Author Topic: glossy surface has substantially more drag than a matte one.  (Read 33190 times)

PonoBill

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Re: glossy surface has substantially more drag than a matte one.
« Reply #30 on: April 25, 2010, 09:59:21 AM »

Yes, lets all listen to Ponos rhetoric based on studying a web site instead of testimonials by persons with practical experience.   

Pono....give this stuff a chance.  You might wanna consider rubbing some [of this] magic fluid between your ears. ;)

So how did you decide that? I've been using Sailcoat and Hullcoat (and other brands of polishes and lubes) on my boat (a rasty old Aquarius 23) for as long as it's been available, which has to be more like 20 years. I confess I never thought of spraying dry lube on the hull, and I've never heard of people doing it, but I don't race boats.

I do race cars, and there's a new magic fluid every week. I am naturally skeptical

So if I rub some between my ears will it grow hair?
Foote 10'4X34", SIC 17.5 V1 hollow and an EPS one in Hood River. Foote 9'0" x 31", L41 8'8", 18' Speedboard, etc. etc.

watermelonman

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Re: glossy surface has substantially more drag than a matte one.
« Reply #31 on: April 25, 2010, 10:40:53 AM »
All of this banter back and forth was confusing me, so I found a paper by an MIT Hydrodynamics professor, who also races sailboats.  He discusses laminar flow, Reynolds numbers, boundary layer separation, viscosity, wet sanding, waxing, lubricants, the whole nine yards, and dispells many of the misconceptions.

BUT,  in the end, what he does on his boat is to use a progressive wet sanding, going from 200 to 600 grit paper, in one direction then 90 degrees to it, finishing with an orbital -  then he applies some sort of lubricant or wax!!! Now I'm really confused.  What he says is that the uniformity of the surface is what's important, not whether it's sanded, waxed, or lubed.  And he goes on to say,  that what REALLY, REALLY, matters is the sailing ability of the skipper.

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Re: glossy surface has substantially more drag than a matte one.
« Reply #32 on: April 25, 2010, 10:50:00 AM »
All of this banter back and forth was confusing me, so I found a paper by an MIT Hydrodynamics professor, who also races sailboats.  He discusses laminar flow, Reynolds numbers, boundary layer separation, viscosity, wet sanding, waxing, lubricants, the whole nine yards, and dispells many of the misconceptions.

BUT,  in the end, what he does on his boat is to use a progressive wet sanding, going from 200 to 600 grit paper, in one direction then 90 degrees to it, finishing with an orbital -  then he applies some sort of lubricant or wax!!! Now I'm really confused.  What he says is that the uniformity of the surface is what's important, not whether it's sanded, waxed, or lubed.  And he goes on to say,  that what REALLY, REALLY, matters is the sailing ability of the skipper.

If I were a sailboat racer and had the cred of an MIT prof, I would conclude by telling my competition that the key to going fast was stowing extra weight in the bow...and dragging a bucket  ;D


greatdane

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Re: glossy surface has substantially more drag than a matte one.
« Reply #33 on: April 25, 2010, 03:38:24 PM »
Try waxing the bottom of your board with a bar of soap..!
No BS
Beau try it on with your fastest board with your GPS thingie..
only works for a short time .but you'll feel the difference..

That's funny you mention that Lee... we used to use soap when snowboard racing in warm, spring snow... super fast, but had to be re-applied every run.  We all know that soap breaks up the surface tension of water...  hmmm.

We use a special foam occasionally mixed with water for fire fighting... it breaks up the surface tension of the water so that the water can get into deep-seated fires... like tire piles and hay piles.  Hmmmm again.
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blueplanetsurf

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Re: glossy surface has substantially more drag than a matte one.
« Reply #34 on: November 17, 2010, 01:00:09 AM »
If you are into the science of water flowing over the hull, this is a great read:
http://www.eatonsurf.com/hullscience.pdf
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wasserdog

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Re: glossy surface has substantially more drag than a matte one.
« Reply #35 on: November 17, 2010, 08:46:04 AM »
Greg Liddle on the subject:

     "I suggest that the finish coated bottom be wet sanded with #320 or #400 wet/dry sandpaper. Use water and sand in same direction as the stringer from nose to tail, tail to nose, do the fins and rails too. You will notice that the water will stick to the wetsanded bottom and feel very different from the finish coated and polished bottom. To me, the result feels faster, more under control and more connected to the wave. You can try it on any board. Ride it glossed first, wet sand the bottom and try it again to feel the difference. The board can be freshened periodically in this way if it becomes dead and sluggish."

                                                             he dah man !!

SoCalSupper

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Re: glossy surface has substantially more drag than a matte one.
« Reply #36 on: November 17, 2010, 10:22:12 AM »
wow this is really interesting-never heard of this before-i rarely paddle race-mainly surf-bottom line if for me someone-will sanding the bottom of my Nectar make my board faster?-really?!-noticeably?!-im intrigued-love going fast on my SUP so if this works i may give it a try!
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WB

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Re: glossy surface has substantially more drag than a matte one.
« Reply #37 on: November 17, 2010, 01:07:14 PM »
I will forcibly restrain SoCal from sanding his custom 14'. My intervention will prevent the Hobie crew from putting a bounty out on his head.

