Cabover camper build help...

Discussion in 'Materials' started by Auntie Frannies, Apr 23, 2018.

  1. Auntie Frannies
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    Auntie Frannies Junior Member

    I initially joined this forum out of extreme interest in the Crowther Buccaneer 24 plans and also build of Kurt Hughes formula 40, but it never worked out to get started on a boat build. Now I am on a different project that I would like some guidance on materials and construction.

    What I am wanting to build is a cabover style truck camper for my commercial medium duty truck with leaf spring suspension. It has to be strong enough to last for hundreds of thousands of miles at highway speeds and the impact of a stiff spring suspension hitting all manner of bumps and pot holes without breaking apart.

    I have attached a rough sketch I attempted in Blender. The outside width is 7-7.5 ft. Length of the main floor is 60" and cabover about 60" long also. Not shown would be a cutout in the front wall below the cabover section for a pass-through into the truck cab to avoid having an outside door. Also would like to have two small windows either in the sides or front of the cabover and two more windows in the side walls for adequate ventilation in all climates.

    I was considering using 2" Dow Foamular 250 XPS foam board as a core as this is the highest compression strength(25psi) stocked locally, the 40psi and up would likely cost 3 or more times as much with the minimum order requirements and shipping costs. And skinning the foam with okoume plywood(4-6mm?) and perhaps 1"x2" 's in the corners and across the span of the floors for a frame.


    Will this idea work and can it be built under 500lbs?

    Thanks for any advice,
    Brandon
     

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  2. SamSam
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    SamSam Senior Member

  3. PAR
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    PAR Yacht Designer/Builder

    I wouldn't use the foam for a core inside a plywood skin, but rather just skin the foam with epoxy and an appropriate amount of fabrics. Frankly I don't think you need the foam. You could do this as a single skin GRP or as a taped seam plywood job. Both would likely be under 500 pounds, probably by a good bit. A single skin GRP could use cheapo foam, that's serves to form a male or female (preferred) mold. You toss your fabrics in, of course after making the mold, wet them out, roll out the air bubbles and let it cure. The foam would be covered with a release agent, polyethylene or other materiel to prevent the goo and fabrics from sticking to it. You just pop it out, finish as desired and bingo, Bob's your brother.

    Plywood would save the bother of a mold, though some shape limitation would be necessary, so you can bend in the plywood. Boats are built like this quite commonly and it's strong and light too. Basically, you cut and hold the edges of each panel where it needs to live, cover the edges with goo and 'glass tape. When this cures, you go back and reinforce all the seams (both sides) with more goo and tape (if necessary), then finish as desired. Given the quite annular structure you have, plywood seems well suited, but it's your call. The internal furniture can be added afterward or done at the same time as the outer shell.
     
  4. Auntie Frannies
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    Auntie Frannies Junior Member

    Thanks for the replies.

    The reason for the foam is insulation. I will be sleeping in this in climates from -10F to 100F with my wife and kids and minimal climate control. Since the foam has to be there anyway, my thinking was why not make use of it as a structural element?

    Was I underestimating the strength of a thin okoume plywood over foam core for this type of structure? Maybe no wood framing but only some inserts where it will mount to the trucks frame and to give something substantial for mounting cabinets and the fold-down berth? A couple of layers of mid-weight glass on the inside of panels, epoxy and fillet the panels together and then glass the outside?

    I am worried, if I build it too light, I will either have the cabover section start breaking away or the floor to wall joints failing . If I am over-building I may end up with something too heavy for my purposes.

    I currently assemble boats for a living and have little to no knowledge on the engineering of composites so please forgive my ignorance in this area. Thanks in advance for any follow up replies.

    -Brandon
     
  5. fallguy
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    fallguy Senior Member

    The cabover part adds some complexity.

    You’ll need some pretty good strength to support 5-600# load.

    I’d build it from 1” foam on the sides and probably 1208 glass, or maybe skip the mat.

    It is going to cost you like at least 2 grand for epoxy glass and foam. The bottom would be 3/4 plywood to take the sliding in n out and walking on/point load. Probably ditto on the cabover.
     
