Taking Off the Training Wheels (Sailing a Hydrofoil Trimaran Without the Amas)

[Doug Halsey]

In an earlier thread (Ama Hull Shapes - 5/29/08), Gary Baigent made the comment

If I had more courage I would build a foiler without any floats at all, just large foils. Whoops!!!

This inspired me to try to sail my hydrofoil trimaran (Broomstick) without its amas (floats). In my case, I didn't have to build or modify anything; the amas that I use in foiling mode simply attach to the crossbeams with bungee cord.

My plan was to go out on a fairly moderate day, first with the amas attached to make sure everything was set right & working OK, then come ashore & ditch the amas. This plan quickly fell apart when I ran into a giant kelp bed (or some kind of weed anyway) & had to spend several minutes in all sorts of odd positions to remove all the weed. Thank goodness for the amas, that time!

Next time out (6/11/08), I launched farther down the beach & was more aware of where the patches of weeds were lurking. I sailed for a few minutes with the amas, then got up my nerve to take them off.

There were some awkward moments (Photo #1), but as soon as the boat had any forward motion at all, it was surprisingly easy to sail. In one sense, it was much easier to sail. When it's not up on the foils, Broomstick's crossbeams don't have a lot of clearance & it only takes a small amount of heel for them to to hit the water, causing tremendous drag & risk of a slow-motion capsize. Without the amas, it seemed to be much easier to keep this from happening. Apparently, the extra drag of the leeward ama when it is deeply immersed is a more powerful factor than the extra righting moment that it provides.

The boat also seemed to perform better & felt more lively. For the first time ever, I was able to take off while close-hauled at about 50 degrees. (Previously, I might have flown that close to the wind, but I did it by reaching off first until foilbourne). I would have expected a smaller improvement, since I'm only eliminating 20 lbs of weight (out of about 200 total, not counting my weight) and also a small amount of windage. Obviously, I can't quantify this very well, but I was very pleased with the performance. See Photos #2 & #3. Top speed for the day was 20.2 knots, in a fairly moderate wind (low to middle teens).

I did let my guard down one time & capsized, for only the second time ever ( Photo #4). That didn't really dampen my spirits much, since I was able to right it without help. I definitely plan to sail without the amas much more.

One final question - If I'm sailing without amas, can I still call it a hydrofoil trimaran?

Note : All photos were taken by Terry Curtiss.

 

[Chris Ostlind]

Who was the idiot who said we get more timid as we grow older?

Very interesting development and now begging for even more design mods, such as a bit more aka clearance and that will most likely necessitate longer foils. Sorry I mentioned it.

This success probably confines the boat to warm water/weather sailing, as it will be no fun at all trying to right that puppy in truly cold water. Still, it's probably a hoot to take the risks with the boat and make these discoveries.

Does the gustiness potential there make for a higher premium on athleticism while trying to keep her upright at the start?

Nice stuff, Doug.

Hey, I'll be out in SoCal for two weeks starting next Wednesday. Maybe I can swing by your place to check out your boat?

My regular email is: Chris at Wedgesail dot com drop me a line with your number and I'll shoot you a call.

Chris

 

[Doug Lord]

Congratulations,Doug! Very cool.

 

[Doug Halsey]

Chris & Doug:

Thanks for the interest & the compliments. This project has probably been the most fun of any I've been involved in, and it's gratifying when someone else takes notice.

Chris: Addressing each of your points:

Who was the idiot who said we get more timid as we grow older?

You must have found out that I used to race Moths in the 1960's.

Very interesting development and now begging for even more design mods, such as a bit more aka clearance and that will most likely necessitate longer foils. Sorry I mentioned it.

Longer foils would definitely give me more headaches! One of my biggest problems has been keeping the foil brackets attached to the crossbeams. Sometimes I think that the best solution might be to run the foils through wells in the amas (like on Gary Baigent's Flash Harry) to give them something more substantial to bear against. Of course, then I couldn't use vee-foils & I couldn't sail without the amas.

This success probably confines the boat to warm water/weather sailing, as it will be no fun at all trying to right that puppy in truly cold water.

Since it only takes a minute or two to attach or remove the amas, I can have them on the beach & decide at the last instant whether the conditions are such that I feel like I need them. For now, I'll probably use the amas if the wind is over about 18-20 knots, or if I'll be measuring the wind, taking many notes, etc. As I get more used to it, I'll no doubt sail more often without them.

Also, this capsize happened in such slow motion that I never fell into the water. See the attached photo. The other time I capsized was in the middle of November, 2005 & it was plenty cold (at least by California standards). Still, I usually only sail from May through October.

Does the gustiness potential there make for a higher premium on athleticism while trying to keep her upright at the start?

I don't consider this to be very athletic - not nearly as much as the 1960-era Moths or the 1970-era Windsurfers I used to sail (even factoring in my ages, then & now).

Hey, I'll be out in SoCal for two weeks starting next Wednesday. Maybe I can swing by your place to check out your boat?

