When I was installing my solar panel, I wondered where to install it so that I could:
1. get at it to clean the surface.
2. be able to tilt the panel to get maximum exposure to the sun.
3. not drill any more holes in the trailer (less chance of leaks).
I ended up putting the solar panel on the rock shield. I had to put a lightweight aluminium bar under the rock shield so I could attach the lower part of the panel. I did not have to do much more work than that. After 3 years of use there is no sign of sagging -- the support is still holding up the solar panel quite well. I am able to tilt the solar panel, get at it to clean the surface and did not have to drill any hole.

There is a bit of disadvantage as the solar panel can only face one direction when I am camping. I have not had any rock debris hit the panel hard enough to cause any damage. I have travelled on a few gravel roads.

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Fred........

That looks like a good solution to roof mounting.

I am suprised no rock chips have hit it tho. They must be tougher than they look!

Nevin Lescher mounted the solar panel for his Scamp on the gravel shield -- Don't forget that the shield is removable, so with an extension cable, it's possible to park the trailer in the shade and have the solar panel in sunlight at whatever angle you wish.

Regarding rock damage, I am surprised to find very, very few scratches on my gravel shield (esp compared to the lower front edges of the egg) -- My trailer's been up and down the East Coast, the Canadian Maritimes, across the country three times and on almost every 'highway' in Alaska, Yukon Terr and B.C., so it has certainly been exposed to a lot of road trash and many thousands of miles of gravel roads -- Based on my experience, I would not hesitate to put a solar panel on the gravel shield.

Good quality solar panels are tough so they can withstand hailstorms.

I keep mine on top so that it's away from my fumbling hands. I broke one of the lilttle battery charger types. They are fragile.
I tested the big panel before putting it on top and according to the meter it didn't matter too much how accurately the panel was aimed.
Its easy to wash on a short ladder with an RV brush.
I wouldn't want to lose my view from the big window.
Great not to have to use my generator. I lugged it around for three years. No use.

Jim, was the meter measuring voltage with the panel not connected to anything (open circuit), or current while the panel was charging a battery (under load), or some other situation? I'm sure a few degrees won't matter, but the aim must matter, and it would be interesting to learn a little more about how much it matters.

Just the meter & panel connected. Meter dipped if I turned panel 90 degrees off center.

In the ball park is good enough for most needs. At least, mine works with my meager draws.

I never precision aim my panels.. I point towards the sun at about a 45 degree angle and leave it at that. Sometimes I lay the array flat if there is no fire danger (The back of the panels do get very hot and we are paranoid around here)

Folks with roof mounts don't have any options for "pointing", and seem to be happy anyway.

If I was trying to power my home, I would pay more attention to precision installation.. but for camping.. not so critical.

I suspected that. With nothing connected there would be no current flow, so the measurement must be voltage. The voltage with no load means very little.

Imagine you had a panel - any size - and it put out 18 volts (yeah, I know, we all bought the panels to charge "12V" batteries...). Then you put another identical panel beside it and connected the two in parallel (+ to + and - to -); you would get the same voltage... but hey, there's twice as much panel!

Now do the same thing - try one panel then two - but this time have them hooked to a battery that needs charging, and measure the current (amps) which flows (with no controller). I bet adding the second panel gives a big increase because there is twice as much panel collecting light, and thus twice as much power pushing into the battery. Warning if you try this: inexpensive multimeters routinely have low current capacity (mine is 10A), and large enough panels (like bigger than most of us are likely to ever have) could exceed that.

Another way to illustrate the same thing is to compare a small panel and large panel of the same design and construction: they will likely produce the same voltage, but connect them to a load and of course the larger panel can deliver more... area matters, and open-circuit voltage doesn't say much.

Sorry, I can't give concrete numbers, because I haven't done this, because the panels are not cheap and thus I only have one.

Having the panels not perpendicular to the line to the sun is sort of like having less panel, because it catches less light; it has less "effective area". Of course, not all the light comes straight to the panel (they work surprisingly well in the shade, where all of the light is coming indirectly, from all directions), and that's why it would be interesting to know how much the output varies with aim, in full sun and in shady conditions.

I'm not questioning that the rock guard idea works - it sounds like a clever idea to me - I'm just trying to pin down how much can be gained by aiming better, and see what I might be missing in my understanding of the factors involved.