Motorhome Solar Panel using TopSpeed System= Bad Idea?

[JasonHaws]

Top Speed mounts sold by Snap-n-rack say they are rated for wind speeds from 90-180 MPH. I'd like to mount 3 on each side of my 400 watt panels (68" x 45") on the roof of my motorhome. Is this a BAD idea? If so, why not? I want it to work but my desire for it to work may be impacting my judgement.


Thanks!!!

 

[RvNaut]

Link?

 

[HRTKD]

Here's a link to the Signature Solar page (which came up first in my search). The Snap-n-Rack's page is here.

I haven't used these mounts so this is just my opinion.
1. They do allow for some horizontal and vertical adjustment. As long as you install them right, you could later install a larger or smaller panel. The vertical adjustment would come in handy when the panel is installed on a section of the roof that is curved (front to back). I have this exact situation, so these mounts have really peaked my interest.
2. Installation with the Top Speed bracket should be faster than with Z-brackets. But is it twice as fast?
3. Most Z-brackets use two fasteners per bracket. The Top Speed mount uses four. That's twice as many holes on the roof. I suppose you could use just two screws but that probably would reduce their wind rating.
4. I prefer nut and bolt attachment at the solar panel for a mobile environment. Given the Rolling Earthquake nature of an RV, I want a solid attachment to the solar panel.
5. Due to obstructions, I had to raise the height of the panels along the center line of my roof. The Top Speed mounts and Z-brackets wouldn't work in that situation. Strut was the solution there.
6. My panels hang over the edge of the roof by a small amount. The Top Speed mounts and Z-brackets wouldn't work in that situation. Again, strut was the solution there.
7. It works with panels with frames 32 to 40mm thick. I was looking at a Qcell panel that was only 30mm thick. It could be argued that nobody in their right mind would use thin framed panels in a mobile environment so this probably isn't a concern.
8. The wind rating is definitely a concern. The more brackets you use the more secure the panel is. The wind rating on their website is "90-180 mph Wind Loads and 0-90 psf Snow Loads". I don't know how that compares to a Z-bracket or strut. I was planning to use six mounting brackets with my panels so six of these Top Speed mounts sound about right.
9. The Top Speed mount may be less expensive than using strut. Z-brackets would be much less expensive than the Top Speed mounts.
10. The Top speed mount is going to weigh less than strut (that shit gets HEAVY unless you use aluminum). Z-brackets weigh almost nothing.

I'm gearing up for installing a couple more panels on my roof in an area with fewer obstructions and I'm also using smaller panels that fit better. The plan is to use off-the-shelf Z-brackets or my own DIY brackets.

Perhaps @SignatureSolarJess can offer some insight into if their customers have used these mounts in a mobile environment.

 

[JasonHaws]

Those are good points. I wasn’t thinking about panels not being bolted to mount. Great feedback!

I like that they can be 3.5-4.5 inches above the surface so panels can go over a sun roof.
The holes don’t bother me as much with the top speed since they have a pocket to that will be filled with sealant and contained out of direct sunlight.

I also like the strut option which was my original plan.

 

[rogerheflin]

You would need to check to see if the screws are too long for an RV roof structure and/or if the RV roof has the right material in it for the bolts to grab into.

I used the snap-n-rack on my house roof, and they are pretty fast once you get the hang of it, and no leaks so far. I used them as directed and then on top of that put the sealant on any joints I could get to on the upper side edges and on top of all bolts for additional protection. No leaks as of yet, and it has rained a number of times and I have had snow on top of them.

 

[HRTKD]

I like that they can be 3.5-4.5 inches above the surface so panels can go over a sun roof.

I'm not completely covering the sunroof on my RV. The panel extends over the sunroof by a couple inches. My concern with going over the entire sunroof would be heat. Could the solar panel generate enough heat to melt the sunroof?

 

[JasonHaws]

That’s a good point. I think I saw a spec sheet that had a diagram of the bolts. There may be a chance I would have to cut the bolts shorter or go to the hardware store for a shorter size. Thanks for the feedback.

I'm not completely covering the sunroof on my RV. The panel extends over the sunroof by a couple inches. My concern with going over the entire sunroof would be heat. Could the solar panel generate enough heat to melt the sunroof?

I sure hope not. Hopefully there would be enough air flow between the two for heat to dissipate .

 

[brainbone]

I would have to cut the bolts shorter or go to the hardware store for a shorter size.

Regardless of bolt length, can the decking of your motorhome roof withstand the forces it'll be subjected to by the bracket? Imagine grabbing that bracket and shaking it violently while it's bolted to your thin motorhome roof... how long would it hold up before something begins to give? Struts would spread all that over a larger surface area.

Also, is your motorhome roof curved? If so, would these mounts work on a curved surface?

 

[HRTKD]

Regardless of bolt length, can the decking of your motorhome roof withstand the forces it'll be subjected to by the bracket? Imagine grabbing that bracket and shaking it violently while it's bolted to your thin motorhome roof... how long would it hold up before something begins to give? Struts would spread all that over a larger surface area.

With sufficient planning, at least one of the screws would be aligned with a roof truss. That's what I do with Z-brackets. But you're right that with strut you can (usually) hit every truss, resulting in a much stronger base.

