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Old 5th June 2009, 06:32 PM   #81
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Eric
There isnt a shred of evidence to say a "rough" fin gives better initial acceleration and ultimately more drag . Infact evidence is mounting suggesting exactly opposite. Perhaps we have learnt to sail with "rough" fins ???
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Old 5th June 2009, 07:40 PM   #82
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The theory is 100% spot on! No doubt, I am talking about human limitations.
In theory when the windsurfer is loading the fin perfect and pushing the board just on the surface it will give less drag

But hey, I can't do that, OK I am not the fastest windsurfer in the world. I am 99.9% of my time in awfull speedconditions. With a polished fin I don't have any margin, every mistake means End of speedrun. Now I don't have time nor patience nor money for such sailingstyle.

Also the gear especially the sail has some comprimizes in the run up for high speed, especially with my lower weight, the moment of inertia doesn't work out 100%. When your fin has no room for mistakes this means you have to easy down and NOT put pedal to the metal. Windsurfing is sooo dynamical, this fact has to be considered when going for worldrecord speed. But also when just freeriding or lower speed.

I do believe we windsurfers can go beyond 50kn, but it takes very good training (especially mental). Me and many other try to get the holy grail, but it is just such a long road.
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Old 6th June 2009, 12:19 AM   #83
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Its always worrying (or should be) when anyone claims "theory" is 100% spot on.

First of all thats why its called "theory" and not fact....

Secondly; history is littered with in theory"facts" going wrong. Titanic and icebergs; space missions falling to earth in fireballs etc etc.

In theory large bumble bees cant fly !! In theory dolphin max speed is 20knots etc etc.

AND there is NO EVIDENCE to support your 100% right theory anyhow. Much of the "current" theory says the opposite !!!!

I`m not a slow sailor (but I`m not that fast either) (Vmax 42 knots) and I`ve been sailing 20 years +. I can not tell difference in polished to mat fins !!! Spin out or top speed !!! (Currently using polished but not waxed) (ie naturally shiny !!!)

Diffence between polished/mat is at best neglible.But try using ventilated fin. You CANT spin the damn things out (Well you can but its a real effort !!!) But they are slower.(I think, not 100% certain though, NOTHING is 100% certain, well nearly nothing !!!)
Get my drift ???

Try getting someone else to put your fins in Eric. See if you can actually tell ???!!! Are you 100% certain you could !!!!

As some other poster mentioned perhaps you learnt to sail with "matt" fins. (Think we all did !!!)
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Old 6th June 2009, 07:03 PM   #84
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This morning I met Stephane and Samuel Moscher, founders and managers of Select. Both told me that they preferred by far wet-sanded over polished. This is based on tank tests they did 15 years ago and since confirmed by continuous experimentation. Their explanation is basically the same as in post #3. A matte surface is easier to wet and a wet surface behaves better in water. Difference in friction drag is negligible or in favour of wet sanded. Interestingly, Select is also wet sanding high performance fins horizontally with 240 grit. Samuel Moscher said that phenomenons such as cavitation might start occurring at 45~50 Knts, but this was just his intimate conviction.

About fins I trust those guys more than any old or modern theory, or comparative tests I could do by myself. Stephane Moscher said that this would probably apply to hulls as well but he had no experience or data about it. Of course someone may invent a surface finish (diamond-like carbon?) that will make it polished and wettable and fast and controllable in a broad range etc, but apparently it has not happened in windsurf yet.

Last edited by Farlo; 11th June 2009 at 02:21 PM.
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Old 6th June 2009, 07:33 PM   #85
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Did Stephane and Samuel mention how much cheaper it is to not bother with final polishing of fins ???


NASA must be etting it all wrong these days !!!
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Old 6th June 2009, 07:55 PM   #86
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Stephane just said it was not any kind of sandpaper. I forgot to mention sanding horizontally from head to tip. Manufacturing cost certainly plays a role in choosing a certain design, but Deboichet has taken a similar option, and I wonder how Kashy fins look like, haven't seen any. Price should not be a limitation there.

Last edited by Farlo; 6th June 2009 at 08:00 PM.
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Old 6th June 2009, 09:19 PM   #87
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did the select guys tell you why their fins always hum and vibrate and need the trailing edge sanding down? or why i had 3 of the viper speed fins of 28cm length breaking at the base. or why i used to have to buy 4 or 5 fins to find a good one? or why as soon as they try a tectonics or a c3 people change and dont go back to select?
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Old 6th June 2009, 09:53 PM   #88
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Well they are making fins every day for years and I guess they are more qualified than you and me. Many people I know are happy with their products. Certainly other brands are doing excellent fins, so check whether they deliver them matte or polished. You will learn much more than by reading articles from Lockeed Martin.

Last edited by Farlo; 11th June 2009 at 02:21 PM.
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Old 6th June 2009, 10:12 PM   #89
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So because mat finish fins sell best they must be best ??? Sort of self fullfilling prophecy.???

Suspect Lockheed etal know a damn site more about aerodynamics/hydrodynamics than any fin manufacturer. Even those claiming to have done tank testing 15 years ago !! Think that says it all !!!!
BTW select fins are not really a good exmple to hold up;

It mght well be mat fins spinout later/ have better lift drag ratios/offer less drag etc etc but FACT is there just isnt any factual evidence to suggest any of claims made !!! Its another part of WS folklore ; like cutouts reducing drag ? When acually they increase it !!!! We just play into the BS. (Cut outs do offer advantages but NOT reduction in drag as normally claimed but thats another argument !!!)

If claims made for "mat " fins are true why do we not see use in commercial fields ??? (Eg Hydrofoils ; aircraft wings ? ???
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Old 7th June 2009, 12:33 AM   #90
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It seems that we are rounding in circles. This is what the guys at Select told me and I've nothing to add. I'm not impressed by references to hydrofoils or aircrafts or guitars which do not really apply to windsurf. Now it could very well be that a given fin performs better when polished. If you have one keep it preciously. I'm leaving this post, bye.

Last edited by Farlo; 6th November 2009 at 03:30 AM.
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