Custom Frame - 1969 Sovereign 31'

[boger]

Hello all - first ever post here.

I've been wanting to renovate an old Airstream for a while now, and ended up finding one nearby last fall, a 1969 31' Sovereign. The shell is in great shape, everything else....not so much. But that's okay, because my plan all along is that I want to build a whole new Airstream from the ground up, especially when it comes to the frame.

I am a mechanical engineer by education, but I now manage a metal fabrication company and am a certified welder (and working towards certified welding inspector later this year). My Airstream, like most of the era and size, has pretty severe back end rotting of the floor, and almost assuredly, the frame as well. My company specializes in heavy, structural steel fabrication, and we galvanize over a million pounds of steel every year. Therefore, I am looking forward to (hopefully) custom building a new, beefy frame and getting it galvanized, as I have yet to find anyone out there that has successfully accomplished this. Galvanizing is the best protection for this type of application, and I am looking forward to sharing my experience doing this so that hopefully others can learn more about the process and gain some ideas for their project(s).

Right now, I am in the middle of the demo process, having torn out all the furniture, carpet, etc but not yet the interior skins, windows, or roof mounted appliances. My plan is to hopefully accomplish the rest of the demo and shell lift off this summer, followed by a detailed frame design and fab this fall (I reserve the right to be waaaay too optimistic in this timeline, FYI).

The reason for the post this far in advance is because I would like to get feedback from those of you out there that have been through this type of frame build so I can be prepared. As of right now, my plan is to use at least 5" x 3" x 3/16" HSS (rect. tube) for the main structural members, with every inch of my being pushing me towards using 1/4" wall thickness for added rigidity. I don't plan to go less than 1/8" thick bent plate or C-channel for the crossmembers and outriggers, which I plan to custom cut and bend all new parts. In short, I plan to go heavy on this frame, mainly because my response to most problems is, "Build it bigger/stronger." Yes, I have read in many threads that Airstreams are monocoque shells designed to hold up the frame and that too much rigidity can shear off rivets and bolts. However, I am yet to "see" this in pictures and experience. So, if you have good experience in this field, I would love to hear your story and advice.

If you have other out-of-the-box or fun ideas for the frame that you've kicked around before, I would love to hear it. I've read a few suggestions to fabricate a metal strip that follows the outline of the shell and sits on top of the outriggers in order to help with support and water intrusion, and I thought that was an interesting idea I may pursue. I am versed in 3d modeling and have heavy equipment and CNC plasma cutting at my disposal, so right now is the time for interesting ideas.

After fabrication, I will plan to do some detailed posts about galvanizing the frame and why I think more people should consider it, based on their location and budget.

Looking forward to sharing my progress with you all and getting your insight.

Thanks,
Jared

[Foiled Again]

Jared, just for snickers and giggles look at vintage AVION trailers. 8 inch I beam frames. Get a paper cup to contain your drool.

[ROBERT CROSS]

Watching with interest...👍

Consider a nice final silver power coat. Might make it ALL silver.🤩

Bob
🇺🇸

The stock rusty spare wheel...

[jeftamm]

Extremely interested in this string. Surprised my wife with a 1972 Tradewind Land Yacht. Gutted it and removed what was left of the flooring. It needs a new frame. I have a 110 volt wire feed welder and can melt metal together. Not that confident in my welding though for something as important as the frame. Considering upgrading to a 220 volt welder if I proceed in building the frame on my own. Was thinking the same regarding beefing up everything. Looking forward to responses.

[A W Warn]

I'm interested also. So Ill be tagging along to watch. Lots of pictures please!

My background is commercial construction. As you know that goes along with a lot of structural steel fabrication. I'm not a certified welder, but I have burned a lot of rods and wire.

I've considered custom fabricating open web trusses for cross members to give more options for running things through the floor frame, and to get some extra depth in the belly for larger tanks and/or additional insulation.

Looking forward to seeing your progress!

Welcome to the AirForums!

