The important part about bending aluminum is the temper of the material. The most common aluminum round tube is 6061-t6511. Which is a 60 series alloy with a t6 temper and artificially aged. In a nut shell, it doesn't want to bend. If you anneal it first (heat then quench in water for aluminum). I will bend well but will no longer have the temper which gives aluminum it's strength and rigidity. I've seen some people get away with bending 6061, but I'm sure if you to a microscope to it you would see lots of tears/cracks. 6063-t5 is what tends to be more readily available and can be bent. It IS considered an architectural alloy, but for tube fenders it will be just fine. That's how I made mine and they have held up well. Haven't bounced them off many rocks yet though. The weight savings are awesome, but they will NEVER hold up to rash like steel ones do. Have fun!!! Aluminum is a blast to work with
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