An article written in the Grey Nomads web page suggested that solar panel mounts should not be just glued to the vehicle roof, but should be glued and screwed. As far as I am concerned, this advice is incorrect, and that a properly glued joint is better than a screwed and perhaps poorly glued joint.
I might suggest the author of the article never buys a composite constructed caravan, nor travel in another aircraft, both have fully glued components. More to the point is that a poorly glued joint would be worse than a screwed and glued joint, but properly done, the glued joint, using the correct materials, the correct engineering, is far stronger.
If one fitted the solar panel mounts, so that the fasteners screwed into a wooden or alloy rib or joist that was on the other side of the cladding (i.e. a bit of meat for the screws to screw into), then that would be strong, but self tapping screws into thin cladding alone would have very little strength, and the brittleness of fiberglass would be likewise (in my opinion).
It really is horses for courses, as the engineering of each installation would be different, and consideration of the structure would dictate how the attachment should be made. The solar panel mounts I have installed have been glued, no screws to attach the mounts to the roof of the van, it was done in accordance with Sika-Flex instructions (available at their web site) for attaching solar panels. The important thing to remember is that a glued joint relies on area, so in my case I made up pads to increase the surface area between the van roof and the mounts, The mounts were bolted to the pads, and the pads glued to the roof.
The important factor in all this, re solar panels coming adrift when driving, is that as part of the inspection or service (yearly at least), the security of the solar panels should be checked, regardless of how they are attached.
What is the advantage of gluing only, no holes in the roof.
Warren-Pat_01 said
12:55 PM Oct 22, 2020
Got some spare time on your hands, Ian?
There has been lots written on this subject over the years as I'm certain you've read. My single (small 60w) panel is glued to the roof via mounts bought from Jaycar. These have quite large feet giving adequate grip to the roof- it is the strength of the roof that really worries me! There ain't much there, mate!!
There has been more talk in the media recently about accidents on the Bruce Highway that have been caused by flying panels coming loose and ...... .
PeterandMargaret have a good setup with what looks like flexible panels attached to their window shields on their Ocka but these get hot if no air gap is left between the two panels, reducing efficiency.
I'm waiting for the "ultimate" solution to come out - painted solar! Tests were done years ago in the USA, what came of them I don't know. Possibly another "heat" problem or perhaps the Asian solar panel companies put them the out of business.
Whenarewethere said
01:21 PM Oct 22, 2020
Sydney's Tangara trains are held together with double sided sticky tape. It was the only way to get nice smooth panels.
Whenarewethere said
01:27 PM Oct 22, 2020
When gluing apart from cleaning property. Give the adhesive time to dry.
In the window industry. Glass bonded into frameless panels needs a month for the adhesive to set because it is 30mm thick as it takes about a day per mm to set.
Wanda said
04:54 PM Oct 22, 2020
Arguments for both, whats the problem, neither is wrong, bit like which is better Holden(remember them) or Ford
Slow news day
Ian
iana said
05:46 PM Oct 22, 2020
Warren-Pat, you bring up the exact point, the tear-out strength of the surface that the solar panels mount to. While self tappers may have a high tensile strength, there grip strength is dubious depending on the thickness of the material they screw into, and the "Tear out" strength of alloy cladding or thin fiberglass is poor. That is why a large glued joint is better in both the latter cases, spreading the load over a large surface.
As for time on my hands yes I have a bit, just can't put it to productive use.
Ian
Whenarewethere said
05:58 PM Oct 22, 2020
Install a downforce defuser to stop panels lifting. I'm sure a bit of hunting around one could modify a few extrusions without too much difficulty.
Whenarewethere said
06:35 PM Oct 22, 2020
This is a standard coolroom shape. Use it vertically with spacer on the rear of the panel. Screw it on back the front on the leading edge of the panel.
I'm sure there are better profiles, but it is a start & it's anodised.
A number of people have mentioned the importance of the type of roof substrate to an effective bond, but equally important is the material the mounts themselves are constructed from. Quality mounts are made of ABS plastic which common adhesive/sealants readily bond to, but this isn't the case with some inferior products being sold on eBay.
