How to replace the gelcoat of a glider
Alfonso Gonzalez
coat, repainting , and
getting a good finish and low surface waviness.
What techniques are recommended to strip the gel coat, size of the block
used to hand sanding out the glider,types of sandpaper, order of
application etc..? I would like to ge several opinions from people with
experience in this matter.
I am going to do the work on a certified repair shop, the guys in charge
there are quite competent, they will
check my work and perform those task that require a better knowledge of
the art than I posses myself. The burdensome work of stripping out the
old gel coat and polishing the new one will be done by myself. Any
suggestions of how to do the work correctly and efficiently will be very
much welcome.
Thanks in advance.
Nolaminar
try http://www.serve.com/BSA/ASW20B.HTM
Regards, Robert Gaines, USA
jim...@ev1.net
LS right now. I've had experience with painting commercial air-
liners but none with sail planes. First of all you talk about
repair/ refinish gel-coat then about repainting. Let's talk
about gelcoat: The usual procedure is by hand. using a piece
of 1x3 aluminum bar the length of a standard piece of sand paper
held on with contact cement. The process is wet sanding with
dribbles of water. I have been told to start at the leading
edge and rub at a diagonal angle to the wing chord. A common
problem is uneven sanding which creates highs and lows. This
can be prevented two ways; first by spraying a light dye on
the entire surface to show where you've sanded. Second way is
templates can be created (usually a set of 4-5) which fit the
wing at various places from inboard to outboard. If low spots
exist, a paste of gelcoat and macroballoons can be created to
take care of this. Once it is set ,it will have to be cured with
poly vynil alcohol or some other curing agent. Usually, I hear
start with 320 Grit-> 640 Grit -> 1000 Grit then polish. I've
seen guys in Marfa, TX use polish with silicone right out of
Home Depot.. to Tim Mara's exotic polish. The most important
control surface is the rudder. It must be equally sanded and/
or refinished on both sides. Because of the checker board finish
on my tail, I'll probably strip and sent out for custom paint. I
will, however weigh the rudder prior to and after. It shouldn't
make a difference in small planes but I'm still going to check.
Sanding and repainting a glider is a different story... I plan to
build a 10'wide x40' long x 8'high clean room with two exhaust
fans ,4 florescent light strips and two quartz halogen lights.
The frame will be 2x4s covered with 6 mil plastic. The bottom
section will have doubled over plastic screen material for air
circ. It'll cost about $600 but will garuntee contamination
control and environmental control. (Optimum spray environ is
70 degrees F and 50% humidity) I live in Houston, hence the halogens to burn off the moisture. The most popular paints are
Prestec or Dupont Imron. I have total paint/activators/cleaners
sealant etc. retail costs. I will go through the process using
Dupont products: A/C paint such as Imron will not bond with
Gelcoat; paint must be either chemically or mechanically bonded.
Clean out all cuts,digs,cracks, build up with gelcoat and macro
ballons (looks like baking soda!) Photograph and remove all
pressure senstive decals. Profile wings per templates and cure
with curing agent,
Apply die to wings and fuselage and wet sand thru to new surface,
using 320 Grit sand paper. This will give you a smooth but deeply
scratched surface. Dupont recommends 220 grit.
with sanding complete, clean all surfaces with water borne
cleaner, Dupont 3949 cleaner. Ensure clean room dust free.
Vigorously shake and stir Dupont Corlar expoxy sealant; add
activator and then reduce by 20% with Dupont lacquer thinner
3602. lightened sealant will more readily fill scratches
and create a bondable surface. Everything has to be strained
prior to loading into paint gun. adjust pressure and pattern
on sample piece prior to the real thing. Spray one coat, do not
sand! Color will be gray.
After drying, all surfaces should be examined for non-conforming
his/lows or runs. sand and retouch.
Mix 3/4 gallon Imron with 1/4 gallon activator. strain/load/test.
