The wider top portion of the surface piercing foil means that the boat will reduce lift within a shorter distance as the boat rises compared to a constant chord. A constant chord foil of moderate or narrow chord length would fly really high. Well this is some of the reasoning behind other surface piercing foilers.

If I understood correctly, you are saying that the progressive reduction of foil chord reduces the amplitude of up and down movement. Makes sense to me.

I saw the photo in the foiled Moth of your construction (I guess) and would like to ask something:

Could you elaborate on the reasons why many Moths use eliptical tips? In the US there is a tendency to make them square.

Thanks,
Luiz

Some of the surface piercing moths have eliptical tips although none of my own T foilers have had eliptical tips as yet. I have a new moulding for and eliptical tip to match the 120mm hydrofoil I use. These reduce the tip vortex making for more efficiency/less drag and more speed.

Just wishing to wave the flag for Joddy and George Chapman who have developed Ceres, one of the most well sorted foiling cats I have ever seen. Regularly sails at close on twice the wind speed (see the results for sail number 141 at Weymouth Speed Week 2002 SpeedSailing.com) A few details about Ceres and links to further information.Ceres .

Regards

Nick Povey

I was playing on a foiled "Sky Ski" board yesterday. The foil on this contraption is about 3' long. It is amazing how the slightest movement will make it jump one way or another. Just taking your hand off the rope to scratch your nose would mean an instant wipeout. My friend is better at this sport and can control it easily, but it does take a long time to master. I like to refer to the control as "touchy-feely". Not sure how different the foils on a cat would be, but I think that I would want a computer doing the thinking for me to maintain control.

Jack Hoying
Fort Loramie, Ohio

Jim,
Are you seat belted in? How is a wipeout? Looks like it might be exciting.

Yes, you do have a seat belt on. Wipe outs are usually easier on the body than regular water skiing. The nice thing about it is that it doesn't take a whole lot of physical effort to get up and to ride it. This makes the learning process a whole lot better, since you can try a bunch of starts without being to whipped to hold on to the rope. After you master the starts, you pop up with ease. Here's a couple photos I took of my friend trying to do 360s, both of which were unsuccesful.



For more information, do a Google search for Sky Ski, or Air Chair (two brand names)

Jack

FYI, here are the cavitation diagrams for the E817 and H105 plus a NACA 6-series section. These data are not found on the NASG site.


Ventilation, of course, is a different animal. You need to have separated flow to cause ventilation, so that may be a good place to look. I don't know why the NACA 0012 would be particularly ventilation-prone - I'd expect it to be more resistant. But maybe there were some details of the actual foil configuration that caused the flow to separate.

Thanks Tom,

Could you please add a Clark-Y shape to that interesting figure? My original NACA 0012 aluminum struts would ventilate badly when presented at high speed at any angle more than a few degrees to the water: These Aluminum struts were probably not really NACA 0012 because they had been extruded too thin, and had very sharp leading edges.

I read that the Orma 60 tris covered their foils in the dock after the Transat. Does anyone know of a new idea or concept that could be so important to justify the covers and extra work to hide the foils? I don't believe it was just for protection.

Thanks!

I also noticed that the new planing/foiling cat from France with curved lifting foils placed poorly: He hit something and damaged one foil early on. Did this make a big difference? Does this concept really work?

Yves Parlier hidroplane cat arrived last in the ORMA 60 multihull class, hardly a success. Lets see how it does in Quebec-St.Malo.

He said the following about the race (bad translation-sorry)

"This was the worst crossing in my life. From Beaufort 3-4 the spray flew permanently. Very soon I was completely wet, despite the sophisticated equipment. I knew it would be tough, but I didn't expect this. I thought I'd be able to sail at ease with the boat under control. But after a favorable beam wind tore one of the mainsails my morale was destructed. The other hull jumps on top of the waves transmiting chocks and vibrations to the craft in the limit of bearable. Apart from that, the lewward sail is hard to see and the craft is difficult to trim. I give myself two years to tame the boat and extract all of its potential, doubtless more for record breaking then for Grand Prix. I was doing 27 knots in Cape Cod and the highest speed reached was 35.5 knots."

Luiz