Electric Foiler(or foil assist)

I'm very interested in this avenue of design particularly after I discovered that there MAY be a major breakthru in stored energy(see thread referenced below). I'm interested in a minimal two person boat(350lb crew) for use on the intercoastal, Banana River and various lagoons in Florida. I'm thinking full flying or using the foils to enhance stability and/or to reduce wetted surface.
Rick Willoughby is inspirational on low power boats:
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"The question was on foiling not exclusively sailing. There are many avenues being explored. Some examples:
http://www.airchair.com/
http://www.foilkayak.com/
http://www.extremekites.com.au/forum...ead.php?t=2990
http://www.youtube.com/watch?v=g3AV1LJwQus
http://www.youtube.com/watch?v=TRd5qMpEUsg

Some have not got past the curiosity stage but there are efforts to market them and some have developed a lot of interest if not yet sales to match. These things have great pose value and that sells. Look at the impracticality of a sports car but there are still plenty on the market.

Who would have thought adding a sail to a surfboard would make something that people wanted to buy.

My personal objective is to be able to slowly run down a rowing 8 and pull past under pedal power. Only hope is with foils. I guess similar aspirations to Peter Ribe:
http://store.foilkayak.com/clinics/
I have a more efficient propulsion system but still to get foils that work well.

Rick W "
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I'm interested in any and all comments along this line of thought....


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Possible stored energy breakthru: http://www.boatdesign.net/forums/onboard-electronics-controls/super-capacitors-25655.html

 

Doug
You need to produce a specification. Some starting suggestions-

I think it would only be worthwhile as a full foiler.

There are already lithium batteries available that make it possible. Better energy source just gives better range. It may be possible to fly with solar power. It has been done with planes.

For minimal; I read car-topable. So length limitied to say 6m. Weight easily transported by two people. Ideally zero set up time.

To be practical it needs to be beachable in knee deep water.

It needs to be able to handle foil impact without foils being destroyed.

A worthwhile design speed is 20kts.

Ideally flight would be self regulating without any need for constant elevation and roll control.

What is your budget?

Rick W

 

Rick, I'm in the middle of a sailing foiler project and there is no budget for this now. In two years- that would too hard to predict. I'd like to figure on a minimum version that will meet my weight requirements and your proposed "beachability" and speed targets. Any help in specing the power supply, prop etc would be most appreciated. I'm good with carbon and foam or wood and understand foils fairly well but I'd like to hear your thoughts on foil configuration,altitude control and stability.
This will help me a lot in doing the final design.
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PS the solar aspect of powering and/or stretching the range interests me a great deal.
PS #2 in my sailing foiler project I have used a Hobie Miracle cat hull(which is being extensively modified)to save money-cost $300-what about something like that for the electric boat? L/B=19/1, weight about 90 pounds. It would require some sort of small amas/buoyancy pods that could be coupled with very small auxiliary "stability foils" with the main load bearing configuration a bi-foiler? Foils easily retractable..

 

My idea for the hull would be more like a double canoe but just wide enough to sit in. It would have no rocker or very little. Seating position would be semi-reclined to keep windage low as possible.

I would design the hull for optimised drag around 10kts with a view to lift off at around 12kts. There is not much compromise in a flat panel hull and this could be built very quickly and at low cost. If you could find something that was a good fit on the second hand market it might be worth while. Structurally I would aim to keep forces out of the hull as much as possible. The hull becomes more like a fairing for both water and air.

My first inclination would be three "T" foils. I expect they would be around 1m wide and around 60 to 70mm chord. Need to be able to each support around 1000N.

If there is someone interested in building it I will help with design. Would even go to supplying a suitable prop.

Rick W

 

Rick, what would you estimate the power related equipment will weigh-motor, battery, shaft ,prop etc?

 

Rick , your thinking is similar to mine .

But why double canoe? I might not be understanding what you have in mind but the moment you go multiple hulls you get a large wetted surface penalty.

Also , for this application there are no significant heeling moments so there is no reason to encumber yourself with three foils (and therefore three surface penetration resistance points) when given enough {foil span}/{ CoG height above foil} you can create enough lateral stability with just dihedral.

 

This is something I've been wondering about for some weeks now, and it just MIGHT be applicable here...

