sail help

[RichKrough]

A couple of years ago I bought plans for a Hartley TS16. I started last fall and am presently waiting for warmer weather to begin expoxy coating and painting of the bottom prior to turning it over. My wife was at conference in Newport last fall and on one of the days they got go to sailng. The boat my wife was on was a small catboat and the skipper gave her and the others a lesson in sailing and to my wife's delight she could sail the simple gaff rig. so when my wife got home guess what she asked?

Fast forward to now. I had contacted Hartley boats last fall about moving the mast forward a couple of feet and using a single gaff, They replied it should work fine. So a couple of weeks ago I talked to a local guy who makes sails as a sideline. He told me to obtain the CLR and COE from the orginal sail plan and he would come up with a single gaff rig for the boat. I figured the proper thing to do was to email Hartley and ask if they had that information.
The reply I got from Hartley was the recommendation to find another sailmaker, They said any competent sailmaker would have asked for the orginal sailplan and from that he would have developed a sailplan himself. I emailed Hartley back this morning asking if I could pay them to design a single sail Gaff sail plan for the boat.

So my questions are:
1. Am I approaching this the right way? should I ask and offer to pay the boat's designer to come up with the sail plan I want? or is this a service that a competent sailmaker usually performs as part of his service?

2. I went looking for sailmakers on the internet
while there I saw several of them listed used Gaff sails for sale. If my orginal sail plan called for 180 sq ft off sail would I want the same amount in a gaff sail? Could I buy a used gaff sail close to 180 sgft determine the COE from that sail and locate the mast and rigging on the boat to suit the sail?.

Thanks

Rick

[ 03-08-2006, 01:37 PM: Message edited by: RichKrough ]

[RichKrough]

To clarify,

Here is what I have now:

http://www.hartley-boats.com/images/14d.jpg

here is what I want to do:

http://home.nycap.rr.com/richboat/eastc1.jpg

[Uncle Duke]

Rich,
A few comments and questions....
Hartley is correct, you (or a sailmaker) can use the existing sailplan and boat plans to determine the existing (as designed) CLR/COE. There are a few methods for doing this, with the easiest being to simply draw lines from each corner to the middle of the opposite side. The triangle which is then formed (assuming the lines do not perfectly meet) shows where the COE is.
There are better methods which take into account loss of drive at the mast, etc. - someone here, smarter than me, will know how to calculate that.
Given that, you drop that point down to the profile. When you put a gaff sail instead, that COE should also be directly above that point.

Questions now:
1) Are you intending to have an unstayed mast? If so, you really need to look at the strength required at partners.
2) Moving the mast forward will affect the trim of the boat, which might (in fact) alter the CLR, which then moves the discussion back to the top - you then need to know the original CLR, determine the COE of the original rig, and calculate the "lead" of the original design. Then you want the new COE (for the gaff sail) to have the same percentage "lead" forward of the new CLR.

And, some calculation needs to be done for height of COE - i.e. some compensation for heeling moment. You can increase the sail area, I think, as long that "heeling force lever arm" does not exceed the original.

I think....

[Ian McColgin]

There are several issues of interest in your plan.

Firstly, the final sail area may well be greater than the designed area for jib and main. The gaff rig has it's center lower, even with a highly peaked gaff which I recommend in general.

The mast location is going to end up ahead of the cabin and you'll probably want to shift to a keel step, especially to allow for a rig with no shrouds, just a headstay.

I see no reason why a hollow birds eye mast (make the gaff hollow as well) would not be light enough that you could plant it right by hand but you might want to have stowed on your trailor down along one side of the keel perhaps three poles that can be set up straddling the bow to act as a stepping and striking derrick.

You will need to seriously reinforce the deck in the way of the partners gunnel to gunnel. The step takes a great deal more wracking strain than with a stayed rig and far less compression strain. Get some sort of ring or triangular structure to connect the under-deck structure to the step and take the wracking off the planking.

Even if you make a sail with the fore&aft center about where the main and jib centered, the actuality of gaff behavior can be a little odd. Give the mast step plenty of fore and aft travel and wedges, maybe even give the partners some serious oval to be adjusted by wedging, so you can find the correct place with the mast about as upright as you cut the sails for.

Once you have all this right, you can tack glue the step wedges and number the partners' wedges so everything goes up and down correctly.

You will want to wedge as that's how the mast stays nice and quiet. It really won't take any time to pop the wedges in and out once you're used to it. The final set of partners' wedges should end their incline at a cut lip right where they are supposed to land so you can get some in without them dropping through till their opposing wedges are in and so it's easy and obvious where you're tapping them down to. A purpose made poke stick will be handy for getting them out. Once perfected, all this is still no harder than the tabernacle approach.

On the sail itself, any good sailmaker really ought to be able to figure the boat's center of lateral resistance and apply a little lead. Your plans should have this anyway but if not, derive it.

