[Rhodes22-list] Rhodes22-list Digest, Vol 4230, Issue 1
Richard MacArthur
richard at macarthurlawfirm.com
Wed Aug 5 13:00:54 EDT 2020
With regard to the screws pulling out of the tabernacle, that happened to me about four years ago. The mast was at about 45 degrees but instead of the butt shooting across the foredeck and the mast falling, the butt hit the crane mounting and stopped. My attempts to fill the holes with short lengths of fiberglass and epoxy the new screws in didn't work. That did not hold the mast but pulled out. I decided to give the tabernacle extra help. I put the screws back I as before but this time I rigged two cables from the tabernacle bolt to the cleats on each side of the companionway, put protective covering where the cables contacted the deck, and tightened the cables with hardware bought turnbuckles. Now the tabernacle can't move and we crank the mast up and down with confidence.
-----Original Message-----
From: Rhodes22-list <rhodes22-list-bounces at rhodes22.org> On Behalf Of rhodes22-list-request at rhodes22.org
Sent: Monday, August 3, 2020 9:45 AM
To: rhodes22-list at rhodes22.org
Subject: Rhodes22-list Digest, Vol 4230, Issue 1
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Today's Topics:
1. Re: mainsail problems (gramille)
2. Re: mainsail problems (gramille)
3. Re: Repair of Spider Cracks at Mast Step Tabernacle
(Frederick Lange)
4. Re: mainsail problems (stan)
5. Re: mainsail problems (gramille)
6. Re: mainsail problems (Mark West)
7. Re: mainsail problems (Peter Nyberg)
8. Re: mainsail problems (cjlowe at sssnet.com)
9. Re: mainsail problems (gramille)
10. Reconnecting the Tabernacle Screws Following Sacrificial
Failure (Chris on LBI)
11. Re: Reconnecting the Tabernacle Screws Following Sacrificial
Failure (Mike Riter)
12. Re: Reconnecting the Tabernacle Screws Following Sacrificial
Failure (Peter Nyberg)
13. Re: Reconnecting the Tabernacle Screws Following Sacrificial
Failure (Michael D. Weisner)
14. Rudder Bolt Hole Enlarged (Gmorganflier)
15. Re: Reconnecting the Tabernacle Screws Following Sacrificial
Failure (Graham Stewart)
16. Re: Rudder Bolt Hole Enlarged (Graham Stewart)
17. Re: Reconnecting the Tabernacle Screws Following Sacrificial
Failure (Chris on LBI)
18. Re: Reconnecting the Tabernacle Screws Following Sacrificial
Failure (ROGER PIHLAJA)
19. Re: Rudder Bolt Hole Enlarged (ROGER PIHLAJA)
20. Re: Rudder Bolt Hole Enlarged (Gmorganflier)
21. Re: mainsail problems (Lowe, Rob)
----------------------------------------------------------------------
Message: 1
Date: Thu, 30 Jul 2020 08:35:34 -0700 (MST)
From: gramille <gramille at tds.net>
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <1596123334638-0.post at n5.nabble.com>
Content-Type: text/plain; charset=us-ascii
Thanks May Lou,
Le's hope it is that simple!
Graham
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 2
Date: Thu, 30 Jul 2020 08:51:03 -0700 (MST)
From: gramille <gramille at tds.net>
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <1596124263780-0.post at n5.nabble.com>
Content-Type: text/plain; charset=us-ascii
Thanks Chris, you make a strong case for replacement!
Graham
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 3
Date: Thu, 30 Jul 2020 12:00:46 -0400
From: Frederick Lange <sloopblueheron at gmail.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Repair of Spider Cracks at Mast Step
Tabernacle
Message-ID:
<CABkv36an9QDUhtY4a4mnp7kDEhAT--qJQgxzZ856+n7zz_XYuA at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Yes, I had to have the whole wood mast step plate replaced along with most
of the fiberglass.
Regards,
Rick Lange
On Thu, Jul 30, 2020 at 10:52 AM Chris on LBI <cknell at vt.edu> wrote:
> Has anyone actually experienced the epoxy plugs pulling out as a result of
> a
> subsequent mast mishap? If so, did the plugs damage the fiberglass
> surrounding the screw holes? If they did not damage the surrounding
> fiberglass, I have to wonder why not.
>
>
>
> -----
> Long Beach Island
> --
> Sent from: http://rhodes-22.1065344.n5.nabble.com/
>
------------------------------
Message: 4
Date: Thu, 30 Jul 2020 12:14:40 -0400
From: stan <stan at generalboats.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <77ffb524-95b1-04a6-b4dc-e25ca5b731ba at generalboats.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Graham P.,? For us both to be fair to all those who have, it is time to
join the Coop.
PS:? I see this is going to the List so I will add that for? anyone
liking anything historical about the Rhodes, I am doing a piece on Inner
mast furling that goes back to the Phil Rhodes years; it has a chuckle
or two but its interesting part, at least for me, is discovering this
industry's business plans mentality re this innovation.
Apropos of the current thread on IMF, the problem is in the name, not
the product.? We will cover that as well. My problem is time to get to
all this.? The new ROC site for parts is doing well but I am having
trouble remembering where I keep all those parts.?? Still looking for
partnering but think I will shift the emphasis to Female partnering.?
The deal gets squashed with male wannabes when they figure in the cost
of the divorce.
stan
> On Jul 27, 2020, at 11:30 PM, gramille <gramille at tds.net> wrote:
>> Hi Stan,
>> It is a 2011 model that you refurbished for Scott Johnson of Knoxville
>> ,Tennessee in 2015. I bought it from him last year and the mainsail worked
>> okay although it did occasionally stick towards the top of the mast.
>> This has gradually worsened despite my best attempts to furl it carefully.
>> It is definitely more awkward on the upper setting. Lastly, there was very
>> little wind on my last sail on Saturday when it again jammed and ripped as I
>> was pulling it out! I did not have any real problems last year but it has
>> gradually become more fussy this season!
>>
>>
>>
------------------------------
Message: 5
Date: Fri, 31 Jul 2020 13:12:31 -0700 (MST)
From: gramille <gramille at tds.net>
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <1596226351689-0.post at n5.nabble.com>
Content-Type: text/plain; charset=us-ascii
The mast is coming down soon and I will report back with what is discovered!
I did wonder if I may have overtightened the rear stay causing or making
worse the problem?
That would perhaps explain the worsening of the problem this season!
G
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 6
Date: Fri, 31 Jul 2020 21:28:46 +0000 (UTC)
From: Mark West <keywestseccorp at verizon.net>
To: "rhodes22-list at rhodes22.org" <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <247043968.7192172.1596230926478 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8
straight mast is best, last year working with Charles on show boats we found one of the end bushing screw backed out and was hanging up inside sail area of mast, note rotation of line and sail and # of wraps around shaft the line makes? ?Mark
-----Original Message-----
From: gramille <gramille at tds.net>
To: rhodes22-list at rhodes22.org
Sent: Fri, Jul 31, 2020 4:12 pm
Subject: Re: [Rhodes22-list] mainsail problems
The mast is coming down soon and I will report back with what is discovered!
I did wonder if I may have overtightened the rear stay causing or making
worse the problem?
That would perhaps explain the worsening of the problem this season!
G
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 7
Date: Fri, 31 Jul 2020 21:01:51 -0400
From: Peter Nyberg <peter at sunnybeeches.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <6E25F479-C21C-43C7-BBFB-6C91B21EDD30 at sunnybeeches.com>
Content-Type: text/plain; charset=utf-8
I seriously doubt that you could have tightened the rear stay enough to cause this problem.
?Peter
> On Jul 31, 2020, at 4:12 PM, gramille <gramille at tds.net> wrote:
>
> The mast is coming down soon and I will report back with what is discovered!
