Tuft Testing on Insight Hatch Glass (2006 Honda Insight, 1st gen.)

[HAHA]

What were the wind conditions during the test? (crosswind?)

[California98Civic]

Originally Posted by jimepting

Just as a guess, one might raise the hatch lid a couple of inches and achieve better aero. In a couple of weeks I'll probably give that a try. All comments very welcome

Isn't there a "lip" at the end of the hatch? Wouldn't raising the hatch change the angle of the lip and possibly cancel-out benefits by adding downforce and turbulence at the trailing edge?

[jime57]

Originally Posted by HAHA

What were the wind conditions during the test? (crosswind?)

Look completely calm from the leaves on the trees.

[jime57]

Originally Posted by California98Civic

Isn't there a "lip" at the end of the hatch? Wouldn't raising the hatch change the angle of the lip and possibly cancel-out benefits by adding downforce and turbulence at the trailing edge?

Yes, there is a small lip, but near as I can tell, it is at same angle as hatch. I don't "think" it would impact testing. It is largely a trim item. Honda may have added it to protect the rear edge of the glass. Just guessing as to purpose. Thanks for the comment.

[jime57]

Originally Posted by HighMPG

Looks good! I just ordered my GoPro Motorsports so I'll be able to get some vids later on.
Planning on a boat tail?

I have one of those that I use in my racing Miata. Problem I had with it in the current test was that the lens does not have a wide enough field of view. I though hard about using it, since the files would have been much smaller. The GoPro is very small, so I intend to use for some outside applications, sorta like Darin's "webcam on a stick."

[MetroMPG]

Originally Posted by jimepting

It seems to me that the turbulence is very slight.

I agree. It definitely doesn't hint at separation, which would have the tufts swirling, and ultimately flowing "backwards" up the glass at times.

One other thing I want to do is put tufts somewhere where I know the flow to be extremely good, like middle of the hood, and see how those look.

You can see what tufts in very clean flow look like in this video I did. Jump ahead to about the 2:40 mark - particularly note the tufts that are furthest forward and on the top row:

www.youtube.com/watch?v=Lo3EEHDoUgc

I was amazed that the turbulence did not get worse further back on the hatch. I had been conditioned to think that flow deteriorated as one got closer to the rear edge.

It does if the shape isn't optimal

All very interesting. Seems Honda got it pretty much right.

Seems that way.

[jime57]

yep, that is about what I expected. The front can be very smooth, before any edges or misshapen parts get in the way. The front fender skirts have a very impressive result.

But, the question is, how do we translate something like fender skirts into an estimate of lowered Cd. Guess, less wind tunnels, we only have A-B-A MPG testing and rolldown testing, both rather imperfect for small changes.

[MetroMPG]

To be honest, I'm less interested in trying to calculate actual Cd than I am in finding differences in coast-down times or MPG readings.

[aerohead]

Originally Posted by jimepting

OK. It seems to be up and working.

My take is this:
1. The middle row and the bottom row tufts all indicate attached flow, but slightly turbulent.
2. The top row tufts are more turbulent and I think that this is caused by the the airstream "tripping" slightly on the rather large open seam between the hatch and the roof.
3. Honda pushed the very limit with the hatch angle. They probably figured and optimum compromise between aerodynamics, length, and rear visibility.

Just as a guess, one might raise the hatch lid a couple of inches and achieve better aero. In a couple of weeks I'll probably give that a try. All comments very welcome

I'm late to the party ( happens quite often).Just watched the video (an amazing tool!).
The flow looks okay.A bit nervous,but no reverse circulation,so the appraisal that Honda got it right on the ragged edge is confirmed.
On my last trip I tufted the hood blister near the windshield.Those behaved as if they were painted on.They didn't move at all except when encountering gusts or bow,stern waves off big trucks.
The top of the trailer was a bit nervous as was expected,as there was a significant gap remaining.
The lower sides which I could see from the mirrors were VERY nervous,although no recirculation visible.They remain the 'dirtiest' location until completed.
It will be interesting to see the 'raised-hatch' results,and if some of the quaking diminishes.
Nice work HONDA!
Nice tuft-testing Jim,and thanks to Darin and all which made all this happen.
I may lean on all of you as I attempt this same sort of thing.I've got a 7-meg camera with a short video capability.And friends have volunteered to do the chase car driving and videography when the time comes.Again,thanks Mucho!

[jime57]

Originally Posted by aerohead

Nice work HONDA!
Nice tuft-testing Jim,and thanks to Darin and all which made all this happen.
I may lean on all of you as I attempt this same sort of thing.I've got a 7-meg camera with a short video capability.And friends have volunteered to do the chase car driving and videography when the time comes.Again,thanks Mucho!

I second the thanks to Darin. We have a wonderful site, largely through his hard work!

When you start making videos with that 7-meg camera, set the resolution as low as your can, and keep the segments to an absolute minimum length. Otherwise it takes forever to get it uploaded to youtube. Powerful tool, but needs some discipline