Solar "Hump" for aerodynamics for Class A RV

[Bobert]

very impressive install. pretty nice integration, I like the tent shape of the panels. You should share that somewhere in Show and Tell.

you could try posting a picture directly from the side like perfectly parallel to the RV. Some of the Simulation Wizards here could create a black and gray model and run it through the fluid dynamic flow simulation and try various tweaks.

I got a tent shape naturally by following the contour of the roof with my brackets. The tent shape dramatically increases the rigidity of the structure. It’s not obvious from my other pictures but I have a 14” cat walk on the driver’s side of the panels. This is convenient for sweeping off the slide outs and cleaning the panels. It’s also worth mentioning that this trailer is high off the ground and I put the tallest tires that I could on it so the frame is a full 2 feet off the ground. This might make a difference for wind resistance. One must also consider that since it is towed how the wind hits the trailer will be affected by the dynamics of the tow vehicle. I can’t get a straight on side view of the camper right now as we are parked in the trees and I can’t get a unobstructed view straight on.. from were the airfoil attaches to the front panels to the back of the trailer is 32.5 feet. There is a space where 2 panels are missing immediately after the first 2 panels because of the roof ac. My thought is to remove the roof ac and install a mini split and 2 more panels in that gap. While I am dreaming my ideal setup would be 12 of these https://a1solarstore.com/solaria-400w-solar-panel-mc-4-powerxt-400r-pm.html?msclkid=a7a6002f77611db1196562ace98e30f3&utm_source=bing&utm_medium=cpc&utm_campaign=First bing feed&utm_term=4586612758817463&utm_content=BingAdGroup that would cover the entire roof and give me 4800 watts up there.

 

[eXodus]

One must also consider that since it is towed how the wind hits the trailer will be affected by the dynamics of the tow vehicle

True,
When I was digging in this topic, I realized how bad pickups without a topper are for towing regular trailers - pretty good for 5th wheels.

I mean - my pickup has the same 5.7L Engine as my 24FT RV - and with the Aero tweak while towing a trailer - the pickup is only 1 mpg better then the RV.
To emphasize that - a 6000 lbs pickup with bad aero needs almost the same fuel as an 11000lbs RV with slightly optimized Aero, while towing.

I put the tallest tires that I could on it so the frame is a full 2 feet off the ground.

not sure why you would do that? Bad roads where you are? That would likely kill most other gains you can make on aero. The less air you got underneath the vehicle the better. I'm going to add a front Air dam to prevent high pressure air getting sucked under the RV.

 

[Bobert]

not sure why you would do that? Bad roads where you are? That would likely kill most other gains you can make on aero. The less air you got underneath the vehicle the better. I'm going to add a front Air dam to prevent high pressure air getting sucked under the RV.

I live in a very rural area of the north east US.
A 38’ travel trailer is constantly catching the rear of the frame if It’s not good and high off the ground. It also gives me a bit more flexibility in getting level at poor camp sites. Larger tires make it easier to get a better load rating. It also makes it much easier to work under the camper. I have done extensive work on the underside of the camper and still have some more to do yet so that is very handy as well.

 

[Weru12]

You could try adding a leading edge with Airtabs (or similar) aerodynamic vortex spoilers to break up the air flow so that you don't create low pressure areas.
Airtabs

 

[Bobert]

You could try adding a leading edge with Airtabs (or similar) aerodynamic vortex spoilers to break up the air flow so that you don't create low pressure areas.
Airtabs

Thanks for the link I had never heard of those before.

 

[eXodus]

1+ year later and thousands of miles - the Solar Hump is still on the roof.

I'm not sure if it did benefit fuel economy much. Certainly it didn't diminish it. The other good news - the RV feels more planted. I'm don't feel that we are getting blown around by gusts as much.

I read that others got reduced fuel economy when adding solar - so that don't have an impact on MPG and better driving experience - I see it as a win.

 

[justgary]

1+ year later and thousands of miles - the Solar Hump is still on the roof.

I'm not sure if it did benefit fuel economy much. Certainly it didn't diminish it. The other good news - the RV feels more planted. I'm don't feel that we are getting blown around by gusts as much.

I read that others got reduced fuel economy when adding solar - so that don't have an impact on MPG and better driving experience - I see it as a win.

