Solar Panels taking flight - Disaster

[lancepar]

Agree they must be secure but just to be clear.........

 

Solar panels are basicalty a flat plate and if horizontal will only create lift if the Angle of Attack is raised, even then the flow of air over the upper surface would be chaotic, and so would be an infficient wing.

 

Retiring to the Hanger. >:-)

 

B-)

[BKen1]

lancepar - 2018-11-21 1:56 PM

 

Agree they must be secure but just to be clear.........

 

Solar panels are basicalty a flat plate and if horizontal will only create lift if the Angle of Attack is raised, even then the flow of air over the upper surface would be chaotic, and so would be an infficient wing.

 

Retiring to the Hanger. >:-)

 

B-)

Not suggesting the panel will have efficient lift exactly like a wing but the principle still applies turbulance or not there has to be lifting effect all be inefficient and the faster you go the more the lift effect ...

[pepe63xnotuse]

How "standardised" are solar panel sizes across their industry/market?

 

The reason I ask is: What happens if, having gone to all of the trouble of correctly bonding and screwing mounting brackets and "deflectors" onto the roof (all of which "cosset" the panel), the panel later develops a fault or gets damaged and a like for like panel is unobtainable....?

 

Would it not be better to build-in a fair degree of adjustability/adaptability into the whole process..?

 

[BruceM]

pepe63 - 2018-11-21 2:33 PM

 

How "standardised" are solar panel sizes across their industry/market?

 

The reason I ask is: What happens if, having gone to all of the trouble of correctly bonding and screwing mounting brackets and "deflectors" onto the roof (all of which "cosset" the panel), the panel later develops a fault or gets damaged and a like for like panel is unobtainable....?

 

Would it not be better to build-in a fair degree of adjustability/adaptability into the whole process..?

 

I came across this very issue when I replaced by old 100w panel with two new 100w panels so I suspect that the answer to your question is “not very”.

 

My new panels were 6mm narrower than the old panel. If the previous brackets had been plastic I’d have had to remove them using the cheese cutter method. Tedious but very doable.

 

As it happens however the brackets were aluminium (my preferred bracket material) consequently I riveted (and stuck) 3mm spacers each side which also allowed me to provided the correct solar panel clearance from the van’s roof (the previous panel had been mounted flush).

 

So I reckon that although replacing a panel may not be a simple swap out due to minor panel size differences, the additional effort is not necessarily that great. I absolutely agree however that adjustable brackets would be a useful addition to the armoury although I suspect many installers would be put off by the potential cost.

[aandncaravan]

lancepar - 2018-11-21 12:56 PM

 

Agree they must be secure but just to be clear.........

 

Solar panels are basicalty a flat plate and if horizontal will only create lift if the Angle of Attack is raised, even then the flow of air over the upper surface would be chaotic, and so would be an inefficient wing.

 

Retiring to the Hanger. >:-)

 

B-)

 

 

That is true of a panel on a flat surface, but imagine a panel at the front of the vehicle mounted just where air flow rises up the front of the van, increasing in pressure/speed as it rises up the front, eventually hitting the underside of the Solar panel and creating significant lift.

It is possible that a vehicle travelling at 70mph with a 40 mph head wind would have a wind speed hitting the panel well over 110 mph.

 

A similar, but less destructive effect, will be had in a 80mph hurricane on a panel mounted near the edge of the roof or rear of the roof. Again caused by air rising up the van sides. This might be particularly destructive on a 'rounded side' PVC.

 

 

The photos of detached Solar panels on the motorhome fun thread above (i think 4 separate stories of Solar panels taking off, all without mechanical fixings), show one where the adhesive held fast to the panel and the paint on the roof, but took peeled the Paint with it when it went flying, so clearly exceptional forces are acting on the Solar Panels on a motohomes roof.

 

 

The screws we recommend that are used are coating protected, so should last the life of the vehicle. The way we suggest they are used also coats them in the Adhesive/Sealant which should also extend their lives.

 

 

 

[Paul-]

pepe63 - 2018-11-21 2:33 PMHow "standardised" are solar panel sizes across their industry/market?The reason I ask is: What happens if, having gone to all of the trouble of correctly bonding and screwing mounting brackets and "deflectors" onto the roof (all of which "cosset" the panel), the panel later develops a fault or gets damaged and a like for like panel is unobtainable....?Would it not be better to build-in a fair degree of adjustability/adaptability into the whole process..?

