Gel coat removal - water sanding vs. straight line sanding
LS3 Pilot
have experience in the best way to remove gelcoat? I've got an area
thats too big to hand sand on the wing that needs some work. A friend
suggested I buy a water sander that continuously feeds water to the
sander (similar to a pneumatic powered straight line sander).
What's the best tools to safely and effectively removing the old gel?
uncl...@ix.netcom.com
Hand sanding with 100 grit.
You didn't want to hear that.
UH
JJ Sinclair
The last one I did using an 8" grinder turning 1800 rpm with a 40 grit
sanding disc! Be careful to stop just short of hitting any glass, then
finish up with 60 Grit and a small 6"hand disk grinder.
Does that answer your question?
:>) JJ
LS3 Pilot
http://www.google.com/products/catalog?q=wet+sander&hl=en&show=dd&cid=2539261311016448822&sa=title#p
Steve Leonard
Sand dry. Use a vacuum of some sort if you want to try and keep dust
in the area to a minimum. Didn't want to hear that either, did you?
Steve
Craig
One of more than a few reasons I don't do it for a living anymore.
Craig
uncl...@ix.netcom.com
I gave you the smart ass answer first. We use 5 inch Porter Cable
orbital with soft pad and Mirka 80 grit discs.
We put in a dust collection system because it's pretty darned messy.
Start slow and take your time. Impatience leads to lots more work.
Good luck
Uh
bildan
There's a thing called an "air file" auto body shops use.
http://www.pivco.net/index.php?main_page=product_info&products_id=1710&cPath=238#googlebase
It's a linear oscillating compressed air driven sander about 18" long
and 2.25" inches wide. I've been told they work pretty well with 80
grit and they have less chance of digging into the fiberglass than a
rotary grinder. Since it's air driven, I suppose you could safely use
wet sanding and avoid the dust.
Bob Kuykendall
> What's the best tools to safely and effectively removing the old gel?
Sawzall
T8
> What's the best tools to safely and effectively removing the old gel?
Junior club members.
uncl...@ix.netcom.com
> On Feb 6, 10:54 am, LS3 Pilot <ls3pi...@gmail.com> wrote:
>
> > Trying to do some work on my ship. Does anyone that reads this forum
> > have experience in the best way to remove gelcoat? I've got an area
> > thats too big to hand sand on the wing that needs some work. A friend
> > suggested I buy a water sander that continuously feeds water to the
> > sander (similar to a pneumatic powered straight line sander).
>
> > What's the best tools to safely and effectively removing the old gel?
>
> There's a thing called an "air file" auto body shops use.
>
>
> It's a linear oscillating compressed air driven sander about 18" long
> and 2.25" inches wide. I've been told they work pretty well with 80
> grit and they have less chance of digging into the fiberglass than a
> rotary grinder. Since it's air driven, I suppose you could safely use
> wet sanding and avoid the dust.
I have used the following in order to find the "best"(for us) tools
fo gelcoat removal.
3 inch air rotary disc sander.- Too small- blows dust all over- noisy
7 inch electric disc sander. Too harsh for us and not easy to control.
Quick but likely to do damage easily.
18 inch air powered linear sander. Noisy. Not good except single
contour. Blows dust around. Need big compressor.
4 inch belt sander. Fast. tricky to use.
4 inch grinder with disc sanding attachment. Fast, fairly easy to
control. inexpensive. Slings dust everywhere.
5 inch electric orbital sander. Very uniform controllable removal.
Lowest dust generation in room. Easiest to use by unskilled or
learning helpers.
Only ones we use now are last 2 with last one doing 90% of the work.
Feel free to relearn the lessons already learned- we all seem tempted
to find the better way that nobody has found. Understand from the get-
go, there is no easy way to do this job.
Have "fun".
UH
JJ Sinclair
>
> - Show quoted text -
Right on Uncle Hank, I use the Porter-Cable orbital sander with DA and
variable speed turning a soft pad with 6" sticky back sandpaper, 60
grit gets through the hard outer surface better (quicker) than 80
grit. I use the 18" air board, but it pulls my 11 cu/ft/min compressor
down in about 5 minutes.
I wouldn't worry too much about the dust, an MD told me the particles
from fiberglass and gelcoat are quite large and not the size that gets
trapped in your lungs. Use a good quality dust mask with inhalation/
exholation valve.
