Duck Tail on cap?

[Ed-in-Maine]

Hi Aero Guys.
I’ve been reading about Duck Tails attached to the trailing edge of pickup truck cabs and even Semi rig trailers. My question is looking at this picture do you think a duck tail would help me? The issue is the cap has this 1”-2” lip that runs across the trailing edge. Actually the lip is part of the contour changes in the top to give it strength.
Thanks for any ideas.
Ed

[Frank Lee]

Your cap is unfortunately the opposite of what is needed for the best aero: it rises up as it goes back instead of dropping down, adding more frontal area and increasing the wake surface. But if you need the function, and you want to improve the aero, a "ducktail" should help but it should be angled down, not straight back.

[Sven7]

Angle the ducktail down 15*. Right now it's doing nothing to reduce the wake. Also think of putting panels on the sides as well to reduce vortex formation.

[Ed-in-Maine]

Thanks Sven7, When you say panels on the side, do you mean like the Semi Trailers, full length, or some shorty vertical end cap? I'm not inclined to build the full length at this time.

Frank- Yes the cap is needed. We're migrating back to Maine shortly and the truck will be packed to the gills again.
Ed

[kach22i]

I think they mean like this.

Automobile 2 - Odds and Ends pictures by kach22i - Photobucket

[skyking]

Ed, that will lengthen your truck a bit. Go all the way and put sides on it, call it a folding boat tail. boat tail = profit!

[Sven7]

What Kach said! The longer you make it, the more benefit you'll see.

[Ed-in-Maine]

Kachi22-That looks great and it would not interfere with loading or visibility
Any ideas on material selection available at Home Depot? I bought a small piece of colorplast the other day but I don't think that would be strong enough without some framing. I'm just thinking proof of concept i.e. a 700 mile run then I"ll build something better when I get home, serious lack of tools where we are now.

Do you know what the red cars duck tail is made of?
Thanks
Ed

[skyking]

Maybe some 1/4 ply with ribs to keep it from flexing, and if you like it glass it with white pigment in the resin. Couple of fill coats and sanding and it would match up nicely.

[mcrews]

use aluminuum angle iron. The sell it at the big hardware stores. It's light and easy to work with.
You can frame it up and still use the coroplasst.
U can also use some aluminuum flat stock.