Good filler

[Myzee]

Just wondering what everyone uses for a filler added to epoxy? I may need to do this to attach formers inside a fiberglass fuse.
Thanks
Myles

[Terry Gauvin]

You can buy fiberglass matting at CT that is approx 1/4" thick. If you cut it in 3/4" strips and soak it with epoxy it can easily be formed to create a 90 degree joint between the formers and fuselage sides. Do not use any more epoxy than required to minimize weight.

[Myzee]

Boy, talk about a brain freeze on this one! I can't believe I didn't think of that! DOH!
Thats what happens when you post while working the graveyard shift! :wstupid:
Thanks for the wake-up Terry!
Myles

[can773]

Just wondering what everyone uses for a filler added to epoxy? I may need to do this to attach formers inside a fiberglass fuse.
Thanks
Myles

Cabosil, available at any place that handles epoxy/glass/carbon etc.

[ronm]

Chad:

Is Cabosil like a "milled fiberglass" product?

Ronm

[Kevin McGrath]

You can chop up the same Crappy tire mat with a pair of scissors add some resin and mold it into place too..........alla samee milled?

[Propworn]

Better yet are micro balloons they also weigh next to nothing and make the epoxy easier to form.

Dennis

[JimMcIntyre]

Just don't inhale them or get them on you skin... ouch! :cry:

[can773]

Chad:

Is Cabosil like a "milled fiberglass" product?

Ronm

No they are hollow silica (glass) balls basically. They add volume but not weight and usually make the epoxy easier to sand and less runny. Great for fillets around firewalls in glass fuses or fillets around anything for that matter. Depending on the mix ratio you can really change the epoxy.

Its similar to miro-balloons that you can buy at the hobby store, but I find that the stuff from a composites place is of much better quality, and much much cheaper.

What I will do sometimes is mix up some epoxy with Cabosil, then mix in a small quantity of milled fiberglass (great planes sells a little bottle of it). Sands better and makes a better fillet for load bearing areas then either product by itself.

If I really want to reinforce a former, I will use Kevlar cloth in the corner, as its lighter than glass for equivelent if not better strength.

I have attached a picture of a firewall put in a carbon fuselage, basically the white colored glue is epoxy with Cabosil. The fillet is nice and light, easy to shape and shouldn't run. Just FYI, the firewall weighs 9 grams (nomex honeycomb/carbon fiber sandwich) and supports the YS 140DZ making 3.5 hp. Arent composites wonderful!

[ronm]

That makes a nice job Chad!

Who sells the honeycomb stuff? Central hobbies?

Ronm

[can773]

I just make it myself, its pretty easy to turn out a nice product.

5.7 oz (either standard or 2x2 twill weave) or any cloth, you can experiment.

www.fiberglasssupply.com

Honeycomb is from Fiberglast

http://www.fiberglast.com/showproducts-category-Sandwich%20Cores-18.html

At the bottom of the page is the honeycomb

2 plates of acrylic sheet (plexiglass) as big as needed to make a panel. The thicker the better as it helps keep everything straight.

Anyways, put green liquid partall on the acrylic sheets and let dry, usually one coat is enough.

Then spread a thin coat epoxy (west system or equivelent) on one side of each acrylic peice.

Lay down your precut carbon cloth and soak thoroughly with epoxy. Once good and wet squeege out as much as possible.

Lay your precut honeycomb peice on one of the wetted carbon layups. Then place the other acrylic sheet with carbon on top to make the sandwich.

I put about 80 lbs on a 6"x18" panel and it works good.

Let dry and voila. Its easy to cut with a bandsaw or scroll saw.

It ends up being 1/4" thick, has the weight of contest balsa but the strength of light ply (or a little better).

Its a bit of an investment to get all the material, but once you have it you will have enough for 100 years.

Below is the ultimate servo tray, a friend made it from a panel of the sandwich material that I made for him.

[ronm]

That's really cool!

I could think of 100's of uses for this!

Thanks for the info!

Ronm

[JimMoss]

Chad mentioned how cabosil is almost the same as microballoons, it is but .....

The only difference is that when you go to sand the cabosil it is much harder than the microballoons. :wink:

[AJCoholic]

One thing you have to remember, is that different fillers are to be used for different applictaions.

Microballoons are NOT meant for hugh strength reinforcement (like the former mounting Myles is doing) or anchoring hardware, etc. They provide a good thickening, and forming ability and make great fillets. They are lightweight also, a plus for filling. But they weaken the bond.

For strengthening the epoxy, I suggest a finely chopped glass, like West Systems coloidal silica. It makes a great thick paste, but is strong like steel when dry. It is not heavy chopped, and is still easy to form once mixed.

Then there are medium strength fillers that are sort of a halfway between a pure microballon and a pure mechanical filler.

I personally use 3 or 4 fillers (some West System products and some other brands) and if you want to know what to use, give Canada Composites (Mississauga Fibreglass Factory Outlet) a call and talk to the tech guys... they know thier stuff.

Another excellent thing to get is the West System guide to their fillers and uses. They rate them from 1 to 4 for filleting, bonding, laminating, etc and if you dont want to buy their brand, you can still reference the same material from another supplier.

And dont forget buying in bulk is cheaper, a LOT cheaper. I buy my microballoons in a gallon pail for about $10, you know what a tiny can costs at the LHS....

[747drvr]

Cabosil is the same as coloidal silica. It doesn't add strength to the mix , just makes it thixotropic ( I love throwing around big words !) . This just means that the epoxy is thickened , won't run and can be made into fillets. Milled fibreglass has the same effect but can get lumpy if you add too much.


Marc

[Myzee]

My main application is for the main former that the wings attach to in my turbine BD-5, so I want it to be tough. Although I will be using the bonding method for other formers, they will not need to be so extreme.
Andrew,
I lost the phone number for Canada Composites, could you post it again for me please?
Thanks
Myles

[SteveM]

I've used the micro balloons with epoxy with great results, but as mentioned already this should not be used where strength is required.

I recall that Sig used to sell a two part epoxy putty that could be used for adding strength and fillets. I no longer see this product on their website so it may be a discontined product.

I also once had some two part epoxy putty glue from europe but I can't remember the product name. It was a German manufacturer and the puty was a grey/taupe colour once mixed.

[AJCoholic]

Mark, it does make the epoxy tougher, (stronger if you will).

quote:

406 Colloidal Silica is a thickening additive used to control the viscosity of the epoxy and prevent epoxy runoff in vertical and overhead joints. 406 is a very strong filler that creates a smooth mixture, ideal for general bonding and filleting. It is also our most versatile filler. Often used in combination with other fillers, it can be used to improve the strength, abrasion resistance, and consistency of fairing compounds, resulting in a tougher, smoother surface.

[messacar]

For those who may be interested, Cabosil is also used as a flatting agent in paint of any form (ie: Dope, Epoxy etc.). It's inert and a little goes a looooooong way.

Fred

[JKovats]

I use corn starch if it's not a strength issue. No weight, easy to sand, readily available upstairs. Comments?? works great with zpoxy.

John