Break areas into manageable time and spray cup capacities. I
anticipate 3-5 passes and 2-3 coats. Allow coats to dry between
spraying. Remember, drying time is a direct variable of temp
and humidity. Just a start... I'm sure others more experienced
can agree/negate. I have a Slingsby factory fibreglas repair
manual if of value.
Jim Jette L3
>
David Kinsell
<jim...@ev1.net> wrote in message > >
>Alfonso, I'm in the process of looking at the refinishing of my
> LS right now. I've had experience with painting commercial air-
> liners but none with sail planes. First of all you talk about
> repair/ refinish gel-coat then about repainting. Let's talk
> about gelcoat: The usual procedure is by hand. using a piece
> of 1x3 aluminum bar the length of a standard piece of sand paper
> held on with contact cement. The process is wet sanding with
> dribbles of water. I have been told to start at the leading
> edge and rub at a diagonal angle to the wing chord. A common
> problem is uneven sanding which creates highs and lows. This
> can be prevented two ways; first by spraying a light dye on
> the entire surface to show where you've sanded. Second way is
> templates can be created (usually a set of 4-5) which fit the
> wing at various places from inboard to outboard. If low spots
> exist, a paste of gelcoat and macroballoons can be created to
> take care of this.
I've had a professional refinisher tell me that microballoons are
a safety hazard since they tend to explode in the lungs if inhaled.
He suggests a silica colloidal filler to thicken gelcoat. I've used
it for nicks, and it seems to work well.
>Once it is set ,it will have to be cured with
> poly vynil alcohol or some other curing agent. Usually, I hear
> start with 320 Grit-> 640 Grit -> 1000 Grit then polish. I've
> seen guys in Marfa, TX use polish with silicone right out of
> Home Depot.. to Tim Mara's exotic polish.
Silicone, either by itself or in a wax is generally not recommended,
since repairs in the future are difficult to make due to poor adhesion
to the surface.
Dave Kinsell
delete an x from address for email reply
Sula
>Silicone, either by itself or in a wax is generally not recommended,
>since repairs in the future are difficult to make due to poor adhesion
>to the surface.
This "old wives tale" is not much regarded by those who repair gliders.
They tend to make few assumptions about how the plane may have been waxed,
and simply take off enough old gelcoat to ensure that the new stuff will
adhere.
David Kinsell
Sula <su...@shn.org> wrote in message
news:SZ7S3.15849$Qo3.2...@wbnws01.ne.mediaone.net...
Funny thing about removing material is that you have to stop somewhere.
Spray on some new material and you feather it across the transition.
Some of that eventually flakes off and leaves jagged little edges if it
doesn't adhere. Not much a repair person can do about it one way or
another, that's just what you get if you're so cheap you use car wax on
a $12,000 gelcoat job. You also don't get much UV protection, but that's
only an issue if you worry about what your glider is going to look like a
few years down the road.
Mike Lindsay
<su...@shn.org> writes
>David Kinsell wrote:
>>Silicone, either by itself or in a wax is generally not recommended,
>>since repairs in the future are difficult to make due to poor adhesion
>>to the surface.
>
>
>This "old wives tale" is not much regarded by those who repair gliders.
>They tend to make few assumptions about how the plane may have been waxed,
>and simply take off enough old gelcoat to ensure that the new stuff will
>adhere.
>
>
>
that he was making fibreglass fishing boats.
--
Mike Lindsay
Gapagod
>and the amount and stickiness are easily controlled.
From my years in RC airplanes, I use 3M Spray 77 adhesive. The trick for
getting the paper off is to put the bar in the oven at 200-250 F for about 10
minutes. If you use a light coat of glue to begin with, you may not even have
to clean off the residue with acetone. However, all my bars are aluminum.
Wood is a different ball game. Though I expect the low temperatures are more
like a sauna as far as the wood is concerned. You work up a sweat, and so does
the wood!
Jim Husain
soon to be SZD 48-3 owner
gap...@aol.com
Gapagod
>stronger than the kind I've used. But I use just enough adhesive to keep
So....what kind do you use? I would benefit from a lower gas bill.