Best Glue For Painted Surfaces?

[lakeroadster]

What would be the best type of glue to use to attach a painted cardboard component to a painted paper body tube on a LPR rocket.

The cardboard component isn't a flight critical component.

Thanks in advance...

 

[Steve Shannon]

What would be the best type of glue to use to attach a painted cardboard component to a painted paper body tube on a LPR rocket.

The cardboard component isn't a flight critical component.

Thanks in advance...

It almost doesn’t matter. The bond can be no stronger than the peel strength of the paint.

 

[BABAR]

As Steve said, bad idea.

If already painted then sand off the contact surfaces so you have barecardboard to bare balsa. One thing that can help after sanding is to pre-color the bare area with a sharpie marker of the appropriate background color, if you can find a sharpie of the right color. White is obviously not an option.
the sharpie marker color will not do anything to impede the adhesion of the glue but will make the joint less cosmetically noticeable. You could also use a clear glue which should give you a good fixation but also won’t mess things up cosmetically as much.

I have never tried it, but in some cases maybe you could dye the glue the background color.

 

[lakeroadster]

Glue will be hidden.. glueing the back faux engine pod section (that has the cardboard adapter) into the larger front pod section.

In-flight loading should be minimal on these parts.

You'd think there would be a glue that would "eat into" the enamel paint while the glue was "raw" and thus give better adhesion? Just wondering.

 

[blackjack2564]

I would use
Elmer's clear

 

[GlenP]

Glue over paint is a good technique to remove the paint, and the part along with it. Ever tried glueing on a launch lug after painting? If you don't want to sand a stripe down to bare wood for a good glue joint, and you really don't need the joint strength, you might consider cross-hatching (or hashtagging) into the paint to the bare wood with an X-acto blade where it will be covered up (#crosshatching). The glue can seep into the bare wood through the scratches in the paint. Or, poke little holes (easy for soft balsa) with a fat T-bar needle so glue can seep into the bare wood in several spots. This technique is sometimes called glue dowels, since the dried glue forms a kind of dowel type joint in the holes in the wood. Those tubes are probably not going to hit the ground first since your engine mount sticks out more than they do, so strength is not such a big concern. The glue on the internal carboard adapter to the larger tube is probably all you really need anyway. Assuming you don't paint the contact surfaces of the cardboard supports and the inside of the outer tube. Were the insides of the tubes painted? I thought at first you were talking about glueing to the painted wing, so my suggestions might not work at all if you have painted the insides of the tube, I was a little confused about what you were talking about.

 

[lakeroadster]

....Those tubes are probably not going to hit the ground first since your engine mount sticks out more than they do, so strength is not such a big concern. The glue on the internal carboard adapter to the larger tube is probably all you really need anyway. Assuming you don't paint the contact surfaces of the cardboard supports and the inside of the outer tube. Were the insides of the tubes painted? I thought at first you were talking about glueing to the painted wing, so my suggestions might not work at all if you have painted the insides of the tube, I was a little confused about what you were talking about.

Yes the inside of the tubes are painted. I could take a Dremel with a sanding disc and scuff the inside out. Sound like the consensus is that is required to ensure adhesion.

I had contemplating just slipping the rear sections in for display, but removing them at flight. But that seems like a cop-out.

 

[GlenP]

OK, this picture makes much more sense. Forget everything I said, you can just friction fit those things like you would an engine. In fact, just insert them after freshly painting them. Ever painted a window shut? Those things can easily get stuck in there essentially permanently, if the cardboard X-cross supports are strong enough. They can't be lifted off, like from the outside of a tube i.e. a launch lug on a painted body. Heck, just add more paint, before and after insertion. As long as you don't think they can hit the ground on landing, that will hold them for flight.

 

[lakeroadster]

Thanks for the input. Also worth noting: the Army Green paint is flat.. and quite rough... which should help to give the glue "teeth" to hold onto.

They can't be lifted off, like from the outside of a tube i.e. a launch lug on a painted body. Heck, just add more paint, before and after insertion. As long as you don't think they can hit the ground on landing, that will hold them for flight.

Very insightful comment Glen... since they are internal, and span the tube.. yep, that should make them stout. And I can't imagine them hitting the ground, they are protected by the fins and the rear body stiffener.