Roof racks - good, bad, and horror stories

[VanTalk00]

Currently, I have some pretty ambitious plans for my van roof.  See the photos below.  The first is the ultimate goal, with fan, removable solar panel, tilting panel, water tubes, and not-weather-proof storage under the panel - all wrapped with an enclosure to keep the wind from lifting everything.  The panel and tube rack is shown in the second image.  The red dots are the current mounting bolt holes on the roof.

Now I'm contemplating how to achieve this wrap around, and that's where I'm starting to get nervous.  Seems like you need a frame to "skin" with aluminum or steel sheet metal. (Hopefully, aluminum sheet metal works.) So should this wrap-around assembly be connected to the current mounting brackets?  Are they strong enough to hold the whole thing?  Where else to mount?  How are commercial "tops" attached to a van roof?  What works?

What has been people's experience with roof racks - especially enclosed ones?  What are the biggest pitfalls to watch out for?

Thanks,

Jim

 

[B and C]

I don't have one or any experience with one. That being said, you will need a way to fasten the panel down for traveling. Windflow up and over it will cause a low pressure area and try to lift it. The higher the wind speed. the greater the lift. Think airplane wing.

I saw someplace where a woman did an enclosed rack with wood but her panels did not tilt. This was on a minivan.

 

[ckelly78z]

Having your solar on the roof will always mean that you have to park your rig in the sun to get best results. This will mean better power accumulation, but also higher temperatures inside of the living space, which might require some of that power to help cool you...a rather catch 22 situation.

You may still want this, but consider running a shade awning off of both sides to keep the beating sun from boiling you out.

Another option is to park in the shade, and have moveable panels on an umbilcal cord in the sun, where they can be adjusted to the suns angle throughout the day.....these are just my random thoughts, so take them with a grain of salt !

 

[VanTalk00]

Another option is to park in the shade, and have moveable panels on an umbilcal cord in the sun, where they can be adjusted to the suns angle throughout the day.....these are just my random thoughts, so take them with a grain of salt !

Yes, that's why the panel frame is open on the end pointing up. That way, I can extract it and tether it 20 or 30 feet away.  When the panel is "closed" - no tilt, the panel is secure.  

The enclosure prevents wind from getting underneath to lift the panel, while providing  "hot" storage under the panel (put cables, ropes, tarps, and other lightweight items tolerable to wetness). The elevated panel ensures no shadow from the fan or tubes.  See the attached.  Not shown are the clear plastic and insulation that will surround the water tubes or the sheet metal that will cover the area around the fan.

 

[Gr8ful]

I'm doing my panels, batteries, controller all on a tilt 101" x120" a deckover aluminum snomachine trailer pulled by the ambo with a 250 amp altenator. They will tilt & if hooked up or cloudy the ambo or genset will charge them. I'm also going 28' of 6" pained black pipe for the hot water.

 

[VanTalk00]

Great!  Love to hear more.  Got any pix or plans?  Are you enclosing the trailer?  How are you mounting everything? What are the hot water details?  That sounds like a neat "portable power station".

 

[bigskybob]

I've got regular racks on my van that attach to the roof gutter.My panels are mounted on the racks.They are not enclosed and I haven't lost a panel yet.I have a 30 ft supply line from the panels to my controller so I can park the van in the sun and the trailer in the shade.

 

[Gr8ful]

It's a flat trailer 4" sides all aim. weighs 450# hauls 2000# with the wheels under so The whole deck is flat, the 6" PVC will be a U across the front & down each side painted black. I've had 6x6 army rtucks & have all the bows & a new tarp to cover the trailer when hauling & easy to remove when camped & will keep everything dry. I can pressurize the water system with a small comressor using a quick disconect on the ambo end. So to the ambo I'll rum 1 12ga ext cord & one Q/C water line. This way I don't have to put the panels down if I want to drive & explore. when pulling the trailer I have 250 amp alrenator to charge everything thu the trailer plug.

 

[maki2]

Do you have a baffle system inside of your water tubes? From what I have read about the engineering of water tubes placed on a roof that is a critical component of the design.

 

[VanTalk00]

I have thought of that.  My plan is to cut the painted CPVC into sections separated by plastic disks that have holes in the top and the bottom of the round disks and are inserted into the couplings.  That way, I can reduce the slosh to a 1 1/2 or 2 foot section.  I calculate the total volume for the  5" pipe with an inner diameter of 5.04" to be 15.4 gallons, weighing 123 lbs, distributed over the roof.

 

[maki2]

I do like each component of your system on its own merits but the combination of them all into one unit needs at least some redesign to allow for better airflow to remove heat accumulation from underneath the solar panel area. The lower substrate which the cells are attached to can be damaged by heat accumulation under the panels. That is a known cause of solar panel failure.

