Sanding a boat bottom with an electric drywall sander

[Dave Cole]

I have a pole mounted electric drywall sander with a 9"disk.  It's a Harbor Freight unit and it has a vacuum hookup which should collect a lot of the dust, I hope.

The last few years I have been using an electric orbital sander with a 6" disk to do the deed but the dust goes everywhere.  Not a fun job. 

Has anyone had any success or failure in using a drywall sander to sand their boat bottom? 

Dave

10M #26

[Jeff Griglack]

Are you sanding to rough up the solid base of paint before adding new coats, or are you sanding to remove the paint down to the gel coat?  If you are removing many layers to get things down to the gel coat, I sure hope you've been doing your shoulder exercises.  I hired somebody to soda blast my boat when I did that.

This is how I rough the surface for new coats of paint:  In the past, I have used a drywall pole sander with a sanding screen (non-powered).  What I would do was to hose the bottom down and then wet sand it, so no dust.  The yard where I store the boat now doesn't like that, so I bought a 6" random orbital sander from Harbor Freight and attach it to a shop vac.  I do not get any dust, but I still wear a full face mask and Tyvek suit.

Hope this helps,

Jeff

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| Jeff Griglack             "Jabberwocky" P-365 #269

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| "Don't take life so serious, son, it ain't nohow permanent"
|                   - Walt Kelly
| 'Years ago my mother used to say to me, she'd say, "In this
| world, Elwood, you must be" – she always called me Elwood –
| "In this world, Elwood, you must be oh so smart or oh so pleasant."
| Well, for years I was smart. I recommend pleasant. You may quote me.'
|               —James Stewart as Elwood P. Dowd
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[Dave Cole]

Just normal yearly bottom coat paint update.  I get a few chips in places and need to sand it thin before I put on more paint.  Im trying to minimize bottom paint as I have realized that I just need to cover thin areas in order to get through a season.  Most of it wont get painted.  Some of the paint probably has 4 seasons on it and it still works.   Ive been using Blue Seas 25% copper.

I didnt know Harbor Freight had a 6" orbital with a vacuum hookup.  That would be almost ideal.  I like the drywall sander idea but I think the 9" disk is on the big side.

I have used a drywall pole sander before, but never wet. 

Thanks,

Dave

10M #26

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[Dan Pfeiffer]

If you can, get a super-soft pad for the sander.  I have one for mine and it follows the hull contour very nicely.  It's a soft foam insert that goes between the sander Velcro pad and the sand paper.  Maybe 3/4" thick with holes so the dust extraction still works. 

If you can get one for that 9" rig it will make short work of the sanding.  And it has lights round the rim so you can run it at night. 


Dan Pfeiffer

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[Dave Cole]

I have a nice soft pad for my 6" but no vacuum setup.   Which is difficult even with a mask and full coverage.   Dust goes everywhere.

The 9" drywall sander pad is a bit over 1/2" thick foam and its very soft.  This might be a good solution,  at least for the flatter areas.  Plus being able to sand at night could be an advantage.  😁.   Ive done crazier things.  

Ill take a few different sanders.  Ill report on the drywall sanders effectiveness.  

Dave

10M #26

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[Jeff Griglack]

Dave,

I made a mistake.  The sander is 5 inch, not 6 inch.  This is the one I got, but it was cheaper when I bought it:

https://www.harborfreight.com/28-amp-5-in-random-orbit-palm-sander-63999.html

Also, you can get an adapter to attach it to a shop vac like these:

https://www.lowes.com/pd/Shop-Vac-All-In-One-Attachment-Adapter/5013192279

I have never needed a soft pad for the contours, but it might make things easier.

What I liked about wet sanding the bottom was that there was no dust and no need to wear any protective equipment.  Wet it down, pole sand it with a sanding screen, wash it down afterward, and occasionally wash down the sanding screen.

Anyway, I hope this helps,

Jeff

------------------------------------------------------------------
| Jeff Griglack             "Jabberwocky" P-365 #269

------------------------------------------------------------------
| "Don't take life so serious, son, it ain't nohow permanent"
|                   - Walt Kelly
| 'Years ago my mother used to say to me, she'd say, "In this
| world, Elwood, you must be" – she always called me Elwood –
| "In this world, Elwood, you must be oh so smart or oh so pleasant."
| Well, for years I was smart. I recommend pleasant. You may quote me.'
|               —James Stewart as Elwood P. Dowd
------------------------------------------------------------------

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[Dave Cole]

Thanks Jeff for following up.

I was trying to figure out which sander you had.

This is the one I have.  It has plenty of power.

https://www.harborfreight.com/57-amp-6-in-short-throw-random-orbit-da-polishersander-64528.html?event_id=182713&utm_source=google&utm_medium=cpc&utm_campaign=12189147054&campaignid=12189147054&utm_content=123858115424&adsetid=123858115424&product=64528&store=111&gad_source=1&gclid=Cj0KCQjw3tCyBhDBARIsAEY0XNlQje5T7ASjKzzklbFdDX2n7uX9gRkEWjeqVnH_-iu3M6x9q0DzXEIaAlzuEALw_wcB

I was hoping to sand it today, but heavy clouds and frequent rains prevented that from happening.

