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I'm shortly to fix some solar panels to our cabin roof.

 

 

 

I'm not going to bother with a tilting panel system, but fix them firmly and in such a manner that it will be difficult for 'the light-fingered brigade' to help themselves to them when they wish

 

Before I drill holes into my precious roof, and terminally change its integrity, I'd appreciate observations on the best way of maintaining a waterproof seal (I know - other than 'don't drill holes! <_<)

 

I intend to fix a number of stainless steel brackets, using M8 security bolts (with passive coating), (as I cannot easily reach the underside of the holes, I shall tap the M8 thread).

 

 

Assembly: I'm proposing to employ a thin neoprene gasket between the brackets and the roof, finely coated with silicone each side, together with a small blob of silicone on the shoulders of the bolts prior to screwing in.

 

(I expect that the first time I unscrew these bolts will be when we repaint the roof!)

 

 

In your opinions - am I proposing to employ the best method of 'weatherproofing' the fixings?

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I'm shortly to fix some solar panels to our cabin roof.

...

Before I drill holes into my precious roof, and terminally change its integrity, I'd appreciate observations on the best way of maintaining a waterproof seal (I know - other than 'don't drill holes! <_<)

I intend to fix a number of stainless steel brackets, using M8 security bolts (with passive coating), (as I cannot easily reach the underside of the holes, I shall tap the M8 thread).

When I replaced the vents, ended up using bolts with nuts (acessible from inside the vents with a bent spanner) as I found the tapped holes were susceptible to rot (rust/corrosion or whatever) so didn't last long.

One solution may be to use those captive nuts inserted like a pop rivet, the more you tighten them the harder they grip!

Neoprene gasket will propably work better than gunge, especially if you use a hole punch!

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When mine was drilled (cratch fitting) the sealant was put into the threads in the boat.

 

Other than that I think you have it covered.

 

Appears to be OK three years later.

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I'm shortly to fix some solar panels to our cabin roof.

 

 

 

I'm not going to bother with a tilting panel system, but fix them firmly and in such a manner that it will be difficult for 'the light-fingered brigade' to help themselves to them when they wish

 

Before I drill holes into my precious roof, and terminally change its integrity, I'd appreciate observations on the best way of maintaining a waterproof seal (I know - other than 'don't drill holes! <_<)

 

I intend to fix a number of stainless steel brackets, using M8 security bolts (with passive coating), (as I cannot easily reach the underside of the holes, I shall tap the M8 thread).

 

 

Assembly: I'm proposing to employ a thin neoprene gasket between the brackets and the roof, finely coated with silicone each side, together with a small blob of silicone on the shoulders of the bolts prior to screwing in.

 

(I expect that the first time I unscrew these bolts will be when we repaint the roof!)

 

 

In your opinions - am I proposing to employ the best method of 'weatherproofing' the fixings?

 

 

No.

 

The silicone is the wrong material- it is a very poor sealant in thin layers and will leak sooner or later. A better solution would be to keep the neoprene gasket under the brackets and put a bonded seal (dowty washer) under the washer beneath the bolt head. Alternatively some non-setting butyl rubber (like Seamseal CV) would do both as a gasket and as a bolt sealant.

 

Tapping the bolts into the roof is a good concept- but will only work if the roof is more than usually thick. M8 has a thread pitch of 1.25mm ( M8 fine is 1mm) so into even a 5mm roof ( most are 4 mm or thinner) you will not get more than 4 full threads. A standard nut is 6.5 mm thick and designed to be weaker than the bolt thread, so I reckon you need at least a total threaded thickness of 8mm. I think you risk stripping your M8 threads out just tightening the panels up properly and certainly they are not going to stand much wind loading unless there are an awful lot of them. The best thing to do would be to put proper nuts and washers, and some butyl sealant if you like, on the inside. If you cannot get to the inside have some doubling patches at least 6 mm thick welded to the roof and then tap into these.

 

If the holes in the brackets are small enough, or you can get some top-hat washers to reduce the hole, then M6 is 1mm pitch and the nuts are 5mm thick so you may get away with that size tapped directly, but it's still risky on a 4mm roof.

 

If the brackets are stainless then A2 or (best) A4 stainless bolts would be the proper fastener, rather than BZP passivated.

 

 

Regards

 

N

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Ah! - - Thank you so much everyone.

 

All your comments have been invaluable, and particularly BEngo's - who has described (most lucidly) the tapping issues I will create - - I hadn't considered welding doubling plates - I now need to investigate whether this can be done without damaging the sprayfoam insulation below - - or if there is any type of adhesive I could use (though I suspect not.)