You could take the measurements of the panel and shop around, but quite often people go for a bigger panel, in this situation something like a wire hand saw will get the brackets off and one of the reasons I use the foam transit pads as spacers.

[plwsm2000]

I recently ordered some Sikaflex 252i but was sent 252 instead. There is a significant difference between 252 and 252i. The supplier was not aware of the difference so check you have not been sent the wrong stuff!.

 

252i is solvent free (low VOC) and has superior mechanical properties to 252.

(I believe there is also 292 and 292i for marine applications).

 

This website has the specs for 252 and 252i.

[url=] https://hkg.sika.com/en/Solutions%20Products/document_download/PDS_Sikaflex.html [/url]

 

 

[aandncaravan]

Paul- - 2018-11-20 2:58 PM

I find that the foam transit pads that window people use are ideal spacers when cut into 1/8" strips, any window fitter will have them and in different thicknesses  This sort of thing in the link

https://www.wholesaleglasscompany.co.uk/acatalog/Glass-Transit-Pads.html

Paul, I liked this idea but have been contacted by Adhesive expert who suggests an alternative.He uses 6mm petrol pipe from Halfords which he cuts into 3.5mm 'tubes' and then stands them on end in the Adhesive. He can cut the tubes to match the bead of the adhesive being used and it's a cost effective easy to acquire option.Like you he says that because the Adhesive/Sealant is designed to be elastic allowing micro movement a spacer like a bolt head or washer, as recommended by some, might rub on roof causing an eventual hole as well as restricting movements.While he thinks the 'soft' tile spacer option is ok, a rubber/foam option is better.So I think I will update the web page to reflect that, but thank you for your tip, you might be one of the few who have a good Solar installation as you have clearly put a lot of thought into it. .

[Deneb]

I wouldn't have thought there would be any discernable give in a 3.5mm length of reinforced fuel hose, with weight borne through the ends of the "cylinder". A good idea though, but I'd be more inclined to use a length of thinner walled and more flexible washer tubing or similar.

[Paul-]

The high density foam pads are used universally by glass manufactures to protect the glass in transport and come free from window fitters, or the tubing can be bought from Halfords.

 I'm from Yorkshire ;)

 

[Robbo]

My only concern about using spacers is, they may be counterproductive to achieving maximum bond.

 

1) The spacers themselves will reduce the surface area of adhesive between joining surfaces.

 

2) The spacer could prevent full compression of the adhesive, if insufficient adhesive is used.

 

A single 7mm diameter bead of sealant will spread a width of 13mm to achieve a 3mm gap. Allowing for compression of the adhesive material, it would be prudent to allow a 10mm spread width, to be on the safe side.

 

So, no need to use spacers in my view, providing the user calculates the bead diameter/spread width and allows for compression of the adhesive.

 

The 3mm thickness of adhesive, as recommended by manufacturers is a guide, so a little bit more or less (say plus or minus 0.5mm) isn't going to compromise the overall strength of the joint.

 

If in doubt, regarding the amount of adhesive to be used, try out a pre-assembly experiment using one of the supports, preferably using a piece of glass to replicate the roof structure, so you can see the extent of the coverage. I would imagine that adhesives used in industry, in hyper critical applications like airframes and bridges, always carryout their own testing (including testing to destruction) prior to using in the final product.

 

 

[BruceM]

Robbo - 2018-11-23 2:56 PM

 

So, no need to use spacers in my view, providing the user calculates the bead diameter/spread width and allows for compression of the adhesive.

 

 

 

If I understand your suggestion correctly I think that you’re suggesting that to achieve the correct adhesive thickness without spacers the mounts would be dressed with the appropriate amount of adhesive and then pressed down on to the van roof until the sealant just starts to squeeze out the sides?

 

I think that that creates a difficulty. The mounts are normally mounted on to the solar panel prior to being stuck in place on the van roof. Consequently, without spacers the on-going pressure from the solar panel’s weight is likely to squeeze the adhesive out beyond the 3mm recommended figures.

 

 

[Robbo]

BruceM - 2018-11-23 3:40 PM

 

Robbo - 2018-11-23 2:56 PM

 

So, no need to use spacers in my view, providing the user calculates the bead diameter/spread width and allows for compression of the adhesive.

 

 

 

If I understand your suggestion correctly I think that you’re suggesting that to achieve the correct adhesive thickness without spacers the mounts would be dressed with the appropriate amount of adhesive and then pressed down on to the van roof until the sealant just starts to squeeze out the sides?