Grrrrrrrrrrrrrrrrrrrrrrrr, glad I'm not doing any of that any more!
JJ
bildan
It's still early and I'm working on my first cup of coffee but...
Might it be possible to make a support block that would limit the
"exposure" of the cutting surface on more aggressive sanders so as to
prevent it digging in? It would work sort of like a block plane.
The idea is to use a fast cutting tool but limited to a very shallow
cut.
uncl...@ix.netcom.com
>
> - Show quoted text -
Might work if the surface we are sanding is straight and uniform over
significant distance.
And the surface we are sanding to is straight and uniform.
And the abrasive medium doesn't wear.
None of these occurs on the projects I work on.
Finding the "easy" way that all the folks that have done this before
is seriously tempting. By the time you develop and test the tool, you
can learn how to use the proven tools pretty effectively.
Well known shop scenario- voice is the worker:
This whizbang (grinder, sander insert tool here) really does much
better than the hard way I keep reading about.
Goin' pretty good- this isn't so tough.
One more pass and it'll be just right.
Damn!
RAS- How do I fix a hole in my(substitute part) skin?
Another thread!
Been there- done that.
You can't buy experience, but you DO pay for it.
FWIW
UH
bildan
Yep, I'm sure it takes a lot of experience.
Another thought struck me. Are you familiar with "rivet shavers" that
cut countersunk rivets flush with an aluminum skin?
They have a sharp rotary cutter inside a micrometer adjustable housing
that lets the user adjust the depth of the cut to produce a perfectly
smooth rivet 'shave'. Maybe something like that....
I expect the idea would be to quickly and accurately remove all but a
few thousandths of gelcoat which would then be removed with the 5"
orbital sander.
Tim Taylor
I think this is what you are talking about Bill:
http://www.gelplane.co.uk/gelplane/product.asp
I have thought about both the plane as well as testing bead/sand
blasting. Never got around to having the time to test both. Used the
7" rotary sanding technique like everyone else.
The old Sailplane Racing Association web pages were great information
on refinishing. Not sure if that information was moved to a new site.
Tim Taylor
JJ Sinclair
>
> - Show quoted text -
The Gel-plane looks interesting, but the photo shows gelcoat being
removed from a boat that has mat structure (chopped fibers & resin)
and it doesn't matter much if you cut the top off the fibers. In a
sailplane the structure is cloth and it matters a whole bunch if you
even nick a few fibers. The real problem is the depth of the gelcoat
isn't uniform. Remember how it is built, gelcoat is sprayed into a
prepared mold and experience has shown that extra gelcoat is needed at
all edges and openings, spoilers, etc. Now start grinding it off and
you soon see that you must stop here, but keep going deeper over
there. I have tried sand-blasting (went right through in a heartbeat)
and paint remover ( just turned everything brown). Alas, I have found
nothing to beat good the old orbital sander. One can train high school
kids to do it, but they soon move on to more interesting work. We are
taliking about a mind-knumbing boring, filthy dirty, noisy, nasty,
activity that nobody is his right mind would do for a few worthless
dollars. Speaking of the worthless dollar, this is a good time to buy
a sailplane.................its got to be worth more worthless dollars
in the future because our national debt will keep eroding the value of
our already worthless dollar. Does everybody realize that every US
taxpayer owes $140,000.00 as his/her part of out national debt? OK,
enough of that..................Go out and buy a sailplane today, it
will never cost less than it does today.
JJ Who can make you a good deal on a fine little 2-place ship that
was owned by a little old lady who only flew it on Sundays, but she
accidently flew it into a tree..........not to worry, it has been
expertly repaired and refinished by a master abrasives technician.
toad
Checkbook ! :-)
bildan
The thing is, there's a bunch of nice airworthy old gliders out there
with bad gelcoat. Right now, replacing gelcoat costs more than
they're worth. If an economical way could be found to redo the
gelcoat, that would be a good thing, wouldn't it?
uncl...@ix.netcom.com
>
> - Show quoted text -
The economical way is owner with more time than money guided by a
knowledgable helper who has done it before.
A couple guys have done that in our shop.
UH
jsbrake
> knowledgable helper who has done it before.
> A couple guys have done that in our shop.
> UH
Forgive the obtuseness, but how long does it take to strip the gelcoat
off, say a 15 m wing?
I guess that would be the easy part, because then one needs to build
it back up and check the profile, yes? How long for that?
