Backing material for rigid solar panel.

[Tigerr]

Hoping for some materials advise. I want to install a rigid panel on the roof of my pilothouse, on a small fibreglass motor fishing boat. (Yes it's not canals, it's the sea, but I cant find the equivalent of canal world for small sea craft - its a much more fragmented world). i want to keep my batteries sweet, as I do leave the boat and theres no power on the mooring, but lots of sun. Ive bought the panel which is 60X90 cm, and the kit, should do nicely. But its a double skinned fibreglass roof, and I can see no way to drill and blind fix the brackets.  Ive thought about blind rivet bolts but the material itself is I think too thick, and I dont want to make a catastrophic mistake finding out.  

There's a raised flat area in the middle which is I think intended for mountings. (Radar/ariels etc). The local boatyard said theyd recommend sikofexing the back of the panel onto that - which I think is a good idea. Except I think the panel needs reinforcing first. What I have in mind is some sort of weather and heatproof stiff board, not wood. I I am struggling to identify the material - some sort of foamed rigid plastic. 

Someone here will know exactly what I need I think. 

[IanD]

11 minutes ago, Tigerr said:

Hoping for some materials advise. I want to install a rigid panel on the roof of my pilothouse, on a small fibreglass motor fishing boat. (Yes it's not canals, it's the sea, but I cant find the equivalent of canal world for small sea craft - its a much more fragmented world). i want to keep my batteries sweet, as I do leave the boat and theres no power on the mooring, but lots of sun. Ive bought the panel which is 60X90 cm, and the kit, should do nicely. But its a double skinned fibreglass roof, and I can see no way to drill and blind fix the brackets.  Ive thought about blind rivet bolts but the material itself is I think too thick, and I dont want to make a catastrophic mistake finding out.  

There's a raised flat area in the middle which is I think intended for mountings. (Radar/ariels etc). The local boatyard said theyd recommend sikofexing the back of the panel onto that - which I think is a good idea. Except I think the panel needs reinforcing first. What I have in mind is some sort of weather and heatproof stiff board, not wood. I I am struggling to identify the material - some sort of foamed rigid plastic. 

Someone here will know exactly what I need I think. 

https://www.simplyplastics.com/catalog/sheet/pvc-foam-board-(foamex)/black-pvc-foam-board-/c-24/c-88/p-660

£71.63 each for 900mm x 600mm x 19mm though... 😞 

Edited July 30 by IanD

[Jen-in-Wellies]

17 minutes ago, Tigerr said:

But its a double skinned fibreglass roof, and I can see no way to drill and blind fix the brackets.

How about fibreglassing on the brackets, where they need to go to mount the panel frame? The panel is meant to be supported by it's frame, so doing that is the least likely to lead to problems, or breakage under wind load etc.

[David Mack]

My solar panel is mounted on brackets like these (except mine came in a set of 6 with straight brackets for the middle of the long side). I didn't want to drill the roof so I simply glued the brackets down with Stixall to the painted steel roof. They've been fine for 5 or 6 years now.

 

https://www.12voltplanet.co.uk/set-4-black-plastic-corner-mounting-brackets-rigid-framed-solar-panels.html

(Also available in white).

[Tigerr]

Unfortunately the raised section makes those brackets unworkable. Id have done that otherwise!

Is 'Foamex' the material I need? 

[Tony Brooks]

When I first read the topic I thought rubber Rawl Nuts would deal with the double skin and provide a mechanical fixing that would only leave four holes to fill if the panel ever had to be removed, but the talk of sheet material made me think they were stick down flexible panels. They come in different lengths and sizes up to 8mm.

 

 

 

 

[IanD]

3 hours ago, Tigerr said:

Unfortunately the raised section makes those brackets unworkable. Id have done that otherwise!

Is 'Foamex' the material I need? 

Probably (see link I posted) but it's not cheap for the size/thickness you need... 😞 

What stops you just cutting a piece of marine ply the size of the panel, painting it (epoxy?), fixing it to the panel frame using the provided screw holes, and then gluing this down to the raised section of roof?

 

(or glue the board down first, then screw the panel to it)

Edited July 31 by IanD

[David Mack]

3 hours ago, Tigerr said:

Unfortunately the raised section makes those brackets unworkable. Id have done that otherwise!

How big is the raised section in relation to the panel size? If you fix the panel to a board and glue that to the raised section are the edges going to overhang? And what if the wind gets under them?

