Solar panel sticky stuff. A test.

[fat haggis]

I stick wet wall 2400 x 1200 sheets to bathroom walls, some of these walls are not straight. I use those expanding bars (bit like light weight acrows) to push the 12mm marine ply wet wall to the wall. I use the dot and dab method on the panels.

Not had one come off yet, and only use Sticks Like https://www.screwfix.com/p/evo-stik-sticks-like-sh-t-adhesive-290ml/22070

I have fixed 3 solar panels on 2 Hymer roofs using this and those large plastic corners, Amazon product ASIN B009X7WKR2they are still stuck down. Sometimes you can overthink things.

Thanks for that info mate I'll be fitting a solar setup soon andxim using plastic set like yours with the extra middle sections. And for extra piece of mind I'm using silkflex 512

 

[Jimbohorlicks]

My last van had a satellite dome, which I planned to remove when I traded it in. I had the van for 2 years, the dome was already on the van when I bought it.
The dome sat on four feet that were stuck to the roof, I don't know what with, but the feet, pads, were as big as small side plates. I hadn't had any worries re it coming off whilst driving, in fact the thought never occurred. When I took off the dome, it cracked, but that's another tale. The base was fastened to the roof pads with a couple of machine bolts to nuts inset into the pads.the bolts did not go into the roof. I removed all the bolts and when I lifted the base, two pads came with it, they were not stuck to the roof. I had a scraper blade ready to remove the pads, but had also considered leaving them on so as to not damage the roof.as I touched the third pad it came up in my hand, the fourth pad I had to tug a little but it came away quite easily. They had been stuck down with something but over the years it had obviously deteriorated and the dome was only being held on by sheer luck..
I now check everything that is "stuck" to my roof every time I wash it or have the ladders out .

 

[Gellyneck]

I could do a static test with 'Management'.

The difficult part will be to get her to stand on the rickety stool while I tie the rope around her'''''''''
(There's No way that the QC for the prosecution could find this post, or is there? )

I think you're correct in that I don't think a prosecution QC will see your post. However, knowing your luck the adhesive will fail and you'll be left with Management standing there with a rope tied to her ********* and a metal bracket on the ground! This is DEFINITELY NOT a comment on Management physique just poor adhesion!
How fast can you run in comparison with Management is the next obvious question!

 

[Emmit]

As is usual, I ran after her, caught her up.

That's when she got me.?

 

[Mr Chrysalis]

No ......... we simply need to stop over-thinking it. Just stick clean surfaces together using PU adhesive. It works. My experience is of installing panels on 4 vans. Twice used Sikaflex and twice used Tigerseal. Adhesion checked visually and with a light tug once a year when cleaning the roof. No issues, no separation, no panels lost. Has anyone on the Forum ever had a panel come loose because of adhesive failure?

Wind passing over / under the panel will tend to pull it onto the roof (air will speed up under the panel because of the small gap). Wind hitting the front edge will attempt to push the panel towards the rear of the van.

I recognise this is academic but I don’t think that the air passing under the panel will increase in speed as the gap is too small. That works with a wing because of it’s shape. The upper side is curved so it travels further than the flatter underside and is therefore faster. The higher speed of the wind creates a lower pressure above it, giving the lift. With the solar panel both top and bottom are flattish so same distance to travel. True, the gap is a bit narrower but with a square inlet and outlet flow will be poor, and there is very little space below the boundary layer to be enough to create the low pressure which would cause the inverted lift (downforce). It might make a really good project for an engineering undergrad to design curved upper and lower surfaces and an aerodynamic air entry guide so that it did create downforce.
Personally I don’t trust any sort of glue, too many bad experiences of things not staying stuck, feel much safer with mechanical fixings. I recognise this is prejudice and is my problem!

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[Emmit]

In my case (or to be more correct,in the case of the solar panel on our 'van) there isn't an even gap along the leading and trailing edge of the solar panels.

Because the roof of the Hobby is 'barrelled' I made the decision early on to try, as best as possible, to make the top of the panel as near horizontal as possible. There is a difference therefore in the height of the panel from the roof on the left side and right side when viewed from the front or rear. I wouldn't know whether this has any bearing on any potential pressure forces imposed on the panel(s) as they travel through the air.

 

[AXO66]

Add on the turbulance of the air barrelling down the roof after the front of the van cuts through. Bound to be various areas of different pressures moving randomly along the whole roof.!

