Quote:
Originally Posted by gezundheit
is there any formula based on the vehicle length? i have a 1978 25ft.pace arrow
and remembered that your rv is that size also.so,how did you arrive at your
fishtails length? what confused me was reading about that european trucking
groups 53ft.trailer and their fishtail.they sized theirs at 2 meters or 6ft.and said
it was the correct size for getting the lowest drag.now i'm thinking,if they are
correct,does that apply to any sized vehicle? anyway,i know you have been
asked this question before but i figured to ask again since you are the man.
regards,brian.
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There are mathematical formulas for just about every aspect of aerodynamic design, including the optimal length for a boat tail, but if you're going to build something that is actually going to be driven on the road, the length has to be confined to what is practical and/or legal.
In the USA, trucking regulations limit the length of a boat tail on a 53 foot trailer to 18 inches, I believe, which is not even close to optimal. My vehicle is the same original length as yours so I based the length of the boat tail partly by applying the proportions of the Dryden van study, and partly by the limitations in departure angle and strikes incurred when you start driving a 25 foot RV off road.
As far as being the man, aerohead and possibly several other of the aero geniuses that frequent this site would possibly qualify for that title, I'm just a guy with a mig welder and the cajones' to use it. ha.