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

Is that the good old "down the mine" syndrome or the standard involuntary highspeed baptism?

 

Why don't you just strap the amas on TOP of the crossbeams? For that matter, some sort of inflatable float would do as well.

That way you can't entirely capsize if you screw up, but they're out of the way otherwise.

 

NF3 video

Heres a video of Dr. Bradfields NF3 foiling with no amas(to speak of):

http://www.youtube.com/watch?v=oRUewjLbi_I&feature=fvsr

 

The video of NF3 with no ama's was a very early one, when she was first built. That system proved to be very poor, and unmanagable in many conditions. Acutally we broke the main crossbeam by burying the outboard end, after a ventilation crash.

Some long cylinder type floats were tried next, but they were a flop.
We later refitted a a pair of surfboards to the ends of the cross beams, which worked very well. They had just enough bouyancy to prevent burying, and skimmed smoothly in calm water.

The trick is to keep the dihedral of the cross beam high enough, so that the boat does not rest on both ama floats at the same time. This allows you to sail with both ama's clear of the water, when hullborne, and keep the windward foil out of the water, when it is retracted.

Nf3 liked to be sailed with the leeward ama about 6" off the water, so the foil hinge was above the waters surface.

Having sailed without amas, I cant recommend it. It is too easy to bury the leeward crossbeam, when taking off. Falling to windward in a lull is also an issue. Also, the dreaded ventilation crash can become much more dangerous, with no bouyancy on the tips.

Hydrofoils are touchy enough to sail, that they really need a little extra help from amas, just to remove that issue from the mind of the poor devil sailing the thing.

 

Hi Busman,

I actually saw this boat on its trailer when Tom and Sam were first selling the converted Hobie16 foiler. My friend Hollis actually bought one, then traded it in on a new Rave.

 

I actually bought NF3 in 1990 from Sam Bradfield. I sailed/raced it for 5 years or so, and then donated it to Chapmans School. Some one else bought it, and then abandonded it later on. Tom and Sam were able to get it back. You probably saw it after all that happened, as that was when the Hobie 16 conversions were going on.

I sailed the Hobie conversion a few times, and thought it was pretty neat,for a cheap little hyrofoil conversion !! Also it was a heck of a lot easier to rig than NF3(that wing was a real SOB).

I thought about buying one of the Hobie conversions, but by that time, I was Hydrofoiled out, after 8 years and 6 different foiler boats. So I bought a gaff rigged catboat instead!!

 

I talked to Randy Smyth about this boat 3 weeks ago- he sailed it in the 18 M2
Nationals with its J-foils.
Too bad it wasn't built light.

 

Yes, Randy did sail with us a number of times on Nf3 and some of the later foilers we built (Hydrosail 21, Mosquito, etc). Alot of good sailors came to try out the various boats, to see what foilers were about. You have to remeber, this was in the late 80's, and we were about the only foil nuts around, at the time. Some left very impressed, others indifferent, which sort of mirrors the public sentiment about foilers in general.

At one point we has 6 different foilers at our site, so we had alot of variety to play with!!

NF3 was not really too heavy a boat, her big hinderance was the J-foils were not built for flat out speed record attemps. They were designed for "round the Bouys" racing. As such, they were profiled to produce better speeds in semi-hull bourn mode. The theoretical top end of these foils was 35 knots, but in practice we found that they could be pushed well over 45knots, by reducing the angle of attack, using the rudder foil's trim tab, and decreasing the horizontal lift angle of the J-foils. We had alot of runs in the high 40's in those days, which was pretty good.

Our later boat, the Hydrosail 21 used one of Randy Smyth's old World 1000 catamaran rig. That boat was a really nice steady performer, and did well in races. It was alot harder boat to sail than NF3, as the crewman had to be in 10 places at one time, as well as being windard ballast!

I am sure NF3 could have easily been a world record boat, with the right foils.
The rigid wing sail developed far more power than the foil system was able to dissapate. As a result, we had to sail her on the conservative side, or she would break foils, crossbeams, etc.

