Testing aeroshell/boat tail For the Dodge

[skyking]

It hangs in the carport now.
Here is a shot of the trusses from the inside. 13' plus long, weighs in at 65 pounds total.

Here is the money shot.


I planned on starting at station 10 as shown. Looks like it is OK until about 40, then it starts to drop under just a bit. The bag in the plastic is showing about station 25.
I figure I will elevate it a couple of degrees next time. It is not difficult to do, because it is hinged off the headache rack.

[skyking]

We put on stringers for a diffuser, but it was a good thing I did not install it. The tail was far too low as built. It would have been dead flat just by my eyeball. I think I'll lift it up so the tail is 4" higher than shown in the picture above. This will put it somewhat above template for most of the profile and probably prudent considering the surface condition. The template is based on a completely smooth wind tunnel model, not a cardboard covered contraption. I think I can leave a little on the table in terms of optimal shape. Much better than trying to push things the other way.
The plastic is coming off for the next test. It will be a fair weather only test
By the time I got to the sides, I was just about out of personal gas Monday night. I cobbled it together aft of the side door area. I had a straight piece forming the back edge of the door when it should be a curve.
I can correct that when I lift it up, and make some nicer transition there. I can leave that framework in place, pull the staples and lift the cardboard, and fir it out to a curve much easier than re-framing. I will add a small pie slice of cardboard along the edge of the box to fill in when I lift it.

[KamperBob]

Sky, a few thoughts for cost effective testing. (1) Tufts to confirm attached flow; 20 mph minimum according to gurus. (2) Find a nearby hill to make some "soap box derby" runs in concert with ABA changes; if you have GPS that might help if the data isn't too dirty. (3) If your truck has ODB then a ScanGauge offers sensitivity over short road sections.

Rock on!

[skyking]

Bob, no fuel flow instrumentation possible without installing inline flow and return flow devices. $$$$$
I do plan on a tuft and coast down test for V2. I was thinking of you specifically as I drove home this morning. What is stopping you from visiting the great PNW?
Come on by, camp in the yard ( I have guests from Australia in our yard in their RV at the moment).

We'll put this thing back on and test again.

Fact is, next time cannot be considered an ABA test either.
Changes;
Bellypan will be on
Diffuser
rear wheel covers

The cardboard came from the sheet of marine ply that I bought for the wheel covers. I need to cut them out and figure up a mounting, coat with epoxy and poly.

Here is a link to my page on boondocker's welcome. The invite is out there.
skyking | Boondockers Welcome

[KamperBob]

Originally Posted by skyking

Bob, no fuel flow instrumentation possible without installing inline flow and return flow devices. $$$$$
I do plan on a tuft and coast down test for V2. I was thinking of you specifically as I drove home this morning.

I'm honored.

What is stopping you from visiting the great PNW?

Just time and distance. If I had too much cash I suppose acceleration wouldn't matter. As it stands both will resolve in due course.

Come on by, camp in the yard ( I have guests from Australia in our yard in their RV at the moment).

We'll put this thing back on and test again.

<SNIP>

Here is a link to my page on boondocker's welcome. The invite is out there.
skyking | Boondockers Welcome

Awesome website! How long has it been up?

Fact is, next time cannot be considered an ABA test either.
Changes;
Bellypan will be on
Diffuser
rear wheel covers

The cardboard came from the sheet of marine ply that I bought for the wheel covers. I need to cut them out and figure up a mounting, coat with epoxy and poly.

ABA still applies. A = baseline w/o cap (other mods moot). B = cap on. A = double check baseline and measurement noise.

Rock on!

[skyking]

Bob, the site is fairly new, I think less than 6 months or so. It seems to be taking off nicely.
I'd give it a try.

[Sven7]

It's about time someone did a 90% boat tail pickup!

Get those corners straightened out and you'll be in business- I think there are a few pockets of detached flow slowing you down- literally! Maybe make some transverse curves over the edges to get a smooth surface. Tuft that, refine, then 'glass it!

You're getting pretty close to this little number:

Aero-Dynamic by jeff868_2000, on Flickr

[ChazInMT]

Here's my 2¢ on what it should look like when modified. Solid "diffuser" area would be a major plus.

[aerohead]

I don't know if you have the clearance,but on my Dodge truck,the 'top' of the diffuser is the 'floor' of a spare tire alcove.The spare just slides in from the rear kinda like Honda's Ridgeline,but no lifting,just sliding.It's nice not to have to lay on the ground to retrieve the spare.

[aerohead]

Originally Posted by Sven7

It's about time someone did a 90% boat tail pickup!

Get those corners straightened out and you'll be in business- I think there are a few pockets of detached flow slowing you down- literally! Maybe make some transverse curves over the edges to get a smooth surface. Tuft that, refine, then 'glass it!

You're getting pretty close to this little number:

Aero-Dynamic by jeff868_2000, on Flickr

I'm going to do 100% at Bonneville 'n see what that's like.No trailer,just a boat tail.I'm guaranteed only 4-runs total so I won't get to 'experiment' too much.
At 100% I can simulate an inflatable tail as depicted in Hucho's book,from FKFS R&D.It was either Fachsenfeld's or Kamm's patent drawings.Don't know for shore.(I'm a 'Valley Boy' so I get to say 'for shore.')