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neonbutterfly 01-04-2004 06:59 PM

balsa/fiberglass filler??
Hi!! need a good lightweight filler for balsa wood and also for light fiberglass glass cloth. once the fuselage has been glassed i would like to fill in the weave of the cloth prior to painting. any ideas???



Edwin 01-04-2004 07:14 PM

RE: balsa/fiberglass filler??
I use light weight spackling from the hardware store. I thin it a lot with water and rub it on the wing with my fingers until I'm satisfied its all in the weave, wipe off the excess. When dry, I sand it off down to the weave. Gives a nice smooth surface that paint sticks to like snot on your finger. Cheap.

wrongwaywayne 01-04-2004 07:24 PM

RE: balsa/fiberglass filler??
Edwin, how does that stuff stand up to flexing? Isn't it kinda brittle?

phread59 01-04-2004 10:50 PM

RE: balsa/fiberglass filler??
I would suggest nitrostan. It is also called spot putty. You can get it at automotive stores. I believe most NAPA stores sell it. I use it as a balsa filler all the time. It is lightweight and dries very quickly. I do not know how it will work filling weave. I have never glassed before. So here you are on your own.

Mark Shuman

BobH 01-05-2004 12:41 AM

RE: balsa/fiberglass filler??
neonbutterfly. I have tried using both thinned spackel and light weight balsa fillers to fill the weave in the cloth. I can't really say if I saved much if any more weight than if I had applied another coat of resin or epoxy. I have switched to using a roller to apply the epoxy which works the best I have ever tried. Each coat is very smooth and even. After your second coat you can apply the primer. Your weave should be sufficiently filled by then. For filling low spots in glass use evercoat. Its available from automotive paint stores. It sets up very fast and can be sanded to a super feather edge. BobH.

Edwin 01-05-2004 08:02 AM

RE: balsa/fiberglass filler??
Havent had any trouble with cracking yet. Been doing it years. I usually put on one coat of epoxy, then the spackling. I prefer the matt finish it gives me for warbird finishes. Later, on a civil avaition plane, I'll use the same process but put a second coat of epoxy on over the spackling. Remember, you sand off the spackling down to the weave which should remove 99.9% of it so there shouldnt be any big build up for cracking. Even shallow filled divits on a non-flexing surface hold up pretty well, within reason. Bob is probably right also about the weight savings. I've been hearing about evercoat for a while now, need to try it.

BobH 01-05-2004 11:51 AM

RE: balsa/fiberglass filler??
Edwin, once you try Evercoat you won't use anything else to fill. Its great for doing a glass fuse and filling the seams. As well as a lot of other applications. BobH.

Edwin 01-05-2004 08:54 PM

RE: balsa/fiberglass filler??
Well Bob, it looks like I might try it tomarrow. Im in the rough sanding phase of making a glass cowl for a highly modified Bandito Grande. (Using the lost foam method for a one up copy, glassing on the outside of the styro plug. Not a perfectly smooth finish but good enough for an everyday flyer) The cowl looks sorta like a P-51 cowl, it will fit a ryobi 31. Im willing to try any new method so instead of spackling Im gonna use the evercoat. Will let ya'll know in a couple of days.

B Vial 01-05-2004 09:07 PM

RE: balsa/fiberglass filler??
To fill the weave of fabric and pin holes in fuses I dip a paint brush into some good SANDABLE primer (not that white lustercoat primer that says it is but isn't or others like it) then I dip the wet brush into a container filled with micro ballons. Sure does look like heck but once it is dry it adds almost no weight and sands like you wouldn't believe. Learned this from some video dealing with fiberglass and have been using it ever since.

k_sonn 01-12-2004 04:15 PM

RE: balsa/fiberglass filler??
1 Attachment(s)
When glassing, I mix micro ballons in the second coat of epoxy resin and apply with a roller (I use West Marine epoxy resin). Then I scrape off the excess resin. When dry, I sand with 80 grit. The weave is filled, there are no pin holes, and the finish is smooth. I then apply a coat of filler primer and wet sand with 320 grit until I can see the wood. If there are any low spots primer will be left on the structure. I use a light weight body filler called Rage Extreme (by Evercaot) to fill in the low spots or to fair in wing fillets, canopies, etc. If you try this technique, you will get a very light weight finish. I am finishing a Top Flight P-51 ARF with this techinque and it is coming out lighter than my buddies T/F P-51 Arf with monokote on it (I converted my Arf to a "B" model). Here is a picture of what the airframe looked like after doing the above described technique.

pete913 01-13-2004 05:19 AM

RE: balsa/fiberglass filler??
For filling fiberglass weave, epoxy mixed with microballons works well. For balsa filler, I make my own. I buy a quart of the cheapest white interior flat latex paint i can find, then mix talcum powder until it's the consistency of the commercial balsa fillers. It's cheap and works great. very sandable, and you can tint it to a balsa color if you wish. I store it in an empty plastic coffee container and store small amounts in a screw top jar. One batch of this stuff would probably last the average modeler a lifetime.

