Quote:
Originally Posted by skyking
Thanks Phil, I was just looking at the template again when you posted. The back of trailer and is about 63% or so. Essentially I'm going from a high point of 7.5' and following the template for about 16'.
I'd have a clean break there with a bumper recessed in out of flow, and the ability to hang a 3' boat tail for longer trips if it would do any good.
I have weights in mind. The combined weight should be between 11,500 and 12,000 pounds.
I have played with the calculator quite a bit. I figure I can get an average of .008 on the crr, using the best tires for each unit. I just discovered I can use the Bridgestone 381 with the really low crr on the trailer.
Just guessing from my results so far, I figure the Cummins 6BT at .29 thermal. The truck sucks hard at 34.5 ft and .44 cd. I think smoothing things up off the truck and finishing them off onto template with faired wheels should net the mid.2s for the combined rig.
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I just now made some photo-enlargements from Hoerner's section on railroad vehicles.I haven't digested every word so far,but these materials may give us some insight into the trailer technology:
*Locomotives with Tenders are progressively streamlined starting at Cd 0.98
*a hemispherical nose and side fairings,and gap-fillers gets it to Cd 0.42
*raising the Tender roof up even with the Locomotive fetches Cd 0.37
*sloping the 137 sq ft Tender down to the 89 sq ft frontal area of the rail cars cuts drag to Cd 0.29 *************a 21.6% reduction in Cd based on the frontal area of the Locomotive.(10.8% better mpg @ 55 mph)
This suggests a historical precedent for your 5th-wheel technology as well as my Viking trailer.
It is saying that you can expect the drag reduction and offers a little quanta.
The Renault V.I.R.A.G.E.S. 10-wheel semi-trailer got to Cd 0.29 with the extended boat-tail.
53 sq ft,down to 17 sq ft is almost a 68% wake reduction.I'm not yet qualified to predict your mpg potential but I must believe that you'll be delighted.I think orbywan got 24% from his RV boat tail.I think you'll be harvesting massive low-hanging fruit.It's a tantalizing project!
