Electric Foiler(or foil assist)

[Doug Lord]

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:
----------
"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 "
===================
I'm interested in any and all comments along this line of thought....


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

[Guest625101138]

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

[Doug Lord]

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.
-------------
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..

[Guest625101138]

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

[Doug Lord]

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

[Tcubed]

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.

[robherc]

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? :P

[Doug Lord]

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? :P
----------------------
Is this what you are thinking about?

[Guest625101138]

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

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

[Guest625101138]

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.

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

[Tcubed]

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.

[robherc]

Is this what you are thinking about?
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.

[Guest625101138]

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.

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

[Tcubed]

<<<<<<<<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.

[Tcubed]

<<<<<<<<<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].

[Tcubed]

<<<<<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.>>>>>>>

I would love to but i'm still learning how to plug the data into michlet and xfoil FLR5 so i'll come back to you on that once i'm confident of the process.

I think L/D of 30 is quite realistic . Strut resistance is not proportional to wetted area though.

[Guest625101138]

<<<<<<<<<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].

The analogy is wrong.

We have a boat doing a leisurely 20kts. I would not expect a planning craft to be destroyed if it hit a log, rock or reef at this speed. Worst damage expected would be a scratch in the gelcoat and maybe a bent prop.

I have seen the aftermath of planing boat hitting a log at 35kts and the only indication was a slight ding in the prop. It was a timber boat with a brass rubbing strip on the keel. The motor certainly bounced out of the water and may have shocked the transom but just lowered back down and away it went.

This is an extreme example but typical of the abuse that you reasonably expect a boat to take:
http://www.youtube.com/watch?v=Zt0eGnu7Sk8&feature=related

If your foil system cannot take a decent knock then it will not be acceptable. That is in the original specification.

Rick W

[Tcubed]

<<<If your foil system cannot take a decent knock then it will not be acceptable. That is in the original specification.
>>>

I agree , but only to the point that one might expect a normal boat to withstand a blow.

I do not expect any small boat to be able to survive falling off a wave onto a barely floating container, for example. It is simply not realistic.

[Tcubed]

And btw 20 Knts is not leisurely. You can pedal your bike at that speed and steer into a parked car say, and you'll know what i mean.

[Tcubed]

Oh, and the video is quite entertaining, and is also a great example of recklessness and the kind of thing that makes boat builders like me cringe!

[Guest625101138]

And btw 20 Knts is not leisurely. You can pedal your bike at that speed and steer into a parked car say, and you'll know what i mean.

Compared to 800kph of a jetliner 20kts is leisurely, which is what you were comparing it with.

Also I am not saying a sudden stop but something that can be reasonably expected to happen when navigating any river or coastal waterway. For that matter an ocean as well.

One of the advantages of old style long keels is their ability to ride up on a rock or beach to absorb energy. Modern deep keelers just come to a shuddering halt with some energy being absorbed by dipping the bow.

A great feature of an outboard boat is its ability to ride up on sand banks without experience damage.

From my own experience I would say that anyone who has not gone aground in a small boat has led a very sheltered life. If you are building boats that are not able to take a grounding or hit a partially submerged object and remain operable then you are deluded. It is a fact of life and not what I regard as careless operation. I regard someone who designs without that possibility accounted for as negligent.

Rick

[Tcubed]

Ok lets not get worked up here .

Yes you have mostly valid points , but it's a question of degree . As in how much damage.

For example the outboard boat hits a gradual sand bank and it will still function afterwards but it was not a boat improving event.

I guess my point is that at these kinds of high speeds it is not reasonable to expect that your foils should be able to survive a collision with a substantial object , like say a log.

[robherc]

LOL, maybe if we made them out of Kevlar-sheathed, hammer-forged Titanium billet they could...but I don't think that'd be very good for our weight considerations. (and, to keep things reasonable, let's just say that we want the foils to withstand the same abuse as the aforementioned fin keel...is that agreeable to everyone?)

[Guest625101138]

...
I guess my point is that at these kinds of high speeds it is not reasonable to expect that your foils should be able to survive a collision with a substantial object , like say a log.

This is where we disagree. I want to be able to run down a river at 20kts knowing if I hit a log or submerged branch I will not have expensive damage.

I have managed to do this to a reasonable degree with propellers and compete quite well with paddled craft in log infested waters. I expect the same with foils. Anything less makes them fragile and of very limited use.

