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Old 01-09-2014, 17:35   #1
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Height of solar panel above Bimini

I'm adding a solar panel, 40" long by 20" wide, lengthwise to go over the Bimini.

I've installed two 1" rails across the Bimini. The solar panel will be directly attached to the rails.

Is there any rule of thumb that suggests how high above the Bimini canvas the bottom of the rail should be ? e.g., 2", 3", etc

Thanks.


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Old 01-09-2014, 19:02   #2
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Re: Height of solar panel above Bimini

It will sound silly perhaps but one thumb width.
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Old 01-09-2014, 19:09   #3
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Re: Height of solar panel above Bimini

When I built my rack for the solar, it was the intent to slide a couple paddle boards in under the panels.. havent tried it as of yet but its a great place to tie the fishing rods..
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Old 01-09-2014, 19:11   #4
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Re: Height of solar panel above Bimini

I haven't put one over a Bimini, but maybe you want to be sure the Bimini can't push on it from beneath? Again just mentioning it, I don't know.
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Old 01-09-2014, 19:41   #5
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Re: Height of solar panel above Bimini

Quote:
Originally Posted by Randyonr3 View Post
When I built my rack for the solar, it was the intent to slide a couple paddle boards in under the panels.. havent tried it as of yet but its a great place to tie the fishing rods..
So that looks like 3" to 4" clearance ?
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Old 01-09-2014, 19:44   #6
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Re: Height of solar panel above Bimini

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Originally Posted by Guy View Post
It will sound silly perhaps but one thumb width.
I guess you are trying to be funny ? Or is that a serious response ? If so, it seems awfully low. I would be concerned with the sunbrella roof of the bimini whacking the underside of the rails in some wind conditions ?

Is there an aesthetic distance ?
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Old 01-09-2014, 19:58   #7
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Re: Height of solar panel above Bimini

No, I'm not being funny. An inch works for many things when you are building stuff. The more stuff you build the more you find 1" is a good clearance. Rule of thumb?, maybe.
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Old 01-09-2014, 21:15   #8
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Re: Height of solar panel above Bimini

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Originally Posted by macbeth View Post
So that looks like 3" to 4" clearance ?
around 6"
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Old 01-09-2014, 21:52   #9
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Re: Height of solar panel above Bimini

I am planning to integrate the panels into the arch and get rid of the canvas. Rails, smoked plexiglas etc. Once the panels go up the bimini effectively becomes permanent and non-folding so why have a bit of canvas that's gonna wear out.

I mounted my 2 X 20w right to the bimini arch in contact with the canvas temporarily (for 2 years) - LOL.

I think as long as you have some airflow and things aren't fouling you are alright. 1 - 2 inches. Randy's idea of under panel stowage is interesting.
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Old 01-09-2014, 22:12   #10
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Re: Height of solar panel above Bimini

Many ways to skin a cat . . . .(provided you are not a cat lover)

I simply wanted enough room to get to the screws on the brackets with the canvas unzipped. Randy's setup looks very similar to mine.

FYI. 2x240w Sanyos.

YMMV.
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Old 01-09-2014, 22:21   #11
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Re: Height of solar panel above Bimini

Macbeth,
You ask a good question....and yes, there is a "rule-of-thumb"....
Quote:
Originally Posted by macbeth View Post
I'm adding a solar panel, 40" long by 20" wide, lengthwise to go over the Bimini.

Is there any rule of thumb that suggests how high above the Bimini canvas the bottom of the rail should be ? e.g., 2", 3", etc
The basic rule-of-thumb is, enough space to allow adequate airflow below (and around) the panels, as they do get hot when subjected to direct sun in the middle of the day / afternoon!!
Typically this going to be 4" - 8"...(6" is good)
Performance of the panels is reduced as the panel temp increases, so anything you can do to moderate the panel's temp (keeping it cool) is good....



