First Electric van boat tail

[aerohead]

Originally Posted by JohnForde

Black HDPE in 1st pic has been replaced by tightly fit white coroplast.

Can't figure out why I get no improvement.

Is it leaking?
Is it the cuff?
Thoughts anyone?

More pics on request.

Thanks
John Forde

John, in the far left image it looks like there are 'pie-piece' gaps at the tail end of the plywood. If so, these openings are immediately adjacent to 'tornados', of extremely-low core pressure.
Should this low pressure be able to 'telegraph' to the 'inside' of the tail cavity, it would be capable of 'diluting' any pressure rise that the top, sides, and bottom were accomplishing.

[JohnForde]

https://photos.app.goo.gl/86RCfm28p19bRuqA9

[freebeard]

Thanks for the tip Freebeard. I think the question before me is not how to do the most efficient tail but rather the most efficient way to get some measurable performance from my current tail. If leaking is suspected a second seal at the rear might be very practical.

wiki.dtonline.org/images/thumb/c/c6/Transformer2.png/1000px-Transformer2.png

Cut your plywood to trapezoidal shape and add rigid curved transition pieces. Closer to a circular termination is better.

[JohnForde]

I think Aerohead may be right. about vortices down low. In the third pic the yarn in the yellow circle is angled downward at the rear corner.

I am pleased that the Zevo seems to have attached flow.

The second pic shows the "pie tabs". Should I cut them off?

The first pic shows my next attempt at a foam floor. I also think doing the back all will give a truer result and create a surface for me to pressure test,

Freebeard I love the round termination but I need the doors to fold for charging.

Next I will mount the pitot tube and hook up the manometer.

[Piwoslaw]

Originally Posted by JohnForde

https://photos.app.goo.gl/86RCfm28p19bRuqA9

Great that you were able to tuft test! It clears a few things up.

For example, seeing that the flow seems attached everywhere except behind the wheels, so maybe rear wheel skirts would help?

[JohnForde]

Originally Posted by aerohead

John, in the far left image it looks like there are 'pie-piece' gaps at the tail end of the plywood. If so, these openings are immediately adjacent to 'tornados', of extremely-low core pressure.
Should this low pressure be able to 'telegraph' to the 'inside' of the tail cavity, it would be capable of 'diluting' any pressure rise that the top, sides, and bottom were accomplishing.

My plan is to eliminate the pie piece by lowering the floor. (Cheap temporary foam)

Should I trim up the sides as in this photo?

[freebeard]

I'd say the opposite curve.

[JohnForde]

Originally Posted by freebeard

I'd say the opposite curve.

I'd have to add wood. Straight good enough?

[ennored]

Tufts do look very nice (to my untrained eye - just making sure no one thinks I'm some sort of expert). Some disturbance around the edges, top and bottom, but that's to be expected, air will spill over. NASA folks got great numbers with their Dryden van with a boxy looking tail, seems like what you've done should be working, but you know that.

On the "working" part. Have you ever cross checked the numbers your dash is displaying? I know there's quite a bit of software between the raw data and what you see on the dash. Sure seems like it'd be working, just like when you are driving with a big tailwind, but maybe there's some fudging going on to not predict a range that the production truck couldn't really do? You can find all kinds of folks saying their dash MPG numbers lie to them. Same thing may be happening here. Under-promise and over-deliver, right?

[JohnForde]

I think Aerohead is correct that my Zevos aero drag is down low, lower than the floor. I am making a major revision, lowering the WT's floor and eliminating "pie tabs". I will test soon.

I believe the Zevo's gauges on the dash are very accurate. Instantaneous kW is most important. @ 63 mph it is ideally 34-35 kW. I hope to drop it under 30.
Total kWh used on the drive divided by odometer, I believe is very accurate.


Thanks for your confidence in me.