As an example the mirrors on my car protrude quite a distance and they take regular pumps in car parks and just fold out of the way. They afford protection for pedestrians and cyclists by easily folding to avoid extensive injuries. If I had to replace them every time they took a knock I would carry barriers to sit beside the car each time I used a public car park. In fact I would also need them in my own garage.

Rick W

[Tcubed]

Well i would say if you can design something like that then i want some lessons!

To me reasonable would be if there was terminal damage to the foils it would leave the hull itself watertight. Much like daggerboards in multis.

I think that designing a foil boat for log infested waters might not be the most practical ...

[Guest625101138]

Well i would say if you can design something like that then i want some lessons!

... ...

No problem. Happy to teach you.

Rick W

[Tcubed]

Thank you.

I will make good on your offer straight away.

I have as shown below the beginnings of yet another design in rhino 4. I also have michlet program with a black window looking at my dumb face....

How do i get that hull's relevant data into Michlet for an analysis?

Would very much appreciate some pointers and can move this to another thread or wherever else.

[Doug Lord]

T,Rick: keep it here-please....

[ancient kayaker]

Crash survivability may be the make-break issue for a commercial boat, although a home builder might be expected to have more caution than the bozo in the video. Since a boat hull is designed to slide through the water it tends to have the right shape to slide up and over a low obstacle. It is also broad in shape which contributes to its durability.

None of that is true of a hydrofoil. Bulk them up and the drag will be unacceptable, use a sweptback strut and the foil will ventilate. Any foil appendage I can think of looks pretty much like a log-fishing hook. If Bozo had been in a foiler with the foil made from infinitely strong unobtanium he would have ended up in the water with his dog, and maybe run over by his own boat.

To expect a foil to survive a collision with an underwater immovable object is like expecting a mast to survive contact with a bridge without damage. It's safer if the foil (and the mast) yield.

...As an example the mirrors on my car protrude quite a distance and they take regular pumps in car parks and just fold out of the way... Rick W

That sounds like the answer. If the foil(s) can snap up and out of the way that leaves the hull to plop down into the water from a modest height. However, all the foils need to snap up at the same time, and quickly enough to avoid transforming into sea anchors. I don't think it's enough to let the foil spring back from the strut leaving the strut stationary, the whole thing has got to pop up.

[Tcubed]

The rear view mirror analogy is promising but a rear view mirror is designed to fold back when there is a relatively slow speed encounter. At sixty mph it no longer folds back. It just disintegrates into shrapnel.

[Guest625101138]

Thank you.

I will make good on your offer straight away.

I have as shown below the beginnings of yet another design in rhino 4. I also have michlet program with a black window looking at my dumb face....

How do i get that hull's relevant data into Michlet for an analysis?

Would very much appreciate some pointers and can move this to another thread or wherever else.

Delftship has an export function for Michlet. I use this method.

I have done various manipulation of the Michlet hull table for various reasons but it takes me a bit of time to work it out.

My usual process is to start with Godzilla to optimise the hull for the conditions. I import the offsets into Delftship and clean up the hull to suit how I will build it. Then I export the hull to Michlet to check that my fiddling has not altered performance much.

The attached is a Michlet input file for the V11J hull. The photo shows the boat. It will give you some idea of the translation required. There are explanations around.

If you delete the existing in.mlt file in the folder where you have the michlet exe file and replace it with the attached file renamed to in.mlt it will give you the outline when you run Michlet and you can get the drag data for this hull.

I find the Godzilla element of Michlet to be very powerful and always start with this for a new hull. You only need 4 numbers to specify a hull to start with.

Rick W

[Guest625101138]

Terry
You have it partially solved. You only need the other bits of the jigsaw to give it a real chance. The attached might give you a clue to what I am thinking. This blade always trails horizontally with little drag unless it is being swept vertically. (Based on the front mount being vertical of course)

The other thing I learnt with this was its ability to balance through symmetry alone. Out of the water it flopped sideways but once in operation it was very stable laterally with no tendency to twist.

I think you could make a foil from very strong material that is very light (probably CF) and it has a completely compliant mount that releases if the force just exceeds the design load. The foil itself will have very little inertial energy. Maybe even some strategically placed compliant bump strips to give momentary energy absorption. Could be hydrodynamically useful polyurethane winglets for example.

Rick W

[Guest625101138]

The rear view mirror analogy is promising but a rear view mirror is designed to fold back when there is a relatively slow speed encounter. At sixty mph it no longer folds back. It just disintegrates into shrapnel.

