Yes, I know the aerodynamics thread is under planes but the rc plane group are much more in tune to aerodynamics to keep the planes in the air whereas the rc boats float.

Does anyone have a good source for learning about Hydroplane aerodynamics? Is this 'ground effects' aerodynamics?

The 'picklefork' hydroplane design even has a canard in front. Is there a source for canard aerodynamics?

The " safe window of flying a prop driven boat is very small ".

Driver egos and changing water conditions in competition, removes all the carefull work done by everyone and causes crashes.

Aggressive people can not stay in the " envelope ".

That's what I would like to do .... "Fly a prop-driven boat" .... especially during a straightaway time trial away from the aggression. Maybe a light weight finely-tuned time trial hydroplane and then another that has the carbon fiber and kevlar to handle the aggression.

The short answer is that canards are destabilizing. Not that a vehicle is unstable with a canard, it's that all other things being unchanged, the vehicle will become less stable. To add a canard, the CG must move forward to maintain the same stability.

However, if you were to combine a moving canard (hinged) with a heading hold gyro, you could have a system where you could tune the pitch attitude of the boat with "elevator" and the gyro would react to any waves or turbulence that would try to lift the nose and flip the boat, and keep the bow rock solid. That's artificial stability, same thing used in fly-by-wire fighters... Just might be a challenge getting the gain set right. Worth a shot.

Thanks - that was the same direction that I was thinking about but didn't want to 'lead' the replies. Since the 'lobster tail' hydroplane uses a single canard between the two sponsons instead of two canards on each side of a fuselage, do you have any thoughts on whether the entire wing should be adjustable by the heading hold gyro, the wing should be split in the center and controlled by two gyros (maintain roll also) or if smaller right and left 'elevators' on the rear of a single canard wing makes since.

I realize that this is mainly guess work without some trial work but it still might help in the initial direction to take and reduce the number of versions to try! I am planning on using a homemade wind tunnel to do the initial experimenting with to reduce the occurrences of catastrophic 'flipping' incidents.

Thanks again for any educated guesses.

AAARrrrrrrgggghhhh!. I had a nice post wiped out, because I started it this morning, then finished it after lunch. When I went to post it, I got a "TIMEOUT" error, after which I had lost all the text I had written.

So, anyway. My simple idea was to put all-flying, swept canards on the outboard gunwales of the sponsons. The "elevator" channel would be mixed with about 0-10 deg of control range available thru a knob on the transmitter. Each canard sized to be about 1/4 - 1/3 the area of the "stabilizer"

The ATV for the "elevator channel would actually allow about 20 deg of down, so the gyro could command that much if needed. If you need more than that to keep control, the battle has probably been lost anyway. Actually, even that much is likely overkill.

Basically, what I'm saying is there would be a knob on your transmitter that would command a nose-up amount from the canard from flat to 10 deg nose up, then the gyro would have the authority to go as much as 20 deg nose down to keep the boat flat.

It sure would be cool to see a boat like this jump off a wake or ?? and just maintain a stable slight nose up attitude until it landed back in the water.

Actually, one thing that would be kind of fun would be to put canards on a hydro foam and manage them with a headin-hold gyro. Just replace the elevon function with a couple of canards. Gotta look at that little sucker tonite.

Aerodynamics in this case is good up to the point of avoiding a positive lifting issue but I think you'll find that the surfaces and their effects are very small compared to the kicking about that occurs due to the roughness of the water. And AFAIK there's seldom an issue when it's glass smooth. Not so?

Where you could gain is to provide for a slight downforce that could be dialed in for rougher conditions to aid in preventing the hydro being kicked up by ramping off a bit of chop and then "catching" the air and causing a flip. But I would think that the only lift up that you want is the actual spots that are touching the water. Otherwise disaster is only a blink away.

If you're looking at actually flying millimeters above the water rather than hydroplaning in contact then you're looking for WIG or Wing In Ground effect. That's a WHOLE other issue and has nothing whatsoever to do with classic or even the picklefork outrigger hydros that are commonly used in boat racing. A WIG craft is an actuall airplane that is optimised to operate at it's best very close to the surface but is capable of flying upwards for popups and for turning when needed. They have a boat hull and wing tip sponsons but that's only for takeoffs and landings and while operating they are airborne. THey require all the typical and proper aircraft controls and aircraft balance point.

