Designing Aero-cap: Make it in Sections?

[Diesel_Dave]

I'm working on designing an aero-cap for the White Whale. I've been gleaning quite a bit of information from different threads on the do's and don't's. Shortly, I should be able to post some images of my CAD drawings. I should note here that my expertice is more in engine efficiency than it is aerodynamics (I'm learning )

From what I've gathered, it's important to keep the slope equal to or less than 12 degrees. Right now I'm planning on using 11 degrees (both from the top down and from the sides inward) and then smoothing out the transitions. As far as the construction goes, I'm planning of doing something similiar to what Fubecca did (ribs covered with thin sheeting covered with plastic).

One thing that I've been picking up in the threads is that people make an aero-cap, it works pretty well at boosting mpg's, but then people end up not using it because they can't use their bed very well with it on and it's a hassle to take it on and off all the time. Here's a solution I'm thinking about: make the cap in 3 pieces (front , middle, back). That way it's really easy to take it off by myself--each section would be fairly lightweight and relatively easy to store. Plus, depending on what I'm hauling I can leave 1 or 2 sections on, getting at least some benefit.

What are everyone's thoughts? Is it a good idea? Has anyone tried this?

-Diesel Dave

[BamZipPow]

Yup...that's exactly what I did...
http://ecomodder.com/forum/showthrea...dea-15137.html

The key will be how you connect the pieces together. I found that unless you have a good fastening system on the front and side pieces...it will wobble a lot...and may self-destruct.

My hatch is similar to bondo's commercial setup as I can remove it when I need to put in taller items. I went with a frame and Coroplast sides as I didn't want to put a whole lot of money in the development until I found a good shape/design to work from. I still have to add in more supports in the sides...

[Diesel_Dave]

Looks like you've had lots of fun

I'm talking about making 3 sections "cross-wise" rather than "length-wise" like you did. It wouldn't be quite as convenient as a hatch, but I think it would be simpler and sturdier. The concept is sort of like a hard panel-type tonneau vs a hatch-type one.

Apologies for the crudeness of the sketch, but here's the basic concept (attached).

[Frank Lee]

I was thinking of how the late Batmobile's armor comes out when I read your first post.

[BamZipPow]

So I guess more like a collapsible cup...

[botsapper]

Here's a nice demo ...and assistant.

http://www.youtube.com/watch?v=E5LNq2Fbo4Q

[Diesel_Dave]

That's pretty much the idea...If only I had an assistant like that!

[KamperBob]

Originally Posted by Diesel_Dave

I'm working on designing an aero-cap for the White Whale. I've been gleaning quite a bit of information from different threads on the do's and don't's. Shortly, I should be able to post some images of my CAD drawings. I should note here that my expertice is more in engine efficiency than it is aerodynamics (I'm learning )

From what I've gathered, it's important to keep the slope equal to or less than 12 degrees. Right now I'm planning on using 11 degrees (both from the top down and from the sides inward) and then smoothing out the transitions. As far as the construction goes, I'm planning of doing something similiar to what Fubecca did (ribs covered with thin sheeting covered with plastic).

One thing that I've been picking up in the threads is that people make an aero-cap, it works pretty well at boosting mpg's, but then people end up not using it because they can't use their bed very well with it on and it's a hassle to take it on and off all the time. Here's a solution I'm thinking about: make the cap in 3 pieces (front , middle, back). That way it's really easy to take it off by myself--each section would be fairly lightweight and relatively easy to store. Plus, depending on what I'm hauling I can leave 1 or 2 sections on, getting at least some benefit.

What are everyone's thoughts? Is it a good idea? Has anyone tried this?

-Diesel Dave

Dave, sections make a neat idea that I haven't seen yet. Here is some food for thought. Plastic covering needs ribs for strength. Each section may need it's own ribs to stay together while handling especially by yourself. That could add some weight.

I haven't built an aerocap yet (other priorities). I designed several and feel 1/4" foam coated with fiberglass is a prudent approach balanacing cost, strength and weight. I lean towards a one-piece hinged, removable lid like Bondo and BZP for bed utility as you mentioned. I'd lay it up section-wise to arch the back, match the cab size and slope cleanly over the tailgate. My preference would be to exploit the full potential of flow attachment.

Wedges seem to give wake stuffing benefit at least, and flow reattachment at best, so that does help noticeably. Simpler geometry is easier to make so I "get" the appeal and bang/buck proposition. BZP is doing well with coroplast and simple curvature.

No matter which way you go I look forward to following your progress.

PS: I'm in IL near Peoria. Are you in near or far IN from me?

[lunarhighway]

how about something like this?

a cap possibly a fabric covered frame or any other light constructionthat can swing up, and has build in struts to lock it in position

(i envision it a bit like a large hatchback) the sides in open configuration could be filled with fabric covers that when carefully designed could remain in place when the cover folds close, allowing good access, instant switch between aero and cargo

[Diesel_Dave]

Bob, I'm in central IN (just south of Indy).
You’re definitely right about the ribs for strength. I’m thinking of at least 2 ribs per section. I was originally thinking of putting ¼” plywood over the ribs and then putting plastic wrap over that. Now I’m thinking of just using coroplast over the ribs. I’ve done woodworking projects for years so I tend to think that way I guess. Also, I’ll be posting pics shortly of the shape I’m thinking of.
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Lunarhighway, yeah I thought of doing a “hatchback” like that. There are a couple things I don’t really like that much about it. First, the hinge mechanism is going to have to be very sturdy (and if it's curved, you can only put one hinge in the center), particularly if I’m going to travel with it in “cargo” configuration. Secondly, if I haul something taller than the cab height I’d have to take the whole thing off anyway.