I'm probably not going to like the answer... I'm very glad that the
gelcoat on my mistress is in great shape.
Morgans
"jsbrake" <cff...@gmail.com> wrote
> I'm probably not going to like the answer... I'm very glad that the
> gelcoat on my mistress is in great shape.
I can't imagine a reason to remove all of the gelcoat off of anything. In
refinishing, you get down as deep as needed in problem areas and then build
it back up, scuff up the rest, and shoot a new thin even coat on the whole
thing, and be done with it. Thin is the key; don't put on more than you
took off.
--
Jim in NC
mike
> "jsbrake" <cffk...@gmail.com> wrote
I have seen several examples where someone attempted to remove only
the "bad gelcoat" layer. In a year or two it looked terrible!
Morgans
"mike" <pca...@gmail.com> wrote
> I have seen several examples where someone attempted to remove only
> the "bad gelcoat" layer. In a year or two it looked terrible!
Oh, yes, the devil is in the details, isn't it.
There are degrees of bad. If the bad is cosmetic, i.e., scratches and
oxidation, a removal of the surface and reapplication of a compatible (ah,
more details that can be the devil) new layer will look fine.
If there is degradation of the jelcoat to fiberglass/carbon fiber/Kevlar
bonding, then the detail is the devil. Nothing to do but to take it all
off.
This is a case where working with someone that can teach the ins and outs of
fiberglass work can be invaluable, or valuable enough to save many man-hours
and material bucks.
--
Jim in NC
mike
> "mike" <pcar...@gmail.com> wrote
>
> > I have seen several examples where someone attempted to remove only
> > the "bad gelcoat" layer. In a year or two it looked terrible!
>
> Oh, yes, the devil is in the details, isn't it.
>
> There are degrees of bad. If the bad is cosmetic, i.e., scratches and
> oxidation, a removal of the surface and reapplication of a compatible (ah,
> more details that can be the devil) new layer will look fine.
>
>
> fiberglass work can be invaluable, or valuable enough to save many man-hours
> and material bucks.
> --
> Jim in NC
You mentioned, " I can't imagine a reason to remove all of the gelcoat
off of anything."
and then in a following post,
" If there is degradation of the gelcoat to fiberglass/carbon fiber/
Kevlar
bonding, then the detail is the devil. Nothing to do but to take it
all
off."
I was addressing your first dictum.
Mike
Morgans
"mike" <pca...@gmail.com> wrote
You mentioned, " I can't imagine a reason to remove all of the gelcoat
off of anything."
and then in a following post,
" If there is degradation of the gelcoat to fiberglass/carbon fiber/
Kevlar
bonding, then the detail is the devil. Nothing to do but to take it
all
off."
I was addressing your first dictum.
You got me on that one.
OK, how about, I can't imagine removing all of the jelcoat unless it was
already trying to remove itself. <g>
--
Jim in NC
shkdriver
Hello,
Having refinished only a shk which is primarily wood construction with
fiberglass cockpit and leading edges, IMHO if you decide to purchase a
pneumatic (air) driven sander, dual action orbital or "air file" there
is a world of difference between quality tools and Harbor freight cheap
imports.
I recomend Hutchins brand tools, powerful, smooth action, and easy on
air demand. also you can use a water flood with air tools.
For heavens sake wear a high quality air mask, that previous comment of
not needing one because the particles are too big is B.S. and
dangerous!
As an ICU RN I work with pulmonologists every day and ran that one by
them, one simply stated "I wouldn't breath that with your lungs"
As far as time required, I removed three complete top coats of paint
(about 75 lbs worth) and primers and fillers. brought up the new
coatings and used polyurethane top coat, 18 meter wings, 4 foot wing
root, big constant taper fuse, about 1100 hours.
B.T.W. prestec products ROCK!
Good luck and best
wishes!
Scott W.
--
shkdriver
jsbrake
> (about 75 lbs worth) and primers and fillers. brought up the new
> coatings and used polyurethane top coat, 18 meter wings, 4 foot wing
> root, big constant taper fuse, about 1100 hours.
> B.T.W. prestec products ROCK!
> Good luck and best
> wishes!
> Scott W.
>
1100 hrs... divide by 20 hours/week = 55 weeks , just over a year of
working in the shop after the full-time job.