 

I think that that creates a difficulty. The mounts are normally mounted on to the solar panel prior to being stuck in place on the van roof. Consequently, without spacers the on-going pressure from the solar panel’s weight is likely to squeeze the adhesive out beyond the 3mm recommended figures.

 

 

Correct, except I would apply the adhesive to the roof.

 

The weight of the solar panel would excert a maximum of 2 to 3Kg to each support (50 to 75 grammes/sq. cm). If the adhesive did squeeze out under that weight (giving a gap of less than 3mm), then I would question the flow characteristics of the adhesive being used.

[Paul-]

I prefer to fasten the brackets to the solar panel, then after marking the roof and cleaning in preparation for the panel, I would stick the foam transit pads to the brackets then use the glue to cover all the brackets.

I would then turn the panel over and affix to the roof, this is usually enough to leave a bead of glue proud of the bracket, if not mask the area and use some more glue.

Just as important is the positioning of and the quality of the controller, fit a good quality controller reasonable close to battery (within a metre) and use good quality wire to the battery otherwise expect overcharging.

A good controller will monitor battery charge condition and the ambient temperature and charge accordingly, if there's power loss in the cable it will charge according to what it receives and could overcharge 

 

[aandncaravan]

The web page has today been given the thumbs up by Sika, so I am fairly happy with it, but it might get some minor tweaks over the next week or two. The latest version should be visible tonight sometime.

 

Sika asked for a bit more emphasis on 'preparation', so waiting for the relevant Sika documents to arrive so that can be included.

 

They also suggested a bit more guidance on 'setting' times, noting that in temperatures close to 10 degrees, it could take as much as 30 days to cure.

So I think any vibration and jolting during that curing period is going to hammer the Solar Panel down onto the Adhesive potentially reducing the bead height, making spacers essential to cover as many eventualities as possible.

 

Spacers are important to also help stop someone over tightening the screws, but obviously people will have their own preferences of installation. Sika liked the 'tube' spacer idea because the void gets filled with Adhesive resulting in almost zero impact on surface area.

But also, being 'tubes' they bend sideways as the Solar Panel expands and contracts as the 'micro' movement is greater along it's length/width than up/down.

 

 

One point that was made, because they have heard and seen a lot more detached panels than us, that they think additional mechanical fixing is not only sensible, but essential, especially as some Panels have detached from breakdown of the paint adhesion to the motorhome roof. So the adhesive did it's job, but the paint didn't do it's bit of sticking to the roof.

 

 

Apparently there have been two other Sika initiatives to document Solar panel fitting : one with Photonic Universe (I think) and the other by a Self Build forum.

I am proud to say that ours got the highest marks from Teacher.

 

I am hoping someone will use the guide to install a Solar Panel and take lots of photos that we can add to the web page to make it even better.

 

http://www.aandncaravanservices.co.uk/solar-panels.php

 

 

Other Solar web pages cover the electrical side of fitting on the web site.

 

 

[Paul-]

As the ABS mountings have a bigger footprint than aluminium they don't have the same problem with paint lifting, its just poor preparation of the feet that are a problem.

Poor preparation of the paint and a small footprint bracket on floating aluminium paneled roof, remembering that the roof is subject to a large amount of wind and vibration is an accident waiting to happen, in my opinion.

 

[Deneb]

Paul- - 2018-11-24 9:04 AM

 

As the ABS mountings have a bigger footprint than aluminium they don't have the same problem with paint lifting, its just poor preparation of the feet that are a problem

 

On one of the Sevel panel vans prone to shedding its top coat of paint it probably wouldn't matter how large the footprint was if the paint to which it was stuck decided to part compony from the undercoat!

[tonyishuk]

Just to add that some motor home roofing is flexible plastic membrane and not actually fixed to the roof / ceiling panel.

 

Obviously it would pay to check what covers your roof before making a choice of how to fix.

 

Rgds

 

 

[Basher Baz]

Hi All

 

I'm new to this forum thing but have read through this and cant see a single reference to anyone using Sika Primer as part of the preparation of the roof prior to applying the adhesive.

 

In my line of work we use Sikaflex adhesive to install metal hose reel drums in fire appliances with plastic bodies. These are subject to huge weights and stresses and have only failed when primer has not been used or the adhesive not had long enough to cure before being put into service.

 

Needless to say when I installed 2 x 100w solar panels on the roof my 2012 VW Crafter 18 months ago, as well as prepping the mounting points with emery paper, Sika Primer 210 was applied followed by the adhesive. No screws pass through the roof. The only screws I used are to fix the feet to the panels.