I bought some very common mounts from Ebay, advertised as being ABS, but when they arrived they were made of a translucent waxy type of plastic that I suspect was polyethylene. As anyone who has tried to mend a polyethylene kayak or kids toy will know only too well, it is almost impossible to get anything to bond to polyethylene. So, I did an experiment of trying to glue two of them together with three common flexible adhesives used in the RV industry - Sika, silicon, and a polyurethane adhesive sealant. None of them would bond to the mounts and they could be easily pulled apart! The same would have happened if I'd attached them to my roof!
I wrote to the seller and asked what they were made of and what adhesive they advised, but by their reply it was clear they didn't have a clue, and cared little. So, I sent them a picture of my little experiment (same picture as below) and explained they were unsafe for the purpose advertised and recommended they withdraw them from sale, which they completely ignored, just offering me a discount! Unfortunately it seems many eBay sellers just jump on the bandwagon of whatever's trending popular at the moment, but have little knowledge about the design requirements and intended use of the products they are selling.
I left a comment on the seller's page warning others about the product and consigned mine to the bin where they belonged, and bought proper ABS mounts from Jaycar for about three times the price. I was happy that I'd dodged a potential bullet, but hate to think how many of these mounts are already in use and are an accident just waiting to happen.
I'm not suggesting the terrible accident recently was as a result of inferior quality mounts, we will only know the cause of that one was when the results of the investigation are released, but I just wanted to warn anyone buying mounts that they should test them with their intended adhesive first to make sure they are compatible and will form a strong bond.
Using Sikaflex glazing structural silicone graph as a guideline. If the distance of the silicone is 10mm from the air it needs about 10 days to cure.
The solar cell pads have a greater distance to the centre of the pad so the silicone will need longer to cure. If it is 30mm to the air (outer edge of pad) the silicone needs 30 days to cure.
Thanks all - I've found this to be an instructive thread.
I had no idea about the adhesive/polyethylene issue and I would never have thought of the downward wind deflection idea.
iana said
01:50 PM Oct 23, 2020
Okay there is another thing equally important, fiberglass can have a release agent on its surface, the part to be glued may have something similar, it is important to remove all traces of this, and then lightly rub the surface with emery paper or similar to create a surface profile for the adhesive to stick to.
I would not consider putting any thing into the airstream, to get any sort of down force, you would need an inverted aero foil i.e. F1 cars, what was proposed is a spoiler, mainly causing drag, and upping the fuel bill.
Peter_n_Margaret said
01:55 PM Oct 23, 2020
Polyethylene (and polypropylene) should generally be considered "un-glue able" for all intents and purposes. It is a bit like trying to glue a candle stick. There are some glues that claim some success, but personally I would never trust them.
Likewise, painting these plastics is problematic. It can be done by chemically etching the surface to create a bond as is done with car bumper bars, but not with 'normal' paints directly.
Both can be hot air welded, spin welded and ultrasonically welded to themselves though.
Cheers,
Peter
iana said
02:01 PM Oct 23, 2020
Agree, how I over come that was to make up fiberglass pads, bolting the mounts to the pads, and then gluing the pads to the caravan roof.
F1 cars, what was proposed is a spoiler, mainly causing drag, and upping the fuel bill.
I'm not suggesting 1000kg downforce.
It's more of a minor tweak to have a clean airflow over the top. It might even improve airflow in general.
Gravy73 said
04:13 PM Oct 23, 2020
You might like to communicate with the owners of the caravan that had a solar panel depart the van here in Tassie recently, it resulted in the death of another motorist.
Only way to ensure proper security of panels is to bolt them to a frame that straddles the full width of the van, frame is attached to the edge of the van via angle brackets fixed with threaded inserts into the sides of the van. This places the bolts in shear rather than tension so there is less tendency for the screws to pull out of the cladding material.
You dont see solar arrays fixed to buildings using glue.
The bonus with this method is there is air circulation under the panels, this results in less efficiency loss due to heat.
Aus-Kiwi said
04:52 PM Oct 23, 2020
Why I used long alloy L section so secure . My dwelling has 7 ply with rubber sealing roof . The holes that secure to panel is larger with big stainless washer to allow some expansion , movement or it breaks away . I used Sikoflex and stainless screws . On other surfaces Like alloy . I use an extra 2mm plate Sikoflexed and riveted to body . Then rivnut through the whole roof with Sikoflex .
