Quote:
Originally Posted by jas67
Hi All,
I just purchased a small flat-front box trailer, 4w x 6L x4h.
It is about a foot taller than my tow vehicle, a 2015 TDi Golf Sportwagen.
I also tow a 6x12x6 V-nose aluminum box trailer with same TV. I use a wind deflector on top of the TV for this trailer, which is almost 8 feet tall overall.
Highway MPG for the TV alone is 44-48 at 70-80MPH
Highway MPG for the TV + 4x6x4 trailer is 30-31MPG, 70-75 MPH
Highway MPG for the TV + 6x12x6 trailer with wind deflector is 20-22 MPG, 70-80 MPH
Highway MPG for the TV + 6x12x6 trailer w/o deflector is 18-19 MPG, 70-80 MPH
I'd love to do a tail for each of the trailer, and a nose-cone for the small one, but, that will be another thread.
For now, I think low hanging fruit on the smaller trailer might be to lower it. It looks like I can likely lower it 2-3 inches by adding blocks to the axel, which is above the leaf spring, without compromising suspension travel.
Has anyone here done that? How much MPG savings can I expect from lowering it 2-3 inches?
TV height is 58 inches. It is a wagon that tapers a little to the rear.
Current roof height on the trailer is 70 inches.
I tried the wind deflector with the small trailer, it may have helped MPG by 0.5 to 1 (30.5-.31.0). I'm thinking that the wind deflector I have is too severe for the shorter trailer, and that maybe a smaller one, or one with less angle might be helpful. Thoughts on this?
I wish I had access to a wind tunnel!
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I don't think we could say with any certainty. There might be an advantage for the upper body airflow, while simultaneously experiencing a disadvantage in underbody flow.
From NASA, until the TV-Trailer are the same height and width, the gap is eliminated, and an aerodynamic singularity is created, only then might we be capable of applying rules to the aerodynamics.
Years ago, member freebeard shared a video of a VW Beetle '5th-wheel' RV Trailer setup which almost eliminated the gap, and an integrated trailer would be capable of completely drafting in the wake of the TV.
Matching roof height meant about a 16% drag reduction, and closing the gap meant another 16% on top of that.
'THEN' we could 'guestimate' what a trailer belly pan, wheel covers, wheel skirts, and a boat-tail would do. And 'nothing' allowed on the roof or sides of the trailer.