Thin CA Glue... Learning From My Mistake

I can't remember how many times I've had thin CA glue surprise me and nearly glue me to whatever it was that I was working on.

Today, I actually managed to glue myself to one of the fins of my Semroc Omega build...

I had just papered the fin, then used thin CA to seal the edges of it. I sanded it lightly to remove the hardened balsa fuzzy. I was about to tack the fin down with medium CA glue, when I noticed that it had clogged again. I set the bottle down, then found a pin to clear the clog. After clearing the clog, I went back to tacking down the fin. What I didn't realize (again), was that I had grabbed the thin CA, and not the medium CA glue.

Of course, it sprayed out, and firmly glued my finger to the fin instantly.

I was able to free myself with only the smallest amount of blood loss, and after cutting away the damaged part of the paper, I was able to glue in a patch, however, it'll take a few days before my finger heals.

So... How do I prevent this from happening again?

I took a RED Sharpie pen, and "painted" the lower part of the thin CA's disposable nozzle to make it easier to recognize.

A smart person learns from their mistakes. A SMARTER person learns from other's mistakes.

Please learn from my mistake.
Jim

That is exactly why I have forced my self into the habit of wearing gloves with CA. And yes, I have glued a glove to a few things....

some things I do/do not do
always keep the de-bonder close to hand with the top loosened (so that I can open it one handed). I use the 'double glue method' (wood glue).
wait 15 minutes before touching any part of my anatomy that could be embarrassing .
I no longer use the 'quality cotton buds' with paper shafts (CA will wick up the shaft).
Rex

my favorite ultra-thin CA story happened while I was working on an Apogee Aspire (my only Mid-Power kit). I was apply the stuff into one end of the body tube, onto the edge-to harden the paper where a coupler was going to fit. The tip of the glue bottle was touching the paper; I was being very very careful not to flood the tube with blue. The tube was roughly level, and my hand was on the other end of the tube-abut 7" away. About two seconds after first touching the glue bottle tip to the paper, I felt the familiar warming sensation as the glue cured on my fingers on the hand folding the tube; the glue had run up the body tube (on the outside, over the glassine) along the spiral and glued my fingers to the BT.

I love the stuff and it will always have a place in my workshop, but it has probably made me swear more than anything else in my toolkit. =)

I have found 60 grit sandpaper to be my best friend when using thin CA. I use the 60 grit on any part of my hand that gets CA on it. I have a baby smooth finger afterwards.

I hate CA but alas I admit it is useful in many situations, especially the "thin." Personally I never use CA unless I have CA remover on hand (VERY IMPORTANT--for me).

I learned something about Crazy Glue Brand CA today that I never knew before. I was using it to saturate Toilet Tissue Paper as filling in the Nose Cone of a Cardstock Plane. It became very hot, as in too hot to touch. I had never realized that in a dense packing like that with Tissue it generates a lot of Heat. I'm lucky the Part did'nt burst into flames.:y:

TopRamen said:

I learned something about Crazy Glue Brand CA today that I never knew before. I was using it to saturate Toilet Tissue Paper as filling in the Nose Cone of a Cardstock Plane. It became very hot, as in too hot to touch. I had never realized that in a dense packing like that with Tissue it generates a lot of Heat. I'm lucky the Part did'nt burst into flames.:y:

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I noticed that years ago when I was building and flying R/C airplanes. I was repairing some landing damage and beefing up the motor mounts in the cowling when I treated the Balsa wood or maybe it was Bass wood, but at any rate, it instantly became extremely hot during the reaction. That wood was tough as steel afterwards.

David

I have two stories that are worse.

1) Glued my wife's foot to the floor. No problem out running her after that happened. Hmm, that might be useful in the future.

2) Glued a rubber glove to a patient's forehead with Dermabond (CA for skin). Not useful in any circumstance and pretty embarrassing. Lesson, gloves stick and won't let go.

Astronot said:

I noticed that years ago when I was building and flying R/C airplanes. I was repairing some landing damage and beefing up the motor mounts in the cowling when I treated the Balsa wood or maybe it was Bass wood, but at any rate, it instantly became extremely hot during the reaction. That wood was tough as steel afterwards.

David

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As an R/C model airplane builder then you remember that the first CA on the market had a brand name that highlighted that quality: Hot Stuff by Satellite City.

I'm also in the 'never use CA' camp. No criticism implied for those who do, but if it's a paper and wood LPR rocket, I'm wood glue all the way, including using a thin bead to tack the fins on.

