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Sanding the bottom for performance?

bigsbetter

bigsbetter

Active member
I've got my boat off the trailer doing some repairs to my trailer. The boat is on a lift in my garage and I'm rolling around on a creeper looking over the bottom. Where the boat sits on the trailer bunks, there's some hard, light brown crispy stuff stuck to the boat. It's only in the 4 spots where the bunks are. I'll try cleaning it off, but I'll probably have to use some sand paper or some kind of scraper or something.
I've heard of sanding the bottom of your boat sideways to airerate the bottom to gain some performance. Is this a good thing? If it can't hurt performance I'll do it, even if I don't gain anything,I'll try it. I just don't want to slow it down. What grit of sand paper do you use?
 
I dont think that sanding the four spots would have any noticable effect on your top end. Although I have heard that sanding is better than waxing. Ide try a 400 grit and work from there.
 
you wouldnt see any difference in speed. allthough sanding does have an effect for higher speed boats.(100+) even then you only see .5 or so mph gains.

just make sure those four spots are not delaminating on you. :thumb:
 
illMATTic said:
if i was at 99.5 mph i would do everything i could to break into the 100's.
Click to expand...

THAT'S RIGHT! If I can gain .5 mph with a 2 dollar piece of sand paper, I'm gonna have to try it. Usally it takes a couple thousand to gain a few mph. And the faster your going the more money it takes to get faster...so it's worth a try.
 
has this boat spent much time in the water? probably just some algee growth - try a bottom cleaner first like slimy grimy, it should do the trick. i'm sure the sanding may help - but you really don't want to get into that. you may have issues selling it later cuz someone will think a poor repair may have been done to the bottom, even though that isn't the case.

for the minor gains you may see (you won't feel .5 mph) i spend your time on other things - perhaps drinking beer?
 
sanding bottom

I spent several hours sanding the bottom om a 1998 2100 after being advised that it was "The Thing To Do" if you want to gain speed. I used 1200 wet dry paper on a block and wet sanded the last 5 feet of the hull just enough to remove the orange peel. You can't see until you start sanding, but it's there. After sanding, I rubbed it out to it's original shine and then waxed the bottom from one end to the other. The gain, 1 mph. Was it from sanding the bottom, did it need waxed anyway? Who know's? But it wasn't that hard to do and even though I couldn't feel it in the seat of my pants, I knew it was faster and that is satisfaction! Plus, I was able to drink beer while working on the boat. Sand for 10min. drink for 20. Boatman
 
ORANGE PEEL???? 1200??? TP might have been quicker.

OK, guys sand bow to stearn, not port to starboard, bow to stearn. Start with 400 grit, then 600, then 1000grit. Buffing is OPTIONAL. Take nice long even strokes with the sanding block. Always make sure to use the gitty side of the sandpaper(I've seen it used wrong).

If you don't want to do it yourself, then bring it here I can do it for $1,200

Feb, 1st Coop's Garage will be open!!!!
 
I'm not worried about my spots where my bunks are, I'll get them out, I'm sure. ,But I'm cunfused on this sanding idea...Some say to sand port to starboard, some say sand bow to stern, some say buff and wax the bottom, some say wax'n the bottom will slow you down...:brickwall:
 
If you are going to sand your hull use 400-600 grit. Sand only in the longitudinal direction of the boat. Save your arm only sand the part of your boat that is in the water at wide open throttle trimmed right out.

If you use too fine a sand paper you will defeat the purpose of sanding. You are trying to stop adhesion. The sanding creates turbulence the boat flies or rolls on the air bubbles created by the sanding of the hull.

On a grander scale this is why your boat runs faster in a slight chop than on a glass smooth lake.

Friends of mine who race boats say for boats like ours it a waste of time but I did it. How much did I gain? It is very hard to see .5-1 mph too many variables.
 
If you just want to get rid of the spots use bottom cleaner, forget the sanding. An acid based cleaner will remove those spots. It is almost certainly algae like Chris said. I had some really bad ones on one of my boats that used to sit on a lift all summer for years before I got it. Nothing seemed to work. Finally tried muriatic acid (very caustic) and they literally wiped right off. No ill effects to the gelcoat.
 
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