Sanding bottom for more speed
 

I heard that sanding the bottom of the boat with 80 gritt with a DA will gain more speed. The same person explained that stripping the paint off the lower unit will have the same effect. If any one has heard of this please say so. I can believe the unpainted lower because all of the XR lower units are bare aluminum. As for the sanding the bottom of the boat I need some more testimony on this one. Especially because his boat bottom was like brand new.

Surface Tension
 

Basically the process of sanding the "Pad" will break the surface tension of the hull and water traveling over it. 80 grit seems a little too agressive. A 320 - 400 grit should work fine. The laminar flow of the water over the hull creates drag, by sanding (scuffing) the hull you are causing air bubbles to reduce the drag of the water over the hull. This all depends on the condition of the hull and speeds you are capable of running.

There are products on the market such as Speed Coat that claim to obtain the same result as sanding. Do a search as I have heard both good and bad reviews of these products.

As for me, I like the protection of my smooth gel coat and a layer of wax to protect my hull. It doesn't seem worth the trade off for 1-2 MPH to potentially cause osmotic blistering of a perfectly good hull.

HOLY CHIT PANTERA !!Your right on !!!WE've been doing this for years most people don't belive it works ,but your right !!!
Graphite spray from w.w Grainger works great as a speed coat on drives and bottoms and is easy to get off later !!!!:D :D :D :D

What is graphite spray? Tell us more Bobby.

If you want to know what the pros do then check out the America cups boats. They polish the crap out of their boats. They used to wet sand them but no more. They have found that a PERFECT, and if you ever look at a 12M boat they are PERFECT, is faster. There is NO WAY I would ever use 80 grit for the sanding. When we used to wet sand the windsurfers a while back it was 600 and then 800 grit

Jon

Jon thats news to me ?

we've used spray on graphite from W.,W. grainger on the web and have always picked up speed !we just do the last 1/4 of bottom and bottom of drive and it cleans up and off boat easy

What Pantera said above is still right to me ,sorry jon you maybe right I just know what works for me :D :D :D :D

Other topic but when I got my boat it had the old fashion black bottom paint on it sanded most all of it of applied new epoxy sealer and sanded and applied HMG Super Speed and gained 1.5 mph on the GPS of the best I had ever seen before. Charlie

Bottom paint will always slow a boat down, so I'm not surprised by your 1.5 mph gain.

All I can tell ya is what they do on the America's cup boats and I can assure you that they spend more money looking for every 1/10th of a knot then we ever will. We are not happy really if we gain 1 mph. They would jump through hoops :D:D We are talking MILLIONS hear :D:D

Jon