Aero RV (custom boat tail for '95 Ford E-350 Class C motorhome)

[orbywan]

Originally Posted by kafer65

One thing, turbo is load sensing irrespective of rpm. If you make more aero improvement s or slow down to reduce aero load the boost will subside even if your at max rpm. Changing to as smaller gear may put you where you have an increased load on the engine and increased boost even when your rpm is reduced. Great job, buy the way. I have an old dodgeslant6 pickup with 3.55 gear and I only get 13mpg empty. I'm so ready to put an airdam and aero bed cover together now.

Yes I have that debate going on in my mind. I started to do that with my Saturn and after finding some torq/horsepower/rpm charts on it I decided I might be going backwards with lower gearing. I shaved the side mirrors, did a total block off of the front grille and covered the head light nacelles with plexiglass and I'm averaging a bit over 50 mpg straight and level with no A/C. I'm happy with that a far as the gearing. Next up is a complete set of wheel fairings and maybe belly pans.

[ennored]

NASA paper:

www(dot)nasa(dot)gov/centers/dryden/pdf/88628main_H-2283.pdf

(Sorry, I can't hotlink it as a new poster here.)

A brick with a .24 Cd, really cool. Love to see an RV built with the shape they developed.

[orbywan]

Originally Posted by ennored

NASA paper:

www(dot)nasa(dot)gov/centers/dryden/pdf/88628main_H-2283.pdf

(Sorry, I can't hotlink it as a new poster here.)

A brick with a .24 Cd, really cool. Love to see an RV built with the shape they developed.

Yeah, that's it. Thanks for posting it.

[orbywan]

Originally Posted by rickjames8

I guess it does come down to skill sets. For me, I'm more intimidated by welding a steel frame. Having never welded, it seems like a much more precise skill....

Work with what you're comfortable with or look it as an opportunity to learn something new. It's good either way.

[t vago]

Originally Posted by ennored

NASA paper:

www(dot)nasa(dot)gov/centers/dryden/pdf/88628main_H-2283.pdf

(Sorry, I can't hotlink it as a new poster here.)

A brick with a .24 Cd, really cool. Love to see an RV built with the shape they developed.

http://www.nasa.gov/centers/dryden/p...ain_H-2283.pdf

[rickjames8]

Originally Posted by orbywan

Work with what you're comfortable with or look it as an opportunity to learn something new. It's good either way.

You're absolutely right. I think I might see about getting a welder and seeing what I can do. I have a few friends locally who've welded before who could give me tips and I would trust them to check my work before roaring off down the road at 55mph.

I plan to buy this RV at the end of Feb with a planned departure at the beginning of June. I'm trying to list out all my mods now to work out how long it should all take. Not that I've ever had a plan stick to a timeframe before.... ;-)

[slowmover]

Originally Posted by rickjames8

You're absolutely right. I think I might see about getting a welder and seeing what I can do. I have a few friends locally who've welded before who could give me tips and I would trust them to check my work before roaring off down the road at 55mph.

I plan to buy this RV at the end of Feb with a planned departure at the beginning of June. I'm trying to list out all my mods now to work out how long it should all take. Not that I've ever had a plan stick to a timeframe before.... ;-)

Start a thread for it. Link it back here.

And thanks for waking this one. I always get pumped when it shows back up!!

.

[ennored]

I've posted in a couple threads about boattails, but not here, where I first was drawn to Ecomodder.

In the beginning of this thread you mention that you kind of just guessed a taper for your boattail. You say it's just over 4' long. Just how much does it taper in? Did you lay out the curved part, or simply eyeball it?

Thanks.

[orbywan]

Originally Posted by ennored

I've posted in a couple threads about boattails, but not here, where I first was drawn to Ecomodder.

In the beginning of this thread you mention that you kind of just guessed a taper for your boattail. You say it's just over 4' long. Just how much does it taper in? Did you lay out the curved part, or simply eyeball it?

Thanks.

There is 18 inches of taper occurring on the first 24 inches of the 4'6" of each rib. I made a 'control' rib of that specification and pounded out each of the 28 ribs to match the control. The taper occurs in the first 24 inches of the length of the rib, instead of the whole length like I probably should have done it.

I did it that way because I was flying along in a J-3 Cub once a long time ago and watched some water vapor moving over the top of the curved wing surface and down the extended aileron as we turned, without separating, and that shape stuck in my mind. So I made my ribs like the Piper wing.

In retrospect that was pretty dumb, but it did still have a great effect on mileage. Once the front mods and the wheel pants are finished I'll do some more testing and maybe make the tail conform to the holy template, or not, depends on how it does and how much time I can spend on it. I have had zero time for months and it's making me crazy.

[ennored]

"There is 18 inches of taper occurring on the first 24 inches of the 4'6" of each rib."

You mean the skin on any side is 18" from the front in only 24" along the skin? Or 18" total narrowing on both sides? And it's basically straight after that? And the ribs started 4 1/2' long? Of the finished tail is 4 1/2'?

What is the total taper? It starts at 96" wide (or close to that) and narrows to what? Maybe 48" (half) judging from the pictures?

Just trying to get in my head what it looks like vs. the Dryden (and other) tails for my graph in the other thread.

Thanks!