[boger]

Thanks all - I'll be sure to post pictures as I discover the condition of the frame and design a new one. Planning to use 3D software at this time, so should be able to share a lot of design aspects and get feedback. Just be patient with me

Foiled - If it wasn't for the banana wraps keeping me at 5 inches and that little thing called weight, I'd be right there with an 8 inch frame!

jeftamm - I don't have a lot of experience with the 110v welders, other than having used ours to do some TIG. I know they've come a long way, but I'm not sure they'll get the penetration you want for the thick parts of your frame. Either way, upgrading to 220v won't be a bad choice.

One of the biggest concerns I have when I see videos of people welding Airstream frames online is that I see a lot of vertical position welds, which is difficult to do correctly and requires the right filler metal. I definitely understand why people do it, as it is very difficult to rotate the entire frame onto it's side. When I get to that point, I may attempt to rotate the frame to weld those positions flat, or at least offer some advice for welding in the vertical position. The welds might look good, but getting the proper penetration is the important part.

[CAVU]

Originally Posted by boger

Hello all - first ever post here.



I've been wanting to renovate an old Airstream for a while now, and ended up finding one nearby last fall, a 1969 31' Sovereign. The shell is in great shape, everything else....not so much. But that's okay, because my plan all along is that I want to build a whole new Airstream from the ground up, especially when it comes to the frame.



I am a mechanical engineer by education, but I now manage a metal fabrication company and am a certified welder (and working towards certified welding inspector later this year). My Airstream, like most of the era and size, has pretty severe back end rotting of the floor, and almost assuredly, the frame as well. My company specializes in heavy, structural steel fabrication, and we galvanize over a million pounds of steel every year. Therefore, I am looking forward to (hopefully) custom building a new, beefy frame and getting it galvanized, as I have yet to find anyone out there that has successfully accomplished this. Galvanizing is the best protection for this type of application, and I am looking forward to sharing my experience doing this so that hopefully others can learn more about the process and gain some ideas for their project(s).



Right now, I am in the middle of the demo process, having torn out all the furniture, carpet, etc but not yet the interior skins, windows, or roof mounted appliances. My plan is to hopefully accomplish the rest of the demo and shell lift off this summer, followed by a detailed frame design and fab this fall (I reserve the right to be waaaay too optimistic in this timeline, FYI).



The reason for the post this far in advance is because I would like to get feedback from those of you out there that have been through this type of frame build so I can be prepared. As of right now, my plan is to use at least 5" x 3" x 3/16" HSS (rect. tube) for the main structural members, with every inch of my being pushing me towards using 1/4" wall thickness for added rigidity. I don't plan to go less than 1/8" thick bent plate or C-channel for the crossmembers and outriggers, which I plan to custom cut and bend all new parts. In short, I plan to go heavy on this frame, mainly because my response to most problems is, "Build it bigger/stronger." Yes, I have read in many threads that Airstreams are monocoque shells designed to hold up the frame and that too much rigidity can shear off rivets and bolts. However, I am yet to "see" this in pictures and experience. So, if you have good experience in this field, I would love to hear your story and advice.



If you have other out-of-the-box or fun ideas for the frame that you've kicked around before, I would love to hear it. I've read a few suggestions to fabricate a metal strip that follows the outline of the shell and sits on top of the outriggers in order to help with support and water intrusion, and I thought that was an interesting idea I may pursue. I am versed in 3d modeling and have heavy equipment and CNC plasma cutting at my disposal, so right now is the time for interesting ideas.



After fabrication, I will plan to do some detailed posts about galvanizing the frame and why I think more people should consider it, based on their location and budget.



Looking forward to sharing my progress with you all and getting your insight.



Thanks,

Jared

If you haven’t found and read the multi year journal by Truckasauras as he attempts a complete ground up rebuild...you should. The man does amazing work.

Search for Truckasauras forum name.

[CAVU]

Per the Truckasauras rebuild comment above, it's easier to find his project by name. Search for "Super Sized Sixty Sovereign"

[boger]

After a long winter hiatus, things have thawed out here enough to get back at the trailer. I've had the interior completely demo'ed already and am ready to start in on removing the belly pan and detaching the shell from the frame.

