Sanding For Speed

[vector mike]

How much speed can you gain by sanding the bottom to loosen up the water from sticking to it. I've heard people say to sand it with 220 from front to rear. I just painted my Vector and hate to sand such a nice finish if it isn't going to gain that much speed.

[Talon2.5]

i have been told 2 MPH but honestly i have never done it nor have i seen it proven from a non-sanded and GPS'ed to a sanded and GPS'ed with an increase

alot of people say it works, there was a thread along time ago that compared a boat bottom to sharks skin and how the sharks skin sheds water and doesnt stick so with that theory i would say mother nature is correct and it should work

hopefully someone that has had it work for them will pop in here and tell us how it should be done

[WATERWINGS]

If you do, you should also sand your gear case, the same idea applies.

It would be hard to tell if the sanding made a difference or the differend air conditions is making the difference.

(since it would take a while to sand, and it would probably be done at night, the next day could just have better conditions)

I sanded mine with 220 or 400??? after I blue printed the bottom anyway.

[Ziemer]

This issue has always been argued, whether a smooth waxed bottom is better or a slightly roughed up bottom (220 sanded) is better.

A few months back I read almost the same article that was in two different boating magazines and the only difference was one said a waxed smooth bottom is better and the other said a slightly roughed bottom was better. Who knows...

I've also used a speed coat on the last 4 ft of the hull which seems to work good, however I don't have any hard GPS numbers. It's a Teflon based product that leaves a rougher finish and water runs right off it.

I would also think a smooth gearcase would be better. The object to roughing the surface is to aereate (sp?) the hull, break it away from the water, which to me would be a bad thing on a gearcase. We all know how fun a blow-out can be.

[WATERWINGS]

David Carver runs unlimited outboard (139.___ MPH 1/4 mile)

sands his gear case (no blowout) and says the best he has found so far is merc. grey primer sanded with 220.

[vector mike]

I too primed my gearcase with epoxy primer and sanded it with 220 but am hesitant to do it to my freshly painted bottom. :eek:

[Ryan140]

Never fooled with sanding bottom. When I was 15 or so I waxed the bottom of my 15' checkmate, took away a few mph. I did however remember Jay Smith (I think it was him) say he puts RainX on his boats. Sounds like a good idea Im gonna try it.

[Wile E. Coyote]

I can tell you what I know. When I got my HST it was manufactured in 1987, the bottom had never been worked. When I rigged it and set it up, after fiddeling with the set up it just would not respond to the trim inputs, and seemed stuck to the water. I pulled the boat and wet sanded the bottom, at first with 220 grit to remove all the orange peel from the gel and to straighted minor imperfections, and finished with 320. Only the last 4 feet of runnin surface tho. Went back to the water and what a difference! night and day, the boat busted a much better hole shot and responded to trim imput all over the rpm range. Not so sure about any (if any) top end gains but it sure dont stick to the water no more. Thats a fact!
Bill

[Reese]

when I sanded my bottom.

Of course those gains had nothing to do with the final sanded finish...it was all due to the fact I straightened everthing out.

Your boat won't know the difference between a freshly painted surface and 220 grit sanded finish...if you don't want to ruin your freshly painted bottom don't sand, you won't see any gains.

What everyone is fighting is the boundary layer that exists on the surface of any object traveling through liquid or gas. I suppose if you finished a boat bottom with 36 grit vs. 220 grit you might see a 1/2 mph but otherwise it ain't gonna happen.

Logic says a smooth finish is faster than a rough one...reality doesn't always support logic.:D

[vector mike]

I DID IT! I sanded my freshly painted paint. It is only the bottom that no one will ever see anyways. I figured while it is still upside down I might as well do it. If there is a gain to be had that I might as well do it because it is free and if there isn't any gain it definately can't hurt. :D