Originally Posted by malconium
On another note did I read your correctly that you are using wood as your inner skin instead of aluminum? If so you might want to re think that. A lot of things have been written here on the forums about the inner aluminum skin being important to the structural integrity.
This is off topic to the original post - but...
I've thought a lot about the interior skin - and read many suggestions that it not be omitted - I certainly can't say I haven't been warned. I understand that there is a structural function to the internal skin.
The material I am using for inner skins is quite structural - baltic birch ply - 1/8" 3 ply with no voids, good wood throughout. My feeling is that this material is strong enough structurally to take the place of the aluminum rather than just be used as an overlay.
I haven't yet weighed the material to see how much it will add or subtract from the overall weight (I think it will add a bit) but I would rather not double the skins and probably more than double that weight.
If indeed the material is up to the task in terms of shearing strength, my concerns are protecting the wood against moisture and keeping the rivets tight after lots of vibration. To this end I have triple coated the backside of the wood with poly and will triple coat the inside as well. I also plan on increasing the number of rivets. On the endcaps (you can see pictures on my thread 1962
22' Safari) I riveted every 2.5 inches, I think I will do the same throughout. I think the rivets are the weak part (they seem to be the part that pops when structural problems happen with the frame at any rate). As far as moisture goes - I see more problems with water getting trapped between an aluminum and wood double skin -- with my single wood skin and the air gap I have in there (between the wood and the foil bubble) things might be able to dry if they do get wet. My spacers should help with the condensation that happens on the ribs - though the wood will do a good job with a thermal break.
When I visited the airstream factory recently I noticed they use very few (very!) internal rivets compared to the number I found in my trailer. I wonder about this...
Last - I am thinking I will be a guinea pig here, try this out, and keep my interior skins until I have a feel that this wasn't a half brained move... I'll report as I get further along.
Thanks for your help re foil bubble methods by the way, I am happy with the technique you described.