tenacious101010

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I have read many posts about glassing but have a very basic question. I have a quart of "Bondo" brand fiberglass resin that I bought at an auto parts store, will this work to glass a plane?
Thanks, Denny

dreadnaut

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If you are glassing over a wood frame it will probably work. Bondo products are, to the best of my knowledge, polyester resins. For laying up composite molded fuselages etc. Epoxy resins, like West System, and MGS are prefered. Among polyester resins, some are called finish resins, or laminating resins. You definatly want to use laminating resin. Also, do not try to use polyester resins if the temperature of your workspace is below 70 degrees F. It will not cure properly.

Spike

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I'm very far from an expert on this but I thought that for fiberglass covering for painting that you wanted a finishing resin. My understanding is that the laminating resins stay tacky.

combatpigg

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Auto parts store and hardware store resin isn't low enough viscosity for good results, unless you are building a RC tank. Buy the good stuff from a specialty supplier. You can cure polyester resin in a hot box made from styrofoam or cardboard and use light bulbs for heat. Finishing [casting] resin is what I use to laminate .6 oz cloth on balsa, it sands better than laminating resin. It is a good idea to apply a thin coat of resin on the bare wood and sand it before doing the laminating of the cloth.

bigtim

My Feedback: (13)

Denny it really depends on how big your plane is,if your glassing a plane then you want to use as little as possable to wet the glass so your not adding too much weight to your model,for glassing models your better off with a model specific product like Z-poxy,or a water based polyurathane,the WB Poly is a easy way to glass needing no catalyst, for hardening/drying as well as low odor.
having done my fair share of fiberglass work its smelly messy stuff that can be trouble to work with,if your not totally in control of the material you can turn your model into a brick in no time.
the Z-poxy and WB has alot of advantages,I prefer the WB and have had much success using it for 15$ you can get a QT of satin Varathane Diamond finish at Home depot,and save yourself the headache.

TFF

It is thick and heavy. The same made for model use is thinned(at manufacture). It was great in the 70's but time has passed it by with better ways.

dreadnaut

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My bad. Spike an combatpigg are correct, and I had a brain fart.

daven

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I use laminating resin for fiberglass all the time as I normally buy it by the gallon. It does not remain tacky, and gives me a great finish. Finishing resin dries with a waxy surface that some feel is easier to sand and give a good finish, but laminating resin works just fine.

tenacious101010

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Thanks to all who have given input to this thread. I have used the "Bondo" brand and other brands of Fiberglass on a wide variety of projects, none of them were especially weight critical, this was my main concern, I know it will harden sufficiently, will sand well and will be strong. I have a giant TBM Avenger I will try it on before I decide whether to use it on my other projects.
Thanks again to all that have shared opinions and experiences, Denny

aa2dd

I have used Bondo resin & light weight glass cloth for lining the inside of the cowl and also wheel pants for extra strength on my Giant Aeromaster

Bruce

Spike

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Dave,

Good to see that you're still around and in the RC scene.

john132

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I am using the bondo type resin on my yellow aircraft f4 wings and so far it is working well. Will post at a later date what the finished product turns out like.

wkevinm

Unless it has changed Bondo is a polyester resin with filler material mixed in. It has a high viscosity and is meant to be used for filling dents and imperfections in automobiles, can be used for creating molded components, it is heavy and not designed as a laminating resin.

Kevin M

tenacious101010

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Kevin, Bondo is a brand name. That company makes several products including body filler and fiberglass resin among other things. "BONDO" is often used to describe many manufacturers polyester body filler.
Denny

jeffk464

I tried using it before and had a problem with the 15 minute set time. I really didn't have time to do what I needed.

TeamSeacats

You can adjust the amount of MEKP you put into the mixture to control the cure time. However, the Bondo brand resins are really low-tech, bottom of the barrel, and the times that I've used them on thin and lightweight laminations, I've had problems with instability in the resin post-cure...i.e., the part warps. I use it frequently in a pinch for minor (people size) boat repair but gave up on it for a modeling or mold making resin.

Higher end laminating polyester resins (the "laminating" usually denotes a much longer cure time) do work well but epoxy is the Cadillac of composites when it comes to consistency, reliable results, and ultimate strength. It also costs more, go figure. I use good quality laminating resins for making molds since I'm not worried about weight or necessarily strength (since I can make it as thick as I need) and have had good success with stability (some have not).

For a chargeable repair on a boat in undependable winter weather conditions, such as the bow on this 20 foot catamaran that I'm currently working on, I strictly use epoxy for the structural repair.

john132

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TeamSeacats

.

bentwings

JMHO you are kidding yourself with the automotive polyester resin. It is just too thick and heavy. It does not sand anywhere near what Z-Poxy or other finishing resins do. You really risk compatibility problems with polyester and epoxys. It can make a real mess. You can add a couple pounds with this finish system easy. It does make a rock hard surface however.

I glassed a Ziroli Corsair with only 3/4 of a Z-Poxy kit and about 1/3 of that was tossed out. The P-51 took 1 kit and again about 1/4 was scrap. The 118" B-25 has only taken 1 kit and just the center section of the wing has not been done. The epoxied parts are ready for primer with almost no sanding. Bondo Lite filler is ok over the Z-poxy but you do have to be sure the Z-poxy is fully hardened.

combatpigg

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Whenever I see the title of this thread it makes me wonder about how well the Bondo fiberglass filler would do for a quick mold. I can see the possibility of dumping a batch of it over a gelcoated plug to make a mold that might only get used once. Is this already being done?

John Sohm

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Man you dump a bunch of it and you had better cut back a bit on the catalyst or you're going to generate some serious heat ! You might damage the plug doing it. This stuff was designed to be put on in thin layers. I still think you'd be better off doing it the recommended way using multiple layers of cloth and chopped mat, etc., etc.

TeamSeacats

yeah, quite a bit of heat that leads to cracking. It's a long story but I was making a composite shell for the back of my gloved hand for wrapping sailing lines to reducing the tendon swelling I was experiencing. I made a soft female mold of my gloved hand and then poured it with polyester resin mixed with some chopped glass. It worked well though it did get extremely hot and probably would have cracked into pieces if I hadn't mixed in fiberglass strands.

The plate worked magically but some of the strap points broke down after 450 miles - I started to make a female mold so I could build one using carbon with new attachment points. Shown here is the plug, wrapped in foil so I could fill in an reshape the plate. It is almost ready to start building a female mold...never got around to finishing it (I've been driving boats since - not pulling lines much recently).

Bottom line; it works but use with caution. You may want to try using the fiberglass filled resin...for the next small project I come up on like this, I may give that a try!

john132

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Here are some of the final project ...................

j.m.

looks pretty good!

(especially considering all the negative comments)

bentwings

John, Nice job and nice plane. Now just think of how much less fun you would have had doing it the easy way.... haha Pardon my humor. You done good. Congrats.

Hey all ya other naysayers, I'm having barbecued crow tonight. Want to join me. They say it tastes like chicken. hahahah