Speed & Aero or why drag a boattail around at 45mph?

[Grant-53]

Measurements are what we use to confirm or refute perceptions. The FE curve from Chilton's old mileage improvement book showed peak mpg for a 70's Camaro at 20-30 mph. With my bicycle front fairing I get measurable improvement at 10 mph.

[Tesla]

So your improvement with bicycle fairing then provides you with a basis for a hypothesis that you can test a similar improvement on your car.
The ongoing bicycle analogies do not provide any evidence for improved aero at those speeds on a motor vehicle, they merely suggest a corrolation which forms the basis of a hypothesis that needs to be tested on said vehicle.

I formed a hypothesis on the basis of information gathered, much from this site, that the addition of wheel covers, air dam and a few other mods I should see close to 10% improvement in my FE, well it didn't show zip.

Does this mean that aero is a waste of time, no I don't think so, but what it does suggest to me is that it is a lot more complex and just because it improves FE in one persons situation doesn't mean it will do the same for everyone else.
I don't have all the equipment at my disposal to determine how these mods are modifying flow around my vehicle I can only propose ideas to the best of my knowledge and then test them with the rough cut tools at my disposal.
In some cases it may merely be that my testing is not sensitive enough in others it may well be that an improvement in one area may be negated by altered flow elswhere.

As said earlier, I'm not fully convinced that it's as simple as CdA when one gets into the lower speed ranges, but I'm still actively searching and reading to try to understand better what is really going on.

In all this, I always have Aerohead in the back of my mind saying fix the rear then look at the rest, wish I could but a boattail or even Kammback is not really feasable ATM for my vehicle.

[orange4boy]

Start with mechanical mods if you think they will make a bigger difference.

The torque converter lockup was my biggest improvement followed by the alternator delete. Is yours auto or stick?

Aero will help at your speeds but you need to log you MPG to tell what works best on your particular vehicle. Every vehicle design responds differently.

I went 19 to 33mpg and I felt like you when I started.

Never underestimate the power of incremental ecomods!

Cheers!

[NeilBlanchard]

HALF the load on the drivetrain comes from aero drag at just 28-30MPH. Ignore aero drag and you will be stuck with incremental gains. Improve aero drag and make substantial gains; and if you want to add the incremental stuff too, then great!

[Xist]

Originally Posted by Tesla

I formed a hypothesis on the basis of information gathered, much from this site, that the addition of wheel covers, air dam and a few other mods I should see close to 10% improvement in my FE, well it didn't show zip.

YMMV

Regarding the rest:

"Big words make my head hurt"
--Colonel Cameron Mitchel, "Stargate: SG-1"

[aerohead]

Originally Posted by Tesla

So your improvement with bicycle fairing then provides you with a basis for a hypothesis that you can test a similar improvement on your car.
The ongoing bicycle analogies do not provide any evidence for improved aero at those speeds on a motor vehicle, they merely suggest a corrolation which forms the basis of a hypothesis that needs to be tested on said vehicle.

I formed a hypothesis on the basis of information gathered, much from this site, that the addition of wheel covers, air dam and a few other mods I should see close to 10% improvement in my FE, well it didn't show zip.

Does this mean that aero is a waste of time, no I don't think so, but what it does suggest to me is that it is a lot more complex and just because it improves FE in one persons situation doesn't mean it will do the same for everyone else.
I don't have all the equipment at my disposal to determine how these mods are modifying flow around my vehicle I can only propose ideas to the best of my knowledge and then test them with the rough cut tools at my disposal.
In some cases it may merely be that my testing is not sensitive enough in others it may well be that an improvement in one area may be negated by altered flow elswhere.

As said earlier, I'm not fully convinced that it's as simple as CdA when one gets into the lower speed ranges, but I'm still actively searching and reading to try to understand better what is really going on.

In all this, I always have Aerohead in the back of my mind saying fix the rear then look at the rest, wish I could but a boattail or even Kammback is not really feasable ATM for my vehicle.

On GOOGLE,at 'Development of aerodynamics for a solar race car', by Ozawa et al.,HONDA Research & Development Co.,Ltd.,they offer a Road Load power curve for both their solar racer and a 'conventional' car (read Honda Accord).
I enlarged the table to 11" X 17".At any velocity you can just pick off the aero or rolling resistance road load component.
It's an easy way to see what aero is doing at the lower velocities.And it's prima facie evidence.No Unicorn-Corral stuff.Worth a look.

[Flakbadger]

Originally Posted by aerohead

On GOOGLE,at 'Development of aerodynamics for a solar race car', by Ozawa et al.,HONDA Research & Development Co.,Ltd.,they offer a Road Load power curve for both their solar racer and a 'conventional' car (read Honda Accord).
I enlarged the table to 11" X 17".At any velocity you can just pick off the aero or rolling resistance road load component.
It's an easy way to see what aero is doing at the lower velocities.And it's prima facie evidence.No Unicorn-Corral stuff.Worth a look.

The link: Development of aerodynamics for a solar race car

[kach22i]

Bicycles were mentioned in this thread, thought this chart might be appreciated here.

Squoval 3 - Cervélo

Relative aerodynamic drag. Aerodynamic drag is on the vertical axis, in multiples of a true aero shape. Each shape has the same frontal area, so the chart compares the drag due to shape only. - See more at: Squoval 3 - Cervélo

[orange4boy]

Too bad they didn't test that tube profile the other (better) way around.

[kach22i]

Originally Posted by orange4boy

Too bad they didn't test that tube profile the other (better) way around.

It probably wouldn't sell, too much ignorance of aerodynamics out there.

If the customers were educated about aerodynamics, they would have to get past the sales people providing misinformation.

If the sales people were educated about aerodynamics, they would have a hard sell with the customers.

The lowest common denominator seems to rule most things in life, which is why we celebrate those who manage to pop their heads above it, if even for a short while.