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Old 05-22-2012, 05:51 PM   #1
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If You were to build a new frame?

Well I have the shell sitting on the ground and the only thing left on the frame is 6 sheets of plywood.
I had to shear off the outrigger bolts fore and aft of the wheel well to remove the plastic wheel wells, with every bolt removed I realize how marginal in strength these frames are. (1975 31 footer rear bath with 5 inch C frame) I hope to salvage the A frame.
My plans were to use 2"x5" .120 tube for the new frame, including cross members. Now I'm questioning my choose in material, so if you were to build a new frame what size tube would you use? Bear in mind every thing from the floor down will be replaced, the only pieces I will reuse are the banana wraps and tanks.
Thought about 2"x6' .125 frame but that would throw the wraps off ?
So how would you go about building a new frame ?
thanks,
Jack
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Old 05-22-2012, 06:07 PM   #2
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The square tubing you speced out will work fine. As Andy of Inland RV has said many times the strength is not in the frame but in the shell. The rear end sags because the attachment to the shell is gone. Just for reference my 81 31ft Excella II has 6"x2" C-channels welded together to form a box beam. With the frame hanging free it drops 1/2" to 3/4" below the shell in the back. I expect yours would hang lower due to the weaker frame members but I am not sure it matters when everything is hooked to the shell properly. If you go to 6" tall beams your will need new wraps. You can buy the plastic corner wraps for the newer trailers and make your own side wraps. Beefing up the outriggers a little might not be a bad idea. Keep in mind you will have to use blind elevator bolts on the beams since you can't get to the back side. The newer trailers use phillips head elevator bolts which I can't find but I did find some with slot heads from McMaster-Carr (mcmaster.com). If money were no object, I would use aluminum channels or even I-beams. Consider steel I-beams, they are a lot stiffer than channel of the same height. The shell makes the Airstreams and airplanes very strong. The distance between the centroid of the structure and the skin is huge. It is the same concept as a pipe. The bigger the diameter of the pipe the stronger it gets. In my opinion, the shell could be much better attached to the frame and floor than it is. Double the number of outriggers and double the number of bolts and put load spreaders below the nuts on the bolts instead of washers.

Perry
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Old 05-22-2012, 07:16 PM   #3
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If I were going to build a frame for ME...

I'd probably look at 10" tall stock. My intrepretation of the original design goals for these trailers were supposed to be "lightweight". Therefore the shell and frame were designed to complement each other allowing the frame to be very minimal. Now days, the cabinets weigh more than the frame and light weight isn't the driving factor that it once was...

Today, the average family 1/2 ton truck can tow more than the best '60/'70's tow vehicle.

Put some 10" high frame rails, big water tanks, basement slides on the sides!
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Old 05-22-2012, 07:42 PM   #4
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I'm with Perry, I also think just going to a slightly larger gauge C would be fine with me.
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Old 05-22-2012, 10:11 PM   #5
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ew frame

I just finished making a complete new frame, it is quite heavier than the stock unit, but that is because of what the future use of the trailer will be...a race car trailer. I'm converting a 30 ft soverign to accept my Bonneville salt flats race car. The trailer is a 68 which is narrower that most but it didn't matter to me because although my race car is 23 feet long it is only three feet wide. I made my frame rails from 2by6 tubing 3/16 thick. Why? Well it's one thing for a human to be walking around inside a parked trailer and quite another to have a 2000 pound race car bouncing up and down over the road.There are angle iron cross braces every 2 feet, diagnal bracing, and I made all my own outriggers. There was more welding than the any other project I've tried before including the race car. The car weighs about the same as all the rotten cabinets that had to be removed, I figure the total unit loaded with car and tools and trailer to be about 6000 to 65000 pounds. You can make your own trailer but be prepared to take up a lot of room for a lot of time and you had better be a good welder.
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Old 05-22-2012, 10:51 PM   #6
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I'm not a nay-sayer, I'd love to have a generator and manly battery bank in my project trailer.

A bunch of years back I've read Andy posting of too stiff of a frame will eat the weak links on the shell - the aluminum eggshell transmits and focuses heave and torsion forces into loose & popped rivets.

True it may be heavied up frame but when it does flex & oscillate the shell gets bucked around instead of everything flowing with slower motions. Increasing the axle rating for toy hauling or cars and running unloaded may become somewhat similar to a TV with high/too stiff rear axle rating.

