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Fiber Glass 101

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Old 10-25-2006, 09:00 AM
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fyredog
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Default Fiber Glass 101

I am going to be fiberglassing on several of my kits, and need good sound advise from all you fiberglassers out there.

1st of all, I will be fabricating from fiberglass, gear doors for my retracts. What I would like to know is what weight the glass cloth recomendations are and what resins to use.

2nd, I may glass the wings and fuselage for painting. What weight glass cloth recomendations are and what resins to use.

3rd, what tricks and what methods of application, including temperature, tools and do's & dont's are there.

Remeber I have not attempted this before.

Thanks in Advance
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Old 10-25-2006, 09:37 AM
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Default RE: Fiber Glass 101


ORIGINAL: fyredog

I am going to be fiberglassing on several of my kits, and need good sound advise from all you fiberglassers out there.

1st of all, I will be fabricating from fiberglass, gear doors for my retracts. What I would like to know is what weight the glass cloth recomendations are and what resins to use.

2nd, I may glass the wings and fuselage for painting. What weight glass cloth recomendations are and what resins to use.

3rd, what tricks and what methods of application, including temperature, tools and do's & dont's are there.

Remeber I have not attempted this before.

Thanks in Advance

1, I would recommend using 3.5 oz glass for gear doors. Once you have the skin over the area of the retracts, draw your outlines and cover it with a piece of transparent Monocote or Ultracoat that is about 1" bigger all around the door and retract hatch. This will work as a parting agent. Lay 3 to 4 layers of fiberglass, with the weave orientation of each layer turned 45 degrees. Once cured, you will be able to trace the outlines onto the fiberglass. Pop it off the covering and cut the pieces out.

2, I would recommend .5 oz to .75 oz cloth for glassing the model. As for resin, there are a number of choices. Most common are, polyester resin, epoxy resin, waterbased polyurethane and finishing laquer. I used West Systems epoxy with their 206 hardener on my last project and am very pleased with the results.

3, Here's what I did on my last project. After filling and sanding the plane, I did a coat of lacquer based sanding sealer and lightly sanded. Lay the glass on the plane, brush it with a soft brush to create a static cling. Brush on the epoxy working with 1 oz batches. Squeegee off as much epoxy as i can with a plastic squeegee. Roll a roll of toilet paper across it to soak up just a bit more epoxy, discarding the outer layer of the roll as i go. Let cure. Fill the weave with coats of primer sanded between coats until smooth, now ready for detailing and paint.

If you use primer to fill the weave, make sure you let the primer fully cure between coats. If you rush your sanding and coats, when you are done, the primer will fully cure, shrink and the weave will show again. Sand each coat just back to the top of the weave and not through it. Work only in small batches of epoxy so it doesn't start to set. Always mix in clean cups and use a clean stir stick and brush. I use those small 2-4 oz plastic cups that the local burrito/taco restaurants use for salsa, wood coffee stir sticks, acid brushes and those fake credit cards that come in the mail make good squeegees.

You might also want to pick up the Black Arts Building and Fiberglassing series from Dave Platt. He covers the use of Polyester resin in this series. Campy, here on RCU, has a good tutorial on the use of polycrylic polyurethane. Tom Pierce has a tutorial on Deft Lacquer on his website.

Scott
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Old 10-25-2006, 11:09 AM
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Default RE: Fiber Glass 101

One bit of advice on working with the lighter glass cloth (.5oz. - 1oz.) - be very careful you don't let anything get hung on it. The fibers pull apart easily and it doesn't take much to ruin your newly cut piece of glass. Also, a method for applying that I have found which works really well is to put down a very light, thinned layer of your epoxy (or whatever you are using with it) and then lay the glass on top of that. Use some latex gloves or something to smooth the glass out with your hands, then add another very thin bit of epoxy or resin. Then sand. And sand. etc.
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Old 10-26-2006, 12:15 AM
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Default RE: Fiber Glass 101

Thanks a million for your advice guys. Very helpful.

The Epoxy, does it give you enough time to groom well before it sets? Most exopies I have worked with, Maybe gives you 10 minutes before the surface gets to hard to groom. what makes epoxy any better or worse from the other agents?

I like the idea of clear monokote after tracing!

But whew! The price of clear Monocote is through the roof! Oh well this wont be my last set of wheel doors!

The sealant I would guess would be sprayed on?

Lots of sanding by hand or block? or both?

I have only used monokote before, so please forgive me.

Thanks
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Old 10-26-2006, 01:00 AM
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Default RE: Fiber Glass 101

If the wing is not too contoured, I suppose you can go the cheap route and just tape down some wax paper. If you go with an iron on, it can be any color as long as it's transparent.

As for working time, I only work in (approx) 1 oz batches. Once the epoxy is on the wing, it sets slower than when it is in the mixing cup. The thinner/smaller the batch, the slower the cure. Get the epoxy brushed onto the wing, then you'll have time for the squeegee and rolling with toilet paper. If the epoxy starts to set in the cup, stop, mix a new batch, then continue. On my TopFlite Spit, I would do one session for the bottom of the wing, 1 for the top, 1 for the vertical and upper horizontals, 1 for the bottom horizontals, 1 for each side of the fuse and 1 for the bottom of the fuse. I spread the work over several evenings.
I've not used method other than epoxy, so I cannot give a comparison. Different people like different methods. The things that I like about epoxy are, most people agree that it gives about the hardest finish. It's fumes are less intense than lacquer. It's a well known process that I found easy to learn and achieve good results. I liked the simplicity of the West Systems metering pumps they sell for their resin and hardners. The hardness of the finish also makes it less likely of accidently sanding through the glass.