 I guess if I was wet sanding I could have ignored the rain.  

Im going to try tomorrow, but there is a chance of rains again.  Ill bring wet sanding gear as backup.

Dave

10M #26

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[Guy Johnson]

I have a Festool 6" (150mm) Random Orbit sander with dust collection. It's 10+ years old now and works well. 

I use dust bags inside my small rigid shop vac to collect the sanding dust. 

Guy

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From: pearso...@googlegroups.com <pearso...@googlegroups.com> on behalf of Dave Cole <dave...@gmail.com>
Sent: Monday, May 27, 2024 8:57 PM
To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Subject: Re: [pearson ] Sanding a boat bottom with an electric drywall sander

 

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[Dave Cole]

Festool; I probably should have bought one of those 10 years ago.  

What do you mean by "dust bag"?

I have one of those small Rigid "toolbox" style shop vacs.  It takes a cartridge style filter.  No dustbags available that I have seen?   Am I missing something?

Dave

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[Guy Johnson]

You can add a collection bag to most shop vacs, it has a rubber seal that stretches over the inlet. 

Here's an example. 

https://www.homedepot.com/p/RIDGID-High-Efficiency-Wet-Dry-Vacuum-Dry-Pick-up-Only-Dust-Bags-for-Select-12-to-16-Gallon-RIDGID-Shop-Vacs-Size-A-2-Pack-VF3502/100390230?MERCH=REC-_-rv_gm_pip_rr-_-304359484-_-%7B%7BproductId%7D%7D-_-N

Guy

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Sent: Tuesday, May 28, 2024 10:02 AM

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[Guy Johnson]

I should add that I leave the filter in place when using the bags. 

Guy

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[Peter McGowan]

Same here, Festool, specifically the Rotex 150 which can do random orbit (which I use mostly between coats - if they've cured - and requires only a light grip) and rotary  "beast mode, lol" where you need to have a firm grip with both hands or it'll take you along for the ride.  Rotary mode combined with a high quality 40 grit (Norton, Mirka, etc.) turns the thing into as close to a vacuum attached grinder as you'll get.  On that note, years of sanding and I'm consistently surprised at how much faster things go with regular changing of disks.  I sort of keep an internal clock going these days on how much I get done in 5 minutes with a new disk.  When I'm getting half that done, I change the disk and give the shoulders a rest.   I agree that bags in the vacuum make for faster progress (and less mess) than filter alone.  I usually skip tight corners (top of keel stub, mostly) with the 6" and return with a smaller 5" sander.  I use paper wrapped around a noodle for the rest.  I always seem to end up covered in paint dust by the end of it, mostly when I'm working the bottom part of the hull and it's easier to kneel down and press the sander up above my head/shoulders than reach out in front of me and press up.  I can tell by how frequently I need to clear the goggles!  Might be that I've been working inside, if I was outside the breeze might be sufficient to avoid the dust falling directly downwards.

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[Dave Cole]

Thanks Guy,

I have another vacuum that uses those.

I thought perhaps someone made a sock that goes over the cartridge.

Dave

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[Jeff Griglack]

Thanks, Guy, I'll look into the bags as well.  I have just been using an old, 6 gallon wet-dry vac that I picked up at a yard sale for $5 instead of my "good" (is that an oxymoron) shop vac.

I have also used a filter system that was designed for drywall sanding.  It has a 3 gallon bucket of water and a hooka type of system to trap most of the dust in the water.  However, then you have to dispose of something that is considered toxic water.

------------------------------------------------------------------
| Jeff Griglack             "Jabberwocky" P-365 #269

------------------------------------------------------------------
| "Don't take life so serious, son, it ain't nohow permanent"
|                   - Walt Kelly
| 'Years ago my mother used to say to me, she'd say, "In this
| world, Elwood, you must be" – she always called me Elwood –
| "In this world, Elwood, you must be oh so smart or oh so pleasant."
| Well, for years I was smart. I recommend pleasant. You may quote me.'
|               —James Stewart as Elwood P. Dowd
------------------------------------------------------------------

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[Al Taylor]

Boatworks Today has shown a dust separator for sanding fiberglass, which is insane with clogging standard filters. I think this is similar to what he uses, and the price is right. All you need is a sander that has a vacuum attachment.

https://www.homedepot.com/p/Dustopper-PRO-High-Efficiency-Cyclonic-Dust-Separator-12-in-Dia-with-2-5-in-Hose-36-in-L-with-2-High-Flow-Sweep-Elbows-HD12B/322662836

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[James Weiner]

First thanks for this thread guys.. I am about to begin my first bottom paint restoration project.  

