Isonic Theory ?? Anyone??
Quote from website (Isonic)
"The theory behind the concept: where the water first touches the board, this is where lift is greatest. Where it leaves the board, this is were lift is minimal yet drag is still strong. So effectively, you want more width at the leading edge of the planing surfac and less at the trailing edge of the planing surface. Based on this idea, the concepts of cutaways (Starboard innovation 1999), side cuts (Starboard innovation 2004) and tail wingers (Starboard innovation 2007) were already born. For 2009, Starboard introduces double wingers."
a) How can edge be less at "trailing edge" than leading .?
Surely any change in width at rear moves trailing edge forward ;ie leading edge at wider point becomes trailing edge ??? (Can you possibly have smaller trailing edge than leading ???)
b) Any cut outs./wingers increase length of trailing edge not reduce it ??? (ie shortest trailing edge would be straight line ???)
Thought idea behind cutouts was to reduce lift but at cost of extra drag ? (ie longer trailing edge but reduced lift to help control at top speeds ??)
I couldn't help noticing you're pondering over several fundamental questions in the last few days, starting some threads.
You haven't clocked much sailing lately, have you? ;-)
Wish you more wind -also to myself, but it's freezing where I am :-(
I don't agree with you,I think This problem should be further analysis.
Yep you are right not getting enough TOW these days.Freezing everywhere I go !!
Warming up soon though ???!!!
To be honest thought Forum has got a bit boring/slow these days. Not like past with LeeD etal. Its not getting anything like turnover it used to and everybody is just so nice with each other ! (Apart from Crazy awper who`s smoking intead of sailing ?)
Missing LeeD, eh? He was entartaining ocassionally. May I recommend talking to Sinbad/Swiftsailor now and then (or one of his many incarnations/voices ;-)
You may also want to visit Boards UK forum (you're from UK aren't you?). Good equipment and spots info, and just general banter, sometimes heated discussions and abuse ;-)
Well guys, LeeD is alive and well on iWindsurf.com. Normally he posts on the Southwestern US and General Forums there.
Nope I`m not missig LeeD.
He made Forum interesting with his own brand of BS but reckon there`s plenty on here without him.
Thanks for advice Screamer.I occasionally post on Boards Forum already.
Would be good to record wind strength/sail size relationship on Forum and that which actually happens on beach/lake. Dont think there would be much correlation between the two !
a) Think of a fin that is more or less straight on its trailing edge but curved on its trailing edge. Lay it flat on a table. This is an example of when you will see more width (span of the fin) on the leading edge while observing a more narrow trailing edge. The planing surface of a board works very similarly. By changing the curve and location of maximum depth of a fin, you can move the trailing edge forward (shortening the chord length of the fin) without dramatically altering its performance. Likewise you can change its performance.
b) Wingers, generally, create more a more parallel outline in the middle of the board that may offer more power and/or speed at certain angles but keep a more narrow tail that may add control or raise the nose of the board. It's very unlikely that Star-board made no other changes to these boards besides the wingers. Subtle tweaks to many deign parameters are likely involved to offer improved performance. One of those changes appears to be the use of wingers.
Cutaways reduce Drag ????
Think you`ve mixed trailing/leading up in your reply but I understand all you are saying and agree with most points but in the blurb starboard claim/make the premis that adding cutaways decreases drag at tail of board.
This is contrary to current fluid dynamics theory.Cutaways or any other manipulation of trailing edge by sheer maths must increase that edges "edge length" (#see point later) This may well be advatageous for other reasons.(ie widening board to increase leverage available for fin but keeping tail area down for top end control) But none of that is mentioned.
#There is a current (yet unproved) theory that applying "saw tooth" shape to trailing edge of a wing helps lift /drag ratio but this is to do with generating tip vortices accroos span of wing and not as a direct way to reduce drag.)But tip vortices and their effects have nothing to do with planing surfaces.Boards plane through momentum exchange between water and board.(ie a board is not a wing/hydrofoil)
With a staight leading it is mathematically impossible for trailing edge to be shorter.A boards leading edge is inevitably straight.(Boards` planing surface is virtually flat in almost every instance) The minimum trailing edge would be another staright line parallel to leading. This would give minimum drag but probably be unsailable ????
I was thinking about the same a few weeks ago, posted on this forum & my website too.
I would like to add 2 things:
-From my interpretation (starboard quote) the Leading Edge is not an edge but the point/line on the bottom were the board hits the water. Trailing edge is an edge, the rails behind the leading edge. Correct me if I am wrong.
-I think lenght of the rails doesn't really matter, I think starboard does explains the outline and width vs drag. De double wingers are placed on 2 crucial points. The winger in front is the place were water does release when I am normal sailing, crosswind. In extreme chop/waves /windlulls/start planning I use the part in front of the wingers. The backwinger is placed really close to the maximum release point, in very light wind I use this release point. And for speedsurfing I also try to release the board somewere in the back.
With wingers the range of a board could be bigger (Sadly I haven't tried/tested it). Because the effect of changing your release point becomes bigger/ or more sudenly?. I guess the difference would be for advanced surfers: "Like changing gears manual in a car, and not a automatic gearbox."
Still I question one thing, is the waterpressure bigger per cm2 at the front footstraps, or at the back footstraps. From statical enginering I would say the back, but if I understand starboard's quote it should be the front????? Am I wrong, or is my english not good enough ;) ?
|All times are GMT +7. The time now is 05:15 AM.|
Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.