[Rhodes22-list] Re: Fully Battened Mainsail From JSI W/O Modifying The Masthead
Roger Pihlaja
rhodes22-list@rhodes22.org
Tue, 27 Aug 2002 05:59:13 -0400
Richard & Toad,
After I wrote to you last night, I was looking over some of my design
calculations from the mainsail upgrade project. There is another option you
might want to consider if you don't want to modify the backstay attachment
point on your masthead casting as I did.
The backstays run at a nominal angle of 63.6 deg relative to the horizontal
when attached at the standard point on the masthead casting. My backstay
extension moved the top attachment point of the backstays aft by about 5".
The same amount of reduction in backstay/leech interference can be achieved
by reducing the luff length on the mainsail, thus lowering the height
achieved at maximum mainsail hoist on the mast.
Tan(63.6 deg) = (Delta Y) / 5
(Delta Y) = Tan(63.6 deg) * 5 = 10"
New Max Luff Length = 21' 8" - 10" = 20' 10"
I opted not to take this option because, all else being equal, it would have
reduced the mainsail area by almost 4% & I was being greedy. I wanted it
all; maximum possible mainsail area, maximum possible roach, maximum
possible mainsail aspect ratio, etc. However, if you are not handy with a
MIG welder or find the notion of modifying your masthead casting abhorrent;
then, you might find this reduced luff length option more attractive.
Remember that all the measurements used to build this mainsail are specific
to my 1976 Rhodes 22 & may not be appropriate for your newer boats.
This is what happens when engineers go sailing...
Roger Pihlaja
S/V Dynamic Equilibrium
----- Original Message -----
From: "Roger Pihlaja" <cen09402@centurytel.net>
To: <rhodes22-list@rhodes22.org>
Sent: Monday, August 26, 2002 4:51 PM
Subject: Fully Battened Mainsail From JSI
> Richard & Toad,
>
> I have the following address & phone numbers for JSI:
>
> Johnson Sails Inc.
> The Sailing Source
> P.O. Box 20926
> St. Petersburg, FL 33742
>
> 800-234-3220
> 813-576-1306 (FAX)
>
> I don't know their internet URL.
>
> I ordered my mainsail in November, 1994 for a March, 1995 delivery. The
> "Snowflake" winter discount price was $776 with free S&H when I placed a
50%
> deposit at the time of ordering the sail. My customer service rep was
> Leslie Ramsdell. My invoice number was 075296-0, dated 03/03/95. My
> customer number was 707800. The product was called a "club race mainsail"
&
> I ordered one additional reef point, insignia, & 3 full length battens.
> Surely, with one of those numbers, they can find the order & sail cutting
> data.
>
> I supplied the following measurements:
>
> Max Luff: 21' 8" To Band
> Max Foot: 9' 0" To Band
> Max Bend: 3"
> A: Aft face of mast to bearing point of tack fitting: 1-1/2"
> B: Top of boom to bearing point of tack fitting: 1/4"
> C: Aft face of mast to bearing point of reef hook: 1"
> D: Aft face of mast to end of groove or track: 5-3/4"
> E: Bottom of the luff groove or track on the mast to top of boom: 10-3/4"
> F1: From back of mast along boom to 1st reefing block or padeye: 8' 2-1/2"
> F2: From back of mast along boom to 2nd reefing block or padeye: 5' 9-1/2"
>
> X: From bearing point on boom outhaul to the top of the boom:5/8"
> Y: From black band on end of boom to the end of the bolt rope groove: 7"
> Z: Width of shackle jaw on boom outhaul: 1/2"
>
> Outhaul Car: No
>
> Luff: 7/16" Sail Slugs
> Foot: 7/16" Bolt Rope
>
> Included in above price: 1st reef point, tapered battens, shelf foot,
> cunningham, draft stripes, numbers, radial reinforcements, leech line,
> telltales, sail bag, & sail ties
>
> Sail Cloth: 5.6 oz/sq yd Dacron
> All Grommets & Other Hardware: 316 SS
> Headboard: UV Stabilized Engineering Thermoplastic
>
> You guys should know that Dynamic Equilibrium has a 3:1 boom downhaul to
> adjust mainsail luff tension. So, I do not use my cunningham grommet & I
> instructed JSI to design & build the sail for applying luff tension via a
> boom downhaul. FYI, this method of applying luff tension works so much
> better than a cunningham that you should consider switching over to it.
>
> You should also know that after I got the sail, I found there was some
> interference between the leech & the double backstays, particularly with
the
> boom in the upper position. Remember, the sail is very roachy. If I was
> careful, it was possible to gibe from one tack to another without hanging
up
> the battens on the backstays. But, I was afraid I'd get careless one day
&
> break a batten. In addition, there was the issue of chafing the leech
> against the backstays on every tack. I just hate having to baby my
> equipment.
>
> My solution to this potential problem was to modify the masthead casting.
> It turns out the ID on the fitting at the rear of the masthead, where the
> double backstays attach is 1". I took a piece of 1" X 1" X 7-1/2" solid
> aluminum barstock & MIG welded it onto the back of the masthead. It
extends
> aft 6" from the rear of the masthead casting. So, there is about 1-1/2"
> sticking into the masthead casting & it's MIG welded all around. After
> welding, I rounded all the square edges to streamline the aluminum
extension
> & thru bolted a HD padeye for the backstay attachment point out near the
end
> of the extension. To prevent the thru bolted nuts from ever coming loose,
I
> tack welded each of the nuts to the studs on the padeye. The net result
is
> that my double backstays now attach about 5" aft of the standard
attachment
> point at the masthead. My full length battens & roachy leech never
> interfere with the backstays now. My design is probably overkill, but I
> never worry about my backstays coming loose, chafing, or breaking
something
> at the masthead. We sail Dynamic Equilibrium hard & frequently go out in
> pretty rough conditions. Sailing starts to get fun when they post the
small
> craft warnings, don't you agree?
>
> Oh yes, I shouldn't forget to mention that I've also beefed up the
> attachment of the masthead casting to the top of the mast. Instead of pop
> rivets, my masthead casting is drilled & tapped for 1/4-20 UNC X 3/4"
> stainless steel round head machine screws. With all the extra stress at
the
> masthead from a tri-radial spinnaker & the extra leverage of my extended
> backstay attachment system, I didn't trust the shear strength of the pop
> rivets. Don't forget to isolate the stainless steel from the aluminum
with
> a good anti-seize compound during assembly.
>
> Good luck guys. I've been very happy with this sail. It's been holding
up
> very well. The shape still looks crisp & fresh even after almost 9
seasons
> of sailing. The only maintenance I've had to do has been annual cleaning,
> minor restitching last year at the headboard, & I had a 3rd reef point
> installed 2 years ago.
>
> Roger Pihlaja
> S/V Dynamic Equilibrium
>
> ----- Original Message -----
> From: "Christine Allison" <sailnut@asan.com>
> To: <rhodes22-list@rhodes22.org>
> Sent: Thursday, August 22, 2002 8:28 PM
> Subject: Re: [Rhodes22-list] Mast Bending & PHRF Rating
>
>
> > Message<I have 3 full battens on my mainsail. It's very roachy & holds
> its
> > shape very well. It's from JSI in Florida. I have sail slugs on the
luff
> &
> > a bolt rope on the foot. Hoisting & lowering are not a problem. It
will
> > sometimes fall down the mast when I let go of the halyard.>
> >
> > This sounds like what I am looking for. Do they have the measurements?
Do
> > you have their URL? Did you order any special options?
> >
> > At the risk of prying what did your sail cost?
> >
> > Richard Smith
> >
> >
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