Sleeping on the roof

[wagondude]

Make your floor follow the curve of the roof or put rails to support the outboard edges of your platform. The primary structure of the roof is in the side rails (where the roof rack bolts down). Putting the flat floor on top of the curved roof can cave in the top making the sunroof inoperable.

[GPW]

Here’s an idea ..... if you’re not particularly tall and require a lot of headroom , why not cut the roof off , and flip it over so it protrudes down into the TV area, giving you several extra inches of clearance so the topper doesn’t have to be so tall ...

[mvankanan]

If you are worried about aerodynamics at all the first worst thing to do is build up.

Well I am, however I think that I’m limited in what I can gain from it, I’m pretty committed to the height of about 2’. If I get the mock up covered with plastic and blow over I won’t do it. If I do do it I guess what I would like to know is how much changing the front angle from 45 will matter, should the point where the angle meets the roof be the highest point with it sloping back to the rear, or should I raise the rear and lower the front? I only have an inch or two to play with, so will that matter? Should I roll that point, kerf and bend? It would probably be tight since I would think I would need the front roof part fairly flat to get some form of skylight in there. I would rather not kerf, feel I got enough challenges.

Re: roof spars, the assembled strength comes from the inner and outer skins, so interrupting the inner skin by letting the spars interrupt the ceiling panel will not yield maximum strength.

I kind of guessed that but it is a kind of truss if it is all glued together isn't it? I don't know but would like to.

Better to have the spars sandwiched between skins.

The only reason I added spars was because of my build sequence. I wanted to install my ceiling ply before forming the foam arch over the top of it and the ply would not support its own weight. If I had built a form to build the roof panel over I may have been able to get away w/o roof spars, but that would have taken more effort and lumber to build the form. It was just cheaper and easier, and more accurate to build in place using spars.

If you are building your roof panel out of foam and then applying a canvas ceiling skin after the fact, you might get away with no spars. The foam can surely support its own weight, especially if kerfed and arched.

Well I would like to build without spares to save weight. I do want to have some kind of tie down and I’m thinking it might be best to have wood completely under the tie down points, across the top and down the sides like a door frame or square arch? When I pick up the 2” foam I’ll support the sides and see if I can lay on it.

[mvankanan]

Thanks wagondude

I kind of mangled my last post, this one I'm going to paste from word

The roof has ridges on 8” centers running front to back. Whatever kind of panel I build will spread the weight out on those. I think that the rails that hold the rack are also on one of those ridges. There is slope front to back with most of it in the last foot or so to the windshield and just the last six inches to the rear. I’m still inclined towards one of those wide gaskets séanc used on his truck cap.

I’m also planning on bolting it down through the holes for the roof racks, and across the front. So I will need to fill in along the whole perimeter and create a seat for the gasket. I will also have a sort of well around the openings front and back. These could fit tight to the roof and I could shim the panel there, I think we are talking fractions of an inch so I’m hoping the plat form might just bend a little where needed.

I should be able to shim to the roof at any bolt, allowing for gasket compression. As soon as I get the 2” foam home I’ll throw the flattest piece on the roof, after removing the roof rails. That should give me a good idea.

The sky light in the front won’t open; it’s just for the view up from the passenger seat. I don’t know if I will have a skylight in the build, I’ve been offered one from a Volvo, but it’s buried right now, so I can’t see it yet. I’m planning on wiley windows on three sides of where our heads will be.

Thanks again mike

[mvankanan]

GPW

Lot's of merit in your suggestion, I'm thinking there might be a bit more engineering and welding

[lthomas987]

It seems that everyone uses some wood in the roof, are these structural? Since interior height is important to me, has anyone routed these into the foam, say ¾”, would this add to or decrease the strength? It would give a larger gluing area.

Not everybody uses roof spars. Many don't use spars. My roof is spar free. I have set many moderately heavy things including my dogs up there. I haven't tried getting up there myself as I am not moderately heavy but quite heavy.

Also don't fear kerfing. It's not very hard and can make seam free sections.

From my roof top hauling experience I would strongly suggest radius-ing all your corners. Sharp edges make a lot more noise in the wind.

