Aerodynamic Bed Cap Add On-- UPDATE w/pics!

[bobo333]

an intesting aero semi trailer design i just found that may interest you, looks to be a similar shape to what your planning (just bigger)

M and S Cuts Carbon With Teardrop Trailers

[MetroMPG]

Just checking in: have you seen bondo's clever "convertible" solution? You could design something like this which converts from an aero shell rather than a tonneau:

http://ecomodder.com/forum/showthrea....html#post5037

[caliboundranger]

Got my hitch installed and now working on the braketry for the carrier storage box. So far so good. here's a few pics. will probably have the full structure of the carrier done tomorrow. have gotten very busy at the shop and not enough time to work on this thing. still need to put everything together under the hood. just need to get some material to make the heavy duty hinge pins. here's a few pics;

Hitch mounted up;


Making hitch mounted arm for hinged carrier;



What a mess lol


A few weld close ups; not my best but it will suffice,


Some project trucks were working on at the shop: ) a few things i take pride in





The beginning stages of the carrier main frame. I know its hard to tell from the pics whats what but after a little more fabrication it will come to view. I eyeballed the angles as close as i thought to 10*. The sides taper in as well as the bottom tapering up toward the rear. The top will also have taper that will follow the curvature of the top air foil.



It's all coming together : )

My Shop...ie..my home...

I have a bunch of money coming in from jobs by wednesday so i should be able to pick up my aluminum sheet and piano hinges to dress it all in. Thinking of using polished aluminum.

[Sporty Modder]

Very nice keep up on the progress.

[caliboundranger]

Heres the latest:



Got the frame about half done. Get the hinge material in the morning and should have the rest of it tacked up by tomorrow evening. I think i'm going to add a little more incline to the bottom to get it closer to the 10* point. I am currently at about 4. Downloaded angle meter app and it is suprisingly super accurate.
Timing belt is back on and engine buttoned up and now just waiting on one more water inlet to have everything under the hood complete.

To Do List:

-Finish carrier
*Finish carrier inner structure.
*Make latch for carrier
*Paint carrier frame
*Skin Carrier and add shelving
*Install ail lights
-Install Front Bumper Rubber Air Dam
-Bend up top air foil
-Fabricate wheel well covers
-Fabricate wheel covers
-Remove mud flaps
-Run power wire and install 2000w Inverter
-Make shelving in bed

[MetroMPG]

Originally Posted by NeilBlanchard

adding an arched top will probably help the overall drag, even if it adds frontal area

I've seen conflicting info about this. I'm fairly sure Hucho says the results of adding frontal area to achieve a lower drag coefficient will be a wash. However we've also seen that U.K. company adding camber to the top of transport trailers/large trucks and claiming an improvement.

Since we've got experts on either side of the fence, I'd personally stick to tried & true before investing a lot of time & materials in something that increases frontal area.

Or better yet, mock it up with CAD (cardboard aided design) and do a proper test on the vehicle in question.

[ChazInMT]

Isn't the lowest possible CdA what we're after here. Seems to me like if adding 4 square feet to a 78 square foot truck with a Cd of .43 and getting the Cd down to .37 we'd go from 33.54 CdA to 30.34 CdA, looks like a 10% improvement to me.

I think it's a matter of how much of an improvement can the frontal area adding modification make. In this case, it seems if the top foil is executed well and the front transition area can be improved as well as getting close to template in back, I'd think there would be about this type of improvement of 10%. I'm not being unreasonable on my numbers here am I? I don’t think the Ford Ranger with a “traditional” square cap is doing much better than .43 and a .37 Cd isn’t an unreasonable spit wad number based on the other projects we’ve seen done and get all excited about. Adding 5% area to get a 10% gain, and with the tail cone, the Cd should drop to .32 or better leading to a 22% overall improvement.

[MetroMPG]

Originally Posted by ChazInMT

I'm not being unreasonable on my numbers here am I?

I don't know - and neither do you. That's my point.

That's why I personally wouldn't take that approach without properly testing a mockup (an easily made one) first.

[Sven7]

15% improvement without a full boat tail? I don't know. Certainly not with straight, 10 degree plan taper. Of course the FA addition is only 5% of the original, but then you'd have to get over 10% aero improvement to make up for that. It'll be interesting to see. I hope these mods are un-boltable so he can do ABA testing.

[MetroMPG]

Found the Hucho reference (4.4.4 in Aerodynamics of Road Vehicles), and he's certainly cautious when approaching the problem (raising the roof & frontal area to decrease Cd). Essentially he says what we have: it's technically possible, but not without experimentation to ensure the additional A doesn't outweigh the decreased Cd.

That supports my advice that it would be risky to just "guess" at this and build something permanent.

EDIT: he says essentially the same thing about increasing side camber (and A) as a means for reducing Cd, in 4.4.6.

FYI, there's already a decent thread on the issues in this particular debate, so I'll stop commenting about it now.

http://ecomodder.com/forum/showthrea...bad-20460.html