Also, is your motorhome roof curved? If so, would these mounts work on a curved surface?

Should work. The concern there would be the difference in the angle of the mount and the angle of the panel. I had to deal with that when I used strut. I started out cutting my own aluminum shims (that fit within the strut channel) on the table saw. Got a prototype working pretty good and decided to use something simple instead.

 

[JasonHaws]

Regardless of bolt length, can the decking of your motorhome roof withstand the forces it'll be subjected to by the bracket? Imagine grabbing that bracket and shaking it violently while it's bolted to your thin motorhome roof... how long would it hold up before something begins to give? Struts would spread all that over a larger surface area.

Also, is your motorhome roof curved? If so, would these mounts work on a curved surface?

I'll need to do some looking to determine how the roof is constructed. I agree that strut's would spread the force over a much larger area which would take away that worry . I've wanted to find strut that is 3" tall so I can put the panels over the sun roof but I haven't had much luck.

If I had money to burn I would buy a system from monument-solar.com, but it's SOOOO Expensive!

 

[JasonHaws]

Regardless of bolt length, can the decking of your motorhome roof withstand the forces it'll be subjected to by the bracket? Imagine grabbing that bracket and shaking it violently while it's bolted to your thin motorhome roof... how long would it hold up before something begins to give? Struts would spread all that over a larger surface area.

Also, is your motorhome roof curved? If so, would these mounts work on a curved surface?

Each top speed is 7.24" wide with a middle base that extends 4.5" in the center. If I put 3 of these on each side, is the risk of failure still super high?

I wish someone else could be the first to experiment with this so i don't have to guess.

 

[brainbone]

Each top speed is 7.24" wide with a middle base that extends 4.5" in the center. If I put 3 of these on each side, is the risk of failure still super high?

I wish someone else could be the first to experiment with this so i don't have to guess.

I'd say reach out to the manufacture, but I'm pretty sure they'll just tell you they don't support non-standard installations.

It may work just fine, though if your roof has a curve to it, I'm not sure if the clamp that holds the panel can adjust for that very well.

If you already have a panel to test with, order a set and see how well it works just dry fitting it all.

 

[HRTKD]

I think that an answer from the vendor/company would be that the clamp works for an arched roof up to X° of arch. I suspect that the safe answer from the would be 0° of arch, as in it has to be a flat roof.

 

[0truck0]

Those brackets look like way over-kill so should hold until the panels themselves break apart or the roof rips out.
Use whatever length lag bolt or screw or nut and bolt set you need to to work on your particular roof.

Lots of folks on this forum seem to think we still drive on wagon wheels and that driving equals extreme shaking and vibration that nothing can withstand. No!! It is the same vibration and shaking that you experience sitting in the driver's seat, almost nothing worthy of mention.
The forces at play is the wind turbulence, slight, that will move the panels slightly. I have pointed out before that at 70mph the leaves and pine straw on the roof around my panels does not all blow out. It is not the same wind as your front bumper will see, wind on the roof is a mess of currents and eddies swirling. Roof does not see highway speed winds directly and even if it did is not enough to pull panels off unless they are just sitting there, and even then you might make it.

I would post a pic of how little VHB tape I have used to hold panels on that have been on for years and cross the country multiple times in horrible cross-wind conditions but it would set too many folks into a conniption just seeing it.
I have always used self-tappers to hold the panels to the mounts and NEVER had any ever come loose, and It is 3 or 4 little screws per 100w panel, sometimes 2 if that one is sandwiched between others. Nut n bolts are fine, but you have to deal with getting to the back side under the panel to hold the other end while you tighten so I choose the easy method. The purpose built brackets are great as they make it easy so not knocking them.

The roof of RV is of bigger concern. Is it a wooden roof with rubber membrane? Thats the worst of them all for solar. I hate holes in the roof but sometimes you have to. Use as few screws/holes-in-roof as possible, because even though u think it is a perfect solution for sealing out water it is not, water always finds a way in, one drop per week of water over time will rot out your RV.

 

[brainbone]

Lots of folks on this forum seem to think we still drive on wagon wheels and that driving equals extreme shaking and vibration that nothing can withstand.

Wind turbulence is a thing.

 

[0truck0]

Wind turbulence is a thing.

is not the thing people think it is. The roof is turbulent, not laminar. The forces just are not there as one imagines. There is push and pull but seems to be a lot less than everyone expects.
The wind hits the front of vehicle/trailer and goes up and over the first few feet of the roof, air moving forward even across the roof, and then swirls a lot in the middle and depending on length of roof may or may not settle down and flow normally. This is why leaves can stay on the roof a long time during driving.
Ever seen the back of a pick-up truck bed while driving and trash just swirls around the bed and never gets blow out? Strange things happen.
This is not like the dummies who strap their new mattress on top of their car over their windshield and DO see the forward wind trying to blow the mattress off, not at all like that. Campers and trailers usually do not have good airflow over the roof so that defeats the driving speed would-be winds and makes less forces pulling at roof objects.
Now, put your panels a foot above the roof as some RVers do (to clear other roof items) and you will have big issues, but an inch or two is not even close to compare that to.