[GPW]

Just a drawing of an inverted top idea .... any old Hot Rod body man could easily do it ,cut around the drip edge flip it and weld it back upside down with little tabs to the drip edge to support it all ... If it didn’t interfere with your interior headroom , it would give you about 4-6” of extra cabin height without being that much higher over the top of the vehicle ... You could even cut your hatch in the front so as to crawl up into the sleep chamber...

[mvankanan]

It seems that everyone uses some wood in the roof, are these structural? Since interior height is important to me, has anyone routed these into the foam, say ¾”, would this add to or decrease the strength? It would give a larger gluing area.

Not everybody uses roof spars. Many don't use spars. My roof is spar free. I have set many moderately heavy things including my dogs up there. I haven't tried getting up there myself as I am not moderately heavy but quite heavy.

I'm thinking of perhaps only under the tie down points, I will eventually post something if/when I get that far

Also don't fear kerfing. It's not very hard and can make seam free sections.

It'll make me stronger?

From my roof top hauling experience I would strongly suggest radius-ing all your corners. Sharp edges make a lot more noise in the wind.

I've heard this before, would you just run a router along the finished build before skinning? I'm not sure I see this in the pictures of the build's, but maybe I'm missing it, a lot of info to absorb.

Not sure I didn't mangle the quote thing again

Thanks Laura

[mvankanan]

Just a drawing of an inverted top idea .... any old Hot Rod body man could easily do it ,cut around the drip edge flip it and weld it back upside down with little tabs to the drip edge to support it all ... If it didn’t interfere with your interior headroom , it would give you about 4-6” of extra cabin height without being that much higher over the top of the vehicle ... You could even cut your hatch in the front so as to crawl up into the sleep chamber...

Well I used to think a old Hot Rod body man could do all kind of things, and then I got scared because of all this unitized body talk!

I really do like your idea, and I thought a bit about it, it did seem a little more complicated. I never really got beyond thinking about it, I think the dimensions might not work out in this case. I think it might end up like building a bed in the back of the vehicle, you end up with not so much usable room when your rolling. I got a pretty big dog.

Anyway depending on the weather I hope to get my mock up wind proof and on the road by the end of the weekend. Hope for some high winds.

[KCStudly]

...would you just run a router along the finished build before skinning? I'm not sure I see this in the pictures of the build's, but maybe I'm missing it, a lot of info to absorb.

I used a 3/4 round over bit to radius the ends of my spars before filling the roof bays with foam that stuck off the edge of the roof a little. Then I sanded that foam back flat to the wall.

A guide bearing won't follow foam well. It will push in, so I just used the ends of the spars as sanding guides. In this post you can see how I developed a sanding block and technique to sand a decent radius into my profile edge: http://www.tnttt.com/viewtopic.php?p=1139355#p1139355.

Here You can see how I added guidelines to improve the technique: http://www.tnttt.com/viewtopic.php?p=1139586#p1139586.

[lthomas987]

It seems that everyone uses some wood in the roof, are these structural? Since interior height is important to me, has anyone routed these into the foam, say ¾”, would this add to or decrease the strength? It would give a larger gluing area.

Not everybody uses roof spars. Many don't use spars. My roof is spar free. I have set many moderately heavy things including my dogs up there. I haven't tried getting up there myself as I am not moderately heavy but quite heavy.

I'm thinking of perhaps only under the tie down points, I will eventually post something if/when I get that far

Also don't fear kerfing. It's not very hard and can make seam free sections.

It'll make me stronger?

From my roof top hauling experience I would strongly suggest radius-ing all your corners. Sharp edges make a lot more noise in the wind.

I've heard this before, would you just run a router along the finished build before skinning? I'm not sure I see this in the pictures of the build's, but maybe I'm missing it, a lot of info to absorb.

Not sure I didn't mangle the quote thing again

Thanks Laura

Only slightly mangled the quote. Better than I ususally manage.

Kerfing will make you stronger! If you've got a table saw or circular saw with adjustable depth it's dead easy. Really.

For rounding over the edges I didn't try a router. I'm personally a menace with a router (probably due to lack of even the most elementary instruction) I did try making a hot wire round over cutter. Didn't work as well as I'd like. In the end I just used the super reliable surform plane. I knocked off the corner to 45 degrees, then each of those corners, then I went back and just evened up all the rounding by eye. It made a bit of a pink foam mess but it wasn't hard and didn't take long.

[mvankanan]

KC and Laura

Thanks for the info.

