Attaching panel to roof

[herald_400rl]

I'm shortly commencing my electrical upgrade (look out for a motorhome fire in the news ) and my new problem is how to attach the panel.

The roof is covered in a plastic like sheet, maybe fibreglass? And it's not properly bonded so I'll need to use mechanical fixings, problem is i can't find any studs... I can walk across the roof without any issues (staying away from the roof vents). So would i be in danger to assume some thickness of ply underneath?

Picture for context.

 

[Jimbohorlicks]

Oh! look at all that empty space
What van have you got?

 

[herald_400rl]

Oh! look at all that empty space
What van have you got?

It's getting a 535w panel which will consume from the metal bar to the first skylight. Could squeeze a 120w up the side but think that'll be overkill.

It's a herald 400rl

 

[Gellyneck]

It looks like you've got what's known as a floating roof.
Our AT has same and there's a solar and satellite dish attached by adhesive only

 

[tonka]

The roof on my previous Autotrail had what I would call "floating". I only bonded Ali angle to that with Puraflex And never had any issues.
Be aware there are often cables running in the roof between the outer ply and the ceiling so be cautious if you plan to use any screws .

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[herald_400rl]

It looks like you've got what's known as a floating roof.
Our AT has same and there's a solar and satellite dish attached by adhesive only

Does it not move/flex? I'd be terrified of it coming off, it'd write the motorhome off if it tore the roof off and could easily kill someone.
I've been thinking about drilling through into some taped 4mm plate and under the headlining and then making good.

 

[Gellyneck]

Does it not move/flex? I'd be terrified of it coming off, it'd write the motorhome off if it tore the roof off and could easily kill someone.
I've been thinking about drilling through into some taped 4mm plate and under the headlining and then making good.

The solar panel was factory fitted in 2013 and satellite in 2019 and both still there however understand your concerns.
The panel is fitted to angle brackets front and rear and the satellite is on a plate around 600mm x 400mm.
When I was fitting the satellite I looked for the area of the roof with "less bounce".

 

[Jev88]

My old Autocruise had the floating roof but was Puraflex40 (proper prep and gapping) with a plastic foot.at each corner and long ones down sides - 6 years and counting.

 

[herald_400rl]

Thinking of getting 2 x 2m strips of 75 x 50mm unequal angle and adhering the 75mm side to the roof so 150mm of coverage along the 2m panel length. Stick down with sika 554.
The only downside is this won't allow air underneath from the length of the panel.
If prefer mechanical fixings, too, but I'll never find a batton.

 

[Gellyneck]

Thinking of getting 2 x 2m strips of 75 x 50mm unequal angle and adhering the 75mm side to the roof so 150mm of coverage along the 2m panel length. Stick down with sika 554.
The only downside is this won't allow air underneath from the length of the panel.
If prefer mechanical fixings, too, but I'll never find a batton.

Not clear on whether you're fitting panel across or lengthwise on the roof but would suggest your angle is fitted to front and rear so the airflow when moving doesn't get under it.

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[fishplug]

Does it not move/flex? I'd be terrified of it coming off

On the old sprinter I made a 'roof rack' out of 2 x 5m lengths of Unistrut which were fastened into some rivnuts for mechanical fixing but I ran a bead of Sikaflex 515 on the underside just to prevent any metal on metal vibration wearing through the paint....

The engine went and I started stripping the van to sell and figured the Unistrut would be handy. The bolts all came out easily and then I started trying to remove the Unistrut.

To get it 'started' required my biggest crowbar and enough force to leave a permanent dent in the roof where I'd been standing and it must have taken me 10 -15 minutes each side and all my leverage and force to get them off.

Bearing in mind that I'd not been over generous with the sikaflex as I hadn't set out to use it as an adhesive.

If I was in your position I'd quite happily use some 45mm aluminium angle to fasten the panel using some sikaflex or other similar ADHESIVE silicone (not your kitchen and bathroom stuff which is just a sealant)

Do all the prep and clean and degrease everything but if the wind is strong enough to rip the panel off your roof then it's probably already going to have put your van on it's side and ripped the roof off.

The strength of it is incredible.

 

[fishplug]

Not clear on whether you're fitting panel across or lengthwise on the roof but would suggest your angle is fitted to front and rear so the airflow when moving doesn't get under it.

A bit of airflow under it will help keep the panels cool on a hot day and therefore more efficient.

Maybe a compromise with your proposed 'barrier' but with a few holes in it to let some of the air pass?

 

[herald_400rl]

Not clear on whether you're fitting panel across or lengthwise on the roof but would suggest your angle is fitted to front and rear so the airflow when moving doesn't get under it.

Panel is 2.1m x 1.1m so will be long length across width.

On the old sprinter I made a 'roof rack' out of 2 x 5m lengths of Unistrut which were fastened into some rivnuts for mechanical fixing but I ran a bead of Sikaflex 515 on the underside just to prevent any metal on metal vibration wearing through the paint....

The engine went and I started stripping the van to sell and figured the Unistrut would be handy. The bolts all came out easily and then I started trying to remove the Unistrut.

To get it 'started' required my biggest crowbar and enough force to leave a permanent dent in the roof where I'd been standing and it must have taken me 10 -15 minutes each side and all my leverage and force to get them off.

Bearing in mind that I'd not been over generous with the sikaflex as I hadn't set out to use it as an adhesive.

If I was in your position I'd quite happily use some 45mm aluminium angle to fasten the panel using some sikaflex or other similar ADHESIVE silicone (not your kitchen and bathroom stuff which is just a sealant)

Do all the prep and clean and degrease everything but if the wind is strong enough to rip the panel off your roof then it's probably already going to have put your van on it's side and ripped the roof off.

The strength of it is incredible.

That's reassuring, I'm concerned that what I'll be fixing to is floating, what if it pulls the top layer off which isn't bonded?

 

[1967bowesj]

Panel is 2.1m x 1.1m so will be long length across width.


That's reassuring, I'm concerned that what I'll be fixing to is floating, what if it pulls the top layer off which isn't bonded?

If you fix the angle transverse at 2.1m then that will stiffen the roof, not much flex left. Keep it as far forward as possible so near the roof vents as they must have supports near them

 

[fishplug]

Panel is 2.1m x 1.1m so will be long length across width.


That's reassuring, I'm concerned that what I'll be fixing to is floating, what if it pulls the top layer off which isn't bonded?

If that's a concern then maybe find a discreet area which you can sand down to whatever the substrate is.

Sounds like it's likely to be GRP but if you can bond directly to that rather than the paint sitting on top of it then I guess that's probably better.

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