 

I also installed two additional feet at the front edge to push the majority of the air over the top as they are very close to the leading edge of the roof.

 

I have covered 15,000 miles since then in all temperatures all year round from Spain to Scotland with no issues. As others have already said, the secret is in the preparation.

 

Hope this helps

[Robbo]

Nice job Basher Baz and good point about using the primer.

 

Very wise to install additional mounts along the leading edge to reduce airflow beneath the panel, being so close to the front.

 

I recently heard of a panel taking flight because the leading edge of the panel was positioned close to where the roof curves down to the windscreen AND, as far as I know, the leading edge was unsupported.

[Robbo]

Just found these aluminium aerodynamic supports:

 

Jackson Leisure

Cross sectional dimensions are 10.5cm x 6cm. I guess the 10.5cm refers to the overall width and the 6cm refers to the height (2.5cm air gap + 3.5cm panel height).

They would need to be connected to the panel before being glued down. Removal of the panel at a later date would be virtually impossible.

https://www.jacksonsleisure.com/caravan-and-camping/solar-panels/regulators-and-accessories/alloy-aero-motorhome-boat-solar-panel-profile-mount-2-pack/

 

An alternative solution, using a similar profile, overcomes removal of the panel at a later date by connecting the panel using a couple of screws either end. The profile curves over the top of panel adding additional security. The support can be cut to length to match the width of the panel. The profile wouldn't suit all panels because of the set height dimension, but would fit the most commonly used panel height dimension of 3.5cm.

PS. I do have my reservations concerning the durability of using a plastic mould between support and panel.

https://www.solartechnology.co.uk/new_aero_bracket_for_roof_top_solar_panels?b_id=91

[globebuster]

Basher Baz - 2018-11-24 10:47 PM

 

Hi All

 

I'm new to this forum thing but have read through this and cant see a single reference to anyone using Sika Primer as part of the preparation of the roof prior to applying the adhesive.

 

In my line of work we use Sikaflex adhesive to install metal hose reel drums in fire appliances with plastic bodies. These are subject to huge weights and stresses and have only failed when primer has not been used or the adhesive not had long enough to cure before being put into service.

 

Needless to say when I installed 2 x 100w solar panels on the roof my 2012 VW Crafter 18 months ago, as well as prepping the mounting points with emery paper, Sika Primer 210 was applied followed by the adhesive. No screws pass through the roof. The only screws I used are to fix the feet to the panels.

 

I also installed two additional feet at the front edge to push the majority of the air over the top as they are very close to the leading edge of the roof.

 

I have covered 15,000 miles since then in all temperatures all year round from Spain to Scotland with no issues. As others have already said, the secret is in the preparation.

 

Hope this helps

 

 

 

Spot on Basher - as I mentioned much earlier in the thread - the correct process and primers need to be used. In my line of work it would be unacceptable and dangerous not to follow the correct procedure for Sika and other PU sealants. I've used Sika products for over 30 years, on many different substrates and subject to very harsh conditions - never had a failure.

As I said, some are doing half a job.....

[aandncaravan]

Basher Baz - 2018-11-24 10:47 PM

 

Hi All, I'm new to this forum thing but have read through this and cant see a single reference to anyone using Sika Primer as part of the preparation of the roof prior to applying the adhesive.

 

In my line of work we use Sikaflex adhesive to install metal hose reel drums in fire appliances with plastic bodies. These are subject to huge weights and stresses and have only failed when primer has not been used or the adhesive not had long enough to cure before being put into service.

 

I have covered 15,000 miles (with my Plastic bracket Solar Panels) in all temperatures all year round from Spain to Scotland with no issues.

 

:

 

 

Baz, I don't know where you were looking for comments about preparation, but the post of 23rd of November stated :

"Sika asked for a bit more emphasis on 'preparation', so waiting for the relevant Sika documents to arrive so that can be included".

.

Well they have arrived today and Sikaflex 292i in the application being specified does NOT require ANY Primer.

All it needs is a clean Oil, free surface between the Aluminium we recommend and a Motorhome painted aluminium roof.

 

However it is clear from the documents that Plastics require all sorts of special preparation depending on the material used to make the 'Plastic' and the selected adhesive appropriate.

 

Even then some plastics are totally unsuited to bonding.

Sika state in the document -

 

 

"7. Plastics -

Some plastics require special treatment before they can be successfully bonded (FLAME treatment or Plasma Etching in combination with Chemical pre-treatment). Polypropylene and polyethylene are two examples.

