Author Topic: options available for joining Aluminium tube?  (Read 10056 times)

Offline RipSlider

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options available for joining Aluminium tube?
« on: June 21, 2009, 04:08:04 AM »
Hello folks.

i was wondering what options I have for joining aluminium tube together? I am thinking of a space frame and some metal widgets which would form the body of a fast model boat, and Ali tube would seem like a good proposition as far as weight savings go.

However, that brings with it the ever present issue of how to actually join the metal together.

It would seem I have - or to put it more accurately - that I can *think* of - the following methods available:

1- screw/bolt etc. strong I guess, but a pain in the backside to do on an entire frame.

2- weld - would be very strong, and can borrow the right kit, but supposedly a very skilled task.
2b- weld and pay for it - would be strong and well made, but defeats the "I made this boat myself" concept....

3- that "aluminium solder" stuff - this seems sort of OK to use, but I have no idea how strong it is, and only seems to make fillet joins, does not seem to wick into joints.

I guess my other options are something more exotic - plasma welding etc - ut that would also have to be paid for - or to use a different metal.

Were I to use steel, how would I measure - or read about - the difference in wall thickness and strength. For example "22swg steel tube is about as strong as 18swg ali tube"...

Any other thoughts/materials/joining idea's? Anyone use the "aluminium solder" in high stress enviroments?

Many thanks indeed.


Offline John Hill

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Re: options available for joining Aluminium tube?
« Reply #1 on: June 21, 2009, 05:12:12 AM »
Possibly a daft idea but what about drill holes and 'sew' it with stainless wire then lock the joints with the 'solder stuff'?
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Offline Brass_Machine

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Re: options available for joining Aluminium tube?
« Reply #2 on: June 21, 2009, 09:40:08 AM »
I have used the aluminum solder a few times. Takes a little practice to use at first, though it works fairly well.

Video link of the demo. I think it should suffice for a model boat frame.

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Offline Bernd

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Re: options available for joining Aluminium tube?
« Reply #3 on: June 21, 2009, 03:56:59 PM »

Mechanical fasterners in aluminum with what you want to do, I would say that they may loosen up after a while.

As Eric, I have tried the aluminum solder. I couldn't get it to work very well for me.

TIG welding is about the best option for aluminum joining. Using steel tubing would make the boat extra heavy.

Also I'm still trying to picture how you keep the fame separete from the hull. Got any pics of a model or real boat with this type of system? Or are we at a language barrier here again on the topic being disscused?

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Offline SPiN Racing

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Re: options available for joining Aluminium tube?
« Reply #4 on: June 21, 2009, 04:12:50 PM »
I THINK.... you could braze it with a torch.
Im not sure on the method only cause I have little experience brazing.. but I know the race shop brazes all sorts of thigns together on some of the older race frames they get restore jobs on.
But I think we would need a better expert opinion on that.  Brom what I have seen, brazing is very much like soldering. Just a lot hotter.

I believe hey make rods for brazing aluminum...
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Re: options available for joining Aluminium tube?
« Reply #5 on: June 21, 2009, 06:32:36 PM »
Hi Steve,

I am not up to date with joining metals with heat (except for a little silver soldering), but I was well up to speed on strengthening model boat hulls to take the stresses of sailing.

We used to use carbon fibre rod, available from good model shops or fishing tackle shops, and bond it with resin and glass tissue along the areas that require strengthening. I think you can even get tube nowadays in very small diameters.

In conjuction with a friend (sadly gone elsewhere), we used to produce for other club members, the lightest glass hulls you could imagine, mainly scale MTB hulls, just one layer of chopped mat thick plus gel coat in most places. Just a few inches of CF rod bonded down the sharp pointy bit at the front would almost make the hull strong enough to chop wood with. Do that in all your problem areas, and not only do you keep the weight down, you make an immensely strong and rigid hull. You can (or used to be able to) get the rod down to 1mm diameter, so you could bend and bond it along almost any internal chine line. Or you could bond it diagonally in a regular pattern to flat panels to make them super rigid.

Just maybe another cure for your problem.