Hello, are the main sails for fractional rigs different than for masthead rigs? I mean sewn diffently for the mast bend. Am considering buying a new boston sail from a hunter and using it on my irwin. Want to make sure it will be ok. luff, leach and foot are same for each.
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Mast Bend Measurement
The mast bend / luff curve is indeed a factor in any mainsail design, and would usually be measured by the sailmaker if you were having a new main 'built'. A frac rig with single swept back spreaders could have at least 4-6 inches of pre-bend, and be significantly different from a mast head single spreader rig with a stiffer straight mast and straighter luff. Also, depending on the Hunter having or not having a fixed back stay, you could find a lot more roach on the Hunter Main than cant be accomodated with a fixed backstay on the Irwin. You definately would wamt to trial hoist the main to see if it will work and be able to return it. I would think you could hoist it to full height, tighten the outhaul to maximum and see if there is a lot of extra depth or wrinkles in front of the battens. You won't want a mainsail that is too full and can never be flattened.
The mast bend / luff curve is indeed a factor in any mainsail design, and would usually be measured by the sailmaker if you were having a new main 'built'. A frac rig with single swept back spreaders could have at least 4-6 inches of pre-bend, and be significantly different from a mast head single spreader rig with a stiffer straight mast and straighter luff. Also, depending on the Hunter having or not having a fixed back stay, you could find a lot more roach on the Hunter Main than cant be accomodated with a fixed backstay on the Irwin. You definately would wamt to trial hoist the main to see if it will work and be able to return it. I would think you could hoist it to full height, tighten the outhaul to maximum and see if there is a lot of extra depth or wrinkles in front of the battens. You won't want a mainsail that is too full and can never be flattened.
The sail maker will know how
to cut the sail if you give him the correct rig measurments. Most of the larger sail making companies have patterns already made for production boats and they account for the "standard" rig. If your's is different then he will need to know and Sauer's advice would be wise.
to cut the sail if you give him the correct rig measurments. Most of the larger sail making companies have patterns already made for production boats and they account for the "standard" rig. If your's is different then he will need to know and Sauer's advice would be wise.
The other posters are correct ......
A mainsail for a fractional rig will usually have a different shaped (called 'luff hollow') luff to accomodate the "normal bend" thats induced in the mast. A fractional rig usually carries quite a bit of mast bend for 'normal' conditions. A boat with a non-bendy mast will only typically have included (somewhat standard) approx. 3/4" of extra 'luff shape' (prebend) for each set of spreaders .... and that most sailors ignore. If you would take a mainsail from a frational rig that normally is set up with lots of mast bend and apply it to a non bendy mast .... the sail will probably have much too much draft. Trying to match a sail from a boat with a fractional rig to a boat with a non-bendable mast probably isnt going to work .... without major luff recutting and reshaping. Such (hand) work is very time consuming and usually costly .... and if the sail already has 'permanent' stretch and change of shape due to use ... probably isnt going to be worth it in the long run.
A mainsail for a fractional rig will usually have a different shaped (called 'luff hollow') luff to accomodate the "normal bend" thats induced in the mast. A fractional rig usually carries quite a bit of mast bend for 'normal' conditions. A boat with a non-bendy mast will only typically have included (somewhat standard) approx. 3/4" of extra 'luff shape' (prebend) for each set of spreaders .... and that most sailors ignore. If you would take a mainsail from a frational rig that normally is set up with lots of mast bend and apply it to a non bendy mast .... the sail will probably have much too much draft. Trying to match a sail from a boat with a fractional rig to a boat with a non-bendable mast probably isnt going to work .... without major luff recutting and reshaping. Such (hand) work is very time consuming and usually costly .... and if the sail already has 'permanent' stretch and change of shape due to use ... probably isnt going to be worth it in the long run.
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