> I did wonder if I may have overtightened the rear stay causing or making
> worse the problem?
> That would perhaps explain the worsening of the problem this season!
> G
>
>
>
> --
> Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 8
Date: Fri, 31 Jul 2020 23:43:12 -0400 (EDT)
From: cjlowe at sssnet.com
To: "The Rhodes 22 Email List" <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID:
<61972.24.140.30.102.1596253392.squirrel at quickpop.sssnet.com>
Content-Type: text/plain;charset=iso-8859-1
Well, since this came up, I'd noticed that since I loosened my back stay ,
I've had trouble furling my main sail. Its bunching up at the bottom. I
will try tightening it back up and see wh
> I seriously doubt that you could have tightened the rear stay enough to
> cause this problem.
>
> ???Peter
>
>> On Jul 31, 2020, at 4:12 PM, gramille <gramille at tds.net> wrote:
>>
>> The mast is coming down soon and I will report back with what is
>> discovered!
>> I did wonder if I may have overtightened the rear stay causing or making
>> worse the problem?
>> That would perhaps explain the worsening of the problem this season!
>> G
>>
>>
>>
>> --
>> Sent from: http://rhodes-22.1065344.n5.nabble.com/
>
>
------------------------------
Message: 9
Date: Sat, 1 Aug 2020 07:43:21 -0700 (MST)
From: gramille <gramille at tds.net>
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID: <1596293001702-0.post at n5.nabble.com>
Content-Type: text/plain; charset=us-ascii
Interesting - any other opinions?
G
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 10
Date: Sun, 2 Aug 2020 16:39:30 -0700 (MST)
From: Chris on LBI <cknell at vt.edu>
To: rhodes22-list at rhodes22.org
Subject: [Rhodes22-list] Reconnecting the Tabernacle Screws Following
Sacrificial Failure
Message-ID: <1596411570037-0.post at n5.nabble.com>
Content-Type: text/plain; charset=UTF-8
This topic is a continuation of a different topic titled ?"Repair of Spider
Cracks at Mast Step Tabernacle?. The subject matter of that topic quickly
strayed from gelcoat repair to how to replace the tabernacle screws after
they pull loose. I thought it would be good to highlight this subject matter
with a new topic heading. I thank Graham Stewart, Rodger Pihlaja, Mike
Riter, and Rick Lange all of whom weighed in on the original thread.
Last week while lowering the mast, the three screws holding the tabernacle
to the block above the cabin let loose when the mast was at an angle of
about 45 degrees. A shroud had fouled and the resulting (unintended) forces
pulled the screws out. In reading on this list/forum, I was relieved to
learn that these screw connections were designed to fail to avoid more
expensive damage to the plate and the cabin top. It also seems that the
repair is very easy to accomplish. However, in asking advice regarding the
repair and in doing some research, I'm undecided as to how the repair should
be performed since I have conflicting information. I've started this new
thread to focus specifically on reconnecting these three screws to the block
below the tabernacle plate so that the sacrificial nature of the junction is
preserved.
The three screws on my boat are 3/16? stainless steel, 1? long, with 10
threads per inch. The mounting block below the tabernacle appears to be wood
covered with fiberglass and gelcoat. The combination fiberglass and gelcoat
appear to be about 1/4? thick. The stainless steel base of the tabernacle is
1/8? thick. The holes in the fiberglass are larger than the major diameter
of the screws. Based on this information I estimate that about 5/8? of the
screws were threaded into the wood block. I read somewhere on this
list/forum that the block is typically pine. Using an online tool
(https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html
) that calculates pullout force, I estimate that each of the three screws
would pull out at about 70 pounds of upward force; 210 pounds total.
I had planned to make the repair by filling the holes with epoxy and then
drilling holes in the epoxy to receive the screws. Since there was some soft
wood around the perimeter of the holes, I scraped it out as best I could,
and noted that the new epoxy ?plug? would be larger in diameter than the
holes in the fiberglass. That is, some of the epoxy plug would be
underneath of the fiberglass. This led me to wonder at what force the plug
would release from the surrounding wood because if it did release, it would
transfer the load to the fiberglass above the plug. Apparently the way to
estimate this force is to take the vertical surface area of the wood/epoxy
plug and multiply it by the shear factor of a wood/epoxy joint (obviously an
estimate). A few sources online use 800 psi as this shear factor. So using a
5/8? deep hole with a diameter of 5/16?, I get a pullout force of about 500
pounds per plug; 1500 pounds total.
I assume that the pullout force of a screw from an epoxy plug is greater
than 500 pounds but I can't find a way to estimate this. Although, if it
were a steel pin (without threads), the shear factor would be estimated at
1600 psi. So with the threads the shear factor would be much great than this
and thus the screw withdrawal force would be much greater than the plug
withdrawal force. That is, the plug will pull out well before the screw
pulls out of the plug. Unless of course it is a shorter screw. But without a
way to calculate it, I would not know what length screw to use to achieve
the desired pullout force.
While a few days ago I was all set to start mixing up a batch of epoxy, now
I'm not so sure. Using these calculations based on the assumptions
indicated, the planned approach would change the original design in two very
significant ways. First, the total pullout force would increase from 210
pounds to 1500 pounds. Second, with the epoxy repair, in the case of
failure, the load would be transferred to the underside of the fiberglass
which I assume the original design is intended to protect. That is, the
original design sacrifices the wood/screw connection, the screws pull out,
and the fiberglass is left unharmed.
So now I am left contemplating four different options: Wood Slivers, Bigger
Holes, New Holes, Shorter Screws
Wood Slivers
The idea would be to partially fill the holes with epoxy, and then pack the
holes with wood slivers that would intentionally weaken the epoxy with the
hope that the epoxy/screw junction fails before the wood/epoxy junction of
the plug. That is, the screws would pull out without damage to the
fiberglass. Obviously this pullout force can't really be calculated, but it
seems like it should be less than the wood/epoxy junction of the plug, but
there is some risk that the plug could pull out first and transfer the load
to the fiberglass. One very important unknown to this approach is the
quality of the wood/epoxy junction. If the wood surrounding the epoxy is
weak, the plug may pull out of the hole before the screw pulls out of the
plug. This would transfer the load to the fiberglass. So there are risks to
this approach. Filling the hole with epoxy and encapsulating the slivers in
epoxy should prevent water infiltration.
Bigger Holes
This idea is to drill larger holes in the fiberglass, so that if the epoxy
plug were to pull out, it can without damaging the fiberglass. The holes
would have to be sealed to prevent water infiltration, perhaps with gelcoat.
The force to pull the plugs out is likely much greater than the original
pullout force (1500 lbs vs. 210 lbs), but maybe this is not a bad thing; if
a minor accident occurs (less than 1500 lbs), everything remains intact and
I still go sailing that day. It would seem that this approach would protect
the fiberglass as intended (although maybe a stainless steel rail gets bent
or broken).
New Holes
The original holes could be filled with epoxy and abandoned. Three new holes
would be drilled in the tabernacle base plate and the block, being sure to
make holes in the fiberglass larger than the major diameter of the screws.
This would closely replicate the original design. Care would have to be
taken to prevent water infiltration. It would be interesting to get
confirmation from Stan that the factory drills holds in the fiberglass that
are larger than the screw diameter.
Shorter Screws
The holes would be filled with epoxy, drilled, and new, shorter screws
threaded into the epoxy plug. The problem with this approach is that I don't
have a way to calculate the pullout force of the screw from the epoxy.
Since I am a novice at repairs of this sort, I again look to the list/forum
for advice. I suspect that in a case like this, group-instinct trumps
calculations.
