Which screws for solar panels, and which configuration?

Spaceman Spiff · Jul 20, 2017

tx2sturgis said:
. . . But there IS a low pressure zone up there that's trying to lift the vent cover or solar panel, (due to the higher pressure underneath) same thing that happens with an airplane wing.

Thanks for the video. That is one I haven't seen.

The problem with your wing analogy is a wing does not have a barrier (the roof) 1 or 2 inches under it keeping the air from rushing up from below (which is what gives the wing lift). Vent cover is different as it has a large volume of air under it (the inside of the vehicle), possibly at higher pressure trying to get out.

If the airflow in the video is to scale, a solar panel close to the roof would be well inside the low pressure area which looks like it is constant pressure (at least in the macro sense). The turbulence would be very hard to predict.

Back to my initial contention: I do not think that mounting the panels at a slight angle facing forward does anything (it probably doesn't hurt either). A quarter of an inch on a 16 inch wide panel is less than 1º tilt.

-- Spiff

tx2sturgis · Jul 20, 2017

Spaceman Spiff said:
If the airflow in the video is to scale, a solar panel close to the roof would be well inside the low pressure area which looks like it is constant pressure (at least in the macro sense). The turbulence would be very hard to predict.

Back to my initial contention: I do not think that mounting the panels at a slight angle facing forward does anything (it probably doesn't hurt either). A quarter of an inch on a 16 inch wide panel is less than 1º tilt.

I guess we de-railed this train somewhat.

Unless the panels are overhanging (or very close to) the front edge of the vehicle, or mounted on tall standoffs, the air pressure under the roof mounted panels, or vent cover, which is fairly stable and lower velocity, is higher than the air pressure above the panels, or vent cover, when the vehicle is traveling at any normal road speed, thats whey they will be subject to a lifting force. Observe an old soft top convertible going down the highway sometime....the ragtop gets lifted into a 'dome' shape.

Bernoulli's principle. Google it. It's basic 8th grade physics. Or used to be.

I was not commenting on panel angle one way or the other. Mounting panels level is fine, or tilted a bit forward is also good. I always mount mine level and very close to the roof.

I guess we will agree to disagree but we kinda need to get back to the topic at hand.

Sorry Miss Dune!

DuneElliot · Jul 21, 2017

No worries. I read through it all, despite some of the recent stuff not being so applicable to my set-up. I think I know what I am going to do as far as mounting...and KISS it. I don't want to make it more complicated than it already is. I have less than two weeks before my 5W becomes my full-time dwelling and I know I'm not going to get everything done between now and then.

GotSmart · Jul 21, 2017

tx2sturgis said:
Here is a typical application chart for the VHB type of tapes...'low adhesion' is a concern.

Lets cross those off the list for a rubber roof and not lose those panels.

In my real life experience, that is bad information. I could not pull off the VHB panels from the roof. None the less, I put braces in place using a different adheasive.

But then I go to extremes in surface preperation.

The rubber roofs I have encountered have all covered material that screws will not grab into.

Weight · Jul 21, 2017

Got smart. yes. That is why I used through bolts with various lock, flat, and fender washers.

GotSmart · Jul 21, 2017

When installing a top of the line system in a nice rig, there are things that never ever get done. Ozark engineering is not an option.

There is way too much bad advice being given on this forum.

You Tube is not a credible source.