Bolting solar panels to rails through roof?

[Byron]

Hi all,

Just wondering, do folks use self tapping screws, or drill through roof support beams and lock them into place with nuts on the interior side of the roof?

[TheHubbardBus]

There are countless ways to mount panels to your roof. You'd be well served to search the forum and people's builds within it to get ideas regarding the possibilities. If the only thing you wish to do is mount brackets for panels - and no other structure will be on the roof that would serve as a better thing to mount them to - I personally wouldn't trust self-tapping screws into sheet metal. But that kind of depends on how many you were planning to use.

Bolting through the rails (hat channels / ribs) is certainly an option. We built a rack system upon which our panels are to be mounted (in the next couple weeks, matter of fact!). It doesn't bolt through the rails, but rather on either side of them. Again, there are tons of ways to do this. Just make sure whatever method you choose takes into account the considerable legal/moral consequences you may encounter should a panel blow off your roof and into the windshield of whoever may be behind you.

[fo4imtippin]

some folks use self tappers, but i would only do that as last resort and if i did, i would angle the panel for downforce at highway speeds.


If you have access to the inside of the hat channel, then push the bolt up through the hat channel and use locknut or locktight on top. use a square carriage bolt through a square hole, or tackweld the bolt on the bottom.


I'm currently torn on doing mine this way, or building a U shaped frame and bolt through the window channels.

[Drew Bru]

We used BlindBolts into the ribs, but if we'd removed the ceiling I'd have bolted all the way through and used carriage bolts with nylon locknuts. The Blindbolts have held up fine though, no sign of them coming loose in 2 years of use. I don't think I'd trust self tappers...they might be fine but the Blindbolts weren't outrageously expensive and were pretty simple to install.

[HamSkoolie]

With self tapping screws into sheet metal you have ONLY the thread surface (of one revolution) of the screws to provide holding power. Constant vibration from both road way and aerodynamic buffeting as you go down the road will be acting on each and every one of those threads as well as the sheet metal they are in and WILL eventually cause them to fail.

I would use at minimum grade 5 bolts with some means to spread out the load on the underside of the sheet metal. Going through the hat channels will do this.
Also, if you are using bolts and nuts I would recommend that the bolt goes UP from the bottom and is tack welded in place in case you need to tighten or make adjustments in the future.
I'm not an engineer but I did stay at a Holiday Inn once....LOL
Actually, I've just dealt with a lot of mechanical stuff and seen both good, poor, and BAD ways to do things....not to mention downing aircraft because a bolt was installed the wrong direction.

[Byron]

Thanks to all for applying so quickly. I had planned on drilling thru the beams, channels, etc. Just wanted to know if there was anyone trying it the way a well intentioned neighbor suggested. I might try self tappers sealed up with silicon, but thats as much as I’d trust them. Thanks again.

[fo4imtippin]

Originally Posted by Byron

Thanks to all for applying so quickly. I had planned on drilling thru the beams, channels, etc. Just wanted to know if there was anyone trying it the way a well intentioned neighbor suggested. I might try self tappers sealed up with silicon, but thats as much as I’d trust them. Thanks again.

Dont use Silicone. Use Dicor or some other lap sealant. You could also use Lexel or something that bonds well to metal. Silicon might work fine initially, but nothing will bond to it(even more silicon) if you have to reapply.

[mmoore6856]

quote
Also, if you are using bolts and nuts I would recommend that the bolt goes UP from the bottom and is tack welded in place in case you need to tighten or make adjustments in the future.



i drilled out some rivets on many hat channels and put my bolt thru from the outside then tack welded the nuts on the inside to the hat channel. after it cooled i put a o ring under the bolt to seal the hole til i get the solar panel brackets made

[mmoore6856]

Originally Posted by fo4imtippin

Dont use Silicone. Use Dicor or some other lap sealant. You could also use Lexel or something that bonds well to metal. Silicon might work fine initially, but nothing will bond to it(even more silicon) if you have to reapply.

and silicone does not always adhere to painted surfaces

[HamSkoolie]

Originally Posted by fo4imtippin

Dont use Silicone. Use Dicor or some other lap sealant. You could also use Lexel or something that bonds well to metal. Silicon might work fine initially, but nothing will bond to it(even more silicon) if you have to reapply.

Beat me to it on the NO SILICONE
I would use PL-3x or SikaFlex. They are polyurethane, stick well, have 35% or more elasticity, and many other good qualities. They do require acetone for cleanup but no big deal. We sealed our windows as they went in with copious amounts of PL-3X that squished out around the outside of the exterior window frames as we wanted. We then used a plastic 4" putty knife to scrape the vast majority of the excess out then nitrile gloves and acetone wetted disposable shop rags to wipe the remaining overflow off. Left a nice "bead" around the window and we know we're sealed for at least a decade.

