[Rhodes22-list] Deck joint repair.
The Rhodes 22 Email List
rhodes22-list at rhodes22.org
Wed Dec 10 07:26:47 EST 2014
Graham,
The newer boats all use a plastic rub rail. Aluminum was scrapped years
ago. NP1 sticks to anything it comes in contact with. It is used in roofing
because it seals during expansion and contraction events. It also has a 15
year direct exposure guarantee from the manufacturer. You are correct in that
you don't want to apply more than you can install the pop rivets and
tighten within an hour or so. It takes several days to fully cure, but becomes
water tight after skinning over. It never fully "hardens".
I did this procedure approximately fifteen years ago on Rumrunner and to
this day it's still water tight.
Rummy
In a message dated 12/9/2014 11:00:25 A.M. Eastern Standard Time,
rhodes22-list at rhodes22.org writes:
As expected, Rummy's instructions are spot on excellent. I might add a few
additional bits that he does not mention and Rummy can correct me if I am
wrong.
On my boat (1976) not all of the rivets came all the way through to the
aluminium rub rail. To remove all of the rivets I had to remove the
aluminium rail and I was unable to do that without destroying it as any
bends that you put into the rail cannot be straightened. So plan on
replacing the rub rail with a new one.
The sealant you decide to use might determine how much you should do at one
time. I am not familiar with the sealant Rummy uses but as it is intended
for roofs, I suspect it stays very soft. Perhaps Rummy will advise what
happens to the sealant he uses as it cures. But if you use a sealant that
hardens up when it cures such as any of the marine sealants you will want
to
close the gap with rivets or bolts before the sealant cures. If you seal
all
the way around the boat and then start adding the rivets the sealant will
cure before you will be able to compress the join.
You will no doubt find that everyone has strong and differing opinions
about
what sealant to use and in the end you will need to go with your best
judgement. Obviously you want a top quality sealant that will last
indefinitely. You will also probably want one that has excellent expansion
capabilities. As the deck and hull expands and shrinks and also flexes, it
is important that the sealant has the ability to tolerate that change. Even
sealant that has excellent elasticity will not work if it is applied too
thin. Boat windows made of Plexiglas and attached to the exterior without
hardware use a combination of special thick double-sided tape and high flex
sealant - usually Dow-Corning 795. The tape is extremely adhesive but also
maintains about a 1/8" gap between the window and the cabin side that
allows
the sealant to be thick enough to work properly. The 795 sealant is
extremely flexible but also extremely adhesive.
The main issue in the case of the hull deck join, in my opinion, is not so
much adhesion, as the rivets will hold the boat together, but rather to
maintain a good permanent and flexible seal. You might consider using butyl
for this (the form that comes in a tube) but because it would add nothing
to
the strength of the join I would double up on the rivets/bolts.
One argument that might favour bolts over rivets is that you can tighten
the
bolts as needed while rivets apply maximum pressure. If you want to make
sure that the sealant is not all squeezed out of the join, bolts would give
you that degree of control. With butyl, that should be less of a concern.
There is a lot (too much) of information on the net about the pros and cons
of various sealants. I would be interested to know which sealant Stan would
recommend.
Widen the gap with wooden wedges/shims ahead of where you are injecting the
sealant to ensure that the sealant is injected well into the gap. Put the
shims in first as needed and then remove each as you reach that point with
the sealant. That will allow you to get more sealant into the join and the
removal of the shim will squeeze the sealant immediately while it is still
uncured.
Another thing I would worry about is removing all of the rivets at once.
The
hull is very thin and very flexible at the top and I would worry about the
whole thing changing shape one all of the rivets and sealant has been
removed. Assuming that the boat is on its trailer when you do the job and
knowing that the trailer applies uneven pressure to the hull, I would not
want to find that the boat hull and deck became misaligned. That might not
happen but at the same time you can avoid the risk by doing sections of
about 8' at a time. Remove the rivets in one section only after the
previous
section has been sealed and riveted/bolted. Alternatively, replace some of
the rivets (say every 4') temporarily with bolts that can be easily removed
as you work your way around the boat.
I would definitely add more rivets or bolts to those presently on the boat
especially around the fore deck. I think that the waves on the bow work the
hull-deck join as the hull is very flexible in comparison to the rigid deck
and that is where the sealant can/will break. Certainly on my boat it was
only at the front section that I had trouble with leaks.
Finally, if you use rivets, I would definitely use washers with them.
Good luck
Graham
-----Original Message-----
From: rhodes22-list-bounces at rhodes22.org
[mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of The Rhodes 22
Email
List
Sent: December-09-14 6:04 AM
To: rhodes22-list at rhodes22.org
Subject: Re: [Rhodes22-list] Deck joint repair.
Chuy,
I'm a little short on time, but I will try to detail the procedure the best
I can.
Remove the rubber insert from the rub rail. In most cases it has
deteriorated enough that you will want to replace it with new. Having
removed the insert you have found the pop rivets which you will have to
drill out in order to remove them. Most of the rivet will fall into the
interior of the boat and you will continue to find them for several years.
After drilling all the rivets out you will clean the deck joint (area
between the two surfaces) with something small enough to remove the
hardened
and worthless caulking.
The cleaner the joint is, the better. I recommend and used on my boat a
one
part polyurethane sealant called NP1. It is manufactured by a company
called Sonolastic and is primarily used in roofing applications so it has
great adherence and weathering properties. It will stick to anything and
can be easily found through Google.
Now comes the really important part, filling the voids in the seam. Using
a
caulking gun, you will squeeze the trigger as you push the gun forward,
driving the caulk into the seam. This is reverse as to how you normally
apply caulk, but you want to fill all the voids. Once the seam has been
sealed, replace the rivets which you have purchased from an industrial
nuts
and bolts supply house and attach the rub rail. Count the holes before
going and add 10% just because. Do not try to find them at a hardware
store, they don't have them. I used a hand operated pop rivet gun, but I
would recommend purchasing a pneumatic or electric gun to save wear and
tear on your hands and arms.
Simply sealing the top and bottom edge of the rub rail doesn't do squat for
stopping water infiltration and besides, it looks crappy.
Good luck and if you have any further questions don't hesitate to ask.
Rummy
In a message dated 12/8/2014 12:52:48 P.M. Eastern Standard Time,
rhodes22-list at rhodes22.org writes:
Rummy,
Searched list but did not find any material on your deck join repair. I
would appreciate if you could repost.
Chuy
---- The Rhodes 22 Email List <rhodes22-list at rhodes22.org> wrote:
> Chuy,
> If you search the list archives you will find a post from me
> detailing
the
> easy resealing of the deck joint. If you can't find it, let me know
> and
I
> will repost to the list. It's a not to difficult repair, but if not
done
> correctly, you will find yourself doing it all over again.
>
> Rummy
> __________________________________________________
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