Help - CRITICAL ERROR - will wood glue stick to primer?

Oh, NO... I'm an IDIOT.

I just started priming a rocket (gray Rust-Oleum automobile primer) and suddenly realized... I forgot to attach the launch lug!!!

Is it too late to do this? Do I need to sand it off, or can I glue the lug down to the primer? I've only used one coat so far - about 20 minutes ago - and have not yet sanded anything.

No, wood glue won't stick to primer very well. Let the coat you applied dry and just carefully scratch off the primer and rough up the body tube where your lugs are going to go.

Well, I think it is safe to say you are not the only "idiot" to ever do that! At least you noticed it now, not at the launch pad.

I'm not certain, but I think you are going to want to sand the spot off before gluing. We'll see what other people say, but that's what I would do.

You'd do best to sand the primer down in the spot that you've primered until the glassine is gently roughed up, then glue on your launch lug.

You CAN glue the lug to the primer, but there's a good possibility that it will pop off at some point, probably taking the underlying primer with it, since the only thing that will really be bonding the lug and glue to the rocket will be the primer itself...

It's not THAT big a deal to sand down JUST THE SPOT YOU NEED TO GLUE THE LUG ON, wipe off all the primer dust with a damp paper towel, let that air dry a few minutes, and then apply a thin layer of yellow wood glue. You can apply a thin layer of yellow wood glue to the surface of the lug that will be bonded to the rocket at the same time, and allow both layers of glue to dry for 20-30 minutes or so, up to an hour if needed. Then apply a second thin layer of glue to the lug and stick it carefully onto the glued spot on the rocket. This will create a near-instant bond between the lug and the rocket (and a joint stronger than either the lug or the underlying paper tube itself!). This is called a double-glue joint and is about the fastest and strongest way to join stuff with yellow wood glue. You can then lightly fillet the lug flanks to the tube for a more blended and stronger appearance. My advice is to keep the fillets small to reduce drying time and reduce the possibility of bubbles or voids or pits opening up in the fillet material as they dry.

I'd let the lug/fillets dry overnight, and then you should be ready to re-primer the lug and fillet area. Follow the instructions on whatever rattlecan paint you're using (presuming you're using rattlecans). Be sure to observe "recoat times" as some brands and types of spray paint are more "sensitive" to recoat times (especially Krylon) than others, and you don't want it to go "wonky" and cause more problems. I recommend 2-3 LIGHT coats of primer, rather than a single heavier coat, to blend the area with the rest of the primered rocket. Light coats tend to create fewer problems than heavier coats, especially when "blending" with earlier coats already applied.

Then you can allow the primer to dry per the can instructions before sanding it.

Best of luck! OL JR

lcorinth said:

Oh, NO... I'm an IDIOT.

I just started priming a rocket (gray Rust-Oleum automobile primer) and suddenly realized... I forgot to attach the launch lug!!!

Is it too late to do this? Do I need to sand it off, or can I glue the lug down to the primer? I've only used one coat so far - about 20 minutes ago - and have not yet sanded anything.

Click to expand...

OH Man Daniel! Wish I had a nickel for every time I've left the Launch Lugs off COMPLETELY Finished Models. I mean completely finished multi-Color models...Sanded the primer two or three times...never even noticed..NO LUGS! Yeap! I'd have plenty of money for hobby stuff

It is absolutely possible to simply glue on your lugs to the Primer but you'll be relying on only the adhesion of the primer to the substrate(body-tube) which is not really that strong a mechanical bond to hold the lugs in place. Not really the best choice.

It's best to wait for your primer to dry, Carefully mark the locations of you Lugs, using the point of an X-Acto knife scrap the primer off down to bare Body tube roughing up the tube surface as you go then double Glue joint your Launch lugs in place.
I'd suggest reinforcing the lugs with Fillets of either wood glue or epoxy whichever your more comfortable using. Once these fillets are dry and sanded to the shape you want continue the priming/finishing sequence.