[Anonathy]

If you're just trying to reinforce the panel personally I'd just stick a couple of pieces of wood to the roof on both edges and then attach the edges of the panel to these. Then the panel is attached in the centre and on the edges, the wood will stop the wind getting underneath them, and it's just the price of a piece of wood and your sticky stuff of choice.  

[BoatingLifeUpNorth2]

Why do you think the rigid Panal will need reinforcing, you won’t be walking on it? Do you think the roof will flex in some way?

 People don’t reinforce them on camper vans, is the roof curved or flat with the raised flat bed you mention?

 You could be over thinking a problem which is not there.

[IanD]

1 hour ago, BoatingLifeUpNorth2 said:

Why do you think the rigid Panal will need reinforcing, you won’t be walking on it? Do you think the roof will flex in some way?

 People don’t reinforce them on camper vans, is the roof curved or flat with the raised flat bed you mention?

 You could be over thinking a problem which is not there.

Panels are attached at the edges using the frame, but it looks like the "raised roof" area (used for attachment) is smaller than the frame -- so he needs a way of linking the frame edges to the central raised area, and the original idea was to use a foamed plastic panel.

 

But anything that attaches to the frame and the raised area would do, even a couple of crossbars.

Edited July 31 by IanD

[GUMPY]

How high is the raised bit?

These type of brackets give a couple of cm clearance.

I have them on the van just sikaflexed to the roof.

 

https://amzn.eu/d/0ac0MRry

 

[BoatingLifeUpNorth2]

2 hours ago, IanD said:

Panels are attached at the edges using the frame, but it looks like the "raised roof" area (used for attachment) is smaller than the frame -- so he needs a way of linking the frame edges to the central raised area, and the original idea was to use a foamed plastic panel.

 

But anything that attaches to the frame and the raised ares would do, even a couple of crossbars.

It sounds like the raised panel is in the middle and it needs to be cleared. If he had risers on each corner, he might be able to raise it high enough to clear the raised panel on the roof. It will obviously depend on the height of the fixed panel. Which we don’t know??
 Maybe the van roof supports that @GUMPY linked to would clear it, if not, he could put additional risers on the corners to add more height if needed. It all depends on how much lift it needs to clear the roofs raised panel.
 I would say risers would be a better option than to Sikaflex foam to the raised roof panel then Sikaflex the panel to that as he mentioned. 

Edited July 31 by BoatingLifeUpNorth2

[Tigerr]

Thanks for the responses.

The panel is flat, the roof is curved, with a central flat section which is the area that would be used as the glue base.  I need to get a bit more height in in though, as the panel edges are deeper than the 

The unglued area of the panel is big enough to get a bit of flex going in a high wind or vibration as with going along at 20knots under power in the sea, which I think might lead to the panel cracking in time, as the edges would be unfixed. Effectively the panel has to be made strong enough to hold itself steady in such conditions. This a weatherproof backing board is needed. 

No overthinking, all I wanted is the name of the plastic board stuff. I think I got the answer - its foamex. Of course its expensive, this is 'marine'. 

[IanD]

12 minutes ago, Tigerr said:

Thanks for the responses.

The panel is flat, the roof is curved, with a central flat section which is the area that would be used as the glue base.  I need to get a bit more height in in though, as the panel edges are deeper than the 

The unglued area of the panel is big enough to get a bit of flex going in a high wind or vibration as with going along at 20knots under power in the sea, which I think might lead to the panel cracking in time, as the edges would be unfixed. Effectively the panel has to be made strong enough to hold itself steady in such conditions. This a weatherproof backing board is needed. 

No overthinking, all I wanted is the name of the plastic board stuff. I think I got the answer - its foamex. Of course its expensive, this is 'marine'. 

I don't think the foamex is expensive because it's marine, that's just an industrial plastic supplier.

 

Or do you mean it's no surprise that it's expensive because *anything* to do with boats is always expensive? 😉 

[Tigerr]

4 minutes ago, IanD said:

I don't think the foamex is expensive because it's marine, that's just an industrial plastic supplier.

 

Or do you mean it's no surprise that it's expensive because *anything* to do with boats is always expensive? 😉 

Everything I have ever done to do with boats, over 40 years, has cost several times more than I expected.

Even my tiny little fishing boat required a new outboard engine that basically doubled its cost. My simple plan to put a solar panel on is simply another money pit, but I hope that it will keep the new batteries for the new motor etc sweet. 