-----
Long Beach Island
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 11
Date: Sun, 2 Aug 2020 21:20:37 -0400
From: Mike Riter <mike at traildesign.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws
Following Sacrificial Failure
Message-ID:
<CAAY+qo8VoCZtCQ7OpFRdnwq57xAfibgneDxb9DbcAvtm_TD2Zg at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
You have really, really thought this through Chris! Looking through your
list of possible choices, I'm throwing my vote in the new holes category.
Fill the existing holes with epoxy, including the spider web cracks, sand
everything smooth and drill new holes. Assuming a good core, the new holes
would represent the same forces of the original mounting.
Michael Riter
SV Emma B
On Sun, Aug 2, 2020 at 7:39 PM Chris on LBI <cknell at vt.edu> wrote:
> This topic is a continuation of a different topic titled ?"Repair of Spider
> Cracks at Mast Step Tabernacle?. The subject matter of that topic quickly
> strayed from gelcoat repair to how to replace the tabernacle screws after
> they pull loose. I thought it would be good to highlight this subject
> matter
> with a new topic heading. I thank Graham Stewart, Rodger Pihlaja, Mike
> Riter, and Rick Lange all of whom weighed in on the original thread.
>
> Last week while lowering the mast, the three screws holding the tabernacle
> to the block above the cabin let loose when the mast was at an angle of
> about 45 degrees. A shroud had fouled and the resulting (unintended) forces
> pulled the screws out. In reading on this list/forum, I was relieved to
> learn that these screw connections were designed to fail to avoid more
> expensive damage to the plate and the cabin top. It also seems that the
> repair is very easy to accomplish. However, in asking advice regarding the
> repair and in doing some research, I'm undecided as to how the repair
> should
> be performed since I have conflicting information. I've started this new
> thread to focus specifically on reconnecting these three screws to the
> block
> below the tabernacle plate so that the sacrificial nature of the junction
> is
> preserved.
>
> The three screws on my boat are 3/16? stainless steel, 1? long, with 10
> threads per inch. The mounting block below the tabernacle appears to be
> wood
> covered with fiberglass and gelcoat. The combination fiberglass and gelcoat
> appear to be about 1/4? thick. The stainless steel base of the tabernacle
> is
> 1/8? thick. The holes in the fiberglass are larger than the major diameter
> of the screws. Based on this information I estimate that about 5/8? of the
> screws were threaded into the wood block. I read somewhere on this
> list/forum that the block is typically pine. Using an online tool
>
> (
> https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html
> ) that calculates pullout force, I estimate that each of the three screws
> would pull out at about 70 pounds of upward force; 210 pounds total.
>
> I had planned to make the repair by filling the holes with epoxy and then
> drilling holes in the epoxy to receive the screws. Since there was some
> soft
> wood around the perimeter of the holes, I scraped it out as best I could,
> and noted that the new epoxy ?plug? would be larger in diameter than the
> holes in the fiberglass. That is, some of the epoxy plug would be
> underneath of the fiberglass. This led me to wonder at what force the plug
> would release from the surrounding wood because if it did release, it would
> transfer the load to the fiberglass above the plug. Apparently the way to
> estimate this force is to take the vertical surface area of the wood/epoxy
> plug and multiply it by the shear factor of a wood/epoxy joint (obviously
> an
> estimate). A few sources online use 800 psi as this shear factor. So using
> a
> 5/8? deep hole with a diameter of 5/16?, I get a pullout force of about 500
> pounds per plug; 1500 pounds total.
>
> I assume that the pullout force of a screw from an epoxy plug is greater
> than 500 pounds but I can't find a way to estimate this. Although, if it
> were a steel pin (without threads), the shear factor would be estimated at
> 1600 psi. So with the threads the shear factor would be much great than
> this
> and thus the screw withdrawal force would be much greater than the plug
> withdrawal force. That is, the plug will pull out well before the screw
> pulls out of the plug. Unless of course it is a shorter screw. But without
> a
> way to calculate it, I would not know what length screw to use to achieve
> the desired pullout force.
>
> While a few days ago I was all set to start mixing up a batch of epoxy, now
> I'm not so sure. Using these calculations based on the assumptions
> indicated, the planned approach would change the original design in two
> very
> significant ways. First, the total pullout force would increase from 210
> pounds to 1500 pounds. Second, with the epoxy repair, in the case of
> failure, the load would be transferred to the underside of the fiberglass
> which I assume the original design is intended to protect. That is, the
> original design sacrifices the wood/screw connection, the screws pull out,
> and the fiberglass is left unharmed.
>
> So now I am left contemplating four different options: Wood Slivers, Bigger
> Holes, New Holes, Shorter Screws
>
> Wood Slivers
> The idea would be to partially fill the holes with epoxy, and then pack the
> holes with wood slivers that would intentionally weaken the epoxy with the
> hope that the epoxy/screw junction fails before the wood/epoxy junction of
> the plug. That is, the screws would pull out without damage to the
> fiberglass. Obviously this pullout force can't really be calculated, but it
> seems like it should be less than the wood/epoxy junction of the plug, but
> there is some risk that the plug could pull out first and transfer the load
> to the fiberglass. One very important unknown to this approach is the
> quality of the wood/epoxy junction. If the wood surrounding the epoxy is
> weak, the plug may pull out of the hole before the screw pulls out of the
> plug. This would transfer the load to the fiberglass. So there are risks to
> this approach. Filling the hole with epoxy and encapsulating the slivers in
> epoxy should prevent water infiltration.
>
> Bigger Holes
> This idea is to drill larger holes in the fiberglass, so that if the epoxy
> plug were to pull out, it can without damaging the fiberglass. The holes
> would have to be sealed to prevent water infiltration, perhaps with
> gelcoat.
> The force to pull the plugs out is likely much greater than the original
> pullout force (1500 lbs vs. 210 lbs), but maybe this is not a bad thing; if
> a minor accident occurs (less than 1500 lbs), everything remains intact and
> I still go sailing that day. It would seem that this approach would protect
> the fiberglass as intended (although maybe a stainless steel rail gets bent
> or broken).
>
> New Holes
> The original holes could be filled with epoxy and abandoned. Three new
> holes
> would be drilled in the tabernacle base plate and the block, being sure to
> make holes in the fiberglass larger than the major diameter of the screws.
> This would closely replicate the original design. Care would have to be
> taken to prevent water infiltration. It would be interesting to get
> confirmation from Stan that the factory drills holds in the fiberglass that
> are larger than the screw diameter.
>
> Shorter Screws
> The holes would be filled with epoxy, drilled, and new, shorter screws
> threaded into the epoxy plug. The problem with this approach is that I
> don't
> have a way to calculate the pullout force of the screw from the epoxy.
>
> Since I am a novice at repairs of this sort, I again look to the list/forum
> for advice. I suspect that in a case like this, group-instinct trumps
> calculations.
>
>
>
> -----
> Long Beach Island
> --
> Sent from: http://rhodes-22.1065344.n5.nabble.com/
>
------------------------------
Message: 12
Date: Sun, 2 Aug 2020 21:33:29 -0400
From: Peter Nyberg <peter at sunnybeeches.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws
Following Sacrificial Failure
Message-ID: <80E5FDB0-B569-4C8A-831C-4A515A2BFDCD at sunnybeeches.com>
Content-Type: text/plain; charset=utf-8
In my opinion, the most import thing is to prevent water intrusion, everything else is pretty easy to repair. You seem to believe that damage to the fiberglass skin would be difficult to deal with, but I don?t believe that?s the case. Given the options you outline, I?d go with the ?bigger holes? approach.
Peter Nyberg
Coventry, CT
s/v Silverheels (1988/2016)
> On Aug 2, 2020, at 7:39 PM, Chris on LBI <cknell at vt.edu> wrote:
>
> This topic is a continuation of a different topic titled ?"Repair of Spider
> Cracks at Mast Step Tabernacle?. The subject matter of that topic quickly
> strayed from gelcoat repair to how to replace the tabernacle screws after
> they pull loose. I thought it would be good to highlight this subject matter
> with a new topic heading. I thank Graham Stewart, Rodger Pihlaja, Mike
> Riter, and Rick Lange all of whom weighed in on the original thread.
