speed sanding bottom.

[addgasgofast]

I am interested in thoughts,opinions and info on speed sanding the bottom of a boat. Eg. does it work? what grit of paper? any info is appreciated thanks.

[Mark75H]

what is speed sanding?

[addgasgofast]

this is the sanding of the aft 3-4 feet of the bottom of the hull. It is done to help reduce the tension of the water to the bottom. this in turn can give more speed. Eg; less drag=more speed and quicker acceleration. this trick was told to me by and old racer. I am looking for the info on the propper grit of paper to use. he said that at one time mercury had/did a bulletin on this procedure.

[Mark75H]

Speed record boats built by Darrel Sorenson are finished as smooth as glass. Darrel's boats hold a lot of APBA speed records. You can listen to whoever you choose, I choose the man who builds the boats that set speed records.

[Winger Ed.]

I'd tend to defer to Sam on this one.


I have no idea how effective it is, but I used to know a guy who ran (mud sucking) jet drag boat that did it. He used 600 grit 3M wet or dry. It was sanded just enough to break the gloss.

Being sanded that lightly, if it doesn't do ya any good, you could just re-polish the gloss back up.

[Gordie Miller]

.

[Mark75H]

There is such a thing as laminar adhesion, but the boundry layer is so thin it is insignificant. Flat and smooth is the way to go. If the laminar adhesion boundry layer were significant props and lower units would be dimpled.

When a significant number of speed records are held by rough surface equipment I'll be convinced. Until then I say that theory belongs with snake oil.

[Gordie Miller]

a golf ball has dimples that are clearly visible to the naked eye. Take note of the finish on the Sportmaster gearcase, not only is it NOT a mirror finish, it is quite rough by gearcase traditional standards. I certainly don't think a golfball type surface is what we are after but a mirror finish is not the answer (IMHO) either. The bottom steps in most HP boats of the last ten years or so would tend to support the laminar adhesion principle. Bear in mind, these are basically theories as we (to the best of my knowledge) do not possess data acquisition equipment capable of telling us for sure what is best.

[Ospreyproduction]

I must agree with Gordie on this one.

[Dave S]

How about Tunnas???

[addgasgofast]

thanks for the info on the 600 grit w/d. I saw r. summerford sanding the starboard sponson and waxing the port sponson on his stv prior to a race. he said it helped it turn left. Yes this sanding has to do with laminar adheasion,as per.the finish on the sportmaster and speedmaster cases. also the speed coatings have a satin finish. It could be snake oil but sand paper is cheep and getting more HP is not. So I will try it at worst I will buff back to glass finish. Thanks again and if any body has any more info or test this them selves please post .

[Shaun Torrente]

I am with gordie also... on my boat i sand with 600 then do 1200 and a final of 2000 grit.....

Shaun

[Dave S]

That sanding is rite. A old Smart boat racer,who worked at interlux told me to take a wet rag and push it on both surfaces to see which is better. A easy test.

[Mark75H]

Next time I'm racing across a wet rag I'll remember that

[Dicky]

Have you ever tried drag racing belt sanders? Its a lot of fun. You need a good belt sander, 100 ft of drop cord, 100 ft. of hard surface and a power outlet. Tip-- 40 grit to get off the line fast, 100 grit for better top end. Practise pushing the plug in the socket at the green light, for good reaction time, use lite weight drop cord.