I started removing the exterior trim on the outside of the C-channel, and I was surprised to find that on the sides of the trailer, the exterior skins extend all the way under the frame and overlap the belly pan. Is this normal? I was thinking the trim was hiding a seam and there was a curved piece that would be removed. My concern is that if this is one continuous piece, I will not be able to set the removed shell on the ground after the frame is removed. The other issue is that the Carefree Awning bolts through the trim, so it appears I will need to remove the awning. I haven't yet researched that, but if someone has some quick advice on that task, I'd be all ears.

While inspecting the belly pan and making plans for removal, I noticed the belly pan sheets run nearly the entire length of the trailer including under the axles, with the seam running lengthwise down the middle of the trailer. I was a bit surprised by this, and will need to do some research on how to best remove the pan sheets. I don't mind replacing the pan with new sheets if needed - I'm more worried about the logistics of just getting the current pan out. Needless to say, the grinder will be within arms reach during the removal.... Worth noting - I was able to peek under the belly pan in a few areas and see the insulation under the floor is spray foam. Is this original? That would make for another surprise if so.

See pictures. Hoping to spend the day this Saturday making some progress!

Jared

[Disco Stu]

G'day Jared. Our 1970 clad wrapped underneath to form the edge of the belly pan too, and ours had glass insulation. We just left the shell hanging in the roof of the workshop while waiting for the chassis work.
We galvanised the original chassis and were very happy with the result, even though we had to straighten it up a bit due to warping from the big dip.
Good luck with the resto!
Stu

[boger]

Stu - thanks for the response. Sounds like we had very similar situations in year of trailer and wanting to get the frame galvanized. I will come up with a system to support the shell instead of setting it on the ground.

Your frame looks great! I have scoured the message boards looking for others that have gone with galvanizing and hadn't had any luck. I am going to build a sturdier frame than the original, so I'm crossing my fingers I won't have the warping issues you speak of.

Thanks again,
Jared

[boger]

Made some progress this weekend.

First, I had to remove the awning from the trailer, as it was in the way of the lower exterior trim. I had to cut the awning fabric to release the energy in the torsion spring. My nearby oscillating fan did not survive to read this post.

After that, it was pretty straightforward to remove the banana wraps at the corners and the exterior trim. My side panels extend down and under the belly pan, so I drilled the rivets out there as well.

After that, I did a lot of head scratching. Most threads I've read would say it's time to remove the belly pan. Even as a semi-young, halfway-mobile individual, I was looking for excuses not to roll under a 5000 lb trailer and drop a 30 foot sheet of aluminum and 3000 mice turds into my face/fogged up safety glasses (such a wuss). After taking stock of the situation, I can't see any good reason not to wait to remove the belly pan until I pull the shell and drive the frame out. I will then be able to get the whole frame assy up on supports and either flip the frame or remove the belly pan with much more clearance underneath. I am planning to do some measurements and layout ideas before pulling the shell, and will be able to access the roof after pulling the shell (it will sit on rigid supports). If you think I'm missing something, now is a great time to let me know .

I am planning to spend a few weeks doing some detailed planning (interior layouts and subfloor measurements, furnace ducting, new holding tank locations and sizing) before hopefully pulling the shell sometime before June 1st. Using my oscillating tool, I test cut two of the bolts holding the bottom shell channel to the subfloor, and I'm happy to say they cut like butter. The 'Amazon Recommended' blades will go fast, but it still looks like the best method without having to go medieval with the grinder.

I'll try to post updates along the way. (Don't wait up)

Jared

[Disco Stu]

G'day Jared, Since we were replacing the floor anyway, I just chopped the floor out and jumped on the exposed belly pan from above. Insulation, belly pan, acorns and mouse nards could then be cleaned up after the TW was rolled away. I didn't bother keeping the floor to trace a new one, just dropped the body back on and made patterns. When I rebuilt our '51 Clipper chassis I did trace the floor though.
Good luck!
Stu

[57Vintage]

I'll add a couple suggestions to your frame design. I added a 1.5X1.5 steel perimeter to the frame for the shell to bolt to. It's welded on top to the frame rails/outriggers. I wanted the plywood subfloor removed from the shell-U channel-subfloor-frame sandwich. My subfloor sits inside the perimeter tube.



