Foam core ?s
 

I have a wing that has the balsa loose at the seam where two sheets join together. The joint is together tight but there is just a little pucker about 3/8 inch wide. Not really a pucker though just can tell it is not stuck to the foam. Can I use a trick of the trade my father taught me with loose veneer? Thin wood glue a little with water and use a syringe and a small needle and inject the glue under the balsa and clamp or weight down until dry. will this work?

This kit calls for the main gear blocks cut into the wing and epoxied . Is there any tips Or is this process pretty easy.

RE: Foam core ?s
 

Dalolyn,

You have a 50/50 chance of that working for one reason. Usually (there's a word with authority) if balsa has separated from the foam core there are two reasons. The most obvious is that no glue (epoxy/sorghum/etc) was applied to that area OR.... the wing was sheeted using contact cement and the sheeting was put together before the contact cement dried,causing a void underneath the balsa. Easy to find out which one... just push down on the "lifted" area. If you finger goes below the sheeting line, you have a void and need to cut out that area and repair/fill it prior to regluing the sheeting. If no void, the needle/glue/weight injection method will work just find... but.. I'd suggest an epoxy rather than a white glue... reason being that the white glue, under that sheeting might take forever to dry... whereas the epoxy will chemically set up no matter the environment. Hope this helps...should get you back on your project.. btw.. what kind of plane is it????

take care,

Dan
Carolina Custom Aircraft

RE: Foam core ?s
 

Should I thin the epoxy any? It is a JM modelcraft Mini Star .40 size sport pattern foam wing core, fiberglass Fuse, balsa tail feathers. I am going to change ir from a trike gear to a tail dragger.

RE: Foam core ?s
 

Epoxy can be thinned some, but not much.

If it were mine, I would lay a straght edge at the end of the lift, spanwise direction, and slice it open. Then you can peek in, see what needs to be done, and probably spread the correct adhesive, too.

RE: Foam core ?s
 

If you thin it with anything you may risk eating the foam, acetone, etc. Warm the epoxy to get it to flow, use 1 hour or more. If you try 5 min, and warm it it will most likely harden in your syringe before you inject it.

RE: Foam core ?s
 

You can use rubbing alcohol, a little is all that is needed, to thin epoxy. Shouldn't hurt the foam.

RE: Foam core ?s
 

If it were me I'd cut a section out all around the bad section - I've tried the syringe injection with limited sucess over the years. For one thing, it's hard to get the skin to go down flush sometimes. And it's hard to be sure you got enough new adhesive in to rebond everywhere.

After removing the skin, I clean up the core and fit a piece of 3/32 balsa (assuming it has 1/16" skins) , then epoxy it in place. Final step is sanding the surface fair with the rest of the skin. For me this is a fast and easy way to get a positive fix.

One last thing. I'd go some distance beyond the faulty area to make sure I got it all.

FWIW

RE: Foam core ?s
 

Repeat after me... NEVER THIN EPOXY....NEVER THIN EPOXY...NEVER THIN EPOXY.... <<<repeat 1000 times......;)

Alcohol will change the chemical makup of the bond and change amount of strength of the bond... if you need thin epoxy (like this) take at least 60 minute epoxy, mix it, and hit it with a hair dryer/heat gun.. it will flow like water with no loss of bond strength... Alcohol is for cleaning up your tools/hands AFTER you have made the repair.

Dan
Carolina Custom Aircraft

RE: Foam core ?s
 

Another alternative is the odorless foam safe CA glues. Put some pinholes in the wood, wick in the CA and hold it tight for a minute.

If the wing was not built by yourself, I would be slicing into it to see what's going on. You don't want a repeat of FRXTim's wing folding episode.


Mark

RE: Foam core ?s
 

I agree with completely with Dan's comment about not thinning epoxy, but it's not a good idea to use any solvent to clean it off your skin. Doing so only helps it get into your body thru the skin.

Virtually all epoxies are toxic to some degree or another. Individual's tolerance varies, but the effects are cumulative and non-reversable. Once you reach your personal tolerance level, even the slightest whiff may induce a violent reaction. There's no way of knowing what your limit is or how close you are to it. Admittedly most of us never get to that point, but why take a chance?

The safest way is to use nitrile examining gloves or a barrier cream. Or at least use a waterless hand cleaner.

It's a personal decision, but I know someone who reached his limit using primarily epoxy glue.

OK, I'll get off my soap box.

RE: Foam core ?s
 

...but I know someone who reached his limit using primarily epoxy glue.

Well. What happened to him?

RE: Foam core ?s
 

The guy I know that it happened to got terrible, terrible rashes all over his arms and parts of his body. As I recall it was so bad he could not work for awhile. He used epoxy for years without problems and then one day bag it hit him.

RE: Foam core ?s
 

ya I agree, most people think chemicals that have an offending odor are more harmful, Proof of this is all my family is still alive even though Ive had Chile for 3 days. ha ha

Is it ok to thin epoxy to fuel proof? I have used this method many times in the past.

RE: Foam core ?s
 

He said he got violently ill and developed a skin rash too. If I invited him into my shop, he'd ask if I'd been using epoxy recently ... apparently just a slight whiff of the smell would start a reaction.

Sorry, I didn't mean to come across as a crusader.

And I'm not going to stop eating chile either <grin>.

RE: Foam core ?s
 

You are absolutely right though. Even latex paint needs to be used with ventilation. same with the use of mineral spirits to clean stuff. ventilate and use latex gloves.