what is the Cd of my trike?
 

Note the back is "behind" the front - so I add the frontal area of the hood plus the frontal area of the "greenhouse" - windows and above.

Any guesses on Cd?

Aero?

under .20????? (I am hoping?????)

How long have you had this one?

started it last december - hoped to have it done for the vetter challenge in call, but didn't get it done.

new hope is on the road in the next 2 weeks..... depends on money/time.

Have you tuft tested it? I don't think it will be below 0.25, but it might be close to that -- the front fenders are probably going to have turbulence behind them. Does the cooling air exhaust out behind the front fenders?

That was my first concern, so much so that I assumed this was a found object being finished up for fun.

I've put a big white "X" in where I think infill from the front fenders may help.

Automobile 2 - Odds and Ends pictures by kach22i - Photobucket
http://i184.photobucket.com/albums/x...ised-zaa04.jpg

Perhaps a NACA inlet would work where the red "X" is.
SDS EM-4: Aircraft
http://www.sdsefi.com/rvrad7.jpg

A photo I took last week:
Lingenfelter-2012 pictures by kach22i - Photobucket
http://i184.photobucket.com/albums/x...2/DSCF6496.jpg

i bet your baby is ugly also.

it is pretty obvious, even to someone as dumb as me, some infill would help things out.

but it sure is nice having doors which open. and windows which go up and down. and the ability to use factory doors off a donor car.

and strangely enough, aesthetics are apparently important if I want to ever sell some of these. the cheese wedge look is not appealing to the ladies.

Sorry, I did not mean to sound rude.

I'm sure when it's painted a pretty shiny color it will be much prettier.

The practical aspect of door operation is appreciated.

I did recently photo an Enzo Ferrari which somehow gets away with a similar detail.

Lingenfelter-2012 pictures by kach22i - Photobucket
http://i184.photobucket.com/albums/x...2/DSCF6467.jpg

And the rear vent facing forward is also rather large.
http://i184.photobucket.com/albums/x...2/DSCF6465.jpg
http://i184.photobucket.com/albums/x...2/DSCF6463.jpg
http://i184.photobucket.com/albums/x...2/DSCF6468.jpg

The downside:
Ferrari Enzo
In my opinion, you have something closer to large motorcycle faring/cowling. However when compared to most cars, that is still a very low frontal area, so it's probably a wash.

Some positive changes worth considering.
http://s184.photobucket.com/albums/x...%20and%20Ends/
http://i184.photobucket.com/albums/x...00-Coments.jpg

If you want to get anything out of this site I suggest you quit taking things personally.
It would be a piece of cake, so to speak, to fair in the area in question during testing. Reach out the window and close a second panel, etc.
Then you'd know for sure the cost/benefit. I could make it faired off and still use that door and still have it all work if you are interested.

are you going to close in the front wheelwells, Basjoos-style, with a door?

I looked it up:
Basjoos Tells All About His "95 MPG" Aerocivic | Autopia | Wired.com
http://www.wired.com/images_blogs/au...ebuild15_2.jpg

Good question, that would help too.

I do not have true side and plan views of the trike in question, so I cannot overlay a template. However, the rear looks like it could be extended some.

Automobile 2 - Odds and Ends pictures by kach22i - Photobucket
http://i184.photobucket.com/albums/x...0-Coments2.jpg

Ain't nothing going to re-attach at the rear, unless the front is done right - in my opinion.

time
 

Al's gonna close the store in 7-minutes so I'm out of time basically.
Like the others,I'm concerned with the flanks,aft of the fenders.Your source flow at the nose is good,but the fender truncation will destroy the rectilinear flow to the tail,which can't 'sink' unless the onset flow is exceptional.
I've gor the same issue with the mini-hypercar.I will enclose this entire area with 'pod' for storage and side crumple zone to provide the gentle plan taper to the rear which the tail needs to function.
Your foundation is real good.Wish you didn't have the short deadline.

Aero, Thanks for your comments.

A few things. The 4 dimensional model is interesting. Yes, I have some stagnation area behind the front wheels, and yes I'm curious to find out what cut outs do.

If you look at the windshield, it is actually well behind the front fenders. I expect high energy air to flow off the hood, spill around the cockpit, and add adequate energy for the back of the car.

I'm pretty confident of that.

i'm so confident I put the goofy air scoops on the back to make ti look cool, but now that the car is outside, I hate the goofy air scoops at the back, and they are getting changed or removed.

as for covering the wheels, am I better to cover the wheels and close behind the fenders, or am I better off to leave the wheel wells open, open behind the wheels, and let air flow in the wheel wells and out the huge openings behind the fenders - basically make the back of the "fender" look like a fender, but not at all functional?

Is that how you built your car?

Kach, thanks for the photos, and apology accepted.
Yes, I'm a bit sensitive about my baby.

FWIW, the rear I purposely didn't take photos of. It is about 12 inches wide, has a 2 inch rim around it, and is already on the edge of functionally too long.

