Advice on aero-cap shape

[hat_man]

Thanks to everyone.

Chaz...the pics I used aren't of my truck. Just to show the shortbed and have something to use with a paint program. All the colored lines are just guess work and to show a concept of 1,2,or3 angles used to make up the shape. I'm not sure what you mean by "lift gate". If it's the height above the tailgate then I haven't decided on anything really. It will be wherever it comes out. 12* straight from the cab would seem to cut way into the "template", where using 3 angles seems to more closely approximate it. Using the "something is better than nothing" philosophy, I think I am going to go for 2 angles of 5* each. The difference in the 10* slope is minimal from the 12* slope (thanks yugomodder) and only using an angle finder and my trusty EMT bender I might be off a bit. If I go over 12* then it's not so good, but if I shoot for 10* and miss then at least I'm in the ballpark for some decent results no matter if I miss +/-.

Skyking...I'm just a lowly electrician not a body and fender guy lmao. I am thinking about some rear skirts though. If I change the rear end to something with the 3:45's, I think some of the earlier model Rangers had rearends that were 1" narrower on each side. That's the ones I am looking for. That coupled with changing from 225 width tires to 195's and lowering the rear 2" should give me plenty of room for full skirts. If not I am thinking of gap fillers like on Cons Ranger. The stepside bed is only 44" wide so no plywood or sheetrock in there lol. I don't haul anything really anyhow. It was what was available when the old truck died. I didn't know anything about modding then. I'll try and post a pick of what I am thinking of for the side shape soon.

[ChazInMT]

OK, refined version of what you're trying to do with self explaining captions.



Bigger Version of Pic

[skyking]

Originally Posted by hat_man

Thanks to everyone.

Chaz...the pics I used aren't of my truck. Just to show the shortbed and have something to use with a paint program. All the colored lines are just guess work and to show a concept of 1,2,or3 angles used to make up the shape. I'm not sure what you mean by "lift gate". If it's the height above the tailgate then I haven't decided on anything really. It will be wherever it comes out. 12* straight from the cab would seem to cut way into the "template", where using 3 angles seems to more closely approximate it. Using the "something is better than nothing" philosophy, I think I am going to go for 2 angles of 5* each. The difference in the 10* slope is minimal from the 12* slope (thanks yugomodder) and only using an angle finder and my trusty EMT bender I might be off a bit. If I go over 12* then it's not so good, but if I shoot for 10* and miss then at least I'm in the ballpark for some decent results no matter if I miss +/-.

Skyking...I'm just a lowly electrician not a body and fender guy lmao. I am thinking about some rear skirts though. If I change the rear end to something with the 3:45's, I think some of the earlier model Rangers had rearends that were 1" narrower on each side. That's the ones I am looking for. That coupled with changing from 225 width tires to 195's and lowering the rear 2" should give me plenty of room for full skirts. If not I am thinking of gap fillers like on Cons Ranger. The stepside bed is only 44" wide so no plywood or sheetrock in there lol. I don't haul anything really anyhow. It was what was available when the old truck died. I didn't know anything about modding then. I'll try and post a pick of what I am thinking of for the side shape soon.

Hey, I just wanted to be first in line to cheer you on if you went that direction

[hat_man]

I See what you are saying now, but I still have a question (silly as it may sound). Take a look at the pic and see if we are talking about the same thing. I was thinking it was the first 4* ( I had just quick guessed at 5*) and then 6* more to total 10*. Is that right?

It looks like it's between 18" and 24" back from the cab to where the angle changes.

Thanks for the excellent pics and overlays

[hat_man]

These are my ideas for the frame shape.

The orange bed shows the tapered bottom frame. Wider next to the cab and narrower at the rear.

The purple truck shows the side idea. The numbers on the right are in degrees from horizontal. The ones on the left are the degrees of downward slope. The only reason for the 6*/10* thing is I think Chaz and I are talking about the same angle but I'm not sure how to write it.

At this point it's all just guess work. Except for the angles from Chaz. I am pretty sure that's what I am going to shoot for. I am open to all suggestions though.

Thanks to everyone

[skyking]

I'd leave the frame out in the back to try and smooth that flow there. The rest is great.

[yugomodder]

I think you've got the right idea. If you shoot for around 10 degrees and miss +or-, you're still looking at a huge improvement in fuel economy. I think you've got the right idea on the sides too. If what you're getting at is to first mark the profile for slope on the top and sides, and then go from that intersection down to the side of the bed for a transition, then that should work really well. It sounds to me like you've got blueprints in your head for how you're going to build it. You should be able to get the shape right, or at least close enough to get the benefit. The next question is, what are you going to use to build it? I'd suggest using some sort of transparent material at least for the vertical piece on the back to allow for some rear view.

Please keep us updated on your progress.

[hat_man]

I had thought about that Skyking but was afraid that the air might get caught up in the space directly behind the cab, over the wheel well, and at the rear (somewhat). The cab is 63" wide (outside to outside) and the bed at the rear is 53" (outside to outside). If I keep the frame rectangle shaped as opposed to tapered this makes a 5" overhang above the red line in this pic. Wouldn't that be a problem? The tapered idea at least only gives me an overhang at the space directly behind the cab. That and I thought the tapered (boat tail?) effect was better than straight 90* lines. I am just guessing here but I thought I had read that here somewhere. Not saying you're wrong, just trying to remember what I thought I think I maybe read sometime in the distant past ago in some thread some guy posted in some forum here. LOL

I am anxious to get started but I know it will be a slow going process. Lots of trial and error with the emphasis on the error part for sure. But hey, that's what it's all about isn't it?

Thanks again for all the advice.

[hat_man]

Thanks yugomodder. I am thinking about 1/2" or 3/4" EMT for the frame. It's a material I am very familiar with. 20+ years as an electrician and probably 20 more to go if the construction economy doesn't turn around soon. For starters I was going to use coroplast screwed to the EMT in panels so I don't have to fight the angles and transitions. I was thinking of a cheap pexiglass piece part way down the final (larger) slope with extra ribs added to give me a place to screw it to. I have an idea on how to make the bed accessible but I can't give away all my ideas, can I? LOL. I have to leave a teaser hanging out there to keep the interest up, eh?

Thanks for the help.

[Big Dave]

I've done some of the stuff you describe.

I general make you drive ratio as low as you can. I have 3.08 rear gears with a 0.8:1 Gear Vendor overdrive.

I lowered my 4x2 F-350 4" in front and 6" in the rear.

Both work.

Your truck presents an unusual opportunity. Having been recently whanged, you could rebuild your bed to taper in (in the plan view) about 5 degrees on each side. You'd have to shorten your tailgate and redo the side sheet metal but it would result in a true bullet-tail

Having overdone the taper I can tell you to slat your cap (elevations view down by no more than twelve degrees. To make the layout easy, use a 1-in-5.5 taper and chop it off at the back.

The distance you drive justifies almost anything.