water tension

[darryl whitman]

ok guys , I hear from u pro boaters to sand the bottom of the hulls an sponsons to brake water tension from the boat. ok I can see that,
but what about using a grit like micro sand in the final sealing goat
in the areas of the boat? or has any1 dun this?

[ls1fst98]

This has been brought up quite a few times, the fastest guys have said not to sand, they want a mirror like finish. I too think/thought like you.

[ososlow]

What about using a product like NeverWet? I have a couple kits sitting here and I got to thinking if it would be of any benefit to an rc boat. I seriously doubt a sport boater like me could see any improvement from it's use. But I figure since this popped up I'd ask if anyone else has put any thought into it or even better, tried it.

[ls1fst98]

I'd spray it on an esc, but I don't know if it's ev r been used on the hull. I think it'd be different if you were trying to get the last tenth of a mph out of a boat.

[robbo1]

This has been brought up quite a few times, the fastest guys have said not to sand, they want a mirror like finish. I too think/thought like you.

Have I read and understood this correctly?… don't sand? I thought to break water tension and that little more speed sand with a 400grit??!!

[Fluid]

The fastest guys do sand the bottom of their ride surfaces, a mirror-like shine is not wanted. Very very smooth yes, but not shiny. Test by pouring water on the surface, it should not bead up but instead run off in thin sheets.



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[ls1fst98]

Fluid is correct, I misspoke, yes yiu do sand but it should not be rough.

[darryl whitman]

ok . just an idea I wanted some feed back , thanks Fluid for the insight .

[cybercrxt]

Darryl, sand the ride surface of your gp310 with 320 grit wet. if you have any clear coat runs be sure to knock those down with a heavier grit, then sand with the wet 320. Get your edges nice and sharp. Sand with a sanding block to take out any convex or concave spots in the ride pad as those create odd handling of the boat. Scuffing the surface creates air turbulence against the ride pad, spinning the airflow (microscopically) and letting it stay against the ride pad as the water goes across. This technically keeps a tiny layer of air between the ride pad and water...therefore "freeing up" the boat off the water. Enjoy, Mike

[Fluid]

While fluid dymanics disagrees with Mike's explanation of why this works, I wholeheartedly agree with the technique he recommends.



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[darryl whitman]

I thank u for the great info, I'm slowly learning from u guys, I need all the help here because , the guys here in town run nitro , and I want so bad to whip up on them, we are good friends an they help a lot too, But I an 1 other guy r AMPHEADS to them, LOL we get a lot of sh##t, . so in short what ever I can learn here , thank u guys.

[Fella1340]

Scuffing the bottom for more speed is not something I can get myself to buy into. Sometimes though I guess some things just work because they do. Does anybody know how much a boat will benefit from this? Perhaps somebody has done a test or run there boat both ways. Are people seeing actual mph improvements scuffing the bottom? I have heard people stating this is something you should/must do but I haven't found anywhere that speaks of the actual performance gain.
It doesn't change the amount of air entering or exiting the hull or sponson bottom(wetted area) and it seems to me that it would create turbulent flow on the wetted (run) surface. L Laminar flow over the wetted surfaces seems to me the way to gain performance. I am just looking for a little insight into how this works and the net performance gains expected.
I just can't get my head around how roughing up a hull can make it faster. If you were to use 40 grit sandpaper it's obvious the gouges left in the surfaces would surely dampen performance, yet at 400 grit its supposed to help.
Please help me understand!

[kfxguy]

I'd like to see some back to back test results myself. I have read (repeat, read) on tbe Web that one guy did this to his real boat (sanded it as recommended by others) and it slowed down. I considered doing a back to back gps test but my boats are all carbon until I get my fiberglass hatches. I still am nervous about sanding on a beautiful cf hull.

[martin]

Once the hull has been scuffed pour some water on the hull & the water flows over the entire hull surface, leaving a thin layer of water on the hull. Do the same with a shiny polished hull & the water dosnt cover the surface with a thin membrane but beads up. Once scuffed the membrane of water that attaches to the hull slides over the lake water, its the membrane of water that attaches to the scuffed surface.

[785boats]

I still am nervous about sanding on a beautiful cf hull.

So spray a couple of coats of clear lacquer on the surfaces & sand that.

Fella1340.
Have you ever felt a sharks' skin? It's as rough as sandpaper. And yet they are the most efficient high speed swimmers.
The rough surface actually traps a thin film of water to the skin. Water flowing over water has much less resistance than water flowing over a smooth surface. At least I believe that's the theory.
The Olympic swimmers hi-tech swimsuits were based on the same principals, breaking all the records until they were banned.

An aircraft company is experimenting with a coating on a couple of passenger liners to see if the same principal works in air to save on fuel costs.

I sand all the ride surfaces of all my boats. Have done so for years.