20kts is a leisurely pace even by comparison with 60mph.

The point I am making is that the specification requires it to take a decent bump. It will not be falling off 20ft waves onto containers at 20kts. However it will be beached at maybe 10kts as it will have a great tendency to glide and unless the controller has an effective reverse it will just glide into the shore. Very easy to do until some experience is gained with its operation.

In fact maybe we need to specify it to have a reverse mode.

Rick W

[robherc]

If you spring-loaded the strut on a "T" foil, mounted to the midline of your hull, then upon impact it would get pushed back & up to the hull. Once against the hull, the lifting foil would roughly equate to a vertical plate being dragged through the water/mud/sand & make a fairly effective brake. This idea MIGHT enable the foil to survive log impacts, but it WOULD enable it to survive most groundings & simple stop the boat. In the case of a log (assuming it doesn't break the lifting foil), sand bar, reef, or cabbage-head; the foil would flip up some, clear the obstacle, then (depending on craft speed) either get held up against the hull until the craft slowed sufficiently, or flip back down into a normal operating position. Either way, it would have slowed the craft down enough that you're going to have to build some speed back up before you're likely going to be "flying" again.

[Guest625101138]

If you spring-loaded the strut on a "T" foil, mounted to the midline of your hull, then upon impact it would get pushed back & up to the hull. Once against the hull, the lifting foil would roughly equate to a vertical plate being dragged through the water/mud/sand & make a fairly effective brake. This idea MIGHT enable the foil to survive log impacts, but it WOULD enable it to survive most groundings & simple stop the boat. In the case of a log (assuming it doesn't break the lifting foil), sand bar, reef, or cabbage-head; the foil would flip up some, clear the obstacle, then (depending on craft speed) either get held up against the hull until the craft slowed sufficiently, or flip back down into a normal operating position. Either way, it would have slowed the craft down enough that you're going to have to build some speed back up before you're likely going to be "flying" again.

That is why I preferred the idea of three foils with two main ones either side of the hull. they do not get jammed against the hull.

Also why does the foil have to be rigidly mounted to the strut. It could be a ball joint on the bottom of the strut so it can move freely in most directions. It only needs to produce a vertical force.

Rick W

[robherc]

1. If the foil is on a ball joint @ the bottom of the strut it can't give you any righting moment.

2. In your 3-foil setup, you would still have the rear foil.strut swing up into the hull, and the front foils (though not the struts) would still strike the bottom of the hull, unless you mounted them extremely far apart. Also, if the front foils came completely out of the water, they'd have a VERY hard time pushing back down through the surface of the water to return to their operating position, unless you slowed the boat down very considerably (and they'd still act as drag-brakes the whole time they were trying).
I guess that idea would work if you went with 4 foils, spaced widely out to the sides, and made them spring-up, completely clear of the water, once they reached a certain point.

[Guest625101138]

1. If the foil is on a ball joint @ the bottom of the strut it can't give you any righting moment.

2. In your 3-foil setup, you would still have the rear foil.strut swing up into the hull, and the front foils (though not the struts) would still strike the bottom of the hull, unless you mounted them extremely far apart. Also, if the front foils came completely out of the water, they'd have a VERY hard time pushing back down through the surface of the water to return to their operating position, unless you slowed the boat down very considerably (and they'd still act as drag-brakes the whole time they were trying).
I guess that idea would work if you went with 4 foils, spaced widely out to the sides, and made them spring-up, completely clear of the water, once they reached a certain point.

Rob
You are not trying very hard.

The front foils have a back stop that prevents rotation as they lock into position. Does not take a lot of thought to work this out. An alternative could be a back plane to provide the necessary moment but this would produce a large counter moment when trying to roll the foils down at speed.

The 'T" foils will only be around 800mm wide. That is 400mm either side of the supporting strut. So at 2m centres that gives 1.2m between tips. The hull is only 500mm wide. So at least 300mm from tip to hull.

Being on a ball joint the foils just trail once unlocked.

The stern "T" foil/combined rudder and drive simply swings up like an outboard. It thrusts against a stop. Swing up provides both foil and and prop protection. Angle could be used for flight trimming if necessary. Same ball joint arrangement of the foil allows it to trail once the rudder strut trails.

You are not showing much imagination.

