Hi, Snide61, I'll hop onto this one, after some prompting from Teardrop-Fucus.
First of all, you will have no trouble towing a tear with your four-banger, if you keep your build as light as possible.
I personally think 3/4 sidewalls and floor are a bit of over-kill. All I know is that my 1/4 lauan is holding up well, may not be the best looking plywood available, but was cheap and could be bought off of the shelf.
I can't answer your fiberglass question, you might want to inquier about that in a PM to Doug Hodder, a member of this forum. He is a whiz with that kind of construction and would be glad to help you out.
Regarding insulation. I have camped in the heights of the local mountains in 40 degree temps with only 1/4" lauan sides and roof and slept very comfortably in my cozy sleeping bag.
Air conditioning. I highly recommend a cheap AC unit, that you can carry in the car and hook it up after you get to the campsite. Many have come up with novel ideas on how to get the air in and out of their rigs, but my AC unit is slid into my tongue box and blows cool air in and up along the roof, through a scoop from the box to the inside of the tear.
I can't give you any advice one way or another about torsion vs leaf-sprung set ups. However, since I am one of the few that think a full-blown steel frame is not necessary, if I were to build another, it would be frame-less with only an angle iron bolted along the sides attached to torsion axles.
The tongue would go full length and attached to the wood flooring supports. A bit unconventional, but since the teardrop body gives you the strength of a solid box, a twisting, bendable, heavy steel frame, in my opinion, is unnecessary. Just my 2 cents, thinking out of the box again.
Now regarding the cutting of the hatch bows, I can tell you what I have done with some success. My "big" woody has bows like you discribed and were cut from 1x12 pine boards. The drawback is that the ends of these types of bows are weaker due to the severe cross grain. To counter this, I doubled them up with similar pine members, cut from straighter grain at the ends, which requires a joint in the middle. Glued together, with router-eased edges, they are solid as a rock. My "little" Stacker TD has bows made of a single layer of 1/2" baltic birch. They're much lighter, but fastening them from the other side of the plywood can be a challenge. I takes a bit of accurate layout, but can be done with some effort. You can see these in my album. The bows in my woody are seen at the URL below. Good luck.
Roly