I'd love to have you see (& possibly sail) the boat. I'll be emailing you shortly to try to sort out how, when & where to meet.

 

[Gary Baigent]

brave man and true foiler

Fanbloodytastic Doug, you're a better man than I am Gungha Din.
Actually the British 1988 AC challenge Blue Arrow, although apparently it tipped in deep on a sea delivery trip, (I heard a rumour that it actually inverted, anyone have more knowledge?) had an interesting float/foil configuration: the foil thickened as it rose above the (usual?) waterline, a bit like an upside down bottle - crude description but you get the image, and in flat water the boat looked fast and stable in photographs to me. Blue Arrow was designed by a group with Ed Dubois, Adrian Thompson, Barry Noble and other British hotshots - definitely breaking new ground. Hey you blokes, tell us more about it - doesn't matter that it was considered a dismal failure, there are plenty of us out here who want to know.
Another pioneer was kiwi Noel Fuller who had triangular float foils that thickened above the water on his 14 foot Sabrina - those foils worked well, didn't bury but Sabrina was not a good windward performer - but reached along impressively enveloped in spray with the doughty bearded designer hidden from sight by a curtain of white.

 

[Doug Lord]

Blue Arrow

Heres more:
http://www.policesailing.org.uk/reports/nimss/americas.htm

 

[Doug Halsey]

Gary & Doug:

Thanks for bringing Blue Arrow to my attention. How could I have been unaware of such a neat boat?

There have actually been quite a few foilers that were essentially trimarans without amas (I repeat, can we still call them trimarans?). A well-known one was Don Nigg's Flying Fish (featured in some of the old hydrofoil books).

One of my favorites was Gary Seaman's flying drainpipe (see photo). This boat won a speed-trial at Hurricane Gulch, CA in about 1972, beating the notable D-Cat Beowulf. The wind was fairly light & the winning speed was only in the high teens. As I recall, he really struggled in stronger winds. It must have been a real bear to sail (unlike Broomstick, which is actually quite easy, even without the amas).

 

[Doug Lord]

Foilers

Gary & Doug:

I repeat, can we still call them trimarans?.

----------------
Interesting question-one that was wrestled with in the Moth class. They finally decided(rightly or wrongly) that foils mounted off the center line were a "multihull" configuration. If we go with that definition then what about Kotaro Horiuchi's boat? It seems that maybe we'd have to make a judgement about the size of the buoyancy at the end of the "racks"?
Kotaro's boat is "obviously" a trimaran but the Bladerider "obviously" has buoyancy pods.

 

[Doug Lord]

Blue Arrow-more pix

Check these out: (from scuttlebutt via SA)

 

[ancient kayaker]

Interesting to note your experience without the amas, Doug (H). My first venture into sailing, apart from the odd rented or borrowed boat, was a sailing canoe with a single home-designed and built ama. I was careful to keep the ama wet at all times assuming that was the thing to do, and was consistently disappointed with the pedestrian performance.

Then one day I found myself tearing along in a modest breeze. I looked around to better judge the speed and Lo! There was the ama a foot out of the water! It was my introduction into just how much drag a short and badly-designed displacement ama could create.

No, I haven't tried foiling yet, but ...

 

[Gary Baigent]

Well, as I posted before Doug, you're a better man than i am - however recently I took Flash Harry out in an informal (but as usual serious) race with winds gusts to over 25 knots and good sized, solid waves running, full sail and wing on Harry (can't reef, no points .... will be changed) and the ******* buried foil and float and half the main beam, never happened before. Also the loads were so high one of the foils started spitting its carbon off during continuous flying, then crashing, didn't break but looked very secondhand when removed later. So making a few changes on Harry, going to inverted Y foils to reduce the bloody crashing, keeping the floats, sorry, empirical knowledge overpowering pitiful attempts at valour, full width main sheet track (to better control a completely overpowered sail and rig) and various other improvements.

 

[Doug Lord]

Gary, what do you think causes the crashing?

 

[Gary Baigent]

Hi Doug, large waves and Harry flying off the tops of them, foils completely out of the water, or almost clear, ventilation, roaring, crash, immediately leaps up again, accelerates tremendously, crash, enormous deceleration, repeat, fun but you just know if you could stay flying ... lot better fun. Foils are surface piercers, (like small Hydroptere) inverted T's or Y's are better IMO - I've fitted them to G. Marx and I really like them, greater lift, less ventilation and require less surface area too. I had to reduce them because I had too much lift and the platform (which has some dihedral) would begin to rock - but now it is steady. In flatter water the originals are fine too, just larger waves cause the problems.

 

[Doug Lord]

Gary, thanks for the info! Good luck in the fix...

 

[Gary Baigent]

Forgot to mention - Inverted T rudder saved my bacon, kept stern down, otherwise I'd have gone helicoptering horizon sudden climb, pause, silence, blue wave swept sea suddenly above head, lots of bubbles.