F-86 Sabre (90mm) Fast Foam - Page 7 - RC Groups
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This thread is privately moderated by Herb, who may elect to delete unwanted replies.
Feb 10, 2010, 01:25 PM
More jets than a carburetor
skydve76's Avatar
Couple questions:

How do you think it would do on grass take offs?
For the aluminium coating you use, how doe sit stand up to force? Does it wrinkle easy? i've used metal tape before and the problem is the wrinkles that show up with any type of stress.

I also wanted to point out that I used the polycrylic type stuff for glassing. I found that it takes over a week for it to dry correctly. I found by using at least a 60 watt bulb in a lamp and keeping it close to the surface, it will dry quite hard in several hours.

I found it odd that you used epoxy to glue things together. I found my epoxy breaks, an then breaks away from the foam. When I built my fly fly mig, I used both epoxy and polyurathane glue, by alternating spots along the joints. All epoxied spots gave out, leaving only the PU glue to hold.

Whats your secret with getting the epoxy to hold foam together?
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Feb 11, 2010, 11:24 AM
Lithium Member
Herb's Avatar
Mine takes off fine from short grass ... long thick grass of course would not work.

It is a light airframe, so given enough power it's perfectly suited for grass takeoffs.

The flyfly struts are marginal @ 8lbs, I use tams retracts which are strong, but at some point I might have to replace the struts with something more durable. But for now they works, so I keep them on.

I have no wrinkles on the aluminum foil (or aluminum monokote) because my F-86 airframe is fully glassed. So the foam it has a thick rigid shell, just like a composite airframe. I think it's pointless to put an alu finish on bare foam, it will indeed wrinkle where the foam bends.

I don't use epoxy for gluing except in a few places that require it, most of gluing was done with lightweight PU if you read the thread, https://www.rcgroups.com/forums/show...5&postcount=14.

Also, I don't use polycrylic, it's a waste of time, https://www.rcgroups.com/forums/show...2&postcount=16
Feb 11, 2010, 11:41 AM
More jets than a carburetor
skydve76's Avatar
I bet the PU for glassing is why my metal tape wrinkles. Going to try z-poxy. Thanks!
Feb 23, 2010, 12:30 PM
Lithium Member
Herb's Avatar
Yes ... good luck with the z-poxy, it should work well ...
Feb 26, 2010, 05:00 PM
More jets than a carburetor
skydve76's Avatar
I didn't find z-poxy at my local HS, so I picked up something called "Finishing Epoxy". Its called a 20 minute epoxy, and it is very clear and shiney.

I put a coat of it on one intake duct on my mig-29. I thinned it with alchohol so it was watery. Here is what I noticed:

It gets tacky quick.
It needs lots of heat to cure
It is hard to get on there "Even" enough. With sanding it makes a good under layer for the paint. Much stronger than PU but not much more weight. I question how hard it would be do to fiberglass with the takckyness, it would pull on the fiberglass while scraping.

Question: Have you ever used the z-poxy as a "top coat" for the paint? I think the gloss and paint protection would be great if I could figure out how to brush it on even. I don't think an airbrush would work, but maybe what I got is not the same as the z-poxy. While from a distance it would look fine, clearly there are brush strokes and places where it "builds up" more than others.

This is what I have here:
Feb 26, 2010, 07:58 PM
Never too much detail
fredo21's Avatar
I laminated a slipso fus with that stuff. Went on well didn't get tacky till about 15+ mins at about 24 deg C. Haven't tried to dilute it. Wet the glass well, I used a credit card to spread and tissue paper to blot after all the glass was wet. I am sold on the stuff. Will not be going back to WBPU. It is very tacky in 2 hours, set pretty hard in 8. I was using small amounts, as its a very small plane. Maybe with larger volumes it sets up quicker?

Feb 27, 2010, 08:02 PM
Lithium Member
Herb's Avatar
Originally Posted by skydve76
I didn't find z-poxy at my local HS, so I picked up something called "Finishing Epoxy". Its called a 20 minute epoxy, and it is very clear and shiney. ...It gets tacky quick. It needs lots of heat to cure ...It is hard to get on there "Even" enough.
I think what you used is probably quite different from laminating epoxy, which dries hard like a shell (at least mine does).



The fast cure (30min, 5 min) epoxies get increasingly softer and more rubbery ...

For laminating you need some hard shell stuff. That usually is rather slow cure I think ?

Besides Z-Poxy there might be other laminating epoxies like that (I would guess west marine has a west system laminating epoxy).
Feb 27, 2010, 11:02 PM
Registered User
West works well, been using it for years. A quart of epoxy + the small (pint?) can of fast hardener + a set of pumps will give you enough for many foamies. Perhaps 6 of these big planes with a full glass job? A 2 squirt batch did the wing bottom on my Mirage, 2 squirts for the top and a total of 3 squirts in three seperate 1 squirt batches for the fuse and fin. A 2 squirt batch is about 1.5 ounces of epoxy.
Mar 02, 2010, 11:31 AM
Lithium Member
Herb's Avatar
Yes the West system stuff is probably a much cheaper substitute to the Z-Poxy for higher volume JePe Fast Foam work
Mar 02, 2010, 09:50 PM
RC Fanatic
Reco's Avatar
I have always used Z-Poxy Finishing resin to apply FC. I dilute it with denatured alcohol until its about the thickness of heavy cream. I brush it on with a 1" paint brush. After it cures I use Auto Body Filler and a plastic squeegee to apply it. I let that set up and then wet sand and repeat if necessary. After that you will have a fine surface for paintng or applying the metal tape.
Mar 02, 2010, 11:32 PM
Registered User
No, never. There are sprayable two part clear paints for that.
Mar 02, 2010, 11:51 PM
More jets than a carburetor
skydve76's Avatar
Originally Posted by Chris True
No, never. There are sprayable two part clear paints for that.
Will they eat foam?
Mar 03, 2010, 12:11 PM
Lithium Member
Herb's Avatar
No as far as I know. What Chris uses is a two part epoxy based paint w/o harsh solvents.

I have used acrylics such as Future or any brushable clearcoat such as varathane pu or polycrylic, or testors clearcoat in an airbrush.

The problem with some (actually most) spray paints or spray clearcoats is the solvent in the aircan version.

Also most Tamiya acrylics in a can are foam safe, most Testors are not (different solvents used). You need to test them first !!

So the best way to find out is to take your can and spray on a piece of bare white foam ... Not the plane ... That is what I always do.
Mar 03, 2010, 08:24 PM
Registered User
Guess you have to ask yourself what "protect the paint" means. If you use nothing but foam safe stuff from the foam up it isn't going to be particularly durable for the most part, especially if everything is inexpensive. You're going to be able to mark it or chip it etc. If you glass with epoxy then you've got a barrier and foam safe isn't an issue.

It's all a trade off, two part paints are expensive / can be heavy / and use those non-foam safe solvents. There are some waterbase good quality / expensive paints you can get a pretty good finish with, if you add the cross linker it is impervious to most anything and very chip resistant. It's a little difficult to work with, Nelson is the one I've used.

OTOH you can get a light good looking finish with various one part systems, it'll chip and mark but protect the model and touch it up every few years. I've seen guys doing pretty nice work with latex paint lately which is dirt cheap. How long is the model going to last?
Mar 07, 2010, 02:54 PM
Lithium Member
Herb's Avatar
JePe has a new page specifically on how to finish foam; he discusses in some detail the pros and cons of both water-based and epoxy products. A very good reference.

The only drawback is that I have no idea at the moment what some of the correspoding products might be in the US, e.g. the water based acrylic primer sounds interesting.


Here is my own conversion to pdf:


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