POD: Custom camper - design stage

[pods8]

Need some thoughts here on how to open the outer door when the top is down and thus the inner door is blocking it.

I was thinking of using basic trimark RV handles like this:

My door thickness is 2", since the above handles are for 1.25-1.5" doors that helps me out so I can recess the inner handle mount .5-.75" into the door. I was thinking about putting cable controls into the door core and routing the actuation part near the top of the door (which would be above the inner/lower door). The lock latch is just back and forth which would be fairly easy, the latch release would likely need to have the cable control drilled into the housing to actually pull the latch release. Thoughts or better ideas?

 

[chris_the_wrench]

If you remember Basinrangers Fuso build. He had a pretty neat overlapping door solution, but unfortunately he deleted his entire build thread. I did download a bunch of the images he posted before that happened though. Hope this is legit...

-Chris

 

[pods8]

If you remember Basinrangers Fuso build. He had a pretty neat overlapping door solution, but unfortunately he deleted his entire build thread. I did download a bunch of the images he posted before that happened though. Hope this is legit...

-Chris

Yep I gawked through that thread numerous times, damn shame it's not up any more. (I still have no idea why he bombed out the whole thing).

Thanks for the pictures but between those and my recollection from his thread I don't recall him ever addressing how to get out from the interior with the top down, do you? (The outer door latch is blocked by the inner door, look at the second picture) For some folks they don't use their camper in that manner so it doesn't matter but I jump into my FWC a fair amount with the top down (and close the door) and would like to do the same on this new one.

I haven't really settled on anything yet in my head but my current slight leaning is to potentially build a little inward swinging "peep" door access hatch into the inner door that would open up a small opening (4" square?) to all reaching through to lock/unlock and open the outer door.

 

[windsock]

(Crudely) Using your top right diagram from a couple of posts ago, what about a lever system? This can be as basic as using one fulcrum point. Would be easier to implement than cables wouldn't it? Undo lever can have a spring-return on it so it stays in one position while not in use.

One lever to unlock/lock and one lever to open the latch. Top of levers are made so they are above the inner layer of the camper shell.

While I do like the 'peep' door idea, it is another hole in the side of the camper...

 

[Overland Hadley]

Yep I gawked through that thread numerous times, damn shame it's not up any more. (I still have no idea why he bombed out the whole thing).

x2

That was one of the best builds I have seen here.

 

[pods8]

Windsock, I had though control cables (or whatever you call the push/pull cables in the plastic sleeve) would be easier to bury in the door core as opposed to carving out a bigger free movement area for levers.

A peep door is another open for sure but it would be in the door zone which already has plenty of opening area going on already. So if there were issues with the peep door I'd likely already be needing to address them with the big door and at least it would all be in one area. I'm not sold on this idea yet but from a simplicity standpoint and having less probability of having a mechanical snafu it does have appeal.

 

[Birder]

Hi Pods8

I am following your build as i want to do something similar

http://www.expeditionportal.com/forum/attachment.php?attachmentid=62984&d=1307961275&thumb=1&stc=1

This is one of your images and i was wondering what you will be doing to stop failures at the marked points?

It seems to me that there will not be a lot of strength in points A & B and even point C could also fail.

Great build so far, i will be using your idea of 2" wide ply at joins and around openings.

I shall be using a 2 part epoxy swimming pool / Boat paint system for my final covering as its avaiable in colours and clear

 

[pods8]

A&B are treated the same in my mind. I basically looked at the cabover as a big flat cantilevered beam. So then I took a cross sectional slice of it and did a beam calculation on it. However it isn't quite that simple since the "beam" is made up of multiple materials with different strength and modulus, so a composite calculation was done in excel to get the net result of the whole thing and start playing with different iterations to figure out what was going to be required. (Sorry if that is starting to get a bit too technical, I pulled some help setting up the calc myself as those brain cells were a bit dusty).

The top of the cabover rails basically end up needing reinforcement is the short answer. The amount is a function of geometry, the taller/wider the rails are the less reinforcement needed. There are numerous ways to build of the reinforcement as well. You'll get the most weight/strength ratio out of unidirectional material.

I took a more efficient dollar and time route though at a slight weight sacrifice (but in reality it is a very small difference in the overall weight of the camper). I utilized some fiberglass pultrusions available on the market. My rails are 2" wide on the sides and they make a 2" U channel pultrusion with 9/16" sides that looked like a nicely made rail cap to me. In terms of the calculation a single 1/8" pultrusion on the top of the rail should theoretically take the load based on my geometry but if there is one place in the camper I'd like to beef things up a bit this was it. The U channel provides a nice dish to lay up additional reinforcement into so I added another 1/8" strip of pultrusion into it along with a few plys of some fiberglass tape I had on hand that was 75% fiber content in the length direction (uni tape would have been even better but I already had this on hand and was just adding on at this point).

So in the end in terms of the calculation I'm 4-5 times the factor of strength required now. I'll wrap my fiberglass skins over top of the pultrusion rail when doing those laminates which will build more material up and tie it into the structure. Additionally the fold up cabover walls will be installed with continuous hinge along the rail that will be riveted into this pultruision which aside from mounting the hinge should sandwich the body skin between the pultrusion and hinge to have one more item holding things together. I've done my due diligence, now it's time to see how it performs in reality.


