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Advice, Suggestions and General Help New Topic Printer Friendly Version

  fastest bottom prep?
  Posted by: davavd on Feb-27-13 6:57 AM (EST)
   Category: Canoes 

What bottom treatment makes for the most speed? I have polished the bottom of my old fiberglass canoe, using the same equipment and polishes that I use for my car. It's all shiny now. Is there anything else I should do to prepare for a race?

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Messages in this Topic

 

  Sure
  Posted by: BNystrom on Feb-27-13 7:02 AM (EST)
Now that you've wasted a lot of time polishing it, sand it with 400 grit. The slightly textured surface is actually faster than a polished surface.
 
 
  X's 2
  Posted by: jackl on Feb-27-13 8:19 AM (EST)
And the other thing is to train, train, and train some more.

jack L
 
 
  Thanks!
  Posted by: davavd on Feb-27-13 9:37 AM (EST)
I was afraid the answer would be wet-sand. That's what we used to do to sailboat bottoms back in the day, but I thought just maybe someone had discovered something new. No biggie, the boat is short and I've still got two days before the race. Training I've been doing since I started thinking about the race (Battle-on-the-Bayou, Ocean Springs, MS). I'm in pretty fair condition for a 60 year old; I won't win, but I should finish respectably and have a good time doing it.
 
 
  B-o-B IV
  Posted by: Pirateoverforty on Feb-27-13 10:42 AM (EST)
Lot's of people just out for the paddle. That first leg you'll be fighting some headwind until you get up into the bayou. Stay out of the pack making that first turn, I have been in a press so tight I couldn't get my paddle in the water. No where to get out and stretch except for the lone bathroom break. I wanted to fix up an old glass canoe and make a run for placing in the solo canoe class but have been spending too much time on the road and haven't finished it.

A nice moonlight paddle - About an hour before sunset on the night before the full moon put in at the launch where they have the break set up and paddle up to the power lines and wait for the moon to come up.
 
 
  The winners will be..................
  Posted by: thebob.com on Feb-27-13 11:16 AM (EST)
The winners will be the paddlers who spent the most time training, and have the most experience racing; NOT the paddlers with the canoe that has the most highly polished hull.

BOB


 
 
  What about Rain-X?
  Posted by: magooch on Feb-27-13 11:35 AM (EST)
Some have insisted that Rain-X makes a difference. I'm thinking about trying it, but I wonder how one would ever tell the difference. One thing I've noticed is that when I first launch and take off--no matter which boat I'm in it feels fast. After a few hours of paddling, they all seem to slow down.
 
 
  Should have the opposite effect. One
  Posted by: ezwater on Feb-27-13 12:52 PM (EST)
wants a tiny, thin layer of water to be able to adhere to the surface.
 
 
  dimples like a golfball will do that
  Posted by: Pirateoverforty on Feb-27-13 1:03 PM (EST)
Mythbusters did it to a car and improved the gas mileage.
The trick is knowing what size depression to make.
 
 
  Myth
  Posted by: willi_h2o on Feb-27-13 11:19 AM (EST)
-- Last Updated: Feb-27-13 11:36 AM EST --

Many have called this a complete myth
-- choosing instead for clean and smooth.

http://www.examiner.com/images/blog/EXID23194/images/Waterflow_around_kayak_hull.jpg

If someone has definitive proof one is better than the other
we would all like to read the study and analysis.
I'm guessing it's all on the magnitude of 1% plus/minus
since it's low speed human powered watercraft.

Diligently avoid getting nicks, dings, and scratches
in the hull whenever possible to help the kayak/canoe glide
smoothly through the water as you paddle.

Myth ""probably"" originated from :
A micro-grooved adhesive backed plastic film from 3M
was tried out by Greg Barton in the semifinals of the
1986 World Championships in Montreal. Apparently the
grooves need to be very carefully aligned so they are
parallel with the flow of water over the surface.
The size of the grooves was matched to the density
of water and the speed of travel so that the grooves
dampen the turbulence of the water as the flow
detaches from the hull.

This leads up to a popular internet myth :
The crazy idea of hand sanding a "texture" into a hull.
You'll never get the robotic accuracy needed for
perfectly straight and parallel lines down the
entire length of your hull.

Frictional drag comes from the "water on water" inter-action
in the boundary layer, the water that is close to the kayak hull.
The trick is attempting to get smooth laminar
flow with a low "shear stress" of the water molecules
sliding against one another.



 
 
  The "myth" originated earlier than that.
  Posted by: ezwater on Feb-27-13 12:57 PM (EST)
After our rowing coach talked to our MIT naval architects, he had us wet sanding the shells with fine sandpaper.

Don't need parallel grooves, just need to eliminate shine that beads water.

But it's a very small effect, and I don't think even rowing shells reach speeds where it makes much difference.

So, I wouldn't be so dismissive on the issue. Let's just say that if something DID make a big difference, it would be more well-accepted by now.

My belief is that eliminating roughness caused by wear will make a modest difference, and that mirror finish and Rain-X go slightly in the wrong direction.
 
 
  a fraction of a percent
  Posted by: nickjc on Feb-27-13 1:44 PM (EST)
is all you can hope for with surface treatment. On the other hand, assuming training is all done, improving your drafting/wake riding skills can give you a 10-20% boost.
 
 
  Winters
  Posted by: CEWilson on Feb-27-13 2:18 PM (EST)
John Winters, the Shape of the Canoe, has a cogent discussion of surface friction, pgs 21-22.

The formula is K=14/v, K being grain size in mils, v being in ft per second. He states a grain size of 3 mills starts increasing friction at the 3mph pace.

Bringing the pace up nearer race speed, 10 fps suggests we need a cleaner surface than that, more like 1,5 mils to minimize skin friction. 400 grit paper is 23 microns=1 mil, 600 grit paper is 16 microns, hence .75 mill, so either will do fine in prepping a scratched hull.
 
 
  Reduce bottom size, bottom size
  Posted by: Glenn_MacGrady on Feb-27-13 2:52 PM (EST)
Best way to speed up the canoe's bottom is to reduce its friction and drag by reducing the immersed bottom size.

Best way to do that is to reduce the size of the paddler's bottom.

So a paddler should lose 20% of body weight, use carbon paddles, and get a bow partner who is a Dior lingerie model. It will also help if she can filter silty water using the wet t-shirt method while polishing your bottom.

http://www.collectorsweekly.com/articles/wp-content/uploads/2012/07/canoe-pinup.jpg
 
 
  Thanks again
  Posted by: davavd on Feb-28-13 6:48 AM (EST)
Thanks for all the info, everybody, especially the "been there did that", Pirate. I'll try to stay clear on the first turn.
 

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