Bending the front and rear Floor Channel for a 1992 Excella

[Re-Pete]

I'm rebuilding a 1992 Excella. The floor channel that encases the structural sub flooring and marries the chassis frame and shell was to fractured, tattered and dented for my taste so I decided to buy new from odmrv.com. I bought both the straight floor channel and the two floor channel bows for the front and rear.

The rub came when I discovered that the radius of the new "bows" did not match my existing bows. The radius is slightly greater on the new bows than it is on the preexisting bows. I just tried a dry fit by bolting only the new floor channels to my frame and the shell does not have the give front and rear to fit over the new radius along the curves. Believe me, my wife, my adult granddaughter, her fried and I tried to shoehorn it in. It was a No Go.

One person told me they cut relief slots in the new bows in this situation to bend them to fit the shape of the preexisting bows. Does anyone have experience with this or similar, or enough metal working knowledge that can expand on this advice and elaborate so I can feel more comfortable doing this. I'm open to all shares on this.

[PeterH-350LE]

Sorry, I dont have the answer you may be looking for. However, i strongly suggest that you do NOT cut relieve slots in the U-channel, since it will immediately compromise the structural integrity. As you probably witnessed on your old U channel, the points next to frame were either cracked or severely deformed by the constant pounding, accelerated by lack of support of a rotten floor.

Since i have been that "deep" on several trailers short of your "full monty", I was trying to figure out what I would do. My approach would be to make a perfect template of the shell curve and then start by mounting the uchannel on the 2 frames. The curve in question is basically floating until it meets the first outrigger. I would use a Heat gun to try to manipulate the curve to meet my template.
If all else fails, you may have to unzip the first rivet line after the curve.

[DGJackson]

i would suggest looking at Metal Shrinker/Stretcher Set. Harbor Frieght and Eastwood both sell them. Several YouTube videos on tips and uses. Never used one but looks like the right approach.

[Re-Pete]

The bending issue is made so difficult because of the complex shape of this extrusion. I am aware of the shaper - stretcher machines and I've watched several videos of people using them to do some pretty cool bends. Unfortunately, I have not seen anyone bend anything but flat or one sided angled metal and for good reason, it would not fit into the jaws of the machine.

I'm wondering if relief cuts and followed with aluminum welding might be possible?

[BobnGayl]

I am not familiar with the exact construction you are dealing with as I've never taken one of these apart, or even seen a cross section diagram. But maybe I can help anyway. If you are trying to bend an aluminum metal section that isn't flat, i.e; a channel section, a relief cut if what I would do, followed up by a reinforcement plate glued and riveted to the inside of the channel. These plates need to be shaped to fit the curve tightly so as to provide maximum reinforcement. Gluing is also important as the shear load carried by glue is far superior to that provided by spot riveting. However since sometimes glued joints creep over time, the rivets are important as well.

Aluminum typically used in parts such as these isn't overly ductile and doesn't bend well once it's cold hardened following the initial fabrication. (This is why dents normally can't be removed from the skin as they can be from steel used in cars.) I don't know if there is room for the reinforcement, but if not, maybe do a little surface routing work on the floor that goes inside the channel, if in fact it fits inside. As long as the reinforcement bridges the cut by a decent distance (8-12 inches), and is riveted and epoxied in place, the cuts should not be detrimental. If you need to make several, then use a larger plate that spans all of them. I hope this helps. If not, just ignore. Good luck.

[Re-Pete]

BobnGay,
I can picture this. I'm not sure what type of glue you are talking about. I'm familiar with epoxy, but not very experienced. I also watched a video a while back where a guy glued aluminum sheet metal together with a really strong glue, a 3M product I believe, and strength tested it against pop rivets. It did remarkably well. Combining glue and pop rivets would probably work well.
Are you able to elaborate on what type of glue you are thinking of? Also what thickness of aluminum after you thinking of?

[PeterH-350LE]

Pete,

It would help to know how much offset you have to deal with? Is it 1/8" or are you talking 1/2 or more?

[AlinCal]

Is it possible to get the correct part? Seems they sent you an earlier version?
The part description says for narrow body but not all years are the same.

