MetroMPG's Honda Insight boat tail extension (cardboard) tuft video; ABA test +9.7%

[pascal28]

Serrated nozzles on aircraft engines are for noise reduction. They have a slight efficiency penalty. They were put on the engines (Trent 1000 & GEnX) powering the Boeing 787 due to concerns that its composite fuselage would transmit more noise than a conventional aluminum one. They reduce noise by encouraging mixing between the hot & bypass flow and between the bypass and free-stream air. This reduces the shear force and consequential noise generation.

[aerohead]

The Hughes OH-6 Cayuse (hope that's correct) morphed into the Allison turbine-powered M-D 500,with 5-bladed rotor of low rpm/high static pressure.
The US ARMY flies these out of Fort Bliss at night,with no lights,and you can't hear them until they're on top of you.
I suspect that the 6-blade prop helps in the same manner.
Thanks for images!

[aerohead]

Originally Posted by pascal28

Serrated nozzles on aircraft engines are for noise reduction. They have a slight efficiency penalty. They were put on the engines (Trent 1000 & GEnX) powering the Boeing 787 due to concerns that its composite fuselage would transmit more noise than a conventional aluminum one. They reduce noise by encouraging mixing between the hot & bypass flow and between the bypass and free-stream air. This reduces the shear force and consequential noise generation.

I believe that this technology is an outgrowth of NASA's acoustic and body-morphing research of raptors,specifically the peregrine falcon and one type of owl.(please see PBS' NOVA's 'Raptor Force')
Critter-cams attached to both birds revealed damping abilities owed to aft-body feather and down architecture.
Earliest winglet technology was also modeled after buzzard wingtip feathers which not only cut drag,but also attenuated noise propagation from the reduced shearing forces.

[freebeard]

Critter-cams attached to both birds revealed damping abilities owed to aft-body feather and down architecture.

Dinosaurs used to be covered with feathers, maybe someday our cars will be too.

/silly vortex generators

[benphyr]

Originally Posted by MetroMPG

...something a bit sturdier than trash bag plastic, which is what I used to cover the Flea's test tail .

I have a roll of plastic that gets used for covering table cloths and what-not. It is clear, heavier than garbage bags, just a little bit stretchable, and you may have however much you need for free...if you are going to be in Hamilton anytime soon. It is a big roll, I am sure there is more than enough.

Cheers,
Ben.

[MetroMPG]

Not going to be in your neck of the woods any time soon, but thanks for the offer!

I was hoping for black plastic as well... so I wandered around Home Depot this morning looking for something and struck out. Seems I'll probably just end up getting some heavy duty garbage bags.

[mavinwy]

Check the plastic that they use for under gravel (usually gardening suppliers carry it) Black and fairly heavy duty.

Don't remember the name offhand.

[Frank Lee]

[MetroMPG]

Thanks, mavinwy... I did find some, but it was only available in 50 ft rolls. Enough to do a fleet of tails!

I ended up getting some "contractor grade" oversize trash bags. 3 mil thickness feels about right. 4 mil was also available.

The last coat of paint is dry, so adding the plastic is the next step.

[jime57]

Originally Posted by MetroMPG

Thanks. Did you post a thread for your undertray?

Sorry to be so late. Been very busy with the Mid-Atlantic Meet. Here are a couple of pictures of the underbelly:

Insight Belly Pan Photos by jepting | Photobucket

I used aluminum sections in front and back, and large coroplast panels in the mid section.

Testing is near impossible here in hilly Richmond VA, and with lean burn popping in and out, so I don't have actual performance numbers. This car also has 90% grill blocks and removed R side mirror. I was able to drive it to 112 MPG last summer over the 90 hilly miles from Richmond to Quantico VA, so the car is pretty slick