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Old 11-02-2015, 07:35 PM   #1
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Retrofitting solar in a T1N Interstate

I'm psyched - our three panels arrived from AM Solar today, and now the DIY fun begins, because we have to design and install a mounting system.

With that in mind, if anyone out there has a T1N that came with solar from Airstream, could you please post a pic here, or PM me with it if you would prefer to remain incognito? Or if you had an upfitter install it, I would also like to see that. Neither my husband nor I have ever seen a T1N Interstate with the solar option - not in real life and not in the resale market. For reference, I'd like to see how others have accomplished it.

Our idea is to design a mounting system that vaults the panels above the A/C. I got this idea from having seen one T1N seller successfully vault his two kayaks over his A/C. The T1N Interstates came with an odd "roof rack" that is fabricated out of what appears to be some kind of ADA or hospital-grade stainless steel (it has surprisingly precise tolerances - we jokingly refer to it as the nuclear reactor piping). The rack in its present form is extremely good quality, but functionally useless for almost all purposes. I can't see us ever using it for anything truly roof-rack-able in the conventional sense, given that the A/C cover juts above the level of it. I've identified no reason why it shouldn't receive the solar panels, especially given that they are coincidentally the same width as the rack. Having them up that high would guard against the possibility of shadowing by roof appurtenances, which hasn't really been talked about much on this forum, but see Handy Bob for dire warnings on that issue.

Anyway, I'm looking forward to seeing what others have done, and/or what they have to say about these ideas. Thanks.
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Old 11-02-2015, 08:19 PM   #2
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You might also check on the Sprinter Forum as there is a lot of discussion re: DIY everything.
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Old 11-02-2015, 08:29 PM   #3
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One thing to watch out for, by "vaulting" the panel over the roof appurtenances, you will have a problem of uplift due to your slipstream. Whatever brackets you use need to be sturdy enough to resist that uplift force.

An angled "dam" in front of the panel, angling down and forward toward the roof, should help with that by deflecting air over the panel that otherwise would go under it. But leave a small gap between the dam and the roof to allow for vibration.
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Old 11-02-2015, 09:30 PM   #4
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I'm looking at about 4 different styles of tube clamps to attack to the roof rack. This is one of them:


I like this clamp because I'm thinking it might mate up easily to some 80/20 extruded aluminum brackets.
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Old 11-03-2015, 07:34 AM   #5
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Could you provide a source for these brackets? Thanks!
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Old 11-03-2015, 08:06 AM   #6
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Quote:
Originally Posted by LB_3 View Post
I'm looking at about 4 different styles of tube clamps to attack to the roof rack. This is one of them:

.... I like this clamp because I'm thinking it might mate up easily to some 80/20 extruded aluminum brackets.

That is an awesome clamp. Looks like you could easily mount your panels above the A/C unit with that roof rack. Then add an air dam on the front of those rack bars to push the air flow over your panels as suggested by Protag.

Which solar controller did you buy? If you follow HandyBob you probably discovered he doesn't like the Blue Sky units sold by AM Solar.


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Old 11-03-2015, 02:04 PM   #7
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What size panels did you get?
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Old 11-03-2015, 05:31 PM   #8
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BUGS, my hubster did the sourcing, but I believe they are the same panels Lewster talked about on another thread - the ones that are no longer being manufactured. And I just noticed that they went on sale immediately after ours were delivered... hmmm...

GS100 Solar Panel | Solar Panels

BOXSTER, the packing list says "Bogart SC-2030 30A solar controller", plus a temperature sensor called "TS-2 for SC-2030".

