Longshot trifoiler

With all the news and achievements of Hydroptere, I am encouraged to think about if a modified trifoiler set-up (based on the former record holder Longshot) is capable to set the new speed sailing record?!

Someone here mentioned the gained knowledge in hydrofoil design and simulation. Maybe you can couple this with an improved vehicle design incorporating ground-effect by the beam and more efficient wings as a replacement for the surf-rigs.

It is still obvious that even the stock Hobie trifoilers are most often setting the fastest time during the different speed weeks!

What do you think about that?

cheers,
Bernd

 

Longshot used foil sections that were designed for a high incipient cavitation speed, but the boat was still limited by cavitation.

I think you have two ways to go to exceed 50 kt. One is to use a planing hull in flat water, and keep the side loads down to avoid cavitating the board(s). This is the Macquarie Innovation approach. The other is to do it with foils in a seaway, ala Hydroptere, but I think some cavitation will be inevitable. In this regard, the surface piercing foils are useful because the foil loading is not fixed - the lower the craft sails, the lower the foil loading.

High foil loading is useful for reducing the skin friction drag. However, when cavitation becomes an issue, you need to start reducing the foil loading, which means putting more surface area in the water if you want the efficiency of a subcavitating hydrofoil.

The alternative is to go with small supercavitating foils. The problem here is the added drag of the separated flow. I think it's possible to design a supercavitating foiler that can sail, but it's not going to be easy.

Aerodynamic drag is as much an impediment to a record-breaker as is hydrodynamic drag. That may be Hydroptere's weakest area.

 

My thought is to reduce the foil loading by a wing shaped cross beam generating lift in ground-effect. Especially in a configuration like Longshot, you should get quite a good flow to that wing. Maybe you can even add same kind of flaps to create a lift/downforce combination and increase righting moment in this way.

Wouldn’t it be possible to use different section on a surface piercing foil without a too big drag penalty? So that e.g. only the tip foil has a supercavitating section?

 

My thoughts on the 50 knot barrier are that I favour a conventional planing surface such as that of Macquarie Innovation or a sailboard. The reason being that it is a proven thing in powered hydroplanes or even a regular V8 powered ski-boat. Foils do funny things when loaded too heavily and do eventually produce significant drag through turbulence.
The Cunningham designed Innovation IMO needs further refinement and maybe even higher grade materials and engineering and of course around 30 knots of wind on smooth water. I can imagine that under such circumstances it will exceed 50 knots on a 500m course.

 

Foil loads

At speed the biggest loads will be horizontal (wind/sail induced) instead of vertical (weight induced) so a horizontal WIG foil will not help that much.

 

As far as I know, all hydroplanes rely also on aerodynamic lift to keep the vessel out of the water! If you look at the footages, you can see that the hulls barely touches the water.

Regarding the horizontal forces: The leeward foil of Hydroptere produces a bending force to the cross beam of up to 60 tons. Idea of the ground-effect lift would be to reduce the necessary force created by the leeward foil by aerodynamic lift. The lift produced by the wing should create less drag than the foil in water! And at speeds Hydroopter or Longshot are moving, I guess a significant amount of lift may be possible? :?:

The foil area, which compensates the sideforce, could be supercavitating section if applicable (see tip of the hydroptere foils).

My basic thought was to keep the craft out of the water. At lower speeds, hydrofoil are used within the dense medium water. As speed increases, more and more lift should be provided by aerodynamic lift of the wing-shaped cross beam. By using flaps on the wing, maybe it would even be possible to create some righting moment?!

I am very new to this forum, but the discussions are really great! Thanks for your replies!

 

Driven by my thoughts I did an Internet search and wound this interesting site:

http://www.wingsystems.com/Development.htm

I remember there were also some french guys working on similiar ideas, but I couldn't find the site.

 

bcv99:

You are forgetting that Hydroptere's leeward foil provides righting moment, as well as vertical lift. How can this be replaced by any lifting surface in the air? Unless, of course, it's way out to leeward somehow.

I think you're on the wrong tack here, but would certainly encourage you to keep thinking, especially of ways to improve the foilers.

Doug Halsey

 

Sailrocket

Did you have a look at Sailrocket already?

http://www.sailrocket.com/

http://www.google.com/search?hl=en&q=site:www.boatdesign.net sailrocket&btnG=Search

 

Hydroptere

The foils on Hydroptere are surface piercing foils unlike the ones on the Hobie Trifoiler, Rave and Skat which are fully submerged foils. Fully submerged foils require an altitude control system on each of the two main foils on the previously mentioned boats( one on the Moth). The differential action of these altitude control systems provides RM. Hydroptere doesn't have such a system because the altitude is "controlled" by the speed of the boat(and her ballast condition-see below); RM is generated by the fact that the center of lift is to leeward of the center of gravity of the boat. It is augmented by the fact that the boat carries up to 1760 pounds of water ballast in each mini ama-probably only the windward one normally. The water ballast is pumped from an intake on the leading edge of the rudder.
Water ballast is also used in the main hull to aid in pitch control.I believe Hydroptere may be the only sailboat in contention for the world speed record with a movable ballast system (except for the windsurfer)?
The Aussie 40 footer Spitfire was also a surface piercing foiler and carried 1000 pounds of ballast. There is a substantial drag penalty for having the foils generate righting moment as on the Trifoiler, Rave and Skat and the penalty increases with speed. Whereas, according to the designer of Spitfire, ballast is good because you "only lift it once".

