Belly pan or vortex generators?

[piekar]

i don't know if this has been posted before, but heres something i found about vortex generators


http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

[Shawn D.]

Originally Posted by Xringer

The blades interlace?

Whatever it's doing, it's not like EM fields being canceled out while flowing in twisted pair wire.

No, they don't "interlace" -- that's taking the analogy a bit too far! The vortices roll against each other like gears (that don't mesh, so don't go there!).

[idtent]

well as far as making the zig-zag i would have access to a laser cutter with a cutting area of 18"x12". i think all i would need is an .eps file to make it work. but about air tabs at work the tech at work installed them on a cube van, and the truck sways a lot less in a cross wind and when a semi goes by the van is not sucked into the semi's wake, but the estimated mgp gain was >1

[Xringer]

Where were the AirTabs installed on the van? (Pics would be nice).
It's very interesting to see where people stick those things.
I loved the Vet with them all around the tail end..

Most of what I've read seems to say not much if any improvement in cd, but sometimes it's worse.
But some report much improved handling in crosswinds etc.

[edbso]

I continue to be blown away by the large positive effect of the Zig-Zag tape. I have now had a chance to drive the Matrix at speed in the rain. The air flows right over the side windows completely scrubbing them of water droplets. All you can see is little water drops the size of pin heads being blown to the back of the car. The wind noise continues to be dramatically reduced too. Even if there are no positive mpg results that makes it worth while.

Next project is rear wheel skirts. I have decided to make them out of 8 ounce fiberglass cloth and polyester resin. I prepared a piece of two inch thick blue Styrofoam to be used as a mold. It cuts easily with a knife and 100 grit sand paper in a palm sander cleans up the edges fast. I then covered it with aluminum foil. If not covered the polyester resin will eat away the Styrofoam destroying everything. It worked really well until I decided to unmold it, which was easy. However the skirt warped with several ripples in it. I guess I took it off before it completely cured. I will likely remold it and apply a couple of layers of polyester resin and then some Bondo to smooth it out.

Here it is remolded.

Having learned my lesson on the first one I will not unmold the second skirt until I have painted it. I have applied the fiberglass and 3 layers of polyester resin and have a very good smooth outside surface. After it cures completely I will paint it and then unmold it and if necessary reinforce from the back.

It looks much better, even professional!

[donee]

Hi Edbso,

Its common to use epoxy resin when bonding to polystyrene foam core materials. But that is not your issue. Also, its resin, not rosin. Rosin is a amber material used as a flux in soldering. Its also powdered and used by athletes and mountain climbers for extra traction/grip, as well - baseball pitchers, gymnists etc.

A better way might be to make a postive foam pattern, which you coat with epoxy resin, sand and apply 4 or more coats of beeswax too. Then push that into a liquid resin that is damned around 4 edges on a board. Use another flat board to get the back of the pattern flat. Check it with a straight edge. After the resin hardens you pull out the pattern. This makes a negative tool. Apply beeswax or other release agent to the tool, and do the fiberglass into it. Alternatively, you can model the part in 3D, and send it off to a CNC Router shop to mill out the negative tool cavity from soft wood. Then coat the wood with epoxy sand and polish.

You might also vacuum bag the part while it cures. Vacuum bagging is easy to do. All you need is a vacuum pump (like for HVAC), or a venturi pump and air compressor to generate the vacuum. Woodcraft sells supplies for vacuum bagging.

[edbso]

Originally Posted by donee

Hi Edbso,

its resin, not rosin

Thanks, spulling corrected, grammar OK?

[nwbabybronco]

I talked to a guy the other day with $130 in air tabs on the back edge of his Sprinter. He was not a happy camper. I sent him to this site to get the real info.

[donee]

Hi NW...,

That may be too many. $130 is like 65 of those things. They are supposed to be spaced out like about 6 inches on center, or something like that, between em. 65 would then be 32.5 feet worth. If the top and sides are the same length, 32.5 feet would be for a 11 foot tall box.

Why not take every other one off, and see what happens.

[nwbabybronco]

Alas, he is somewhere between Colorado and Canada. Good to know, though.