rear bumper delete and removable boat tail filler panel 2 ideas to merge
 

http://ecomodder.com/forum/member-gu...726-172424.jpg
Eg of tarped load.
http://ecomodder.com/forum/member-gu...irty-air-2.jpg


http://ecomodder.com/forum/member-gu...-7160gross.jpg
Ideal would have been to fill the gap from underneaththe tarp to tuch the tail finn instead of 4'from the rear. Some glad bags will help with thisin the future, as it was this was the maiden voyage for cap and this is what I got.

http://ecomodder.com/forum/member-gu...den-voyage.png

What angle on the gate(absolute angle to level)?

I may go as simple as a simple I.M.C.A. stile 2"×.125 tube . Bumper .Insted of a hand built role pan, to cover the hitch.
http://pitstopusa.com/images/F15901632

Airfoil could be flat. Purpose for airfoil is to streamline the 4.5"sq ×1/4" hitch cross tube. It would be nice if the tail of the Airfoil was positioned to be a step when the gate is closed/open like the current step bumper

Easy to clean snow bugers is a design requirement , they can over load a 1ton truck from a bad design.

As a guy with a pickup truck which backed into a pole because my passenger was distracting me by throwing his arms around wildly and yelling/laughing like a maniac (I have some "fringe" friends), and as a guy which was just sitting there at a stop light when the idiot behind me thought the light had changed and crushed my rear bumper a second time - keep the rear bumper intact.

Do you have a belly pan or something which would begin to warrant removing the rear bumper?

I can see cutting slits or drilling holes in the rear bumper to relieve air pressure, but doubt you have anything resembling clean air flow under the truck.

Agreed safty first the ,not in drawing ,should have about the same crash strength as the stock + more crush zone distance
If i get hit or I back into something hard enough to get through the I.M.C.A. Modified bumper , then the stock bumper would have done body damage by folding into the body as the side sections are just chromed sheet metal ~ .090" thick maby as low as .065" with a center section (frame wide)of .250" flat plate for the bumper mount hitch ball.

Ill fix the broken link to the pic of I.MC.A Modified rear bumper.

I have often thought a foot of six- or eight-inch-thick foam board would make a great back bumper.

Or a boat tail! :D

I would feel safer with a better bumper up front, too, it would just do little aerodynamic good. It seems like I keep seeing cars that do not have bumpers, just a big rounded front.

filler panel/wing
 

unless the panel goes all the way down to the bottom of the belly there will be a pressure discontinuity 'kink' as Hucho calls it,which will compromise the drag reduction.
The wing may be in a stalled area of turbulence and not be able to divert any flow.A nearly-full belly pan might be required to clean up the flow enough for a wing to work down there.
http://i1271.photobucket.com/albums/...titled6_27.jpg
Pickups have some of the highest drag underbodies
http://i1271.photobucket.com/albums/...titled29_4.jpg
If it did,Hucho says that it will cause more harm than good,due to the drag of the wing itself.He tested a lot of aero accessories while at the VW wind tunnel and never saw any sort of flow diverter improve drag.

If im understanding correctly the 5 sided box that sticks out 3"per side and a brick shaped hitch cross member is the best cleanup I can expect.
Ive heard sence I was a kid that a rollpan bumper with a hidden hitch was about the best aerodynamic package you can do to a pickup. Nowdays its airdams , side skirts, aero caps,and belly pans and many more on top of the tryed and true Rollpan . Iam merely trying to tie it all together and figure out a long term plan.

I have a tendency to dream big. Some times to big.
So for this level of mod some extra steps are needed.
1 full belly pan
2 side skirts
I alluded to side skirts by asking for advice on width "hitch wide or out to side skirts as rear mount" under "Request for Advice #4"in drawing picture.
3 ??? What else keep them coming this is another high-school idea like the cap its purpose and design have adjusted to changing life ... I cannot see all the shortcomings but I can adjust to the ones that are visible to me or others. Eg I saw that the supper aggressive Airfoil could be to much and said it could be flat if nothing mote than a pice of sheet metal pop rivited as a tail cone...
Corection the hitch is 38"w 2.75×2.75 sq. It hangs 13"lower than the lowest sheet metal and 17below the bottom of the bed over a foot off the ground.