I also built floor patterns before removing the shell so I could replicate the footprint of the U channel for building the perimeter frame. I also drilled 1/4" holes in the patterns at each corner through the frame rails to make sure I duplicated position once the shell was off. The end patterns are odd lengths (front to rear) but the middle ones are all 48" front to rear so I could use them for patterns to cut the subfloor plywood and maintain the factory edges of the plywood. Layout of crossmembers were changed to match this so the subfloor joints (side to side) always are on a crossmember (replaced with 4X2 rectangular tubing). This can get complex so that tanks (fresh, grey, black) all fit also.



Last idea is not about the frame, but requires work on the frame to complete. I added conduit to the outriggers to take the bulk of the wiring away from the interior. (My outriggers are solid, Yours may have oval openings.) Obviously wiring in a 58 is minimal. Adding modern mechanicals adds a lot, plus I didn't want to daisy chain much electronically. We rebuilt/refinished the original interior panels/cabinets so I didn't want to cut a lot of access for wiring. Enough mods would occur with adding multiple tanks and plumbing. I used 1" pvc, recommend you go to 1.5" or 2". I could have used more space.



The large junction box is where most of the wiring runs to (first conduit photo). I hid most of the controls were the old panel heater was. Kept the face panel to hide it all.

[boger]

Stu/Harold - thank you guys for paying me a visit and the quick insights. Both of your threads look to be chock full of the type of information I am looking for for my project, and I will be reading them in short order. Based on your advice, I'm thinking I will get floor templates before pulling the shell. I might try to put them into my 3D modeling software that I use for work, so I can visually match them up with my frame design.

Harold -

I had considered that same idea about a perimeter piece of steel to rest the shell on, but had not found someone that had done it before. I'll read more about the details in your thread, but as of right now I'm leaning towards doing this.

Furthermore, you and I are on the same page in terms of frame design. I'm planning 5 x 3 x 1/4" rect. tube right now for the main members. Moving crossmembers is also in my future as I was going to make custom tanks like you too. One of the questions rolling around in my head, however, is how to handle furnace ducts under the floor to keep the tanks warm. I won't likely do much cold weather camping in the near future, but I like the idea of heat to the tanks in some fashion, both for resale down the road and change in lifestyle if we do more cold weather camping later in life. I see your design does not have heat below the floor - did you consider it, and were there any reasons you chose not to? I'm still torn on what I want to do on that subject, which will affect my tank and electrical design below the floor.

Jared

[57Vintage]

I'm not familiar with the underfloor furnace ducts, so I can't help you there. I know there are also electrical heating pads that can be placed with the tanks as an alternative. Hopefully someone will step up and help you there.

Since I'm in the NW I don't have your winters (familiar with them, grew up in Minnesota, nine months of winter, three months of bad sledding ). I not as concerned with cold weather camping. There is so much plumbing in my unit that insulating under the floor seemed futile. If I was going to insulate down there I'd definitely go for rigid insulation. The belly is going to get moisture one way or another.

Clarification: I didn't make custom tanks. I used ones from Vintage Trailer Supply. Keep in mind my stock frame rails are only 4X2 so that limits what fits. You shouldn't have any problems finding stock units considering your frame rail size.

I would reconsider your 1/4" wall thickness. That's a lot of weight. I made my perimeter frame with 1.5X1.5X.125. In hindsight I wish I had used a thinner wall tubing. Considering the shell is only a few hundred pounds and its designed to 'flex' I didn't really need that much rigidity. My main goal was to get the subfloor out of the sandwich.

Looking forward to watch your progress. I'd suggest another thread by Truckasaurus. He built a new frame so you might find his take of benefit.

https://www.airforums.com/forums/f36...ign-84829.html

[boger]

Been a while since my last post. Project was moving pretty slowly but is starting to pick up steam. I removed the shell a couple months ago (for some reason, I only decide to work on this trailer when it is below 0 degrees in Iowa). I did the shell-off completely solo in the span of two days, which includes building the inner bracing. I used perfectly sized 24’ aluminum beams we had laying around at the shop to support all the 2x4 braces in one plane, and then used a bottle jack at four jacking locations to raise the shell. I raised each corner 1 ½” at a time until the trailer was approx 2 feet off the trailer deck and then transferred the weight of the shell to some wood structures I built next to the trailer before driving the frame out.