Would a "down-arrow" (\|/) shaped front foil be able to balance the benefits of "V" foils and inverted "T" foils in some applications. If you bent the arms of the "T" fil up at an angle, and mounted them on a longer strut, you could (in theory) get some of the righting-moment improvements of the "V" foil, and the high-speed "climbing" abilities. Meanwhile, at lower (pre-flying) speeds you would only have 1 spar piercing the surface, thus better pre-flying efficiency. The big drawback I'm seeing here, is that you would have 3-points of surface-pierce when flying at higher speeds.

Does anyone else think this would be a useful option, or have I been putting the wrong "tobacco" in my pipe this week?

 

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Is this what you are thinking about?

 

Depends on the range. You could get maybe 30 minutes of full speed operation with a total drive weight of 10kg. Maybe 60 minutes flying at the most economic speed. Going to 20kg will give something like 30nm range.

If you shopped around for the best batteries you might get even lighter. Something like this would be suitable for testing:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4779
This would give about 10 to 15 minutes at full speed. So an economic way to get it all sorted before you make the commitment to larger battery and/or solar panels.

Rick W

 

Maybe I should have said a twin canoe although they are usually referred to as "double". See attached. Hull would be similar although I would go for flat panel construction CF on corecell. The deck would be higher to improve aerodynamics, single cockpit so pilots seat could be adjusted to operate with right balance one-up and reclined seating.

I have tried a single wide foil and I doubt it can provide roll control without active input. I have a feeling that two tee foils mounted forward of the CoG and centres spaced about 2m apart will be adequate for roll control simply using loss of lift near the surface. I have not tested this though or done numbers on it. Having side mounted foils also makes for easier bump release for jumping obstacles.

Rick W

 

Two man boat ok. Now we're on the same page.

When you refer to your single foil experience ; how much exactly if any dihedral was there and CoG height over foil compared to span?

You should absolutely avoid relying on surface effects for heave/roll stability due to the severe loss of L/D.

 

Somewhat, though I think narrowing down the center span & lengthening the angles on the sides would help give it more righting moment. If my theory is correct, the resulting "V" sections would give increased vertical lift on the section that is leaned towards, while converting the lift of the higher section towards horizontal, thus making it "steer" & balance similarly to a bicycle/motorcycle (without the gyroscopic effect of the wheels). Might even make it easier to steer & balance by using the front "T-V" foil as the rudder instead. ... Would definitely be a new experience on the water.

 

The foil was 2.4m wide and straight. My CoG was about 0.7m above the foil. My aim was to use steering to control the roll but it took all my effort to get to sufficient speed to lift. As soon as it started to lift I would go into a roll and speed would collapse. I did not persist very long with it because I was aiming for something that would better 12kph with 150W.

After the initial testing I revisited the calculations and factored in the wave drag and realised it would be near impossible to better 12kph with 150W so I stuck with displacement mode.

There is a compromise with the strut drag and the wave drag. So the optimum foil will be operating with some surface interference. If the two main foils are separated by 2m they do not need much force differential to provide roll correction.

I envisage two small struts would have similar drag to a larger single one. I also like the idea of being able to swing the foils clear of the water for beaching.

Do your numbers for your proposed foil set up and I will do them for mine and we will see what looks the best. The target is to get an overall L/D of 30 when flying. The system has to survive a full speed collision with a solid object.

Rick W

 

<<<<<<<<The foil was 2.4m wide and straight. My CoG was about 0.7m above the foil. My aim was to use steering to control the roll but it took all my effort to get to sufficient speed to lift. As soon as it started to lift I would go into a roll and speed would collapse. I did not persist very long with it because I was aiming for something that would better 12kph with 150W.>>>>>>

If it had zero dihedral i am not at all surprised that it would have very difficult to control roll characteristics.

However , with those ratios it shouldn't be a problem to obtain sufficient roll stability with dihedral.

 

<<<<<<<<<The system has to survive a full speed collision with a solid object.
>>>>>>>>

I'm afraid that is about as realistic as saying "crash proof airplane"...

You collide your airplane with the earth and it transforms itself into a pile of [censored].

You collide your boat (foils or not) into an immovable object and it transforms itself into a pile of [censored].