----
---- how about part 2 idea #1
Boat tail patch panel to allow the tailgate to be set at ??°as a rear diffuser . The gate idea would work better minus the the giant hallow ,parachute 5 sided air scoop they called a bumper in the 90's and a rearbelly pan from the rear end. I have a 4 ×8 sheet of plexiglass from an old sign to work with just trying to think of a best use of it but mixing a 4th consept in I felt was too long a title blending 2-3 into one build is complex enough .
I like the suggestions so far it just increased the #of concepts
The center belly pan should be simple slap a flat panel to the bottom of the running bords with dutz aircraft fasteners into the cross stringers . add the missing section between the cab and rear wheels wala a belly to the rearend. Corce have to accommodate the drive shaft . This is what we had to do to our street stock with a custom floor pan also make room fore 2 6"×36" glasspacks. All with in the scope of my toolbox of understanding and skills my shapes are dreived by eye not computer programs so my thinking is a little different but we can communicate (as long as you can figure out the Cypher)sorry bad spelling and composition but I do try.
Gumby Stay Flexible

I'm going to try my had at being an unimaginative pragmatist here, so bear with me.

Take that long list of yours and toss it out, nothing is going to be as effective as lowering the "A" in the CdA formula.

As with any type of pickup truck cover, you have already compromised the utility of the vehicle, frequent large heavy loads are not a daily routine to say the least, right?

Lowering the truck depletes it of most it's cargo holding capacity, but it is the simplest route in my opinion.

Below is a truck I've seen recently, I forgot to ask him about his MPG, we talked mostly about Eastwood rust preventive products having a marginal effect.

2016 Misc by George Kachadoorian | Photobucket
http://i184.photobucket.com/albums/x...psmoo6xfjr.jpg

http://i184.photobucket.com/albums/x...psohnhha1j.jpg

http://i184.photobucket.com/albums/x...pswa4tifzw.jpg

Just food for thought.

I'm sure the baby moons and tiny sport mirrors help a bit.

Perhaps go one step further and seal off the gap between the cab and bed?

Kach22i
 

I hope I haven't offended
2
Agreed reduction of A is a large gain. in this old dodges case loss will occur apon repars being made . Ill explain . This model of dodge uses an aproxamitly 3" tall 0 rete spring rubber for proper ride hight. Theas last (from what I've read) aproxamitly 100,000 mi 10-15 years. My truck on the original rubbers @275,000 and 25years the rubber is about as thick as a pice of paper. = ~ 3"lowerd in the front. Stock rear /~ 17" under the hitch. So whin i get this defect repaired the A will grow.

If the Montana roads and 4-8"ice ruts hadn't taken out 3 Ball joints in 6 months, I would not be considering raising the front end. Cause and effect. I think the Ball joints are operating out side an accepted operating angle causing failure.at a price of $100.00 ea upper and 75.00usd ea lower purchased yesterday will in stall in near future. With theas NASCAR spring rubber less the splits ABA testing will be labor intensive but valid. I will have to do a life span test to determine. If the accelerated Ball joint wear is worth the extra FE of the lowered front
I would rather keep it low and find some geometry corrected control arms . Then 4 link and bag the rear for load compassity.
Point#3
Appearances can be deceiving.
Some of my design requirements to call a truck a truck it must maintain the ability to:
1 haul 1 cord (4'×4'×8' neatly stacked) fire wood, wet/green Oak ~ 3,000lbs . (This will fit under the cap as in the wrapped load pic the top duse not nee to tuch to bed this load travaled 800 mi with no trouble at 69-75mph)
2 have at least a class 3hitch with a min of 10,000lbs WD
.
If theas 2 are not true itis not a truck, then its a glorified car and the mod isnt practical.
Hence all modds must pass this litmans test
For my cap
easy and quick removal by 1 person (v1.2 =35lbsV1.0=21lbs sub 5min removal, it takes longer to tie it down than to r&r the cap, with my current cap. Note: it duse help to point the truck straight into the wind for installation as the windvaine effect can be strong
Point 4
Allready discussed my method of lowering .. more details to solve this lost compassity. Add some ride hight controls mechanical lenkage or go high-tech decade old tec magnetic, these are both load compensateing .
Eg of a random load that found its way to my truck to day
Attachment 20309
Attachment 20310

Moons would help .
Larger mirrors are already wanted . For towing safety.

Sealing off the cab i finally spent the $3 on pool noodles on tusday on Wednesday I got a personal best on my 200mi mpg test route 29.3south and 27.26north an aproxamitly 1.5mpg improvementin each direction . I have wanted to rebuild the headache rack when I first built it (I should have measured twice and welded once .to close the gap to .5-.325" .
Nice truck .
Like they say no pic no happen so
Attachment 20308

gumby79 you are to be commended for using your truck like a truck, for ingenious packing/loading skills and just the functionality in general. I did not realize the cover was able to tilt up like that.

I'm not a big fan of lowering a truck, Montana where you live and Michigan where I live it makes little sense.

