Need Fiberglass Foam Core Panel Recommendation

[Peter_n_Margaret]

A few people have asked me to post the pics I mentioned earlier. I will put them up in a few groups.
Bear in mind that these are 9 year old comments on a build that was done 14 years ago. Materials and ideas have moved along since then.


Another tip with drawers.
It is normal to make drawer runners "flat", but it is better if they slope backwards (down hill) slightly as that tends to keep them closed as the vehicle rattles along bad roads and that takes load off the catches.

This is a normal, commercially available compressor fridge. It has a remote compressor which is in a cupboard nearby. That means that the back, sides, top and bottom can have much more insulation which significantly reduces the power consumption. Some day I will get around to adding more insulation to the door too.
There is no external ventilation either, which reduces the opportunities to get dust inside.

EDIT.. The foam core of these panels is polyurethane. I believe it is both structurally and thermally better than polystyrene, but check that with your local suppliers.

More to come.
Cheers,
Peter
OKA196 motorhome.

 

[Peter_n_Margaret]

Next batch....


I used a cheap drop saw fitted with an aluminium blade to get accurate cuts in the extrusions.

There are 2 sizes of the compression latch I used. I chose the smaller but in hindsight I wold probably use the larger one next time.
You will notice one with a red bit on it a couple of pics back. I modified a few so they could be opened from the back side. There is an emergency crawl-through from the camper section to the cab through a wardrobe and 2 way access was required.

More to come...
Cheers,
Peter
OKA196 motorhome

 

[Peter_n_Margaret]

Next lot....


Getting stuff off that has been glued on with Sikaflex is in fact quite easy. The most convenient way is to cut the glue with a vibrating "multi-tool".
I believe it is also possible to drag a fine wire or even dynema fishing line through it if you cab get it around the glue joint.
Also, the pop rivets in the windows were totally unnecessary.


That's the lot. I hope they provide some inspiration to someone.
Cheers,
Peter
OKA196 motorhome

 

[turbothrush]

Much appreciated. Very helpful Thanks

 

[J!m]

Wow. That is one SERIOUS DIY project!

Nicely done!

 

[Peter_n_Margaret]

Another small tip that took me a while to learn Not covered in the earlier pics.
Attaching all but minor things to sandwich panel can cause high point loads which are not a good idea for the thin skins, but there are a couple of techniques to overcome this.
First is for medium loads. I use this method for things like fire extinguishers and the like. The pic is for a smaller load that is regularly attached and removed so I have glued a piece of flat aluminium onto the skin with Sikaflex 11FC that has a riv nut (clinch nut) attached to it. The threaded section is recessed into a hole in the panel. Depending on the extent of the load, the size of the aluminium patch can vary accordingly.
This one is in an outside storage area, so not very neat , but you get the idea....

Second is for more serious loads.
My spares weigh 80kg each. They and the hoist for getting them up and down are attached to a steel frame on the outside of the sandwich panel. That frame (that you can see) is bolted to a steel body rail at the bottom and to another steel frame (that you can not see) that is glued to the inside of the panel at the top. In this case that frame inside although made from quite light tube, is quite extensive to take the loads, but the eventual aim is to spread the load over a wide area of sandwich panel.
There are spacers going through the panel to stop the panel from being crushed when the bolts are tightened.

Cheers,
Peter
OKA196 motorhome

 

[Paredneck]

I have received three samples of panel materials. All were fairly representative of the model that would be used for the walls. I am currently building mock angles and panels with the samples, but they are all a little too small. I plan to purchase larger boards (4'x8') of the exact model that I would use for more representative testing.

I continue to research companies that could build the entire shell and paint to match my truck. Cost will be $10-20K. PM me if you are interested - perhaps we could get a better deal buying two shells if they are the same. My truck is a 2014 F350 longbed.

did you look at a complete kit from total composites?

 

[bapple]

I have considered Total Composites and requested/received a quote. Very nice guys and definitely know what they are doing. I prefer a more contoured appearance and couldn't get over the limited number of angles they offer.

Short update and thanks to all for informative and inspiring posts.

After too much R&D, I concluded that it is very feasible but not practical to build a structural shell. Concerns began when I tried to find structural data for the numerous off-the-shelf composite panels on the market. No manufacturer had (or was willing to share) structural data. Any company willing to stand behind their engineering claims was only interested in custom work – that was simply too expensive and more appropriate if I was building an airplane.