>
> Last week while lowering the mast, the three screws holding the tabernacle
> to the block above the cabin let loose when the mast was at an angle of
> about 45 degrees. A shroud had fouled and the resulting (unintended) forces
> pulled the screws out. In reading on this list/forum, I was relieved to
> learn that these screw connections were designed to fail to avoid more
> expensive damage to the plate and the cabin top. It also seems that the
> repair is very easy to accomplish. However, in asking advice regarding the
> repair and in doing some research, I'm undecided as to how the repair should
> be performed since I have conflicting information. I've started this new
> thread to focus specifically on reconnecting these three screws to the block
> below the tabernacle plate so that the sacrificial nature of the junction is
> preserved.
>
> The three screws on my boat are 3/16? stainless steel, 1? long, with 10
> threads per inch. The mounting block below the tabernacle appears to be wood
> covered with fiberglass and gelcoat. The combination fiberglass and gelcoat
> appear to be about 1/4? thick. The stainless steel base of the tabernacle is
> 1/8? thick. The holes in the fiberglass are larger than the major diameter
> of the screws. Based on this information I estimate that about 5/8? of the
> screws were threaded into the wood block. I read somewhere on this
> list/forum that the block is typically pine. Using an online tool
>
> (https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html
> ) that calculates pullout force, I estimate that each of the three screws
> would pull out at about 70 pounds of upward force; 210 pounds total.
>
> I had planned to make the repair by filling the holes with epoxy and then
> drilling holes in the epoxy to receive the screws. Since there was some soft
> wood around the perimeter of the holes, I scraped it out as best I could,
> and noted that the new epoxy ?plug? would be larger in diameter than the
> holes in the fiberglass. That is, some of the epoxy plug would be
> underneath of the fiberglass. This led me to wonder at what force the plug
> would release from the surrounding wood because if it did release, it would
> transfer the load to the fiberglass above the plug. Apparently the way to
> estimate this force is to take the vertical surface area of the wood/epoxy
> plug and multiply it by the shear factor of a wood/epoxy joint (obviously an
> estimate). A few sources online use 800 psi as this shear factor. So using a
> 5/8? deep hole with a diameter of 5/16?, I get a pullout force of about 500
> pounds per plug; 1500 pounds total.
>
> I assume that the pullout force of a screw from an epoxy plug is greater
> than 500 pounds but I can't find a way to estimate this. Although, if it
> were a steel pin (without threads), the shear factor would be estimated at
> 1600 psi. So with the threads the shear factor would be much great than this
> and thus the screw withdrawal force would be much greater than the plug
> withdrawal force. That is, the plug will pull out well before the screw
> pulls out of the plug. Unless of course it is a shorter screw. But without a
> way to calculate it, I would not know what length screw to use to achieve
> the desired pullout force.
>
> While a few days ago I was all set to start mixing up a batch of epoxy, now
> I'm not so sure. Using these calculations based on the assumptions
> indicated, the planned approach would change the original design in two very
> significant ways. First, the total pullout force would increase from 210
> pounds to 1500 pounds. Second, with the epoxy repair, in the case of
> failure, the load would be transferred to the underside of the fiberglass
> which I assume the original design is intended to protect. That is, the
> original design sacrifices the wood/screw connection, the screws pull out,
> and the fiberglass is left unharmed.
>
> So now I am left contemplating four different options: Wood Slivers, Bigger
> Holes, New Holes, Shorter Screws
>
> Wood Slivers
> The idea would be to partially fill the holes with epoxy, and then pack the
> holes with wood slivers that would intentionally weaken the epoxy with the
> hope that the epoxy/screw junction fails before the wood/epoxy junction of
> the plug. That is, the screws would pull out without damage to the
> fiberglass. Obviously this pullout force can't really be calculated, but it
> seems like it should be less than the wood/epoxy junction of the plug, but
> there is some risk that the plug could pull out first and transfer the load
> to the fiberglass. One very important unknown to this approach is the
> quality of the wood/epoxy junction. If the wood surrounding the epoxy is
> weak, the plug may pull out of the hole before the screw pulls out of the
> plug. This would transfer the load to the fiberglass. So there are risks to
> this approach. Filling the hole with epoxy and encapsulating the slivers in
> epoxy should prevent water infiltration.
>
> Bigger Holes
> This idea is to drill larger holes in the fiberglass, so that if the epoxy
> plug were to pull out, it can without damaging the fiberglass. The holes
> would have to be sealed to prevent water infiltration, perhaps with gelcoat.
> The force to pull the plugs out is likely much greater than the original
> pullout force (1500 lbs vs. 210 lbs), but maybe this is not a bad thing; if
> a minor accident occurs (less than 1500 lbs), everything remains intact and
> I still go sailing that day. It would seem that this approach would protect
> the fiberglass as intended (although maybe a stainless steel rail gets bent
> or broken).
>
> New Holes
> The original holes could be filled with epoxy and abandoned. Three new holes
> would be drilled in the tabernacle base plate and the block, being sure to
> make holes in the fiberglass larger than the major diameter of the screws.
> This would closely replicate the original design. Care would have to be
> taken to prevent water infiltration. It would be interesting to get
> confirmation from Stan that the factory drills holds in the fiberglass that
> are larger than the screw diameter.
>
> Shorter Screws
> The holes would be filled with epoxy, drilled, and new, shorter screws
> threaded into the epoxy plug. The problem with this approach is that I don't
> have a way to calculate the pullout force of the screw from the epoxy.
>
> Since I am a novice at repairs of this sort, I again look to the list/forum
> for advice. I suspect that in a case like this, group-instinct trumps
> calculations.
