Panel mounting, lmproving bonding.

[dorkins]

As we are now in a warm spell of weather I am now fixing my 400w panel, being quite large and heavy I am looking at ways to improve the bonding (no screws or bolts into the roof), have looked at a wealth of information on this, I have used the ABS mounts as supplied by Bimble (along with the panel) in hindsite I would have looked more into ally mounts but too far gone down the plastic route. Looking at the very flat surfaces of the mounts, recommendations are to super clean and lightly abrade both mounts and roof (fibreglass) so far so good, my question is would it improve the bonding strength to actually drill say 4mm holes through the mounts, say 4 per corner amount so that the adhesive would push up through these holes to form a "pillar" within the mounts also how about "dimpling" the bottom of the mounts with say a 2mm drill going in by about 1mm?
The recommendations for adhesive thickness is anything between 3mm and 6mm, from reading other posts it seems that tile spacers are often used but has their been any experience of the adhesive sagging between these spacers? and has anyone found more suitable spacers deeper that 3mm?

For the record I am using CT1 adhesive and Multisolve CT1 solvent for cleaning and preparation as supplied by Bimble.

Your thoughts and comments, as usual, would be very much appreciated!

 

[Lenny HB]

Yes holes will help a bit.
I don't know anything about CT1 but have you checked with the manufacturers that it is suitable for the type of plastic you are bonding to?

With Sikaflex only certain ones of their range are suitable for plastics. Most of the panels that have come off Motorhome roofs have had plastic brackets fitted with the incorrect adhesive.

 

[Raul]

According to CT1 site, it sticks to all plastics except polypropylene.
I have used the plastic mounts on a horse box with a small 90w panel to maintain the batteries. Maybe not all mounts are the same, but, the ones I used are not completely flat underneath, only the outside 15mm edge, and the rest is hollow. That made me use one screw per mount to reinforce the fixing. Maybe not needed, but the roof is likely to brush low branches on the lanes and could dislodge the panel. So far no problems. Also the CT1 will take well over 48hrs to fully cure over 3mm bed. For bonding try to keep the bed to 2mm.

 

[jongood]

As we are now in a warm spell of weather I am now fixing my 400w panel, being quite large and heavy I am looking at ways to improve the bonding (no screws or bolts into the roof), have looked at a wealth of information on this, I have used the ABS mounts as supplied by Bimble (along with the panel) in hindsite I would have looked more into ally mounts but too far gone down the plastic route. Looking at the very flat surfaces of the mounts, recommendations are to super clean and lightly abrade both mounts and roof (fibreglass) so far so good, my question is would it improve the bonding strength to actually drill say 4mm holes through the mounts, say 4 per corner amount so that the adhesive would push up through these holes to form a "pillar" within the mounts also how about "dimpling" the bottom of the mounts with say a 2mm drill going in by about 1mm?
The recommendations for adhesive thickness is anything between 3mm and 6mm, from reading other posts it seems that tile spacers are often used but has their been any experience of the adhesive sagging between these spacers? and has anyone found more suitable spacers deeper that 3mm?

For the record I am using CT1 adhesive and Multisolve CT1 solvent for cleaning and preparation as supplied by Bimble.

Your thoughts and comments, as usual, would be very much appreciated!

The thing that would concern me most with a panel that large on a motorhome is the scope for flexing, I would also be worried about the air pressure as you can't really insure that their trajectory is flat in motion. I would be looking to make a framework to add some suport to the middle along with multiple adhesion points and yes definitely a few holes for whichever adhesive to ooze through.

 

[Lenny HB]

Also what van are you fixing to, as you said it was GRP. Hymer have a GRP panel fixed to the aluminium roof where as Rapido have a floating GRP roof. I would have thought a 400 watt panel too big for a safe fitting on a floating roof.

