Do you figure in the roof angle also?

If your seasonal winter setting for that area is 60, then you have to set the angle at 60 against horizontal level. What Mr. Wiz said.

If your roof already has South-facing 7 deg slope, then the panel should be set at 60-7=53 deg against the roof surface. To be exact, 53 against the tangent to the cambered roof surface.

If your roof has North-facing 7 deg slope, then the panel should be set facing South at 60+7=67 deg against the roof surface. Because the seasonal angle that you're getting from those websites, is against horizontal level.

But, because the aforesaid 60 number will change to a different number (likely, to a lower one) when you are not facing True South or True North, I think you could just ignore 7 deg slope, because the angle will be off anyway.

Mr Wizard,

Kind confused about this info, not sure what you are referring too.

Question,
If the sun (winter time values) is at 30* above the horization and my setting for this area/time is 60*.

Wouldn't I have to set the panel angle at 67* roughly, to get the proper panel angle? (allowing 7* for RV roof angle)?

MrWizard wrote:

the angle is too the Sun against horizontal level

Tia,
Don

Thanks guys,

The adjustment arms I made for the solar panels are adjustable for any angle depending on the length or width of the panel, without having any holes.

I plan on using the angle finder to get the correct angles on the panels when needed etc.

Tia,
Don

MrWizard wrote:
the few degrees of crown you might have on your roof

has NO real effect on the panels performance

Mr Wiz has managed to say the same as me in a very few words.

What I was trying to explain was that exact tilt angle becomes even LESS important when you are not facing True South, which is - probably - most of the time, for temporary camps. It also becomes DIFFERENT in this case.

the angle is too the Sun against horizontal level

the few degrees of crown you might have on your roof

has NO real effect on the panels performance

Why consider the roof angle at all? Use a level and protractor as a reference and mark the tilt bars every 5 degrees. Then set the panels based on location, heading and time of year.

I was just playing w/ my new tilt bars yesterday, and found that I am maxed out at 45 degrees, including 5 degree roof angle. I cut them strictly by guestamation. (could have been longer) But I also decided that angle will be close enuff, because I also found out that a 5-10 degree change was hardly noticeable on the amp meter. Its really not that critical

Assuming 8' width of trailer and 6" rise in the middle, the angle of the roof would be about 7 degrees. If your mounts are all the same height, the 7 degrees would be subtracted when tilt angle is referenced to the top of the mounts.

FWIW, i have a feeling that when using small amounts of solar (less than a KW), having Winter tilt angle off by a few degrees is not that meaningful in the greater scope of things. First, your batteries are going to be fully charged after two days in sun and the difference of a couple of degrees is going to be the difference of a few minutes of charging. I'm a big believer in getting every watt possible and not wasting a ma but storage considerations are different than daily use.

Ideally - yes. But this is not too important, roof angle is only 4-5 degrees. Don't forget, you should keep that 4 degrees slope when panel is lowered down onto the roof - to shed water and dust. When you calculated the optimum seasonal tilt according to that site (you probably mean Landau musings on Macslab site), it was for aiming strictly at the True South. Unless you are on a seasonal or permanent site, you are rarely facing South - or North, or East/West if your contraption is so sophisticated that allows 4 directions of tilt.

Not to mention that you - usually - don't know where the heck True South is in that particular location. Compass shows Magnetic South, which may differ 10 or 12 degrees from True.

You can of course calculate the roof angle and include this into your planned angle. Easy enough to do - 6" crown divided by panel width length will give you Cos, then go online and find the angle. Front and rear of trailer are usually sloped lengthwise, in addition to crown-sidewall slope.

Optimal angle for directions other than True South can be derived from PV Watts Calculator. Click on your planned location in the "colonies", or wherever you think you are going to be. If it won't let you put in panel watts in DC Rating, put your total W as if it were KW. Not important, because you only need relative numbers for monthly harvest.