 

I don't believe that a new outright speed record will fall to a craft that has as one component a relatively fixed aerodynamic lifting wing. There is a very fine line between producing enough lift to bring say 95% of the hull clear of the water which might potentially produce a record time, and have a complete break-out of the hull and any water borne appendages by a slight transient wind strength increase. In contrast, the beauty of the sailboard is many fold.
(1) The lightest possible weight overall.
(2) The natural tendency to lift about 90% of the hull clear at speeds of over 30 knots and even over 40 knots very little more surface reduction which is a good thing, as water contact = control of board attitude and direction.
(3) Of all systems currently in use the speed fin on a sailboard has the least tendency to develop cavitation and hence loss of control, (when sailing at about 130 degrees to the true wind direction on a speed course), compared to the hydrofoils of Hydroptere and the fully immersed Moth style foil, when approaching the 50 knot barrier. Importantly the sailboard board fin is essentially a control plane and not a load bearing one, as it must be in the other examples. This allows it to be much smaller, and of lower drag profile as well.
(4) The free sail system which is aerodynamically potentially as good IMO in L/D as the wing of the C class cat "Cogito".
(5) A highly intelligent and mechanically subtle articulating machine wired into the computer control system in such a complex and efficient way that Bill Gates can only dream about. (Read expert sailboarder for this description)
(6) The sail simultaneously produces forward drive and lift, with fairly low values of aerodynamic drag, in such a way, that the ratio of lift to drive can be instantaneously modified by a sytem so intelligent that it can anticipate changes in wind and water a moment before they occur, so allowing fine tuning adjustments very precisely, and with far greater precision, than any yet invented mechanical device, at the correct moment that the new conditions now impinge on the sailboard.
I am not surprized that Finian Maynard still holds the outright 500m speed sailing record!

 

wing lift + foils

Bernd, you may find this interesting; it is from the A class mail list and mentions a speed sailing prototype being built in the US by a Team I haven't heard of before:

"Hi Jeremy!
It has been a year since your e-mail, but we have only now gotten in a position to buy a used A-Cat, and perhaps you never found a buyer for your boat.
The price and condition of your boat seem satisfactory, but we are in New Jersey so shipping might be unacceptably expensive. Sometimes items like this can be piggybacked on a moving van shipment if they can be disassembled to reduce the size for shipment.
It is also unclear exactly how appropriate the boat would be for our purposes so I will explain what we are trying to do and hope that you can send us photos if the boat is still available.
We are developing new techniques for speed sailing which we hope to test on a modified A-Cat. Specifically we will mount a sailcloth airfoil between the mast and the bow, and another smaller one aft of the trampoline. These are predicted to the lift the boat off the water at true wind speeds above 15 knots and should result in boat speeds in excess of 30 knots. We need a boat which can be modified so that the hulls are on center lines twelve feet apart and which is constructed in such a way that it is possible to attach mounting fixtures for our airfoils. We hope to keep the weight of the modified boat below 200 pounds.
Please let us know if your boat is still available or if you know of a boat which we might obtain.
Thanks.
Cheers,
Jay Eveleth, Kittihawk20 Speed Sailing Team"

 

Lifting the hull off the water with wings is meaningless unless you can do it with less drag than the hull has in the water. I haven't seen anything in any of these concepts that addresses why it would be less draggy to fly than to float.

 

I once did a study for an 80m passenger ferry which used wing in ground effect to augment hydrodynamic lift. At 90 knots, the reduction in drag due to aerodynamic lift was a whopping 2%. At speeds less than this the drag was worse than that for the hull without the wing due to the added aerodynamic drag of the wing and of course the added weight of the wing structure. Granted that this was quite a large vessel compared to a small sailing dinghy, but I'm sure that the same principles still apply. I suggest doing a numerical analysis first to see what you are up against.

Mal

 

Haha, did you see the genoa rolled up on the forestay during their 1nm record run? How arrogant, eh!

ah, but flying might be softer and quieter than planing!
You should have seen the planing behavior of "Kun Fett" the proa kiteboat model! Hilarious moves! Makes me a bit suspicious about using planing surfaces as "direct sensors" for hydrofoils (like the miller sailboard) as well.

There is another point about air control surfaces: They can still work if you loose contact with water entirely! Look at Jon Howes' monofoil for an example.

Here is a sketch of another silly proa concept, I figure it might have some pitch stability issues, and a really low AR - shitty efficiency below supersonic. I'm not good at perspective drawing but the thing that sticks out in front is supposed to "sheet in" the "slat" as it rides the water.

The second one is different plans for the Kun Fetto (if I have enough fishing pole left); the front sensor is supposed to adjust the relative AoA of the foil in the water and the air. Sorry for the unfinished style, maybe it is not at all understandable for anyone else. I wanted to think about the difference between that, and a miller style fixed setup (which would also, at this power/weight, need a tail I think).