Would be quite easy to get to speed with both bow foils rolled back and just fold down and lock in to get lift. Could easily be done on the fly.

Remember this boat has a total mass of 200kg loaded. The front foils carry 80kg each. The lift to drag is 30. The drag is less than 30N. That is not much force. Until the foil starts to provide lift (the last couple of degrees of engagement) the drag is considerably lower than 30N.

The foil support system does not even need a dedent or spring. It can be self locking with over-centre action. Might have some sort of bungee just to give a little extra restraint when jiggling around.

Surely you do not expect me to do the whole design!!

Rick W

[robherc]

OK Rick,

Most of that sounds fairly plausible except: How are you going to design a foil with L-D of 30:1 with a submerged ball joint, U-joint, or anything similar?
Every time I try to imagine something like that, especially if it's supposed to have 90* forward rotation, I end up seeing MUCH lower L-D ratios...ball joints just aren't THAT graceful underwater, they fairly unavoidably add some drag.

Also, I had overestimated the width of the front foils from your earlier post. You had said 1m foils on struts 2m apart, and I was picturing 1.75m foils in my head...don't ask, it was 3AM here....

[ancient kayaker]

Maybe the spring-loaded strut in post #32 has a flaw. I assumed it retains lift as it swings back by virtue of the parallelogram linkage, so I don’t see it as a brake the way Rob does. It also eliminates the need for the other foil(s) to cancel lift simultaneously, and maintains speed. However, as Rob pointed out, when it swings back the lift vector applies more torque to the spring-loaded pivot and it may not spring forward again at speed.

However, if the strut is swept back it will tend to glide over obstacles the way a fixed keel does, and if continues down past the foil it should lift the boat over the obstacle allowing a fixed foil to be used. A small winglet(?) partway down the strut will prevent ventilation. It should handle horizontal solid obstacles, but the foil may need a vertical axis hinge to dodge tree stumps which I have added.

I imagine reverse would use displacement mode; slower, like an auto, but perhaps the foils could be sprung loaded in the reverse direction at the hull attachment.

[robherc]

AK,

I hadn't thought about parallelogram linkage, but that could be a useful way to reduce the braking that the foil would cause upon swinging up. Then, if it didn't return to its original position, it would still be providing SOME lift, and it would be able to swing back down at a much higher boat speed than the fixed foil on a spring-loaded strut.
Either way, I like your vertical-hinged, swept-back foil design for avoiding stumps. The swept-back foil should be able to self-track very well in all modes except for reverse without the need for a spring that could get fouled or weakened over time. Would you lock the foil in place for reverse mode, or remove/raise it some way? I think it's a good idea, but reverse-mode will give you some hassle. My best spur-of-the-moment idea there would be to have a vertical hole through the front center of the foil, and have a locking-bar that can slide into the hole while the foil is centered to hold it in place for reversing.

Would there be any way to retract your design vertically up near the bottom of the hull for beaching/reversing?

[Guest625101138]

OK Rick,

Most of that sounds fairly plausible except: How are you going to design a foil with L-D of 30:1 with a submerged ball joint, U-joint, or anything similar?
Every time I try to imagine something like that, especially if it's supposed to have 90* forward rotation, I end up seeing MUCH lower L-D ratios...ball joints just aren't THAT graceful underwater, they fairly unavoidably add some drag.

Also, I had overestimated the width of the front foils from your earlier post. You had said 1m foils on struts 2m apart, and I was picturing 1.75m foils in my head...don't ask, it was 3AM here....

The foils did shrink a little when I looked at what was required. My first guess is that one cannot make a foil much smaller than 60mm chord that will carry the load with some margin. So I set this as a limit. With this limit the lowest L/D foil is around the 800mm mark across. My initial guess was 1m. The 60 by 800 can achieve the L/D of 30.

My vertical strut is 10mm wide so I have to devise a compliant connection that can take a vertical force of 800N and horizontal force of 30N when in the locked position. Forces are quite steady so low fatigue cycling. Should not be a huge ask. The joint could be a little thicker without noticeable increase in drag.

Refining the design with proper stress analysis might reduce the chord. At this stage I am still wondering if the 3 tees offer the best solution.