I mostly mentioned it as an alternative.

In design one makes design decisions, best way make a decision is to have a choice between two or more schemes. I'm sure you went though many ideas and tossed out more than you kept to arrive at your current configuration.

Thank you for the detailed and well documented explanation, I feel like I learned something.

SIDEBAR: If you know of any International Scouts (1960-1970) for sale out your way which might NOT be showing up through the usual Internet resources, give me a shout. For some reason I'm attracted to boxes on wheels, perhaps it's the challenge of getting them to be more aero friendly, not sure.

I wonder if they make square or rectangular stock pool noddle extrusions. Might fill the gap between cab and bed a little more cleanly. What you have done now looks pretty good, but I also understand what I am looking at. Strangers to aerodynamics might not be so accepting, but screw them. ;)

Well, I'm offended by that. Man up! It's only words. :)

This is your main constraint. All the air below the vehicle has to be herded through that opening. An at least partial bellypan, of course. I suggest a difusser made by fences that start inside the rear tires and curve outward to 38". Like this only with more ground clearance.

http://ecomodder.com/forum/member-fr...bonnevette.jpg

The only reasonable angle for the tailgate is 0°, so as to not compromise load/unload (it's in the middle of the wake anyway). There is a 17x38" space below that could have some structure added or unfolded.

hitch tube fairing
 

If the hitch structure is above the bottom of the differential's pumpkin,there's a very good chance that it's embedded within turbulence and the wing-like fairing wouldn't function.

I looked his truck over the other day. We commiserated about the usual difficulties of truck belly pans, the accumulation of dirt, rocks, water which becomes ice that never melts for 2 months and tears things off. The usual :p
For example, My ex-logging truck has 30 pounds of dirt on the top of the tank I have yet to remove. It got up there as dust, got glued down and is now wrapped around important things like wiring and fuel lines :D
My thoughts are to leave the bumper on and figure out a pan that will let stuff go. I was thinking something like the louvered covers on an 80's camaro rear window. sheet metal with big vents that you can hose out at the car wash, that still calm that progression across the bottom. I think it will work, it is just figuring out a way that is cost effective and durable.

I would think instead of louvres, an expanded metal mesh or perforated steel plate.

There must be something like an index of refraction for air. If it's coming straight at the perforation it goes through but if it is flowing along the surface only a percentage will flow... either in or out depending on the pressure differential.

The louvers would allow you to pressure wash it out without removing anything, at least that was my thought. expanded metal is pretty grabby, but hey, it might work.

Perforated, undimpled plate is probably better. You could control the size and spacing of the holes.

Maybe some strategic openings to pressure wash or steam clean through.

Progress note.
Got this for $20 when I was in California 30"x8'.
https://ecomodder.com/forum/attachme...1&d=1589169888

Then I turned it into this.
https://ecomodder.com/forum/attachme...1&d=1589170866

Not seeing it. The aerocap is still boat wrap, isn't it?

Did you make a bellypan?

A new roll pan bumper/2 turn / brake lights and one turn only, 2x6"flush mount LED , and 3"4x1w recessed backup lights..
The new bumper incorporates 7 1/4x20 both old holes or terminating the belly pan.
It has definitely had an effect on the air flow pattern, tailgate s now getting covered in dust .I don't know if this is being drafted up through the hole as intended or if removing the parachute style bumper has added a dirty air recirculation bubble? tuft testing is in order

Okay. Hiding behind all the lights (and paint?).

Yes, Ford tractor Gray Implement paint is almost a perfect match for Dodge White.
A side view
https://ecomodder.com/forum/attachme...1&d=1589230395
(Sometimes computers don't like me sorry it's upside down it wasn't)
And you can see how far the hitch sticks down below the body work representing how much further the Factory bumper protruded, then my custom.
The Nissan Leaf trunk section belly pan panel that I have is going to do a very nice job of completing the belly pan from the differential to the bumper, granted I got to make some filler panels nad mounts to get her tight. The front section of belly panel from the Nissan was almost ready to bolt in shape wise. Time to finish getting the truck unloaded and build my sidewalk then I go play with the new to me 2" magnehelic gauge ,wont help with the bumper but it'll help with the belly pan and cooling stack

On a stability note at Interstate speeds I have noticed small cars have a new effect as a pass my rear quarter. The effect is most pronounced in crosswinds, when there bow wake pushes into the rear wheel well , the back of the truck gets light and starts porpoising slightly. In clean air she feels more planted than before.

roll pan
 

Purdy! Real purdy! Nice goin! let's keep an eye on that small car effect.:)