Removing Fiberglass - Cabinet Scraper?

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83glt
Posts: 36
Joined: Mon Jun 06, 2005 8:58 am

Removing Fiberglass - Cabinet Scraper?

Post by 83glt »

In short the fiberglass job on my first canoe was lousy. It's blotchy, clouded, streaky, and just plain ugly - at least to me. Anyone who's a non-builder that sees it says it looks amazing, but I know how beautiful it could have looked had the fiberglassing been done right. Anyway, I'm not asking for advice on whether I should re-glass it, or just build another canoe. I don't want to build another canoe. I love the way this one paddles and performs. I like the weight and its lines. I just want the fiberglass to be done right. I've read the posts here and elsewhere about removing glass with a heat gun. My question is, has anyone tried using cabinet scrapers? It seems that one would have more control in spite of the bigger effort required. I'm considering this as a winter project and don't mind taking my time to remove all of the fiberglass back down to the wood and then re-fiberglass the hull. Can anyone provide any insights into using cabinet scrapers vs. heat gun or any other removal method? Thanks very much in advance.
bluedcanoed
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Joined: Thu Jun 08, 2006 7:16 am
Location: Kawartha Lakes

Re: Removing Fiberglass - Cabinet Scraper?

Post by bluedcanoed »

Have you considered just painting it?
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John Michne
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Re: Removing Fiberglass - Cabinet Scraper?

Post by John Michne »

A cabinet scraper would be totally ineffective. Start at one end at the stem and heat the stem with a heat gun. The epoxy will soften, and the glass can be lifted, albeit grudgingly, from the wood. Work a putty knife under a small section as you go. When you have lifted enough glass so that the putty knife is difficult to maneuver, stop and cut the loosened cloth off with a utility knife. Don’t try to pull the glass away, or you will tear out the wood. Only lift it with the putty knife when softened. The epoxy will reharden when the heat is removed, and can have sharp edges. Gloves recommended.
There will also be a sweet smell, but I don’t know what it is. I am able to write this, so it probably isn’t toxic (to me, anyway). A facemask with a carbon canister is suggested – your call.
The hull will be rough when you are done. Sand the remaining epoxy off and reglass. Don’t overdo the sanding – it was done once before when you built it. You don’t want to remove any wood, just get all the epoxy off.
- John
Rod Tait

Re: Removing Fiberglass - Cabinet Scraper?

Post by Rod Tait »

Yup. Heat is what you need. I also have some info written on my web site on my "How To" page titled stripping old glass - major repairs.
http://www.orcaboats.ca
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Patricks Dad
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Re: Removing Fiberglass - Cabinet Scraper?

Post by Patricks Dad »

I've never done this before (so take what I say with a grain of salt)... but I would worry about getting all the old epoxy off (which would probably drive me to over-sand) - my wife calls me "Randy, Randy, Oversandy"...

If you don't fully sand off all the old epoxy, will the new epoxy blend in nicely with the old anyway avoiding appearance issues? If so, that would be a great comfort to know...Or will streaks of old epoxy left behind cause a "visual disturbance" once re-glassed which might look worse than the situation you have now? In that case, a thorough sanding and inspection would be in order (maybe a pre-coat of epoxy before glassing to judge the sanding job - if you hadn't planned to pre-coat anyway).

I'd be very interested in how it turns out (I'm thinking of starting a restoration of an old 1940's rowboat that has been glassed)...

thanks
Randy Pfeifer
(847) 341-0618
Randy.Pfeifer1@gmail.com
83glt
Posts: 36
Joined: Mon Jun 06, 2005 8:58 am

Re: Removing Fiberglass - Cabinet Scraper?

Post by 83glt »

Thanks for the replies everyone.

Yes, I have thought about painting it, but I feel that would be defeating the purpose of having built the cedar strip. The aesthetic potential of the stripping is what makes me want to avoid painting it if possible. For a first canoe I'm proud that I did a really good job of the stripping and matching strips, etc. I just really fell short on the fiberglassing - at least partly due to circumstances outside my control, but also, to be totally honest, due to using an inferior product, or at least inferior use of a product. :)

I think that any visual imperfections resulting from a re-stripping attempt can not come close to how bad it looks now. There are large opaque sections where you can barely make out the wood underneath, and other large areas where the weave is clearly visible. It's just really ugly in its current state - however solid and usable it may be.

