A Warped Idea

One of the issues with trying to roll my own fiberglass rube to replace the metal in the lower cage to get improved stiffness without a lot more weight is the need to get 20" diameter molds.  Car wheels would be expensive, but assuming that I did not get anything on them (since you wrap a plastic sheet around them before you start glopping on the epoxy), they would be resellable afterwards.  And there are plenty of used, cosmetically challenged but still round 20" wheels out there, I think.

What happens if you take an existing aluminum tube, and add a layer of fiberglass and resin?  The resin alone would dramatically stiffen it, and the fiberglass would make it strong as well.  Or will thermal expansion coefficient differences between the aluminum and fiberglass cause it to crack the fiberglass layer?

What is attractive about this warped idea:

1. No need for 20" molds.

2. It covers over all the existing holes, although the one that are still needed could be recreated by drilling from the inside, or by putting something in them to prevent them from being covered over by the fiberglass.

3. Minimal materials costs, since I don't need to make an entire 20" ID fiberglass tube -- just improve an existing piece of aluminum with what would likely be one layer of fiberglass cloth and resin.  The result would be far stiffer than the current aluminum, and would not add enormous weight.

If this seems strange, there is a long practice in amateur telescope making of epoxying cardboard concrete forms tubing to get the cheapness of Sonotube with the improved moisture resistance and improved looks of fiberglass.  Any thoughts?

If you are wondering about lack of interest in politics and current affairs at the moment: I can only focus like a laser beam on one intense project at a time.  And the overwhelming lack of interest by magazines on this topic that should be interested in my research on the ineffectiveness of background checks for reducing murder rates has left me feeling like the effort in that area is a bit wasted.

UPDATE: I meant to look this up this morning, but a reader's comment pushed me to do so.  Aluminum has a thermal coefficient of expansion of 22.2 x 10^-6 m/m/K; unfilled epoxy is 55, or more than twice as much expansion.  If I understand the units correctly, this means that a meter of aluminum will expand .00000222 meters for every degree Kelvin (or Celsius) of temperature increase.  The normal range of temperatures that this part will be exposed to is about 70 degrees Fahrenheit, or about 40 degrees Celsius; a part that is .0023 meters thick will therefore expand by billionths of a meter, or 0.0000080409288 inches.  Even with repeated cycles -- I am having a hard time imagining this alone would play any significant role in delamination.  There are doubtless other problems behind the delamination problem that commenter below describes.

I am going to experiment with some Coke cans this evening to see how what a layer of fiberglass does to the stiffness of what is universally recognized as a very flexible piece of aluminum.  This is also a remarkably smooth aluminum surface, much less likely to accept epoxy than the tube that I would need to actually turn into an aluminum fiberglass composite.  If it doesn't just turn into a mold for the tube, the combination will give me confidence that my strategy can work.