[J. Morgan]

Originally Posted by Re-Pete

The bending issue is made so difficult because of the complex shape of this extrusion. I am aware of the shaper - stretcher machines and I've watched several videos of people using them to do some pretty cool bends. Unfortunately, I have not seen anyone bend anything but flat or one sided angled metal and for good reason, it would not fit into the jaws of the machine.

I'm wondering if relief cuts and followed with aluminum welding might be possible?

I made a replacement u-channel for my 72 using a shrinker/stretcher set.

I made two sheet metal 90 degree angles on my metal brake, and then used a shrinker/stretcher to form them to the right shape and contour, and then welded the two pieces together to form a u-channel.

It worked out pretty well.

[Re-Pete]

Originally Posted by PeterH-Airstreamer

Pete,

It would help to know how much offset you have to deal with? Is it 1/8" or are you talking 1/2 or more?

Peter,
I'm going to say greater than 1/2" and possibly 1" at the widest point.

[Re-Pete]

AlinCal,
It's a good question, but I'm certain it was the correct one. It's listed as being for the narrow body. I picked them up at ODM myself and the parts guy and I had been working together for a few weeks while I was calling in additional items for my order. I love in Virginia Beach, VA so ODM is only about 5 hours away and driving saved me a huge shipping bill. [emoji3]

[Re-Pete]

J. Morgan,
You sound very talented and it seems you have some excellent skills to compliment that. [emoji106][emoji3]
The channel for my unit is a bit more than a U shape. I've attached a couple of pictures pictures from a scrap piece. I'm going to check around tomorrow for a local company that does metal fabrication and see if they can help. But BobnGay has also offered a good idea. Per your welding suggestion, I can do a bit of welding, but I'd probably get someone with real trading to do my welding. I have a Millermatic 140 MIG welder, but I don't have a spool gun and I've never welded aluminum. If you can think of anything more I'm all ears.

[DavidsonOverlander]

Originally Posted by J. Morgan

I made a replacement u-channel for my 72 using a shrinker/stretcher set.

I made two sheet metal 90 degree angles on my metal brake, and then used a shrinker/stretcher to form them to the right shape and contour, and then welded the two pieces together to form a u-channel.

It worked out pretty well.

I did the same for curved roof supports for my Avion Truck Camper, but I pop riveted them together rather than welding. These were installed fore and aft of a new vent.

I agree that the stretcher/shrinker would probably not work on a shape as complex as C-channel.
Ideally you would find a piece with the right curve, but I don't see a problem with making relief cuts in your channel. Consider that you have the outer skin and the inner skin attached to the channel plus the bolts through the floor which all add strength. If you think it needs it you could cut pieces of aluminum curved to fit flat on top of the channel before bolting it through the floor.

[J. Morgan]

Originally Posted by DavidsonOverlander

I did the same for curved roof supports for my Avion Truck Camper, but I pop riveted them together rather than welding. These were installed fore and aft of a new vent.



I agree that the stretcher/shrinker would probably not work on a shape as complex as C-channel.

Ideally you would find a piece with the right curve, but I don't see a problem with making relief cuts in your channel. Consider that you have the outer skin and the inner skin attached to the channel plus the bolts through the floor which all add strength. If you think it needs it you could cut pieces of aluminum curved to fit flat on top of the channel before bolting it through the floor.

After looking at the piece, and reading that the difference is only about a half an inch, I'd probably do relief cuts too.

[Re-Pete]

I should have provided these sooner. Here are some pictures. I've laid the old channel over the new, rear and front to show the differences. I hope this is helpful in showing what I'm dealing with.

My wife brought up a good point. She suggested I call Out of Doors Mart and maker them aware of this problem. These bows are definitely not plug n play ready and it should be explained as so to customers, along with a suggested method to make them fit properly.

[BobnGayl]

I worked in the plastic and composite materials and fabrication business for many years but I haven't rebuilt an Airstream so much of what I say may have zero value. But, maybe not. First, hats of to J Morgan, he certainly has talent beyond anything I can do. I haven't had much luck trying to bend aluminum section materials in past projects which is why I made the relief cut - glue-rivet suggestion I did. Certainly welding is an option - my problem with that is skill, equipment and material properties. Welding aluminum is done in many industries but it's not something a non-expert should attempt IMHO. Aluminum comes in many grades and without knowing exactly what you are dealing with, welding could cause all sorts of problems such as making the parts brittle and subject to early fatigue and failure.