>
>
>
> -----
> Long Beach Island
> --
> Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 13
Date: Sun, 02 Aug 2020 21:52:22 -0400
From: "Michael D. Weisner" <mweisner at ebsmed.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws
Following Sacrificial Failure
Message-ID: <mailman.1080.1596419550.2787.rhodes22-list at rhodes22.org>
Content-Type: text/plain; charset=utf-8
Chris,I understand your issue of pulling out the entire epoxy plug and damaging the fiberglass over the epoxy that has flowed outside of the original hole where you removed damaged wood.Can you make a wood plug that is the diameter of the hole, made of the same wood used in the tabernacle structure, preserving the correct grain? If you can, why not set this wood plug into the epoxy and set the screw into the wood plug? You will have replicated the original structure and release properties for the screw. You shouldn't need to worry about the epoxy pulling out if the screw releases first.? ?Mike? ?s/v Wind Lass ('91)? ?Nissequogue, NY
-------- Original message --------From: Chris on LBI <cknell at vt.edu> Date: 8/2/20 7:39 PM (GMT-05:00) To: rhodes22-list at rhodes22.org Subject: [Rhodes22-list] Reconnecting the Tabernacle Screws Following
Sacrificial Failure This topic is a continuation of a different topic titled ?"Repair of SpiderCracks at Mast Step Tabernacle?. The subject matter of that topic quicklystrayed from gelcoat repair to how to replace the tabernacle screws afterthey pull loose. I thought it would be good to highlight this subject matterwith a new topic heading. I thank Graham Stewart, Rodger Pihlaja, MikeRiter, and Rick Lange all of whom weighed in on the original thread.Last week while lowering the mast, the three screws holding the tabernacleto the block above the cabin let loose when the mast was at an angle ofabout 45 degrees. A shroud had fouled and the resulting (unintended) forcespulled the screws out. In reading on this list/forum, I was relieved tolearn that these screw connections were designed to fail to avoid moreexpensive damage to the plate and the cabin top. It also seems that therepair is very easy to accomplish. However, in asking advice regarding therepair and in doing some re
search, I'm undecided as to how the repair shouldbe performed since I have conflicting information. I've started this newthread to focus specifically on reconnecting these three screws to the blockbelow the tabernacle plate so that the sacrificial nature of the junction ispreserved.The three screws on my boat are 3/16? stainless steel, 1? long, with 10threads per inch. The mounting block below the tabernacle appears to be woodcovered with fiberglass and gelcoat. The combination fiberglass and gelcoatappear to be about 1/4? thick. The stainless steel base of the tabernacle is1/8? thick. The holes in the fiberglass are larger than the major diameterof the screws.? Based on this information I estimate that about 5/8? of thescrews were threaded into the wood block. I read somewhere on thislist/forum that the block is typically pine. Using an online tool (https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html) that calculates pullout force, I estimat
e that each of the three screwswould pull out at about 70 pounds of upward force; 210 pounds total.I had planned to make the repair by filling the holes with epoxy and thendrilling holes in the epoxy to receive the screws. Since there was some softwood around the perimeter of the holes, I scraped it out as best I could,and noted that the new epoxy ?plug? would be larger in diameter than theholes in the fiberglass.? That is, some of the epoxy plug would beunderneath of the fiberglass. This led me to wonder at what force the plugwould release from the surrounding wood because if it did release, it wouldtransfer the load to the fiberglass above the plug. Apparently the way toestimate this force is to take the vertical surface area of the wood/epoxyplug and multiply it by the shear factor of a wood/epoxy joint (obviously anestimate). A few sources online use 800 psi as this shear factor. So using a5/8? deep hole with a diameter of 5/16?, I get a pullout force of about 500pounds
per plug; 1500 pounds total. I assume that the pullout force of a screw from an epoxy plug is greaterthan 500 pounds but I can't find a way to estimate this. Although, if itwere a steel pin (without threads), the shear factor would be estimated at1600 psi. So with the threads the shear factor would be much great than thisand thus the screw withdrawal force would be much greater than the plugwithdrawal force. That is, the plug will pull out well before the screwpulls out of the plug. Unless of course it is a shorter screw. But without away to calculate it, I would not know what length screw to use to achievethe desired pullout force.While a few days ago I was all set to start mixing up a batch of epoxy, nowI'm not so sure. Using these calculations based on the assumptionsindicated, the planned approach would change the original design in two verysignificant ways. First, the total pullout force would increase from 210pounds to 1500 pounds. Second, with the epoxy repair, in the
case offailure, the load would be transferred to the underside of the fiberglasswhich I assume the original design is intended to protect. That is, theoriginal design sacrifices the wood/screw connection, the screws pull out,and the fiberglass is left unharmed.So now I am left contemplating four different options: Wood Slivers, BiggerHoles, New Holes, Shorter ScrewsWood SliversThe idea would be to partially fill the holes with epoxy, and then pack theholes with wood slivers that would intentionally weaken the epoxy with thehope that the epoxy/screw junction fails before the wood/epoxy junction ofthe plug. That is, the screws would pull out without damage to thefiberglass. Obviously this pullout force can't really be calculated, but itseems like it should be less than the wood/epoxy junction of the plug, butthere is some risk that the plug could pull out first and transfer the loadto the fiberglass.? One very important unknown to this approach is thequality of the wood/epoxy
junction. If the wood surrounding the epoxy isweak, the plug may pull out of the hole before the screw pulls out of theplug. This would transfer the load to the fiberglass. So there are risks tothis approach. Filling the hole with epoxy and encapsulating the slivers inepoxy should prevent water infiltration.Bigger HolesThis idea is to drill larger holes in the fiberglass, so that if the epoxyplug were to pull out, it can without damaging the fiberglass. The holeswould have to be sealed to prevent water infiltration, perhaps with gelcoat.The force to pull the plugs out is likely much greater than the originalpullout force (1500 lbs vs. 210 lbs), but maybe this is not a bad thing; ifa minor accident occurs (less than 1500 lbs), everything remains intact andI still go sailing that day. It would seem that this approach would protectthe fiberglass as intended (although maybe a stainless steel rail gets bentor broken).New HolesThe original holes could be filled with epoxy and aba
ndoned. Three new holeswould be drilled in the tabernacle base plate and the block, being sure tomake holes in the fiberglass larger than the major diameter of the screws.This would closely replicate the original design. Care would have to betaken to prevent water infiltration. It would be interesting to getconfirmation from Stan that the factory drills holds in the fiberglass thatare larger than the screw diameter.Shorter ScrewsThe holes would be filled with epoxy, drilled, and new, shorter screwsthreaded into the epoxy plug. The problem with this approach is that I don'thave a way to calculate the pullout force of the screw from the epoxy. Since I am a novice at repairs of this sort, I again look to the list/forumfor advice. I suspect that in a case like this, group-instinct trumpscalculations.-----Long Beach Island--Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 14
Date: Sun, 2 Aug 2020 18:55:30 -0700 (MST)
From: Gmorganflier <gmorgan.flier at gmail.com>
To: rhodes22-list at rhodes22.org
Subject: [Rhodes22-list] Rudder Bolt Hole Enlarged
Message-ID: <1596419730473-0.post at n5.nabble.com>
Content-Type: text/plain; charset=UTF-8
I took my rudder and rudder cheeks off today in preparation to paint them.
The hole in the rudder where the pivot bolt goes through is quite
enlarged....probably twice the diameter of the bolt. I noticed the plywood
core where the hole goes through was wet. I feared maybe my entire rudder
was waterlogged, but after turning the rudder upside down and leaving it in
the sun, the hole appears to be drying up. There are no cracks or damaged
areas which would allow water intrusion. The bolt hole seems to be the only
way water is getting in and we did have rain yesterday.
My question to those who are so much more experienced than me in boating
repairs....what should I do to stop water from getting in the rudder through
this bolt hole. Maybe enlarge the hole even more and epoxy some sort of
bushing for the bolt to go through? I?m open for suggestions.
Thanks,
George Morgan
1986 R22 S/V Knotty Lady
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 15
Date: Sun, 2 Aug 2020 22:06:49 -0400
From: "Graham Stewart" <gstewart8 at cogeco.ca>
To: "'The Rhodes 22 Email List'" <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws
Following Sacrificial Failure
Message-ID: <034901d6693a$c1adf0b0$4509d210$@ca>
Content-Type: text/plain; charset="UTF-8"
Your calculations are impressive but in the end you probably need to go with what you are most comfortable. The discussion has been interesting to me and I now think I would do it differently than I did last time when I drilled out the hole, filled with epoxy and then drilled new holes.
Option 1 to use slivers and epoxy and option 2 to drill larger holes are not mutually exclusive as I understand them and I think that combination is what I would go with. In that case I would want to maximize the proportion of wood slivers to epoxy. The epoxy would be only sufficient to seal the core and hold the slivers together. Not having the fiberglass overhanging the hole would likely reduce the damage to the skin should the plug pull out. The weakest link, I would think, would be the interface between the plug and the core material. Unless the core is damaged and the epoxy seeps into crevices I would think that the force required to pull the plug out would not be much greater than the force required to pull a screw out of solid wood under fiberglass. That is what I think but I could easily be entirely wrong. In this case you want a properly sealed but relatively weak bond. Using the slivers tightly packed strikes me as the best way to achieve this balance.
I don't know how you could abandon the old holes and drill new ones without moving the base. I would not do that. When I rebuilt my deck I removed the mast foot, repaired and then painted the step along with the entire deck. I did not make careful note of exactly where the plate was attached thinking that is was centered on the step. Nope, it has to placed exactly in the right place or you will not be able to attach the slider for the pop top to raise and descend properly. I ended up doing this install three times before I got it right. Each time I had to raise and then lower the mast. After spending 7 years restoring the boat you can imagine how frustrating that was to be stopped at the moment that I would be able to raise the sails and go.
