First Electric van boat tail

[JohnForde]

UPDATE: The structure is done to 4' behind the rear bumper. Top and sides are all 11-12 degrees. Floor is foam and close to air tight.

I plan on adding tail lights and going 2 more feet in the next couple of days. Yesterday was too windy to test. I am heading out in an hour for a 60 mile test.

JSH suggested the VGs may be hurting. I removed one easily. I may remove them all.

I still need to improve the upper corners. Then add the 24" of twin wall polycarbonate to the tail. Should happen in the next 2 days.

[Piotrsko]

Seems a shame to have this extra length and not be able to use it. Any plans on making it functional?

[aerohead]

Originally Posted by freebeard

I do not think that percentage means what you think it does (that's three orders of magnitude). Or maybe it's the conjunction [by] vs [to].

I'd say to 125%. The case of a Porsche ducktail is different to a box van.

Remember your Morelli's 'Fluid Tail' thread?


Blown rear wheelwells FTW.

1) I made my best WAG, applied the 'expert's' project estimation correction factor, which put the curved panel man-hours at over 900%, compared to 'straight.'
2) Since most members who visit this forum are math-averse, I just rounded-up to 1,000 %, so as not to confuse, and scare people off.
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3) I read your 125% thesis. I've been 'constructing' since kindergarten. I'm very interested in fabrication. I pay attention to 'approaches.' I've never observed, heard about, or read about anyone ever 'doing' what you've proposed, so I'm not aware that there's any efficacy to your technique. Perhaps they sell types of plywood in the Pacific Northwest that I've never experienced.
4) I'll stick to my 1,000% estimate.
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5) As to the 'Duckbill' spoiler, it is exactly germane to the ZEVO boat tail, since this always has to do with boundary-layer theory. All 'aerodynamics' revolves around it.
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6) What is it that I want to think about in relation to Morelli's 'fluid tail' ? It has no bearing on what John is willing to do on the ZEVO.

[JohnForde]

Originally Posted by Piotrsko

Seems a shame to have this extra length and not be able to use it. Any plans on making it functional?

Functional as in storage? Weight is a major consideration. I already have 2 e-bikes inside. Maybe next year I will consider how to install a strong floor, but it also needs to be able to retract to get at level 3 chargers with 72" cords.

Current design functions great as a veranda with the 60"W roll up door open - sun & rain shelter. Down the road I will considering splaying it wider

[JohnForde]

Plan for last 24".


The 'wake area' width has been reduced from 84" to 48"

Including the top the recovered attached flow should now be just about 50%, at least above the bumper.

[aerohead]

Originally Posted by JohnForde

UPDATE: The structure is done to 4' behind the rear bumper. Top and sides are all 11-12 degrees. Floor is foam and close to air tight.

I plan on adding tail lights and going 2 more feet in the next couple of days. Yesterday was too windy to test. I am heading out in an hour for a 60 mile test.

JSH suggested the VGs may be hurting. I removed one easily. I may remove them all.

I still need to improve the upper corners. Then add the 24" of twin wall polycarbonate to the tail. Should happen in the next 2 days.

1) Pressure drag reduction is what's in the cross-hairs.
2) It depends on base pressure.
3) The base pressure is dependent upon the static pressure which exists at the separation line.
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4) VGs 'lower pressure'.
5) Without the whale tail, the VGs would essentially be 'right at' the separation line. And lowering pressure 'there' would be antithetical to drag reduction.
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6) With the VGs in place, they might act as an 'insurance policy' as far as flow attachment 'down' the whale tail is concerned. Since they're already in place, you might consider leaving them, at least until you make at least one test run, giving you 'data' for future comparison.
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7) If the 24-inch extension causes the 'floor' to end right where the side panel's lower 'angled' intersection is, that would be great, taking maximum advantage of available pressure recovery.
Travel safe. Have fun!

[JohnForde]

Originally Posted by aerohead

1) Pressure drag reduction is what's in the cross-hairs.
2) It depends on base pressure.
3) The base pressure is dependent upon the static pressure which exists at the separation line.
-------------------------------------------------------------------------------------
4) VGs 'lower pressure'.
5) Without the whale tail, the VGs would essentially be 'right at' the separation line. And lowering pressure 'there' would be antithetical to drag reduction.
--------------------------------------------------------------------------------------
6) With the VGs in place, they might act as an 'insurance policy' as far as flow attachment 'down' the whale tail is concerned. Since they're already in place, you might consider leaving them, at least until you make at least one test run, giving you 'data' for future comparison.
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7) If the 24-inch extension causes the 'floor' to end right where the side panel's lower 'angled' intersection is, that would be great, taking maximum advantage of available pressure recovery.
Travel safe. Have fun!

Thanks Aerohead! I was hoping you would weigh in this morning. I will leave the VGs for now.

Are you saying the 24" extension should not have a floor? That would be easier although I do have a plan to install a large piece of coroplast as the floor from 48" - 72".

[aerohead]

Originally Posted by JohnForde

Thanks Aerohead! I was hoping you would weigh in this morning. I will leave the VGs for now.

Are you saying the 24" extension should not have a floor? That would be easier although I do have a plan to install a large piece of coroplast as the floor from 48" - 72".

Presently, from your photos, the trailing edge of the floor is about 6-inches above the 'upper' edge 'corner' of the side panels, where the 'vertical' edge meets the 'angled' edge.
To take full advantage of the side panel pressure recovery, you'd want the floor to match that 'corner.'
It looks like, when you've added the extra 2-feet of side panel, that if you extend the existing 'floor', it 'WILL' intercept that new 'corner.'
That would be 'optimum.'

[JohnForde]

Originally Posted by aerohead

Presently, from your photos, the trailing edge of the floor is about 6-inches above the 'upper' edge 'corner' of the side panels, where the 'vertical' edge meets the 'angled' edge.
To take full advantage of the side panel pressure recovery, you'd want the floor to match that 'corner.'
It looks like, when you've added the extra 2-feet of side panel, that if you extend the existing 'floor', it 'WILL' intercept that new 'corner.'
That would be 'optimum.'

Thanks Aerohead! THAT'S THE PLAN!

[freebeard]

Skegs and fences?

How's the departure angle?