So when you really add up the frontal area, it is the hood, plus the cockpit above the hood, right??????
And you don't think air will spill "down" the sides as it goes around the windshield?

I don't think air will rush into the wheel wells to flow out the back, the cover suggestion is to smooth the flow across the rotating wheels. Also, having it open at the back will be quite messy in rainy weather. The wheels would toss all that grime right up on the side window and corner of the windshield.

Keep in mind that I'm not pretending to be an expert. I'm just trying to use my imagination, and think this one through.

Although at this late stage in the game a complete re-design or even modest modifications may be enough to stall you from getting on the road indefinitely, and I don't wish to do that.

This is what I think will happen now:
Automobile 2 - Odds and Ends pictures by kach22i - Photobucket
http://i184.photobucket.com/albums/x...nge2-zaa04.jpg

This is what a tightly curved or deep split vee windshield may do.
http://i184.photobucket.com/albums/x...ange-zaa04.jpg

it doesn't show in the pic, but the windshield is pretty curved.

Thank you for your excellent work on the pics - I have NO idea how to go about that kind of stuff.

I envision the B pic is what I have now, with turbulence from the sides.

If I had a FREE rein to do what I wanted, I would have dived the fenders at a 20 degree angle behind the center point of the tires downwards, and made the back of the fenders shorter.

But I needed to use an existing template as I don't have the skills to do the hood from scratch.

Does anyone recognize the hood?

The front clip reminds me of a Lotus.
It is looking good !
My suggestion, (eh gad not another one) is to round the front fenders ends off in a ergonomic type curve, something like the edge of remote control only bigger, for instance, where Kach22 suggest a curve back i suggest a curve forward and back.
Esthetically speaking that is.

The air flow is probably going to be a combination of the to flow diagrams that George posted. If you know that an ideal vehicle has air flow that is first accelerated outward in all directions by the front of the vehicle, and then smoothly closes back into place after the vehicle has moved past. To achieve this, the air pressure must be as even as possible all over the vehicle.

If there are areas of low(er) pressure, then they will pull the air away from the higher pressure areas. The largest areas of low pressure on this vehicle will be behind the truncated front fenders. Some air will flow through the front grill, through the engine bay and past the spinning front wheels (I am assuming) and then will exit into this area, and will partially "fill in" this zone, but this exhaust air flow itself will be turbulent, and may not form a trapped pocket, similar to the bed of a pickup for example.

The result will be, I think, that there will be both a lot of turbulence and a lot of air will be pulled down from the hood and lower windshield, as well. Maybe this turbulent area will allow the air flowing off the fender to "bridge" to a point on the rear of the vehicle and reattach? The only way to "know" is to tuft test it.

Here's a vehicle called the Trev that addressed this issue by having a really "fat" door, hinged at the back:

http://w3.unisa.edu.au/solarcar/imag...enfleet_04.jpg
http://w3.unisa.edu.au/solarcar/imag...es/trev_01.jpg

Trev (two-seater renewable energy vehicle)
Image archive

Ideally, the sides would be slightly convex; not slightly concave.

It's not the GF3 Mark Smyth Performance front end, which was my first thought.

JLP's Smyth Performance G3F Build - GO GREEN, GO FAST
http://3.bp.blogspot.com/-NumcSVOAz8...NosePic900.jpg

The trendy Porsche GT3 style openings at the lower front corners (dual split radiators) makes me think it's something fairly current.

The Trev is cute, I like it. However, they stopped short of their full potential - tail wise.

http://s184.photobucket.com/albums/x...%20and%20Ends/
http://i184.photobucket.com/albums/x...sc_2007_03.jpg

I modified one of their images found here:
http://w3.unisa.edu.au/solarcar/imag...ve/default.asp

More images of car here;
http://www.nvntrs.com/mpg-trikes.htm

My latest mark-up:
http://i184.photobucket.com/albums/x...k-up-daa01.jpg

I still would not dare to guess the Cd, it's just such an unusual vehicle.

Your car is much like the Ale' - both are even Honda powered.
I think the flanks on the Ale' might give some inspiration :

http://www.carsbase.com/photo/Fuel_V..._pic_43965.jpg

BTW, I like your version much better.

thanks Cd - I did look long and hard at the Ale, and it has some great features.

I chose to have doors and windows which roll up and down so some things obviously are different.

I'll get some more pics today.

Somehow I missed the similarities with the FVT eVaro (formerly know as the Alé). It has a hinged canopy that has a "fat" portion:

http://www.futurevehicletechnologies...l_p3200970.jpg
http://www.switchimage.org/phlog/Ima...og_Evaro-8.jpg

Another X-Prize vehicle that is even closer to the the layout of your trike is the Zap Alias:
http://zapalias.files.wordpress.com/...ay-samyang.jpg
http://www.instablogsimages.com/imag...3_jrKhy_69.jpg

The "Zap" is an excellent compariable.

I think the following can also be lumped in there with Doug Miller's design. If we can find the Cd's of these cars, maybe we can make an educated guess about Doug's Cd.