So I built test rig in my shop to measure deflection under different loading conditions. I selected the most-likely panel system and ran a few tests. My results were surprisingly close to the predictions of the (very smart and way underpriced) engineer I had hired to help with the analysis. With this information, we built a full finite element analysis of my shell design. The snapshot from the report (below) shows we had to simplify the design to use only flat planes.

My test conditions were pretty much pulled out of thin air. I estimated a max load of 1,000 lb in the cabover while stationary, and 500 lb while driving. Max speed of 100 mph and max crosswind of 100 mph. The system is to be mounted to a 2017 F350 with a payload capacity of 4,008 lb. We accounted for the properties of the suspension that Ford is willing to publish. Our design passed under these conditions with a maximum deflection of 30 mm at the front of the cabover. FWIW, the walls were approx. 2” thick.
When it came time to pull the trigger on ordering panels, I became very frustrated with the supplier. They changed a few of their vague specifications and recommendations, and eventually signaled that they were not confident in my planned use of their product. One honest guy finally confided that they have no engineers on staff and didn’t understand much about structural designs. So with only moderate confidence I decided to go another route.

I designed a similar shell but with better contours and enlisted the help of another smart and underpriced engineer to assist with the design of aluminum frame. Images of the shell are below – these were done in Sketchup so contours do not display so well. We finished the FEA last month and I hope to start welding in the next two weeks. The load conditions are similar but with less weight (750 lb) and max deflection of 20mm is at the front of the cabover. Image of frame is below. And I didn’t do a dynamic analysis because I’m sick of designing and want to start building.

It will be mounted on an Aluma flatbed that I custom ordered without a headache rack.

I will cover flat surfaces with CarbonCore panels, thermally mold foam for curved surfaces, and the wrap key areas with a combination of carbon fiber and fiberglass. Then rolling color-matched U-Pol + glitter and then clearcoat for final finish.

 

[rruff]

I can think of some reasons why you had trouble getting engineering info from panel makers. The best "engineering" for this sort of thing is experience. The structural analysis on the panels or box is trivial and not very important. As you say, "test conditions were pulled out of thin air". The details are what matter. Exactly how the panels are joined for instance, how it is mounted, and how much the truck frame flexes. That's where you will get failures.

Does Carbon Core say it's ok to use wet layup epoxy for structural corners? How does the aluminum frame interface with the panels?

I can understand not wanting a square box. The camper I'm slowly working on has a good amount of contour. The front (cabover) curves from the top and sides to make an aero nose, and the top also curves down in the back. The sides are flat though. All the edges have a radius, but only a couple inches. I'm doing wet layup over 25psi XPS. The floor of the camper is reinforced at mounting points, and mounted directly to the frame with urethane isolators.

 

[Stuckincitymud]

I have considered Total Composites and requested/received a quote. Very nice guys and definitely know what they are doing. I prefer a more contoured appearance and couldn't get over the limited number of angles they offer.

Short update and thanks to all for informative and inspiring posts.

After too much R&D, I concluded that it is very feasible but not practical to build a structural shell. Concerns began when I tried to find structural data for the numerous off-the-shelf composite panels on the market. No manufacturer had (or was willing to share) structural data. Any company willing to stand behind their engineering claims was only interested in custom work – that was simply too expensive and more appropriate if I was building an airplane.

So I built test rig in my shop to measure deflection under different loading conditions. I selected the most-likely panel system and ran a few tests. My results were surprisingly close to the predictions of the (very smart and way underpriced) engineer I had hired to help with the analysis. With this information, we built a full finite element analysis of my shell design. The snapshot from the report (below) shows we had to simplify the design to use only flat planes.

My test conditions were pretty much pulled out of thin air. I estimated a max load of 1,000 lb in the cabover while stationary, and 500 lb while driving. Max speed of 100 mph and max crosswind of 100 mph. The system is to be mounted to a 2017 F350 with a payload capacity of 4,008 lb. We accounted for the properties of the suspension that Ford is willing to publish. Our design passed under these conditions with a maximum deflection of 30 mm at the front of the cabover. FWIW, the walls were approx. 2” thick.
When it came time to pull the trigger on ordering panels, I became very frustrated with the supplier. They changed a few of their vague specifications and recommendations, and eventually signaled that they were not confident in my planned use of their product. One honest guy finally confided that they have no engineers on staff and didn’t understand much about structural designs. So with only moderate confidence I decided to go another route.