Have at least three reef rows and have her rigged properly for easy reefing from the cockpit. I think that the reefs should rise towards the clew such that the boom will be lifted higher from the water the more you reef.

If you send me a note, I'll sketch some of the ancillary lazy lifts and reef controls that are so often left out. It's easy to end up with over a dozen bits of hardware on the boom and five on the cabin top coming back from the mast. All this takes a modicum of thought to be really handy, safe to use, orderly and never spagetti.

The main sheet takes some thought as it will be about five miles long. Have it over a plain rod traveler with the end free to be cleated on either side of the helm. This gives you the greatest chance of fully using one of the catboat's most wonderfull benefits - letting the sail way way out - and still having use of the cockpit.

Remember, reef early and often! You'll be impressed at how much faster you sail if not over-powered. Once you learn how to trim the sail, you'll also be a bit surprised at how weatherly and powerful the rig can be.

G'luck.

Edited to add: I see you're going with the open boat version.

[ 03-08-2006, 02:17 PM: Message edited by: Ian McColgin ]

[Todd Bradshaw]

Uhhhhhhhh....guys........This is kind of pushing the boundaries of sailmaking. Yes, we're all brilliant, of course :D , but most of us aren't really trained in boat design and at 180 sq. ft. you're looking at something big enough to get somebody hurt.

Figuring out a new plan that has the same CE and the same area is no big deal and neither is making mods to that plan's sail area or C.E. location when needed - but...I'm not the least bit sure that a catboat-style gaff rig should have the same area and amount of lead as a Marconi sloop does and suspect doing it that way may not be the best choice. That's why they invented boat designers.

If one of you would like to show me how a sailmaker is supposed to figure out the CLR/CLP of the hull without at least a good profile drawing with all the foils in place and which is more sophisticated than the old cardboard cutout balanced on a knife, I'm all ears.

In any case, the sailmaker's primary job is to translate the flat profile that a designer has drawn into a three-dimensional foil and be sure that the construction details are sound (we don't know all the in's and out's of boat design, they quite often have similar gaps in their knowledge of proper sail design and construction). Some sailmakers will do some rig design work. Most will be clueless about how many knots of wind it's gonna' take to rip out the chainplates or even knock the boat over and without the real design data they're not going to ever be able to tell you those things (even if they know how which most, myself included, don't). I'm a bit surprised that the company has either so little regard for their design or so much faith in the boat design abilities of sailmakers that they would suggest that "any competent sailmaker" should be OK for re-dsigning half of their boat, but perhaps once they sell the plan they don't really care what happens to it. Most designers are a bit more picky about folks making sweeping changes to their designs.

I do a lot of rig design for my customers, but they're small simple rigs for boats that I have a lot of experience using and I stay within my comfort level. Two days ago I turned down an opportunity to re-design a Hartly rig where the customer wanted a 200 sq. ft. gunter rig and mentioned sailing in salt water in 25 knots of wind. Just the thought of that scenario ought to send the liability alarm into overdrive! If the company isn't interested in drawing up a gaff rig for their boat (complete with things like scantlings for moving the mast, spar diameters, whether or not it needs stays, amount of sail area, position and height of the new C.E. for proper performance, etc.) then go find a genuine boat designer who will. Without real boat design knowledge and data, anything else is just a guess. The sailmaker who re-rigs your boat can do nothing more than guess about it's eventual performance. He doesn't have enough data (or training in most cases) to do anything else. Who wants to go to all the trouble to build a boat when nobody really has a clue how well it will work?

Send your sailmaker a sailplan and let him do the job he's trained to do. Trying to work an already built, used sail into the picture is possible, but may just make the issue more difficult to resolve. I suppose it would depend on what you can find.

[Stiletto]

Others know a lot more about gaff rig than I do, but the Hartley trailer sailers sailed very well with their original sailplan. You are making a change for essentially domestic reasons. :rolleyes: (which I have sympathy for)
The original rig is not hard to operate and in my opinion the boat will perform best with it left unaltered. Build a catboat next.

[ 03-08-2006, 04:46 PM: Message edited by: Stiletto ]

[RichKrough]

Thanks for the replies. This isn't something I have to do, nor am I going to build another boat. If I can use a catboat rig and make it work, great! if not I still am happy with the orginal sail plan.

Last night I did some reading and internet searching. I compared 6 catboats of similar proportions and displacement, The sail plan for those boats ranged from 152 sqft to 170 sqft. SA/DP ratios ranged 18-22.(the Hartley sa/dp ratio is 23 at 1400lbs ). If I take an average of similar displacement catboats I get 160 sqft of sail(sa/dp ratio of 20 at 1400lbs) I know there is more to the equation but it seems a good place to start. I'll wait to see what the N.A. has to say before I commit to anything.

Rick