Tornado-Cat

The winning foils

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Foil wave drag is addressed (among all other foil drags) in a Cheasapeake workpaper about the Moth.

It is a few years old document, but still interesting, cannot find it among the hundreds of CFD  pdf I have on my laptop. 

Should be findable on a Moth thread.

Regards

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^ Found it, thanks - that's a really interesting study. Wave drag increases as you get closer to the surface - it's the deformation of the water surface that I was guessing about - but according to the study, the reduction in drag resulting from having less of the foil mast submerged more that offsets it, at least on T-foil set ups like the Moth.

https://www.scribd.com/document/213283260/International-Moth-Hydrofoil

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Note that ETNZ foil was sailed with the tip horizontal.

The kink enabled the horizontal tip to be both deep & nearly half of the span vs Orifice who did have a similar tip but much smaller, with most of the foil operating much closer to the surface & on an angle.

 

AC TEAMS DAGGERBOARDS.png

@darth reapius image :)

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Thanks Hoom,

If ETNZ used to sail with the tip horizontal, then my former remark is totally irrelevant.

Sorry, I apologize for this disinformation, just forget it.

Obviously, the reverse engineering of winning foil is not a trivial exercice.

Regards

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From here: http://www.sailingworld.com/kiwis-cup

“Our daggerboard tips were angled down more than any of the other teams,” says ETNZ coach Ray Davies, “which made them faster upwind but harder to sail, but our control systems were better and we were able to achieve the same stability with the faster foil, and that’s where we were faster upwind. We were able to sail higher, with more windward heel, which gave us more grip on the leeward daggerboard.”

 

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10 minutes ago, weta27 said:

From here: http://www.sailingworld.com/kiwis-cup

“Our daggerboard tips were angled down more than any of the other teams,” says ETNZ coach Ray Davies, “which made them faster upwind but harder to sail, but our control systems were better and we were able to achieve the same stability with the faster foil, and that’s where we were faster upwind. We were able to sail higher, with more windward heel, which gave us more grip on the leeward daggerboard.”

 

I think it sums up pretty well the advantage. And, iirc, the control system was a dot to follow with a finger  on a screen. Not forbidden but a serious loophole.

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50 minutes ago, Tornado-Cat said:

I think it sums up pretty well the advantage. And, iirc, the control system was a dot to follow with a finger  on a screen. Not forbidden but a serious loophole.

Inspiration

shuttle_FDAI_flight.jpg.d84b1b37f4e06035e0130fcdedad654a.jpg

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2 hours ago, Tornado-Cat said:

I think it sums up pretty well the advantage. And, iirc, the control system was a dot to follow with a finger  on a screen. Not forbidden but a serious loophole.

I don't believe it was a touch screen, it was a joystick with a dot on a screen... similar tech to what was used to test pilots in the 40s

 

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On 9/6/2017 at 3:27 AM, Erwankerauzen said:

Foil wave drag is addressed (among all other foil drags) in a Cheasapeake workpaper about the Moth.

It is a few years old document, but still interesting, cannot find it among the hundreds of CFD  pdf I have on my laptop. 

Should be findable on a Moth thread.

Regards

Bill Beavers analysis of the Moth below:

CSYSPaperFeb09 Beaver paper on Moth.pdf

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That reminds me of this beast, a Stecometer (the page is in Czech), for precise measurements on photos (stereo pairs). Two wheels for each hand and one for each foot moved two images (one for each eye) while the operator looked through the binoculars, trying to place dots in marked locations in the images. The hand wheels could also be pushed to give a fast motor driven movement for getting around the image faster. Required serious coordination to be efficient.

Stecometer.jpg

 

 

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