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[dorkins]

Thanks to all.
Lenny - CT1 guff does claim it is excellent for bonding plastics but I will double check, from what I have read so far CT1 seems to have the edge, over Sikaflex even their 292i but I may yet change my mind!
The van is a 1999 vintage Swift Royale, the roof is GRP, it has slightly raised 4" ? bands alternating with slightly lower bands running the length, it does appear to be a very solid roof, very little deflection even when I have had to crawl over it. In the past a couple of things have been screwed to it, since removed and filled so even tho' I don't like the idea of screwing the panel mounts it is a last resort option.

Raul. The mounts are ABS, same as the ones you describe but I will double check with CT1. whether their adhesive is recommended. The 48 hour cure time is not a problem, can you expand on your recommendation of a 2mm bed rather than a deeper one?

Jongood. The panel is actually quite rigid within it's ally frame, I intend to add additional mounting points, if additional supports were added to the middle I would be a bit concerned they may be points that shock could betransmitted to the panel, would a small amount of "give" be better or perhaps a supporting pyramid or two of sealant like material? The panel is 72" x 41" (apologies to the metrics reading this) or am I now over thinking this?

I might now look at ally mounts as this seems to offer better mounting and air deflection options.

 

[walburga]

Last couple of motorhomes that I installed panels on I made my own Aluminium brackets, approx. 100mm long, self tapped these to the alu frame of the panels, drilled 4 holes through each of the brackets, sat the whole lot on cleaned and scratched surface of the van roof, on 3mm plastic spacers, on a good thick bead of adhesive mastic bought from Screwfix. I watched as lots of the adhesive spilled out through the bracket holes, I was happy that this method gave the installation added stiction. I cleaned the overspill from under the brackets (there was quite a bit) to make it all look tidy.

Job done.

 

[TinaLes]

I also used the white plastic panel mounts on my van, one large in each corner, plus another 2 for the middle.
I used white Sikafix and having roughed up the mating surfaces of the brackets and the GRP roof, I placed the panel, marked around the bracket edges with a pencil, before I placed masking tape on the roof about 6mm outside the pencil marks, this enabled me to make a really neat mastic joint around the brackets, after smoothing with wet finger, and peeling off.
LES

 

[Raul]

The 2mm bed it just for drying time, similar to bonding windows. I tend to believe the ally brackets will be better in offering more contact surface with the roof. As for the middle of the panel, it really needs to flex, I would not support the middle, let it expand and contract with change in temperature. The glass and frame is designed to take huge snow loads anyways.

 

[Bessy765]

You might consider if space allows placing a wind deflector that is slightly high the the panels, this would help deflect the 50 or so mph wind force from trying to lift the panel

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[dorkins]

The 2mm bed it just for drying time, similar to bonding windows. I tend to believe the ally brackets will be better in offering more contact surface with the roof. As for the middle of the panel, it really needs to flex, I would not support the middle, let it expand and contract with change in temperature. The glass and frame is designed to take huge snow loads anyways.

good point!

 

[dorkins]

You might consider if space allows placing a wind deflector that is slightly high the the panels, this would help deflect the 50 or so mph wind force from trying to lift the panel

It will sit behind the big sky light, not sure if this would act as a deflector or whether turbulance could have a negative effect! now seriously thinking that the front edge be mounted on an ally mount spanning the full width, this would also act as a deflector, also using the ally mounts along the two long sides and the remaining short side but also using the ABS corner mounts, this I think, would give me the best of all worlds, particularly as the ally mounts apparently bond better than ABS, thinking on this please!

 

[Bessy765]

With lots of brackets on one panel, remember the roof will hopefully if we get any expand in the sunshine of you have a mount across the from and two corner mounts across the rear this will allow some flexing of the frame. I always used to fit them with a slight coward angle in the direction of travel this had two advantages the coward pressure as driving forwards and allow some air to circulate when parked up in hot weather. Solar panels loose some efficiency when they get hot.

 

[Bessy765]

Bloody spell check

 

[dorkins]

Thanks all for the advice, I have decided to go with the original ideas plus upgrades! I am going to use a mix of ABS (corners) and ally on the ends and sides along with an additonal deflector across the front, I am sticking (no pun intended!) with the CT1 adhesive as a 3mm bed.
Fingers crossed.

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