The screws you have are, as I recall, much shorter than mine but if these are what Stan used I would stick with them.
Good luck,
Graham Stewart
gstewart8 at cogeco.ca
-----Original Message-----
From: Rhodes22-list [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Chris on LBI
Sent: Sunday, August 2, 2020 7:40 PM
To: rhodes22-list at rhodes22.org
Subject: [Rhodes22-list] Reconnecting the Tabernacle Screws Following Sacrificial Failure
This topic is a continuation of a different topic titled ?"Repair of Spider
Cracks at Mast Step Tabernacle?. The subject matter of that topic quickly
strayed from gelcoat repair to how to replace the tabernacle screws after
they pull loose. I thought it would be good to highlight this subject matter
with a new topic heading. I thank Graham Stewart, Rodger Pihlaja, Mike
Riter, and Rick Lange all of whom weighed in on the original thread.
Last week while lowering the mast, the three screws holding the tabernacle
to the block above the cabin let loose when the mast was at an angle of
about 45 degrees. A shroud had fouled and the resulting (unintended) forces
pulled the screws out. In reading on this list/forum, I was relieved to
learn that these screw connections were designed to fail to avoid more
expensive damage to the plate and the cabin top. It also seems that the
repair is very easy to accomplish. However, in asking advice regarding the
repair and in doing some research, I'm undecided as to how the repair should
be performed since I have conflicting information. I've started this new
thread to focus specifically on reconnecting these three screws to the block
below the tabernacle plate so that the sacrificial nature of the junction is
preserved.
The three screws on my boat are 3/16? stainless steel, 1? long, with 10
threads per inch. The mounting block below the tabernacle appears to be wood
covered with fiberglass and gelcoat. The combination fiberglass and gelcoat
appear to be about 1/4? thick. The stainless steel base of the tabernacle is
1/8? thick. The holes in the fiberglass are larger than the major diameter
of the screws. Based on this information I estimate that about 5/8? of the
screws were threaded into the wood block. I read somewhere on this
list/forum that the block is typically pine. Using an online tool
(https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html
) that calculates pullout force, I estimate that each of the three screws
would pull out at about 70 pounds of upward force; 210 pounds total.
I had planned to make the repair by filling the holes with epoxy and then
drilling holes in the epoxy to receive the screws. Since there was some soft
wood around the perimeter of the holes, I scraped it out as best I could,
and noted that the new epoxy ?plug? would be larger in diameter than the
holes in the fiberglass. That is, some of the epoxy plug would be
underneath of the fiberglass. This led me to wonder at what force the plug
would release from the surrounding wood because if it did release, it would
transfer the load to the fiberglass above the plug. Apparently the way to
estimate this force is to take the vertical surface area of the wood/epoxy
plug and multiply it by the shear factor of a wood/epoxy joint (obviously an
estimate). A few sources online use 800 psi as this shear factor. So using a
5/8? deep hole with a diameter of 5/16?, I get a pullout force of about 500
pounds per plug; 1500 pounds total.
I assume that the pullout force of a screw from an epoxy plug is greater
than 500 pounds but I can't find a way to estimate this. Although, if it
were a steel pin (without threads), the shear factor would be estimated at
1600 psi. So with the threads the shear factor would be much great than this
and thus the screw withdrawal force would be much greater than the plug
withdrawal force. That is, the plug will pull out well before the screw
pulls out of the plug. Unless of course it is a shorter screw. But without a
way to calculate it, I would not know what length screw to use to achieve
the desired pullout force.
While a few days ago I was all set to start mixing up a batch of epoxy, now
I'm not so sure. Using these calculations based on the assumptions
indicated, the planned approach would change the original design in two very
significant ways. First, the total pullout force would increase from 210
pounds to 1500 pounds. Second, with the epoxy repair, in the case of
failure, the load would be transferred to the underside of the fiberglass
which I assume the original design is intended to protect. That is, the
original design sacrifices the wood/screw connection, the screws pull out,
and the fiberglass is left unharmed.
So now I am left contemplating four different options: Wood Slivers, Bigger
Holes, New Holes, Shorter Screws
Wood Slivers
The idea would be to partially fill the holes with epoxy, and then pack the
holes with wood slivers that would intentionally weaken the epoxy with the
hope that the epoxy/screw junction fails before the wood/epoxy junction of
the plug. That is, the screws would pull out without damage to the
fiberglass. Obviously this pullout force can't really be calculated, but it
seems like it should be less than the wood/epoxy junction of the plug, but
there is some risk that the plug could pull out first and transfer the load
to the fiberglass. One very important unknown to this approach is the
quality of the wood/epoxy junction. If the wood surrounding the epoxy is
weak, the plug may pull out of the hole before the screw pulls out of the
plug. This would transfer the load to the fiberglass. So there are risks to
this approach. Filling the hole with epoxy and encapsulating the slivers in
epoxy should prevent water infiltration.
Bigger Holes
This idea is to drill larger holes in the fiberglass, so that if the epoxy
plug were to pull out, it can without damaging the fiberglass. The holes
would have to be sealed to prevent water infiltration, perhaps with gelcoat.
The force to pull the plugs out is likely much greater than the original
pullout force (1500 lbs vs. 210 lbs), but maybe this is not a bad thing; if
a minor accident occurs (less than 1500 lbs), everything remains intact and
I still go sailing that day. It would seem that this approach would protect
the fiberglass as intended (although maybe a stainless steel rail gets bent
or broken).
New Holes
The original holes could be filled with epoxy and abandoned. Three new holes
would be drilled in the tabernacle base plate and the block, being sure to
make holes in the fiberglass larger than the major diameter of the screws.
This would closely replicate the original design. Care would have to be
taken to prevent water infiltration. It would be interesting to get
confirmation from Stan that the factory drills holds in the fiberglass that
are larger than the screw diameter.
Shorter Screws
The holes would be filled with epoxy, drilled, and new, shorter screws
threaded into the epoxy plug. The problem with this approach is that I don't
have a way to calculate the pullout force of the screw from the epoxy.
Since I am a novice at repairs of this sort, I again look to the list/forum
for advice. I suspect that in a case like this, group-instinct trumps
calculations.
-----
Long Beach Island
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 16
Date: Sun, 2 Aug 2020 22:27:40 -0400
From: "Graham Stewart" <gstewart8 at cogeco.ca>
To: "'The Rhodes 22 Email List'" <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Rudder Bolt Hole Enlarged
Message-ID: <034f01d6693d$ac08fcc0$041af640$@ca>
Content-Type: text/plain; charset="UTF-8"
George:
Might you epoxy in a tube, preferably stainless steel but aluminum might do, that has an opening that is the proper diameter.
Graham Stewart
Agile, Rodes 22, 1976
Kingston Ontario
-----Original Message-----
From: Rhodes22-list [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Gmorganflier
Sent: Sunday, August 2, 2020 9:56 PM
To: rhodes22-list at rhodes22.org
Subject: [Rhodes22-list] Rudder Bolt Hole Enlarged
I took my rudder and rudder cheeks off today in preparation to paint them.
The hole in the rudder where the pivot bolt goes through is quite
enlarged....probably twice the diameter of the bolt. I noticed the plywood
core where the hole goes through was wet. I feared maybe my entire rudder
was waterlogged, but after turning the rudder upside down and leaving it in
the sun, the hole appears to be drying up. There are no cracks or damaged
areas which would allow water intrusion. The bolt hole seems to be the only
way water is getting in and we did have rain yesterday.
