Does CA Glue Shrink?

[Motorman]

I made a built up stab/elev and covered it with 1/32" balsa. It sat for a couple weeks and now there's indentations all along the back of the leading edge stick like a fillet of glue there shrank and pulled the sheeting down. It's only on the side I glued first. Didn't glue the sheeting on the other side for a couple of weeks after. I guess I can put some superfill on it but, what happened?

Thanks,
MM 

[Tim Wescott]

If you're putting enough CA on the thing to make a fillet you're putting on too much.

I don't think CA shrinks, at least not much -- I'll go money that it doesn't shrink nearly as much as carpenter's glue or Ambroid does.

It could just be from temperature or humidity cycling, or because of how you clamped it when you put sheeting on the opposite side.

[Avaiojet]

Photo?

[Dan McEntee]

  I think the only way for the condition you describe to appear is for there to be a gap of some kind between the sheeting and the structure. If the sheeting is only 1/32" it won't have a lot of strength on it's own to resist  pulling down. And as already mentioned, if you have a fillet of glue in that location, you have too much glue, especially for CA. All a fillet of CA glue does for you is add weight. CA doesn't gas off and get lighter. I think it can contract as it kicks of there is room for it to do that and not enough strength in the balsa to resist it.  If someone asks me the question of how much glue to use, I answer that if you can see glue coming out of the joint, you used too much glue, especially if it's CA.
   Type at you later,
    Dan McEntee

[Motorman]

[Gerald Arana]

Personally, I'd strip that wood off and apply new sheeting. Filling it would add weight at the tail.................the worst place. IM(not so)HO 

Jerry

[Motorman]

It looks worse held up to direct light but it's not that bad and it's on the bottom. I'm just wondering why it did that, it's like it's pulling a vacuum inside.

MM

[john e. holliday]

I've never known of CA to shrink, even with layers of it on my fingers.   Did you poke vent holes thru the ribs?    If not, strip off the offending sheet and poke some vent holes with a straight pin.  The hole does not need to be that big.

[Curt D Contrata]

I think it is simply the results of sheeting an open surface with 1/32" balsa. Have you done this before? I've tried it and ended up with a huge mess once I started with dope and tissue.

I think you should sand it all off and sheet it with 1/16", or simply start over.

Curt

[Tim Wescott]

I think you should sand it all off and sheet it with 1/16", or simply start over.

My thought exactly.  Most 1/32" wood is pretty dense, so if you use really light 1/16" wood you may not even add that much weight.

[Avaiojet]

Looks like indentations from pressure?

I CA plenty and I've never seen an issue like this?

The X-Files.

[Tim Wescott]

I did a web search out of curiosity, and found nothing relating to cyanoacrylate glue and shrinkage.  If it were an issue there'd be a ton of industrial white papers on how to deal with it, and glue companies touting low-shrinkage formulas.

So I think it's safe to assume that it doesn't shrink much.

[John Leidle]

   From here it doesn't look like the CA shrunk ,,, looks like  the most rearward sheeting shrunk in the open bays & the rest at the joint   .. . .. no matter what I'd do as Curt said .  and in doing so you might even save time.
    It is a mystery ,  John 

[Paul Walker]

Did the sheeting get wet after it was glued on?

[Curt D Contrata]

Did the sheeting get wet after it was glued on?

That is what happened to me. I was making a 1/2A Nemesis and used 1/32" for LE sheeting. All went well until I was covering with wet tissue and it all went to hell. 1/16" seems to tolerate moisture much better than 1/32".

Curt

[Motorman]

It's down in my basement, maybe the humidity got to it?

MM

[Dan McEntee]

    Moister of any kind is what starts the reaction of CA glue. And no reason to think that it doesn't "shrink." Contraction is more the correct term. Judging from the photos, you used way too much glue, and when it kicked off, the heat generated sucked all the moister out of the wood and it pulled. I almost never use CA for any kind of sheeting, especially if it will need any sanding, since CA doesn't sand very well.
   Type at you later,
   Dan McEntee

[Bill Johnson]

    Moister of any kind is what starts the reaction of CA glue. And no reason to think that it doesn't "shrink." Contraction is more the correct term. Judging from the photos, you used way too much glue, and when it kicked off, the heat generated sucked all the moister out of the wood and it pulled. I almost never use CA for any kind of sheeting, especially if it will need any sanding, since CA doesn't sand very well.
   Type at you later,
   Dan McEntee

That makes sense, Dan. It's the first hypothesis that sounds right.

[Motorman]

It's the side I glued first so there's less glue than the other side that didn't do it. I didn't use that much glue.

MM