Teardrop frame for saltwater environment

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Teardrop frame for saltwater environment

Postby kayakevan » Thu Dec 08, 2022 10:15 am

I am working on building a teardrop and I am going to weld the frame myself. I've been digging around the internet and the common material for the frame seems to be square tubing, but I also come across people trying to figure out how to stop their frames from rusting out from the inside out so I'd like to avoid that. I live in Virginia Beach, and I will be using this camper extensively on the Outer Banks in NC so salt spray and salt air will be a common occurrence. I'm leaning towards using c-channel for the entire frame so that I can prevent rust but it seems to be less common, so I haven't been able to find as many frame designs.

A few questions.

1. Am I overthinking the rust issue for the square tube frame? Could I weld the tube ends closed to prevent the rust issue? I know that condensation can form inside the tube so could I put some kind of oil inside the tube during the welding process to prevent future rust?

2. Does anyone have a basic design for building a trailer with c-channel? I've found tons of designs for square tube but haven't been able to find much for c-channel.

3. I was thinking I would use 2x3x3/16" c-channel for the frame. I'm pretty sure that that is overkill, but I'd rather have a solid base and cut weight elsewhere on the camper.
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Re: Teardrop frame for saltwater environment

Postby Ottsville » Thu Dec 08, 2022 12:14 pm

I would lean towards C channel regardless of your concerns regarding saltwater and you can always build your frame and have it galvanized. There's got to be a place to get it dipped in your area, if not, there's one in Ashland
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Re: Teardrop frame for saltwater environment

Postby tony.latham » Thu Dec 08, 2022 2:01 pm

Do what the aviation industry does. Weld it closed, drill a hole and put some linseed oil in and weld it shut.


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Re: Teardrop frame for saltwater environment

Postby kayakevan » Thu Dec 08, 2022 3:52 pm

If I go with the C channel do I need to close the c in the area where the axle gets mounted? I'm just going to use a standard spring axle and I'll have the spring hangers welded to a buffer piece of metal to try to spread the stress from the springs. So should I weld that c closed over the entire length of the buffer or would it be better to just put a cross member where each end of the spring mount?
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Re: Teardrop frame for saltwater environment

Postby philpom » Thu Dec 08, 2022 7:07 pm

kayakevan wrote:If I go with the C channel do I need to close the c in the area where the axle gets mounted? I'm just going to use a standard spring axle and I'll have the spring hangers welded to a buffer piece of metal to try to spread the stress from the springs. So should I weld that c closed over the entire length of the buffer or would it be better to just put a cross member where each end of the spring mount?


I would weld a piece of 1/4" thick 3" wide angle along the section of C channel where the axle mounts, maybe 24" long or about the length of your springs in full expansion along the bottom side then weld the spring hangers on that. The open side of the C will face inward so place the vertical side of the angle on the inside also so the spring will ride towards the outside. Then 1 cross member in front and behind it.

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Re: Teardrop frame for saltwater environment

Postby KCStudly » Wed Jan 04, 2023 1:26 pm

C is very commonly used in commercial trailers. It is stronger and cheaper by weight than box if properly braced (by typical xmbrs). I think most home builders just avoid it because fitting the X-section profile takes a bit more work at joints. I would just weld a piece of similar thickness to the C web across the toes (tips of the C flanges) to box the section over the axle. No need to close the ends. In fact, if galvanizing (highly recommended for steel fabrication in salt environment) you can't have any closed areas... I'm told by a reliable source who often has items plated that enclosed volumes are dangerous to the plater during the plating process.
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Re: Teardrop frame for saltwater environment

Postby kayakevan » Thu Jan 26, 2023 6:06 pm

I'm looking at using 3 x 4.1 lb (3 X 1.41 X .170) c channel for the outside of the frame as well as the cross members and then 3x3x3/16 tongue tube. I also plan on adding angle braces to the tongue tube using the same c channel as the frame. Looking at the harbor freight trailer this seems like it's probably even overkill, but does anyone see any issue with these materials?
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Re: Teardrop frame for saltwater environment

Postby Squigie » Thu Jan 26, 2023 9:58 pm

C-channel is the easiest answer, and a quick rattle through my brain seems like your materials would do the job.

