Quote:
Originally Posted by 4536
For Aerohead, and anyone else interested.
Most vehicles have fairly short circumference curves in their transition from their sides to their top. So I suspect that little thought needs to be devoted to their taper characteristics from front to rear. However what about a vehicle with a large circumference curve?
Of course one of the advantages of the large circumference curves is its lower suseptibility to direct crosswinds which is always a concern with a trailer or high profile vehicle. Also it will presumably be more aerodynamic with any off center winds that are encountered.
Based on the Streamlined template, the following is the case for the trailer I am constructing. (see 6-14-10 "AeroTrailer from Scrap Materials" thread):
1. Each of the 24" vertical sides of my areodynamic trailer has a faster taper than the top because the D for the sides is 74" and the D for the top is 136". (53" high from floor to top at its highest point plus 15" from top of floor to pavement X 2 = 136").
2. There is a 29" radius curve that transitions upward and inward between the upper vertical sides and the top. The right and left curves account for 58" of the 74" width of upper part of the trailer at its widest point. Therefore only 16" in the center at the very top is flat (horizaontal). The trailer will be Kamm backed at about 79" rear of the widest, tallest point.
Therefore, what should the lateral (hoizontal) taper of the mid point in the circumfrance of the curve be, as it transitions to the rear?
What should the verticle taper be for that midpoint in the curve?
I ask this as that midpoint occurs at a shorter width than the sides and a lower height than the top.
Is it as simple as transitioning that mid point vertically with the roof and laterally with the sides?
Or is there some more complex equation that involves a chord perpendicular to the mid point of that curve and runs downward to the ground and is then doubled to determine D. Wouldn't this most likely provide a corner that bulged outward as it transitioned rearward due to a slower taper than the sides and top?
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4536,I apologize,as I'l late to the party.
The other members have made some good comments and I'll throw some thoughts your way also.
It's important for you to think of the trailer as an organic extension of the towing vehicle.
The roof curvature and body camber of the tow vehicle are going to establish the quality of the 'onset flow',as Hucho calls it.Also,the roof-to-sides architecture of the tow vehicle will set the pattern for the body of the trailer.
After seeing triple-trailer rigs lying on their sides along US-80 at Bonneville,I understand your concern for crossswinds,although having recently doing limited tests with my latest trailer,it may not be such an issue as you think.
With respect to the taper on the roof and sides of the trailer,it will be established by the roofline and sides of the tow car,and should not be any more aggressive than what the template would allow,looking at the car/trailer as a single form.
The V-nose is actually 'inferior' aerodynamically than say a 'NoseCone '-style radiused leading edge.
The blunt face with radiused side and top is better.
The gap between car and trailer is bad,it can add up to 20 % drag.If you can figure a way to close that up it would be good.
Morphing from the back of the tow car into the body of the trailer would limit the radius in the trailer top/side,even if you had the transition panels as I'm developing for my trailer and if you're not careful,you can aggravate the velocity potential at these two areas,causing the air to spin up into attached-vortices,like an ill-designed fast-back car.
If you could post a side view and overhead photo of the car/trailer combo it would be a big help.Then we could work with your dimensions a little better.
Fun project!