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Here’s an alternative approach to take with ABS plastic cowlings and wheel pants.
I know many people like to get the fiberglass replacements for the ABS parts in many kits, but for those of us on a budget, this is an easy and inexpensive way to make the most out of what comes in the kit. I’ve had good results with this method on several planes. My cowls and pants look good, and as long as they’re not handled too severely, they last a good long time, also.
The first step is to trim the edges of the pieces that will be glued together as carefully as possible. If you’ve ever built a plastic display model kit using liquid cement, the assembly is a piece-of-cake. Use dope thinner as a liquid cement to glue the pieces together. You can hold, clamp, or tape the pieces together dry, then using a fine paint brush or applicator, run some thinner into the seam. The thinner actually dissolves a bit of the plastic and causes the pieces to “Weld” together.
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Allow the assemblies to dry overnight, or at least for a couple of hours. Drying time depends on how much thinner you got into the seams. For the next step, the assembly doesn’t have to be rock solid, but you don’t want things falling apart as you work with them.
While waiting for the parts to dry, you can begin to make the filler cement. Cut some of the scrap plastic from the moldings into little bits, and place them into an old baby food (or equivalent) jar. It’s important that your jar has a lid that fits well. After you have an eighth to a quarter inch deep of plastic bits covering the bottom of your jar, pour just enough dope thinner into the jar to wet all of the bits. Cover the jar and wait an hour or two.
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When you come back to the jar, you should find the bits all dissolved and you now have a creamy paste which can be used to fill the seams and any other imperfections in the parts. It can also be used as a cement to glue reinforcements into the parts, such as a ring inside the front of the cowl around the hole you cut for the prop shaft. I smoothed my filler into the seams with a palette knife. A flat blade screwdriver would also work well, or even a small flat piece of wood. I filled the inside of the seam on my cowl to add extra strength, also. The goo will come off of your tool pretty easily with a paper towel while it’s still wet, or it will peel off when it’s dry, but it welds itself to the plastic parts... it actually becomes “One” with them.
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This filler will shrink slightly when it dries, so don’t be afraid to leave it a little thick. You can also keep the stuff in the covered jar for a while, so if you need to add more filler later, that is not a problem.
After drying for at least a day, the filler will be the same color and consistency as the original plastic part, and the seams can be carved, sanded and shaped just as easily as the plastic parts (which isn’t saying much, granted). Be careful sanding, or you’ll just melt the plastic and make a mess. I use very coarse (60 grit) sanding blocks to begin the shaping, and progress to finer grades as I go along.
Eventually the parts will be ready for primer and paint.
Very nice phlip, thats an GP RV cowl hehe, got that on too
Apalsson, I find it necesarry to reinforce the cowl because otherwise it will crack rapidly. The most important thing is to roughen the inside with p.e. 60-80 gritt paper. Otherwise the epoxy wont stick to the abs. I have always used epoxy but you can do it with polyester too.
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I have to say, that is very ingenious, to use the left over plastic to make a filler/cement. Never would've thought of that.
I always just tack the two halves together with thin CA, then run a thin strip of 2oz glass/epoxy inside along the seam. Then I fill the whole inside with a layer of 0.75oz glass/epoxy to stiffen and strengthen up the whole thing. if the epoxy is used very sparingly, this method adds very little weight and the glass provides a little heat insulation from the engine that it otherwise would not have.
I then use just a smidgen of Bondo on the outside of the seam and sand perfectly smooth. Then, prime and paint. Seems to work pretty good for me.
Patriot
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quote:
Do you reinforce your ABS cowls by fiberglassing the inside? If so, any tips?
I've never reinforced before, but frankly, this GP RV-4 cowl is thinner than the other stuff I've done before... all Sig kits, I think. I'm considering it this time. Haven't decided yet.
You don't see it in my photos, but I did reinforce around the prop shaft opening by cutting a circle out of a flat piece of scrap and cementing it to the inside of the cowl, so now it is double thickness around the hole.
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Joined: 9/14/2003 From: Ft Wayne,
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I tried this,,, On a pod for a Seamaster 40-
and it works GREAT!! it takes awhile to set completely on the thicker parts, but sanding is easy, you can control the 'thickness' by letting it stand or adding more acetone. I used "layers" to build up the gap formed by the seam and you can't tell where it joined!!
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Joined: 5/20/2003 From: Houston,
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I agree that ABS parts need reinforcing. I use glass cloth on the inside with Oatey's All Purpose Cement as the adhesive. No need to roughen the inside surfaces to get the glass cloth to adhere. Easy to do and tough as fiberglass parts. PVC cement will also work.
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I usually use 2 oz cloth, cut into strips, and thin CA. I apply a strip over the seam on the inside and any areas that need reenforcing, such as where the mounting screws go. Works very well and bonds well to the ABS also.
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I reinforced some ABS part inside with a light layer of glass sucked with acetone. It made the glass sink into the ABS. That method worked quite good. Instead of actone I also used thin CA.
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quote:
ORIGINAL: p51flier
I reinforced some ABS part inside with a light layer of glass sucked with acetone. It made the glass sink into the ABS. That method worked quite good. Instead of actone I also used thin CA.
The only negative I have found to acetone is that if you use too much, it can "melt" through the ABS piece and/or warp it.
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