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Yet another Trimaran build


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Lookin real good. Any idea how the FD floats compare with the Farrier floats displacement wise? Hope it all fits but you can still be a bit over-width without any hassle trailing.

 

Thanks. Compared with the F82 floats, the FD floats are 1 meter longer with a squared off stern for the rudders. There is not nearly as much rocker as the F82 ones have. The floats are slightly less tall (but within 30 mm) and approx 150mm wider and the volume is carried lower and for longer. I would guess the FD floats fully submerged would displace approx 1800Kg - I've never had any displacement figures for the F82 ones but I'm guessing the FD floats are maybe 400Kg greater in displacement than the F82 jobs.

 

The F85SR is said to have another 600lb (272KG) of displacement compared to the F82 Jobs so I believe I have gone slightly greater in displacement again. They are still tidlers compared to Sam's floats (one of which you can see sitting in the background of the bow-on photo).

 

Looks like an interesting project, although such projects can be a worry, and cannot use my name, but it looks like yours is being done well. A couple of points:

 

The F-82 floats displace 1653kg and the F-85SR floats displace 1944kg. Very hard to get them any larger, as folded beam can then go over the legal limit, or interior has to be reduced too much. The only way is to make them longer, but that creates problems of its own, and I don't favour too much increase.

 

One problem can be excessive bow overhang to where the float bows can be too prone to break off. I use extra reinforcement on my float bows to cover this, and if you got the F-82 plans with your F-82 center hull then these should detail this. Any extra overhang will require even more reinforcement, so this is something you may be wise to check.

 

The other way to effectively increase float displacement is to use curved lifting foils, which are an option for the F-85SR, and I can supply the foils. Expensive, I know, but they are just about solid carbon, as the loads on them can be horrendous.

F-32SRFoils.jpg

However, foils can increase the effective float displacement significantly when in use, to where the boat may be able to fly just on the leeward foil. We have not managed to do it yet with the F-32SR, but it is early days yet.

 

Your rudder pin also looks a little light - rudders can be very highly loaded on a trimaran and I use 1/2" (12.7mm) solid rod on the F-85SR, which uses a reinforced F-22 rudder case with a longer higher aspect blade. Composite cases also need a lot of carbon to be strong enough.

 

There's now one F-85SR building in Auckland, but note that I am withdrawing all my plans from sale on the 25th September, to concentrate on production boats, and from then on the F-85SR will only be available as a kit or the sail away boat.

 

Ian Farrier

Farrier Marine (NZ) Ltd.

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Thanks Ian - I never refer to it as a Farrier but the amount of people who come up to me and ask "what sort of Farrier is that??" is not funny and I have to launch into a long explaination about it each time. I'm very keen to see an F85 if/when one should appear in Auckland.

 

I have found the float volume to be Ok upwind (where you can feather in the gusts) and downwind (where you can steer down to depower) but on a reach I get distinctly uncomfortable and am reliant on the crew to "dump" - I guess this will always be the case at some stage of the game even with larger floats or foils. I am actively thinking about some sort of lifting foils config like you have for the F85 to at least delay entry into the "death zone". I would have to also put a centreboard in at the same time which I'd hoped to avoid but I don't see an alternative. I've done endless drawings with S foils etc and in some conditions they would be OK but I can't work out how you could dial the appropriate lift vs leeway resistance equation for all occasions with just one foil... Those foils of yours do look very nice, I may be in contact about them.

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Don't worry about the float sinking Dean, it's actually a good safety point. PE will sink the ama and I have had the mast nearly parallel with the sea, and it pop's right up again.

But I think you will raise the main hull before you sink an ama.

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