The sanding sealer I used was Deft sanding sealer. I applied it with a 1" brush and once cured, lightly sanded with 320 grit.

When sanding the primer, I wet sanded with 320 grit. I picked up a sanding pad at the local auto paint store which is designed for wet sanding. It's a rubber pad with holes in it. This gives lots of cutting edges and makes fast work of the sanding.

Another tip if you use primer for filling the weave. Make sure you let the primer thoroughly dry between sandings. If you sand too soon, once sanded, the primer will finish drying and will slightly shrink which will result in the weave showing through again.

Oh, one other source of information I forgot to mention, if you haven't yet found and visited his site, be sure to check out www.airfieldmodels.com by Paul Johnson (cafeenman). It has tons of how to's, tips, and information.

Hope this helps

Scott
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Old 11-05-2006, 11:57 AM
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Default RE: Fiber Glass 101

What is with the toilet Paper? What purpose does it have?

Thanks Again
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Old 11-05-2006, 12:13 PM
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Default RE: Fiber Glass 101

You roll the toilet paper roll over the fibreglass cloth to soak up the excess resin. You roll the paper in the direction so that the paper sheets do not un roll.
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Old 11-05-2006, 02:56 PM
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Default RE: Fiber Glass 101

You many want to consider glassing with waterbase polyurethane.

The advantages to it are:

About 1/2 the weight of a resin job.
MUCH easier to sand.
No fumes.
Soap and water cleanup.
Materials are noticeabley less expensive.

The disadvantages:

Only about 50%-60% of the hardness of resin
Only has about 60% of the strength of a resin job. (If you need the glassing for strength, I suggest going back and take a good look at the airframe and re-enforce the weak areas).

Here is a "basic" how to for using waterbase poly, however the basics and prep work are pretty much the same for a resin or a poly glassing job. (PS - I use Minwax Polycrylic for my glassing )

Glassing with Water Base Polyurethane


1. Sand the model with 220 grit and remove any highs/lows you may find.
Fill as needed with lightweight filler and sand.

2. Give the wood 1 thin - medium coat of wood sealer. I use the
commercial stuff. What this does is twofold - it stops the balsa
from soaking up too much of the poly and at the same time protects
the balsa from the water in the polyurethane.

3. When dry, sand lightly with 220 to remove the "fuzzies".

4. Some people say to apply a light coat of 3M #77 adhesive to the
wood at this point. I have found that this is more trouble than it
is worth since if you have a wrinkle, the complete piece of fiberglass
has to be removed to straighten it out.

I prefer to lay the fiberglass cloth on the part/area to be covered and
smooth it out using a SOFT brush. Brush FROM THE CENTER TOWARDS THE
EDGES. The static electricity usually holds it in place. I normally
use 1/2 oz (.5 oz) or 3/4 oz (.75 oz) fiberglass cloth.

5. Using WATER BASE polyurethane and a FOAM brush, start at the center
and brush towards the edges of the fiberglass. All you want to do is
stick the fiberglass to the balsa, so excessive amounts are not needed.
Any additional pieces of fiberglass should overlap each other about
1/2 - 3/4 inches.

Let this dry. DO NOT SAND !!

Brush on another coat of polyurethane. This coat can be a little heavier.

Let this coat dry. DO NOT SAND !!


6. Mix up some polyurethane and microballoons. I use 1 part
microballoons to about 5 parts polyurethane. This will be on the thick
side.

Brush on a medium coat of this mixture and let dry.

7. Wet sand this with 220 or 320 grit paper. BE CAREFUL, AS YOU CAN
VERY EASILY SAND RIGHT THROUGH THE FIBERGLASS.

8. Check the fiberglass carefully to insure the weave is filled. If
the weave is not completely filled, repeat step 6 and 7.

9. SPRAY a coat of water base polyurethane on the plane and let dry.
DO NOT SAND !!

10. Spray a THIN coat of primer on the plane. When this is COMPLETELY
dry, block wet sand with 220 or 320 grit as much of the plane as
possible to highlight any highs/lows you may have missed during your
sanding/prep. The areas that can not be block sanded, CAREFULLY sand
by hand. (TIP: CA some of the wife's/girlfriends fingernail file boards
together. Wrap the sandpaper around them so you can block sand in tight
areas. The CA helps prevent the boards from disintergrating in the water)
Fill any low areas with a lightweight filler and sand when dry.

Apply a THIN coat of polyurethane to these areas.

When the poly is dry, repeat this step until you are satisfied that all
the highs/lows are removed.

11. SPRAY a thin coat of polyurethane on the plane. When dry, spray
the primer.

12. When the primer is dry, you can apply your rivets, panel lines and
other detailing desired.

13. Now you can spray your paint.
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