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Thanks tlouth7! At this point, my rig planning is based on spars I already own. The Wharram wingsail can be pretty efficient. A beamier plan helps to set the shrouds out at a greater angle, since there are no spreaders. Because of the wingsail, the forestay goes to the masthead. So probably a...

Oops, I bet you meant individual hulls. Kayak seats are typically 20". Give a couple more inches on each side and we get L/B = 20'/2' = 10. The amas beam across the deck is about 15". Waterline beam when half submerged about 10"? So L/B = 240"/10" = 24?

Not having planned it to specific dimensions, using the above-stated figures of 21' LOA and 17' beam gives L/B somewhere in the 0.80 to 0.85 range, depending on the length of the stem above waterline.

Thanks Rumars! Here is a thread discussing bowsprits. I have not yet read all pages. What's So Bad About the Bowsprit ? - Cruisers & Sailing Forums https://www.cruisersforum.com/forums/f47/whats-so-bad-about-the-bowsprit-48782.html

Typical full width bevel scarf. Probably no bowsprit if the hull length carries the sailplan. But I don't know. A bit of searching found no general discussion of sprit vs. hull, hence this thread. Mike Waters recently put up a good essay on multihull beam...

No sketches yet. All three hulls about 21' (to scarf from three sheets of plywood) and a beam about 17'. Borrowing a lot of design concepts from Mike Waters W17. Narrowest possible main hull that permits forward-facing seating with foot steering, but sailing from trampolines an option...

For my plan, I was wondering about that. But why a bowsprit at all if the hull is long enough? And I am considering a furling tube for a spinnaker, so I wonder if that might be better with no bowsprit?

Might we summarize the considerations in choosing between adding/lengthening a bowsprit versus building a longer hull? This is for original design more than adaptation of an existing one. As a more particular question, for me this is for a fast nonfoiling beach trimaran that often will sail...

Those forces are substantial indeed, though the windward hull is essentially moot in this thread. Unless you have crew out to windward, its righting force is limited by its weight, while the leeward ama's force is the greater weight of the water it displaces. Otherwise amas would be prone to...

It is an impertinent question in the context of my statement. To the degree the wind blows on the sail, the ama is forced deeper into the water until the buoyant force equals that of the sail. Of course all the details of how a trimaran works are far more complicated. None of us need our noses...

I quit reading as soon as you asked where the downward force on an ama comes from.

For a car, the road is static. Your description of the leeward ama at different times as it crosses a wave is excellent, thank you. I can see how Adrenaline's swain might be helpful. I searched for more about Adrenaline, but found little.

If the engineers here can see their way to help neophytes like me through the pitfalls of terminology, I appreciate it. I hope I am not misinterpreting or misunderstanding the concept of buoyancy. As I understand it, as the ama of a trimaran is subject to more downward force, it goes deeper into...

I wonder if the concept is quite different on a proa, helping the ama to work in both directions?

Well, I don't think we are talking about water in its solid state, when it does flex. If we need to be picky about semantics: At displacement hull speeds, the water moves out of the way of all hulls (i.e. is displaced), in particular the leeward ama. My point being the boat structure does not...

Discussions like this are fun exercises. I do think this one is fundamentally flawed because it has ignored a factor that I don't see mentioned. A boat does not need to flex, because the water does ... unless you are designing an icebox or a high-speed planing hull. The windward ama on a...

Sharpii2: I agree with your assessment, thanks. I think a long shallow profile is the way to go, if I make a tri with all hulls quite narrow. What I lose in pointing ability might be made up in VMG, especially when weed dumping time is a factor.

The Q: Current monos are an O'day 25 with a centerboard within a short keel, and an off-brand 17 with a swing keel. Both with swing rudders. The O'day is limited to always sailing board up. Tried it with the board down and it gathered so much weeds around the pendant that it was impossible to...

I hope readers might advise me. Sailing monos on our increasingly weedy lake is becoming a hassle, and moving me closer to building a trimaran. Hopefully some readers have had positive experiences. What features, and examples of tris with them, would be best where weeds are frequent? Hull...

For sale again, SailboatListings.com ad dated 29 September 2019. Both of the photos above are in the current ad, so none probably are current photos. Correction, it has a Facebook page so some pics seem current. Needs at least sails and a good cleaning, but it gets out and about. Trimaran...