Standup Zone Forum

General Category => Gear Talk => Topic started by: SEA on April 22, 2010, 08:25:28 PM

Title: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 22, 2010, 08:25:28 PM
This article is from the board lady and I am now seeing why Naish uses an unfinished bottom , or matte finish on the bottom.  What do you guys think ??? I'm wet sanding my bottom ... the board that is :)
 
Check out the pictures at the bottom



By Eva M. Hollman

Water is pretty sticky: dip a paddle into the ocean and it comes up with much water attached. Move a board through the ocean – be it surf, windsurf, stand-up, or kitesurf -, and it will drag a substantial amount of water along, which, as it eventually cannot hold on to the bottom any more, emerges behind in the form of a wake. The energy that you generated with your sail, kite or paddle, went into accelerating not just you and your board, but this rather substantial mass of water as well.

To go faster, then, we need to decrease the amount of water “sticking” to your board – “reducing the drag” in techno-lingo, since the best wake is no wake!

In extensive tank testing for world-class racing boats, it was established 40-some years ago that a glossy surface has substantially more drag than a matte one. In tests I was involved in for an America’s Cup boat, we found that simply sanding a glossy bottom with 600 grit paper, reduced the surface friction by about 5% at ½ hull speed, i.e. at about 4.5 knots. Instead of sticking to the glossy bottom, the water molecules would be “tripped up” by the minute ridges left by the sandpaper. This slight turbulence would reduce the thickness of the film of water being moved along with the vessel (the “boundary layer”), and thereby reduce the overall drag.

Surfboards are traditionally finished super-glossy-shiny. Windsurfers, on the other hand, have long since followed the lead of sailboat racers and taken the gloss off the bottoms of their craft.

If you wonder if your bottom is too shiny, throw a cup of water at it: if the water beads, like it will on a freshly waxed car, then the surface tension is high, and therefore its resistance going through the water is high.

To change it to a low-drag surface, sand it in a circular motion with 600 grit wet & dry paper, until water thrown at it runs off in sheets – WITHOUT ANY BEADS forming.

Instead of wet & dry sandpaper, you can also use a “Purple Pad”, a Scotch brand synthetic wool pad designed to burnish metal and take off rust. Again, a circular motion is optimal.

To keep this fast surface fast, wash it now and then with soapy water; and lightly apply the Purple-Pad when the bottom appears yellow.
   


How big a difference will this make? After a bottom repair a while back, I decided to Purple-Pad the entire bottom of a windsurfing board. The owner noticed with a raised eyebrow, but did not comment on it when he picked up the board. However, he was back 4 hrs later, demanding to know what exactly I had done to his board: a friend, who had always easily passed him before, was no longer able to even keep up with him.

Or this recently from Shawn C: “I purchased an old Hifly 265 poly board that I used a couple of times and really enjoyed.  I noticed that the board had a few small gouges on the bottom so I thought that I would sand them down using wet/dry 600 grit as you suggested.  I then mistakenly waxed the bottom and had horrible performance on the water.”

Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 22, 2010, 08:30:07 PM
Sorry guys the pictures are opposite in the thread they should be the beading water is Slow the Sheeting water is Fast

Title: Re: glossy surface has substantially more drag than a matte one.
Post by: Pureadrenalin on April 22, 2010, 09:01:25 PM
I like the sanded finish maybe cause I'm dull ;D. Checkout Doug's quiver majority sanded.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 22, 2010, 09:17:51 PM
I guess Doug is on it ??? 
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: corgi on April 22, 2010, 09:30:40 PM
Interesting tip, thanks SEA, I'm all for making my board faster.  I just have a hard time sanding my board being its only 2 months old.  If I do, is handing sanding good enough or would using an orbital sander be more efficient?  ???
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: bigdom on April 23, 2010, 02:18:51 AM
sharkskin is even faster
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 23, 2010, 05:30:56 AM
Interesting tip, thanks SEA, I'm all for making my board faster.  I just have a hard time sanding my board being its only 2 months old.  If I do, is handing sanding good enough or would using an orbital sander be more efficient?  ???


I would definitely NOT use an orbital sander !!! You'd want to just sand by hand a little at a time till you achieve the finish you are looking for.
 
In Eva's article it says...... "To change it to a low-drag surface, sand it in a circular motion with 600 grit wet & dry paper, until water thrown at it runs off in sheets – WITHOUT ANY BEADS forming.

Instead of wet & dry sandpaper, you can also use a “Purple Pad”, a Scotch brand synthetic wool pad designed to burnish metal and take off rust. Again, a circular motion is optimal."