I designed a similar shell but with better contours and enlisted the help of another smart and underpriced engineer to assist with the design of aluminum frame. Images of the shell are below – these were done in Sketchup so contours do not display so well. We finished the FEA last month and I hope to start welding in the next two weeks. The load conditions are similar but with less weight (750 lb) and max deflection of 20mm is at the front of the cabover. Image of frame is below. And I didn’t do a dynamic analysis because I’m sick of designing and want to start building.

It will be mounted on an Aluma flatbed that I custom ordered without a headache rack.

I will cover flat surfaces with CarbonCore panels, thermally mold foam for curved surfaces, and the wrap key areas with a combination of carbon fiber and fiberglass. Then rolling color-matched U-Pol + glitter and then clearcoat for final finish.

Curious how things have progressed since moving to construction from analysis. Side note on the AL frame, I would have put the X members the other direction in the cab-over section so they are in compression instead of tension.

 

[awheeler]

Take a look at Coosa Composites. I have and am considering it.
http://www.coosacomposites.com/

I'm also using Coosa for our interior build. Just starting the build so I don't have a lot of feedback yet but so far it's pretty easy to cut and work with.

 

[kcshoots]

I'm also using Coosa for our interior build. Just starting the build so I don't have a lot of feedback yet but so far it's pretty easy to cut and work with.

How do you plan on covering the Coosa? Since it's a polyurethane, Coosa says it take PU-based paint very well, such as a bed-liner style paint.

 

[awheeler]

How do you plan on covering the Coosa? Since it's a polyurethane, Coosa says it take PU-based paint very well, such as a bed-liner style paint.

Coosa recommended Kilz 3 primer and then whatever interior paint. The boards do you have some imperfections which I will just fill in with bondo if needed.

 

[reddrum]

I have considered Total Composites and requested/received a quote. Very nice guys and definitely know what they are doing. I prefer a more contoured appearance and couldn't get over the limited number of angles they offer.

Short update and thanks to all for informative and inspiring posts.

After too much R&D, I concluded that it is very feasible but not practical to build a structural shell. Concerns began when I tried to find structural data for the numerous off-the-shelf composite panels on the market. No manufacturer had (or was willing to share) structural data. Any company willing to stand behind their engineering claims was only interested in custom work – that was simply too expensive and more appropriate if I was building an airplane.

So I built test rig in my shop to measure deflection under different loading conditions. I selected the most-likely panel system and ran a few tests. My results were surprisingly close to the predictions of the (very smart and way underpriced) engineer I had hired to help with the analysis. With this information, we built a full finite element analysis of my shell design. The snapshot from the report (below) shows we had to simplify the design to use only flat planes.

My test conditions were pretty much pulled out of thin air. I estimated a max load of 1,000 lb in the cabover while stationary, and 500 lb while driving. Max speed of 100 mph and max crosswind of 100 mph. The system is to be mounted to a 2017 F350 with a payload capacity of 4,008 lb. We accounted for the properties of the suspension that Ford is willing to publish. Our design passed under these conditions with a maximum deflection of 30 mm at the front of the cabover. FWIW, the walls were approx. 2” thick.
When it came time to pull the trigger on ordering panels, I became very frustrated with the supplier. They changed a few of their vague specifications and recommendations, and eventually signaled that they were not confident in my planned use of their product. One honest guy finally confided that they have no engineers on staff and didn’t understand much about structural designs. So with only moderate confidence I decided to go another route.

I designed a similar shell but with better contours and enlisted the help of another smart and underpriced engineer to assist with the design of aluminum frame. Images of the shell are below – these were done in Sketchup so contours do not display so well. We finished the FEA last month and I hope to start welding in the next two weeks. The load conditions are similar but with less weight (750 lb) and max deflection of 20mm is at the front of the cabover. Image of frame is below. And I didn’t do a dynamic analysis because I’m sick of designing and want to start building.

It will be mounted on an Aluma flatbed that I custom ordered without a headache rack.

I will cover flat surfaces with CarbonCore panels, thermally mold foam for curved surfaces, and the wrap key areas with a combination of carbon fiber and fiberglass. Then rolling color-matched U-Pol + glitter and then clearcoat for final finish.

Curious, did you move forward with this? How did it work out? I am about to begin a similar build with similiar ideas for building techniques. I would love to hear anything you have learned, good and bad.