But for racing I doubt if a WIG would be considered legal since technically it's not a boat. It also uses aircraft engines and not a water prop.

Do a Google on the words "wing ground effect" and it'll come back with a lot of reading for ya.

Johng and Bmatthews - Your thoughts are quite thought-provoking. My thought process is this - The impact to the hydroplane attitude is most affected by its reaction to the water (because of density) so tuning its water elements is done first in calm air and smooth water. BUT, once it hits a wave or a gust of wind (or even when it turns into the wind - since I race Ovals) - both of which are bad if you have it tuned 'on the edge' THEN my only control is air-related because it is the air that creates the flip. The flips are faster than human reaction time (at least in R/C) so it will have to be automated.

I will do some research on WIG. You are correct in that the hydroplane is required to be water prop driven.

If by "swept canards on the outboard gunwales of the sponsons" you mean something that makes the hydroplane wider, overall, that would violate rules since I am at maximum width. I like the idea of having a manual control to give it a "nose-up" attitude and then lightning-fast gyro-controlled control to override the manual control for a pre-flipping event. I also agree that once the hydroplane gets a nose-up attitude of a few degrees "the battle has probably been lost anyway" since the whole boat transforms into a big wing with an aggressive positive attack angle for the flip.

Thanks to everyone.

Hey Bruce,

I don't know if you've seen these things go, but they are already tuned to essentially fly with only the prop in the water, and the hulls only kissing or ticking off the water. So "disaster is only a blink away" already. In what other surface based sport (FS) do the drivers wear parachutes?

So the addition of a tunable gyro stabilized system could only make things better. The lift on the canards would tune the overall lift on the hull of the boat, maximizing speed. But any disturbance, water or air based, could be damped by a gyro with sufficient gain. Even if a wave is responsible for kicking the boat into the air, it is an aerodynamic problem once that initial evant has taken place. So, a gyro-canard could be quite usefull. It could even be tuned to lower the nose with application of rudder do provide more hull in the water to effect the turn. No need for it to be tuned with a downforce for normal operation tho.

If they have to be inboard to satisfy rules, so be it.

This might sound a little strange but I have decided to build a "portable test bench" that will strap onto the top of my van. It will allow the hydroplanes to be supported by three vertical rods (3 point hydroplane - rear of each sponson and center rear of transom). By having the rods slide through a 3' x 4' ground effect plate (plywood) mounted on bearings & springs to measure positive and negative lift and having the plate mounted on bearing slides and springs (to measure drag), I should be able to have linear sensors on the plate and the 3 rods attached to a data recorder and measure everything (including effects of any canard (with and without gyro).

Although probably generating some stares on rural Texas highways, this "portable wind tunnel" should allow me to initially set some things like size of canard wing & control surfaces, speed & gain of gyro, etc. without destroying expensive hydroplane hulls and engines which sometimes happens with these high-speed flips. Final tuning will, of course, have to be done on the water.

I already have one of my hydroplanes rigged with sensors and a eagletree data-recorder to record mph, engine rpm, engine head temperature, exhaust gas temperature (EGT), servo positions, and 2-directional g-forces.

What do you think - Crazy??

I found this in a white paper on WIG craft - it seems to go along with our thoughts:

[link=http://www.dsto.defence.gov.au/publications/2058/DSTO-GD-0201.pdf]Australia Department of Defense[/link]

"2.5.2 Pitch Stability
Pitch stability is a measure of the response of the craft to changes in pitch. With a disturbance in pitch the response of the craft can be either stable or unstable. Unstable behaviour results in increasing pitch amplitudes, while stable behaviour results in the craft returning to a pitch angle.
The control of WIG craft pitch stability has been one of the larger hurdles in WIG craft
development. The problem is due to a change in the pitch stability with height. The result is the necessity for a large amount of control power to maintain trim. Early designs and
theoretical studies have shown that the greatest problem is damping the long period (phugoid) oscillations. DSTO-GD-020114
Designs have often shown stability in some regions above the surface and instability in other regions. Pitch instability causes ride discomfort and is a possible hazard to the craft. As the pitch stability is linked to the vertical height stability, large excursions could cause contact with the surface, resulting in high structural loads or failure.
It is now considered [3] that this problem can be overcome using modern control methods and the current understanding of WIG craft aerodynamics. The challenge in the design phase is to provide sufficient control power for stability to be maintained throughout the vertical height envelope."