I covered the mock up with some plastic tarps and took it up Rt 89 in NH, it's the windiest highway I could think of. I tried to keep it above 70, got it up to 85 down hill, never really felt it much at all. Never felt any lean on the curves. I still had pick up at that speed. I got 15.4 mpg, not great for sure. It wasn't loaded other then the mock up, though I made that heaver then I think it might end up. It was also a little higher and longer then it will end up, but it didn't go down to the bumper because I didn't wont to block the lights and plate.

So I think I'm going to do it. I'll get it off and on saw horses and play around with the final shape. I think I will try to kerf and bend the nose, that might get me a little lower in the front but still let me crawl in. It will be slow going at first, other stuff to do, but I'll try to keep up the pictures of the build as it happens.

I'll have a lot of questions I'm sure, but I think the first step will to fab the platform for the floor, and get that up on the roof. It looks like there is a little more curve than I thought.

Should be a fun project Mike

[mvankanan]

I got the headliner out, I was a little bummed out because the cross ribs were in the way of my holes in the roof. I went and saw my car guy he said mike think about any van conversion when the take the whole roof off, where are the cross pieces? So now I’m a whole lot less worried and I’m going to just go for it. Bad weather for the next week it looks like; wish I had a big shop with a level floor.

As far as not worried about cutting into the roof, this frees up the design a bit, if I can move the entrance hole back, with a drop in panel to sleep on, I think I can change the build profile and lower the front height, and angle. I’ve been playing around with crawling in and out of the mock up with different heights, if the hole is larger I can get by with less height, at least in the feet end. Maybe a pop up part over my head?

It occurred to me that it might be a lot easier to bend tubing to fit the roof profile, I could then screw or bolt some plywood strips connected to the sides of the floor panel to the tubing, and the tubing to the roof. This might make it a lot easier to level. I wouldn’t have to be as accurate cutting the bottom of the ply strips, I could then wrap the canvas under the whole floor, and then set it back on the tubing and attach it. The problem would be in getting some kind of gasket for the tubing? Something like that slip on foam pipe insulation comes to mind but that wouldn’t be rugged enough. Anyone have any ideas for the gasket?

I’m thinking emt conduit for the tubing. More weight then I want, but that seems easier to fabricate? It would need to be u shaped two sides and the front, maybe one and a half inches so I will have more meat to attach the build?

I guess I will use titebond 2 to make the floor panel, 1” foam 1/8 luan top and bottom, wood around the edges to bolt thru. I’m planning to leave it solid and cut out the holes for the skylight and entrance later, I’m thinking I could cut the holes and then rout out the foam, leaving the ply and then glue in the wood strips around the edges of the holes?

Whatever I use for the wood edges presents a bit of a problem because the foam is a full inch, wood is only ¾” seems like I might want it a little wider for bolts? 5/4 on the flat is still only 7/8”? I’m thinking of gluing 1x3 together on the flat and then resawing that to get the full inch I need, I’ll end up with a 1 ½” x 1” piece. I guess I could try to find ¾” foam but I would rather have thicker, without the height constraints I would prefer 2”. I feel like I’m limited by what’s at Home depot 1” or 2” in full 4x8 square edge. Don’t want to get it shipped or special order for fear of damage to the edges and it’s only one sheet for the floor?

Getting the floor up on the roof should allow me to visualize what I’ll have to work with better as far as height. I have another wrinkle in that the jeeps a little wider below the roof in the back so once I get the floor up there I can get an idea of what I can do there. It is tempting to make the whole build a little wider than the roof but then I’m dealing with lift? Anyone with the engineering skills to puzzle me through that? It would be about 3-4” on each side? That might cause me to need more foam for the roof but then again I could angle that, say the bottom is 56” the top could still be 48”?

Thanks Mike

[Socal Tom]

I got the headliner out, I was a little bummed out because the cross ribs were in the way of my holes in the roof. I went and saw my car guy he said mike think about any van conversion when the take the whole roof off, where are the cross pieces? So now I’m a whole lot less worried and I’m going to just go for it. Bad weather for the next week it looks like; wish I had a big shop with a level floor.

As far as not worried about cutting into the roof, this frees up the design a bit, if I can move the entrance hole back, with a drop in panel to sleep on, I think I can change the build profile and lower the front height, and angle. I’ve been playing around with crawling in and out of the mock up with different heights, if the hole is larger I can get by with less height, at least in the feet end. Maybe a pop up part over my head?