Razor...........lots of turbulence coming off those front wheels.
Razor at stoneleigh...
http://thumbsnap.com/s/AW4yDuW2.jpg

I know this has four wheels, and is open on the sides and top, but mass wise it's in the same ballpark, and lot of drag coming off those wheel flares.
Kit Cars [group] most recent on FlickeFlu
http://farm9.static.flickr.com/8008/...03d205cb9d.jpg

Drag off the front wheels seems to be a part of most traditional 3-wheel trikes.

EDIT: According to this the Edision-2 had a coefficient of drag of 0.16

X Prize Winners Look Weird ... With Good Reason | Autopia | Wired.com

I read elsewhere, that the Zap World car made the top five finalist. So how bad could their aerodynamics possibly be? An exposed rear wheel, and drag inducing front wheel farings not too dissimilar to Doug's, I'd say he might be better off than we first thought.

I'm thinking the Cd would be on the order of 0.4. But the small frontal area will make up for quite a bit.

No specific reasons, but I see lots of places for vortexes to form and for flow to be disrupted.

I would think that overall drag would be quite good, but more because frontal area is very low than because of a low Cd.

-soD

I'm taking the other side of the fence with the Cd values, The only thing in the wind is the front end. The middle and rear end are traveling behind a wind block, the amount of drag induced by that end will be next to non existent,it takes advantage of the otherwise wasteful large wake.

My car has a 0.38 Cd so my guesstimate is it has to be more then 1/3 less drag then my beetle, more like 1/2 so the Cd is about 19.

I'm going to guess that the Cd will be between .10 - .50 .
http://s3.amazonaws.com/coolproducti...jpg?1327728745

All joking aside, I don't think we have enough data to make an educated guess.
I agree that there is most certainly going to be major turbulence just behind the front fender.

Is this a running vehicle capable of doing a tuft test ?

Hood.

http://www.globalmotors.net/wp-conte...al-concept.jpg

As far as the low pressure zone is concerned, have you considered doing a "soft" body panel that would flex as you open the door and stay taut when it's closed? The BMW GINA used this to great effect, if you're not familiar.

http://37signals.com/svn/images/bmw-doors.png

Yours wouldn't have to be as complicated as that but I could see using a few strategic structural lines covered in some sort of treated canvas (like old airplanes) to create a "good-enough" body surface that anchors on the Civic door. This would do what Skyking was talking about, but would not interfere with ingress/egress.

Now, it's not going to be a quick project, but I think if you gave it some time and played around a little it could be pretty cool, and work well too.

Please don't reply to this with a sarcastic remark or personal attack. I'm just trying to help. Thanks.

When you get everything sorted you could do some coast down testing and let us know how it comes out- if we weren't interested we wouldn't be posting here :)

I was thinking along the lines of a lightweight panel that clipped onto that current door, and radiused up front so it turned inside a projection off the back edge of the fender. It would have a minimal gap when closed. No moving parts and very light. I'd have to see the "door open" picture to see what I'd be working with. In the mean time, go test it and have some fun, and tape some coro on there later and do an ABA test and see if it was worthwhile.
EDIT: I looked at the pics some more. My idea would also be an ideal shelf for a beverage during REALLY slow speed testing :D

There are several track type cars covered in spandex, something like this might work here.

You could manually pop it out and then as the door opened the panel could hinge forward like a La-z-boy footrest. It would just need two simple brackets.

There are a few options on the table here, so Miller, do what you like.

I like it Cd, that just might work.

Thanks guys! Some great ideas!

in particular, the "soft" wing is making me think pretty hard about that!

The idea of Cd's looks good, but in the real world doesn't really work out. When you look at it IRL, the sizes just don't work, and building that thing onto the door is beyond my skills.

Good catch on the 'vette. Interesting no one else has commented.

FWIW, the fenders are about 10 inches wider then the doors. and about 20 inches tall, or about 3 square feet total between the two. I still think if I make half of them grills, they are not going to hurt that much.

Actually guys, Skyking had the same idea but posted first.
I'm a complete moron.

I'll try an see if I can make something like this work using a model car before posting anything here.

I wonder if there would be an advantage to breaking up the nodes or mass flow there. Something like a series of ripples of more than one plane or a hump like the Alpine below.

RENAULT ALPINE A110-50 CONCEPT | Hidden Garments
http://www.hiddengarments.cn/wp-cont...ncept-2012.jpg

2008 Mazda Furai Concept Images. Wallpaper Photo: mazda_Furai-Concept_2008-030-1024.jpg Wallpaper
http://files.conceptcarz.com/img/Maz...08-030-800.jpg

Doug, I for one didn't recognize the new Vette nose, because I simply haven't seen it before. I just found an article on-line dated a year ago, and all the pictures said they were artist renderings (looked like photos to me). I'd be interested in hearing the story describing how you came about such an item.

2014 Chevrolet Corvette (C7) To Offer Better Feedback And Quality From New Platform

Maybe I did see this car in a magazine at the barber shop a while ago. I seem to recall the rear but not the front for some reason.