 

[Mr Chrysalis]

In my case (or to be more correct,in the case of the solar panel on our 'van) there isn't an even gap along the leading and trailing edge of the solar panels.

Because the roof of the Hobby is 'barrelled' I made the decision early on to try, as best as possible, to make the top of the panel as near horizontal as possible. There is a difference therefore in the height of the panel from the roof on the left side and right side when viewed from the front or rear. I wouldn't know whether this has any bearing on any potential pressure forces imposed on the panel(s) as they travel through the air.

It will probable make you beer violently from side to side ( but only when combined with large volumes of alcohol)

 

[Gromett]

I do know however, that the the top of the panels are flat and not curved. I also know that the distance between the two edges of the panels both top and bottom are the same. As a result there will be no difference in pressure above or below them and theoretically no 'lift' as one would get with, say, an aeroplane wing.

I wasn't going to comment on this thread until I re-read this.

Lift does not require a curved surface nor does it require a tilt. All it requires is that the air speed on top of the panel be higher than that underneath it.

 

[tonyidle]

I wasn't going to comment on this thread until I re-read this.

Lift does not require a curved surface nor does it require a tilt. All it requires is that the air speed on top of the panel be higher than that underneath it.

You can demonstrate that effect by blowing through the gap between two pieces of paper held in your hands. Your head says they'll move further apart - physics creates the opposite effect.

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[Emmit]

I wasn't going to comment on this thread until I re-read this.

Lift does not require a curved surface nor does it require a tilt. All it requires is that the air speed on top of the panel be higher than that underneath it.

Could I point out that in the experiment you have shown, the air below the table is not moving at all.

 

[Jimbohorlicks]

Could I point out that in the experiment you have shown, the air below the table is not moving at all.

Think that's, the whole point, similarly the air under the panel is not moving so likewise the panel will tend to rise as the paper. 6"nails come to mind, or you could wrap a rope around the van with a nice bow on top to secure the panel.

 

[Emmit]

You can demonstrate that effect by blowing through the gap between two pieces of paper held in your hands. Your head says they'll move further apart - physics creates the opposite effect.

Think that's, the whole point, similarly the air under the panel is not moving so likewise the panel will tend to rise as the paper. 6"nails come to mind, or you could wrap a rope around the van with a nice bow on top to secure the panel.

I wonder if I could put a nice 'comfy' seat up there for 'Management.

 

[Gellyneck]

Emmit
I hope you're taking in all this scientific advice.
If you can realign your panels to take advantage of the lift you'll get just think of the reduction in tyre wear!

 

[Oldbob]

Another fun way to test adhesives is to get a pair of old work boots, two different types at adhesive and glue them to the roof of car/ van and go for a drive, if people follow at a distance, toot, wave, then you know that they are still there and glue works.
If people sit up your a** as usual then glue has failed !
This can be carried on until boots either fall off due to glue failure, or boots rot away !

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[Jimbohorlicks]

I wonder if I could put a nice 'comfy' seat up there for 'Management.

You could do, but what would you "stick" it down with…?

 

[tonyidle]

Think that's, the whole point, similarly the air under the panel is not moving so likewise the panel will tend to rise as the paper. 6"nails come to mind, or you could wrap a rope around the van with a nice bow on top to secure the panel.

As it is being forced through a narrow gap air below the panel will be travelling more quickly than that above the panel. In the experiment hold the paper just above the table. It will be drawn downwards.

 

[Jimbohorlicks]

As it is being forced through a narrow gap air below the panel will be travelling more quickly than that above the panel. In the experiment hold the paper just above the table. It will be drawn downwards.

I doubt that as there are 2 corner brackets that prevent air entering plus other obstructions on the van roof will reduce the airflow below the panels. But there again I am no expert, just observing the configuration.

 

[tonyidle]

I doubt that as there are 2 corner brackets that prevent air entering plus other obstructions on the van roof will reduce the airflow below the panels. But there again I am no expert, just observing the configuration.

I think you've hit the nail on the head. This discussion is interesting but in no way accurately describes what's happening on a surface covered in very non-aerodynamic objects. I'll just carry on with the adhesive.

 

[Jimbohorlicks]

I'll just carry on with the adhesive.

