Lag bolts to fasten Uni-Strut to RV roof

[littleharbor2]

The leading panel will be set back about 4 feet from the leading edge. And, I'm going to use these sorts of plastic mounting brackets for the leading panel:

https://tinyurl.com/5h3zycv6

If you can fabricate an air dam on the front edge of the front panel to divert the oncoming air over the panel you alleviate the lift which is so dangerous.

 

[MrThisIsME]

If going into the aluminum frame some self threading screws should be fine. By all means double up a bit on the leading edge.

While self-tappers are just fine even more so if into steel, I tend to like small lags better as they have deeper threads for more bite. Pre-drill required for both. To each their own though.

 

[HRTKD]

If you can fabricate an air dam on the front edge of the front panel to divert the oncoming air over the panel you alleviate the lift which is so dangerous.

It has been suggested here on the forum that the panels have no curve and are therefore not likely to have any lift. I'm no aeronautical engineer so I can't say one way or another.

 

[time2roll]

While self-tappers are just fine even more so if into steel, I tend to like small lags better as they have deeper threads for more bite. Pre-drill required for both. To each their own though.

I used stainless #10 drywall screws into the wood frame. Does not really apply to the OP.

 

[littleharbor2]

It has been suggested here on the forum that the panels have no curve and are therefore not likely to have any lift. I'm no aeronautical engineer so I can't say one way or another.

The air dam would keep the high speed air from getting under the panels causing substantial lift. I doubt you need to be an aeronautical engineer to figure this out.

 

[MrThisIsME]

The air dam would keep the high speed air from getting under the panels causing substantial lift.

High speed air under a panel does not create lift. If it did then plane wings would be shaped as rectangles.
Argument could be made that turbulent air could cause lift, but that is moot point.

 

[littleharbor2]

High speed air under a panel does not create lift. If it did then plane wings would be shaped as rectangles.
Argument could be made that turbulent air could cause lift, but that is moot point.

If you say so.

 

[inspectorrgadget]

High speed air under a panel does not create lift. If it did then plane wings would be shaped as rectangles.
Argument could be made that turbulent air could cause lift, but that is moot point.

Bi-planes, Boeing 707's, and F-35's all have one thing in common, which is they can all be flown upside-down.

I'm inclined to thing it's the "kite effect" which enabled Tom Cruise/Maverick to fly his F-14 inverted next to a F-5 standing in for a MIG. The same kite effect can cause a solar panel to fly off an RV roof.

For our purposes, keeping the panels level in the airflow is best. obviously. Based on experience with different fairings on my motorbikes, I don't believe fairing which ramps the airflow over the solar panels would hurt anything. Especially if there was a NACA-style vent at the bottom of the solar array fairing.

 

[MrThisIsME]

Funny you mention 707. My father, as a young lad, was there to witness such. How many times do you think I have heard that story?

A fairing might help, but I am far from being well versed at such. I just try to keep the level.

Only thing that would concern me would be the vacuum and or turbulence the fairing would create, but that is just me.

One thing to look at (it made me think), Is the vent above the refrigerator on the roof (I think they are all almost the same). It is a little piece of flimsy plastic with two screws going into more flimsy plastic, sort of shaped like a long seashell. If that thing can manage on an RV roof............

 

[HRTKD]

One thing to look at (it made me think), Is the vent above the refrigerator on the roof (I think they are all almost the same). It is a little piece of flimsy plastic with two screws going into more flimsy plastic, sort of shaped like a long seashell. If that thing can manage on an RV roof............

My vent has four screws. The only reason I know that is because I routed my PV cables through the vent down into the trailer.

 

[MrThisIsME]

My vent has four screws. The only reason I know that is because I routed my PV cables through the vent down into the trailer.

My bad, you are right all have 4 screws. Still flimsy - yet still hold well. With the shape it is you would think that it would be the first piece to go flying off the roof.

 

[inspectorrgadget]

Funny you mention 707. My father, as a young lad, was there to witness such. How many times do you think I have heard that story?

A fairing might help, but I am far from being well versed at such. I just try to keep the level.

Only thing that would concern me would be the vacuum and or turbulence the fairing would create, but that is just me.

One thing to look at (it made me think), Is the vent above the refrigerator on the roof (I think they are all almost the same). It is a little piece of flimsy plastic with two screws going into more flimsy plastic, sort of shaped like a long seashell. If that thing can manage on an RV roof............

 

[MrThisIsME]

Seen it a number of times
Funny thing is how technology works these days and how blessed we are with information. I sent my father that video, 6 years or so ago, so 60 years after it took place. He never knew the background as much as the video provided. Of course he called me up shortly after and asked "Did I ever tell you I was there?". LOL
There is one version were the top comment is "You let a guy named Tex fly your airplane, what did you expect."

 

[RoadTurtle]

High speed air under a panel does not create lift. If it did then plane wings would be shaped as rectangles.
Argument could be made that turbulent air could cause lift, but that is moot point.

Panel angle will have a huge impact on "lift". Air get under the panel and it can very easily create upward force. Front of my 5th wheel is angled down at the front, which in theory should create a downward force. Mfg on my 5th wheel used brackets with only one screw per bracket.

For my installation, I'm using brackets with two attachment points along with dicor, which admittedly has very limited retention, but it does add to the overall strength.

The concerns of "flying" off the roof is an issue, but it's also why I don't want to lift the panels to overcome my issue with shadowing.

 

[Geokilroy]

Thinking about this some more, the strut should be directly on the roof. I would create/weld a custom bracket that provides the necessary elevation off of the roof. Even then, it's a bit sketchy. My brackets would be fabricated out of solid aluminum.

I have a section of my roof that I would really like to use for a solar panel. But the refrigerator vent (10"x18", maybe) is in the way. I think I could remove the top part of the vent and with the solar panel taking its place rain won't get down there. But rain that is coming in horizontal because I'm driving 70 MPH in the rain? My point is that I'm not inclined to sacrifice functionality just to get more panels on the roof.

The refrigerator vent is to vent the heat from the refrigerator. Covering this vent keeps this heat under your panel. Mine puts out a lot of heat. No problem running cables down it, but covering it up no way.

 

[HRTKD]

The refrigerator vent is to vent the heat from the refrigerator. Covering this vent keeps this heat under your panel. Mine puts out a lot of heat. No problem running cables down it, but covering it up no way.

It's not ideal to heat the underside of the solar panel, however there would be a good amount of clearance for air movement. Plus, the plan is to ditch the absorption fridge and replace it with a DC compressor fridge, which will have no requirement for a vent.