Second, I also have a "water trap" dust collector that Home depot sold years ago for drywall sanding.  Its nothing more than a small 2-5 gallon covered bucket with an inlet and outlet.. the inlet has a tube that goes 1 inch below or so close to the surface of a gallon or so of water in the bucket.. (so the air bubbles through). The outlet goes to any almost vacuum (I used a shop vac)  It works well and collects the vast majority of the dust in the water (without clogging the vacuum filters).  I guess I will have to get that out when I start sanding. 

Jim (P26)

[Dan Pfeiffer]

I also have a Festool RO150.  Best sander I have ever had and its random orbit mode is also ideal for polishing. 

It is a very aggressive sander in rotary mode but, if you want a vacuum attached grinder the Festool RAS115 is significantly more capable and has excellent dust collection (though not quite as good as RO150).  I got mine when I was doing a comprehensive bottom job and the RO150 was not quite up to the task of sanding through the old barrier coat.  The RAS115 was more than powerful enough.  A class above the RO150 for aggressiveness.  But also able to do more damage in careless hands.   But it is an honest grinder.  The variable speed on both these tools and especially the RAS115 is a great advantage in this work.  It tends to miss some bigger bits in the collector shroud but if you slow it down it's better.  And running fast just heats the pads more anyway which wears them out faster.  That's true for both sanders. 

I have a Festool HEPA vacuum (dust collector) and it is amazingly good.  Doesn't stop working until the bag is packed like a brick.  I have also used these tools with a regular shop vac and that certainly works but you loose the anti-static qualities of the Festool system.  When working with the circular saw and the shop vac I could feel the static charge on the hose as it was working. 

Fein has some excellent dust-collecting sanders too.

This Makita belt sander is also a must-have.  Get's into places no other sander can. 
https://www.makitatools.com/products/details/9031


Dan Pfeiffer

[Dave Cole]

My verdict is in.  The drywall sander works really well as a bottom sander.  Having the long handle and the sander head away from me is really nice.  Plenty of power.  I have ablative paint on my boat and it is easily sanded with 120 grit drywall paper.  With no clogging.  Surprising.  

The sander is almost too effective.  I had the speed above 50% and the vacuum couldnt catch the dust fast enough.  Turn it down to a about 1/3 speed and everything works.  Very little dust.  I brought an old shop vac with a big paper bag filter and it catches most of the dust.  

Its much faster than a 6 inch sander and the 9" pad tends to level the surface much better.  A smaller sander is still needed for corners and tight areas, but this is the fastest Ive ever sanded the boat and the surface is much smoother.

Having two hands on the sander handle is much easier than holding the 6" sander.  Less effort overall.   Plus I dont need a ladder to get to the upper portions with the long handle.  Just less effort in general.

Highly recommended.

I dont think it would be difficult for me to strip most of the paint off the hull bottom with this sander. 

I dont need to do that, but I wouldnt hesitate to try it with this sander.

Dave

10M #26

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[Dan Pfeiffer]

Did you have the super-soft pad? 

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[Peter McGowan]

Awesome!  As a matter of interest, why sand off ablative paint?

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[Peter Trunfio]

Same question...

On the 10M...each spring, I scuff the ablative with the brown 3M Doodlebug...and reapply 1 gallon of ablative...focusing on the waterline and leading edges (hull, keel, skeg).

Only reason to sand would be excessive buildup?

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[Dave Cole]

The pad that comes with it is very soft.  About 5/8" thick.  You can use your finger and easily  push through the pad to the backing plate.  I think the hook and loop disks add some rigidity.

But i could easily sand over curves without digging in.   I bought this to do drywall at my daughters house, but she found a very good contractor.  I think I found the machines true purpose.  😄

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[Jeff Griglack]

Glad to hear that, Dave. Maybe I'll try one when my current sander dies. 

Jeff

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[Dave Cole]

My 10M is 50 years old this year and its probably had at least 50 coats of paint.

Ive had the boat for about 10 years.

The original owner was a hardcore racer.  Im sure back then it had a nice smooth bottom job using hard paint.  Then at one time it was stripped and barrier coated.  Then blue hard paint went on over that.  Then someone switched to blue ablative.  Some of the coats appear to have been applied with a broom.  Really rough with serious buildup in some areas.  I switched from blue to red so I could see where I was applying paint and where it was wearing away.  Admittedly, early on I was sanding it hard to try and level the underlying paint but then applying too much ablative.   After realizing that, I have been grinding the bad spots more and more to level the paint.  And then putting down a minimal amount of ablative.  Ive been getting some chipping in some areas due to too much paint so I continue to sand while putting down just enough paint for the season.  

Its amazing how little paint the boat needs for the season which is June to mid November for me.  The boats in Lake Erie.  Zebra mussels are the problem here.  I sanded it hard this year and the sander did a good job to level and further thin the paint.  I only painted the areas where I sanded into blue paint.    I put down 5/8-3/4 of a gallon of red ablative using a 1/4" roller.

On Thu, May 30, 2024, 4:24 PM Peter McGowan <mcgowa...@gmail.com> wrote:

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[Dave Cole]

Fyi, that sander is going for $99 right now if you have a Harbor Freight membership.  I just saw the sign in the store.