Drywall sanding rig for bottoms?

[Cheechako]

I dont think you need the length. It weighs nearly 12 lbs too! SO extending it out is going to be very hard on the arms! Most of a boat bottom you reach fine with a disc sander. The rest of that handle on that drywall sander is just going to be in the way and make sanding a clumsy affair.

[jharding]

when I had to do a blister job and remove all paint and a layer of glass, I used a variable speed grinder which normally has a 7 inch disc, which grinds about a 3-4 strip when using it tilted up, this tries to dig in if not careful and takes forever. I went to McMaster carr and ordered 17 inch floor sanding discs, I think 36 grit if I remember right, and made a lexan backing plate, that baby did the job and because it was so much bigger it didn't dig in, it was a little more dangerous, once you got it up and spinning you didn't want to hit a thru hull or it could kick back, I wore a full face respirator which took a few hits. Hope to never have to do that job again. Put on copper coat 12 years ago and don't see ever having to do a bottom job again.

[twofingerpoi]

I recently did my first bottom job on a boat that I own. Next time I will pay extra to have soda/sand blasting done to minimize the sanding effort. I tried using drywall screen by hand on ablative and it was too much work, so switching to DA sander with 60 grit too strip as much as possible. Battery powered tools weigh more and don't last long enough, so lots of battery swapping and waiting to charge. Grinder with flap wheel was fast and useful for barnacles and blisters. My first consideration would be how long i have to hold a tool at some awkward angle. I noticed that the pros in the yard were using 6 or 7 inch polisher/sander. I have a 7 inch polisher and will probably get 7" hook and loop sanding discs next time. Make sure to wear good gloves, coveralls, cap and respirator.

[capt jgw]

Originally Posted by twofingerpoi

I recently did my first bottom job on a boat that I own. Next time I will pay extra to have soda/sand blasting done to minimize the sanding effort. I tried using drywall screen by hand on ablative and it was too much work, so switching to DA sander with 60 grit too strip as much as possible. Battery powered tools weigh more and don't last long enough, so lots of battery swapping and waiting to charge. Grinder with flap wheel was fast and useful for barnacles and blisters. My first consideration would be how long i have to hold a tool at some awkward angle. I noticed that the pros in the yard were using 6 or 7 inch polisher/sander. I have a 7 inch polisher and will probably get 7" hook and loop sanding discs next time. Make sure to wear good gloves, coveralls, cap and respirator.

The only cordless tool I have is a 3/8" drill motor. Everything else is corded including another 3/8" and a 1/2" drill. I only use the cordless for little quick jobs. If I have a big job away from 120v power, I bring my portable generator. The convenience of cordless only goes so far.

[twofingerpoi]

I have a full set of cordless tools that tend to be my first choice for most projects but I still have several corded tools including a hammer drill, sander, circular saw but use them infrequently as the power improves in cordless tools and the collection of batteries and Ah increases.

I used a 5" corded DA sander for most of the prep on the bottom job and it was a pain. Dragging the extension cord around, and holding the sander over my head for hours.

Another tip is to get a mechanics stool to sit on, preferably one with wheels that can roll across the tarp in the gravel yard.

[j.g.evans]

I have used the open mesh, 8x11, dry wall, sheets on ablative anti fouling paint for many years, I was not trying to remove all the paint, just scuff it up before new paint. I just held it in the palm of my hand. I wet the hull and rinsed the sheets often. It easily removed enough material. THERE WAS NO SANDING DUST IN THE AIR TO BREATH. I have also used a very course 3 M pad attached to a block to wet sand. It works well too.

[Dockhand]

Not sure what yards you have been in but on East Coast I have seen several yards using them. They have used it on my boat. Just wet the surface and a light sanding and rinse, let dry a day before painting. One guy sands and paints a 45’ bottom in a day.

[Coltrek]

That would probably be me. I agonized over this for several years, as sanding bottoms over most of my life has been the bane of my existence. I searched everywhere, and could find no one who tried it. I didn't want to be the Guinea Pig. The price kept me away initially, and I was afraid the rotary action would end up in gouges. FINALLY Festool came out with their oscillating Drywall Sander a few years ago, and I bit, pretty pricey at $1400. However, I have to say it works quite well, If my bottom was lower it would be a little harder to hold it out horizontally. The suction does help take the load off quite a bit, as long as it isn't too curvy. Amazingly, I can get through the whole bottom with one mesh sanding disk. No Gumming - (Pettit Triton Odyssey) If it was a little darker in the day, you could see how nicely sideways light shows all the imperfections.

https://youtu.be/N7_b9pWDB_s

[thinwater]

[Nord Sal]

Originally Posted by Coltrek

That would probably be me. I agonized over this for several years, as sanding bottoms over most of my life has been the bane of my existence. I searched everywhere, and could find no one who tried it. I didn't want to be the Guinea Pig. The price kept me away initially, and I was afraid the rotary action would end up in gouges. FINALLY Festool came out with their oscillating Drywall Sander a few years ago, and I bit, pretty pricey at $1400. However, I have to say it works quite well, If my bottom was lower it would be a little harder to hold it out horizontally. The suction does help take the load off quite a bit, as long as it isn't too curvy. Amazingly, I can get through the whole bottom with one mesh sanding disk. No Gumming - (Pettit Triton Odyssey) If it was a little darker in the day, you could see how nicely sideways light shows all the imperfections.

https://youtu.be/N7_b9pWDB_s

Interesting video.

I wonder how aggressive those drywall sanders can be compared to an eccentric sander like a Bosch or Festool Rotax? I suspect they're only good for lighter-duty sanding.

I don't think it'd be possible to hold something that grabs like my Bosch (regardless how light it might be) at the end of 2.5-3' lever. It's hard work to hold onto mine even using two hands but the material really comes off.

Also, really ought to consider using a respirator if you're going to sand dry bottom -even if the sander uses vacuum for dust extraction.