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M109 - can we extend the box?

Silvae

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Question for those who have tinkered with an M109 and seen how the box is constructed - we are about to buy an M109A4 and want to convert it into an offroad camper, but are wondering if we can squeeze a bit more room lengthwise. The box is about 12 feet long, and we were wondering if it is feasible (or sane) to cut the box at some point and extend it out a few feet, then weld it all together again with additional support beams underneath to carry the extra length. This would give us a 14-15 foot box, which is a sizable improvement - about 20% more floor space.

Any thoughts of whether this is feasible? Or does anyone have an alternate solution to expand the living area of the M109?

Thanks! Once I get the truck and start the conversion, I'll open a thread to document it.
 

Jeepsinker

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If you do, lengthen the frame of the truck too. These truck frames flex almost as much as the suspension does. If you don't extend the frame rails to make the box move with the frame, you'll tear it apart in short order.
 

Silvae

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Awesome replies, guys! I really appreciate it. And thanks for the pics and the mdmorgan thread - those were super helpful! Amazing work, btw.

That's the other concern we had - how the movement dynamics work. I don't want to be halfway into an Appalachian forest only to realize my box had pulled off the frame and fell off onto the trail at some point.

I was looking at the M36 and considering just building a custom box on it, but due to movement issues, I don't know how to construct the box. Wood studs and plywood clad in siding? Steel shed/garage ribs with sheet metal walls? I'm not mechanically inept BUT I'm also concerned that this construction project would be too much for me to competently handle given the dynamics of a moving, twisting vehicle, leading to the aforementioned box tumbling off the bed. The 109 seemed to be a nice happy medium as a challenging build but won't be too much to bite off.

Happy Thanksgiving, BTW!
 

Silvae

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Why not just get an M934?Why reinvent the wheel?
That was my first thought. However, a yellow flag came up as I researched it and found LOTS of people selling 934s as "perfect for" RV or camper conversions, but none that actually MADE an RV out of it. The best I saw were essentially indoor camp sites with cots and loose furniture. No one actually installed cabinets, beds, showers and toilets, water heaters, etc like you would expect on an RV (which is the direction we want to go). Then I did further research and it seems the way the 934 expansible sections slide out makes them poorly insulated and leak-prone (and thus not conducive to an RV interior) and the physical structure and expansion mechanics make it ill suited to convert into an RV. So, I settled on the 109 as the next best option.

If someone knows of someone who did a full RV style conversion with a 934, I'd love to see it. I'm sure nothing is impossible, but remember we are not trying to bite off more than we can chew with our full-time work schedules and limited funds.
 

cattlerepairman

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I do not have an M109 but I think I have read next to all M109 RV conversion threads on here, because it is something that fascinates me.

Perhaps you need to go see an M934 and evaluate what modern materials (spray foam insulation, styrofoam glue-on insulation panels etc.) can do for you. Perhaps speak to someone experienced converting buses and vans into RVs. They now spray foam a lot.

It seems to me that the work involved to build a 2 or 3 ft section of an M109 box (or chop another box and graft the section onto yours) is very involved, especially for a leak-free, rust-proof and good looking job. Then you have to deal with the frame extension (or get an M36 chassis; but then you lose the A4 upgrades).

Perhaps an M36 and a newer 14ft shelter container would suit your needs?
My five cents is that extending the box on an 109 is lots and lots of work and headaches for what could easily end up to be a mediocre end result, given the effort. I think you are very wise in considering the "bite-size" of the work ahead from the get-go.

Also, a M1079 (FMTV 4x4 with box) might give you that little extra space. They are pricier but the box sure is well built.
 
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SCSG-G4

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An M-36 will give you five feet more room (17 vs 12), so cutting and splicing in the box is a bit more complex, as it probably needs to be done in two places. But you get five more feet of length, and thus almost another 40 square feet of space to add to the original 96. Almost a 50 percent gain. From a time perspective, it might be best to get two 109 boxes so you would have all the interior and exterior pieces pre-shaped and would just have to cut for the length you desire. Sounds like an interesting project!
 

Recovry4x4

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Would likely be much easier to find an M146 box and section out the extra length. The M146 box is 22' vs the M109 12' and has the side door as well.
 

camoyj7

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I'm pretty sure the M146 is aluminum and M109 is all steel. Recovry4x4 has a great idea cutting down an M146. Weight is the biggest problem you will have with a deuce. Just not enough power. I stretched out a deuce and added a regular size M109 and 45-50 mph was top speed.
 

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