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Help with Estes Cosmic Interceptor

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vicmeister

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I recently purchased two kits of Estes Cosmic Interceptor, one for a backup of parts etc as this is for my grandson's 4H project. The problem is with the two main body tubes which need connected using a coupler. These tubes (2 inch) and coupler are of a relatively thin wall cardboard, and are made for a pretty tight fit. Unfortunately, when placing the glue either on the inside of the body tube or on the exterior of the coupler it is nearly impossible to insert the coupler into the tube. The glue "grabs" and I cannot twist or push the pieces together. We have sanded the coupler almost to the point of sanding through the wall and will not fit using glue. As for the glue, we have tried Elmer's Contractor's Wood Glue, Titebond II Premium Wood Glue and Titebond III Ultimate Wood Glue. After pretty much ruining the body tubes and coupler of the first kit, we resolved the problem using the parts from the 2nd kit and cutting a 3/32 lit out of the length of the coupler, making it smaller around. Unfortunately, another identical coupler is used in making the motor mount, which also includes some exterior detail. This detail and the required fit makes it inpractical to modify this coupler in the same manner as when connecting the tubes.

I have contacted Estes and their suggestions are a bit impractical, and involves removing one layer of the cardboard from the coupler. I believe this would excessively weaken the tune and motor mount assembly.

Any suggestions would be greatly appreciated - either in the procedure or possibly another glue which would not grab yet would be sufficiently strong.

Thanks
 

samb

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I have successfully used Gorilla polyurethane glue for paper couplers and motor mounts.

Single_Use_Tube-1.png
 

Cabernut

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I second the epoxy. If anything, the epoxy will lubricate the connection at first.

What I do is sand the inside of the body tube end a bit to make sure there aren't and burrs from the tube being factory cut and also to provide an ever-so-slightly larger diameter opening. Sometimes can make a big difference.

For this kit, especially the engine assembly coupler, use epoxy. You could use wood glue, but you have about 1 second before it's locked in.

For what it's worth, I have noticed some of the "red band" Estes couplers can be a hair oversized requiring me to sand off almost all the red to get it to fit.
 

mjennings

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A layer of paper off the OD of the coupler will minimally reduce the strength. (Axial loads will be fine and I would imagine that the CG is close to or aft of the coupler reducing concerns of bending assuming of course it is assembled straight) I'm working on a CI right now and I agree the couplers are a bit snug. How much wood glue are you using and where are you placing it? Given the length of the couplers if you are applying the glue at the lip of BT anything that isn't a time cure is going to grab before you get it fully inserted. I'll have to be extra careful with mine as I'm pre-painting the sub assemblies. Cabernut's suggestion of checking the lip of the tube is a good one also check the coupler side. I had considered making this a mid break or engine eject model but with the coupler fit over time I'm not sure I'm going to pursue that option.
 

jadebox

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The glue "grabs" and I cannot twist or push the pieces together. [...] As for the glue, we have tried Elmer's Contractor's Wood Glue, Titebond II Premium Wood Glue and Titebond III Ultimate Wood Glue.
Wood glues tend to "grab" more than white or school glue. So, white glue is a better choice for gluing couplers into a body tube. I once had wood glue grab on me when installing the fin section in a 5.5" diameter rocket. At my wife's suggestion ("What do you have to lose?"), I fixed the mistake with a big hammer.

You can also help avoid grabbing if you spread glue inside the body tube just short of the distance that the coupler will go into the tube. Don't put glue on the coupler itself. This way, there's no glue on it to grab until it's almost in position.

BTW, here are links to a couple of Cosmic Interceptor "Builds" that might help you with yours:



In the page pointed to by the first link above, Manny mentions having to sand the couplers to fit.

-- Roger
 
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OverTheTop

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Sometimes the wood glue makes the cardboard swell a little. If you have a close fit don't muck around too long once you apply the wood glue or it will get closer.
 

BABAR

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Wood glues tend to "grab" more than white or school glue. So, white glue is a better choice for gluing couplers into a body tube.

-- Roger
+1

Paper to paper or cardboard to cardboard, white glue give you more time to work with and for these materials pretty much just as good a final product. Also dries clear or white, as opposed to the orange yellow of wood glue, also doesn't tend to contract as much, so less likely to cause a wrinkle.

If you have to sand off the outside a bit and are concerned it might weaken the couple, you can use a spar body tube section the length of your coupler, make one cut along the length, roll it up and glue it INSIDE the coupler again with white glue to strengthen the coupler. If you don't have extra body tube around, can probably make due with a toilet paper tube cut to fit and rolled up.
 
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AfterBurners

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I've had the same problem in the past but if you use epoxy you will have more work time. I stopped using wood glue for this type of procedure just for that reason.
 

HHaase

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I use gorilla glue for situations like that, once I got familiar with how it works. A bit different than white or wood glue but goes perfect for motor mounts and couplings if I don't feel like mixin up some epoxy.

-Hans
 
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