So the heat method is the way to go. Why would scrapers be totally ineffective? Is it just that it would take a whole heck of a lot more time? Or is there any other particular reason? I've read lots on how a well honed cabinet scraper can remove lots of material very quickly. I know wood is softer obviously, but can hardened epoxy not also be removed efficiently/quickly with a scraper? What about using the scraper after the fiberglass to remove the remaining epoxy - in conjunction with sanding?

Any recommendations on a particular brand of heat gun, wattage to be used, etc.?

Thanks very much for everyone's assistance! If/when I go forward with this, perhaps I will document the experience with photos, testimony, etc.
Rod Tait

Re: Removing Fiberglass - Cabinet Scraper?

Post by Rod Tait »

When you heat the resin, the glass can literally be pulled out of the resin, leaving resin on the wood. If the old glass comes out cleanly then you are left with a boat that is basically pre-coated. If there are sections of bare wood and others with resin, then you will have to sand back to wood as it will leave blotchy areas if just re-glassed. If it is the resin that is the problem, such as different patches of resins, lines from application, etc., then everything needs to be removed.

The better the heat gun the faster- more wattage.

Scrapers can cut through resin quite nicely especially to smooth out before sanding and varnish, but not as effective when you hit the glass fibers. Could be done, but it will take much, much longer. I heat stripped the kayak in my online info in about 2 hours and then sanded for maybe two more.
Whitworks
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Re: Removing Fiberglass - Cabinet Scraper?

Post by Whitworks »

Cabinet scrapers are for wood. You'll find that scraping glass will require frequent sharpening/burnishing. If you want to scrape the only thing that might work is a tungsten carbide scraper but it will be messy and you risk digging into the wood occasionally.

I've removed glass from wood (not on a canoe) and the heat/spatula is very effective and a lot less messy. I would think that the top of a stem would be a good place to start because you have a point of material (unless you've wrapped the stem. in which case you'll have to sand the glass away to the wood at the very front of the stem).

Wave the heat gun back and forth to pre-heat an area from the point to a few inches back using a heat setting which will get the glass hot but not scorch the wood underneath. Apply a little more heat at the point until the glass softens and you can lift it with a spatula.

Wearing a glove, you should be able to pinch the glass and pull it up while waving the heat gun back and forth just in front of where the glass is lifting. I found that since the glass is impregnated with resin, both glass and resin come off together, leaving a fairly even layer of resin on the wood. While you're doing this, keep an area about two inches ahead of the 'lift line' preheated. As you go, keep on cutting chunks of the lifted glass away to keep the work area accessible.

Good luck with it whichever method you use,

Mark
83glt
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Joined: Mon Jun 06, 2005 8:58 am

Re: Removing Fiberglass - Cabinet Scraper?

Post by 83glt »

4 hours to remove: Wow! That sounds promising. I'm sure it will take me longer as a novice and in wanting to be careful, etc. But I was worried this would take much longer.

Thanks again for the advice everyone. I'll report back in a few months when this is actually underway. Happy paddling!
sedges
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Location: georgia

a reason to NOT do this

Post by sedges »

If you peel the boat there will be a resin-saturated surface left. If you sand this down to wood with no resin your hull will be real thin with less stiffness and strength. If you re-glass over the resin-saturated surface you will have only a mechanical bond between the wood and glass. While this bond is still substantial, it will tale less stress to cause delamination.

I would have fun paddling this boat while stripping up another.
83glt
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Joined: Mon Jun 06, 2005 8:58 am

Re: Removing Fiberglass - Cabinet Scraper?

Post by 83glt »

Thanks Sedges, but as I indicated in the first post, I don't want to build another one. I don't have room for 2 canoes anyway. This is a light tripping and leisure canoe. It will never see white water of any significance. So I appreciate your concern, but for the use that it is bound to see I'm not all that worried. I always understood the strength of a stripper to come from the epoxy/glass, and not the wood core. So what difference would the thickness of the wood make anyway?
sedges
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Location: georgia

Re: Removing Fiberglass - Cabinet Scraper?

Post by sedges »

The strength and stiffness of the hull comes from the combination of the wood and glass. The thicker the core the stiffer the hull. Its like an I-beam with the wood being the central member. People are building hulls with 3/16" strips these days, however, so if you are careful it should be OK.

It is always most difficult to sand a hard surface off of a soft one without getting too deep into the soft material while trying to remove a persistent area of hard stuff. Be very careful!

Good luck!
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