Stretching a trimaran

I remember reading on here about how a Buccaneer, I think a 28, was stretched by moving each frame 4cms apart to give an extra couple of feet or three. However, I cant find the post just now to reference it, goodness I've tried...

I've got plans for a Farrier F32AX, and having the visited both the aft cabin and aft cockpit boats would love to have the bigger cabin of the aft cockpit with the aft cabin as well. One thought of having my cake and eating it is to stretch the boat to gain an extra foot in between the beams, by moving the form frames 5cms apart and increasing the width of the foam core.

I wanted to ask you guys your thoughts and feelings as to whether stretching the boat like that is a really bad idea and how it is going to alter the balance?

From looking at other Farrier tris, for example the F32 and F35c, all the extra length was in the stern and equally with the F36/39...

 

Suggest you sign up with the Farrier group (its free) and post your question with them. Several of the people have extended their boats and can advise. Several designers say you can do small length extensions to their designs (EG 5%) but you need to understand any implications. PS Designers get annoyed if you widen a design as that has real implications in structure, strength, stability and performance of both the hull and rig. Try: main@FCT.groups.io | Home

 

Thanks for your reply, oldmulti.

I'm an active member of the Farrier forum and think it is such a fantastic resource with an enormous amount of collective wisdom. I've asked a couple of the builders there about stretching the boat and have had mixed responses, which is why I am posting here. Ian Farrier, of course, is held in great respect and of course, like any designer, didn't want people, like me, messing with his plans, as the consequences could be downright dangerous, sail poorly and damage his brand. Totally understand!!

However, as you say certain people did extend their boats, and perhaps some with his blessing. Unfortunately I'm not able to ask him today, so reaching out to other knowledgeable folk.

For me I always thought that it would make more sense to stretch the boat over it's whole length, so proportionally the boat would be similar, rather than simply add an extra foot in between the beams where I want it.

One builder told me that he thought it would be strange to stretch the whole boat, and if so then it could well have a detrimental effect on the centre of lateral resistance. He suggested that perhaps the mast would need to move forwards...

Another builder, who stretched his boat fore and aft, said that as long as the mast and dagger board where in the same relation to each other and that the foot of the mainsail wasn't lengthened. He didn't see a problem with a 5% stretch and didnt think there would be a need to increase the thickness of the foam sandwich. I would just have to come up with a new attachment point for the traveller....

So, I'm just casting my net a bit wider and thought I'd ask here as I've read several posts about tris being stretched. Some of which incredibly successfully by all accounts!

 

Would I do it ?
Yes I would, I agree with you & the second builder.
But I would be throwing in some extra carbon to so that I could sleep at nite.
Matting is expensive, but twill is cheap.