YIKES! I'm really, really glad I've got good ol' Scwabbelack
(spelling?) on my Kestrel... original 1972 gelcoat in great shape.
uncl...@ix.netcom.com
650 man hrs for club members to refinish ASK-21. Gelcoat off, fill,
contour, respray in acrylic urethane.
About 1/2 that for ASW-19 in gelcoat.
Good news is no need to go to gym for upper body exercise. My doctor
says that, for a fat guy, I have pretty good arms and shoulders.
LOL
UH
Morgans
"shkdriver" <shkdrive...@aviationbanter.com> wrote
> Hello,
> Having refinished only a shk which is primarily wood construction with
> fiberglass cockpit and leading edges, IMHO if you decide to purchase a
> pneumatic (air) driven sander, dual action orbital or "air file" there
> is a world of difference between quality tools and Harbor freight cheap
> imports.
> I recomend Hutchins brand tools, powerful, smooth action, and easy on
> air demand. also you can use a water flood with air tools.
I can only agree with the comment to buy quality air tools, made by any of a
number of manufacturers. The difference in air consumption between a cheap
one and a better one doing the same amount of work can easily be twice as
much air being consumed by the cheap one. No kidding.
--
Jim in NC
Brad
wrote:
Scott..............Prestec isn't a PU product is it?
I'll be looking at a total paint job of the HP-24 sometime soon. Right
now it is all bare carbon. Can't decide if I want to go with Simtec
products or use a 2-pack PU. a-la PPG concept.
Brad
JJ Sinclair
>
> - Show quoted text -
I recommend PPG Concept (90288 super white) with PCL polyprimer (907
white) for primer. You must be very careful when spraying acrylic
urathane, this stuff can kill you! Get a respirator with hose outside
the spray booth, use plastic gloves, hat and glasses leaving no
exposed skin. You will need about 3 gallons of mixed product which
means 2 gal of paint, 1 gal of catalist and half gal of thinner ($1000
bucks or so). Spray on 4 medium coats or until you get good orange
peal everywhere which is an indication you have enough paint on. Let
it cure out for 24 hours at 70 degrees, then block sand (wet) with 600
followed by 800. I spray on guide coat (spray can) before hitting it
with 600 then use the black powder rubbed on in the area before
hitting it with 800. Then let it cure out for a good 3 more days
before buffing with a wool pad and liquid rubbing compound.
Hope this helps,
JJ
Brad
Hey JJ,
This sounds like what I'll end up doing. I'll probably spray the
Polyprimer myself (this is a polyester right?). Then..........I'll
sand the primer, fill pin holes, repeat as needed, then take it to a
pro to have the top coat/PPG sprayed on.
My backyard tarp shed probably won't work!
Brad
Paul Cordell
> Trying to do some work on my ship. Does anyone that reads this forum
> have experience in the best way to remove gelcoat? I've got an area
> thats too big to hand sand on the wing that needs some work. A friend
> suggested I buy a water sander that continuously feeds water to the
> sander (similar to a pneumatic powered straight line sander).
>
> What's the best tools to safely and effectively removing the old gel?
We are all looking for that magic bullet and easy way to prep the
Glider for refinish. There may be hope on the horizon.
http://nanopatentsandinnovations.blogspot.com/2009/11/us-technology-corps-nanoclay-blast.html
Paul Cordell
And the Product is called MAGIC
JJ Sinclair
Brad, Have a talk with the painter to make sure you're both on the
same page. An auto paint shop will normally give it 2 coats and it
should come out bright and shinny and that might be all you want. In
this case you want to do final sanding with 220 grit. If, on the other
hand, you wish to wet sand it as in my earlier post, you need 4 coats
with orange-peal. The painter will think your nuts, just tell him you
need lots of paint so's you can sand one coat off and have it
perfectly smooth, which his car paint job isn't. For a 4 coat job,
the final sanding can be done with 80 grit on a long board followed by
a pass with 150 (hand sanded) to knock down the high scratch marks.
This gives your paint good 'tooth' and you shouldn't be pulling any
paint when removing wing tape. The 80 grit scratch marks will
disappear after the second coat of paint is applied. Many auto paint
shops aren't ready to do a 25' wing and will probably end up with lots
of over-spray...........not a problem if your going to wet sand later.
I think 4 coat then wet sanded and buffed is the way to go. Williams
Soaring has a paint booth and Rex can deliver whatever you wish. I saw
an RV-8 he painted with 2 passes and it looked great.
