Originally Posted by silver-man
Bart, thanks for the input. What did you use to frame it out with?
I'm in the process of figuring out what replacement water heater to buy, so don't know the size yet. The hole that's there now is a good bit larger than needed for the 10 gal Atwood I took out, so I'm thinking it will be bigger than whatever I put in there.
I used some nice boat framing scraps (vertical grain douglas fir, IIRC); it doesn't need to be fancy though. Something that holds screws well would be a good idea. The water heater is heavy when full of water, and the rear of the trailer can jump up and down nicely when traveling over rough roads, so making sure that the heater is properly supported from underneath should be a priority.
If you can fit a nice flush aluminum patch for the outside, that would look nice and be extra strong. A good wood frame will work well between the inner and outer skins.