Stripping Hull with HEAT Gun
Adam M. Noble
hull with an electric heat gun? Please list any disadvantages or
advantages as to time required and effect on the glass. Also
define type or kind of heat-gun used.
--
--Adam Noble
342 Ling-A-Mor Terrace South | AOL: Rampage24
St.Petersburg, FL 33705 | internet: anoble%dol...@palan.palantir.com
(813)895-2700 | UUCP: ...palan!deep6!dolfin!anoble
tkla...@cc.curtin.edu.au
> Has anyone ever tried stripping bottom paint from a fiberglass
> hull with an electric heat gun? Please list any disadvantages or
> advantages as to time required and effect on the glass. Also
> define type or kind of heat-gun used.
yes, I have done this with an ordinary Black and Decker heat gun, and it
works OK provided you use a bit of caution. I used it on high heat setting
for stubborn bits, low for easy bits. I took several 5 minute breaks to
ensure the entire structure wasn't getting too hot. If it does, the gel
coat starts to get soft but I don't think that is a major problem as you
will presumably be epoxy coating the hull after going to so much trouble
to get the old paint off.
It is a slow process, and only efficient if the bottom paint is thick. If
there are only a few coats of paint to remove then mechanical methods are
quicker. Use good fireproof gloves with the heat gun, and an appropriate
mask with any bottom paint work, it is poisonous.
Kim Klaka
Perth, Western Australia
Stefan Mochnacki
|> In article <ITCMtAc...@dolfin.UUCP>, ano...@dolfin.UUCP (Adam M. Noble) writes:
|> > Has anyone ever tried stripping bottom paint from a fiberglass
|> > hull with an electric heat gun? Please list any disadvantages or
|> > advantages as to time required and effect on the glass. Also
|> > define type or kind of heat-gun used.
|>
|> yes, I have done this with an ordinary Black and Decker heat gun, and it
|> works OK provided you use a bit of caution.
[ ... gruesome stuff deleted ....]
All the books I've read say "NO WAY! Heat guns and GRP don't mix!".
(e.g. "This Old Boat"). I've never seen anybody do it.
Perhaps somebody more experienced can knock this one on the head
for good ... but to me heat-stripping and plastic seems all wrong.
I would think that serious damage is likely: gelcoat softening,
severe stresses, delamination, etc. OK for metal and wood (with care),
NOT for plastic!
Standard methods, in order of preference (??), are:
(1) Scraping with a hooked blade.
(2) Chemical remover (see thread of past few days). Interlux
make a stripper; make sure it's the right one (for GRP).
(3) Sanding (80 grit or finer ALO; hand, finishing or orbital sander).
(4) Sandblasting (NOT recommended unless you are applying
an epoxy barrier system; erodes and damages the gelcoat).
Sanding is usually necessary before applying new anti-fouling.
An interesting twist in more recent literature is that if you have
good gelcoat on the bottom, it is a good idea to put on a couple of coats
of conventional marine enamel before the anti-fouling. Supposed to keep
the osmosis nasties away better than epoxy ... but this "scientific"
result hasn't percolated to many boatyards yet, I suspect.
The CSC-type antifouling (controlled solubility copolymer) is supposed
to be recoatable without sanding (just high-pressure wash). I put 3 coats
on top of my new Interlux 2000 epoxy system last spring. I'll let you know
in a year or two how recoating works!
Stefan Mochnacki
Grampian 30 "Somewhere"
--
Stefan W. Mochnacki INTERNET - ste...@centaur.astro.utoronto.ca
Astronomy, U. of Toronto UUCP - {uunet,pyramid}!utai!helios.physics!stefan
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John F. Hughes
:An interesting twist in more recent literature is that if you have
:good gelcoat on the bottom, it is a good idea to put on a couple of coats
:of conventional marine enamel before the anti-fouling. Supposed to keep
:the osmosis nasties away better than epoxy ... but this "scientific"
:result hasn't percolated to many boatyards yet, I suspect.
Can you give us some references on this, Stefan? My understanding was
that most conventional marine enamels aren't meant for below-the-waterline
use, and with the wash-away bottom paints (e.g., CSC) you'd eventually
have them sitting touching the water, no?