[HamSkoolie]

Originally Posted by mmoore6856

quote
Also, if you are using bolts and nuts I would recommend that the bolt goes UP from the bottom and is tack welded in place in case you need to tighten or make adjustments in the future.



i drilled out some rivets on many hat channels and put my bolt thru from the outside then tack welded the nuts on the inside to the hat channel. after it cooled i put a o ring under the bolt to seal the hole til i get the solar panel brackets made

That will work but tack welding the nut has more potential to warp the nut and cause difficulties getting the bolt to go through. Pretty hard to warp the bolt head....that's the only reason for doing the bolt head so if your skills are sufficient (for penetration into the nut without distortion)....some of yo need to get your minds out of the gutter RIGHT NOW...... go for it.

[mmoore6856]

Originally Posted by HamSkoolie

That will work but tack welding the nut has more potential to warp the nut and cause difficulties getting the bolt to go through. Pretty hard to warp the bolt head....that's the only reason for doing the bolt head so if your skills are sufficient (for penetration into the nut without distortion)....some of yo need to get your minds out of the gutter RIGHT NOW...... go for it.

3 tacks on a ss nut does not warp any. just got to know how to weld as warping is not a issue to a good welder

[HamSkoolie]

Originally Posted by mmoore6856

3 tacks on a ss nut does not warp any. just got to know how to weld as warping is not a issue to a good welder

And how many good welders do we have on this forum as opposed to how many bought a Harbor Freight flux core 110 volt welder and have no concept of proper penetration, distortion avoidance, destruction of metalurgy properties, etc.?
Toss in that there's a good chance the nut will be galvanized......might even be a nylon insert lock nut. Or a purposefully distorted lock nut that could also lose it's retention capabilities.
There are simply too many variables to assume "good welding". I wouldn't even assume mediocre welding as I've seen plenty of pretty welds with zero penetration. Without some training, there's no telling how effective the weld is likely to be.

[Veloc]

A while back I installed Cadillac seats with the integrated seat belts into an old pickup designed to use side mounted belts. Part of the job required replacing the floorpan, which was replaced with thin sheet metal. It was thick enough to work but thin enough that it required grooving to make it stay flat. The metal was likely at least as thick as a bus roof. I was concerned with whether or not the seats would hold in an accident since the truck's floor never was designed for this, and the metal that replaced it was about as thick but not quite. I reinforced the seats with a 1.5in flat bar of steel from Home Despot, underneath the floorpan, that stretched across the floorpan to about 2 inches past the rear seat bolts. Later on, I wrecked the truck when an idiot thought a 2 way stop was a 4 way stop and pulled out in front of me when I was about 30 feet from the intersection going 40MPH. 40MPH to 0MPH in 8 feet, because I hit the brakes about the same time I T-boned the car and as it had just rained I had 0 traction. I weighed in at about 240lbs back then, and the seats were another 100lbs each, and the floorpan didn't show any sign of buckling.

The point behind this rambling story, bolt through the roof, use at least 3/4 inch diameter bolts, and run a strip of steel flat bar stock underneath the roof connecting each bolt, and nothing's coming off the roof.

[mmoore6856]

Originally Posted by HamSkoolie

And how many good welders do we have on this forum as opposed to how many bought a Harbor Freight flux core 110 volt welder and have no concept of proper penetration, distortion avoidance, destruction of metalurgy properties, etc.?
Toss in that there's a good chance the nut will be galvanized......might even be a nylon insert lock nut. Or a purposefully distorted lock nut that could also lose it's retention capabilities.
There are simply too many variables to assume "good welding". I wouldn't even assume mediocre welding as I've seen plenty of pretty welds with zero penetration. Without some training, there's no telling how effective the weld is likely to be.

Wow you really want to stroke this out and scare them away

[HamSkoolie]

Originally Posted by mmoore6856

Wow you really want to stroke this out and scare them away

Not at all. Remember that you yourself stated that warping isn't an issue to a GOOD WELDER.
The welding skills required in building a skoolie are far closer to the "tack and gob" skill level than the guy on Wake Island who got us out of there by welding an exotic fuel manifold that couldn't be replaced and wasn't supposed to be repaired. That guy had mad skills with a tig and we all knew when he said "it's good", that it was.
That said, there still needs to be some minimal understanding of metallurgy, penetration, over penetration, and what's happening when that arc is struck.
Remember, that roof rack is exposed to 60+ MPH winds, potentially upward aerodynamic forces, and vibration. With too much heat and penetration those grade 5 or 8 bolts and nuts aren't any more. Not enough penetration and the whole reason to weld them is lost.Training doesn't have to be a semester long vocational course, just some time spent with someone who does know welding and a little practice under their tutelage.

