Gen 3 Prius See Through Boat tail Idea

[Angel And The Wolf]

I used the template, both vertically and horizontally to draw an aerodynamic boat tail.

The floor, end piece, and front is plywood, and the sides and top are clear plexiglas pulled into curves that match the template.

The floor is bolted to a trailer hitch ball mount, and the plexiglas is built on the plywood pieces.

I also plan a plexiglas piece that would stretch from the top of the rear hatch window to lay on the flip up part of the spoiler, thus allowing the air to flow without the flip at the rear. I doubt I will be driving at a speed where I might need a spoiler.

The boat tail will reduce the vertical area to about 144 square inches, 6" high X 24" long.

[Angel And The Wolf]

Well, I have drawings, but I seem to have misplaced the attachments button.

[Angel And The Wolf]

OK, here are the drawings:

[Angel And The Wolf]

I worry a bit about the necessarily high angle of the plywood floor, that it may produce such a reverse lift that the front of the car becomes lighter.

I hate to use anything to direct the air toward the floor that would increase drag. Maybe a second floor skin hinged at the front of the tail that could be drawn downward by the lower pressure?

[Angel And The Wolf]

Or, maybe just a spring loaded second floor, without the end or side pieces. At slow speeds, where you would be enter driveways, the second floor would be held up against the real floor by the spring loaded hinges, but at higher speed, where reverse lift would be produced under the boat tail, the second floor is drawn down by the lower pressure, and keeps the lower pressure off the real floor.

Would this work?

[Angel And The Wolf]

Or, maybe I should leave the sides on the second door to keep down spill over?

[freebeard]

I'm no fan of The Template, but get some other opinion on whether you have applied it correctly. The top view Template[s] are complete, but the side view is butchered. The ground plane and departure angle have been deleted. What you have is suitable for off-road rock crawling. IMHO it should also slide forward to match the contour at the roof.

I know you're fixated on reducing down to the height, if not width of a license plate. You're compromising a lot to get there.

[Angel And The Wolf]

Originally Posted by freebeard

the side view is butchered. IMHO it should also slide forward to match the contour at the roof.

Beard, I used the portion of the profile from the highest point (widest point when laid horizontally) because I didn't want to cut off part of the rear fenders to match the profile. Nor did I want to add width to reach the profile. Yes, that would be more tear drop, but I'm giving up the profile forward of the rear corners of the car, and using it from that point back.I can post the unbutchered profile on the top view: (You know, I think you may be right!) Thanks!

[freebeard]

Just trying to help. People apply the template to everything. The thing is the back 70% depends on the airflow set up by the forward 30%. You can't just tack it onto the back of some arbitrary form. Mair starts with an extended body (fineness ratio is your friend) with a circular cross-section. There is (somewhere) some middle ground, hence the wind tunnel rules over theory.



I like the Tropfenwagen, it's shaped like a submarine conning tower. I tried combining several aero-forms into one:



This would need serious filleting and tweaking, but could accommodate specific internal space requirements.

You could lose all the [upper] taper and optimize the sides. Here's a study of putting a back window like the 1948 Studebaker Starlight coupe on a Beetle:

[BamZipPow]

Originally Posted by Angel And The Wolf

Or, maybe just a spring loaded second floor, without the end or side pieces. At slow speeds, where you would be enter driveways, the second floor would be held up against the real floor by the spring loaded hinges, but at higher speed, where reverse lift would be produced under the boat tail, the second floor is drawn down by the lower pressure, and keeps the lower pressure off the real floor.

Would this work?

When I was building my diffuser fer the first iteration, I had single bungee cords holding it up. At speed, I got banging from the diffuser gitting sucked down, the air stalling, and then from the lack of suction/negative air pressure, the diffuser would retract back. This would repeat until I slowed down where the bungee cords were able to keep the diffuser in place. I would expect yer design to be similar and would probably function in the same way.

If you do go in the direction of a retractable floor, look at the rear door of the P-51 Mustang.


As far as yer choice in materials, you might want to look at Coroplast and aluminum angle to build out the floor pan with instead of plywood. Waterproof and there isn't a propensity to degrade with inclement weather. It will be lighter and more durable than plywood. It will last longer and be easier to work with and install.

I'm not sure you would want the upper part to be plexiglass as the suggested angle you have would make it rather difficult to see out of especially as the thickness increases.