Bi-foiler with "Power Foils", idea that MIGHT add more "High" to Performance

One of the great advantages of a boat like the Hobie trifoiler, Rave or Dr. Sams new Osprey is that that dual wands operate independently allowing the boat to develop all its own RM without input from the crew. Hydroptere and every surface piercer I know of develop RM differently by increasing the separation between the center of lift of the main foils and the boat CG as it heels(leeward foil develops an increasing amount of lift). Hydroptere uses movable ballast as well.

I've been toying with the idea of a hybrid: a "bi-foiler" that uses retractablesmall foils in each buoyancy pod-primarily in heavy air upwind. The point would be to increase the RM of the boat boosting upwind speed. The foil would be deployed in such a way as to hold the boat at a designed angle of veal heel along WITH crew participation. A target might be to add 50% to upwind RM and that would require a foil(actually one foil each side-only one used at a time) about half the size of a Moth mainfoil.

Disadvantages include the fact that two foils would be required and the additional weight. The gains could be appreciable, allowing a substantial increase in SA.

In light air the foils are retracted but the boat still has all the extra SA. So the gains would be not only upwind in heavy air but downwind in every condition and upwind and downwind in light air due to the extra power.

Takeoff would be significantly earlier than a "normal" bi-foiler....

Bradfield and Ketterman have already proved that the extra drag of a third foil is more than made up for in moderate to heavy air by the virtually unlimited rm available with their system. I think that it would be ideal to have these "power foils" able to be deployed without an altitude control system-a preset angle of incidence might work.

What do you think?

International 14's

Most people probably know that the 14's are using a rudder foil that supports 25-30% of the sailing weight of the boat. What some people don't know is that the FIRST two person bi-foiler in the history of the world was an International 14 sailed in 1999 within months of John Iletts first sail of his foiling Moth.

Many people may not realize that this first foiling 14 also used MANUAL altitude control using a twist grip tiller operating the flap on the rudder foil.

Another first for David Lugg and Alan Smith who developed this boat.

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.

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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!

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.

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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.

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:




Osprey
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- 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.

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.

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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.......

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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.
crew-320lb.
D/L=45.6
SA/D=74.3
SCP/Total weight=42%


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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.