 

Captive Nuts/Bolts is another suggestion I hadn't considered - - though ideally I had wished to use security head bolts

 

And magnets - - hmm - - I'm jokingly known as 'magnetman' (I use them for so many things) - but I simply hadn't considered that they may be practical in preventing the theft of my panels . . . I'll have another think about these too.

 

 

Hmm . . back to the drawing board I suspect . . .

 

Sincere thanks

 

Dave

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not withstanding Bengo's comprehensive answer,

 

I was going to suggest stainless steel fixings but hadn't considered the tapping issue, as I've only used M5 to hold down my mushroom vents and plank holders.

 

maybe a couple of 6mm bolts would do instead of 8mm ?

 

jon

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These Neodymium magnets do seem incredibly strong. Maybe it might be worth investigating using them for mounting the panels and then adding a couple of security chains of some description?

 

That way you would be having to drill far less holes in the roof and only for the security chain mountings. Just a thought.

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When I remove our magnetic based sat dish I have to use a strong levering action to break the grip, no chance if I used a direct pull which would be required if there were several magnets. Maybe fix dummy security or coach bolt heads to fool dickheads!

 

If panels are bolted using metal bolts inner ends will have to well insulated to prevent condensation dripping down, perhaps plastic bolts would be better?

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Ah! - - Thank you so much everyone.

 

All your comments have been invaluable, and particularly BEngo's - who has described (most lucidly) the tapping issues I will create - - I hadn't considered welding doubling plates - I now need to investigate whether this can be done without damaging the sprayfoam insulation below - - or if there is any type of adhesive I could use (though I suspect not.)

 

Captive Nuts/Bolts is another suggestion I hadn't considered - - though ideally I had wished to use security head bolts

 

And magnets - - hmm - - I'm jokingly known as 'magnetman' (I use them for so many things) - but I simply hadn't considered that they may be practical in preventing the theft of my panels . . . I'll have another think about these too.

 

 

Hmm . . back to the drawing board I suspect . . .

 

Sincere thanks

 

Dave

 

 

Captive nuts (a sort of threaded tube which is put into a larger hole and squeezed up so that it becomes a permanent fitting in the roof- Google Rivet Nuts Examples ) would be fine, provided they are set in properly, so you will need a version that has a grip length covering the thickness of the roof. They have quite a tight tolerance on the size of the fitting hole so banging some holes in witha hand drill would need to be very carefully done or they just spin in the holes- creep up on the final size very slowly. They also introduce another joint to leak but you can put a security head bolt into them. AFAIK security bolts are available in A2 and A4 stainless.

 

Welding to the other side of sprayfoamed steel is OK, provided you don't overdo the heat input. On a boat roof you need to be careful about that anyway. On a continuous area the foam may droop a little, but can be pushed back up easily and sticks if held for a few seconds. If there is a hole by the welding area it will smoke a lot and char and I wouldn't inhale the smoke. Most sprayfoam seems to extinguish immediately and not to flame or to glow afterwards. Have an extinguisher handy and hang around for at least a hour after the welding finishes, just in case. If you got the doubler thick enough you would not need to make holes in the roof at all.....

 

If you can get the roof down to bare metal, and really, really clean (wash with aggressive detergent, rinse, repeat, rinse again, wipe with surgical spirit, add adhesive immediately) then Araldite (not Rapid) or other similar epoxy on a warm sunny day (in 2012?!!!!)would probably do well. You need to ensure that there is a small gap between the doubler and the roof but not bigger than about 0.004in though. Allow 3-4 days before touching it after it sets.

 

 

Alternatively, bolt each doubler pad to the roof with several M3 or M4 countersunk security screws, tapped into the roof, spaced about 25mm apart around the edges of the pad. A neoprene gasket, or some araldite under the pad, then drill and tap for the panel fixings. I have no idea of the panel mount sizes so I can't advise on what size doubler might be right. Easier DIY than welding, but a lot more work. (At this point the OP will turn out to be a coded professional welder!)

 

 

N

Edited by BEngo
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When I remove our magnetic based sat dish I have to use a strong levering action to break the grip, no chance if I used a direct pull which would be required if there were several magnets. Maybe fix dummy security or coach bolt heads to fool dickheads!

 

If panels are bolted using metal bolts inner ends will have to well insulated to prevent condensation dripping down, perhaps plastic bolts would be better?

