Hi Chri5, If you want a sealer/adhesive then Sikaflex is popular.

If you search on ebay you'll find a range of product numbers. 512 is a common one and you can get white pr black to suit where you're going to put it.

I've got to reseal a window frame and I've just ordered 221 in black.

You apply it with a mastic gun and mask up well to keep it tidy

Hi Chri5
Neil is on the ball again sikaflex is great stuff, I have put the cartridge in hot water for a couple of mins before using and found that your not putting to much pressure on the gun and helps to get a good finish also wear some Lycra type gloves as it can be difficult to get of your fingers
Have fun
G

What is the difference between Sikaflex 512 and 221 please Neil

Cheers Neil

It's a good question and I don't have a definite answer....

They are both pretty well descibed the same. I went for 221 as I saw it advertised in black

As said stikaflex is the usual
But if thinking of other makes, what you want is a sealer that doesn't dry, so it stays flexible at all times.
Maybe its worth contacting a motorhome manufacturer/converter and asking them what they use?