Your design restricts the air flow from the front, your design restricts the airflow from the sides. In addition you have two large heat accumulating storage units on each side which will increase rather than decrease heat accumulation under the panels. You are calling it a hot box and it truly is going to be that. Sure while you are in motion there will be some air flow movement but not much at all when you are parked and the panel is not elevated to tilt. But one of your goals is to be stealthy sometimes when parked and that means the panel staying down flat.

If the primary goal is to have stealth looking solar panels that is achievable by making the edges of the panels and the mounting brackets the same color and gloss as the van. A lot of vans have roof racks of various types, it won't draw a lot of attention if you keep it looking plain vanilla with nothing fancy to draw the eye up there. So if stealth is the goal along with solar power then that is easily accomplished with no additional shroud surrounding the panels.

Of course there are quite a few options for heating water which you will have already seen. Tubes are a fun concept for heating water, But at least in my mind the need for solar electricity takes precedence over water heated in tubes if the tubes could contribute to the failure of a solar panel with their adjacent location.

 

[VanTalk00]

Your design restricts the air flow from the front, your design restricts the airflow from the sides. In addition you have two large heat accumulating storage units on each side which will increase rather than decrease heat accumulation under the panels. You are calling it a hot box and it truly is going to be that.  

So here are some thoughts ...  First, the tubes will be surrounded on three sides with foam board insulation.  

More importantly, in the attached drawing, I've added some mesh screen, in red.  One is nearly horizontal on the front spoiler, and the other is vertical at the back of the panel between it and the fan.  I could see having that whole area around the fan as consisting of mesh screen and just not keep anything of value there.  Seems there would be a lot of air circulation possible then, without abandoning the hot water tubes.

I'll have a new design in a few days.  I need to confirm measurements and also think about available aluminum stock.  The difficulty is that my "reasonably-priced" supplier tends to carry the heavier, less common stock, such at 2" x 1/4" flats and L's in 20 foot lengths - way more than what I need or can justify buying.  I think I can get away with 1" x 1/8" L's in a frame that allows attaching a wrap.

 

[B and C]

I have flexible panels flat mounted on the roof with 1/4" spacers evenly spaced out underneath with industrial strength velcro holding the entire perimeter down. I haven't noticed that part of the roof to be any hotter than the rest of the roof. It has been working for at least 3 years now.

 

[grummy]

What has been people's experience with roof racks - especially enclosed ones?  What are the biggest pitfalls to watch out for?

The link below is one similar to your drawings that I put on my old Step Van. The only difference I would suggest as others have already is you need some air flow underneath. I left mine up off of the roof itself a little as well as some gap around the panels.

I like what your trying to do. Smooth, clean, more hidden and compact... we think alike !

 

[MrNoodly]

My only rack horror story is that I got one with aluminum uprights which kept cracking. I replaced it with a good old steel one.

 

[MrNoodly]

First, the tubes will be surrounded on three sides with foam board insulation.

You're going to want as much surface area exposed to the sun as possible since plastic is a poor conductor of radiant heat. That's assuming you want to warm the water, not just carry it high so it's an easy gravity feed.

 

[ckelly78z]

I have the same thought process on heating water, but as a DIY pool heater for my upground pool at home. I coiled 100' of 1" black plastic water pipe into a flat coil, and laid it out into a 4'x4' square with a 1"x4" wood frame on black painted plywood, that is then covered with plexiglass to essentially make a hot box. I have 2 of these coils on top of my steel CONEX shipping container that I keep my horse hay in. On a sunny day, these coils will heat water up 15-20* over the starting temperature in about 5 minutes of slow circulation back into the pool. I think each coil will hold 5-6 gallons and could be used as a shower source if capped.

 

[VanTalk00]

The link below is one similar to your drawings that I put on my old Step Van. The only difference I would suggest as others have already is you need some air flow underneath. I left mine up off of the roof itself a little as well as some gap around the panels.

I like what your trying to do. Smooth, clean, more hidden and compact... we think alike !

I will definitely think more about some enhanced air flow, but without catching the wind when I drive lifting the whole assembly off the roof.

 

[VanTalk00]

You're going to want as much surface area exposed to the sun as possible since plastic is a poor conductor of radiant heat. That's assuming you want to warm the water, not just carry it high so it's an easy gravity feed.

Hmmm ... maybe leave off the foam board on the side facing the metal wrap-around and let the wrap-around heat radiate into the pipe.

 

[Gr8ful]

You're going to want as much surface area exposed to the sun as possible since plastic is a poor conductor of radiant heat. That's assuming you want to warm the water, not just carry it high so it's an easy gravity feed.

Must have never tried a black solar shower bag.