On Sunday, April 30, 2017 at 12:34:58 AM UTC-4, wrote:
I have an alluminum "cigar tube" trailer for my Glasflugel Libelle.

Getting primer to bond to heavily oxidized aluminum is a challenge. It may look good for a year and then start to chip.

You did say CHEAP. Two components 1)material cost 2)your time.

Here is a cheap approach:

https://www.google.com/shopping/prod...31fhoCMujw_wcB

It might even plug the leaky rivet holes.