However, I have no problem of watching him sand his and his son's boards before I take paper to mine.

-W

pdxmike

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Re: glossy surface has substantially more drag than a matte one.
« Reply #38 on: November 17, 2010, 01:16:15 PM »
Try waxing the bottom of your board with a bar of soap..!
No BS
Beau try it on with your fastest board with your GPS thingie..
only works for a short time .but you'll feel the difference..

That's funny you mention that Lee... we used to use soap when snowboard racing in warm, spring snow... super fast, but had to be re-applied every run.  We all know that soap breaks up the surface tension of water...  hmmm.

We use a special foam occasionally mixed with water for fire fighting... it breaks up the surface tension of the water so that the water can get into deep-seated fires... like tire piles and hay piles.  Hmmmm again.
I've been experimenting with soaping my paddle blade, and when I do I definitely feel that I get a cleaner entry. 

pdxmike

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Re: glossy surface has substantially more drag than a matte one.
« Reply #39 on: November 17, 2010, 02:30:55 PM »
sharkskin is even faster
In swimming, Speedo's long tech suits started a few years ago with a textured ribbed fabric that created a thin layer of bubbles against the suit (the Aquablade model).  That was replaced with the FastSkin, which had a heavier texture patterned after sharkskin.  The idea was that the texture made the swimmer slip through the water faster.  Then that was replaced with the LZR, which went the opposite direction and incorporated smooth polyurethane panels.  Other techsuit manufacturers used polyurethane coatings over their whole suits.  Each generation of suit was faster than the previous one, although they also got progressively tighter, so texture wasn't the only variable.

So, swimming was dealing with the same question of smooth versus textured.  The tech suits are illegal now, so no conclusion was ever reached.  And I'm not going to try sanding my skin to test that, either. 

greatdane

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Re: glossy surface has substantially more drag than a matte one.
« Reply #40 on: November 17, 2010, 03:03:57 PM »
I wet-sanded the bottom of my 18' Bark the day before Round the Rock.  Took the high-gloss finish off with 200 grit paper/water.  Over a 13 mile course, I got second place ahead of third place by a mere 3 seconds.  Was it the sanding?  Probably not.  But, even if it only makes a board .01% faster, that can add-up in a close race.  My brain probably told me it made me faster... power of suggestion.
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pdxmike

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Re: glossy surface has substantially more drag than a matte one.
« Reply #41 on: November 17, 2010, 03:26:19 PM »
I wet-sanded the bottom of my 18' Bark the day before Round the Rock.  Took the high-gloss finish off with 200 grit paper/water.  Over a 13 mile course, I got second place ahead of third place by a mere 3 seconds.  Was it the sanding?  Probably not.  But, even if it only makes a board .01% faster, that can add-up in a close race.  My brain probably told me it made me faster... power of suggestion.
Greatdane--the proof that sanding works is that every racer in any sport will tell you that winning comes down to whoever has the most grit.

Pierre

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Re: glossy surface has substantially more drag than a matte one.
« Reply #42 on: November 17, 2010, 03:36:31 PM »
Last summer I sanded hull of my epoxy-plywood 14 foot race board ( grit 600 wet carborundum paper) , and before my first race I also cleaned it up with soapy water. whatever the reason I won the 7 mile race 3.5 minutes ahead of a 17-footer carbon board .
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SoCalSupper

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Re: glossy surface has substantially more drag than a matte one.
« Reply #43 on: November 17, 2010, 03:49:39 PM »
Dont worry WB-i would give you permission to shoot me if i ever took a sander to the Hobie!-but im still not convinced as to the whole sanding thing-You go first!! :D
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pdxmike

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Re: glossy surface has substantially more drag than a matte one.
« Reply #44 on: November 17, 2010, 03:50:35 PM »
I wet-sanded the bottom of my 18' Bark the day before Round the Rock.  Took the high-gloss finish off with 200 grit paper/water.  Over a 13 mile course, I got second place ahead of third place by a mere 3 seconds.  Was it the sanding?  Probably not.  But, even if it only makes a board .01% faster, that can add-up in a close race.  My brain probably told me it made me faster... power of suggestion.
Greatdane--the proof that sanding works is that every racer in any sport will tell you that winning comes down to whoever has the most grit.
Seriously, greatdane, .01% off your time would have been nearly 9 seconds.  So, even if sanding cut your time by less than half of .01% that would have been the difference.  Plus, sanding made your board lighter!

The big deal to me in any kind of competition is that part of doing everything you can do to help your speed is so you can win, but an equal part is to eliminate remorse and excuses.  If I hadn't sanded and lost by 3 seconds, I'd feel bad for having skipped an easy step that could have changed the outcome.  Or, worse, by skipping something that I knew might help me, I'd open up the potential to make it an excuse.  Without sanding, I might think that I would have won if I'd sanded.  I could convince myself that the other guy certainly did sand, and I might even be able to convince myself that the sanding would have shaved 30 seconds off my time instead of 3.   

In my own case, I didn't sand for Round the Rock, and it cost me a couple hours at least. 

 


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