Rick W

[robherc]

...OK, while you do your stress analysis and get your chord perfect on the 3-strut setup, I think I'll toy around with my very NON-definite balancing foil idea & see if I can make anything (cheap) that will prove my idea to be a feasible way to balance the thing on only 2...so fewer struts, and (hopefully) less surface drag.
I'll leave the analysis to those of you with more training/equipment than myself...as long as it's only my own life at stake, "trial-and-error" will work for me for now.
I'll let you guys know if I find anything useful in my bathtub tests. ;)

[ancient kayaker]

AK,

... I like your vertical-hinged, swept-back foil design for avoiding stumps. ... Would you lock the foil in place for reverse mode, or remove/raise it some way? ...Would there be any way to retract your design vertically up near the bottom of the hull for beaching/reversing?

Yes, simple is sometimes best. It should be should retract for reverse, I don’t like the idea of foiling backwards! I think for reversing it could just pull up and forward along its own LE until the foil snugs up under the hull although I would prefer some way of getting it completely out of the way for beaching.

[Guest625101138]

My idea of a two seater electric foiler. Design weight is 200kg. Total boat weight is 50kg including battery.

Would foil from 14kts. Design speed is 20kts.

Requires 950W motor output at design speed.

Features overcentre locking of front foil beam and tilting stern "T" foil to provide foil impact protection.

Rick W

[Doug Lord]

Very interesting ,Rick. Would you use wands for altitude control?

[Guest625101138]

Very interesting ,Rick. Would you use wands for altitude control?

I have not got into the control aspects other than thinking about trim. The front foils would overcentre to a high lift position for the take off at 7m/s and then be trimmed back once flying to get the most economic lift. I can envisage some form of trim control on the rudder tilt as well. In fact I may have enough range with this to just have a single stop on the front foils.

I have not done much work on lifting foils. I have not done pitch stability analysis. Ideally it would be self stabilising for roll and pitch but I do not know if this can be achieved.

It is somewhat different to a sailing foiler because the power input is constant. All forces on the boat are notionally steady as well.

If someone was actually interested in building it I would put more effort into the flight control aspect.

Rick W

[Chris Ostlind]

On to another movement within the greater piece being played.... we have this new foiling machine as an alternative to the electric foiler being discussed.

"February 10, 2009 The Foiljet MR1 is a new personal watercraft concept that takes the best features of a motocross bike and jetski, throws in two hydrofoils plus a silent, energy efficient electric motor to create what would have to be a surefire recipe for outrageous fun. The design looks something like a motocross bike, but instead of wheels there are beams with small hydrofoil wings mounted at the ends that can be raised or lowered. The concept would use a 15 kW (20 hp) electric motor housed at the end of the rear beam with its instant electric torque lifting the craft out of the water to become "foil borne".

To cope with shallow water the beams can be raised at the flick of a switch. The electric motor runs off a 48V battery that should see three hours of full load running with the possibility of a theoretical 10 min recharge time.

While still at the purely concept stage Matt De Bellefeuille & Robert Vandenham have come up with an original design that most definitely deserves to reach the prototype stage.

The designers have selected a T-shaped fully submerged foil system which, while not affected by surface waves is not self stabilizing, so it needs constant adjustment of the angle of attack of the front foil to keep the craft level with the surface. Front foil angle adjustment on the Foiljet MR1 is made manually by what would conventionally be the clutch lever on a motorcycle. In larger applications this sea-keeping function is automated with a computer system that measure either surface height or pitch and roll to make constant fine adjustments to the front foil.

Hydrofoils produce relatively no wake and electric propulsion is near silent, so if the Foiljet MR1 makes it into production it may allow current laws against jetski’s on inland water ways to be relaxed around residential areas."

There is more info at the designer's website:
http://www.debelle-design.com/index.html

Be sure to follow the arrows at the lower right hand corner of the imagery

[Guest625101138]

....... The concept would use a 15 kW (20 hp) electric motor housed at the end of the rear beam with its instant electric torque lifting the craft out of the water to become "foil borne".

To cope with shallow water the beams can be raised at the flick of a switch. The electric motor runs off a 48V battery that should see three hours of full load running with the possibility of a theoretical 10 min recharge time.

While still at the purely concept stage Matt De Bellefeuille & Robert Vandenham have come up with an original design that most definitely deserves to reach the prototype stage.

......
Chris
I did some quick sums on the "concept".

