Just starting on wheel skirts, need opinions/ideas

[brucepick]

Originally Posted by FoMoCo_RANGER

is removing the tailgate more of a problem, then a help?

Have a look at this page re. the tailgate question.
http://www.cartalk.com/content/colum...ctober/05.html

I saw a writeup somewhere saying that whether up or down is better depends on the length of cab and/or bed - but I do like the coherent explanation in the link above.

I think a tonneau cover beats an uncovered bed, regardless of whether the gate is up or down. And an aero pickup bed cover such as you'll find discussed somewhere in this forum should beat a tonneau cover, if its well designed.

[FoMoCo_RANGER]

Originally Posted by brucepick

Have a look at this page re. the tailgate question.
http://www.cartalk.com/content/colum...ctober/05.html

I saw a writeup somewhere saying that whether up or down is better depends on the length of cab and/or bed - but I do like the coherent explanation in the link above.

I think a tonneau cover beats an uncovered bed, regardless of whether the gate is up or down. And an aero pickup bed cover such as you'll find discussed somewhere in this forum should beat a tonneau cover, if its well designed.

my factory tonneau weights in at about 200 pounds, i just took that off hoping to gain more MPG... i'm gonna do some expermenting myself to see some actual results, i saw the mythbusters episode, and still not sold on the idea, it was 2 different drivers

[MetroMPG]

There are a couple of threads here that deal with the question more scientifically than MythBusters did, and the results almost always suggest tailgate up is better than down or off.

[Chris D.]

Originally Posted by MetroMPG

Except you're not going to get any useful data because you've changed too many things.

Tank to tank testing is dodgy at best. But you've thrown a spanner in the works by also removing the tail gate. (Also - why would you remove the tailgate?)

You should only change one variable at a time.

true, which is why I'm going to put it back on, only driving I did was a test drive to mcdonnalds and back because I was too tires to bust out the WOK and make something good

Originally Posted by FoMoCo_RANGER

my factory tonneau weights in at about 200 pounds, i just took that off hoping to gain more MPG... i'm gonna do some expermenting myself to see some actual results, i saw the mythbusters episode, and still not sold on the idea, it was 2 different drivers

Sup Rob!!!!

I know for a fact that on a "unibody" truck Dodge Rampage (Ramlet) that the tailgate down or missing made a positive result in aero because my top speed went up 4mph.. It wasn't a conventional truck by any means..

it was a 1980's Dodge Charger with an El Camino truck bed..

Ditching that tonneau of yours will drop alot of weight. Isn't your tonneau ribbed in surface design? (Ribbed for her pleasure?)
I'd wait for it to stop snowing alltogether before dropping weight over the drives tho..

If I can find a sheet of coroplast in a 5 x 7 sheet, I'll make a bed cover.
Or, for 8 bucks I saw a 1/8" thick piece of plywood that I'd need two off to make a bed cover.. I'd reinforce it with aluminum square stock and rubber foam for the bed to tonneau mating surface..

I can tell you guys this..
My usuall section where I'd throw my truck into coasting mode before a stop sign with nobody behind me usually got me down to 35mph by a certain section.. last night I was coasting down in that same area and I was at 40mph in that same section.. this is all from 45mph exactly..

maybe theres something to this?

[FoMoCo_RANGER]

actually the snow has stopped here, its back to good old oregon rain... i'm gonna run a few little experements with running tail gate up, down, and gone to see what i come up with

[Chris D.]

I honestly think the tailgate up or down thing varies.. Not all trucks are designed the same.. So one general rul for a bunch of different variations of truck are too vague and should be taken on a truck by truck basis..

I just put my gate back on and up for the test voyage of these skirts..
reports tonite..

[cfg83]

Chris -

Originally Posted by Chris D.

...

I can tell you guys this..
My usuall section where I'd throw my truck into coasting mode before a stop sign with nobody behind me usually got me down to 35mph by a certain section.. last night I was coasting down in that same area and I was at 40mph in that same section.. this is all from 45mph exactly..

maybe theres something to this?

Someone can describe a better test than me, but I would do this, with and without the skirts :

1 - Find a hill you can coast down in Neutral that has a 45 MPH speed limit, and won't put you over 50 MPH (so no one can get mad at you for speeding) max on the coast. Maybe this means starting at a lower point down the hill. The hill will need a nice long flat section of road at the bottom.

2 - Start from the same start point each time. Coast down to a rolling stop as many times as it takes to get a reliable average for distance, max MPH, and time. The idea is to show repeatability.

If the skirts work, all three of those variables should be greater than without the skirts.

I think the only problem is finding that hill.

CarloSW2

[LostCause]

I know the coast down test has been described before, but I found a reference that goes into detail into limiting error. I think the most valuable thing was that it described how to find the coefficient of rolling resistance, rather than just using an assumption based on weight and manufacturer's tire specs.

Good results on the wheel skirts, but lets get some testing to make sure they aren't just placebos.

- LostCause

[Chris D.]

Originally Posted by cfg83

Chris -



Someone can describe a better test than me, but I would do this, with and without the skirts :

1 - Find a hill you can coast down in Neutral that has a 45 MPH speed limit, and won't put you over 50 MPH (so no one can get mad at you for speeding) max on the coast. Maybe this means starting at a lower point down the hill. The hill will need a nice long flat section of road at the bottom.

2 - Start from the same start point each time. Coast down to a rolling stop as many times as it takes to get a reliable average for distance, max MPH, and time. The idea is to show repeatability.

If the skirts work, all three of those variables should be greater than without the skirts.

I think the only problem is finding that hill.

CarloSW2

I have no hills that I can do that with, is there another way?

Originally Posted by LostCause

I know the coast down test has been described before, but I found a reference that goes into detail into limiting error. I think the most valuable thing was that it described how to find the coefficient of rolling resistance, rather than just using an assumption based on weight and manufacturer's tire specs.

Good results on the wheel skirts, but lets get some testing to make sure they aren't just placebos.

- LostCause

As soon as someone tells me how to go about testing
for results, I'm definatly down to give it a shot

I was suprised people on my truck forum didn't lynch me for skirting it. LOL
I've actually got the large portion of members trying to beat me.. More MPG to them!

If I end up at over the 30.5mpg mark, there mite be something to these..

[cfg83]

Chris -

I can't find that hill either, .

If you had a ScanGauge, you could do what Peakster did for an Acetone test, a point-to-point test on the highway :

Fuel Economy Test #5: ACETONE REVEALED!!!

http://www.youtube.com/watch?v=van5VmJ1yno

In the meantime, here is a compromise version of the same kind of test I was describing :

1 - Find a long flat road you can drive at the 45 MPH or greater speed limit. I think you want to start with at least 45 MPH in order to focus on the effect of aerodynamic drag. The middle of no-where with at least two lanes in each direction is your best bet.

2 - Drive up to the speed limit and pop it in neutral at a specific point along the road. You can use a landmark and/or a pal on the side of the road to help.

3 - Coast down to a rolling stop as many times as it takes to get a reliable average for distance and time. Again, the idea is to show repeatability.

If the skirts work, both of those variables should be greater than without the skirts.

Having another pal in the car with a stopwatch, pad, and paper to help record the numbers would help too.

I don't like this version because it introduces human error at the point where you pop it into neutral. For that reason, I would predict that your "coast to stop" positions could be wildly different. The downhill approach lets good ol' gravity give it the exact same push every time.

CarloSW2