My question to those who are so much more experienced than me in boating
repairs....what should I do to stop water from getting in the rudder through
this bolt hole. Maybe enlarge the hole even more and epoxy some sort of
bushing for the bolt to go through? I?m open for suggestions.
Thanks,
George Morgan
1986 R22 S/V Knotty Lady
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 17
Date: Mon, 3 Aug 2020 04:31:55 -0700 (MST)
From: Chris on LBI <cknell at vt.edu>
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws
Following Sacrificial Failure
Message-ID: <1596454315934-0.post at n5.nabble.com>
Content-Type: text/plain; charset=us-ascii
Graham,
In thinking about drilling new holes, I was thinking that I would also drill
new holes in the tabernacle base plate so the location of the base plate
would not move.
But your point about hole location raises an interesting additional problem
for me that I had not considered. Each of the three existing holes in the
mounting block below the base plate is now oblong, sort of like two holes
slightly offset from one another in both the x and y axis. So I'll have to
decide which of the two possible centers is the one I should use when
remounting the tabernacle base plate.
That is an interesting observation that Wood Slivers and Larger Holes are
not mutually exclusive.
I feel your pain relocating the base plate 3 times. When you did so, how did
you repair the holes that were not located correctly? Also, do your screws
bite into the fiberglass as well as the wood block underneath?
Thanks,
Chris
-----
Long Beach Island
--
Sent from: http://rhodes-22.1065344.n5.nabble.com/
------------------------------
Message: 18
Date: Mon, 3 Aug 2020 12:26:29 +0000
From: ROGER PIHLAJA <roger_pihlaja at msn.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws
Following Sacrificial Failure
Message-ID:
<CH2PR02MB6920DFB9A35B6FD95C899A2C804D0 at CH2PR02MB6920.namprd02.prod.outlook.com>
Content-Type: text/plain; charset="Windows-1252"
Chris,
For the most part, your calculations are reasonable and the results are in the right ballpark, with one exception. I must push back on your assumption that the 3 screws are loaded evenly and therefore the total failure load is 3X the individual failure load. When the mast stepping/unstepping goes properly, this assumption might be OK. But, the very notion of something going wrong during the mast stepping/instepping implies these 3 screws are not evenly loaded. I would hypothesize a failure mechanism wherein an uneven load causes first one screw to fail, which overloads another, and then the third to fail in a cascading sequence. A more conservative design approach would call for each screw to be capable of supporting the entire load.
Roger Pihlaja
S/V Dynamic Equilibrium
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
From: Graham Stewart<mailto:gstewart8 at cogeco.ca>
Sent: Sunday, August 2, 2020 10:06 PM
To: 'The Rhodes 22 Email List'<mailto:rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Reconnecting the Tabernacle Screws Following Sacrificial Failure
Your calculations are impressive but in the end you probably need to go with what you are most comfortable. The discussion has been interesting to me and I now think I would do it differently than I did last time when I drilled out the hole, filled with epoxy and then drilled new holes.
Option 1 to use slivers and epoxy and option 2 to drill larger holes are not mutually exclusive as I understand them and I think that combination is what I would go with. In that case I would want to maximize the proportion of wood slivers to epoxy. The epoxy would be only sufficient to seal the core and hold the slivers together. Not having the fiberglass overhanging the hole would likely reduce the damage to the skin should the plug pull out. The weakest link, I would think, would be the interface between the plug and the core material. Unless the core is damaged and the epoxy seeps into crevices I would think that the force required to pull the plug out would not be much greater than the force required to pull a screw out of solid wood under fiberglass. That is what I think but I could easily be entirely wrong. In this case you want a properly sealed but relatively weak bond. Using the slivers tightly packed strikes me as the best way to achieve this balance.
I don't know how you could abandon the old holes and drill new ones without moving the base. I would not do that. When I rebuilt my deck I removed the mast foot, repaired and then painted the step along with the entire deck. I did not make careful note of exactly where the plate was attached thinking that is was centered on the step. Nope, it has to placed exactly in the right place or you will not be able to attach the slider for the pop top to raise and descend properly. I ended up doing this install three times before I got it right. Each time I had to raise and then lower the mast. After spending 7 years restoring the boat you can imagine how frustrating that was to be stopped at the moment that I would be able to raise the sails and go.
The screws you have are, as I recall, much shorter than mine but if these are what Stan used I would stick with them.
Good luck,
Graham Stewart
gstewart8 at cogeco.ca
-----Original Message-----
From: Rhodes22-list [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Chris on LBI
Sent: Sunday, August 2, 2020 7:40 PM
To: rhodes22-list at rhodes22.org
Subject: [Rhodes22-list] Reconnecting the Tabernacle Screws Following Sacrificial Failure
This topic is a continuation of a different topic titled ?"Repair of Spider
Cracks at Mast Step Tabernacle?. The subject matter of that topic quickly
strayed from gelcoat repair to how to replace the tabernacle screws after
they pull loose. I thought it would be good to highlight this subject matter
with a new topic heading. I thank Graham Stewart, Rodger Pihlaja, Mike
Riter, and Rick Lange all of whom weighed in on the original thread.
Last week while lowering the mast, the three screws holding the tabernacle
to the block above the cabin let loose when the mast was at an angle of
about 45 degrees. A shroud had fouled and the resulting (unintended) forces
pulled the screws out. In reading on this list/forum, I was relieved to
learn that these screw connections were designed to fail to avoid more
expensive damage to the plate and the cabin top. It also seems that the
repair is very easy to accomplish. However, in asking advice regarding the
repair and in doing some research, I'm undecided as to how the repair should
be performed since I have conflicting information. I've started this new
thread to focus specifically on reconnecting these three screws to the block
below the tabernacle plate so that the sacrificial nature of the junction is
preserved.
The three screws on my boat are 3/16? stainless steel, 1? long, with 10
threads per inch. The mounting block below the tabernacle appears to be wood
covered with fiberglass and gelcoat. The combination fiberglass and gelcoat
appear to be about 1/4? thick. The stainless steel base of the tabernacle is
1/8? thick. The holes in the fiberglass are larger than the major diameter
of the screws. Based on this information I estimate that about 5/8? of the
screws were threaded into the wood block. I read somewhere on this
list/forum that the block is typically pine. Using an online tool
(https://www.engineeringtoolbox.com/wood-screws-allowable-withdrawal-load-d_1815.html
) that calculates pullout force, I estimate that each of the three screws
would pull out at about 70 pounds of upward force; 210 pounds total.
I had planned to make the repair by filling the holes with epoxy and then
drilling holes in the epoxy to receive the screws. Since there was some soft
wood around the perimeter of the holes, I scraped it out as best I could,
and noted that the new epoxy ?plug? would be larger in diameter than the
holes in the fiberglass. That is, some of the epoxy plug would be
underneath of the fiberglass. This led me to wonder at what force the plug
would release from the surrounding wood because if it did release, it would
transfer the load to the fiberglass above the plug. Apparently the way to
estimate this force is to take the vertical surface area of the wood/epoxy
plug and multiply it by the shear factor of a wood/epoxy joint (obviously an
estimate). A few sources online use 800 psi as this shear factor. So using a
5/8? deep hole with a diameter of 5/16?, I get a pullout force of about 500
pounds per plug; 1500 pounds total.
I assume that the pullout force of a screw from an epoxy plug is greater
than 500 pounds but I can't find a way to estimate this. Although, if it
were a steel pin (without threads), the shear factor would be estimated at
1600 psi. So with the threads the shear factor would be much great than this
and thus the screw withdrawal force would be much greater than the plug
withdrawal force. That is, the plug will pull out well before the screw
pulls out of the plug. Unless of course it is a shorter screw. But without a
way to calculate it, I would not know what length screw to use to achieve
the desired pullout force.