I use CA to get a quicker bond when working with epoxy. I put a thick bead of epoxy across the root edge of the fin, except for the very ends. The very ends get a drop of CA. Then, I press the fin on, the CA sets quickly, and the epoxy gives a strong bond.


Matt

I've used the "coating of CA to toughen up a balsa nose cone" trick a couple of times - with disposable nitrile gloves on to spread the CA over the NC as evenly as possible. I noticed on the larger cones (~2in) that the heat coming through the glove was getting uncomfortable.

The easiest thing to do when using thin CA is to get the Extra Fine applicator tips. The flow of CA is much more controlled, and there is far less chance of it drying in the tube. I as well, only use CA in limited circumstances.

I often lose a layer of skin from a finger tip and sand off another when using CA. It is fairly rare, and I often have CA dry out before needing it again. Would use debonder, but worried I'd get that bottle glued to me somewhere before I got it to work.

I just keep a can of acetone handy for all of the many various often frequent times I end up having to get unstuck. :eyeroll:

Maxx Mayhem said:

I just keep a can of acetone handy for all of the many various often frequent times I end up having to get unstuck. :eyeroll:

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The box of tissue I have on the table never seems to help

So, in a choice between yellow carpenter glue and CA (of any thickness, brand, or style), what you choose?

So far, I've done carpenter glue in kit builds and CA was demonstrated as an emergency repair out at a club lauch. (I bought the bottle off the vendor when I saw the value!)

Kirk G said:

So, in a choice between yellow carpenter glue and CA (of any thickness, brand, or style), what you choose?

So far, I've done carpenter glue in kit builds and CA was demonstrated as an emergency repair out at a club lauch. (I bought the bottle off the vendor when I saw the value!)

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I use carpenters' glue for pretty much all of my assembly needs. 15min epoxy comes out for gluing couplers. CA occasionally makes an appearance to harden tubes or when I'm building a laser-cut model aircraft kit. Moral of the story: every tool has its use. Play around with each type of glue and find what works for you.

Kirk G said:

So, in a choice between yellow carpenter glue and CA (of any thickness, brand, or style), what you choose?

So far, I've done carpenter glue in kit builds and CA was demonstrated as an emergency repair out at a club lauch. (I bought the bottle off the vendor when I saw the value!)

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IMHO, CA is "ok" for EMERGENCY repairs (where you want to get it back into the air ASAP) but for general construction, especially load-bearing construction glue joints, I'd rather use something else. CA doesn't age well (joints gets brittle over time) and it has poor strength in the shear plane, which is exactly the type of force you get on fin roots, especially at landing when the fin hits the ground first as the rocket is still dropping. CA's main strength is in TENSION, ie parts trying to be pulled directly off the surface. CA is useful for surface hardening balsa parts, but it seals off the pores of the wood so that wood glue cannot properly penetrate the wood grain to get a good bond, so it has to be used correctly.

Wood glue is much stronger, and can be about 95% as "quick and convenient" as CA... you want to use a "double-glue joint", that is, apply a thin layer of yellow wood glue to the fin root edge and to the tube where the fin will be attached (the fin line on the tube). Allow this glue layer to almost fully dry (it can still be a little sticky, or dry is okay, but let it dry more if the glue is still wet), then apply a SECOND THIN LAYER of glue to the fin root, then carefully align the fin with the fin line, and then press the two parts together. Ensure that the fin is aligned perfectly with the tube lengthwise, that it's sticking out 90 degrees from the tube surface, and that it's properly located fore and aft (if the fin is aligned with the rear edge of the tube or properly located ahead of the front edge of the tube by the proper amount). Hold the fin in place for about 20-30 seconds, and it will "lock" in place... you can set the rocket aside and the glue will dry quickly. I usually apply a THIN yellow glue fillet and spread it with a fingertip as soon as the fin "locks in place", smoothing out any droplets of glue squeezed out from under the fin when it's pressed to the tube. Works great and the glue will dry quickly-- the joint will be dry within an hour or so, and you can do a pair of opposing fins, or all the fins, at one time...

Later! OL JR

I'm wrestling between the additional weight of glue fillets and the strength that they might impart.

I know some people wipe away the excess carpenter glue in fillets, but I would think the more mass
or substance in the creavase, the stronger the joint. Or am I wrong?

Kirk G said:

I'm wrestling between the additional weight of glue fillets and the strength that they might impart.

I know some people wipe away the excess carpenter glue in fillets, but I would think the more mass
or substance in the creavase, the stronger the joint. Or am I wrong?