I much prefer the epoxy-rivet approach I mentioned. Just like aluminum and everything else, epoxies come in all sorts of varieties but generally they are the same chemically. The varieties arise from the type and amount of resin, the catalyst used, fillers such as metal powder, etc. These all add or subtract something - for instance, a high proportion of catalyst shortens cure time dramatically, but also may cause a weaker bond. Adding metal fillers (J-B Weld) may make the adhesive stronger, but also can affect adhesion and toughness.

I would suggest you just buy a good slow cure straight 2-part liquid epoxy from a reputable company such as Loctite, Devcon, Bob Smith, etc. It's important to buy a slow cure version (2 hour would be my pick) to ensure you have good mix, good placement, and good clamping (riveting) prior to any cure taking place. Normally slow cure adhesives are unpopular because of fixturing-clamping issues but in your case you have the rivets to take care of that. Whatever you do, don't go with a 5 minute cure or even 15 minute cure option - you have all day since you are riveting the assembly in place, and you want the adhesive to achieve full strength. When an adhesive begins curing immediately, strength can be severely compromised.

Also, make sure your metal surfaces are very clean - any oil or dirt will destroy a good bond. Use a solvent such as MEK if you can get it. Contact cleaner or even carburetor cleaner isn't a bad option either.

Good luck!

[PeterH-350LE]

Originally Posted by Re-Pete

I should have provided these sooner. Here are some pictures. I've laid the old channel over the new, rear and front to show the differences. I hope this is helpful in showing what I'm dealing with.

My wife brought up a good point. She suggested I call Out of Doors Mart and maker them aware of this problem. These bows are definitely not plug n play ready and it should be explained as so to customers, along with a suggested method to make them fit properly.Attachment 346606Attachment 346607Attachment 346608Attachment 346609Attachment 346610Attachment 346611

Thats not aceptable. But I wonder what is wrong with the old one? It does not appear to have a break at the frame area, or does it? Everything else can be bend back in shape. No 2 Airstreams are identical and not all parts are interchangeable .

[Re-Pete]

BobnGayl,
Thanks, very thorough

[Re-Pete]

PeterH,
I didn't highlight the damaged areas so I get your question. There is a lot of fatigue and corrosion present particularly on the bottom of the channel where it rested against the frame and outriggers. There are also missing areas along the outside of the front channel that were cut out for battery boxes that will not be reused. I'm going back with lithium ion batteries. I intend to replace the front aluminum panel and need good channel to rivet to. The front panel of our Excella for not have a single rivet along the bottom that fastened it to the channel. Over the years this caused some collateral damage to the curved aluminum pieces which were left to carry the brunt of the stresses around the fasteners as it traveled.

[PeterH-350LE]

Originally Posted by Re-Pete

PeterH,
I didn't highlight the damaged areas so I get your question. There is a lot of fatigue and corrosion present particularly on the bottom of the channel where it rested against the frame and outriggers. There are also missing areas along the outside of the front channel that were cut out for battery boxes that will not be reused. I'm going back with lithium ion batteries. I intend to replace the front aluminum panel and need good channel to rivet to. The front panel of our Excella for not have a single rivet along the bottom that fastened it to the channel. Over the years this caused some collateral damage to the curved aluminum pieces which were left to carry the brunt of the stresses around the fasteners as it traveled.

Thanks for clarifying, I am familiar with the weakening of the channel due to contact with other metals. The front flat panel appeared to have been riveted to the u channel according to your pictures, i can see the old rivet holes, but may be those were just the rub rail rivets or the panel rivets were sheared off by what you are describing as collateral damage to the curved aluminum piece. This condition is typically called front end separation (versus the widely known rear end separation of the 31' trailers) and can in extreme cases (mostly in 34' early 90's trailers) cause a crack in the skin at ~1pm above the entry door. It has been determined by long time experts that the cause for this is too heavy tow vehicles used along with overrated (stiff) tow bars. The fix is to install a metal strengthening plate between the battery compartments that is riveted to the frame and the flat panel