Sails for Multihulls How Different from Sails for a Monohull

[savageseadog]

Was offered a sail from a cat not sure if would fit but was interested to know if multi mains and jibs are vastly different from mono sails anyway.

 

[Talbot]

Infinitely better of course! /forums/images/graemlins/laugh.gif

No real difference, i.e. if the measurements are suitable, then it doesnt really matter which it comes from.

 

[dunedin]

Depends type of multihull - light and fast cats sail much faster and hence apparent wind well forwards, therefore sails tend to be very flat cut

 

[snowleopard]

And heavier fabric as the boat can't spill wind by heeling.

 

[Adonnante]

Also bear in mind a cat sail will be in a heavier fabric and construction due to the stability of boat which will usually produce a heavy and/or more expensive sail. Jibs will have been cut to accommadate the increased forestay sag of a cat and the main usually will have a much larger roach to keep the centre of effort low, this also has implications on sail twist and mainsheet tension.

 

[AngusMcDoon]

[ QUOTE ]
main usually will have a much larger roach to keep the centre of effort low

[/ QUOTE ]

Hmm. Tris have a large roach, because it's an efficient sail shape. The greatest extra roach compared to a monohull's (with backstay) sail appears to be near the head, so wouldn't the centre of effort be higher?

This sort of mainsail wouldn't fit a mono with backstay anyway.

 

[Adonnante]

If the mainsail were to be of the same area a more triangular sail would have to increase the height of the mast. Boom length tends to be at a maximum limited by the length of the boat. The taller mast will give a higher CofG

 

[AngusMcDoon]

I see what you mean now. I was assuming an equal mast height, not an equal sail area.

Still reckon that the primaray reason for an increased roach is sail shape efficiency though, lowering CoE a secondary reason. That's what my sailmaker (UK McWilliams) says anyway.

 

[Otter]

A lot of cats, particularly Prout's and Patterson designs, have the mast set much further aft than on a monohull, this creates some perculiar sail shapes!

 

[jamesjermain]

To sum up what's being said: a multihull main will almost certainly be unsuitable because of teh roach (wont fit through the backstay when tacking) and the jib/genoa will be too flat cut for full efficiency and will be unnecessarily heavy. It will also, probably, be high cut in the clew to rise over the bridgedeck. I would thank the gentleman kindly but decline his generous offer.

 

[snowleopard]

Or you could accept the sails and then get a proper boat to go under them /forums/images/graemlins/wink.gif

 

[savageseadog]

[ QUOTE ]
Or you could accept the sails and then get a proper boat to go under them /forums/images/graemlins/wink.gif

[/ QUOTE ] When are you going to separate the two boats you've got stuck together? Did they forget to chainsaw them apart on the production line?

 

[Deleted member 478]

Now listen carefully Mr Savageseadog, there are only three types of boat:
- a catamaran
- half a catamaran
- and a cat and a half.

Furthermore, if is not a cat, it's a dog.

Got that?