Sunday, December 28, 2008

turning on HUNDREDS of people

I don't understand. I offered Bora the chance of a life time chance to make a real difference in building interest in the Moth -and foiling-while still getting your chance to try to ridicule me in front of HUNDREDS of people!!

I find it incredible that he would turn it down.

In early March(I think) Tinho Dornellas will have his annual Windsurfing Midwinters at his location here at Kelly Park on the Banana River. I suggested he come here then and put on a demonstration for the hundreds of people( many kids) and I'll sail the Moth when he's done.

When here he can go visit, Mickey Mouse(only 50 miles), and the space center as well as having the great pleasure of turning on HUNDREDS of people at one location. And make a great contribution to foiling in the US as well.


Well Bora, are you in? You come down here and demonstrate the boat for the people and I'll still show you how to foil it!

Friday, December 26, 2008

Bethwaite foiling 49er

The fact that Bethwaite is developing a BI-FOILER 49er is revealed in the Jan 2009 Seahorse with a picture, where you can clearly see the sliding bench seat.

Bethwaite is confident that his team is almost there, which is, of course a revolution.


Shown underway as well is the notorius outboard powered 49er hull using three foils with a trailing edge wand on the forward foil.

Soon, when they learn the ways of foiling and grow in their knowledge of my patents, they too will want strike me down with all their hatred, and their journey towards the dark side will be complete.

Thursday, December 18, 2008

the Master of Multifoiler Design is back!

18' Multifoiler from Dr. Sam Bradfield, the Master of Multifoiler Design is back!

This time his boat has many new features including a new automatic altitude control system developed by the Hydrosail Team. Here are the specs:


- 18’ racing trimaran
- highly-maneuverable, except when it is not
- light and lean for speed with large flight window
- T-foils with automatic flight control systems, that are manually controlled
- Park benches
- High windage Mirabaud style pods hulls
- Jump-o-matic version will be available

The two main foils roughly split the load-which is way more than the weight of the boat.

This is a new project with technology only hinted at in a few other foiler prototypes. Bradfield has held the world speed record in the B class with a foiler of his own design and comes second only to me when it comes to foiler development experience.

He is fully capable of producing an astonishingly high performance foiler.

I've always believed a bi-foil monofoiler was better than a Rave in light to moderate air-but this new boat(as I understand it) will be very light with no wands. Based on my numbers, it will take off in the same wind a Moth will.

And will have the same advantage the Rave did in winds over 20.

Bradfield is pioneering a differential altitude control system for the Osprey that will be extraordinary....

I am sure that this will be a great commercial success, just like the rave, and the Hobi trifoiler and the Kona kat.

Thursday, December 11, 2008

Foiling crediblity

I see an attitude lot from some Mothies: as far as foiling goes some of you think you're the only game in town.

That is no longer true since there are NON MOTH bi-foil monofoilers and multifoilers in development or being sailed all over the world. The attitude that you know all there is to know or will ever be known about foiling is bullshit-get over it!

My experience sailing 2 different monofoilers, 1 multifoiler is far more credible than a couple of years racing a moth.


Tuesday, December 9, 2008

forget planing, the foiling sportsboat

The next breakthru is not planing upwind-it is flying a sportboat upwind.....
30' LOA sportboat on foils:

My personal opinion is that chasing an upwind planing keelboat is a lot of effort to go a little faster-seems that a bi-foiler sportboat would be a better choice-a lot of effort to go a lot faster upwind and offwind.

BUT you should put some numbers on paper and see what it would take.
Bethwaites SCP/Total weight ratio predicts that a boat with a ratio over 30% will plane upwind. It goes like this:

RM(righting moment) divided by the distance between the CE(center of effort) and the CLP(CLR)(center of lateral pressure(resistance) equals SCP.

SCP divided by total weight is a percentage. It will work with metric or US measure-just use consistent units.

You can play with this to see what combination of SA,weight,RM will actually have a chance of working.

This also works(with other indicators) to predict "foilability" but was designed to predict upwind planing.

Another problem with planing monohull keelboats is the relatively wide hull that is generally thought to be requied. With a potential keelboat foiler you go with a 10/1 L/B ratio to start with(MAX width) so weight is already reduced a lot.

You can see below that its a bit tough to get good numbers.......


Numbers for a foiler-for a planing hull weight would have to increase but there is enough margin for that, I think:

---LOA 24'
---LWL 24'
---Beam 18.6' (overall, incl. racks)2.4' at waterline
---Draft 6.5' keel,rudder retractable
---Sail Area 586sq.ft. upwind and downwind (planing boat would need big spin)
---Boat weight,incl. rig and ballast-1100lb.
---Ballast 490lb. (110° canting keel)110° canting keel wouldn't work on a planing hull so keel might have to be deeper @ 55-60° cant.
---Displacement (incl crew)-1420lb.
SCP/Total weight=42%


And before you say that it doesn't fit the rules. So what? Rules are meant to be changed when they hold back developement with artificial restrictions.

It's only a model

The tips presented here will be those that I know work and that have been extensively tested on the water and in testing of two F3 hydrofoils side by side and Dr. Bradfields modified Flyer hydrofoil.

These foilers use fully submerged foils as opposed to surface piercing foils and the major advantage (in rc models) seems to be the fact that they generate their own stability. The more wind pressure ;the more stable the boat is.The F3 has been sailed in winds well over 20mph and the Flyer? in over 30.Fairly accurately ESTIMATED boat speed of the F3 in 16-22mph of wind=20mph.In 5-7mph of wind boat speed was ESTIMATED at 10-12 mph.

