Welding camper to F-250 questions

[rb_nw]

Hi Folks,
1st time poster to this forum- I've read through what I can find on here about pros/cons of welding a frame for a camper directly to the frame of a toyota. For what it is worth, I just got back from a 5 month trip in Patagonia where I welded a steel frame onto a 92 4Runner and drove around without any issues.

I just bought an '02 F-250 7.3 long bed and am planning on taking the back off the truck and building a cheaper version of an earth roamer rig.

Here is my plan and questions for folks:

1. I was planning on using 1 inch square steel to build the frame of the camper and then using wood studs inside of the metal for added structural stability. I want to avoid using all steel for weight and issues installing the exterior fiberglass siding. Question: Do you see an issue with welding directly to the frame of the F-250? I am going to extend the length of the car to a 12 foot box- so will be adding an extra 4 feet off the end of the car. The frame is super solid (clearly) and the weigh of the cab all finished should be way under 1000 pounds.

2. For the exterior walls I am planning on using 1/4 plywood with EPS glued on the inside to give it some added structural rigidity. From there I was going to fiberglass the outside of the box.
Question: what weight cloth would you use for the side walls and roof? I am having a little trouble understanding the ideal finish for the fiberglass- gel coat vs wax coat. Can anyone make a quick recommendation?

3. The camper is basically a 6.5ft wide x 6.5 ft tall x 12ft long box. I want to keep the overcab profile as aerodynamic as possible (I understand the irony of the statement) I do not want to sleep over the cab- so it will just be storage space. The designs I have seen on most modern campers have a slight rise to the roof line to make it a bit tear drop shaped. Do you think this helps at all? When you look at the front of the truck I am trying to decide if the overcab portion should just be a flat upward sloped angle or a curve? Is there a difference for aerodynamics?

4. I am going to attach the overhang of the camper to the top of the cab of the truck. My plan was to use a rubber gasket and silicon to make this connection so that the camper doesn't actually sit on the roof of the truck, but prevents air flow and (hopefully) water from getting into the space between the truck and camper.
Question: Any brilliant ideas for how to make this seam work?

*Sorry for the lack of pictures for the concept. I can't draw to save my life...

Thanks for the input and looking forward to sharing build pics and lessons learned as I lay into this project...

 

[java]

Q1: yes you will have issues, they frames flex a lot. Welding to the frame is not a good attachment method. Yes I realize the frame seems beefy, but it will move, trust me. I am betting you will be over 1000lbs..... It adds up FAST.
Newer truck, but look at he cab vs bed.

Q2: It depends. Multi layer? Laying up the flat panels and then corners etc. 2x3oz would be my go to. But I would look at using FRP for the exterior skin.

Q3: aero is going to suck, period. Dont stick out past the "windshield line" and angle back. Curve will add too much complexity IMO.

Q4: see Q1, you will need some space.... Dont attach it to the cab. Mine moves a good 2" easy with a 4' overhang. I used an accordion gasket from unigrip for my crawl thru.

 

[pappawheely]

I used to have a fiberglass shell on my 92 obs. I switched to a metal shell that is much more rigid. I bolted the shell to the bed and put a bead of silicone around the inside and out to seal it from dust and rain. The bed flexes so much more than the shell that it broke that bead of silicone all the way around. The only way I would weld to the frame is if you had enough structure to completely negate any flexing of the frame like a full cage. Otherwise, it will tear it apart. Offroad race trucks use a rigid frame that is computer designed to be rigid. They see cracks that have to be repaired all the time. With a factory frame, you are stuck with a lot of flexing. Check out this thread to get ideas for an articulating mount. https://www.expeditionportal.com/forum/threads/pivoting-frames-and-mounting-campers.25494/

 

[Victorian]

In my expirience you will have a VERY hard time staying below 1400lb. Our 12 composite camperbox is empty ~900lb. The interior is very basic and functional but I still managed to need 5 sheets of 4x8 plywood. Add the hardware, batteries, waterjugs, camping gear and personal items and you will reach the 1400 pounds in no time. One thing you should avoid at all cost: overload your vehicle.

 

[B85]

Builders need to look at glass panels to build from.

http://www.coosacomposites.com/

https://www.merrittsupply.com/product/coosa-nautical-15-series-composite-board/

 

[b dkw1]

Toyotas have boxed welded frames which are not heat treated.
Ford's have C section heat treated frames.

Do not weld on the Ford frame unless you want a whole bunch of cracks.

Bolt it on with 3 mounting points. 2 by the cab and one in the center in the rear to deal with the frame flex.

 

[Jo_Duval]

If no serious off-road is intended I wonder if you could use the bed box body mounts or if you should go more like a cube van mount.