Tonneau With Steps

[aerohead]

Originally Posted by Big Dave

Kamper Bob:
1. Mine's always been a one-ton. You must have me confused with someone else.

2. I have no intention of going to 22 degrees. I have to step down a total of 22 inches in an 80 inch run.

3. I'm gonna do open sides. I'm looking for some visibility so I can cut down or eliminate my side mirrors.


CFG:
Thanks. That's what I'm looking for. I'm thinking two flat plates attached parallel to the top of the hard tonneau. Use the top of the tonneau as the zero datum, I thought the first one might be set about 14 inches above the datum and the rear one 7 inches above the datum.

I'm thinking 14 gauge aluminum with some welded longitudinal stiffeners. I'll also need stronger gas struts for the lift mechanism as the tonneau top gets heavier.

Dave,I don't know what your budget looks like,but both Wicks and Aircraft Spruce and Supply carry a beautiful aluminum hat-section designed specifically for stiffening.

[Big Dave]

I'm planning to use threaded rod struts at first for the steps. That way I can experiment looking for the best angle & spacing. The struts should be out of the high-energy air stream, but once I settle down on a design, I'll use something that looks a bit better.

The big question in my mind is how far back should the first step begin. My problem is I cannot just snug it up on the cab bulkhead and expect to be able to open my tonneau lid. I look for the first step to be 6-8" below the cab top and the second one will split the difference.

I'll probably have to breakover and buy a scan gage even if my engine control tuning makes a hash of readings. Maybe the error will be consistent and I can find a "best" configuration and then test it the old-fashioned way for real performance.

[KamperBob]

Dave, I thought it was an interesting enough idea to start modeling it myself. Being able to raise the lid concerned me too. Solvable though.


Our truck box dimensions appear more alike then different. If you want the model as a head start, let me know.

Cheers
KB

[euromodder]

Originally Posted by Big Dave

I have a makeshift aerolid. It is suboptimal in my view. Too steep (17 degrees) and I'm blind as a bat to the rear, thus married to big side mirrors. But at the same time, it was a 1.5 MPG improvement over a hard flat commercial tonneau, so the thing had some virtue. Therefore I'm on the lookout for something different: Better smoothing of air flow and better visibility.

Maybe I'm missing something obvious, but why not fit transparent panels (Plexiglass, Makrolon) to the makeshift aerolid ?

[Tweety]

How about something like this?

It's a very crude drawing in paint, I'm at work so the computer has no software for anything else...

The red part is fixed to the cab/bed and not moving, covering the gap, making it possible to leave room at the front of the stack for opening the cover, while still covering the gap... I'm no aerodynamics ace, but to me it seems reasonable that the air should "see" this as the same as the cab being longer? And considering that the steps and the "bar" overlap the gap should "disapear" in terms of aerodynamics, right?

And it should still be "short" enough to give good rearview...

Just a though...

[Big Dave]

Kamper Bob:

Amazingly close to what I had in mind.

Staring at the truck last night I had a minor brain drizzle.

If my top step were located 4 inches down from the top of the cab, it would be completely out of view (a positive).

I was thinking of making the top step about 24 inches long. The second step would then have to split a 18 inch gap and would be 30" long.

A 12 degree Kamm treatment has my last step 8 inches above the back of the bed.

So to get the smooth flow Bondo gets (the wind tunnel says he has set the standard), I'd need three steps added. Front one 18 inches above the ARE tonneau spaced maybe 6 inches back from the cab bulkhead (to allow clearance when the lid is lifted) extending maybe 24 inches. Center plate fourteen inches over the ARE tonneau and 30 inches long. Rear plate 8 inches over the ARE tonneau and extending 6 inches beyond the end of the bed. 80 inch short bed.

A final refinement. I radius over the last 12 inches of each step 0.125 inches. Just a little downward turn for the air flow to help keep it attached. Whaddaya think?

[KamperBob]

Dave, I find design kinda hard with text. Too often a word means different things to different people in my experience, and when ya string em together it dont help much; so pictures work 90% better for me.

I'm attaching a Google SketchUp model. (Trying anyway; my first attempt to do so at this site; fingers crossed...)

Cheers
KB

[botsapper]

Add flying buttresses & then add the louvers. 70's-80's fastback flashback! ...had a Z with those things.

[aerohead]

Dave,since a cab-wing with half-tonneau has almost as low drag as aero-shell,what about a wing complex like KamperBob has shown,hinged at the rear uprights,and pinned at the front.
When you need to get into the bed,you pull a couple clevis-pins,tip the wing complex backwards,allowing clearance for the tonneau to swing up and open.
You could still mount the wing complex close to the cab without losing access.
Just s thought.

[KamperBob]

Originally Posted by botsapper

I give it a 10 for style but have to wonder if aero + dually = oxymoron. LOL

Cheers
KB