A further criteria is having enough space so that the canvas, etc. doesn't hit the underside of the panels / brackets / etc...(a couple / three inches is usually enough for this)


So, as you see, for most boats / most installations, the real answer is:
6" is good....4" is minimum....anything more than 8" is probably a waste...

And, as an aside, the hotter climate and more hours of high sun angles, the more you'll need the airflow to keep the panels operating reasonably well...(heck, I've dumped buckets of sea water over my panels from time-to-time on long hot sunny summer days, and it does improve the output!!)
In the tropics, this IS important...
For most of the year, up in Canada you may not have panel overheating issues....but still try to give yourself 4" - 6" of space....



Have a look at the photos / article of my current solar array....(now about 8 yrs old, ~ 12,000 offshore miles, including two Atlantic crossings, 3 days sailing thru a Tropical Storm, multiple severe T-Storms, etc. etc..)

Solar Panels





I hope this helps...

Fair winds...

John
s/v Annie Laurie
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Old 02-09-2014, 02:21   #12
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Re: Height of solar panel above Bimini

I like that setup, especially if the panels can rotate 30 degrees or so. Also has space to slide stuff under as suggested.
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Old 04-09-2014, 19:15   #13
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Re: Height of solar panel above Bimini

Quote:
Originally Posted by ka4wja View Post
Macbeth,
You ask a good question....and yes, there is a "rule-of-thumb"....
The basic rule-of-thumb is, enough space to allow adequate airflow below (and around) the panels, as they do get hot when subjected to direct sun in the middle of the day / afternoon!!
Typically this going to be 4" - 8"...(6" is good)
Wonderful ! Thank you very much. I knew there had to be some sensible reason somewhere !!
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Old 04-09-2014, 20:27   #14
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Re: Height of solar panel above Bimini

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Originally Posted by macbeth View Post
Wonderful ! Thank you very much. I knew there had to be some sensible reason somewhere !!
That is pretty funny. Why is does 6" make sense? Why not 12"? You would probably have twice the airflow by that logic. The need for a 5 or 6" clearance is just an another opinion.
I have well over 6 feet and the volts still drop when they get hot.
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Old 04-09-2014, 21:02   #15
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Re: Height of solar panel above Bimini

Guy, et al,
I think some may be taking this a bit too literal / serious??
Quote:
Originally Posted by Guy View Post
That is pretty funny. Why is does 6" make sense? Why not 12"? You would probably have twice the airflow by that logic. The need for a 5 or 6" clearance is just an another opinion.
I have well over 6 feet and the volts still drop when they get hot.
First off, yes the output will drop when they get hot....and they WILL get hot in direct sun in the tropics, no matter how they're mounted...

But, Macbeth asked if there was a "rule of thumb", to which I replied:
Quote:
Originally Posted by ka4wja View Post
The basic rule-of-thumb is, enough space to allow adequate airflow below (and around) the panels, as they do get hot when subjected to direct sun in the middle of the day / afternoon!!

As for why 6" makes sense to me??
Yes, this IS opinion....and my opinion of having 4" to 8" of clearance allows for adequate space for any canvas movement and depending on your boat / superstructure / etc. should give you adequate airflow under average-sized panels.... (based on my present set-up/design and my experiences with solar arrays, starting back in 1983)...and takes into account the added structural integrity needed the higher up you mount them...
As well as, based on my desire to not increase weight aloft...nor have an un-aesthetically pleasing (ugly) set-up....etc. etc...


The above "6 inches" (or the 4" - 8") IS opinion....and opinions do vary...
And, in my opinion, having panels "well over 6 feet" above the bimini top would not only be ugly, but would require a rather large / heavy structure to adequately support the array....(but, what you decide for your boat is your choice/opinion....and what I decide/choose for my boat, is my opinion....and neither is right or wrong...just different...)



Now, I know that maybe I should've mentioned the above....but, Macbeth was just asking a simple question and I thought I'd give him a simple answer....
But, I'm glad it made you laugh as well...


Fair winds...

John
s/v Annie Laurie
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