PROTAG, you are correct about lift. Fortunately, LB_3's senior engineering project in university was a wind tunnel model which hangs in our garage to this day (behemoth that it is). So we've got some process knowledge on that issue.
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Old 11-03-2015, 07:54 PM   #9
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Originally Posted by Jbray333 View Post
Could you provide a source for these brackets? Thanks!
4 Wheel Parts has the clamp I showed above. I'm not certain that the mounting flanges come with them however. Here is the pic again with a link below:

Trail Gear - Tube Clamps | 4WheelParts.com


Here is one sold to mount lights and speakers on Wake Board cages:

Krypt Wakeboard Tower Clamps - 1 1/4", 1 1/2", 1 5/8", 1 3/4", 1 7/8", or 2".


These are pretty clever and expensive:

Amazon.com: Rugged Ridge 11031.02 Black X-Clamp for 1.25-2" Tube Bumper Roll Bar and Cage Accessory Mount 2-Piece Kit: Automotive
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Old 11-03-2015, 08:01 PM   #10
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Originally Posted by Protagonist View Post
One thing to watch out for, by "vaulting" the panel over the roof appurtenances, you will have a problem of uplift due to your slipstream. Whatever brackets you use need to be sturdy enough to resist that uplift force.

An angled "dam" in front of the panel, angling down and forward toward the roof, should help with that by deflecting air over the panel that otherwise would go under it. But leave a small gap between the dam and the roof to allow for vibration.
I just installed two of the GS-100 panels on my AI, one of which is at the front of the roof. Although mine only has an inch or so of clearance to the roof I was concerned about the air flow under the panel so I ordered an Auto Ventshade Model 77005 (sunroof air deflector) which is about an inch longer than the panel and around 3" high. Should solve the problem in my case although it's not what the poster needs. I do agree with Protag's recommendation for some sort of air dam or deflector.
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Old 11-03-2015, 11:08 PM   #11
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Which solar controller did you buy? If you follow HandyBob you probably discovered he doesn't like the Blue Sky units sold by AM Solar.
As Interblog notes, I chose the charge controller designed by the guy that makes the trimetric meter. It's not the most sophisticated model (no MPPT) but if I learned anything from buying Apple products,it is that if you just want something that works, getting devices designed by a single shop is a great place to start.

Expectation management is critical to the success of any project and this is where my first failure lies. I never should have let Interblog see the panels because she is starting to get excited about being able to recharge our battery without driving or starting the generator. But that isn't what this project is about.

We're replacing our refrigerator this weekend since it doesn't operate on shore power and I've finally given up on it after replacing both circuit boards with no results. When I take the old fridge out, I intend to pre-wire a combined box on the refrigerator vent in order to route the solar power cables down into the coach.

I purchased the combiner box and charge controller with that scope in mind. But since Lew mentioned the smaller panels from AM Solar being perfect for our smaller vehicles, I figured I should pick those up as well before they are sold out.

Now I have to hurry up and figure out how to loft these things up above the AC before Interblog loses her patience with this project. :-)
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Old 11-03-2015, 11:36 PM   #12
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I just installed two of the GS-100 panels on my AI, one of which is at the front of the roof. Although mine only has an inch or so of clearance to the roof I was concerned about the air flow under the panel so I ordered an Auto Ventshade Model 77005 (sunroof air deflector) which is about an inch longer than the panel and around 3" high. Should solve the problem in my case although it's not what the poster needs. I do agree with Protag's recommendation for some sort of air dam or deflector.
Lift from your front, nearly surface mounted, panel is probably not a concern. AM solar has installed hundreds and maybe even thousands of panels using only double sided tape and their customers have never reported a failure if their website is to be believed.

There are several ways to calculate lift on an object. The first and most obvious it to calculate the pressures over the top and bottom of a surface then multiply by the area and you get a lifting force.

Bernoulli tells us that faster moving air exerts less pressure so we can conclude that the faster air over the top of the panel from the clean slip stream will result in lower pressure on the top than the slower air under the panel. This will result in a net lifting force on the panel.

Another way to calculate lift is to look at the change in momentum of the entire flow field. Since Newton tells us to expect a lifting panel to have an equal and opposite reaction on the air flowing past it. To generate lift (upward force), the flow field has to be turned (deflected) downward. As a result, we can determine the lift by calculating the mass of the air that is being deflected by the panel as the air flows past it.

