Most tapes on offer are under 10mm wide which sounds too narrow?.
Also, how far does a 300ml tube of Sikaflex 512 go?, my caravan is about 20' long, and it sounds like I would need a lot of 300ml tubes to replace an awning rail!.
Thats what I would use if I was using mastic tape. I helped a mate do his awning rail yesterday, we had both but used non-silicone sealant. If I did mine, I'd use the sealant again. It made a nice tidy job, I'd be far more confident of the seal.
I guess you would need 3 or 4 tubes, depending how liberal you are with it. We used 1 1/2 tubes to do half the rail.We put it on liberally as they were only £2.95 each. Just wipe off the excess which squeezes out, and this gives a nicely filled gap (and a better seal)
the www.thecaravanshop.co.uk does mastic on a roll. I used it for the awning rail and all other rails. filled the screw holes in the awning rail with sikaflex put on the roll masic, then ran a bead of silaflex along either side of the roll mastic then fixed it back into place. Worked for me
I have just re-sealed half of my awning rail,it is a 15ft van and I used 1 and a half tubes of sikaflex,the rail is about 15mm wide and i did not skimp,