FOILER 1 Grand Prix

[dimitarp]

What is the question in this discussion. Everyone write everything that find annywhere?

[RHough]

Originally Posted by John ilett

The picture shown is Moth class world Secretary Mark Robinson sailing a Prowler. The boats only use the windward heel when sailing upwind. This photo shows Mark reaching.

If the rig carries weight then the foils carry less so the sectional shapes may improve with less positve flap.

Below Rohan and Mark sailing upwind.

Good point John, I missed that he was on a reach. I was just happy to find a photo that was head on enough to look at the angle. My mistake.

Most of the photos I've seen show the boats heeled to weather in lower range of wind speeds (judging from the water state), I haven't stumbled across a photo that shows the angle when the boats are sailing upwind in a breeze.

Scroll down to the picture just above the beautiful woman:
International Moth- UK Homepage
http://www.int-moth.org.uk/

[RHough]

For what it's worth, I think I can explain the improved performance from heeling to windward.

When on the foils the boat heels around the vertical centre of pressure of the foils, some distance under the water.

A non-foiling boat heels around the centre of buoyancy.

The distance between the crew's CG and the pivot point is much greater on the foiling boat. With the angle of the racks, the crew might be 45deg above a horizontal line through the pivot on a foiler and only 15 deg above on a non-foiler.

Maximum RM gives higher sail carrying power. Maximum RM comes when the crew cg is on the horizontal line from the pivot.

If the angle to the pivot is 15, you could gain 3.5% in crew arm by heeling 15 deg to windward. For a non-foiler that would be about 23ft/lbs of RM for 165lb crew.

If the angle from the crew cg to the pivot is 45, heeling to windward reduced the angle to 30 and increases the arm by over 16% and would add about 108ft/lbs of RM for a 165lb crew.

On a Moth rack the crew arm is about 4ft, giving a RM of about 660ft/lb

The windward heeled foiling Moth could have 768ft/lb of RM (the 16% gain).

On a 10ft sail arm the SCP goes from 66 to 76.8. For a 220lb boat and crew that moves the power/weight ratio from 30% to almost 35%

There is absolutely no doubt in my mind that a 5% gain in SCP to weight would increase upwind performance.

It's the ratio of rack width to foiling height that makes it work.

As the racks get wider, the gains from windward heel become smaller.

Check this out if you're interested in the Moth:
Mon Moth à moi....
http://moth-pour-tous.over-blog.net/

Check this out:
International Foiler Moth - Bladerider
Address:http://www.kasail.com/sailing/bladerider.html Changed:3:02 AM on Thursday, May 4, 2006