 

Not wishing to detract from the original topic, but where did you get the mag-mounts for you Sat-Dish you mention. I use one of those ineffectual 6" x 6" flexible magnetic sheets and apply the suction mount on the Sat-Dish. I have never been too happy with it and try to keep my eyes open for something better.

 

Regards

 

Tony

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Rawlnuts?

 

These act like pop rivets but pulled up by the screw. They comprise a brass insert in a rubber sleeve, so may automatically provide the seal you want.

 

Google Rawlnuts for a photo - I would put a link on, but have to rush? back to 'work'

 

HTH

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... but not bigger than about 0.004in though.

 

Shome mishtake, shurely? Isn't that 1/256ths of an inch? You don't want to be mixing these new-fangled Frenchie decimals with good old Imperial units. ;)

 

I've bolted stuff to my roof with M5 brass bolts tapped straight in, and sealed with marineflex. Despite the wooden spacer shrinking and expanding (expanding mostly), it's not leaked yet (4 years, I think). The *%£@%&ing chimney, however...

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Not wishing to detract from the original topic, but where did you get the mag-mounts for you Sat-Dish you mention. I use one of those ineffectual 6" x 6" flexible magnetic sheets and apply the suction mount on the Sat-Dish. I have never been too happy with it and try to keep my eyes open for something better.

 

Regards

 

Tony

 

Look at timbodonkey magnet seller on ebay - - his stuff is ace

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I'm shortly to fix some solar panels to our cabin roof.

 

 

 

I'm not going to bother with a tilting panel system, but fix them firmly and in such a manner that it will be difficult for 'the light-fingered brigade' to help themselves to them when they wish

 

Before I drill holes into my precious roof, and terminally change its integrity, I'd appreciate observations on the best way of maintaining a waterproof seal (I know - other than 'don't drill holes! <_<)

 

I intend to fix a number of stainless steel brackets, using M8 security bolts (with passive coating), (as I cannot easily reach the underside of the holes, I shall tap the M8 thread).

 

 

Assembly: I'm proposing to employ a thin neoprene gasket between the brackets and the roof, finely coated with silicone each side, together with a small blob of silicone on the shoulders of the bolts prior to screwing in.

 

(I expect that the first time I unscrew these bolts will be when we repaint the roof!)

 

 

In your opinions - am I proposing to employ the best method of 'weatherproofing' the fixings?

I used Sikaflex 512 to fix a 140 watt solar panel fixing brackets to the roof of my camping car[ motor caravan] travel the roads at 65 mph[ were allowed]& in the 6 years since I fixed it no movement at all& no through roof holes

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Not wishing to detract from the original topic, but where did you get the mag-mounts for you Sat-Dish you mention. I use one of those ineffectual 6" x 6" flexible magnetic sheets and apply the suction mount on the Sat-Dish. I have never been too happy with it and try to keep my eyes open for something better.

 

Regards

 

Tony

 

When we abandoned our useless birdcage TV aerial I kept the magnetic base (expensive extra!) To protect the magnet from wet weather I bought a set of cheap stainless cooker ring covers and drilled one to enable the dish to be (stainless steel) bolted through that and the magnetic base which provided an effective rain shield for the base. Before bolting I removed magnet from its rubber shroud and gave it several thick coats of hull blacking to seal it followed by some touching up underneath (round the nut and bolt in the centre) Made a really sound job of it.

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I used Sikaflex 512 to fix a 140 watt solar panel fixing brackets to the roof of my camping car[ motor caravan] travel the roads at 65 mph[ were allowed]& in the 6 years since I fixed it no movement at all& no through roof holes

 

Thanks for the tip, I'm considering doing the same. What did you do with the power lead from the panel?

 

Regards

 

T.

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Lord Nelson's never been stolen from the top of his column so why not stick it out of reach on a long pole, it'd be more efficient too being nearer the sun. :rolleyes:

On my previous boat, a Harborough-marine with a fibre-glass top i made new wooden handrails and fixed them down with plated cavity wall bolts, that was 20 years ago, about a pound for 50 at Wicks. I kept that boat for 7 years afterwards and no leaks.

And to my knowledge they're still holding them on. :mellow:

Seriously though good quality S/Steel cavity wall bolts should do it,but i've never seen s/steel ones. :closedeyes:

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If the panels are sighted between two roof vents, the internal grills taken off so nuts can be offered up. If out of reach just stick the nuts and washers on a flat stick and offer them up with someone on top screwing the screws. Once the grills are off you can poke up and down with a thin rod to determine frame positions first.

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