While a few days ago I was all set to start mixing up a batch of epoxy, now
I'm not so sure. Using these calculations based on the assumptions
indicated, the planned approach would change the original design in two very
significant ways. First, the total pullout force would increase from 210
pounds to 1500 pounds. Second, with the epoxy repair, in the case of
failure, the load would be transferred to the underside of the fiberglass
which I assume the original design is intended to protect. That is, the
original design sacrifices the wood/screw connection, the screws pull out,
and the fiberglass is left unharmed.
So now I am left contemplating four different options: Wood Slivers, Bigger
Holes, New Holes, Shorter Screws
Wood Slivers
The idea would be to partially fill the holes with epoxy, and then pack the
holes with wood slivers that would intentionally weaken the epoxy with the
hope that the epoxy/screw junction fails before the wood/epoxy junction of
the plug. That is, the screws would pull out without damage to the
fiberglass. Obviously this pullout force can't really be calculated, but it
seems like it should be less than the wood/epoxy junction of the plug, but
there is some risk that the plug could pull out first and transfer the load
to the fiberglass. One very important unknown to this approach is the
quality of the wood/epoxy junction. If the wood surrounding the epoxy is
weak, the plug may pull out of the hole before the screw pulls out of the
plug. This would transfer the load to the fiberglass. So there are risks to
this approach. Filling the hole with epoxy and encapsulating the slivers in
epoxy should prevent water infiltration.
Bigger Holes
This idea is to drill larger holes in the fiberglass, so that if the epoxy
plug were to pull out, it can without damaging the fiberglass. The holes
would have to be sealed to prevent water infiltration, perhaps with gelcoat.
The force to pull the plugs out is likely much greater than the original
pullout force (1500 lbs vs. 210 lbs), but maybe this is not a bad thing; if
a minor accident occurs (less than 1500 lbs), everything remains intact and
I still go sailing that day. It would seem that this approach would protect
the fiberglass as intended (although maybe a stainless steel rail gets bent
or broken).
New Holes
The original holes could be filled with epoxy and abandoned. Three new holes
would be drilled in the tabernacle base plate and the block, being sure to
make holes in the fiberglass larger than the major diameter of the screws.
This would closely replicate the original design. Care would have to be
taken to prevent water infiltration. It would be interesting to get
confirmation from Stan that the factory drills holds in the fiberglass that
are larger than the screw diameter.
Shorter Screws
The holes would be filled with epoxy, drilled, and new, shorter screws
threaded into the epoxy plug. The problem with this approach is that I don't
have a way to calculate the pullout force of the screw from the epoxy.
Since I am a novice at repairs of this sort, I again look to the list/forum
for advice. I suspect that in a case like this, group-instinct trumps
calculations.
-----
Long Beach Island
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------------------------------
Message: 19
Date: Mon, 3 Aug 2020 12:50:29 +0000
From: ROGER PIHLAJA <roger_pihlaja at msn.com>
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Rudder Bolt Hole Enlarged
Message-ID:
<CH2PR02MB69203CE8DF29D191DC74B67E804D0 at CH2PR02MB6920.namprd02.prod.outlook.com>
Content-Type: text/plain; charset="Windows-1252"
George,
I would drill out the hole to 2X it?s present diameter. Then, coat the ID with unthickened epoxy to seal it. After the unthickened epoxy has kicked off; but, not fully cured, fill the hole with epoxy thickened with WEST System 406 Colloidal Silica and 423 Graphite powder mixed in a 90%wt 406, 10%wt 423 ratio. The thickener mixture should be dry blended first, not mixed separately into the epoxy. The epoxy should be loaded with the thickener such that the mixture flows like thick pancake batter. Mix the epoxy resin and thickener first, then add the thickener mixture, and blend it such that all the powder is wetted out with no lumps or bubbles. After the thickened epoxy is fully cured, drill out a hole for the bolt, and you?re good to go. The 406/423 filler mixture will provide a very hard, abrasion resistant, lubricative bearing surface for the bolt to turn on. But, you won?t have any galling or dissimilar metal corrosion issues with the stainless steel bolt. By wait
ing for the unthickened epoxy to kick off, but not fully cure, when you pour in the thickened epoxy, you will have a molecular and mechanical bond with the rudder substrate that will never fail. This repair will last a very long time.
Roger Pihlaja
S/V Dynamic Equilibrium
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
From: Graham Stewart<mailto:gstewart8 at cogeco.ca>
Sent: Sunday, August 2, 2020 10:27 PM
To: 'The Rhodes 22 Email List'<mailto:rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Rudder Bolt Hole Enlarged
George:
Might you epoxy in a tube, preferably stainless steel but aluminum might do, that has an opening that is the proper diameter.
Graham Stewart
Agile, Rodes 22, 1976
Kingston Ontario
-----Original Message-----
From: Rhodes22-list [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Gmorganflier
Sent: Sunday, August 2, 2020 9:56 PM
To: rhodes22-list at rhodes22.org
Subject: [Rhodes22-list] Rudder Bolt Hole Enlarged
I took my rudder and rudder cheeks off today in preparation to paint them.
The hole in the rudder where the pivot bolt goes through is quite
enlarged....probably twice the diameter of the bolt. I noticed the plywood
core where the hole goes through was wet. I feared maybe my entire rudder
was waterlogged, but after turning the rudder upside down and leaving it in
the sun, the hole appears to be drying up. There are no cracks or damaged
areas which would allow water intrusion. The bolt hole seems to be the only
way water is getting in and we did have rain yesterday.
My question to those who are so much more experienced than me in boating
repairs....what should I do to stop water from getting in the rudder through
this bolt hole. Maybe enlarge the hole even more and epoxy some sort of
bushing for the bolt to go through? I?m open for suggestions.
Thanks,
George Morgan
1986 R22 S/V Knotty Lady
--
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------------------------------
Message: 20
Date: Mon, 3 Aug 2020 06:15:21 -0700 (MST)
From: Gmorganflier <gmorgan.flier at gmail.com>
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] Rudder Bolt Hole Enlarged
Message-ID: <1596460521780-0.post at n5.nabble.com>
Content-Type: text/plain; charset=UTF-8
Roger and Graham,
Thanks for your responses.
Roger....I like your solution...I?ll plan to do as you recommended.
George Morgan
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------------------------------
Message: 21
Date: Mon, 3 Aug 2020 13:45:08 +0000
From: "Lowe, Rob" <rlowe at vt.edu>
To: "rhodes22-list at rhodes22.org" <rhodes22-list at rhodes22.org>, Mark
West <keywestseccorp at verizon.net>
Subject: Re: [Rhodes22-list] mainsail problems
Message-ID:
<MN2PR05MB6941C708D73AB489A04CF659C14D0 at MN2PR05MB6941.namprd05.prod.outlook.com>
Content-Type: text/plain; charset="iso-8859-1"
Yes, make note of the wrap direction and the number of turns that the furling line makes on the drum. I'm glad I took photos of mine when I replaced my main this year. - rob
________________________________
From: Rhodes22-list <rhodes22-list-bounces at rhodes22.org> on behalf of Mark West via Rhodes22-list <rhodes22-list at rhodes22.org>
Sent: Friday, July 31, 2020 5:28 PM
To: rhodes22-list at rhodes22.org <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] mainsail problems
straight mast is best, last year working with Charles on show boats we found one of the end bushing screw backed out and was hanging up inside sail area of mast, note rotation of line and sail and # of wraps around shaft the line makes Mark
-----Original Message-----
From: gramille <gramille at tds.net>
To: rhodes22-list at rhodes22.org
Sent: Fri, Jul 31, 2020 4:12 pm
Subject: Re: [Rhodes22-list] mainsail problems
The mast is coming down soon and I will report back with what is discovered!
I did wonder if I may have overtightened the rear stay causing or making
worse the problem?
That would perhaps explain the worsening of the problem this season!
G
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