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Topic Review (Newest First)
22nd May 2008 05:53 AM
Unregistered What happens when you tack then?
21st May 2008 02:42 AM
PGVirtual It is true that you can use the Lessacher assymetric fins at least a size smaller than regular fins. Thus, would it be possible to make an assymetric 70 cm Formula fin with the power of an 80 cm fin, for absolute lightwind (and maybe olympic Formula Windsurfing)?

Anyone up for the challenge?
17th February 2008 04:58 PM
Lessacher A very long time ago worked I a board how a fextail. The last 70cm were in acryl, so
I could see all it what with the fin happend. I know what spin out is.I could all it see,
What I now work is only that what I tried good 20 years. Why work I asymm. fins for
tour and retour in one fin? No spin out, very fast and and they can be always 15%
shorter than other fins. Why are weedfins so fast ,or faster than upright fins.? Nobody
would hear that. Finish of the fin.? Look the fin of Martin. What is lift? How many % come
from the front, or from the bending fin.? A never ending story.
Wolfgang
16th February 2008 01:58 PM
Unregistered but how does it line up against other fins?
16th February 2008 05:36 AM
GEM Not sure I agree with you, Peter. I agree that the load is distributed, but the ENTIRE visible section remains completely straight, at least to my eye. Perhaps a slower motion / less distorted image would show more flex, but to my eye the part of the fin that is bending is not in view.
15th February 2008 01:27 PM
pfaffi Sorry, mistake in my last article:
Wrong: However it is difficult to make the fin in the tip so soft to have in this section some remarkable twist.
Correct: However it is difficult to make the fin in the tip so soft to have in this section some remarkable flex.
15th February 2008 01:14 PM
pfaffi The camera was mounted at the rear end fixed with the two fin screws by a bar. The lens fixed 1cm under the planing water level (to avoid view of all the airbubble under the board running through) adjusted to look to the fin tip which a have coverd with a orange self addhesive film for better view. By this setup you can not see the full fin length up to the basis, app. 60% of the length.
To GEM: The main flex of my F1 fin (and all other brands) is beginning from the basis up to app. 50cm of length. The tip (last 20cm) will not flex to much because of relative less forces in this section. Dont forget, the bending force is caused by the uniformly distributed waterload. So at the tip end no load and than the load is permanent increasing up to the basis. I found the sum of all water forces on my fin is only a little smaller than my body weight. However it is difficult to make the fin in the tip so soft to have in this section some remarkable twist. Difficult because there will be not to much reinforcment in there anymore and if you tough the ground or catch a fish the tip will easily brake.
To Ion: You are right, the camera is mounted solid. My F1 fin in H+ is compareable to a R19 S! My F1 S is flexing up to 30cm one side! I think except the starting and pumping movement the fin is moreless not moving left/right in the water. So the left/right movement you see on the video is caused by the longitudinal walking of the board.

I will look for some Photos showing the arrangement and will do a short photo video and place it in Youtube. Will be anounced!

Peter
15th February 2008 10:11 AM
GEM Interesting thing is that the blade itself doesn't seem to flex at all! So much so I have to wonder about the stability of the camera mounting apparatus. If it is in fact stable, which I suspect it is, then it would seem that ALL of the flex is at the base. Given that the fins I've seen snapped off broke at the base, I suspect that's true.

Leads to the question - are fins overbuilt on the blade, but underbuilt at the junction of the base and blade?
15th February 2008 04:35 AM
Ian Fox Warning !!
DON"T use a headset with the volume turned up LOUD
trying to hear what Pfaffi says in his introduction !
- or turn it down real quick once he hits the wet stuff !

But it's great footage and actually quite well done considering all the factors
and as a "home made" video analysis ! Well done and quite interesting.

Pfaffi, if we understand correctly, what you are suggesting is this video is using an extra stiff F1 FW fin (?) - in which case a video of some other really soft, flexy FW fin would be even more dramatic. (didi you try or make a video of super soft Deboichet etc?)
(we've seen some pretty wild still photos of FW flex in the past ).

Hey Steve, due to the relative smooth action between the fin movement and the reference (camera) it's pretty clear the camera (or sensor) is solid mounted to the board, so the flex we are seeing is the relative variance between fin and board, not free floating camera and fin. Agree, the railing of the board can influence this, but what we are looking at is the relative flex of the fin vs the datum of board.

Maybe Pfaffi can post up (or email us) some pictures of his board/video set up !

Cheers ~ Ian
15th February 2008 03:59 AM
steveC I would imagine that its tough to get a clean and crisp video result most likely using a very small lens assembly on a mounting with tons of turbulence coming off the planing surface of the board and water.

Still though, I'm curious about two things. I often see formula boards very tweaked (port and starboard) in their planing mode, and I wonder whether that might have influenced the visual image of the fin in any way. Secondly, I wonder about the camera mount design and its ability to maintain parallelism with the water surface at all times. Was it gimbaled in the mount in some way to sustain a true horizon? Or, maybe, was it just rigidly mounted perpendicular to the board?
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