Oops....primed BT before fin glue

I was so focused on the process of priming and sanding the BT grooves smooth, that I hit the entire BT with a primer coat, before attaching the fins.

Is that going to cause issues? Will I loose adhesion strength on the fins? I was reading where the wood to paper bond is important for fin attachment strength.

I am guessing I could sand most, if not all, of the primer off where the root edge will attach.

Newbie mistake.... guess that is how we learn. Or watching it crash and burn......

Not a big deal. Just do a spot sanding where the fins are going to go on, then proceed. It'll work out.

Yup, just sand away the Primer at the Fins.
It's Primer, and meant to be sanded.
Your still in the "Rough Draft Stage" of Painting, so anything goes!!!

I'll go you one better.

Yes, sand off the primer in the areas where the fins will be glued. Then, sand off the thin outer plastic coating on the BT (you should do this any time, pre-primered or not) to expose the basic cardboard. After all that, glue your fins on as usual.

powderburner said:

I'll go you one better.

Yes, sand off the primer in the areas where the fins will be glued. Then, sand off the thin outer plastic coating on the BT (you should do this any time, pre-primered or not) to expose the basic cardboard. After all that, glue your fins on as usual.

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Glassine is actually a thin translucent "paper". Not plastic.


Jerome

JeromeK99 said:

Glassine is actually a thin translucent "paper". Not plastic.


Jerome

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Ditto Jerome:
Glassine does NOT have to be removed to get True Wood bond between body tube and Wood fins.
However I do agree the primered area under the fin locations must be completely removed down to bare Cardboard/glassine.

Micromeister said:

Ditto Jerome:
Glassine does NOT have to be removed to get True Wood bond between body tube and Wood fins.
However I do agree the primered area under the fin locations must be completely removed down to bare Cardboard/glassine.

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+1 This.

Wood and paper glues bond excellently to glassine. It's just another form of cellulose-based paper, chemically much like the craft paper underneath. If you put glue on it, the glue does wet the glassine and soak through to some extent, into the next layer down. Sanding the glassine off the bonding areas will get more glue to soak into the underlying paper, but that's not necessary for a good bond.

I did a test once where I took two sections of BT55 tube, and used identical balsa fins glued with the same amount of glue (Carpenter's wood glue double glue joints, followed by fillets with TMTG). After thorough drying, I then attempted to rip the fins off each. They were both similar strength bonds based on my tests... they failed at about the same amount of force, both at the joint ripping the top layer of paper off the tube. The one not sanded gave a cleaner break and was easier to re-glue.

Glassine is a wonderful thing.

Marc

I was able to sand down to the cardboard fairly easy. Fins will be double glued tonight, then a primer coat on everything and another sanding. One step at a time.....

Thanks.