Small trimarans under 20'

wave piercing planing ama +....

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No, I think if you want a wave piercing planing hull you should consider a shape like I showed you earlier....... If you go with a displacement hull you'll have to have a longer, heavier ama.

 

It doesn't match the boat. That's true, the ama would have to be longer, but then I could reduce cross-sectional area, and I think weight would remain about the same. If the ama is going to be in the air most of the time, does it matter as much if it is a displacement or planing hull? Perhaps it would be best to go more for a long and narrow hull so it isn't as effected by displacement, and just know that in light winds it will be out of the water anyways, and in chop, it can handle going through small waves without any fuss.

 

A still interesting link provided to us all by HAYSB on the first page of this thread:
http://www.nauticaltrek.com/35-trimarans

 

Craig Tuffnell just posted some more from his foiling trimaran down in New Zealand! Looks like he's got it well tuned now!

https://www.youtube.com/watch?v=sGzXG50L2Cc

 

Guys, I just did some more research on masts. I don't think the Hobie 14 mast is that unreasonable at 35 lbs. Flying dutchman is about 28 or so and a 49er is about 31. I'll have to get ahold of a H14 mast and see for myself, but it doesn't sound that bad. It's also got a wing profile, which a lot of the dingys won't have.

 

One of the Hobie staff put the H14 mast at 40lb. However it's also the wing profile, or more precisely the effects of that wing profile, that would concern me. The fore-and-aft stiffness of a wing means you get far less mast bend in response to wind increase, and therefore much less of the automatic sail-flattening effect that you get in a well tuned dinghy.

In a cat this automatic depowering is (IMHO) much less important for various reasons, including the amount of stability inherent in the cat platform, so wing masts work well on cats. A small-ama tri may be more dinghy like, especially one that relies on planing lift from the amas.

 

Well, I'm planning on putting a cut-down 18' cat sail on it, so I figured they would be compatible. Square topped cut-down 18 footer sails would have some depowering... I am planning to have it rotating, so a wingmast is preferable.

 

16' Trimaran

Just for the hell of it, maybe the contributors to this thread could discuss what you would like to see in your ideal 16' trimaran. Faster than a beach cat?
Bunks? Tents? Cruising? Racing? Cruiser/Racer? Anything you can think of for a 16 footer.........

 

Racing/fast voyaging, emphasis on light weight performance. Weight under 200 lbs assembled. Cartoppable. Able to keep up with F18s in light wind. Minimum cost.

That's about it for me!

 

So, I did some more design work on my amas for my trimaran, and I'm seeking you guy's opinions on it.

Specs for this version are as follows:

Fully submerged displacement: 274 lbs.
Half-submerged displacement(shown waterline): 122 lbs.
Designed to fly both amas when boat is perfectly level. Boat does not fly main hull. Emphasis on lightweight, so no lifting foils/rudders/stuff like that.
Ama LOA: 10'
Ama beam:0.984'
Skin on frame construction, 8 longitudinal members per ama(3 on each side, 1 top, 1 bottom).
Projected weight per ama: 15 lbs.
Bow profile matches Vaka bow profile.
Hull shape is wavepiercing, similar to AC72 hull shape.

Here is a render.

 

It is going to ride hard with the shallow v bottom.

 

Would you recommend making it steeper? I'm trying to strike a compromise between planing at very light pressure and wavepiercing if it hits a wave, combined with enough overall displacement to support weight at a dock.

 

It's not a planing ama and that is probably a mistake given the length* of the main hull. As the boat accelerates, the ama will cause more and more drag because it can't easily reach the same speed that the main hull is capable of.
Flatter, wider sections aft might fix that.
* this is based on my understanding that your main hull is 16' LOA.

 

Correct Doug, but the amas are supposed to stay out of the water as much as possible, so just skimming the surface. I could widen the profile aft, that probably wouldn't hurt anything.

 

It does need to maintain the shallow V section aft to be a planing hull, the increasing aft deadrise now wouldn't let it plane. Compromise is the word, ride can be on the table if it does what you want.