Not a critical error at all...just an oversight

Too many times we get to primer or even the perfect paint job when that nasty little piece of straw reappears from it's hiding place on our workbench. Like the others say you got to get beck to the raw surface. If you already have a good paint job, mask off the small rectangle of contact area for the lug before you sand or scrape. That way minimizes the chance of scratching or sanding on your pretty paint. Allow enough area for small fillets on your launch lug.

luke strawwalker said:

You'd do best to sand the primer down in the spot that you've primered until the glassine is gently roughed up, then glue on your launch lug.

It's not THAT big a deal to sand down JUST THE SPOT YOU NEED TO GLUE THE LUG ON, wipe off all the primer dust with a damp paper towel, let that air dry a few minutes, and then apply a thin layer of yellow wood glue. You can apply a thin layer of yellow wood glue to the surface of the lug that will be bonded to the rocket at the same time, and allow both layers of glue to dry for 20-30 minutes or so, up to an hour if needed. Then apply a second thin layer of glue to the lug and stick it carefully onto the glued spot on the rocket. This will create a near-instant bond between the lug and the rocket (and a joint stronger than either the lug or the underlying paper tube itself!). This is called a double-glue joint and is about the fastest and strongest way to join stuff with yellow wood glue. You can then lightly fillet the lug flanks to the tube for a more blended and stronger appearance. My advice is to keep the fillets small to reduce drying time and reduce the possibility of bubbles or voids or pits opening up in the fillet material as they dry.

Click to expand...

Micromeister said:

It's best to wait for your primer to dry, Carefully mark the locations of you Lugs, using the point of an X-Acto knife scrap the primer off down to bare Body tube roughing up the tube surface as you go then double Glue joint your Launch lugs in place.
I'd suggest reinforcing the lugs with Fillets of either wood glue or epoxy whichever your more comfortable using. Once these fillets are dry and sanded to the shape you want continue the priming/finishing sequence.

Not a critical error at all...just an oversight

Click to expand...

Whew! So, here's what I did, guys.

I took a little piece of coarse (150 grit?) sandpaper and wrapped it around the lug itself, then used that to sand just the area where the lug should be placed - I could still just see the mark under the first layer of primer. I was concerned about oversanding, because while trying to sand off wood filler in spiral grooves, I've oversanded the body and ended up with a fuzzy airframe that neither primer nor paint could completely fix - definitely not what I want! So, I got just a tiny area sanded free of primer.

Then I roughed up one side of the launch lug itself, and applied a bit of wood glue to it and touched it to the body tube where it would end up living. Then I let both glue bits dry - got to have a real use for my reverse action tweezers (hey, that turned out not to be a silly purchase!) by keeping the launch lug in them to keep them from rolling over and gluing itself to the table. Once the glue was dried, I reapplied a little glue for a nice double glue joint, and followed that with fillets... All of this is stuff you experienced guys already know to do, but for me, I'm super pumped about learning how to fix problems (I've had at least one per rocket) and how to do things properly.

Aaaand now I have to wait to prime because it'll be raining and/or humid for the next... Well, seemingly forever.

Thanks for the advice, everybody!

You're welcome...

At least you caught it before you got to the launch pad... LOL

Best of luck! OL JR

Check out this video link - https://skybusters.org/Images/11/NYP01_FTBOD.mpg

This is the Flying Traffic Barrel of Death, NYPOWER 2001. A great level 3 attempt that failed because the ring-tail was glued to primer. The joint failed on landing simply for that fact. Always glue part-to-part, never to any kind of paint.

Pat

You are quite welcome;
Working on a very nearly completed Scale Model last night I realized I have done it again. NO Launch Lugs... Ha ha ha!

Not to panic...just cut the lugs, a few small scraps and a little epoxy... were ready for decals

To make filling, sanding, and priming easier, I typically leave off the launch lug. Before final painting, I locate the area where I want it, sand down to whatever is under the priming substance THEN attach and repair. Maybe it's 7's to do it that way but I like it.
-Ken

We've all done it at some time. Sand the area for attachment down to the bt. I like to cut a small slot or drill a couple holes with the tip of an Exacto knife, some 5 minute epoxy and your good to go. Finish as you please after that. The wood glue won't hold on primer even if you sand it---it will fail !!! As a rule, I just go straight to epoxy to mount my lugs anyway.

The other option available to you is to leave that drag inducing object off the airframe, and launch with a tower!