Foam Board Repair... or Punt?

[Inq]

I'm new to using foam-board in anything... much less an airplane. I've had the hinge area delaminate on both the rudder and the stabilizer. I thought I did Josh's smearing of hot-glue trick, but now, I'm not sure if I got every place. When you all make repairs, do you just glue this down or cut it off and replace it? Are there any other tricks to re-enforce this area?

 

[JasonK]

that you can put a bit of glue in and repair, you should also then open the joint as far as possible, put a small amount of hot glue on the joint, then wipe it off, it leaves a very thing and flexible layer of glue that makes the joint quite a bit stronger.

I know Josh does that in at least some of the built videos, but I don't recall one for sure to show the technique.

 

[Foamforce]

So far I’ve had good luck just sqeezing a lot of hot glue as far up under the delaminated paper as possible, then dragging a piece of foam or credit card along the back side to force as much glue back out as possible, and then cleaning up the inside of the hinge. Sometimes after I do that my hinge is too stiff because I wasn’t able too clean it out well enough, so I just reapply hot glue in the hinge, which melts the old glue, and then I re-wipe it. I haven’t had to replace a control surface yet. That said, I’ve only been doing this a few months, so YMMV.

 

[Inq]

I know Josh does that in at least some of the built videos, but I don't recall one for sure to show the technique.

He did demonstrate that in the Storch build video that I followed. I'm guessing, I must have missed this rudder area.

That said, I’ve only been doing this a few months, so YMMV.

That make you an expert in my eyes.

Thanks guys! I was hoping you all don't cut it all apart to replace this kind of damage.

 

[AIRFORGE]

I use Clear Gorilla glue for this type of repair. Clear does not foam/expand. Just a thin application where needed, and not on the actual hinge. Tape together 'til cured (about 24 hrs). And, it will add more rigidity to the vert stab where glue is applied. Then, add more hot glue to the hinge, if needed.

 

[Piotrsko]

Depends on what I'm doing, but: a piece of tape around the surface to the other side, but the problem is still the paper to foam interface and my tape trick just moves the problem somewhere else

You realize this de lamination is actually a design feature?

 

[Merv]

...When you all make repairs, do you just glue this down or cut it off and replace it? Are there any other tricks to re-enforce this area?...

That is an easy repair, just hot glue it back on. If you want to reinforce it, hot glue some of the paper on the V side of the joint. Make sure to press the paper down into the V.

It's much easier if you do the reinforcement while the plane is being built, I do this to all my hinge joints. An old covering iron make the job much easier. Apply the hot glue and smear it out as a typical glue hinge. Fold the hinge open, add the paper and hit it with the hot iron to reactivate the glue.

I've never had this hinge delaminate.

 

[Inq]

An old covering

I might have one of those in the attic from 40 years ago. Great tip.

 

[Merv]

Yes, the old covering iron is very useful with hot glue. It makes great filets & can reactivate glue that has cooled.
When your iron gets gunked up with glue, just wipe it off with a paper towel while it's hot.

 

[Inq]

It makes great filets

Oh! That's even better. The bane of my existence... crappy looking glue joints. Now I got to go hunting up in the attic.

 

[Foamforce]

On the topic of reactivating glue, one tip I’ve been meaning to share is how to remove glued on parts. I use an old putty knife with about a 1.25” blade. I heat the blade up with my heat gun until it’s pretty hot. The I slide it slowly between the glued pieces. It’s not hot enough to harm the paper, but it will melt through the glue given a little time and light wiggling. I usually have to re-heat the putty knife a few times if it’s a bigger piece I’m removing. I also wipe the glue off the putty knife onto paper towel as it builds up. Before I figured out this technique I had been trying to apply the heat gun directly to the glued parts, but that frequently warped the surrounding foam board, so using the hot putty knife made my repairs a lot cleaner.