When I got back my Naish 14 glide from being repaired this week, Clay Carson remarked how the bottom of the board had a matte finish on it and that he had to wet sand it to make the repair like the rest of the bottom. However he  said he had to follow the sanding lines of the rest of the board. He said it appears that Naish finish sands the bottom of the 14 and 17 glides  with a straight up and down stroke ( from tail to nose). So I don't know which is better a straight up and down sanding stroke or a circular one like Eva recommends. I guess we will have to experiment ???
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: stillwater on April 23, 2010, 06:23:38 AM
I have wondered why my Starboards were matte finished. I don't think I will be waxing them in hopes of making them faster. Thanks for the insight.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: DavidJohn on April 23, 2010, 06:40:08 AM
The bottom of my new Naish 17 and also the new 14' Javelin are sanded.. but not just sanded.. they're directionally sanded.. We used to do it on our slalom and speed windsurfing boards.

DJ
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: 1tuberider on April 23, 2010, 06:55:05 AM
Some race boats have blueprinted hulls.  I know on my whitewater racer bottom maintenance was important for top speed. Hulls are flipped over and low spots filled in and no hook in the tail. 

If you have dents or other imperfections I would address them before the sanding process.

I also believe there are applications that can be painted on that will give similar results.  Drift boats can get a coating of glovit to not only seal the bottom but to also make it easier to paddle by decreasing resistance. 

What are the top racers using?  Some may be going beyond sanding and may be keeping it a secret.

Title: Re: glossy surface has substantially more drag than a matte one.
Post by: chipmonk on April 23, 2010, 10:37:28 AM
Hey, in your pictures it looks like that Rusty is a molded board. Is that true ? Will this work to wetsand the paint on a molded ?

Title: Re: glossy surface has substantially more drag than a matte one.
Post by: JustPaddle on April 23, 2010, 03:46:32 PM
A downside of the matte finish on the Naish boards is that my friends 14ft Glide has black marks from the Dakine tiedown straps.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: DavidJohn on April 23, 2010, 04:41:25 PM
A downside of the matte finish on the Naish boards is that my friends 14ft Glide has black marks from the Dakine tiedown straps.

Mine did the same so I swapped to the blue Kialoa straps and now I don't get any marks at all.

btw.. These are the best things for removing marks from boards.. http://www.chux.com.au/images/library/Image/hero/hard_surface_2pk.jpg (http://www.chux.com.au/images/library/Image/hero/hard_surface_2pk.jpg)

DJ

Title: Re: glossy surface has substantially more drag than a matte one.
Post by: Lobes on April 23, 2010, 06:57:02 PM
This is all fascinating and to be honest I would have assumed the opposite, that glossy was faster.

I too would like to know  more about the performance difference regarding applying matte with a circular sanding motion or a straight up and down.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: heave on April 23, 2010, 09:24:54 PM
I usually just do 400 grit wetsanded with linear flow.  Its mostly a .005 mm granular roughness that matters.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: wadadli_waterman on April 24, 2010, 07:49:44 AM
One word (or name)......McLube.

Their Sailkote dry lubricant spray has been used by the fastest sailors in the world for years.

Its the high tech equivalent to greased owl poop......no sanding, burning through or staining.

The stuff works.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 24, 2010, 09:56:35 AM
One word (or name)......McLube.

Their Sailkote dry lubricant spray has been used by the fastest sailors in the world for years.

Its the high tech equivalent to greased owl poop......no sanding, burning through or staining.

The stuff works.

Is that the Mclube hullkoat ??  Have you used it on Matte finish ?? I've never heard of this stuff. Has anyone else used this ? it looks like the sailors LOVE it for their hulls.

http://www.mclubemarine.com/hullkote/ (http://www.mclubemarine.com/hullkote/)
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: enden on April 24, 2010, 10:07:08 AM
I'm not sanding my board. Speed is not on the top of my priority list.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 24, 2010, 10:17:59 AM
I'm not sanding my board. Speed is not on the top of my priority list.

When doing down wind runs , speed IS what we are concerned about. Definitely would not do to a nice glossy surfboard or SUP surf board.

Maybe spray that Mclube sailkoat on it looks like it works
http://www.mclubemarine.com/sailkote/ (http://www.mclubemarine.com/sailkote/)
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: PonoBill on April 24, 2010, 11:48:39 AM
Sailcoat is for refurbishing old sails and making them handle better. Hullcoat is boat polish. There's a big difference between what works for boats and boards. Unless you leave your board floating in the water all season Hullcoat won't do much for you. It's to keep the algae and gook in the water from sticking to the hull and slowing the boat.

