How to glue supports inside of tubes?

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HumanPoweredDesigner

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Supposed I buy some square metal tubing for structural use, and I want to epoxy some square metal struts (walls) inside it every 8 inches. How could that be done without all the glue getting rubbed off before the piece is slid to the desired location? Would I just have to rub lots of glue in there and slide them in fast before it dries? Or do they have heat activated glue I could put in there wet and then heat once everything is in place?

Small plywood plugs would probably be easier to manipulate.
 

lr27

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Nov 3, 2007
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Try not to have important epoxy to metal joints. Especially where you can't get at them easily. To epoxy metal reliably, everything I've read seems to say that you have to have really good surface prep and really good process control. If it was ok just to insert the pieces and hold them in place, perhaps you could space them with blocks of foam of some kind.
 

litespeed

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Go a stronger tube and forget added pain and uncertainty of internal bracing.
 

drake

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Dec 23, 2007
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Not sure what you are building but maybe using 2 C channels and put nut plates to screw reinforcements in so they can be removed or just rivit in place and then rivit the 2 channels together to make square tube. Many different possibilities.
 

Lucrum

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Canton, GA
On a somewhat related note.
If I have a round hollow tube (not metal BTW) and bond a smaller tube, whose OD equals the larger tubes ID, inside of it. And I know the torque being applied to the tube.
Is it correct that the stress on the bond joint will be shear?
And with a given adhesive, is there a relatively easy method for me to calculate the necessary joint area to handle the torque/shear?
Any equations or URL's to existing threads on the subject much appreciated.
 

vortilon

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Jul 7, 2009
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Marana AZ USA
You are thinking like an engineer trying to build something that cannot be done. Heat would be the only way to obtain the needed viscosity to flow where needed but even that has it's risks. Forget it and go to next gauge wall thickness. Now steel tubing has been sucessfully inserted with channels and rossette welded that is an excepted method. I imagine aluminum could be dip brazed together but that is outside my envelope.
 
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