That's great news!

After looking at your problem and playing with a few different box trailers, I have decided that: 1) you just can't hide frontal area; and 2) Most of the gain possible is likely gotten by shaping the rear of the vehicle to reduce turbulence.

 

[justinm001]

I put 1800w of solar on my class A Prevost and had to put it at a high slope to not hit AC units. I was worried having such a huge gap would create a ton of lift.

I drove over 500 miles with a couple pencils, screwdriver bits, nuts/bolts and even a 6' piece of aluminum all just chilling on the roof no issues. I'm certain the front being so close to flat causes the air to go so much above the roof it doesn't affect anything.

 

[Lt.Dan]

Worst part of putting panels above the AC is overall height of the rig now.

I thought about doing it to mine, but after measuring, the tip of the AC (on mine) is 13' 6", which is the legal limit for height here. Adding any more height would be over the legal limit, and im already worried about low hanging objects.

 

[Supervstech]

12’8”.com

 

[justinm001]

We have a low overpass in my town we call the canopener because it's 12'8" or so and claims a ton of trucks almost one a week.

I bought an XL2 which is about a foot shorter than the H3 model of many prevosts. There's a label that says 13'6" clearance but I think we're still just under 13' with the panels. Lowest bridge we went under was 13'8" and crawled through it.

Mines mounted using door hinges on my fake awning covers then uses threaded rods in the middle connected to aluminum bars. Takes just a couple minutes to unscrew the 2 sets of bars and lift it up half at a time, then use rope to hold it open.

I'm planning on adding another 1800w on the other side but I have real awnings so need to find another way to mount the end, then some wedge to angle the panels at the right angle. I'm still thinking about making them motorized to track the sun but they work pretty well so might not be needed.

Also still working on the ACs. I have 6 of them and only 2 are working fine, about to swap out 4 of them.

 

[eXodus]

Worst part of putting panels above the AC is overall height of the rig now.

I don't like the A/Cs are on the roof period. They are heavy bricks poking holes in the membrane.

Would love that when some RV manufacturer would make some effort to integrate a Ducted Inverter Mini Split A/C units. It's not that hard when you design a new Floorplan.

Would get rid of all things on the roof ,smooth out aero, lower center of gravity and enable more solar. Further bigger rigs - you can get on large Mini split with multiple heads - so you can do multi zones. But you don't need to have 2-4 A/C units.

 

[jberger]

We have a low overpass in my town we call the canopener because it's 12'8" or so and claims a ton of trucks almost one a week.

I bought an XL2 which is about a foot shorter than the H3 model of many prevosts. There's a label that says 13'6" clearance but I think we're still just under 13' with the panels. Lowest bridge we went under was 13'8" and crawled through it.

Mines mounted using door hinges on my fake awning covers then uses threaded rods in the middle connected to aluminum bars. Takes just a couple minutes to unscrew the 2 sets of bars and lift it up half at a time, then use rope to hold it open.

I'm planning on adding another 1800w on the other side but I have real awnings so need to find another way to mount the end, then some wedge to angle the panels at the right angle. I'm still thinking about making them motorized to track the sun but they work pretty well so might not be needed.

Also still working on the ACs. I have 6 of them and only 2 are working fine, about to swap out 4 of them.

Can you post some pics of this setup, very interested in being able to pivot the panels of up and out of the way when working on the roof.

 

[justinm001]

I don't seem to have any pics of it up but you can see the hinges on the side. I have 2 sets of 9 100w renogy panels screwed together then at the end have aluminum angle for reinforcement. And for the mount I have like 8 threaded rods drilled into my roof with fender washers and bolts on both sides and then another aluminum angle for reinforcement. The bolts are screwed through both aluminum angle pieces with bolts on both sides. Also have a few bolts securing them both together.

It's still a work in progress but we drive this coach all around and it's working great. I left quite a bit of thread on the rods so I can adjust as I'm replacing some AC's with taller ones so it'll be adjusted higher. Also might weld the angle together and will clean it up but want to add 2 additional solar panels to keep my starter and genny batteries always topped off.

When I remove I just unscrew the top of the rods and wiggle them apart and have string tied from the top of the panels to the awning mounts on the other side.