after riding my old pos scott scott the other day i realized that the bottom finish is very rough as opposed to a glossed board. Also wen i switched back to the same exact board that i just had made a month ago…i realized that it hasnt bogged down in the same critical sections as my old board. My new board has a gloss coat. So the real question is, how does the finish of a board influence speed and planing?
–tom
“rough is slow”
Gloss is pretty fast.
Discriminating performers sand their tail bottoms in the direction of water flow with 600 wet/dry, and say it’s the fastest.
Who needs speed? We turn to stall and slow down, not outrun the waves.
Careful on those comparisons, the old board may have lost it’s lively flex properties compared to the new…
yea…good point…i was just wondering
…that being said, don’t discount it either, there’s lots of stuff in the archives…Quite a variety of opinions of what’s faster, and ways to do them…Personally, I rely on a carefully concocted mix of truck-bed paint, wax from other boards, greasy sea-scum, runoff pollution, cat hair, and other proprietary materials…
Who needs speed? We turn to stall and slow down, not outrun the waves.
Sometimes you do, sometimes you don’t.
regards,
Håvard
this is something i heard , and sometimes i think its true…i ride both sanded rough and polished,and ive heard that a polished board wants to form a bond with the water, and sortof stick, (slow down)…could be true…i forget the techinical word for this effect, but to me it made sence at the time…i shine a board so itll look good…not for speed…think about it, how many sanded longboards do you see, ? and how many polished shortboards?..why…because i think sanded boards are faster…but thats just me,think and do whatever the hell you want…
Sanded finish boards are cheaper and easier to make. Justified with performance gain! Negligble performance gain, if any at all.
IMHO
HerbB
Don’t believe the hype! NWA
interesting comments…my personal boards are finnished to sandcote,1000 grit finnish.
maybe its faster,maybe not,but 1 thing is sure…it weighs less.
untill it soaks then i make another board.
customers,needdless to say,get what they want and get charged for it.
At http://www.vacantisw.com/foildesign.htm it is suggested about a smooth bottom finish that:
“Generally speaking, a very smooth keel surface is perhaps most valuable at low speeds-perhaps 2 to 3 knots-when the Reynolds number is most likely to be below the critical value of 1.5 million”.
However a significant decrease in friction at low speeds in a surfing situation can sometimes allow the rider to make it through a slow section into a faster section, the practical result in such a case being that although the smooth bottom gives less friction reduction at higher speeds, it enables the rider to get into a high speed section which he might otherwise have missed.
I find that sanding my boards with 600 to 1200 grit in a fore and aft direction makes a very noticeable difference to the speed of the board, but also that I hardly ever bother to do it!
I used to race on a 55’ Nelson Merrick that never applied an anti-fouling bottom paint. Before each major race they would have my yard haul the boat, acid wash the bottom wetsand to 600 grit and apply a alcohol base teflon to the bottom. It also had a very fine waterline with minimal wetted surface area. In light air we were able to sail under and through the lee of Taxi Dancer with Dave Ullman steering for the 70’ Hi Point Series. So, yes, from personal experience, surface prep does have a major influence in low speed hydrodynamics.
u say teflon…dang,i had boards with sprayed on ureathane finnish.
that died out when glassers found out how deadly 'thane was.oh,those boards were faster under all conditions. they realy neede looking after else the finnish rubbed off and dings were a total night mare repair
the russians did some hydro research on dolphins,some of the findings actualy used on subs in the cold war era: supple skins with the ability to GRIP water so drag is reduced to increased laminar flow
it also made the sub quieter.
something to ponder eh?
Hi Tomatdaum, I used to love those drifters too, when I was sailing centreboarders and half tonners in the 70’s. I remember reading about Rainbow II and her successful challenge for the one ton cup (1970?) Two of the crew travelled with the boat on boat on the ship which was carrying her to Heligoland for the series, and they spent the trip applying layer after layer of wax polish to the hull, until it shone like a mirror. They received a telex just before they arrived instructing them to strip off all the wax and sand with 400 grit as the latest tank tests showed wax polish to be slow. They did the deed and Rainbow won in light conditions. Those old IOR shapes still do it in drifting light conditions too. It’s rather a pity that the Americas cup races don’t allow racing in winds of 0 to 5 knots, it is so dramatic and interesting.
Actually, I suffer through the light stuff and the around the buoy stuff for the big pay off. Long distance offshore surfing downwind is what I do it all for:)