-John
tkla...@cc.curtin.edu.au
> In article <1994Jan10...@cc.curtin.edu.au>, tkla...@cc.curtin.edu.au writes:
> |> In article <ITCMtAc...@dolfin.UUCP>, ano...@dolfin.UUCP (Adam M. Noble) writes:
> |> > Has anyone ever tried stripping bottom paint from a fiberglass
> |> > hull with an electric heat gun? Please list any disadvantages or
> |> > advantages as to time required and effect on the glass. Also
> |> > define type or kind of heat-gun used.
> |>
> |> yes, I have done this with an ordinary Black and Decker heat gun, and it
> |> works OK provided you use a bit of caution.
>
> [ ... gruesome stuff deleted ....]
>
> All the books I've read say "NO WAY! Heat guns and GRP don't mix!".
> (e.g. "This Old Boat"). I've never seen anybody do it.
> Perhaps somebody more experienced can knock this one on the head
> for good ... but to me heat-stripping and plastic seems all wrong.
> I would think that serious damage is likely: gelcoat softening,
> severe stresses, delamination, etc. OK for metal and wood (with care),
> NOT for plastic!
I agree that you are going to do serious damage if you apply lots of heat
or very high temperatures, so perhaps I should have stressed the 'caution'
part more in my original posting. As a guide to how much heat to use, a
yacht deck sitting in the sun here in W. Australia can get too hot to walk
on, and that doesn't cause any damage. Clearly you need more heat than that to
get the paint off, but only locally over a shallow layer. you don't go at it
like you were using a blow torch! The gel coat will definitiely soften if you
get carried away, and so I would only use this method if coating with epoxy.
I have done two boats this way, one 6 years ago, the other 4 years ago, and
both are still loking fine. They had very thick gel coats, maybe this made a
difference.
>
> Standard methods, in order of preference (??), are:
>
> (1) Scraping with a hooked blade.
> (2) Chemical remover (see thread of past few days). Interlux
> make a stripper; make sure it's the right one (for GRP).
> (3) Sanding (80 grit or finer ALO; hand, finishing or orbital sander).
> (4) Sandblasting (NOT recommended unless you are applying
> an epoxy barrier system; erodes and damages the gelcoat).
*
Yes, I have tried these too. No. 1 is good on soft paints if you have strong
muscles
I have found 2 to be hopelessly slow and messy, it seems to strip the paint
one layer at a time no matter how much stripper you put on for how long. Then
when you decide to give up and use method 3, you have a viscous goo on the
surface that won't sand.
3 is OK except for poisonous dust, and only reasonable fast if you use a
disc sander; you have to be VERY careful with a disc sander, or you can do
serious damage by gouging through the gel coat and into the laminate.
4 is very messy, I have used slurry blasting as a cleaner alternative. It
certainly gets rid of the gel coat and blasts open any voids in the laminate,
but you would want to know about these anyway so you can repair them. Again,
the boat I did this on 12 years ago is still doing fine.
Has anyone had experience of doing damage with a heat gun? If so, what sort
of damage and under what circumstances?
Whichever method you use, it takes three times longer than you plan (doesn't
everything!)
Stefan Mochnacki
I have copies of two reports:
"The Causes of Boat Hull Blisters", by Thomas J. Rocket and Vincent Rose.
(ABBRA Report, completed under USCG Grant #1501.83)
"The Prevention and Repair of Gel Coat Blisters", Thomas J. Rockett,
Vincent Rose and Andra Kirsteins (ABBRA report, 1988)
(USCG Grant # 1601.82)
[ABBRA= American Boat Builders and Repairers Association, Inc.
715 Boylston Street,
Boston, MA]
The authors are with the Dept. of Chemical Engineering, University of
Rhode Island, Kingston, Rhode Island. The second report says in its
introduction: "The detailed description and results of all experiments
conducted are available at Coast Guard Headquarters, Washington, D.C.".
These reports are extensively quoted in "This Old Boat"by Don Casey.
I think they get referred to by Vaitses in one of his books, but I don't
remember.
The paint conclusion is a funny one. The second report certainly
indicates that marine paint does blister underwater, but it is alleged
to inhibit blistering of the gelcoat anyway.
I painted on an enamel waterline strip, using Sila-Lux (not optimum),
over epoxy, and the paint has blistered a bit over the summer (of
course, that has nothing to do with the above. Just illustrates the
blistering of immersed enamel. In fact, a small overlap of Micron
CSC bottom paint over the waterline strip suggests that the enamel
will wrinkle and peel away under the antifouling paint. Yeccch.).