Howdy
This is my first post. I've been reading other posts and can't seem to get what I am looking for. Thanks in advance for your help.
I have an old "pop up" trailer. The top/lid on it has essentially met its match with age and the elements. I want to rebuild it and improve on the original design in the process. The trailer does not have any kind of climate control or storage available. Most travel trailers nowadays have some kind of mini a/c-heater on top. There is also room up there for a bike rack and storage during travel.
The lid/top is 121" long, 81" wide and 8" deep. I am trying to determine what structural material to use as the main top support. I am thinking that steel or aluminum square pipe would work best, but I am not sure what size to purchase or an assembly method. The A/C would create a ~100lb static load right in the middle. The bike rack + bikes would be another ~100lb static load on one end (probably the back). The challenge with this, however, is that the load is not exactly static when we will be travelling down the road at 70mph with potential cross winds. So there is some sheering effect I need to take into account in material. The storage area on the front end would be probably 200lbs max (probably less) and would be low profile like the mini-a/c so wind sheer is not as worry some. The storage and bikes would come off the top before it is lifted up to setup for camping. The mini-a/c would stay there all the time. The 4 edge lifting supports are thin walled aluminum channels.
My rough thinking is to use a 1" and 18-20 gauge square tubing assembled in parallel lines on the short 81" width spaced about 1ft apart or so for the length of the lid. I would devise some kind of rectangular hole in the center for the a/c. Storage and bike rack would be a simple eye bolt or other tie down to keep the items in place screwed through the tubing. The ends of the tubing would be secured to a 2x8 or other lumber. The whole thing would be encased in fiberglass cloth w/ resin.
Thoughts? Any guidance would be appreciated.
James
James,
If I am correctly understanding what you are describing, the logical question is can you use the 8" depth? Or must the top fit over some permanent parts in the camper? 30 years ago I had a rudimentary Apache pop up. Mine had an all canvas top and the plastic lid was only for travel. The lid fit down over the folded camper thus had to be hollow. Is your top like this or is there clearance to use the 8" depth for framework?
Timelord
Timelord
Thanks for the question. The 8" is the outside dimension of height. I looked and the inside is 7", so I at least need to have 7" on the inside to fit over the sink and some other things that fold in. I don't have an outside height requirement, so I can build up the lid top, but I do need it to be hollow in that sense. I was thinking about this some more and I forgot to mention that the top (not sides) will be layers. Bottom layer will be plywood (probably 1/4"), then the metal beams and lastly a top later of plywood with the metal tubing essentially sandwiched in between. The shearing effect will be minimized with the plywood and fiberglass. I am also suspecting that I will get support out of the plywood, so the metal tubing will not have to hold everything.
Hope this helps
James
Plywood and lumber and fiberglass will be relatively heavy. Do you know what the top weighs now? You said "edge lifting supports" so I am assuming you have a crank up roof. In that case I think you need to assess the lifting mechanism and supports to estimate what they can lift. I think you will probably want to keep the structure as light as possible because it must lift the AC in addition to itself at a minimum.
Timelord
JW, Could you tell us the brand model and year of your popup? the reason is I have restored 5 or 6 Apaches from the 70's (hard-sided ones) and Have a lot of information here on many others. I was frequently asked to add A/C and equipment racks and things. One thing about pop ups is they were built for the equipment they had and not much else so you have to be careful, Sway at 70 MPH can take you right off the road if the thing isn't loaded properly and you get a blast from a passing truck to start the wave.
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