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I'm sure you've seen what a popped off fin looks like after a hard landing of a LPR.

A casual inspection of the fin generally shows the fillet will still be attached to the fin, not the body tube of the LPR. This is because the glue (white or yellow Elmer's) will readily soak into he bare balsa wood the fin is made outta. Unless you take the time to sand off the glossie covering on the tube, the glue will not soak into the tube.

With a built in failure point such as this, a large fillet is more for looks rather then strength.

If the joint is prepared properly, a fillet will add some strength but mostly helps in smoothing out air flow and reducing drag.

Kirk G said:

I'm wrestling between the additional weight of glue fillets and the strength that they might impart.

I know some people wipe away the excess carpenter glue in fillets, but I would think the more mass
or substance in the creavase, the stronger the joint. Or am I wrong?

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Additional glue just adds additional weight, with very little increase in strength.

Of course if you want to build up the fillets a little for any additional strength that is provided, and to improve the aerodynamics a little bit and the aesthetics, well, that's certainly up to you... the weight is actually very minimal and not really worth worrying about.

The best way to do fillets with yellow wood glue is to do them in several thin layers-- they dry quickly, and without the usual pits, voids, and pinholes that typically afflict larger yellow wood glue fillets, and without the running, dripping, and sagging that can really screw up your build. Like I said, after I do a double-glue joint with yellow wood glue (also works with white glue for builds where the fins are glued to the outside of wraps and you don't want the discoloration of the yellow wood glue) I apply a very thin fillet with additional YWG along either side of the fin and spread it with my fingertip and wipe off any excess that isn't spread into the fillet area or onto the rocket tube or fin surface adjoining the fillet. This merges with any droplets of glue squeezed out from under the fin during the double-glue joint joining process and makes a strong structural fillet.

You can follow this up with another thin application or two of YWG if you want to build up the fillet more, OR you can let it dry, then use Titebond Moulding and Trim Glue (TMTG) to make whatever fillets you want, ALL AT ONCE on ALL the fins, and be done. TMTG is a no run, no sags, no drip formulation of thickened yellow or white glue (strong like yellow, clear when dry like white) that can be applied directly over the YWG fillets and joins with them and can easily be spread with a damp fingertip to the perfect fillet appearance. It doesn't shrink appreciably as it dries, so whatever the "wet fillet" looks like when you finish applying it, is what the "dry fillet" will look like once the glue cures. It CAN be sanded, though it gets gummy if you sand to hard or too fast (like any other YWG or white glue) but there's really NO NEED-- you can smooth it to your hearts content when it's wet and get perfect looking fillets first time, every time, no muss, no fuss.

How strong is a double-glue joint with a TMTG fillet?? How about "stronger than either the paper tube or the balsa fin"... I had a rocket go awry in flight and come down horizontal, impact the ground under thrust on hard ground-- the impact was hard-- hard enough to disintegrate the outer forward 1/4 of the hardened papered fin in the impact, before the forces finally built up enough to rip the fin off the tube-- and then it wasn't the joint that turned loose-- the outer layer or two of the paper tube ripped off the underlying layers.

No sense going for any stronger than that-- if the tube or the wood breaks first, well, what more can you ask of the GLUE JOINT??

Later! OL JR

When did somebody ask for a long winded "how to" on making fillets ?

white/yellow glue will lose about 50%(or more) of its' weight as it dries.
Rex

bradycros said:

I'm sure you've seen what a popped off fin looks like after a hard landing of a LPR.

A casual inspection of the fin generally shows the fillet will still be attached to the fin, not the body tube of the LPR. This is because the glue (white or yellow Elmer's) will readily soak into he bare balsa wood the fin is made outta. Unless you take the time to sand off the glossie covering on the tube, the glue will not soak into the tube.

With a built in failure point such as this, a large fillet is more for looks rather then strength.

If the joint is prepared properly, a fillet will add some strength but mostly helps in smoothing out air flow and reducing drag.

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Thank you.
I wished I had read this before I glued all my fins on the Alien Invader rocket I'm now painting....

blackbrandt said:

I use CA to get a quicker bond when working with epoxy. I put a thick bead of epoxy across the root edge of the fin, except for the very ends. The very ends get a drop of CA. Then, I press the fin on, the CA sets quickly, and the epoxy gives a strong bond.


Matt

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BB, I used your Method today on my Crossfire DX. Great Idea. It worked great.
Thanks for the Tip.