Just to let everyone know I'm still working on my boat

Consulting jobs have kept me away from home, but more there's been alot of progress this last week!

All three of the 18.5ft by 3 ft beams are coming together.

The three hulls, the kayak is a Pax 19.5

what it should look like when I'm done.



More photos are my website:

Or you can go there directly here:

13 replies:

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RE: Swiftwood


RE: Swiftwood


This forum doesn't use embedded tags for images and stuff. You need to use the images button at the bottom of the text box. It also truncates images to 500 pixels max width.

A hydrofoil trimaran - neat!




RE: Swiftwood

Great news, Brian.  Keep at it; we're all waiting to see her fly.

I'm curious.  What speed will be needed to lift the hulls completely out of the water (or do they stay partly in the water at high speed?)

RE: Swiftwood

Ah, I was wondering what I did wrong thanks.

It's more of a a foil stabilized boat, I want to keep them just kissing the water.

RE: Swiftwood

Could you explain in more detail about the position of the windward and leeward hulls and foils while underway, relative to the water?  I'm not sure I interpreted your answer correctly.  As I read it, you want both hulls just kissing the water when underway (and thus, all three foils completely submerged).

RE: Swiftwood

It will have two mods of running,

Foils up, for shallow water.


And foils down for running in deep water


I've got a real long thread on the Woodenboat forum about it:


RE: Swiftwood

Thanks, Brian, that clarifies it.  The pictures show the hulls completely out of the water in the deep water case, which is what I wasn't sure of about your particular design.

What speed will be needed to get all hulls free of the water?


Looks like a real thrill of a ride!


  It will be interesting to see how your novel idea (to me anyway)  of a gaff- schooner rig will work out.  I've read about this subject with interest for many years, and must admit that I don't recall this more traditional rig being used with foils.  Most of the folks seem to go with the philosophy of those in your photos, a modern high-performance rig.  High aspect-ratio Bermuda sloop rig, for example. 


RE: Swiftwood

I should get "foil born" at about 10kts.

You can get them to go sooner, but that means more drag which would reduce speed on the top end.

Here's a video of a Windrider Rave


RE: Swiftwood

Thanks, the construction details are very informative, should I ever decide to build something so exotic!


Again, just curious: what surface area did you decide on for the foils, and what all-up weight for the boat?  The reason I'm wondering is that I recently read a post that gave a "rule of thumb" estimate for C(L) for small craft hydrofoils, of 0.25 to 0.4 .  I am wondering if your experience confirms the validity of rule of thumb or not. 

RE: Swiftwood

I've got to dig up the NACA foil I picked.

I'm still trying to decide whether or not use to a controller much like the RAVE with single foils or go with the ladder type. The ladder types are self regulating, and easier to design, but the have a lot more drag.

Unfortunately it's getting [i]cold[/i] at night.
Too cold for the epoxy to cure.
So unless it warms back up, I may have to put the project to bed until spring :(

RE: Swiftwood

Is this thing done already... this has been going on since the 90's!



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