As long as it's a self-made & maintained project its just something to watch. I think the frame/shell of the AS (older) trailer designs is like a 1950's bamboo fishing rod, everything is good until you ask it do to something different...
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Old 05-22-2012, 11:10 PM   #7
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Thanks for the input guys. Any more idea's before I start cutting metal.
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Old 05-22-2012, 11:47 PM   #8
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Boatdoc built a stainless steel frame and there is an extensive thread about it: http://www.airforums.com/forums/f36/...ame-29294.html . Not that you might want to build a frame like Boatdoc's but there is a lot of good information in that thread.

Tim
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Old 05-23-2012, 03:10 AM   #9
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I just finished making a new frame and i went with 24 gauge steel (4mm) c channel with 18 gauge (3mm) outriggers and crossmembers, i had a shop bend up all the crossmembers and outriggers and made a new a-frame myself. It is definately a stronger frame but it still has flex in it, i think most frames this long will have flex in it unless you went to higher channels or really beefed it up, the frame is still liftable with two people which IMO means it must be under 200kg, for me this was my best option as my trailer will have a commercial kitchen in it. If you want my opinion I think the floor has a lot to do with the strength of these frames and not so much the body as I think there is only two support beams (on the body) which actually go right to the floor in my trailer so this body is held down only by the aluminium c-channel and the wheel tubs!, there are show trailers built that the whole sides open up on them so it would be interesting to see how much strength they are gleaning from there shells ( they definately would have a beefed up frame), of course too highly rated axles will jolt everything apart as there would be no cushioning that makes sense but IMO a stiffer frame should not cause problems as the body would be just sitting on it, that is only my opionion and probably not worth the pixels it's written in !! p.s greta time to have the frame galvanised which was the same price as painting!
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Old 05-23-2012, 05:26 AM   #10
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I would go just slightly heavier to maintain the flexibility and light weight. Then either galvanize or POR-15 the entire thing for rust protection.

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Old 05-23-2012, 05:58 AM   #11
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I would copy an Avion frame.
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Old 05-23-2012, 10:27 AM   #12
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I found 0.125" pre-bent U-channel that I ended up replacing seven rusted or bent outriggers with - I'd meant to only use them on the solid-faced wheel-well outriggers as defense against blow-outs but the temptation to slap them in everywhere needed was too great. I had drooping outriggers that got removed and refit but anything weak was replaced over-built by about 350%.... When/if these get hit it'll tear out chunks of frame rail and snap bolts, prolly bad mojo there.

I fear I've done wrong as the old light outriggers are a good break-away design, they absorb & deflect a bunch of energy without transmitting it further into the structure - witness the twisted & mangled stamped sheet steel that were merrily covered over by new wraps and left to me to cut out to replace! (sorry, no pictures, let me check the scrap pile but I think they got sold to the scrap man to make the #500 minimum on iron last trip)

If I had a more seriously damaged frame to begin with I'd be tempted to simply double-up the number of spars and outriggers and over-build the axle mounting plate cradle; on my trailer there were NO flooring fasteners in the main frame rails, everything is in the spars and outriggers and I've replaced it the same way, but doubling up spars gives a better stitch into the plywood floor than a single row of fasteners.

I'd be tempted to go back-to-back stock thickness frame rail C-channel as "I-beam" aft of the axles to reinforce the main frame rails just to help with the odd Dukes of Hazard style curb jumps or approach ramp grindings somewhen in the future. allowing for the extra flange when welding in the outriggers would eat time but still be easier than retrofitting a stock frame.

What might be really interesting is to find a wide-bodied shell and mate it to a car hauler trailer cut down to match... Got to love the old fashioned slab oak flooring effect
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Old 05-23-2012, 11:06 AM   #13
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Thanks again for the input.
The tire blow out aspect is going to be a bad deal any way you look at it. The major damage will be in the aluminum skin, the long sheets on either side.
I'm not trying to reinvent the wheel, I would like to improve the frame, after all if I copy the old frame to the tee, it should last 37 years.
As far as the car trailers with oak floor, I told my wife a couple of weeks ago, just buy a 40 ft. goose neck trailer and set the shell on the oak floor, make some nice steps off the trailer, you got a place for generator and anything else you need will camping.
That didn't go over real well, I don't think she liked the idea. Then I said how about a long pontoon boat and trailer then we can have an amphibious Airstream, Well that wasn't a good idea either so I am back to building a new frame.
thanks
Jack
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Old 05-23-2012, 12:22 PM   #14
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Jack,

After several years of reading various posts here, if I were to build a new frame, I'd go all- aluminum - or take the end product out to be hot dipped galvenized.

Aluminum would mean wider, thicker channels but that appeals to me too.

The Boatdoc stainless steel frame seems like a permanent solutuon as well.

Let us know what you do.


Sergei
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