Placing glue inside a body tube

What methods have you guys developed to place glue inside a long body tube to anchor a motor mount or something else. Dropping the glue in drips and hoping it lands where it's desired seems too crude to me. Is there an extension method or something for the glue dispenser? Or maybe a syringe with a long tube?

I often use a 1/8" dowel as an applicator. If the adhesive is viscous enough, this works well.

I have some long Q-tip like things that we got for applying dental goop on pet's teeth. Your pet may love you, but they don't like you putting stuff on their teeth so the goop comes with 8 inch long Q-tips in case they bite. And yes, they do bite. My wife, Six-Fingered Connie, can attest to that.

If it is a regular 18mm low power I just use my finger. I can get up to 3" deep. If using epoxy I put on a nitrile glove.

If it is longer than that I use a stick cut from scrap balsa.

I have some wooden chopsticks from a Japanese restaurant that work well. But really, any long stick. Use something without any sharp edges, round it off if possible for best glue spreading.

Kuririn, what am I looking at here? Just a stick with like 1,000 layers of glue on it?

14" long 1/4" round dowel that has come in handy MANY times for me.
Cheers, tally ho, pip pip.

I epoxied a tongue depressor onto a chopstick.

Oral medicine syringe. Glue a straw on the end of the appropriate length.

If you need a lot of glue, coil one end of a stiff wire into a small spiral, like a spring. Works like a honey dipper, holds a lot of glue. If the glue tends to drip, just slowly twirl the wire as you insert it into the tube. Size of the spiral and length of the wire depends on the rocket.

I've also used small-diameter polyethylene tubing as you would a straw. Suck some glue into the tubing, plug the end of the tubing with your finger, insert into the body tube, release finger pressure to dispense. I've had to tape the tubing to a stiff wire or dowel, as it comes in coils and doesn't like to straighten out.

Best -- Terry

Disposable long plastic pipette

Or drill a hole and inject then patch the hole

I use the blunt end of a bamboo skewer. I put a blob of glue on a card, measure on the stick how deep the glue should go into the tube, place my thumb there and apply the glue at that depth. Once you’ve used the stick a few times, the glue residue builds into a blob that makes putting the glue exactly where it should be even easier.

I thought about this for a while, here's what I came up with that worked pretty darn good the first try.

I grabbed an extra hunk of silicone fuel tubing from my RC Hydro that was laying around doing nothing. It slips over the end of a bottle of Sig Bond.

I took a regular plastic drinking straw and slid that over the silicone tube to make the tube ridigd. I taped the straw to the end of the bottle of Sig Bond.

I used a piece of masking tape to mark the depth needed inside the tube to place the Sig Bond in the correct location.

It works !

Thanks to all for helpful advice that gave me ideas !

Here's the results



Here's the tool

The reason I didn't just use the straw is because it used up too much Sig Bond just traveling down the tube and would then deposit the adhesive in too large of a blob...

Okay, here's my outside the box method for gluing in motor mounts and motor motor blocks for low and mid power.

I am gluing paper to paper, so I use white glue which gives me a long set time. And since these things tend to stay in place for the moment without any glue at all (unlike a fin, which either you have to hold in position or just a jig or something to keep it in place), once you stick it where you want it, it is unlikely to shift with gravity.

For a motor block, I use a used engine casing of appropriate caliber, place it in as far as I want it to go, and mark the side with pencil (don't want to get ink on the rocket tube), and remove.

I stick my standard glue tip in as far as I can go, usually about half an inch, and do an inside ring of glue, rotating the tube.

I stick the motor block in, and quickly and smoothly advance it with the used casing to the appropriate depth/pencil mark, and promptly remove the casing. With WHITE glue I have not had any problems with casing getting stuck. I have never felt the need to rush, but I am not going to go answer a phone call in the middle of the procedure either..

Does this leave a bit of residual glue on the inside of the tubing below the mount? Sure does, but it has never been a problem for me. Would be a BIG problem if I used polyurethane/gorilla glue.

For motor mounts, I do the same thing, except after I get the first centering ring in past the glue ring, I quickly do a second white glue ring along the inside of the tube below the upper ring, then push the motor mount forward to the appropriate position.

This has been my routine for about 10 years now using WHITE GLUE, I have never (knock wood) had an motor block or motor mount lock on me or fail under use, and I haven't had a problem with the residual trace of white glue in the tube that prevented me from easily inserting an engine. I DID have problems with premature "grabbing" or removal of the casing when I tried this with wood glue.

I also have stopped using store bought motor blocks/engine blocks. I cut a ring of same size body tube as my motor mount about 5mm long. I cut a tiny segment out, so it fits perfectly inside the tube. Tiny piece of masking tape to keep it as a ring. That's my motor block. For low and mid power, have yet to have one fail (again, knock wood.)

