Shape of a wind deflector? Tightness of fit

Does it matter how tightly a wind deflector fits? Does the material (metal or plastic) have to touch the top of the cab? I see some deflectors that have a 2 inch gap to the top of the cab, and really wonder about their quietness and efficiency. Likewise, it would seem most quiet and efficient if the deflector extends to the top of the Gofast leading edge?

Goal is to reduce noise but also increase fuel economy, which honestly is pretty dismal now.

This is an important question because if tight fit doesn’t really matter I’ll just buy a stock “Frontrunner” wind fairing or similar. Otherwise I’ll build my own deflector of ABS plastic and bent aluminum brackets (stolen ideas from other posts on Gofast forum) and make it fit with no major air gaps.

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Good question! I have a Thule crossbar and Thule fairing on my Ram. When my rig is standing, I have a 1” gap between the fairing and the top of my truck. I, like you had concerns about that gap. What I discovered with my setup is that at 30mph my fairing flattens increasing the angle and eliminating any wind noise. This flexing/flattening has provided me with a more aerodynamic rig.
Assuming you are interested in improving your aerodynamics on paved roads and not worried about off-road. Another thing that has improved my gas mileage is keeping my RPM as close to 2000RPM when on pavement. Doing this will depend on the type of rig, gears and transmission you have on your rig. This is my opinion and I am sticking to it! lol
Cheers!

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Mine has a gap but it definately reduces wind noise and hopefully improves aerodynamics.

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Here’s what the Front Runner fairing looks like on mine:

When it’s touching the cab, the rubber edge squeaks like crazy because the bed flexes relative to the cab. I’m working on replacing the metal fairing piece with some ABS plastic cut to a taller dimension so it sits at a lower angle and functions less as a speed brake. I’ll put some felt along the edge so it doesn’t squeak anymore too. The Front Runner hardware is great though because it’s adjustable and has no issues with the front track.

If anyone is interested in the metal fairing piece let me know. I won’t have any use for it once I fab the new one. I’m keeping the hardware though.

@globemaster Good ideas, thanks. It seems the optimum angle for reducing drag is about 20 degrees, which would also (if not too many gaps or holes) roughly be the quietest, too*. I’ll check out ABS plastic and see if readily available - otherwise I’ll cut it out of plywood with a smooth surface in front; if 1/4" thick or so the plywood should bend as needed. Will paint black and put felt along bottom edge. The height will depend on the angle, with an attempt to set at about 20 degrees.

*https://www.researchgate.net/publication/287150866_Aerodynamic_drag_reduction_of_heavy_vehicles_using_append_devices_by_CFD_analysis#pf3

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Had great luck with the camper rack from Shop — MARTIN OFFROAD

Deflector does a great job sending wind over the camper and made the ride much quieter. I also added an Amazon bulb seal to reduce noise even further.



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I second the Martin OffRoad method. I no longer have wind noise. Before install anything over 35mph was annoying. I installed and originally had the angled piece set at the top, it moved the noise to the rack. Moved it down and noise eliminated.

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In my humble opinion the deflector/fairing should - if possible - be tight to the cab roof and close to the GFC. However this is based upon just one try at building a fairing so take it with a grain of salt. But I’d think that any deflector/fairing you put up there will help.`

I built this wind deflector/fairing using a half-cylinder piece of 3Form polycarbonate left over from a construction project, Yakima cross bar and connecting pieces from a Yakima kayak stacker. I used pipe insulation to make a quiet seal between the fairing and the cab roof. The fairing is also set as close to my GFC as possible while still allowing the top to pop up.

The tight fit seems to work as the ride is quiet and my gas mileage is pretty good (21-22 highway MPG trying to keep RPM around 2000. Stock gear ratios)






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I like the idea of the pipe insulation (cut in 1/2). I don’t have a kayak or bike rack to use so I’m ordering parts now to do like this:

  • @ 1/4 ABS plastic sheeting, which should be flexible - will cut in a “reverse smile shape”
  • 1/4 inch bendable aluminum for brackets to go to T nuts on front of GFC
  • bolts, which will be painted black (resist rust) afixed through ABS and into brackets
  • will cut fairing as wide as top of cab

Will likely make a cardboard model first, to get the dimensions right. Will post pictures unless the whole project ends up in the trash, ha ha.

Sounds like a good approach. The idea of attaching to the front of the GFC is an excellent idea.
I also made a cardboard model first to get the dimensions and shape of ‘reverse smile’ correct.

Good luck and please let us know how it comes out.