Writer seeking examples of tested DIY aero mods for book

[freebeard]

OP tries to slip one past us, but Youtube puts it on (at least my) front page:

https://www.youtube.com/watch?v=ukOu6myatCU

TLDR; front undertray gives 45% benefit on the underside.


edit:
Further down the page: Julian's grumpy video

2nd edit:
Make your own steel offcuts storage rack

I just use five-gallon buckets.

Car aero tricks and tips from the past

I had one of the examples, a 1961 Type II [panel van]. They came with a optional three piece bellypan between the axle lines:


(DDG, original page 404s)

But I believe these parts were used to stiffen the shell in the 23-window variants.

I would assert that the VW Beetle has a blown wake. 1500cfm, IIRC.

[freebeard]

Deceptive rules of thumb in car aerodynamics
Julian Edgar
26 views 1 hour ago

[JulianEdgar]

Originally Posted by freebeard

Make your own steel offcuts storage rack

I just use five-gallon buckets.

The rack does work so much better than 5 gallon buckets.

[JulianEdgar]

Originally Posted by freebeard

I would assert that the VW Beetle has a blown wake. 1500cfm, IIRC.

Yes, maybe. I must admit I was thinking of only low-drag cars.

[JulianEdgar]

Originally Posted by freebeard

Deceptive rules of thumb in car aerodynamics
Julian Edgar
26 views 1 hour ago

This'll get me banned! So many single-value rules of thumb talked about on this forum, and I believe none of them. If only car aero were so simple...

[freebeard]

I was always bothered by the 12° one, thinking it's an odd way to quantify a curve. Then Tesla unveiled the Cybertruck.

As for the buckets, anything longer than 3-4ft goes into the [flat] ceiling joists.

[JulianEdgar]

I've now been asked what experts I consulted with when writing the book.

Firstly, Dick Barnard was my tech consultant at every stage of the book. Dick started his career as an undergraduate aeronautical engineering apprentice at Handley Page Ltd, and later became Principal Lecturer and Postgraduate Research Tutor at the University of Hertfordshire. He is also a founder member of the UK Wind Engineering Society, and a Fellow of the Royal Aeronautical Society. He has been a consultant for numerous car companies, including Jaguar and Rolls-Royce Bentley. Richard is the author of Road Vehicle Aerodynamics and has written many technical papers. Dick is an excellent writer, and he was very effective in telling me "they don't need to know that!" when I headed down too technical an alley. He also told me some very funny stories about aero testing Bentleys with their chief road testing driver.

Joseph Katz (Professor of Aerospace Engineering at San Diego State University, and author of two books on car aerodynamics) read the more technical chapters - and he had plenty of comments to make! Joe was probably my harshest critic.

Adrian Gaylard (Jaguar Land Rover chief aerodynamicist) saw the whole book in draft form. Adrian pointed me towards some significant engineering papers that I’d missed, and wasn't at all backward in highlighting where I thought I was leading readers astray (like the original draft on the topic of vortex generators!).

Willem Toet (F1 aerodynamicist) read most of the chapters. We had lots of email debates about things like front/rear distributions of downforce - understandably, Willem came from a more 'performance' background.

The thing that struck me about all the experts was how down-to-earth they were. They all understood that I was writing for 'normal people' and so math had to be kept to a minimum. (Sometimes that was hard for Joe to pull back from, but he usually did.) They were also all very positive about my on-road testing techniques (some of which I developed while writing the book). By the same token, none were the sort of people to spoon-feed you - and you wasted their time at your peril!

But from my point of view, the biggest thing they gave me was great confidence in what I was writing. As completely self-taught in car aero, I needed the reassurance - that what I had come to believe through research and on-road testing, was actually also what these experts believed.

[freebeard]

Here's a question/case study for you. I'm holding a reservation number for an Arcimoto FUV (higher than their total production of 100+ (More than Tucker)). At some point I anticipate exercising it.



They have a stock fiberglass motorcycle-style fender and abysmal range at freeway speed. One thing needed is a full pantaloon/pontoon fender, but the inside wheel at full lock needs truncation.

Maybe a box cavity or details cribbed from rear view mirror designs?

Here's the most I've done on the full body. Proportions are right, except for a two foot boat tail, but the daylight openings aren't cut in. I'm actually backsliding with this newer software.



I envisage riveted aluminum construction, like Randy Grubb's DecoPods. Except only one cut edge for each hexagon, pulled into a shallow cone. And frenched-in 1959 Cadillac tail lights in wind-splits as vortex generators (?)

[JulianEdgar]

Well, if I was doing it, I’d make some different full-size bodies (eg out of wire frame and stretch cloth) and tow them behind another vehicle at a decent distance, measuring drawbar pull with a strain gauge.

Make body modifications; retest.

I think in the absence of testing you could speculate endlessly and be no further advanced at the end of the speculation than the beginning.

[freebeard]

Fair enough.

For full-scale testing at speed, an actual FUV would be optimal. So I guess it's back to waiting. Thanks.