S-318 extending

sokoji

New member
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Kennewick, WA
Probably a foolish question but how hard would it be to make a s-318 longer to fit my long bed. A s-250 is too short as well and I got the s-318 for a good price. Just wondering if anyone had worked on the shelters much. Any thought would be appreciated.IMG_20210228_085409998.jpg
 

Coug

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Location
Olympia/WA
So if this is like the other shelters I've seen or worked on before (only a couple times helping out in the motorpool) it's basically a frame, a whole lot of spray foam, and a layer of aluminum on the inside and outside.

To make it longer would likely be a bit of an undertaking. You'd have to start by cutting it in half, stripping a bunch of the foam away to get to the structure, then weld in extensions for everything to make it longer. Then rivet one side of the wall in, fill the interior back up with foam, and apply the outer layer and rivet it on (or some just used the binding power of the spray foam to hold together, and were a royal pain to get apart)

So short answer is a lot of aluminum for the frame, aluminum panels, spray foam, aluminum rivets and rivet gun, and some pretty good aluminum welding skills. Then steel to extend the length of the skids underneath as well.


That's a rough idea of what it will probably take if it's similar to the S-250 series.

You're talking about a shelter that's 50 years old (maybe newer manufacture, but still an old design) so if you have the materials and skills it should be doable. Might have a different type of insulation in the walls rather than spray foam, but you can likely use the spray foam instead.

Easiest way would probably be buy a second shelter, cut the front end off one, the rear end off the other, and weld them together to extend them. Might require some additional strengthening if you ever plan for it to be lifted by the top corners.
 

sokoji

New member
20
2
3
Location
Kennewick, WA
So if this is like the other shelters I've seen or worked on before (only a couple times helping out in the motorpool) it's basically a frame, a whole lot of spray foam, and a layer of aluminum on the inside and outside.

To make it longer would likely be a bit of an undertaking. You'd have to start by cutting it in half, stripping a bunch of the foam away to get to the structure, then weld in extensions for everything to make it longer. Then rivet one side of the wall in, fill the interior back up with foam, and apply the outer layer and rivet it on (or some just used the binding power of the spray foam to hold together, and were a royal pain to get apart)

So short answer is a lot of aluminum for the frame, aluminum panels, spray foam, aluminum rivets and rivet gun, and some pretty good aluminum welding skills. Then steel to extend the length of the skids underneath as well.


That's a rough idea of what it will probably take if it's similar to the S-250 series.

You're talking about a shelter that's 50 years old (maybe newer manufacture, but still an old design) so if you have the materials and skills it should be doable. Might have a different type of insulation in the walls rather than spray foam, but you can likely use the spray foam instead.

Easiest way would probably be buy a second shelter, cut the front end off one, the rear end off the other, and weld them together to extend them. Might require some additional strengthening if you ever plan for it to be lifted by the top corners.

Thank you, that was what I was looking for and gives me a bit to think about. The main part that worries me is the welding aluminum, I can weld steel just fine just don't have the tools or know how for aluminum. Would it be crazy to extend it with steel and rivet/bolt it together ?
 

Coug

Well-known member
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622
113
Location
Olympia/WA
Thank you, that was what I was looking for and gives me a bit to think about. The main part that worries me is the welding aluminum, I can weld steel just fine just don't have the tools or know how for aluminum. Would it be crazy to extend it with steel and rivet/bolt it together ?
the problem is that steel and aluminum don't play well together.

Do a little research on "galvanic corrosion" if you don't already understand about it.

Basically, if any moisture gets into the same area as bare steel and aluminum are in contact with each other, it will cause corrosion. Enough corrosion to eat through the frame.

Extending it with steel, in my opinion, would be asking for major issues in a few years down the road, where things will literally start falling apart. Getting everything perfectly sealed up again after you work on it would be a royal pain, and you won't know if it's actually sealed without taking it back apart and verifying, at which point you start over.


Usually when the two metals have to be used together there is some sort of barrier between them, be it a chemical coating/process of some sort, or a physical one. When I took apart my DRASH trailer there was a lot of thick plastic tape stuck all over the frame (steel) wherever there was anything aluminum in contact with it. I didn't have whatever plastic they used, so I used 20 mil PVC tape from the hardware store in the plumbing/irrigation section.


I don't think bolts and steel would be the best idea for this job. It might work, and might last many years, but I think in the end it will eventually corrode/fall apart. Might be a couple years, might be a decade or more, so it really depends on how much effort you want to put in and how long you expect you might want to keep it/use it for, as well as what type of value it will still have when/if you ever decide to sell it.
 

sokoji

New member
20
2
3
Location
Kennewick, WA
I know alittle about galvanic corrosion, that's why I was worried about using steel, I was just hoping if I kept everything primed/ painted and used a corrosion inhibiting paste between all the places there were dissimilar metals it would last a long time. But like you mentioned it's the best to keep it all aluminum I'll just have to find a fabricator that can make and weld in the corner pieces and i can do all the skins and rivets.

the problem is that steel and aluminum don't play well together.

Do a little research on "galvanic corrosion" if you don't already understand about it.

Basically, if any moisture gets into the same area as bare steel and aluminum are in contact with each other, it will cause corrosion. Enough corrosion to eat through the frame.

Extending it with steel, in my opinion, would be asking for major issues in a few years down the road, where things will literally start falling apart. Getting everything perfectly sealed up again after you work on it would be a royal pain, and you won't know if it's actually sealed without taking it back apart and verifying, at which point you start over.


Usually when the two metals have to be used together there is some sort of barrier between them, be it a chemical coating/process of some sort, or a physical one. When I took apart my DRASH trailer there was a lot of thick plastic tape stuck all over the frame (steel) wherever there was anything aluminum in contact with it. I didn't have whatever plastic they used, so I used 20 mil PVC tape from the hardware store in the plumbing/irrigation section.


I don't think bolts and steel would be the best idea for this job. It might work, and might last many years, but I think in the end it will eventually corrode/fall apart. Might be a couple years, might be a decade or more, so it really depends on how much effort you want to put in and how long you expect you might want to keep it/use it for, as well as what type of value it will still have when/if you ever decide to sell it.
 
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