Lightly sanding by hand shouldn't harm your board at all, and it's probably good for a minor increase in performance. Sand a little area, wet all around it and just slide your fingertips across the surface. The sanded section holds the water better and your fingers slide smoothly across, when you hit the glossy area your fingers stop dead.

Most of my boards have a lightly sanded bottom--surfboards too. Makes me feel better, and that's probably about it. All the dings, scratches and pressure dents certainly overcome anything I've done. But there's no reason for a surfboard to have a glossy bottom.

There's always someone selling magic fluid.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: wadadli_waterman on April 24, 2010, 01:37:29 PM
Sailcoat is for refurbishing old sails and making them handle better. Hullcoat is boat polish. There's a big difference between what works for boats and boards. Unless you leave your board floating in the water all season Hullcoat won't do much for you. It's to keep the algae and gook in the water from sticking to the hull and slowing the boat.

Lightly sanding by hand shouldn't harm your board at all, and it's probably good for a minor increase in performance. Sand a little area, wet all around it and just slide your fingertips across the surface. The sanded section holds the water better and your fingers slide smoothly across, when you hit the glossy area your fingers stop dead.

Most of my boards have a lightly sanded bottom--surfboards too. Makes me feel better, and that's probably about it. All the dings, scratches and pressure dents certainly overcome anything I've done. But there's no reason for a surfboard to have a glossy bottom.

There's always someone selling magic fluid.

Yes, lets all listen to Ponos rhetoric based on studying a web site instead of testimonials by persons with practical experience.   This kind of crap always gets my goat but I guess its part of the forum world where the number of posts a person has gives them some kind of clout.

Sailkote is in fact applied on hull surfaces.  Its applied mostly on small dinghys and other racing one designs which in many cases have also been rubbed down with 400 grit...becuase the stuff works.  It really does make a hull quicker through the water and its been around for more than 10 years.  In fact some class associations ban it as its considered a cheat.  I am talking about trailerable boats that don't live in the water with hull sizes, speeds and shapes not unlike SUP downwiners. 

I have applied it to my downwind boards, its a piece of piss to do, and I do notice an appreciable difference.

Pono....give this stuff a chance.  You might wanna consider rubbing some [of this] magic fluid between your ears. ;)
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: wavehobbit on April 24, 2010, 02:28:20 PM
Absolutely true.  We learned this years ago w/ windsurfing.  Take a glossy fin and your spinning out, 600 sand it and it's like night and day.  I sand all of my fins with 600 and the bottoms of the boards.  It makes a huge difference.  If you wet sand it doesn't take long at all, you'll see the water attaching to the board and you move on.  Great tip, that somehow wasn't brought up before on this site.  Also alot easier to grab your board in the foam going out then a slick glossy. 
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: jdmotes on April 24, 2010, 06:57:29 PM
 I get asked again and again why our Nah's have sanded bottoms while the decks are glossed. These boards are made by AHD (Advanced Hull Dynamics) well known in the windsurfing community for great sailboards. They know what works!      JD
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: JustPaddle on April 24, 2010, 07:19:38 PM
I wonder why Mark R. boards have a glossy bottom?  8)


here's a link with some additional info - http://www.epickayaks.com/news/news/to-wax-or-not-to-wax (http://www.epickayaks.com/news/news/to-wax-or-not-to-wax)
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SUPaholic on April 24, 2010, 08:42:59 PM
Is it okay to sand down a SUB w/ carbon fiber?
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: greatdane on April 24, 2010, 09:12:35 PM
Is it okay to sand down a SUB w/ carbon fiber?
I'm not an expert on CF, but I wet sanded the gloss finish on the bottom of my carbon Bark.  My uneducated guess is that you are ok as long as you don't sand deep enough to get into the fibers of the carbon...  but wet sanding should just dull the clear coat.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: lee on April 24, 2010, 09:53:33 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..
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SEA on April 24, 2010, 11:44:34 PM
I wonder why Mark R. boards have a glossy bottom?  8)


here's a link with some additional info - http://www.epickayaks.com/news/news/to-wax-or-not-to-wax (http://www.epickayaks.com/news/news/to-wax-or-not-to-wax)

After reading the link above at epic kayaks .com , I'm confused or at the very least back where I started. wondering what works best. Guess it does not matter cause I'm no Olympic caliber paddler.  Just find this topic extremely interesting. I will keep looking for more info on both sides of the fence. hope you guys do to.

Thanks
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: warped on April 25, 2010, 02:50:41 AM
I wonder why Mark R. boards have a glossy bottom?  8)

Nearly every hand shaped S.I.C. board I've seen had a sanded bottom, including my F18.  A while back Mark mentioned that only the molded boards he produces have glossy bottoms.  Not sure if that's still true today since it seems like he comes up with new innovations every week.