Mine are also "glued" on, one by the motorhomers manufacturer and an additional one myself, I used front and back full width plastic brackets and to date all is sound. I do check them after an experience of taking off a sat dome, that basically was held in place by stiction
and a prayer. If there were issues with panels blowing off MH roofs, I'm sure the insurance industry would be on to it very quickly.

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[Gromett]

Could I point out that in the experiment you have shown, the air below the table is not moving at all.

Can I point out that the air under your panel may not be moving either depending on how you have blocked the front. The point of the video is there is a difference in air pressure caused by the speed of the air passing over the sheet of paper.
The difference is the point. If air moves at the same speed on the top of the panel and the bottom then there will be no lift. BUT this cannot possibly happen on a motorhome mounted solar panel.

Sorry but this is basic physics. Unless a solar panel is sealed all the way round completely then it will develop some degree of lift.

 

[Gromett]

As it is being forced through a narrow gap air below the panel will be travelling more quickly than that above the panel. In the experiment hold the paper just above the table. It will be drawn downwards.

Not correct. The air going under the panel will be moving slower due to the restriction. Remember the air flowing along the vans roof will be slowed by friction the closer to the roof the slower.

 

[Jimbohorlicks]

Just think if the glue holds enough and you have plenty of panels on you could eventually take off. 🛩

 

[Emmit]

Just think if the glue holds enough and you have plenty of panels on you could eventually take off. 🛩

That's one way of getting to Portugal (all this talk of an air bridge)

 

[fat haggis]

I think I'll change my silka 512 for that wallpaper paste they used years ago to stick a man they tried everything to get boots to come off. They where welded on with the paste

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[AXO66]

Not correct. The air going under the panel will be moving slower due to the restriction. Remember the air flowing along the vans roof will be slowed by friction the closer to the roof the slower.

It's so complicated
due to the restrictions of the panel mounts, there is less air under the panel causeIg a very very slight suction down!
then add on turbulance.

so the basic physics is right but the effect on a moving motorhome is chaotic.

i go with the “if there is a problem with sticking it down” , then the industry and insurance folks would have sorted it out.

not to say that there will be duff installations.

 

[Emmit]

Can I point out that the air under your panel may not be moving either depending on how you have blocked the front. The point of the video is there is a difference in air pressure caused by the speed of the air passing over the sheet of paper.
The difference is the point. If air moves at the same speed on the top of the panel and the bottom then there will be no lift. BUT this cannot possibly happen on a motorhome mounted solar panel.

Sorry but this is basic physics. Unless a solar panel is sealed all the way round completely then it will develop some degree of lift.

You are right of course.

In the case of our solar panels, I think I have already found that I couldn't get 12kgs of force to tear off the adhesive which measured approx. 30sq cms. Each of our panels are stuck down on over 250 sq cms of surface area. When one considers that gravity already has a an impact on the panels, I think I'm going to sleep safely.

 

[Gromett]

You are right of course.

In the case of our solar panels, I think I have already found that I couldn't get 12kgs of force to tear off the adhesive which measured approx. 30sq cms. Each of our panels are stuck down on over 250 sq cms of surface area. When one considers that gravity already has a an impact on the panels, I think I'm going to sleep safely.

I wasn't saying you were doing it wrong. I was just pointing out your physics/theories about curves/tilts was wrong. There will be lift on your panel. If you are confident in it now, and are confident that after it has been in the sun/cold/wet/dry for a number of years the adhesive will hold up then good on you

I don't know the construction of your roof, so wouldn't comment on the suitability of your method...

 

[Al n Val]

i’m using these mounts along the panel width with extra bits in the centre as it’s a long panel

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rather than the corner ones, and the panel is going to be fitted in the direction we’re travelling

using Sikaflex 512 so hopefully all will be fine, it’s important to prepare the surfaces first as well which i’m sure you all know

This will be the 2nd panel on the roof and the first has been on nearly 2 years so hopefully all’s good, this one is hopefully being delivered today before 6pm

Al

 

[Emmit]

As the bloke in the Castlemaine advert said (when the Ute, collapsed under the weight of the Beer)
"Overdone it with the sweet sherry."

I can report that I more then doubled the weight on the previously mentioned 'Test'.

The Puraflex survived a good three hours before tearing. Prior to that I had to amend the 'hook' as the weight was pulling that down without affecting the bond between the two aluminium surfaces.

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