Sandblaster for Paint Removal from Fiberglass?

[AlexfromRI]

Hi iBoats, hope you can help me out here.
I'm in the beginning stages of restoring a 50 year old sears gamefisher and converting it to a shiny "new" flats boat. It's in rough shape, but I'm devoted to it, and have grand plans down the line. In the meantime though, I have to get the paint off.

The gents who owned it for the last 50 years were not discerning about materials used to patch and paint this boat. I've been spending weekend after weekend with my orbital sander and 36 grit pads removing at least four layers of old, thick, and sometimes rubbery paint. I'm getting sick of it, and looking for a faster route. Would a sandblaster get the job done? I'm loathe to rent one just to find out, but would be happy to shell out if it means stripping the rest of this paint off in a day. I can only work outside and I'd love to use as much of our October weather on fiberglass repairs as I can.

 

[dingbat]

Sand blasting would work, but you might look into soda or walnut shell blasting as well.

 

[ahicks]

Sand blasting makes a huge mess and is not a lot faster than 36 grit. Suggest you try some good paint stripper.

 

[AlexfromRI]

Sand blasting would work, but you might look into soda or walnut shell blasting as well.

Good point! I'm interested in whatever abrasive is the most effective. Is there a reason why soda/walnut shell might be better?

 

[AlexfromRI]

Sand blasting makes a huge mess and is not a lot faster than 36 grit. Suggest you try some good paint stripper.

I'm okay with a mess, but it's disappointing to hear that it's not any faster. What's your experience with paint stripper? My understanding is that it's incredibly toxic so I'm not sure I want it in my backyard.

 

[dingbat]

Good point! I'm interested in whatever abrasive is the most effective. Is there a reason why soda/walnut shell might be better?

A lot of variables involved. Size of compressor, nozzle size, blast media, etc. Can't see it taking more than a couple of hours at best. Much cleaner finish than stripper or sand paper.

How big is the compressor? Can't get too aggressive or you'll remove too much of the fiber glass. Use soda and Walnut shells to remove bottom paint from fiber glass hulls. Works well with minimal removal of the glass substrate.

https://www.youtube.com/watch?v=NYbEhytnceM

 

[gm280]

My $0.02 cents worth. I have sandblasters, both a floor model cabinet version and an outside hopper version. IF, and that is a really big if, if the paint is rubbery, the sand blaster isn't going to be your magic bullet to removing it. The rubbery paint will absorb the sand velocity and not remove the paint like hardened paint would come off. Most people use 36 grit flapper or even regular sanding disks on an angle grinder for removal. And it is a very messy, smelly, itchy job. Actually the worst part of refurbishing any boat.

Paint strippers do work pretty well and no more toxic then mere gasoline. Of course always use the appropriate safety equipment whatever method you select. And if you go the paint stripper route, make sure you watch for the stripper dissolving the fiberglass when you get close to it after removing the paint. Some strippers state that it can dissolve epoxies and fiberglass resins. So read the can and obey the instructions. You will still have some sanding to do after paint stripper as well.

One other thing you may or may not have contemplated about sandblasting, you have to have a really good compressor to make it work correctly. If you already have such a compressor, then you are setup. I like using Black Diamond medium grit in my blasters. Tractor supply sell its around ~$10 per 40 pound bag and you can get it in fine, med or course grit as well. Sand is a ton slower, but Black Diamond is coal ash and cuts paint and rust pretty well if the paint isn't soft. And to keep from running out of the grit, lay down a large tarp and collect the grit and reuse it. It can be used over and over until you run out after a few reuses. You never collect 100% of it.

Hope that helps you some. You are doing the worst part of refurbishing any boat and it does get old and takes a lot of time. But once it is done, you will feel that self satisfaction of knowing you did it! Keep us informed of your progress and post some pictures for us to see. We love pictures...