However, I did get out today for a few hours into the sea, magnificent blue water, and caught a few small fish. It's quite fun sitting there at anchor watching the sailors and yachts, being captain of my own little ship. 

[Llamedos]

7 hours ago, Tigerr said:

Unfortunately the raised section makes those brackets unworkable. Id have done that otherwise!

Is 'Foamex' the material I need? 

I used to use Foamex board a lot, mainly for creating display boards at exhibitions etc. It was great for that because it's easy to cut and very lightweight but rigid and strong it isn't. I used a bit on my boat to make a switch panel a couple of years back but using it to mount a solar panel? I'm really not sure. 🤔 Apart from its lack of strength and flexibility I can see it warping in the hot sun.

[IanD]

Just now, Llamedos said:

I used to use Foamex board a lot, mainly for creating display boards at exhibitions etc. It was great for that because it's easy to cut and very lightweight but rigid and strong it isn't. I used a bit on my boat to make a switch panel a couple of years back but using it to mount a solar panel? I'm really not sure. 🤔 Apart from its lack of strength and flexibility I can see it warping in the hot sun.

I'm sure that's true for the thin stuff (how thick were you using?), which is why I suggested the (expensive) 19mm which is much stiffer -- ~3x better than 10mm, ~12x better than 5mm...

[GUMPY]

Apart from being heavy what's wrong with using HDPE sheet? Can be easily cut and "welded" just make a support for the edges that follows the contour of the roof.

[Llamedos]

Just now, IanD said:

I'm sure that's true for the thin stuff (how thick were you using?), which is why I suggested the (expensive) 19mm which is much stiffer -- ~3x better than 10mm, ~12x better than 5mm...

Fair point you may be right.

 

I'm just relating my experience of using it and it was the thinner stuff. If you've had some success with the thicker stuff on other projects it might work. 🤔

 

However, I've just asked Google AI and got this which is taken directly from information published by one of the main UK suppliers... "Thick Foamex board (expanded PVC) is not suitable for long-term outdoor marine solar mounting because it lacks structural rigidity under wind loads, degrades under high heat, and traps damaging thermal energy."

 

I think the OP needs to go carefully unless there's some real life examples of it being used successfully for this. Maybe ask the panel manufacturer.

[IanD]

13 minutes ago, GUMPY said:

Apart from being heavy what's wrong with using HDPE sheet? Can be easily cut and "welded" just make a support for the edges that follows the contour of the roof.

That's easier than it sounds with a curved roof -- actually, a complete PITA according to Ricky, who had to do exactly that for rigid solar panel mounts... 😉 

 

[Tigerr]

Foamex is a bust - long term exposure to heat - which is a certainty under a solar panel - will blow it because its full of air bubbles. 

I think I will retreat and think it all through again. Might look at wood, and grp backing. Its out of sight and basically just needs to be weather/rotproof and structurally rigid. I can see a solution. 

Thanks all, I am going to back out of the thread, very useful comments as always but obviously its a bit niche. 

[IanD]

Just now, Tigerr said:

Foamex is a bust - long term exposure to heat - which is a certainty under a solar panel - will blow it because its full of air bubbles. 

I think I will retreat and think it all through again. Might look at wood, and grp backing. Its out of sight and basically just needs to be weather/rotproof and structurally rigid. I can see a solution. 

Thanks all, I am going to back out of the thread, very useful comments as always but obviously its a bit niche. 

I did suggest good old painted marine ply... 😉 

[GUMPY]

41 minutes ago, IanD said:

That's easier than it sounds with a curved roof -- actually, a complete PITA according to Ricky, who had to do exactly that for rigid solar panel mounts... 😉 

 

That's exactly what I meant.

HDPE is easier to do it with than marine ply that's for certain.

We used to use it for building portable power distro, easy peasy. 

[Tigerr]

Thanks to the Canalworld folk. Ive gone back to the boat and re-examined the issue. I think I can make a fix using the plastic corner mounts, using sikafex buildup to fudge the curvatures, and more sikafex inside the mount to fair up to the panel aluminium frame. Basically a lot of mastic, but I think it might work. Plus with four mounting points, I think it will be sufficiently string to cope with open sea conditions for a few years. Asthetically, got to get a neat finish to the sikafex or it could look quite nasty. 

But - I can see a solution to the battery decay problem here!