Tmoth4 01-13-2004 08:17 AM

RE: balsa/fiberglass filler??
For balsa wood Hobbico Hobbylite filler is excellent. It sands better than lightweight spackle.

For filling fiberglassed surfaces I use primer/surfacer from NAPA auto stores. I thin it down and brush it on. Most of it gets sanded off.

An excellent filler for low spots and pinholes on surfaces that have already been glassed is 3M Green Spot Putty, also from NAPA.

The auto primer/surfacer and Green putty are expensive $30-40 each, but there is enough of each for several planes.


wrongwaywayne 01-13-2004 10:19 AM

RE: balsa/fiberglass filler??
I was thinking of covering with supercoverite an iron on fabric and then filling the weave in certain places for that aluminum look. It is for a Chipmunk which was built as a composite covered airframe - aluminum and fabric. Then I would spray paint the whole thing.

What do you think? Any other ideas? I am wanting to keep it light.

Tmoth4 01-13-2004 11:24 AM

RE: balsa/fiberglass filler??
Coverite would work well on the wings but I wouldn't use it on the sheeted fuse. It will eventually bubble up over time. You're better off glassing the fuse.


forfun42us 01-14-2004 12:59 PM

RE: balsa/fiberglass filler??
1 Attachment(s)
I have never tried this but plan too some time in the future. It is called surface veiling and it's used to prevent print through on molds and such. in a mold you would apply it between the Gel coat and the Glass fablic to prevent the weave from showing through the gel coat, so if you apply it as the last layer it might do the same?. You can get it at www.uscomposites.com

If anyone has tried this let me know how it did.

billd3 01-30-2004 08:40 PM

RE: balsa/fiberglass filler??
I have been glassing and painting for 15 years and I'm always experimenting and learning. There are many different techniques (all in the name of "keep-it-light") which have worked for me with varing degrees of success. I've tried everything from polyester resin to water based polyutethane with talc mixed epoxies of many brands thinned with alcohol and or mixed with talc or microballoons...same goes for fillers. Here's the techniques/materials I always come back to...

Fillers: apply BEFORE you glass...model water based fillers are excellent and really do seem to sand better than regular light weight spackle compounds. automotive pin hole filler for pinholes and really small scratches (weight doesn't matter here as you use so very little)...any brand seems to work well...you know the red or green stuff in the tube.

Resin thickeners: Talc has proven much better (smoother) over microballoons for me.

Glass cloth: use .58 oz cloth and make sure you get a weave that is TIGHT. The cloth Dan Parsons use to sell was my personal favorite and when I run out of my stockpile I'll search for another brand...The tight weave is important as it has smaller voids to be filled with resin. When shopping, look for a high thread count with the low weight. I'v seen some so-called light cloth has such an open weave it would take a dump truck of resin to fill it.

Resin and application: I prefer an epoxy finishing resin (low viscosity) such as Z-poxy. West system also makes a laminating resin (System 105) which works very well and appears to be harder (less shrinking over time). I do not thin the resin any more than it is because I found that 3 coats of 50/50 thinned resin did nothing but soak into the wood adding unnecessary weight and requiring a lot of sanding. Apply the resin with an old credit card (or similar) squeegy out ALL the excess resin ( and I do mean ALL). After curing squeegy on a 2nd coat. This will completely fill the weave and requires VERY LITTLE sanding (my least favorite job).

A normal primer coat sanded almost completely off will complete the process. I have also learned that a "ton" of weight can be saved when painting colors like yellow, red, (and believe it or not...some OD colors), by spraying on a light coat of white first.

Keep in mind that practice makes perfect. I have found that I can glass and paint a 33-35% plane and only add a few more ounces over a standard moneycoat finish

wrongwaywayne 01-30-2004 09:25 PM

RE: balsa/fiberglass filler??
I just finished putting a primer coat on a fiberglass cowl. Now all the imperfections show up. What sort of putty should I use before the next finish coats? I hope I dont have to re primer.

Any ideas?

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