 

[Scott Danforth]

first, sand blast media doesnt know where paint and gel end and where the fiberglass starts.

low pressure and media like baking soda or walnut shells helps, however that exponentially adds time.

fiberglass is not much harder than paint, so think of it like sand blasting sheet metal with paint and body filler and your trying to save the body filler

24 grit is faster at grinding than 36 grit

if you want fast on a boat restoration, start with a new boat that only needs a re-power

I spent 4 weeks sanding bottom paint with a DA and 40 grit. I went thru 1 compressor (yeah, burned that puppy out), 1 DA (burned out the bearings, and 3 rolls of 40 grit, and 1 roll of 80 grit.

you need a minimum of a 5hp compressor for DA work and if you are blasting for any speed, you need about 25hp screw compressor.

if you really want it blasted, I would take the boat to a local company that does blasting for auto restoration. they should be able to remove the paint with marginal fiberglass damage, and do it quickly.

 

[ahicks]

I'm okay with a mess, but it's disappointing to hear that it's not any faster. What's your experience with paint stripper? My understanding is that it's incredibly toxic so I'm not sure I want it in my backyard.

I did an entire fabric covered airplane. A huge project that required all glue and paint be removed from hundreds of pieces not the least of which was the fuselage/frame. I started off sand blasting, the huge mess after many hours, and tried paint stripper. I found it went much quicker, with way less mess in the enclosed area I was in.

As far as toxic, I didn't find it that bad at all. Painting was WAY worse! If you're concerned about the drippings, just spread out a plastic drop cloth to collect them.

Walnut shell media is often used when working on engines. That sand can, and will, find it way in and be pretty much impossible to remove completely. Rather than risk it, walnut media is used.

 

[Faztbullet]

Find someone who vapor blasts...not messy at al. Customer had a 14ft FD aluminum boat blasted for $75...

 

[gm280]

Post some pictures of what you are working on so we can understand it better and offer maybe better methods... JMHO

 

[AlexfromRI]

Post some pictures of what you are working on so we can understand it better and offer maybe better methods... JMHO

Good idea! Hopefully this gives an idea of what I'm working with. The top layer of green paint is the rubberiest by far. The yellow bottom coat is hard and thin - would definitely flake off easily if it weren't buried under the other coats. From what I can tell, there's at least two coats of the green paint, and one of the yellow. Every so often I come across a brown color between the green layers that I can't identify. I can't confirm that any of it is marine paint.

The keel is a pita too... the guy said he "redid it" but that appears to mean he did a hack job repairing the fiberglass, painted over it, and then slathered some kind of resin all over it when he was done. As you can see, there's fiberglass work to be done, so I'm eager to get it stripped down. I can't complain too much though! I did want a big project where I basically rebuilt the boat from the ground up, and here I am.

I'm not near the boat atm so I can't get photos specifically for this thread rn, but this video might show more detail.
https://youtu.be/gupiZAtSoCA

 

[gm280]

Good idea! Hopefully this gives an idea of what I'm working with. The top layer of green paint is the rubberiest by far. The yellow bottom coat is hard and thin - would definitely flake off easily if it weren't buried under the other coats. From what I can tell, there's at least two coats of the green paint, and one of the yellow. Every so often I come across a brown color between the green layers that I can't identify. I can't confirm that any of it is marine paint.

The keel is a pita too... the guy said he "redid it" but that appears to mean he did a hack job repairing the fiberglass, painted over it, and then slathered some kind of resin all over it when he was done. As you can see, there's fiberglass work to be done, so I'm eager to get it stripped down. I can't complain too much though! I did want a big project where I basically rebuilt the boat from the ground up, and here I am.

I'm not near the boat atm so I can't get photos specifically for this thread rn, but this video might show more detail.
https://youtu.be/gupiZAtSoCA

What I just saw in that video is NOT paint by any stretch. And sadly, I honestly don't see any sandblasting removing that stuff. But neither do I think stripper will as well. It looks like someone used roofing tar to seal leaks? I can't tell for sure, but it kind of looks that way. Maybe a heat gun and putty knife would be the better choice to remove the tar-ish stuff. Could give it a try and see... IDK!