YMMV

I use the same stick method as many above, usually a bit of balsa scrap. And I have one little trick: I measure from the business end of the stick the depth I want the glue ring and mark the stick there. Then I can dip the stick and insert it into the tube up to the mark and I know I've got my glue where I want it.

BABAR said:

..... Would be a BIG problem if I used polyurethane/gorilla glue.

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FWIW....

I use gorilla glue for all wood pulp derived parts, not white glue... For motor blocks I too use an engine casing but instead of just marking it I put tape around the casing so when it's inserted into the body tube the tape stops the motor casing from going in to far.

Use a 3/16" dowel as the glue applicator, place a ring of glue in the body tube at the correct location, put in the motor block and "slide it home" with the engine casing. Pull out the casing, wipe off any gorilla glue from the engine casing, reinsert the casing and spin the rocket, pull the casing back out, wipe off any gorilla glue, and repeat this process. You end up with a bit of glue lining the inside of the motor mount tube which is a good thing. The internal glue makes the motor casing fit nice and snug and also protects the tube from motor gasses during ejection. Well.. protects it better than a bare cardboard tube would.

Also, once the motor block is in position I always hold the rocket "nose up" so the glue forms a fillet between the body tube and the motor block.

Just keep inserting the casing, holding it so it won't spin, & spin the body tube. The spinning pushes any glue out against the body tube and makes a nice uniform fillet.

JohnCoker said:

I often use a 1/8" dowel as an applicator. If the adhesive is viscous enough, this works well.

Click to expand...

Plus when using a dowel rod, you can put marks on it to gauge the appropriate depth.

lakeroadster said:

I use gorilla glue for all wood pulp derived parts, not white glue... For motor blocks I too use an engine casing but instead of just marking it I put tape around the casing so when it's inserted into the body tube the tape stops the motor casing from going in to far.

Click to expand...

I thought you were using Gorilla *Wood* Glue, not the original polyurethane glue?

neil_w said:

I thought you were using Gorilla *Wood* Glue, not the original polyurethane glue?

Click to expand...

I am...

lakeroadster said:

I am...

Click to expand...

Yeah, BABAR was referring to original Gorilla Glue which is of course totally different from what you're using. For clarity, you should make sure to keep "Wood" in there to avoid confusion.

Ooof that original Gorilla Glue can be really messy! That's the stuff that expands right?

Yup. I suppose there are places in rocket building that it might be useful, but I'm not touching it anywhere near my rockets.

I recall reading that it's good for gluing shot to the inside of plastic nose cones.

neil_w said:

Yeah, BABAR was referring to original Gorilla Glue which is of course totally different from what you're using. For clarity, you should make sure to keep "Wood" in there to avoid confusion.

Click to expand...

I see, said the blind man, as he picked up his hammer and saw. I misinterpreted Babar's text of "polyurethane/gorilla glue" to mean either polyurethane or Gorilla wood glue.

My experience is Gorilla Wood Glue sets up a lot quicker than Elmers white glue.... I learned that the hard way.

lakeroadster said:

FWIW....

I use gorilla glue for all wood pulp derived parts, not white glue

Click to expand...

Hmm, I am not sure we are talking the same gorilla glue. When I think of what I definitely do NOT want to use for an engine block, it is polyurethane glue that foams up as it cures. I think this was the original Gorilla Glue, now Gorilla makes multiple glues. Even the tiniest smidge of foaming glue In the wrong place leaves a big bump or ridge when I dries.

On the other hand, the big deal about using a stick to get glue in the inner workings of the tube presumes that I you have some where you don’t want it, that’s really bad. In my experience with white glue, as long as I use the engine block to shove the vast majority of the glue forward, the trace amounts of white glue left behind haven’t given me any trouble getting a motor in. With the foaming glue, if I leave even a trace i might as well throw the piece away, it is a real PITB to get that stuff off and it is really bulky.

I've read somewhere that white glue when dry is as strong as yellow glue. But, of course it doesn't have the "glue grab" when installing that yellow/wood glue has. So if you don't want the glue to grab, as in installing engine mounts, use white glue. If you do want it to grab, as in attaching fins, use yellow/wood glue.
For locking down nose weight I use an expanding polyurethane foam, but I suppose expanding polyurethane Gorilla glue would work just as well.

In case no one else knows this trick/tool, for each motor size, I glue a 1/4 inch strip of paper around the rear end of an expended motor - when dry it is now a thrust ring positioning tool. Simply apply the glue inside your motor tube using the methods listed above, insert the thrust ring into the motor tube, and push in the positioning tool until it bottoms out. The thrust ring is now placed so exactly 1/4 inch of the motor will stick out the back. Because you can position it quickly, evenly, and accurately, the ring will not "grab" in the wrong position. I have a set of these for each motor size (13mm, 18mm, 24mm short and long).