Light wind sailboats

Question: is that main cut with the threads running parallel to luff and foot? Reason I ask is because that creasing is exactly how an old mainsail looked on a model boat I had when I was a kid, and that was the cause.

 

The sail in the picture is not pretty. From appearance only, I guess that it is less than efficient. That your jib pulls better, sort of affirms that guess. That the main works better loose footed is another clue.

Do yourself a big favor and buy a sail from a professional sail maker. Not a big sail either. Nor a big name sail maker. I have a 60 sq. ft. sail that I bought from Harold Paysons little outfit. It is used on the Cartopper, Gypsy, and several other of the Bolger designs that Payson used to build. I paid about $135 a few years back and it has been excellent. The sail is made by one of the old line lofts in Maine. They know what they are doing and they do it well. That little sail on my 16 foot flattie routinely outruns Sunfish, Precision 16s and several other boats with more sail area, all in light to moderate air. Area is not everything, A sail that pulls well is.





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I see, so it isn't so much the sail area that matters in light wind as the sail shape? Would an old Hobie 16 mainsail work if I recut the foot a bit higher?


So to design a boat for light wind sailing, what sailplan is recommended for a sloop? Gaff? Sprit? Square top bermuda? Big genoa? Little jib?

 

It's both. Having a perfect shape isn't much good if the sail is too small. A large sail with a terrible shape is no good either.

An old Hobie sail should work fairly well, as long as you get the batten tension right and "pop" the battens when you tack or gybe. You have to do this with fully battened sails in light airs, because if the battens stick with the curvature inside out you will stop very quickly.

Gaff and sprit will always be less efficient for a given area. Sloops seem to go best for a given area when they have a fairly large main and small jib (about 2:1 is a good starting point). A square top main would be good, if and only if you have the controls set up to handle it properly.

 

What about total efficiency for a given mast length? Say I'm limited by mast size? Still a bermuda?

I'm pretty sure I don't have controls set up to deal with a flat-topped main, and I would have a hard time getting the shape right. I think I'll go with the Hobie main most likely. I'm fairly familiar with them.

 

Basic rule in very light airs is you want lots of area, and you want it as high as possible. The wind gradient is more pronounced in very light airs, so a high rig is an advantage.

Square top main would still be best on a limited mast height, assuming it's of reasonable height, but you need accurate twist and depth control (really this applies to any sail).

In light airs twist control is easy as the forces are low.* If you want to use such a sail effectively in stronger breezes too, then you need modern rig controls.

If you want a really short mast and lots of area in a fairly efficient rig that is still easily handled, try a standing lug (see Goat Island Skiff as an example).

*Handy hint from dinghy racing: in very light airs, unreeve your mainsheet and just run it straight from the boom to your hand. Have your hand well to windward of the boom (ie: don't haul down on the leech upwind). Do not use any vang. This makes it much easier to get the twist you need.

And use telltales. You can't sail efficiently in light airs without them.

 

How does the weight of the boom affect things? Is it worth getting one that weighs next to nothing or does it not matter? It seems like it would affect twist a lot.

 

Yup. Light booms are better. However, you could also use a topping lift to help. Racing dinghies don't usually have those.

 

Anything above the CG should be as light as practical, especially spars.

 

The International Canoe is not a great light-wind boat. It's pretty well accepted that the OD IC is only about as fast as a Laser downwind in the light stuff, despite the IC's extra sail area. The IC's rig is considerably bigger and the wetted surface is comparable but the high-aspect IC rig doesn't perform as well downwind in the light stuff as the low-aspect Laser rig.

Upwind the IC is a lot quicker, but it's still not a really great light air boat.

The idea of accepting slow speed in light winds is good; everything is relative.

 

Sorry to say it, but that rig looks like it would be really holding back the potential of the main hull.

As noted by others, keeping the leach open is very important in light winds and if that's a draft line that can be seen in your pic at the head of your main, then it's clearly way too closed for optimum light wind speed. The bottom 75% of the sail looks excessively flat.

Full battens can help to get rid of the "hard points" at the front of the partial battens but they are heavy and can make the sail difficult to read in very light airs. One very popular class around here switched from dacron jibs to fully battened Mylar jibs and found the new sails to be slower in drifting conditions.

It can also be difficult to get battens to pop onto the new tack in light winds, unless you can roll tack which is not likely in a small tri like yours.

The jib looks far too small in proportion to the main. The gap between the two sails is also very large; a smaller gap is definitely more efficient than a larger one, and some classes have found that small overlap can be more efficient than a non-overlapper.

A masthead rig is problematic on a small craft as you can't bend the mast effectively enough to flatten the sail for each end of the wind range.

Hobie 16 mains are (if I recall correctly) quite flat and cut for over-rotating masts. They are also a large, low-aspect sail which does make the H16 surprisingly quick downwind in the light stuff, but putting one on a lightweight tri is sort of like putting a SUV motor in a sportscar; you don't need that much grunt and you can't carry the same sort of mast.

To get some good general ideas, look at the development class dinghies like the British National 12, Norfolk Punt, Merlin Rocket, A Rater (already referred to earlier) and Australian MG14 and NS14. Also look at the International Canoe site.

 

Pneumatic battens . . .

 

Not for me.

 

Have to agree with this. It looks like a toy boat rig rather than something that is actually intended to sail. If you get a couple of decent sails on it you'll be amazed at how much better it goes. Suitable secondhand ones would be fine if they're in good nick.

Also, I'd move your amas up another couple of inches. In ghosting conditions you want it so it's only on the main hull, or with one ama barely touching the surface, to minimise wetted surface. Which brings up another point: a little bit of heel is handy in very light airs to help the sails sit nicely. Again, having the amas set a bit higher would be good.

 

Nice to see your thought provoking post Jammer, per your usual contributions here. It's pretty clear there's a lot more to making a sail, even if it's Tyvek than meets the eye. I've only made one set of sails and have discovered the sail maker earns every dime they charge. It's not the hand work or the panel attachments and layout, but how to actually make one draw nice, place the camber in an ideal location for the particular rig, how to sew it up so it wears well, etc. There's a huge difference between a cheap sail and a good one, with boat speed and pointing ability being the direct result. I just had a custom sail cut and spent an hour and a half on the phone with the sailmaker. I was grateful he knew what he was doing and we worked out the camber location, amount of rounds and their belly locations, etc. This sail draws batter than any in it's class and light air tests against it's sisters, proved the difference between a faux job and a real cut. It's not enough to get the dimensions right, it takes years of experience to actually cut a sail right or more appropriately, know how to cut a sail right, because anyone can sew to the line.