  6. PAR
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    PAR Yacht Designer/Builder

    I think 3/4" is the melon farmer way to get it done. It'll work, but it'll be heavy as all hell and other concerns. Insulation is an easy thing to take care of, once it's built. I'd use Dynamat products, just like any car or truck. It's light, effective and doesn't require a lot of room. Besides, you're going to put in carpet or some other surface covering anyway, which will cover the Dynamat, right. Lizard Skin is an other option, though I'm not sure about i't properties on things other than metal.

    You should be concerned about local reinforcements, which is all I think you'd need. This means either thicker 'glass in some areas or a foam composite sandwich or even just a hunk of plywood to locally stiffen some spots as recognized.
     
  7. fallguy
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    fallguy Senior Member

    Keep in mind these can be inhabited while on stands. The clearspan width is 4’. And the cabover section is camper queen sized bed with hopefully ocassional dynamic loading, but zero support from beneath. What kind of composite would work for that? Basically a 4x8 sheet each way with no support under. The walk in section typically has a galley, so you could stringer that from above, but the other side is typically an open table/salon. It could be raised for a stringer if you will as well; I suppose, but you still have the same width of span. Just less the galley width; so say 30” clearspan.

    I asked a question on the forum a month ago and got no solid response. All I wanted to know was how to calc deflection in a 20” wide composite stair tread. Got crickets mostly.

    Here; you’ll have four people potentially going in n out.

    Even just to clean bedding these get walked in w/o the truck under.

    I suppose you could box beam composite for a 4’ span rating.

    melon farmer
     
  8. PAR
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    PAR Yacht Designer/Builder

    How much work have you done in Blender? I ask, because it's likely you'll need a bit of engineering to address loading and laminate schedules. Can you post more images, say a profile, plan and sectional view and any others you think may describe your structure a little better.
     
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  9. fallguy
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    fallguy Senior Member

    As with many of these I think the OP left the room when he realized how much trouble it was gonna be Versus buying a used unit off of craigslist for three grand
     
  10. fallguy
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    fallguy Senior Member

    I just like to add there’s a reason these are not made as good as boats. The costs are simply too high
     
  11. Auntie Frannies
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    Auntie Frannies Junior Member

    I am pretty much an amateur in Blender. I have used it on and off over several years, but never long enough to get good at it. I pretty much have to relearn it every time I dig it back out for something.

    If you look at the top view picture, the rectangles coming out to the right is the truck frame rails. This is not intended to be a slide in type camper, but bolt to the frame. This is more like a non-integrated sleeper on a semi truck. You can find them used for under $1000 but they don't have the interior volume and are over 600 lbs.
    Slide-in truck campers are easily 1000+ lbs dry weight, likely to have damage in the cabover section from water leaks and would require major modifications to fit between the cab and trailer.
    Since it is intended to be a rather permanent install, maybe I would be ahead by building something that is attached with bolts and adhesives to the cab itself?
     

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  12. SamSam
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    SamSam Senior Member

    If it's a pickup, the cab and bed usually move separately which wouldn't be good.
    There are a lot of diy plans that you can use directly or get ideas from.
    diy truck camper plans - Google Search https://www.google.com/search?q=diy+truck+camper+plans&client=firefox-b-1&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjnruDXveDaAhXjmOAKHf_uAv8QsAQIJg&biw=1345&bih=647#imgrc=2n06NPzWHggDlM:

    diy foam truck camper - YouTube https://www.youtube.com/results?search_query=diy+foam+truck+camper
     
  13. Auntie Frannies
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    Auntie Frannies Junior Member

    It is a cab and chassis, not a pickup. Something like this attachment is what I am working with.
    truck and trailer.jpg
     
  14. gonzo
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    gonzo Senior Member

    What is the width of the frame, and the overall width of the cab?
     

  15. Auntie Frannies
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    Auntie Frannies Junior Member

    Outside frame width 34"
    width of cab ~76"
    width of roof ~56"
     
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