The stresses at C should be low since it is such a large wall section there but I'll likely go overkill with extra plys of cloth when I glass things together there.

 

[Birder]

Still not sure i fully understand,

Your U channel would do nothing on the underside of the overhang unless it goes into your sides so i take it that your 2" channel will sort of cap the top of the wall.

I still cant see it being strong enough but you are certainly more technical than i am and i dont think i could calculate such things.

For interest:

On the carbon covered foam camper he has a U channel in alloy on top of the wall so its a C all the way along so i can see how its going to work. On yours you only have a foot or so on the right hand side before the door opening.

I will keep watching with great interest.

 

[pods8]

Yes I'm using the U channel to top the cap of the cabover rails (side walls on the cabover) and extending a bit onto the main wall top.

The way beams work is the upper and lower surfaces farthest from the nuetral axis carry the bulk of the forces applied in the structure. The amount of force the upper and lower surfaces can take is a function of their strength and the amount of material present. Since the cabover rails are thin, comparatively, an extra build up of material is required. On the lower surface of the cabover the forces are spread across the entire width of the cabover so although there isn't any additional laminate built up there specifically there is a moderate amount of material present never the less. (Note if I terminate the underside of the cabover at a right angle into the wall it would create a stress concentration though, I'll radius that transition some when I'm reassembling the glassed portions).

The other aspect of beams in the greater the distance from the nuetral axis the lower the forces are. So once I've transitioned into the main wall sections there is a much larger section for the forces to spread out across. The short chunk of wall before the door is an area I'll diligently assemble since it could see some higher stress in the material but in general the layup schedule I'm doing should carry quite a bit of load, theoretically of course. We'll see.

I'm familiar with home skillet's carbon fiber camper. His build kicked off my interest I've just taken a bit different path with mine. From my chat's with him I don't believe he actually calculated his cabover frame as opposed to using a channel section similar to how the aluminum framed pop up manufacturers are doing. The amount of aluminum there should definitely be adequate, as he's demonstrated, but the key is it needs to remained tied into the structure. In my research I wasn't comfortable with the long term bond-ability of epoxy to aluminum in a home based setting for structural usage (certain anodizing processes developed by the airline manufacturers would be good it seems but again not something I'm going to duplicate at home). Because of the way he embedded that channel though the whole length of the camper though I don't really suspect he'll run into issues even if it does delaminate some over time. However although aluminum is light that is a decent hunk of metal he's got in there which I didn't see the need for when some selective build of up glass material would do the trick and makes me far less concerned about delamination. (Delamination is something that is a nagging concern of mine, not just in terms of epoxy to aluminum but also with the interface to the foam structure, that is why I've also embedded all the wood strips in the middle of large panels since the shear strength of wood is much greater than the foam).

More that one way to accomplish things, this just happens to be the route I've decided to utilize.

 

[Birder]

Your wood strips are a great idea and i shall be using that in my build, however i shall be making interlocking joints where they cross using opposing cut outs that will slot together. My idea is to make the strips so i can get everything ready and numbered and then assemble it when the weather is perfect. I am thinking of putting corner triangles in as well.

Using foam i could not see how i could have a cabover as i felt it would sag and i dont want to use alloy beams.

I am not in a hurry so will keep watching your build as you seem to have all your ideas worked out

Thanks for your help and sharing

 

[pods8]

Using foam i could not see how i could have a cabover as i felt it would sag and i dont want to use alloy beams.

That's the thing right there, I'm not using foam, I'm using fiberglass. In reality you can ignore the foam outright in your calculation and assume it's just air there since you're not trying to have it carry load (I didn't ignore it but you could since it really doesn't change anything in the numbers).

Here's screen shot of my finalized scenario, probably will make you want to cross your eyes but the "FoS" column of the lower left set of numbers is the factor of strength. I'm in the 6x range for all the glass components on that rail. That bottom skin is 18x (ie it it could take 18 times the stress before failure).

I've done my calculation for 800lb at the end of a 60" cantilever which is aggressive in itself. The wood strips I used between the rail and the bottom in assembly are actually what will start to fail first according the calculations and that is with 2000lb applied at the end of the 60" cantilever. We'll see how well that matches reality but ideally this should hold up just fine for "mom and dad time" or the kids jumping on mom/dad.

(Note this type of calculation is not my specialty, I pulled some help from a fellow familiar with home built composite airplane construction.)

 

[trackhead]

Has the build started yet? Or is it still in the design/theory stage?

 

[pods8]

Has the build started yet? Or is it still in the design/theory stage?

Slowly coming along:
http://www.expeditionportal.com/for...re-fiberglass-skin-pop-up-camper-build-thread

The design thread is still being used to hash out design ideas so the build thread doesn't necessarily get cluttered to much with what I didn't do and more focused on what actually was done.

 

[trackhead]

Slowly coming along:
http://www.expeditionportal.com/for...re-fiberglass-skin-pop-up-camper-build-thread

The design thread is still being used to hash out design ideas so the build thread doesn't necessarily get cluttered to much with what I didn't do and more focused on what actually was done.

Cool, thx, hadn't seen that.