With many plastic blends it is impossible to give specific guidance due to the potential variety of components and internal/external release agents they contain. Thermoplastics are subject to a risk of stress cracking. Thermally formed components must be destressed prior to adhesive bonding by the controlled application of HEAT".

 

 

That sort of preparation is way beyond most DIY AND Professional Installers, and why we suggest everyone plays safe and avoids Plastics.

Even if they have Plastic heat treatment or Plasma etching in combination with chemicals, unless you are 100% sure the Plastic will last 10 years without cracking and breaking up we suggest you use Aluminium which has PROVEN itself to last for many, many years in a motorhome and marine environment.

.

 

All the posters on the Motorhome Fun Forum thought the Solar Panels, that had been attached for some

time, were secure.

 

Sika have now come across a LOT more, hence the tho previous initiatives. All the detachments have involved Plastic brackets without any secondary, safety mechanical fixing.

 

 

So, Baz, just because you have travelled a few miles doesn't mean the panels won't fly off next year.

 

I note that in your line of work you are bonding metal, probably Aluminium or Steel to a 'Plastic' roof, which is more than likely GRP, not a thermoplastic.

For GRP, Sika say that it does provide strong bonding to metal and does not suffer stress cracks.

That is very different to the bonding of thermoplastics to a Painted motorhome roof, so I am not sure your analogy is relevant?

 

 

In any case the new Sika advice is that to reduce the possibility of stress cracking and break up of Plastics, they now recommend a minimum 10mm Sealant bead to allow for thermal expansion. Any holes that are drilled, should be oversize, even for those between the Solar Panel and the Bracket to allow for movement to prevent cracking the Plastic bracket.

 

I would be willing to bet 5p that very few of the Professional fit Solar panels using plastic brackets had even 6mm of a an appropriate Adhesive. Not seen any advice on the Forums to use 10mm either for Plastics.

 

We all know that modern adhesives can create incredibly strong bonds to the appropriate materials But during this work with Sika, it is clear that not all Plastics are appropriate materials for use on a motorhome roof.

.

I will update the guidance on web page with this info from the Sika Technical team today, and the other stuff that arrived on Friday. Hope to have it done by Wednesday..

 

 

I will not argue the points further, I will just keep the web page updated as and when we hear more from Sika - . http://www.aandncaravanservices.co.uk/solar-panels.php

We are following Sika advice and have taken every care to ensure that this joint approach is the safest, belt and braces, and we are willing to stand by that.

 

Those that believe Plastic brackets are suitable will probably continue to advise everyone as such, but hopefully they will also take out Insurance to pay the legal costs of anyone whose Solar panel detaches resulting in Death or serious injury from following their advice?

 

 

[Robbo]

Allan, just read your 24/11/18 updated webpage. Excellent guide, congrats.

 

Just have a couple of comments:

 

1) Totally agree with a full width support for the leading edge to reduce air turbulence getting under the panel. Not so sure about a full width support along the rear edge. I would prefer an escape route for the turbulent air so it can be dissipated without increasing pressure between the roof and underside of panel. Consequently, I would be inclined to install two shortish supports at the rear. Having said that, most of the uplift on the panel will probably be generated along the top surface of the panel, so I understand your reasoning to improve the adhesion of the rear support. Perhaps we need an aerodynamics engineer to provide guidance on this one :-D

 

2) Think you briefly mentioned in your first draft about tethering the panel to an anchor point as an enhanced safety measure. Quite a few vans do have roof bars or cargo rails where a short restraining cable could be attached to the solar panel. Alternatively, an anchor point could be installed through the roof (with a spreader plate), adjacent to where the solar cables enter the van, usually in a cupboard.

[plwsm2000]

Great source of information Allan.

 

It looks as though Sika have changed their recommendation of using 252 since this was published back in 2013

[url=] https://sikaflexit.wordpress.com/2013/09/06/how-to-install-a-solar-panel-to-the-roof-of-your-caravan/ [/url]

 

It might be worth mentioning that these adhesives must be applied at ambient temperatures between 10 to 40 degC. 10 degC may be a bit challenging to maintain at this time of year given that it needs several days to cure (a 6mm bead needs at least 5 days!).

I spoke to Sika about this when I fixed my panel, and I was told that it was important to keep the temperature above 10 until at least the adhesive formed a skin. If you are planning to fit a panel at this time of year, it is worth checking the weather forecast!

 

I used 252i (not 252) which has a slightly higher tensile strength than 292i but is less chemical resistant. 252i is quite different to 252.