PeterInSa said
08:08 PM Oct 23, 2020
This is the method used on our Tandem Van
(Only way to ensure proper security of panels is to bolt them to a frame that straddles the full width of the van, frame is attached to the edge of the van via angle brackets fixed with threaded inserts into the sides of the van. This places the bolts in shear rather than tension so there is less tendency for the screws to pull out of the cladding material.)
Warren-Pat_01 said
09:15 PM Oct 24, 2020
Before I put the mounts with the panel on my roof, I gave both the mounts & the section of roof a good clean with wax remover.
Frames probably are a better way, but that adds more weight & those of us with single axles don't have much of that to spare.
Mariner30 said
03:26 PM Oct 26, 2020
Gravy73 wrote:
You might like to communicate with the owners of the caravan that had a solar panel depart the van here in Tassie recently, it resulted in the death of another motorist.
Is that the recent one on the Midland Hwy?
If so, three people died as a result of the solar panel detaching from the van roof,
One of them was a child.
Gravy73 said
04:31 PM Oct 30, 2020
Correct
mischief said
08:43 PM Nov 3, 2020
agree with peter in sa ..went the same way on frame with six panels up there,,all mounting to the outside frame.
An article written in the Grey Nomads web page suggested that solar panel mounts should not be just glued to the vehicle roof, but should be glued and screwed. As far as I am concerned, this advice is incorrect, and that a properly glued joint is better than a screwed and perhaps poorly glued joint.
I might suggest the author of the article never buys a composite constructed caravan, nor travel in another aircraft, both have fully glued components. More to the point is that a poorly glued joint would be worse than a screwed and glued joint, but properly done, the glued joint, using the correct materials, the correct engineering, is far stronger.
If one fitted the solar panel mounts, so that the fasteners screwed into a wooden or alloy rib or joist that was on the other side of the cladding (i.e. a bit of meat for the screws to screw into), then that would be strong, but self tapping screws into thin cladding alone would have very little strength, and the brittleness of fiberglass would be likewise (in my opinion).
It really is horses for courses, as the engineering of each installation would be different, and consideration of the structure would dictate how the attachment should be made. The solar panel mounts I have installed have been glued, no screws to attach the mounts to the roof of the van, it was done in accordance with Sika-Flex instructions (available at their web site) for attaching solar panels. The important thing to remember is that a glued joint relies on area, so in my case I made up pads to increase the surface area between the van roof and the mounts, The mounts were bolted to the pads, and the pads glued to the roof.
The important factor in all this, re solar panels coming adrift when driving, is that as part of the inspection or service (yearly at least), the security of the solar panels should be checked, regardless of how they are attached.
What is the advantage of gluing only, no holes in the roof.
There has been lots written on this subject over the years as I'm certain you've read. My single (small 60w) panel is glued to the roof via mounts bought from Jaycar. These have quite large feet giving adequate grip to the roof- it is the strength of the roof that really worries me! There ain't much there, mate!!
There has been more talk in the media recently about accidents on the Bruce Highway that have been caused by flying panels coming loose and ...... .
PeterandMargaret have a good setup with what looks like flexible panels attached to their window shields on their Ocka but these get hot if no air gap is left between the two panels, reducing efficiency.
I'm waiting for the "ultimate" solution to come out - painted solar! Tests were done years ago in the USA, what came of them I don't know. Possibly another "heat" problem or perhaps the Asian solar panel companies put them the out of business.
Sydney's Tangara trains are held together with double sided sticky tape. It was the only way to get nice smooth panels.
When gluing apart from cleaning property. Give the adhesive time to dry.
In the window industry. Glass bonded into frameless panels needs a month for the adhesive to set because it is 30mm thick as it takes about a day per mm to set.
Slow news day
Ian
As for time on my hands yes I have a bit, just can't put it to productive use.
Ian
Install a downforce defuser to stop panels lifting. I'm sure a bit of hunting around one could modify a few extrusions without too much difficulty.
This is a standard coolroom shape. Use it vertically with spacer on the rear of the panel. Screw it on back the front on the leading edge of the panel.
I'm sure there are better profiles, but it is a start & it's anodised.
So are the walls.
Oh dear, what shall I do?
Cheers,
Peter
My solution is not solely relying on adhesive.