Since your panel is horizontal, there isn't going to be all that much air being deflected and the fact that the panel is low to the roof limits how far you can bend the flow field since the roof will just straighten up the flow again. This interaction of the two surfaces really limits how much lift can be generated by the horizontal panel.

Now mounting a panel 12" above the roof like ours will allows for much more air to be deflected and lift to be generated.
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Old 11-04-2015, 10:19 AM   #13
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I just received an email from Costco and they have Grape Solar 100 watt panels for about $135 as an online sale. Don't know if they are the same ones from AM Solar but seem to be a good deal.

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Old 11-04-2015, 10:51 AM   #14
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I just received an email from Costco and they have Grape Solar 100 watt panels for about $135 as an online sale. Don't know if they are the same ones from AM Solar but seem to be a good deal.

Dennis
I'm having LB_3 check this out (he's at work this morning but I am not). Description seems like it, but pic is not the same item.
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Old 11-04-2015, 10:55 AM   #15
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One can calculate lift on something like a solar panel or other planar element of similar aspect ratio, OR, one can drive down IH-45 and get an empirical feel for the phenomenon by observing nonsense such as this:
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Old 11-04-2015, 11:23 AM   #16
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Re: solar in general - So how do owners of Interstates with existing solar systems clean their panels? I'm assuming this needs to be done routinely?

Right now, I have a giant splat of bird poo on top of my A/C cover. If our panels were installed, then it would be shading in a way that would kill the efficiency of the panels until such time as it was removed. In our area, we have a large assortment of marine and estuarine birds - waterfowl - all of which excrete profusely. This kind of bird splatter is inevitable. Even without it, I've noticed that our roof gets dirty very quickly, with general grime.

This is one of the reasons why I wanted the ten-foot version of Telesteps. I'm assuming I'm going to have to get up there routinely to clean, possibly while on the road, especially given that I want the most remote boondocking locations that I can manage to find (which tend to have the most birds). Here's another pic with the Telesteps in place with the pipe wrap to protect the side of the Interstate, and also I've begun using a rubber bungee to lash it securely at the top. I'm quite pleased with it. I find it very comfortable getting on and off the roof.
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Old 11-04-2015, 11:30 AM   #17
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Retrofitting solar in a T1N Interstate

Quote:
Originally Posted by dennis3751 View Post
I just received an email from Costco and they have Grape Solar 100 watt panels for about $135 as an online sale. Don't know if they are the same ones from AM Solar but seem to be a good deal.

Dennis

They are NOT the GS-100 panels. The only ones Grape Solar has not are considerably larger.


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Old 11-04-2015, 11:44 AM   #18
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They are NOT the GS-100 panels. The only ones Grape Solar has not are considerably larger.


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Correct - my husband noted that those offered by Costco are different sizes and also it's a question of monocrystalline (more expensive) vs. polycrystalline (less expensive)... I haven't checked the spec sheets but I wonder if the Costco version is not as efficient as a result.
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Old 11-04-2015, 01:35 PM   #19
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Yes, these are not the same as AM Solar's panels. These are indeed the polycrystalline model. I did install one of these on my AI to replace the puny 50 watt panel. It is a bit larger than the monocrystalline panels and that required me to add standoffs to clear the bathroom vent, in that I could not avoid it with that panel. It works as specified. I have since purchased 2 of AM Solar's panels, along with a MPPT controller....and all the accessories.... Their ratings are very close and I will expand my project soon. We will see how they play together soon.
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Old 11-04-2015, 06:18 PM   #20
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In order to derive maximum output from any MPPT controller, all panels should be within 0.2 VDC of each other in their output voltage.

Greater differences in output voltage will confuse the MPPT module during it's sampling and will result in decreased solar charge boost, or even none at all.


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