It occurred to me that it might be a lot easier to bend tubing to fit the roof profile, I could then screw or bolt some plywood strips connected to the sides of the floor panel to the tubing, and the tubing to the roof. This might make it a lot easier to level. I wouldn’t have to be as accurate cutting the bottom of the ply strips, I could then wrap the canvas under the whole floor, and then set it back on the tubing and attach it. The problem would be in getting some kind of gasket for the tubing? Something like that slip on foam pipe insulation comes to mind but that wouldn’t be rugged enough. Anyone have any ideas for the gasket?

I’m thinking emt conduit for the tubing. More weight then I want, but that seems easier to fabricate? It would need to be u shaped two sides and the front, maybe one and a half inches so I will have more meat to attach the build?

I guess I will use titebond 2 to make the floor panel, 1” foam 1/8 luan top and bottom, wood around the edges to bolt thru. I’m planning to leave it solid and cut out the holes for the skylight and entrance later, I’m thinking I could cut the holes and then rout out the foam, leaving the ply and then glue in the wood strips around the edges of the holes?

Whatever I use for the wood edges presents a bit of a problem because the foam is a full inch, wood is only ¾” seems like I might want it a little wider for bolts? 5/4 on the flat is still only 7/8”? I’m thinking of gluing 1x3 together on the flat and then resawing that to get the full inch I need, I’ll end up with a 1 ½” x 1” piece. I guess I could try to find ¾” foam but I would rather have thicker, without the height constraints I would prefer 2”. I feel like I’m limited by what’s at Home depot 1” or 2” in full 4x8 square edge. Don’t want to get it shipped or special order for fear of damage to the edges and it’s only one sheet for the floor?

Getting the floor up on the roof should allow me to visualize what I’ll have to work with better as far as height. I have another wrinkle in that the jeeps a little wider below the roof in the back so once I get the floor up there I can get an idea of what I can do there. It is tempting to make the whole build a little wider than the roof but then I’m dealing with lift? Anyone with the engineering skills to puzzle me through that? It would be about 3-4” on each side? That might cause me to need more foam for the roof but then again I could angle that, say the bottom is 56” the top could still be 48”?

Thanks Mike

MIke,
Van conversions are built on a truck frame, the later model cherokees and grand cherokees are unibody contruction. The roof member are part of the frame that holds the whole thing together. If you cut those out, you need to install something to take their place, like a well built roll cage that ties into the chasis with strong connections.
Tom

[JaggedEdges]

Interested in development here, also want to do something rooftoppy, more leaning to tents though.

Some thoughts...

In Dodge vans which are also unibody, what I've seen done is that the pressed roof "ribs", were carefully cut off the area where the roof penetration was, and move forwards and backwards and rewelded. This may or may not be a suitable approach on the Cherokee.

Another thought is to look at the structural differences between the original XJ Cherokee and the Commanche pickups.

Sometimes manufactures publish or have available by special request vehicle modifier guides, that show the hardpoints and the "do not cut, really, ever" points on the structure to assist in police and ambulance conversions and other special uses. It seems to me I might have seen a mountain rescue Cherokee with raised top in the past. Also try looking for wheelchair conversions, may have been done for people in rural 4x4 required areas.

Also with this, Chrysler's unibody thinking still had a lot of body on frame thinking going on, many of them practically have a frame, it's just a layer of metal short, the floorpan capping the U section instead of box section then floorpan. It's not quite a case of fall apart as soon as it's got one hole in it, but caution still advised in modification. Another clue, round holes where possible, well radiused corners where you want something squareish. Spreads stress.

For the floor, 3/4 needed if it's going to be on a couple of roof bars, and all the weight on those... if you're spreading the weight thoroughly, then you can go down to half inch, maybe even lower if it's full foam contact to profile of roof. A clue on how that might be achieved... fill a huge bag with 2 part foam, spread on roof, squish floor down on top of it, let set, remove bag, trim it up and you've got perfect fit to roof. This foam kind of dense, might want to rough profile in styrofoam under you floor board, so you only need a thin layer of this.

Other things to look at for inspiration, Saab and Prius drop in campers, they're the tailgate removal cabover type.