3 hours by 15kW is 45kWh. So with the best current battery technology getting 100Wh/kg there will be a 450kg battery. About half a tonne of battery. No way that hull will support that weight. Will need powered wheels on the bottom of the foils so you can do a flying start down the beach or jetty and just pray the motor does not stop when you are in deep water. (The concept does not show any wheels)

The current best batteries cost roughly USD1/Wh in quantity. Hence you could expect to pay USD45,000 for battery to operate the USD15,000 concept that does not float and has no wheels for running down the beach. (You need to read the fine print of course -"BATTERIES NOT INCLUDED"

One other small obstacle is the 300kVA generator you will need to charge the thing in 10 minutes. If you and a couple of mates hit the beach together and want to recharge at the same time you will need a 1MVA power plant. You need a decent truck to carry this. So the truck and generator brand new will set you back a further USD400k. Of course you could buy a unit second hand or even hire the set up. Probably USD5000 for a weekend. These are sound proofed so is in keeping with the low noise craft. Maybe you could restrict operations to close proximity to power stations and get them to put a 1MVA transformer off their HV towers.

At least what I proposed has a measure of reality even if I have not determined what is required for flight stability. I expect a home builder could build my concept for USD2,500 in a functional mode while, with quantity production, you might get them for USD6,000 retail.

I expect it could be made car-toppable with the basic hull coming in at 20kg, the wings and front foils being carried in the boot (trunk) along with the rudder/motor and battery pack. Would take a couple of minutes to set up on the beach and two people could carry it to launch from the beach.

As it is drawn it would be twitchy (KMT is only 300mm) and might need a float on the wing extremities to provide static stability. THe wings will help a little but not much as currently drawn.

I have not done a full check of power demand through lift-off but making the hull any wider is going to increase this. The proposed motor has ample peak power. I have not checked what cooling is required to get the continuous rating around 1kW.

Rick W

[Chris Ostlind]

Thanks for the effort with the calcs, but come on, man.... why do you want to douse the work of Mssrs. De Bellefeuille and Vandenham when you already know that this is a revolution?!

Take off that doubter's head piece you wear and recognize that this foiler will be built, it will do everything they say it will and it will be available at less than USD$10K and will be driveable, right out of the box, by rank amateur recreationalists in a matter of seconds.

After all, these guys, deB and V'ham, are industrial designers, they have run all the numbers and your constant negative criticism and total lack of understanding is getting pretty old.....

;-)

Foilers of any kind... Interesting segment of the boating environment? Sure!

Revolution of stupendous proportions that will sweep away our tired, limited scope carcasses?

I think not!!

[Guest625101138]

Chris
Foils certainly offer an interesting avenue for exploring. I cannot see an imminent revolution. Overhyping their potential uses just takes thing backwards.

I know a guy who made a pedal powered version of the foiler similar to what you pictured. He actually purchased a set of Hobie foils to propel it and he imagined he could get lift as well from the flapping foils. He spent many hours in the water moving very slowly or simply getting dunked.

Actually thinking about Hobie I wonder what has made more money - the Hobie trifoiler or the Hobie Mirage. Both are applications for foils. Silly part is that a propeller is way better for propulsion than the Hobie flappers.

I have a chuckle each time I think of the Mirage drive these days. There were a group of young ladies using a twin mirage in the Murray Marathon this year. There were enough of them to operate in relay. They started in the first group 30 minutes ahead of me and I would catch them each day about 30 minutes after I started. Each day they made some comment about the relative speed, how come I could go so fast or desire to have a boat like mine. They only actually finished on the last day because they were picked up by the sweeper boats on the first four days. Their time on the last day was just under twice my time.

Irrespective of the relatively poor performance of the Mirage I did recommend to my sister that she buy one. She had tried one of my boats when visiting a couple of years ago and decided pedalling was fun. She now has a Mirage and her hubby is so taken with it that he wants one. They are becoming a very popular fishing platform in Australia. So horses for courses.

Revolutions usually sneak up on people. Many years ago I made deep V boat that was 6ft long with 3ft beam powered by a 6HP outboard. It fitted in the back of my car. It was the tender for my yacht and at that stage the outboard doubled as the yacht auxiliary. That little boat was designed to be unsinkable and would do about 25kts one-up. It was not a lot different in form to a modern jetski but it was maybe 10 years ahead of the jetski.

I doubt that the first guy who fitted a jet into a short hull was thinking revolution. Likewise the first guy who stuck a sail on a surfboard. No matter what it is, it takes something like 30 years from viable technology to common use. Lithium batteries make electric powered vehicles of all sorts viable. I think it is only a matter of time before we see common use. They have already killed IC engines in model planes and opened up a whole new world for many with dramatically lower cost of entry into RC model planes and helicopters. For my last birthday I got a remote controlled model plane I can fly in the house. Can you believe that! It flies for about 10 minutes on a charge. Amazing technology.

