Thread: Sail Design for the GIS

Hi MIK,

The schematic doesn't seem to have made it through? I get what you are saying though, makes a lot of sense to run it with the leech and use a patch running down the luff to keep things tight there. Here is another sketch with my seams running as described. Should I finish the edges by folding over and stitching like on the pdracer sail plan, or would it be better to cut a 3" or so strip to fold over the edge and stitch through the 3 layers?

I would like to invoke keyhavenpotter here. His sails for the RAID were just fantastic and made to this scheme.

It is important that the luff doesn't stretch, so I would cut a piece of cloth maybe 4 or more inches wide with the threadline up the long axis and fold it around the luff (near vertical front bit) and sew. Always round off the corners so they don't lift up.

Along the foot ... there are a couple of tricks. You could cut a simple reinforcement patch along hte bottom of the sail like the PDR lug - again with the threadline parallel to the straight line of the foot.

There is also another method a sneaky sailmakers trick. The second bottom panel shoujld have the seam allowance on the bottom edge. Mark out the bottom panel with the curve as in the drawing but leave extra cloth. either end. Cut the curve accurate, but leave some extra length on the opposite side. Then you flip it over and stitch the curved edge to the bottom of the second bottom panel. I have never made a sail with this trick so you might end up having to rip the seams and redo it if it is a disaster. But it mean the foot of the sail has the threadline in the right direction.

It does mean that the bottom part of the leach will have the threadline in wrong direction but you could put a patch on the back edge to prevent that. Might be trying to be too smart!

MIK

Originally Posted by joern

Hi Al,

SNIP

But : you can do leech battens to support a rounded leech. They allow more area of the sail and therefore a tad more power.

Best wishes from Bonn - Jörn

I am not convinced a small roach (rounded leach) like Michael does either benefits greatly or causes much of a problem. I suspect he just likes a rounded leach.

With bermudan sails with full length battens, but very big roaches can provide a lot of horsepower to conventional boats. The best article I have seen on this was by Steve Dashew, designer and builder (one of) the most interesting large cruising boats in the world. Believe it or not these boats are set up to be handled by a cruising couple. A WEALTHY cruising couple as a 70 ft boat set up for two people is something special indeed.



He wrote an article about big roached mainsails that extend further back than the backstay on yachts.
See from page 89 in this google book (pretty happy to find it for you guys to read too)
The New Book of Sail Trim - Google Books

It is a great article - one of the ones that changed my thinking.

But the difference is that the triangle represented by the backstay is a big limitation on yachts, so you need to consider ways of getting extra area without having a longer mast or the complication of running backstays.

A lot of trad boats can get a big benefit from a larger roach as they are somewhat underpowered. The Goat was drawn up from experience with performance two person boats in Australia. So the 105 square feet of sail is already much larger than the 80 square feet of most sixteen footers. The assumption was that people would reef when they needed to.

So the extra sail has already been added! I do think the short battens are a little bit of an extra complication ... but if someone likes the idea of having them I won't argue to stop it. Particularly when sorted out by a sail maker as good and thoughtful as Mike. I am sure incorporating his own idea has given him a special bond with hte Goat so he will do an extra good job on the sails!

MIK

I found making MIK's sails to his design using 4oz dacron worked out really well. No complication, just used the PDR lug rig instructions and the numbers from the rig as designed by MIK. All roundings, shapes and reinforcements.

The bit I added was using Sailcut4 to give me all xy plot points for the two main panels which made it easier to lay out the shapes on the cloth, including teh rounding and hollows.



I think the two full battens I included also helped keep the induced shape from the yard in place. My thoughts were that with a loose foot lug sail the shape starts at the yard and hopefully carries on all the way down. Since this area is flat cut in will have a tendency to instibilty of shape. My profiled battens, only £6 cost from local sailmaker and sanded over the leading edge in the same way my windsurfing sail battens are.

Not sure if this is helpful or relevant, but please ask if my experience with sailmaking can help in any way.

Pleased to say the garden is all sorted now my back's recovered.

Brian

Thanks for that.

Brian commented privately that he can't make head nor tail out of what I wrote above about the alternative way of flipping over the bottom panel.

In the cold clear light of day I can't either!

It is great that he confirms that the OZ PDR method works fine.

Where is a pic of the sails in action ...

Thanks Brian!
The pic is very helpful, as is the info on having used the PDRacer plans. This is what I will be doing too, (using MIK's specs for the edge curves) Since it's a flat sail, I'll use my CAD program to lay out the seams 2d to facilitate cutting, then it is some quality time with the sewing machine. Glad to hear you are feeling better too Brian. There are few things worse than not being able to move around and get things done. Also thanks Dkirtley and MIK for the seam layout info. It all makes sense now and I feel like I'll end up with a pretty good product. Plus it will be cool to tell people I made the boat, and the sail!

I'll get on it soon and post lots of pics too.
Thanks again,
Al

How long does it take to sew a Goat sail?

I am wanting to get an idea of how many hours at the sewing machine I need to schedule for. I know I will get many different answers but anything will help.

I will be getting a sail kit and doing just the sewing, so cutting the panels does not need to be included in the estimates.

I would say

and afternoon assembling the sail with double sided tape.

An afternoon or an evening to sew the sail.

An hour or two sorting out all the loosed thread ends

An hour or two inserting all the hardware if you have the tools. Are you hiring them, they are expensive to buy.

If you are using a home sewing machine, check that it does not have any plastic bevel gears because these might strip. Our best home machine stripped in this way, but our cheaper machine had all metal drive and did not strip. It did need extra hand turning to cope with the thickest parts of the sail.

Brian

What I was told is that a home machine may be able to punch through even light sail cloth,. but it it struggles at all it will leave uneven stitiching as it sews a lot.

I sewed a Sail rite kit for a 55 SF lug in one day with some experienced help and a Sailrite machine the friends who helped used days before for the same sail type.

I'd say 2 8-hour days.

This is one of the big variables. Some cheap machines do it quite well and some expensive home machines struggle.

The first PDR sails we built were sewn together in a couple of hours. So I thought it was always dead easy. But then later we had a home worker who was interested in sewing the sails up and it was a train of disasters. A large part was that the double sided tape was gumming up the needle - I altered the plans and attached email to keep the double sided tape away from the sewn edge.

I guess if there is a big problem the sail could be carefully folded or rolled and taken to a local canvas goods place - tarpaulin maker, awning maker, Auto trimmer, sailmaker - all of them would probably do a good job.

. If they do it with a synthetic thread and a zig zag stitch it would be OK and because they did not need to cut and arrange it the cost might be quite reasonable.

MIK

MIK

You can now order your sails with your favourite photo on them!

Now that would make trimming hard!

White with a horizontal strip through the middle please!!!

MIK

On a sail note,

Would anyone dissuade me if I decide I want to punch a two small grommets just above my full-length battens for additional tie-downs when I reef? Or do I need to re-enforce the area first?

For the little bit of sewing, I would not even take the chance. It is too easy to sew on a bit of patching and the grommets will hold better anyway.