Have fun,
JJ
Papa3
>
> - Show quoted text -
Hey JJ,
Scratching my head a bit on this one. I think what you were driving
at is that the final primer coat is left at 150 grit, followed by the
four coats of top coat. Or did I miss something?
P3
Brad
I think JJ was referring to using 80 grit followed by 150 on the
Polyspray primer, as you said.
A final coat at 80/150 would be ah...........not so good!
Brad
Doug Hoffman
[big snip]
Great tips on painting JJ! You have just answered several questions I
have had for some time. Thanks for sharing your know-how on this
difficult subject.
Regards,
-Doug
JJ Sinclair
There's two schools of thought here guys; Auto painting and sailplane
re-finishing. The auto painter is going to sand his light primer coat
with no less than 220 and probably more like 320, then spray on two
medium coats, then he's done. Its shiny, cure it out and give it to
the customer!
The sailplane re-finisher breaks all the above rules. He primes real
heavy, maybe 4 coats, depending on what he has to fill to end up with
a good block sanded surface. He jumps on this with his 18" sanding
board with 45 left/ 45 right action and hopes it comes out smooooth as
a baby's bottom without going through the primer and show raw glass.
When all is good, I hand sands it with 150 just to remove any rough
edges, but I'm going to spray on 4 coats of paint and then wet sand
it, so I don't need the 220/320 action. In fact I dont want to do that
because my paint won't have killer good adhesion (AKA tooth) and it
will peal paint from the finished product when Mr. Customer peals off
his wing tape. The 80 grit scratches will disappear with the second
coat of paint, but even if they don't, your first pass with 600 wet
will make them go away.
That's what I have done for the better part of 35 years,
JJ
PS; Oh , yeah body putty. If you have little pin-holes showing through
your primer, wipe in medium body putty and hit those areas with 150.
Brad
JJ....................my glider bits came out of the mold with no
primer, paint or anything, just black carbon with probably a million
little pin holes. My plan is the sand the surface of everything with
150 grit, clean all the dust and bits of sanding debris off with air
and.........(insert suggestion here)................then, if I flood
the surface with polyprime, will that fill the pin holes and give me a
good base to work with?
thanks,
Brad
uncl...@ix.netcom.com
It will bridge across many pinholes. You will sand thru bridging- more
pinholes.
My suggestion is light coat of filler. don't sand yet. squeegee in a
coat of filler to fill pinholes. Then sand.
That will get 90% on first try from my experience.
UH
JJ Sinclair
Flooding doesn't get all the little buggers, but a light prime will
expose them all and then do like UH says and wipe in body putty. I
like the blue stuff that has body, the red stuff is a mite thin for
pin-holes. If Bob did a good job on his molds, you won't need too
heavy a prime......maybe around the L/E, T/E, spoilers, etc, but the
rest may get-er-done with one prime coat. Your local auto paint store
has all the sanding boards and sticky back paper roll in 80 grit, etc.
JJ
Bob Kuykendall
> If Bob did a good job on his molds...
You ought to come and see for yourself. We're convening the next
Akaflieg Douglas Flat in early March, Doug and Brad are coming down to
close a set of wings.
Morgans
<uncl...@ix.netcom.com> wrote
It will bridge across many pinholes. You will sand thru bridging- more
pinholes.
My suggestion is light coat of filler. don't sand yet. squeegee in a
coat of filler to fill pinholes. Then sand.
That will get 90% on first try from my experience.
**************************
Good thread. One thing though; you guys really need to take the time to
trim your previous posts, ya-know? ;-)
One thing might be worth trying, (on a small sample area, perhaps) using the
polyprime.
I agree that a spray will bridge most of the pin holes. What I would
suggest is putting it on with a squeegee, then a rough sanding to take off
any ridges left by the squeegee. It works for filling grain pores on red
oak cabinets and sanding sealer, so it just might work for his pin holes.
Then after the rough sanding, hit it with the sprayer, to have an even layer
to block sand on.
--
Jim in NC
Brad
micro balloons, might give that a try to fill the pin
holes............I'll rough up the surface, and squeegee in the
thickened goop.
When I painted the wings on my Russia, I was horrified to see hundreds
of little pin holes appear......seemingly out of nowhere. But, that
was my first experience with composites, sure have learned a bunch
since then!
Brad