[Jolly Roger bus 223]

Originally Posted by HamSkoolie

Not at all. Remember that you yourself stated that warping isn't an issue to a GOOD WELDER.
The welding skills required in building a skoolie are far closer to the "tack and gob" skill level than the guy on Wake Island who got us out of there by welding an exotic fuel manifold that couldn't be replaced and wasn't supposed to be repaired. That guy had mad skills with a tig and we all knew when he said "it's good", that it was.
That said, there still needs to be some minimal understanding of metallurgy, penetration, over penetration, and what's happening when that arc is struck.
Remember, that roof rack is exposed to 60+ MPH winds, potentially upward aerodynamic forces, and vibration. With too much heat and penetration those grade 5 or 8 bolts and nuts aren't any more. Not enough penetration and the whole reason to weld them is lost.Training doesn't have to be a semester long vocational course, just some time spent with someone who does know welding and a little practice under their tutelage.

ok ham.
i understand your opinion on the welding and warping of the nut.
but i have an opinion?
first off let me say OOHRAH i still live and work on all the bases in eastern nc
after being a grunt and recon swimmer.
i have been a certified welder for pipe and structural since 96 and still supervise that operation today.
i support the advise of if you use through bolts to put the bolt inside and tack weld if you cover them and you should go metal to metal.
wood is to soft and would need to be re tightened over time as the bolt wears into the wood.
now on to the welding stuff.
yes practice and proper penetration is key but we are talking about tacking a whatever whoever uses nut to lesser metal?
we would actually have to look at each specific install to be able to give the best advice.
tacking a nyloq nut negates the purpose of buying it.
a wire welder will not burn through the coating on a galvanised nut unless you grind the coating off but then you not galvanised anymore.
and the galvanizing paint never matches because it is a cold galvanized.
i will be using blind bolts because my wifes bus ceiling did not come down but if it had?
bolts from inside out tacked with nyloq nuts and thread lok blue.
i know the red to and it aint going on them but in restropect it might be the best use for it

[HamSkoolie]

Originally Posted by Jolly Roger bus 223

now on to the welding stuff.
yes practice and proper penetration is key but we are talking about tacking a whatever whoever uses nut to lesser metal?
we would actually have to look at each specific install to be able to give the best advice.

Ahhh but there's the rub....you and I and many others know this but MANY don't. And did the nuts get bought from the cheapest place available (probably) and what alloy are they? Galvanized (later on)

Originally Posted by Jolly Roger bus 223

a wire welder will not burn through the coating on a galvanised nut unless you grind the coating off but then you not galvanised anymore.
and the galvanizing paint never matches because it is a cold galvanized.

I'm not so sure about a wire welder not burning through galvanized coating on a nut. Or do you mean without really nailing it?
And yes, no longer galvanized. The welds of the roof bows to the lower structure of my '96 AmTram are some UGLY things to look at. Welding galvanized and no clean up...just black nasties.... but they seem to have held all this time. I guess if the customer couldn't see it.....

Originally Posted by Jolly Roger bus 223

bolts from inside out tacked with nyloq nuts and thread lok blue.
i know the red to and it aint going on them but in restropect it might be the best use for it

I prefer the nuts that are physically distorted to nylocs but then I also use a split lock washer and locktite. Red's not a big deal on anything you can put an impact on. But don't use it on tiny screws unless you mean it.



It's all good. We all go about things differently.
Sorry about you being in sand flea land.....eeeeeew..... as I lower my Hollywood sunglasses. (GRIN)

[Jolly Roger bus 223]

sorry you never got out of hollywood marine?
started there done that.
loved the mexican food in carlsbad/oceanslime/sandiego but i was a texas marine to begin with.

[HamSkoolie]

Originally Posted by Jolly Roger bus 223

sorry you never got out of hollywood marine?
started there done that.
loved the mexican food in carlsbad/oceanslime/sandiego but i was a texas marine to begin with.

Oh my Hollywood sunglasses came in handy. I figured get teh overseas tour out of the way so I put in for overseas......and actually got what I asked for!!!!
Back then Hawaii was considered overseas..... oh twist my arm. I was signed up for SCUBA lessons the day after I arrived!