This is copied from the S.I.C. website (on the F18 page):  "We recommend a light grey primer bottom. It is light, fast and has little friction due to the ultra fine sanded surface."
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: heave on April 25, 2010, 08:08:36 AM
I always wetsanded with 400 grit and then would secretly coat my laser sailboat with Ivory dish soap the night before each day of racing.  I would always try to be one of the last boats in the water as to not have it rinse off too soon.  Maybe it worked or it was just psychological.  All I know is that I would usually finish very well in the first races.  Rounding the first bouy in first place in the first race has its advantages.  That was 30 years ago and I don't need to leave a slimey bubble trail anymore.
       

   
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: PonoBill 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?
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: watermelonman 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.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: Admin 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

Title: Re: glossy surface has substantially more drag than a matte one.
Post by: greatdane 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.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: blueplanetsurf 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 (http://www.eatonsurf.com/hullscience.pdf)
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: wasserdog 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 !!
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SoCalSupper 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!
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: WB 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
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: pdxmike 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. 
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: pdxmike 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. 
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: greatdane 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.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: pdxmike 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.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: Pierre 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 .
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: SoCalSupper 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
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: pdxmike 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. 
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: Paddlefit on January 10, 2011, 11:28:50 AM
Does anyone have any more insight into this subject?  I had to do a repair to my board, and with the Cold Stroke Classic coming up this Saturday I was debating going to Home Depot and spending this friday sanding the bottom and rails of my board, as well as the blade of my paddle. 
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: Fishman on May 11, 2012, 06:33:42 PM
Lets  TEST this!!!

Boy, interesting info but most of this is very subjective and vague and may have zero relevance with our size boards and speeds. 

How about simple testing this. We should see if this really make a difference with SUPs.

All we need is a good scale, fishing line, a moving swim pool, a board and weight/sand bags. 

 I'm sure someone here has access to a "moving swim pool" (not sure what they are called, the kind where people swim in place)
Place the board in the pool, secure the board nose to the secured scale.
Turn the pool on to it to a average paddle speed.
Measure the drag. Then add weight 150 & 200lbs and ad measure. then experiment with sanding, waxing, soap... Then record the facts.

Anybody In Atlanta Ga have a Moving pool...?
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: ObviousSup on May 12, 2012, 03:14:25 AM
This stuff sounded pretty impressive
http://www.hydromer.com/seaslide_web/brochure_sealide.pdf (http://www.hydromer.com/seaslide_web/brochure_sealide.pdf)

Then I noticed where in the drag test they noticed no improvement at 3 knots. If I could paddle at 20 knots the 17% reduction would sure be nice but I am not quite that fast.

I think I will just stick with my carnauba wax that I use on my other fiberglassed toy. After seeing the difference between how well water blows off a well waxed car vs a car that hasn't been waxed in ages I will go with wax. I don't need to trap water on the surface to act as a lubricant between the board and another solid surface (if I do I suspect I am doing something wrong). All I am concerned about is keeping my board looking nice and making water not stick to it. I suspect higher speeds that some boats attain might change things but with must me and a paddle I will not be seeing those speeds.
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: colas on May 12, 2012, 05:11:45 AM
After reading this post, I 400-sanded both a windsurfing and a SUP board, and I say you can definitely feel a small difference in the transition from non-planing to planing, basically, your take offs are smoother, or on a wave when you go up the wave face, find  the trim line and put your weight forward, you feel the board "changing speed" more easily.

Other than this, I didnt feel any difference.

I sanded my paddle blade faces, but could not feel a difference there.

So I would say that for boards you enjoy the glide (longboards), it may be worth it if you are a nitpicker, but not if it destroy the looks of the board (visible wood, spray paint job on the blank, ...). On opaque white boards I would recommend it, for instance.

For racing. I guess only a controlled experiment would tell
Title: Re: glossy surface has substantially more drag than a matte one.
Post by: PonoBill on May 12, 2012, 09:14:26 AM
If you did manage to improve flow on a paddle face it would be a bad thing. Slip is just water flowing off the face and into the low pressure area behind the blade.

The hull sanding thing is pretty easy to test with a boat and an accurate scale and speedometer. You boom a weighted board off to the side to get it out of the turbulence and record force at a specific speed. I'd want to do the tests close together with several interspersed repeats to cancel out some of the environmental variables, but easy to so if someone really wanted to know. You could also do it in a lap pool with a winch (which is basically how a test pool works). A jet pool wouldn't work well, too much turbulence.