 

[JASinIL2006]

Maybe it’s Flex-seal? Or something like that?

 

[Scott Danforth]

Good idea! Hopefully this gives an idea of what I'm working with. The top layer of green paint is the rubberiest by far. The yellow bottom coat is hard and thin - would definitely flake off easily if it weren't buried under the other coats. From what I can tell, there's at least two coats of the green paint, and one of the yellow. Every so often I come across a brown color between the green layers that I can't identify. I can't confirm that any of it is marine paint.

The keel is a pita too... the guy said he "redid it" but that appears to mean he did a hack job repairing the fiberglass, painted over it, and then slathered some kind of resin all over it when he was done. As you can see, there's fiberglass work to be done, so I'm eager to get it stripped down. I can't complain too much though! I did want a big project where I basically rebuilt the boat from the ground up, and here I am.

I'm not near the boat atm so I can't get photos specifically for this thread rn, but this video might show more detail.
https://youtu.be/gupiZAtSoCA

you have more issues than the keel

the rolled gunwale is the structure on this boat and its missing at the transom. the hull is rated for only a 7.5hp motor

 

[gm280]

An easy way to tell if it is some type roofing tar is to take some mineral spirits on a rag and see it you can rub any of it off. If the rage turns black...BINGO! As for how to remove that, again try a heat gun and putty knife to remove the majority of it and then mineral spirits to dissolve the rest as you go along...

 

[AlexfromRI]

What I just saw in that video is NOT paint by any stretch. And sadly, I honestly don't see any sandblasting removing that stuff. But neither do I think stripper will as well. It looks like someone used roofing tar to seal leaks? I can't tell for sure, but it kind of looks that way. Maybe a heat gun and putty knife would be the better choice to remove the tar-ish stuff. Could give it a try and see... IDK!

Certainly not! Whatever the tar stuff is, that spot in the bow is the only place I've run into it so far... I hope there isn't any more but I can't say for sure. With everyone's input, I'm thinking more and more that I'll stick to sanding to get all the paint off. Seems like it's supposed to suck, so I don't mind putting the work in. I'll definitely try a heat gun for the tar, thanks for the idea! The good thing is that this boat was meant to be a huge learning opportunity, and so far it has been. It seems like every time I see a video or read a forum post describing how not to repair a fiberglass boat, I go outside and find a perfect example of what those bad repairs look like down 20 years down the line!

Edit to say: didn't notice page two in my initial response. I will absolutely test out mineral spirits too.

 

[AlexfromRI]

you have more issues than the keel

the rolled gunwale is the structure on this boat and its missing at the transom. the hull is rated for only a 7.5hp motor

That's an understatement. I do have the missing gunwale. It broke off while in the POs care, and is safely sitting in the cooler waiting to be reattached when I get to the repairs. I hope that's not going to be a problem, will it? I'm redoing the entire transom as it is. The wood piece that fit into the center of it is rotted out, but I'm going to use it as a template for a new one and then use plywood across the entire transom so that it's way stronger than when it was built. I have a strong sense that the transom was flimsy even when brand new.

 

[Scott Danforth]

no mater what you do with the boat and transom, your limited to 7.5hp based on transom width, boat length, etc.

the boat was intended to be thrown on the roof of a 60's station wagon on a fishing trip to a local pond.

 

[AlexfromRI]

no mater what you do with the boat and transom, your limited to 7.5hp based on transom width, boat length, etc.

the boat was intended to be thrown on the roof of a 60's station wagon on a fishing trip to a local pond.

That's fine by me - I'm planning on using it to fish salt marshes and maybe the bay on calm mornings. Needed something light to suit my towing capacity, as well. 7.5 hp should more than do the trick, and is right in my budget. My concern now is mostly about the gunwale. Will it still offer the necessary structural support when I reattach it (provided I do the repair correctly and with quality materials)?

I do also plan on reinforcing the hull with additional fiberglass and/or bulkheads. I should start a build thread for this...