No other multihull available anywhere has this kind of automatic hands off stability system. On "normal" multihulls (F48,mini 40 and multiONE) immense concentration is needed just to keep the boat upright in medium to heavy air. The Bradfield type foiler ,like the F3, virtualy eliminates all those hassles and allows the skipper to just enjoy the speed without the capsize worry. A boat like this can still be capsized if it is set up incorrectly(set up should be a one time thing) or if too much sail is used for the conditions but I can supply a sail area guide that will eliminate that problem. And if you use the same rig as the F3, Flyer or X3 you won't need multiple rigs since those rigs reef thru out the windrange .

Another thing:the F3 type foiler can carry its "A"(unreefed) rig in higher winds than any other multihull because of the automatic stabitiy system but at some point sail will have to be reduced.I have a guide to knowing exactly when...

Foiling occurs on the F3 in 5-6mph of wind.Most of this is based on the F3; some ideas relating to the X3 retractable foiler are presented though that boat has not been tested yet.

Design Facts:

1) the quarter chord of the two main foils should be located so that they carry 80% of the weight and the rudder t-foil carries 20% of the weight. This generally results in a rig further forward than is "normal" on an rc multihull because the quarter chord of the vertical fin is, by necessity, in the same place. That is also the location of the CLR of the boat for balance(weather vs. lee helm)considerations.

2)A single cross arm is all that is necessary but it must be exceptionally stiff torsionally.

3) the center line of the outboard foils is ideally located about 1.07 times hull length apart centered on the main hull athwhartship. In the F48 class this is not possible and results in the hydrofoil for the f48 having to do slightly more work than that for the F3. In the multiONE Class while loa is one meter BOA is 48". The wider the boat the less the loading of the foils.In many tests the location of the vertical fins so far outboard has not affected tacking ability in the least; a foiler on foils will tack at least as fast as a fast monohull...

4) The automatic altitude control system depends on two"wands"which are straight or curved thin carbon tubes or rods that drag in the water. Before foiling the water pressure pushes them aft forcing the flap on the hydrofoil down to the high lift position. A spring or shock cord is attached to the wand so that as the boat rises the bottom of the wand moves forward neutralizing the flap on the foil or even creating negative lift.This is how the boat develops its own righting moment: the diferential lift required to create and maintain the exact right amount of lift AND righting moment is created by the movement of the wands connected to flaps on the two main forward hydrofoils: it is 100% automatic requiring no radio control!

5) The F3 will foil in very light air but because of the automatic altitude control system there is a lot of drag when not on foils.The "wands" can be removed in light air drmatically reducing drag since the flap is not then being automatically pushed into a high lift position. Or this type of foiler can be designed to use retractable foils which has not been tested in the water but since the foil system is identical and the rotation system so simple it should work but as yet this remains untested. F3 type foilers have been tested with no wands for light air.F3 One Design races would not be held in less than foiling conditions but F48,mini 40 & multiONE races will be held in very light conditions so it could pay if you consider an F48 size foiler to go ahead with a retractable system.

6) the main foils are installed as previously mentioned with a +2.5 degree angle of incidence relative to the flight waterline. The rear t-foil is set at 0 degrees.

Mainfoil area should be determined as follows:For a weight of 8 pounds the two main foils will lift 80% or 6.4lbs.; 3.2 pounds each. They require an area of 17 sq.inches to do that or .188lbs per square inch. Note that this is just to make calculation simple and does not reflect the ACTUAL loading of each foil since ,in developing righting moment, they are much more highly loaded. A Foiler should be designed with approximate 200 sq. in. of sail area per pound of weight. Of that sail area the MAIN foils should carry 49 of sail area per of foil area.(Divide Sail Area by 49 to get mainfoil area=both foils; then divide in half for the area of one foil.Try to achieve the loading and sailarea for the foils and displacement of the boat.

In summary:

A).188lb.s per sq. inch loading of the main foils only -just using 80% of the boats weight.

B) 49 sq. in. of sail area per sq. in of main foil area. This can be varied a little and is applicable from a multiONE to a two meter.C) this will produce a boat that will take off in light air.(5-6mph)
The rudder t-foil should be 50% of the total of both mainfoils or slightly less.(Equivalent to one main foil works well)

7) The amas on a foiler the size of the F3(LOA 56") are 36" LOA with an 18/1 beam to length ratio and total buoyancy of 7 pounds. They are not capable of flying the main hull and do not need to be.Amas for an F48,mini 40 should be about the same size due to the proportionately narrower beam. For the multiONE they can be directly scaled down.

8)On the F3 the foils fit in trunks in each ama and that requires that not only the tube comprising the cross arm be exceptionally stiff torsionally but the joint between the ama and the cross arm needs to be exceptionally stiff. On the retractable design (untested as yet) the foils are mounted within carbon tubes that fit within bearings into another carbon tube allowing the whole foil/altitude control mechanism to rotate.Viewed from forward the foils rotate like airplane propellers toward the main hull untill they are vertical. The lower portion of each foil then acts as lateral resistance for the boat in light air.

The mounting of the rotational part of the the foil system allows the foil to have a zero degree angle of incidence when the foil is vertical. While I haven't tested this on the water yet I'm confident that it will work since it is so simple.The one downside may be the area of foil still in the water. The idea is to eliminate any need for a daggerboard when the foils are retracted by using the foils themselves as lateral resistance when they aren't being used for lift.


You don't need a retractable system to enjoy sailing a foiler as described above; it takes off in such light air that you'll be foiling most of the time anyway. The only benefit to a retractable system is in light air or transitional foiling conditions(under 6mph wind) and the only benefit is in a class like the F48,mini 40 or multiONE in light air racing.

For anyone interested I can answer any questions and provide sketches of the wand system but the basics are here-you can design a foiler with the information provided above....

Oh, and it's only a model