LiFePO4 technology is now 13 years old so in another 5 to 7 years we should have the panorama of its (or equivalents) potential. In 18 years average Joe might just take lithium technology for granted.

I am just rambling now - I did my undergraduate thesis on electric cars. The final slide in my presentation was a drawing of a typical car battery of the day with four wheels and a steering wheel with a driver perched on the edge of the battery. The aim was to point out that electric cars were not viable without significant leaps in battery technology. That has now happened and, along with modern material technology, you get some interesting possibilities like the Aptera.

OK - finally got there - if there is a revolution here it is with lithium batteries not foils. If a technology is 100 years old and has not become common it is not going to happen:
http://en.wikipedia.org/wiki/File:Forlanini_Idroplano-Forlani_Hydrofoil_1910.jpg

There is a window of opportunity to get foils established for boating applications combined with lithium while the batteries are in their early development. As time goes by their improvement will make use in more conventional boats viable.

Rick W

[clmanges]

Rick,
You killed the Foil-Jet . . .but you used their own numbers to do so . . . they've spec'd a 15kW motor (which does seem like overkill to me), and the rest of their design falls down based on that, as you've shown.

But, you previously calculated a boat to get on foils with 950 watts. What if the Foil-Jet was revisited, starting with a much more modest motor, and a prop drive instead of the jet-drive? Is it possible that way? I think two or three hp should drive it for about an hour. It would lose something to windage (maybe too much). I just had to wonder. Their proposal is still unrealistic from other angles, starting with the price.

In any case, I wouldn't want to be on the Foil-jet and hit a submerged log . . . that could be a bad day for the rider.

[Guest625101138]

Rick,
You killed the Foil-Jet . . .but you used their own numbers to do so . . . they've spec'd a 15kW motor (which does seem like overkill to me), and the rest of their design falls down based on that, as you've shown.

But, you previously calculated a boat to get on foils with 950 watts. What if the Foil-Jet was revisited, starting with a much more modest motor, and a prop drive instead of the jet-drive? Is it possible that way? I think two or three hp should drive it for about an hour. It would lose something to windage (maybe too much). I just had to wonder. Their proposal is still unrealistic from other angles, starting with the price.

In any case, I wouldn't want to be on the Foil-jet and hit a submerged log . . . that could be a bad day for the rider.

Curtis
The Foil_jet has enough power to do around 40kts. I did not do a full calculation because I would need to look carefully at the foil profile.

The difference is most easily explained by comparing the wings on a glider to a jet fighter. One is very efficient the other is very fast. With the very narrow foils the Foil-Jet is more like the latter. Efficient it is not. The L/D of the Foil_jet will be no more than 10. Not much better than a Jet-Ski.

The desire to only use two foils by others it to achieve better efficiency but I think by the time you get a self-stabilising configuration the L/D will be back around what I have. With two foils it is very easy to engineer the impact avoidance system, which I feel essential for a practical boat.

Efficiency of my propeller is 88%. The jet thruster will be around 60% as sketched. It has a very small nozzle. The concept has been done by a student I guess who does not have much engineering knowledge. Just enough knowledge to make it seem feasible. You could certainly make something like that but it would look different to that shown.

Rick W

[Guest625101138]

Doug et al
This is a foiler I did some prop analysis for in its design phase last year:
http://www.youtube.com/user/MrDonLuigi
http://www.youtube.com/watch?v=FsAL_2fRS6E

Not too far from my concept a few posts back.

Rick

[Doug Lord]

Rick, thanks for posting this-very interesting! What is the guy using for altitude control? Is the forward foil surface piercing? Do you know the all up weight of the boat?

[Guest625101138]

Rick, thanks for posting this-very interesting! What is the guy using for altitude control? Is the forward foil surface piercing? Do you know the all up weight of the boat?

Doug
The initial weight estimate was 100kg. They provided a drag curve that was determined using readily available software for displacement mode, combined mode and full flight mode. We agreed on a design speed and design drag from this data. The power I determined with the motor they selected was well under 1HP at the selected speed. I have not seen any test data on what eventuated.

I do not know if they use any control surface for attitude control. The initial idea was to achieve inherent stability in flight.

Rick W