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Topic Review (Newest First)
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| 28th June 2012 01:31 PM | |
| Lessacher | There the cut out is 3cm wide, so is the end of the fin 3cm behind the cut out,the water goes a little earlier through the cut out. The end of the fin comes a little to late. 3 cm.to late. Wolfgang |
| 28th June 2012 01:20 PM | |
| Lessacher |
You make a jump or you surf over choppy water. If you come in the water ,two things. Leewards pressure, On the other side from the coming in the water more vavuum. That takes a mixture of air and water from the boardbottum to the end of the fin, and goes down to the tip,make bubbles and sometimes spin out. Have you a cut out at the base of the fin,there goes the water and air mixture in an angle of 30-40° behind the fin from leeward,the pressureside, to the other side aned take all it away from the fin, so it cannot come something to the tip.If you saw what in Netherland happend ,sorry I stopped in the half, so I cannot say what it was, but it is to easy to say it was the Windsurfer. I hope that some of you try to make such a cut out at the base,take a old fin and try it.It is not so that I want to work for you here fins, I want only to show some People what we can do against spin out. Please look here: www.cameraid.com/Lessacher/tech.html There can you see the cut out. And how the diagonal concaves are. Wolfgang |
| 26th June 2012 04:31 PM | |
| Lessacher |
When I work speedfins between 18 to 28cm i work they very stiff so they cannot produce a lot of twist and flex. When,than a little flex for lift and not 2 things ,flex and twist at the same time ,one works against the other. A twisting fin need more power for flexing. That reduce the speed. I worked a fin with 20cm for one way. The idea is, to work flex in the fin,for a little lift of the end of the board.The fin stay in an angle of 10° to the left or right side.So you need only the half power for to get flex and later the lift. The power you need for flex ,reduce the speed a little. I work only 100% carbon fins,the reaction of carbon is the shortest,I know,( bending and back). I worked a fin inside only with rowings.I lay the rowings in epoxy and do powder of ceramic around the rowings. that makes the fin stiffer than all the other things. So I try and try. Wolfgang |
| 26th June 2012 04:19 PM | |
| Lessacher |
When I work speedfins between 18 to 28cm i work they very stiff so they cannot produce a lot of twist and flex. When,than a little flex for lift and not 2 things ,flex and twist at the same time ,one works against the other. A twisting fin need more power for flexing. That reduce the speed. I worked a fin with 20cm for one way. The idea is, to work flex in the fin,for a little lift of the end of the board.The fin stay in an angle of 10° to the left or right side.So you need only the half power for to get flex and later the lift. The power you need for flex ,reduce the speed a little. I work only 100% carbon fins,the reaction of carbon is the shortest,I know,( bending and back). I worked a fin inside only with rowings.I lay the rowings in epoxy and do powder of ceramic around the rowings. that makes the fin stiffer than all the other things. So I try and try. Wolfgang |
| 23rd June 2012 06:12 AM | |
| Lessacher |
The asymm. fin was for one way over 1km. 20m in front.But retour slowlier. So I said,okay,to be the half of 20m in front, that are 10m in front,so or so, I am the first. But how. The conave only to the half,from the base to the middle,and for retour on the other side from the middle to the tip. But what happend? I made not 10m, always 20m,but why? It works always the concave leewards, the concave on the other side shell work retour. The concave on the vacuum side reduce the vacuum,that could I not know, but it was so.The concaves reduce good 5% of a normal profil. A thinner profil is faster.But I work the nose thicker, thats better for upwind. Through the concaves is a speefin 2 knots faster. That works at all fins. But nobody want to know that. A assym.fin for one way is leewards thinner than on the other side, And the nose? Leewards is the angle sharper, there the profil is thinner,thats better for speed. On the other side is the profil normal,the nose angle is not so sharp than on the otherside.There you can nothing reduce on the vacuum side,is such a fin a little slowlier.than my fins. Wolfgang |
| 22nd June 2012 05:58 PM | |
| Ken |
Lessacher and unregistered, Both of you make good points and I think my issue with the Drakes is the exactly Lessacher's point regarding the thick/thin nose. The Drakes have a thin nose and in a speed trial, probably are a bit faster than a fin with a thicker nose. However, a faster fin that spins out frequently is not a faster fin, it's a pain in the ass. In chop, the Drakes were particularly bad. My skills are pretty good having windsurfed for the last 28 years and have raced the entire time, but on average only 3-6 regattas per year. Last year, I had 89 days of windsurfing. The other side of this issue is the type of sailing one does. 95% of my windsurfing is freesailing where I most commonly head up and bare off rather than just reaching. Since I try to point as high as I can on my slalom board about 1/3 of the time, I am pushing the fin to it's limits. I typically am in gusty conditions where staying on plane is ALWAYS an issue even on very windy days, so a larger fin with a little more lift helps keep things going. If I sacrifice some speed, so be it, it's worth it. |
| 22nd June 2012 03:52 PM | |
| Unregistered |
Ken A thicker foil does have a wider tolerance with respect to varying angles of attack. (a thicker leading edge will be less critical to changes in AoA) so like I said earlier a thicker foil will initially give beter results and feel less prone to spin out(and recover more easily) but like many things in life its at a cost somewhere else. Might well be you are actually a bit slower with your new fin and other sailors might find the drakes spin out less when fully maxed ??? It all depends on the sailors ability;conditions and what they want to achieve. V max. Vmg.playful feeling.. control ??? Very often a fin that has to be coaxed initially (ie bear away; accelerate and gradually increase load) will give higher Vmax but not everybody wants to sail like that and in some situations you simply cant.. Thats why its very difficult to give broad assumptive answers.. We all give answers based on our own circumstances and limitations.. Basically (IMO) if you want to go really fast fit smallest thinnest fin you can just cope with at slow speed; coaxing into life slowly... When its up and running it will be great. (Highest Vmax) If you want to simply go and arent concerned about Vmax fit largest fattest fin that you can cope with at highest speed you are likely to achieve.(Highest VMG) Somewhere between the two is freeriding. (and wave sailing ???) |
| 22nd June 2012 01:54 PM | |
| Lessacher |
Only nose and what at the end of the fin happend,that should we see. Why work I cut outs at the base.I saw that water and air from the bottum of the board want to go down at the end of the fin to the tip of the fin. The bubbles are a little brake. We go with an angle of 10-15° through the water..The water must go through the cut out and in the same angle behind the fin and cannot go down.So you make jumps and nothing can go down at the fin. Wolfgang |
| 22nd June 2012 11:52 AM | |
| Unregistered |
"Please dont write over long or short fins. Flex or twist,Thick or thin fins. Sanded or not. G10 or carbon. Please only what a spin out is, I wrote what I saw, and what I did to eleminate spin out.Sorry, that write I tomorrow. Wolfgang" Think its good that we try and keep things simple butt all parameters you mention have influences on spin out. Putting it simply though (IMO) spinout is what happens when fin stalls; ie when it stops opposing downwind force and lets board slip down wind. Reason for stall are many fold and inter related and hence diiicult to quantify. Aeration is simply but one of them. (But cavitation is not) If you are spinning out very early try a thicker fin.(It will work at higher AoA encountered at slow speeds.) If you spin out at speed try a bigger fin but check you have not affected your Vmax. ??? |
| 22nd June 2012 10:25 AM | |
| Lessacher |
Please dont write over long or short fins. Flex or twist,Thick or thin fins. Sanded or not. G10 or carbon. Please only what a spin out is, I wrote what I saw, and what I did to eleminate spin out.Sorry, that write I tomorrow. Wolfgang |
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