But, for an anecdote:

In 2016, I built a porch support structure out of 1x1" and 2x2" steel square tube, both .120" wall.
Certain parts had drain holes or gaps.

But there was some direct weather exposure on a 2x2" tube that had to be dead level (horizontal). So it needed to be closed.
I fogged the inside of the tube with penetrating oil; sealed one end; taped the other end with a rubber hose shoved inside, all the way to the sealed end (~11'8"); and purged through the hose with C25 gas at a low flow rate for about 25 minutes. (75% argon, 25% CO2)
I pulled the hose slowly, sealed that end up, and crossed my fingers.

I couldn't help but wonder, so I drilled a 7/32" hole in the center this summer - just over 6 years later. There was a short, satisfying, little 'hiss' when the drill penetrated. I stuffed my .190" bore scope in there and it looked like the day I sealed it.
Short purge, acetone, zapped with the welder, quick hit with flap wheel, touchup with primer and paint, and I'm never going to worry about it again.
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Re: Teardrop frame for saltwater environment

Postby MickinOz » Mon Feb 06, 2023 6:46 am

If you don't want to get your frame hot-dipped in zinc after welding, you can do what a lot of home builders do here.
Use galvanised steel. Clean the zinc off wherever you need to weld it, then spray it with cold galvanising zinc rich repair paint.
Lots of boat trailers here in Oz are made with C-channel or even just angle iron.
It's pretty common here to weld the spring mount to a separate piece of angle iron that is bolted or even u-bolted to the main trailer frame.
This allows the axle to be moved backwards or forwards to balance the weight distribution.
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Re: Teardrop frame for saltwater environment

Postby JoshuaNik » Tue Apr 04, 2023 7:27 am

Using a c-channel for the entire frame could be a good idea to prevent rust, especially since you'll be using it extensively in the Outer Banks. As for your questions, welding the ends of the square tubing closed and using oil during the welding process could help prevent rust. As for finding designs for c-channel frames, have you tried looking on YouTube or camper-building forums? If you need a service to make your work more eco-friendly, I suggest checking out www.carbonclick.com. I hope it helps!
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Re: Teardrop frame for saltwater environment

Postby Juneaudave » Tue Apr 04, 2023 2:00 pm

FWIW....I wouldn't over think it too much. If it were me, I would just go ahead and weld it up, then prime it with epoxy primer and give it a good top coat. That should be good for 50 years and then you can repaint it :thumbsup:
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Re: Teardrop frame for saltwater environment

Postby kennyrayandersen » Sat May 13, 2023 4:58 am

kayakevan wrote:I'm looking at using 3 x 4.1 lb (3 X 1.41 X .170) c channel for the outside of the frame as well as the cross members and then 3x3x3/16 tongue tube. I also plan on adding angle braces to the tongue tube using the same c channel as the frame. Looking at the harbor freight trailer this seems like it's probably even overkill, but does anyone see any issue with these materials?


If you want to give me your layout dimensions and your gross weight I could run a few numbers, but that sounds like a lot of steel.

Having the frames dipped would certainly work, but I have no idea how much that runs. There is some stuff called Extend that you could paint on steel. It chemically bonds and reacts with the steel and causes a small layer of oxidation that would stop further corrosion, then you can painted over it. That's way cheaper and it works:

https://www.loctiteproducts.com/en/products/specialty-products/surface-treatments/loctite_extend_rustneutralizerspray.html

A lot of folks use POR 15 for coating car chassis, but it never quite hardens (I think): https://por15.com/products/rust-preventive-coating

They might be worth looking into.
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