Electric Foiler(or foil assist)

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

 

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

 

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

 

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!!

 

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

 

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

 

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

 

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