Small Surface Piercing Trimaran Foiler

Here is a project that is off to a good start:
http://www.youtube.com/watch?v=p1ADR-Dft6w#t=169

 

Not exactly a stable ride given how deep it buries itself at 55 secs into the video

Meh

 

Come on BB,

You bash Doug for not getting his project on the water.

Then when someone does put something new on the water you jump in with a negative post.

Given the probable number of sailing hours on what looks like a brand new from scratch design, I did not think it looked bad at all. Yes there looks to be room for improvement, but there also seemed to be some interesting potential.

 

What I find most interesting is some of the text that goes with the video:

"Garage project - prototype hydrofoil trimaran. Sailing in the Marlborough Sounds, New Zealand during January 2014. These are the first trials up on the hydrofoils in light and puffy winds. Great fun, easy to sail and more stable than expected. Still needs a few mods to improve performance. Completely disassembles for transporting on (and in) a car! Takes about 30 minutes to assemble."

and

"Yes, pitch-poling was always going to be an issue, but I was very pleased that I have enough buoyancy in the bow to prevent a complete pitch-pole after the nose dive seen in the video - in this instance anyway. It's the same nose dive in both cases in the video and I kept it in for interest. I think I have a bit much power in the mainsail so that, when a gust comes along or the power comes on from low speed I can feel it dig in. As long as I bring the power on gradually to let the foils take effect as the boat speeds up then all is well. I also need to change the angle of attack of the rudder foil so that the front foils get more lift."

 

Paul, if you haven't already check out the video in post 141 of the Hydroptere thread-it has a brief shot of an 18' Hydroptere proto.....

 

I had noted that video back not long after it came out I think.

Early foiling efforts included more than a few with a similar basic configuration that were not impressive enough to prompt more widespread use. I seem to recall that Dr. Bradfield did something similar before moving on to flaps and wands.

However, the big improvements in materials, rigs and the improvements in foil design knowledge probably make it worth trying the layout again. Also, I am thinking that some early efforts really wanted record setting kind of stuff where now the goal is probably more along the lines of a "regular guy's hot-rod" small boat.

 

Well then that's my bad.... I didn't read the text, just looked at the vid, and the uBoat Commander at 55 secs looked pretty scary

 

That nose dive was not as bad as many Hobie 16 "incidents".
I'm assuming that the main beam is not actually movable as it looks in a few of the segments. Probably due to the camera optics?

Its all very well to have fixed foils to minimize controls, but a small boat like this ought to have some manually controlled way to avoid the nose dive.
Any suggestions on the best way?

Bradfields and others use of a wand is another level - automatic control.

 

--------------
The camera sure did produce a "scissor effect" that I initially thought was movement like Randy Smythes boat.
It appears to me that the main foils are attached to the amas and a couple of times it was apparent that the amas were rocking back and forth-that may have been the cause of the pitch down. Fairly simple correction in any case. Doug Halsey's 18' foiler with "V" foiler is quite stable-there is nothing inherent in surface piercing foils that would cause this sort of pitch instability.
Surface piercing foils should be very stable and they are very simple-perhaps the simplest form of foiler with automatic altitude control and no moving parts.
One problem experienced on some surface piercers is ventilation of the main foils* and thats why you see an array of "fences" on Hydropteres main foils. Ventilation could be part of the cause.
* because the load is carried very close to the surface.

 

Hi Everyone

I thought I should chip in as its my boat (Kotuku). The aim on the project was to build a foiler that was easy to sail and easy to transport - keep it simple.

The nose dive was the only significant incident in 4 days sailing and was partially due to poor sailing on my part. Once it dug in I didn't let go of the mains sheet for a while so it went down. But I didn't completely pitch pole so that was in some ways a success. Where I was sailing is a challenging spot. On my last day of sailing (the cloudy day and the day of the nose dive) the wind came in gusts from the norwest, then the east, I was becalmed for a while and then a southerley all in the space of one hour. Gusts would come from opposing directions!!! I figure if I can sail a foiler there, I can sail it anywhere.

BTW, the amas are on pivots so do not affect the foil pitch. I also have one fence on the foils, but I'm not sure how well it works yet.

There are still loads of improvements needed and I appreciate your comments. I have a small flap on the rudder foil, but I cant adjust it easily. I'm still working out the best adjustment for it to have the yacht flying at the best angle. I should make it adjustable while sailing!!! The rudder and rudder foil needs replacing (long story) and I think I have too much power in the main sail too.

I like the "regular guy's hot-rod" small boat. In some ways this sums up the project.

Cheers,
Craig

 

Craig, welcome to the forum and thanks for the info! Congratulations on a great job-I think you've got a cool little boat there that will only get better.
Best of luck!

 

Ah, these NZ Nelson boys, eh, crazy as loons? I'm a Nelson boy.
Great stuff, Craig - your nose dive was minor; you should have been on board Flash Harry in high wind and waves at some times - saved only by the T rudder.
Here, with inverted V main foils, beating/pinching to weather in some good breeze.
With Sid, so far, have not experienced the crash dive but the main foils are curved with a substantial amount of vertical lift, seems more stable than the angled 45's.

 

Hi Craig,

I'm really glad you decided to join the list & I'm looking forward to comparing notes with you. If there's anything about my Broomstick that you think would help you with Kotuku, just ask.

 

Craig, here is a link to some info on Doug's Broomstick foiler:
http://www.boatdesign.net/forums/hy...ler-design-foil-assist-full-flying-40894.html post 15
This has been here awhile so Doug may need to update it.

 

Thanks for joining in.

I noted you were responding to comments on U Tube and was going to invite you to the forum, but did not get around to it.

Congrats on the progress thus far. I see lots of potential for fun.