Fastening some extrusions to the leading & trailing edges of the solar panel to create downforce.
Your second form of fastening!
Carry a few big rolls of Gaffer tape?
You'll be right mate, afterall the Ocka can't break the sound barrier, can it?
You are correct.
I used the gaffa tape a few times for broken windows until we changed them from acrylic all to polycarbonate.
Also carried a couple of bits of coreflute for the purpose.
Cheers,
Peter
A number of people have mentioned the importance of the type of roof substrate to an effective bond, but equally important is the material the mounts themselves are constructed from. Quality mounts are made of ABS plastic which common adhesive/sealants readily bond to, but this isn't the case with some inferior products being sold on eBay.
I bought some very common mounts from Ebay, advertised as being ABS, but when they arrived they were made of a translucent waxy type of plastic that I suspect was polyethylene. As anyone who has tried to mend a polyethylene kayak or kids toy will know only too well, it is almost impossible to get anything to bond to polyethylene. So, I did an experiment of trying to glue two of them together with three common flexible adhesives used in the RV industry - Sika, silicon, and a polyurethane adhesive sealant. None of them would bond to the mounts and they could be easily pulled apart! The same would have happened if I'd attached them to my roof!
I wrote to the seller and asked what they were made of and what adhesive they advised, but by their reply it was clear they didn't have a clue, and cared little. So, I sent them a picture of my little experiment (same picture as below) and explained they were unsafe for the purpose advertised and recommended they withdraw them from sale, which they completely ignored, just offering me a discount! Unfortunately it seems many eBay sellers just jump on the bandwagon of whatever's trending popular at the moment, but have little knowledge about the design requirements and intended use of the products they are selling.
I left a comment on the seller's page warning others about the product and consigned mine to the bin where they belonged, and bought proper ABS mounts from Jaycar for about three times the price. I was happy that I'd dodged a potential bullet, but hate to think how many of these mounts are already in use and are an accident just waiting to happen.
I'm not suggesting the terrible accident recently was as a result of inferior quality mounts, we will only know the cause of that one was when the results of the investigation are released, but I just wanted to warn anyone buying mounts that they should test them with their intended adhesive first to make sure they are compatible and will form a strong bond.
Using Sikaflex glazing structural silicone graph as a guideline. If the distance of the silicone is 10mm from the air it needs about 10 days to cure.
The solar cell pads have a greater distance to the centre of the pad so the silicone will need longer to cure. If it is 30mm to the air (outer edge of pad) the silicone needs 30 days to cure.
Thanks all - I've found this to be an instructive thread.
I had no idea about the adhesive/polyethylene issue and I would never have thought of the downward wind deflection idea.
I would not consider putting any thing into the airstream, to get any sort of down force, you would need an inverted aero foil i.e. F1 cars, what was proposed is a spoiler, mainly causing drag, and upping the fuel bill.
Likewise, painting these plastics is problematic. It can be done by chemically etching the surface to create a bond as is done with car bumper bars, but not with 'normal' paints directly.
Both can be hot air welded, spin welded and ultrasonically welded to themselves though.
Cheers,
Peter
Agree, how I over come that was to make up fiberglass pads, bolting the mounts to the pads, and then gluing the pads to the caravan roof.
I'm not suggesting 1000kg downforce.
It's more of a minor tweak to have a clean airflow over the top. It might even improve airflow in general.
Only way to ensure proper security of panels is to bolt them to a frame that straddles the full width of the van, frame is attached to the edge of the van via angle brackets fixed with threaded inserts into the sides of the van. This places the bolts in shear rather than tension so there is less tendency for the screws to pull out of the cladding material.
You dont see solar arrays fixed to buildings using glue.
The bonus with this method is there is air circulation under the panels, this results in less efficiency loss due to heat.
(Only way to ensure proper security of panels is to bolt them to a frame that straddles the full width of the van, frame is attached to the edge of the van via angle brackets fixed with threaded inserts into the sides of the van. This places the bolts in shear rather than tension so there is less tendency for the screws to pull out of the cladding material.)
Frames probably are a better way, but that adds more weight & those of us with single axles don't have much of that to spare.
Is that the recent one on the Midland Hwy?
If so, three people died as a result of the solar panel detaching from the van roof,
One of them was a child.