I believe I have the honor of being the first person to pitchpole a sailing hydrofoil, at speed. We were always under the impression that the rudder foil would prevent a pitchpole, when it went to a negative angle of attack. I proved this to be false, by pitchpoling NF3 in clam water with a 15knt wind.
This was not a fluke, as I had it happen on 3 different occasions, while I owned NF3.

 

hey Busman, that is very, very interesting. I remember looking at photographs of NF3, with the full wing and J foils, and being very impressed - you blokes were pushing the boundaries - but what I didn't know, was that you achieved those very high speeds, although I knew the boat had to be fast. On the point of pitchpoling, I've buried Flash Harry many times, and once recently right over the main beam, but the inverted T rudder saved my bacon everytime. What did you do, in only 15 knots wind, to achieve this momentous record?

 

NF3 could really develop some serious power in 12-15 knots of wind. With the camber induced wing, set with a fair amount of camber, and a slight twist off the top, she could really move in medium winds. As I said, the wing made alot more power than the boat could handle. We could get 2.5x wind speed under the right conditions.

My first pitchpole was the result of a ventilation crash, when I was hotdogging on a lake in West Palm Beach, one day. The foils ventilated, and the bow dropped pretty fast, as I had the j-foils set in fairly vertical position (less lift, more speed). Since the foils were more vertical, the recovery of lift was slow, and allowed the bow to get under water . Nf3's bow was very short,only3ft in front of the crossbeam.

Once the bow submerged, the stern kept going up and over, and catapluted me out of the cockpit, into the wing sail. I came out of the wing sail cut to ribbons by all the carbon fiber and epoxy !!!

I was able to duplicate this feat, 2 more times over the years, but with a cockpit seatbelt, I stayed out of the wing sail....a big plus!!

I have a beauty of a scar down my right leg, from the first pitchpole, which is trophy from that ,ahem, momentous event.

We learned alot of lessons the hard way, that hopefully helped the breed evolve.

I do find it interesting that Hydro Petre looks like a giant version of the Hydrosail 21, even the design of the crossbeam and the foil control system.
I would have thought that 20 years would have brought more changes than it did!!

Thanks
Don Carson

 

Don, very interesting stuff-thanks! Have you seen the new Osprey? Seems like it will be a sort of carbon Rave... Last I talked to Dr. Sam (2 months ago?)
he said they were about "20% along".

 

I have not seen the Osprey yet, but knowing Sam, it will be very interesting and well thought out. He has been at it longer than anyone else, truly the father of the modern sailing hydrofoil!

It was the high point of my sailing life to work for him, and be a part in building 4 hydrofoil boats. We had alot of fun,even when everything fell apart! Heck, in one race,we finished in 1st place,foilborne, and settled down on the hull after crossing the line, and promptly sank!!! We had split the hull stem to stern, smashing a wavetop on the final leg of the race. Since we were on the foils, we did not know about it till the race was over.
Fun times....

 

Don, could you post some photographs of that important, historical time. cheers.

 

I have to look around for my old photos of my time with Dr. Bradfield. I know I have complete building photos of the Hydrosail 21, from the bare hull to sailing. Also, alot of photos of NF3 under sail. I think there are some shots of Mosquito (an 18sq Nacra hull based foiler), and a few other boats that were around at the time. It was a very intersting time for me, as I felt like we were really pushing the envelope of performance.

 

Pitchpoling

Don :

Like Gary, I've always been tremendously impressed by NF3. Not only was it a technological marvel, but it's possibly the most beautiful foiler I've ever seen photos of.

I wonder if you have any numbers for the depth of the aft foil, compared to the main foils ? One mistake I made in designing Broomstick's foils was to put the aft foil too shallow. (In my defence, I didn't really "design" it that way, I simply slapped a foil on the bottom of an existing kick-up rudder. My real error was in using the same aft-foil depth when I made a second, more substantial rudder.)

When the boat is flying on the tips of its foils, the aft foil can get too close to the surface & possibly stall or otherwise misbehave. I've never pitchpoled, but I've seen some pretty wierd effects (like the fountain in my wake in the attached photo), & I firmly believe that this is a major factor limiting Broomstick's top speed so far.