cracking solar panel mounts

[krick3tt]

Just a thought, I made some brackets from aluminum for mounting on my M416 trailer. The vibrations of off road driving caused them to crack at the bends. I made some from flat plate steel and the issue was solved. The idea of making the brackets for your use from fiberglass may be much better than any other material as there would possibly be some flex to them.

 

[tanuki.himself]

If it is an an airflow issue, it becomes a matter of tuning that flow. Sometimes it is as easy as a crude air damn in front. Years ago I was assigned a new patrol vehicle. When driven at highway speed the light bar would generate all Kinds of noise against the thin roof from the airflow. In the end moving a couple of inches was all it took to make the problem go away. Since it sounds like Winter is taking you off the road for the season, is it possible to pull one corner and one center mount and make them into molds to recreate the mounts in stronger fiberglass?

The problem is the height of the camper now it is on the truck, and the strength of the sikaflex 252 glue i stuck the mounts down with. When i had the camper on the floor the roof is over 2m above ground and in my rented accommodation i don't have big ladders, so it was as high and as far over as I could reach. Now the camper is on the truck its 3m to the roof line, so even more inaccessible, I cant get a rented access tower or anything around it and i don't have level ground that i can easily demount it again - now its fitted out its too heavy to try and manhandle back to where i built it. I can take it to some local public land and demount it for a few hours, but then i only have the use of hand and battery tools, so no pneumatic glue gun or oscillating cutter.

The other issue is that there is quite a thin layer of glue between roof skin and the mountings, and my experience of cutting this glue apart on a couple of other areas is that it is extremely tough and it is all too easy to end up cutting into the material you are trying to preserve - in the case the 2mm fibreglass roof skin. Even with easy access and plenty of time I would be vary wary of doing this and damaging the roof. i think adding some additional fibreglass inverted T brackets to act as tie downs is going to be a safer and easier bet.

I am thinking that if I can feel vibrations when being driven then i can try sticking some foam wedges of different sizes and shapes in front of the panels to find a way to stop the airflow, and once i have a working design i can make it in fibreglass....

 

[tanuki.himself]

Just a thought, I made some brackets from aluminum for mounting on my M416 trailer. The vibrations of off road driving caused them to crack at the bends. I made some from flat plate steel and the issue was solved. The idea of making the brackets for your use from fiberglass may be much better than any other material as there would possibly be some flex to them.

Fibreglass tends to be my goto material as i've now got quite a bit of experience with using it, and i have some better than bog standard tapes and fabrics that can make it a lot stronger then chopped strand matting for certain applications. Plus its glues well with the sikaflex 252 i have - my understanding is that aluminium is difficult to clean and glue well without serious chemicals which I don't have or know where i can buy locally :-(

 

[Kmrtnsn]

I think that if you feel buffeting on the test then you’ll have found your culprit. I’d the fab up some simple aluminum sheet metal spoilers to mount between the roof and the front edge of the panels. If that solves the issue and you’re confident in the mounts after that point a simple metal reinforcement bonded to the existing mounts might well cure your problem with their cracking. A good epoxy over them with a bonded reinforcement might suffice. Best of luck. Anxious to see how this turns out.

 

[NatersXJ6]

I’m thinking part of your issue was not tightening the screws, part was not spreading load with big washers. The panels don’t change size much in the heat to cold cycles, and any such change would have been made up by flex in the mount.

 

[Man]

If you don't think it could be from lift, did you consider twist? To me it looks like the cracks formed from lift as if someone pulled up on the panels, but if you were driving slow there wouldn't be enough force. Maybe articulation caused the damage?

 

[Alloy]

Kind of irrelevant, and not knowing the plastic type ( I suspect a PVC of some kind ) or examine them in person.
If ruled out fastener stress, I suspect crappy job of injection moulding.
Plastic moulding is art science and dumb luck rolled into as many parts possible per hour from very expensive machine.
Getting the temperature, pressure, time, sprue locations wrong can create parts what initially look ok but contain coldshuts and internal stresses.
Its easy in speculation a company making small batch solar fittings may not have their moulding process dialed in as perfectly as a company making thousands daily of pipefittings or mousebuttons for example.

....and who knows if the company added UV stabilizer.........only plastics I expect to last outside are black.

 

[tanuki.himself]

If you don't think it could be from lift, did you consider twist? To me it looks like the cracks formed from lift as if someone pulled up on the panels, but if you were driving slow there wouldn't be enough force. Maybe articulation caused the damage?

its possible - i was going over some big potholes and dips down by the beach, but the camper box itself seems pretty rigid with no signs of movement on any of the joints, and it should move with the tub

 

[tanuki.himself]

I've now made my additional fibreglass tie down brackets from some woven tape i had left form my frame build, layered with CSM and formed over a piece of 5mm core material (also left over from other jobs). This tape is pretty strong - i can hang my weight off a single loop of it - so hopefully it will resist any cracking or pulling through of the screw. Obviously it will only be as strong as the glue holding it to the roof so i'll be using the same sikaflex 252 as i still have some and don't know of anything stronger, I'm going to use some 5.2mm stainless flange head self tapping screws and 20mm penny washers as the widest thing i can find locally, and will put a layer of 4mm draught excluder foam between the bracket and the frame to allow for any thermal expansion.