Last weekend I got around to stripping the frame and removing the subfloor. The corners and edges were pretty bad, and the back of the trailer subfloor had turned to dust. However, it still took a circular saw, big crowbar, and lots of sweat to take the floor out in sections. Under the floor, I found that the entire belly had been spray foamed. Someone correct me if I am wrong, but I assumed that spray foam was not done in 1969, so someone must have done this later. The spray foam came out about as well as you can imagine, but the good news is that it protected the frame from the same fate as the subfloor, as there are only a few outriggers and the black tank support angles that really need any work done to them. Once I am finished building and installing the new frame, I will likely post the existing frame for sale, in case anyone is looking for an original 1969 frame to take home.

Now I am in hardcore research and planning mode for my next steps, which I hope will proceed faster than the previous steps. I have also decided to move forward with converting this trailer to a mid-bath layout from the original rear bath. There are a number of reasons I want to go this route, both from a structural and convenience standpoint. However, it means more complexity to plan for….

Next step is new frame design. I need a few more dimensions from the old trailer, and then I will layout the new frame in 3D so I can picture everything before I fabricate it. Will still plan to go with 5x3x1/4 tubes for the main rails and C5 x 6.7 channel for supports. I will get the frame hot dip galvanized after that, and I will plan to share some drawings when I get them done.

I am also knee deep in deciding on new running gear and holding tanks. Looking at #11 6000 lbs dexter axles, with shocks, and will add a lift of 1-3 inches (height TBD). Waiting on quote to come back from Dexter, but have not yet decided between electric drum brakes or disc brakes yet - I would welcome feedback! I love the idea of disc, but the extra cost holds me back since we will not use the trailer quite as much as others on this forum.

For holding tanks, I plan to add a gray tank in addition to the black tank and locate them just aft of the axles, to better distribute weight. I also plan to put the fresh tank below the floor and move that just forward of the axles, for the same reason. In order to accommodate larger tanks, I am planning to use 8” deep crossmembers in those areas - and since the axles sit 3” below the frame anyways, I won’t be sacrificing much true ground clearance. All tanks are planned to have heating ducts incorporated to keep them from freezing. Black and Grey tanks will empty streetside just aft of the wheels. I designed custom tanks, but the quotes I received from three different roto mold companies were all in the thousands of dollars (due to custom mold), so I scrapped that plan and will find the best off-the-shelf one possible. So far, Class A Customs seems to have the best prices and closest sizes to what I want (appears to be in the $100-$200 range for each tank).

More info and questions to come!

Jared

[57Vintage]

I would suggest a review of doing electric brakes. You're adding a lot of weight, over the original, with your new frame. If your dexter torsion axles have a #42 spindle you can go to a Kodiak disc brake kit for a 13" vented rotor.

https://www.etrailer.com/dept-pg-Tra..._lbs_Axle.aspx

It requires a 16" or larger wheel.

Keep in mind I did my conversion with a regular dexter tube axle not a torsion axle so you need to confirm the Kodiak parts will fit correctly on a torsion axle.

I also recommend looking at TusconRV's brake actuator. It works through your OBD port so it receives more input than most add on systems.

https://tusonrvbrakes.com/

My thread discussion on the brake conversion is post #102.

https://www.airforums.com/forums/f97...-172124-6.html

[boger]

Good point on the added extra weight. Still waiting on the quote to come back but I'm heavily leaning disc brakes at this moment. There's not a ton of room in that wheel well though, so I'll probably try to keep to a 15" wheel with a 12" rotor.

I actually came across a different thread of you discussing the Tuson systems and have added that to my short list of options to consider. In your experience, would the Tuson brake actuator work ok with my inboard trailer brake controller (2016 Ford F150)?

Thanks!

[57Vintage]

No idea how the Tucson unit functions with built-in brake units. I have an O8 F150 Limited no trailer brake system, suggest you contact TucsonRV and see what they say. I know there are other forum members using the Tucson units so hopefully they can give you some feedback.

A lot of people switch to the 16" wheel and tire so I think you'll find you have plenty of room. Especially if you do the lift kit.