sepp's second aerocap

[sepp]

thank you all, i was especially hoping for tips from aerohead. i think i will go for the polyester edges.

i thought long about giving it an airbrake, and maybe i will but not with these flaps. as i believe that if these are used to brake a 2 ton vehicle, that it will make the whole thing disintegrate.
i searched a bit but i could only find some actuators on some auction sites wich go from 26 to 160 €. i will leave that for the last and keep searching for a good find.

also does anyone know if some sort of spoiler would help? i was thinking of some kind of horizontal wing above the rear end. or is it better to let the cap end with a horizontal part that is in the shape of the cap like most car truncs or roofs end with.

[Frank Lee]

While I appreciate the thought going into the flaps, it violates the K.I.S.S. principle: Keep It Simple, Stupid (no offense!).

I don't know what sort of traffic conditions you have to deal with, but especially if I'm in busy multi-lane conditions, I want to be able to glance around at any time, with no notice, without reaching for a button or something.

I'm recalling the PNGV cars and how Chrysler's version had a more vertical visibility panel. It appears to me the flow is designed to skip over the rear window and reattach on the decklid. The car had impressively low Cd; right in there with the Ford and GM models, so that break in the flow must not have had negative effects on drag.



Also I wonder why you are proceeding on Version II before knowing how Version I actually performs, i.e. "I wonder if the angle is too steep and flow is separating". A yarn test on VI would answer that.

Lastly, there is no gaslog data for us to peruse. There is no way of telling how effective this device is for improving fe at all.

Anyhoo, feel free to proceed and let us know how it works out.

[elhigh]

For operating your flaps, what's wrong with some power window actuators? A lot of the hardware you need is right there.

[COcyclist]

I have been toying with building one of these for my little pickup. For visibility straight out the back, you don't need a plexiglass as big as the back glass in the truck. In pickups the glass is closer to the back of the driver's head. You aren't even using the glass down by the driver's shoulders to see behind you out on the highway. There just needs to be a window a little larger than, and in line with the rearview mirror. I would suggest mounting the framework on the truck and take it out on the highway to see how small of vertical plexiglass you would actually need. A little scallop like Aerohead's should be fine. Some bicyclists use a little mirror the size of a postage stamp on their glasses and it works because it is close to the eye.

[Jetta90GL]

I also think power window motors would work nice. I have a set I pulled out of the junk yard from a mustang that I plan on using for some aero projects.
To control the motor I would use a limit switch set up similar to what is used in overhead doors and electric gates. That way you can "set it and forget it" by using micro switches built into the mechanism. One limit switch would be for the "full open" end point and the other would be the "fully closed" end point. When you turn your toggle switch in the cab to "open" the motor would run until it bumped into the "fully open" limit switch and shut its self off.

[wagonman76]

Great job. I love it!

[sepp]

Originally Posted by Frank Lee

While I appreciate the thought going into the flaps, it violates the K.I.S.S. principle: Keep It Simple, Stupid (no offense!).

...

that principle probably works for most, but has a negative effect on me
if i want to make something valable, then i need to start with the most complex and perfect idea possible, because out of habit i know that along the construction i will always leave stuff out out of lazyness. like only making 3 instead of 4 beams, or like i already did here make 2 flaps instead of the 3 i planned.
those little vertical windows are a nice idea, they come to late unfortunately.
im making a second cap because of a suspicion that possibly the angle was bad, but mostly because it was just not practical and was just too heavy wich are just facts.
i probabaly won't use the flaps when driving in known areas, and leave them open when driving in unknown areas because i get stressed quickly. they may also be used as a "get off my back" feature to let those annoying people know that i don't like when they drive so damn close that they disappear in all 3 mirrors. will probably be safer than my current "scare the f* out of them" techique wich consists in slamming on the brakes

the window actuator idea is a great idea, only need to find some. can't even ripp them out of my pickup as i have manual windows (out of ecologic principles i swear! )

today im gonna put on some alumium plates, but first work off the frame and paint it.

[PaleMelanesian]

Why not use a throttle or choke cable and have a manual lever-operated mechanism? KISS again.

[MazdaMatt]

That's a very nicely built cap. Good job.

If we're talking about keeping it simple, why the hell does the thing have flaps? Cover your hinged part with plexy and you're done. No screwing around with motors, leavers, ropes and pullies or monkeys on treadmills. It will the easiest and lightest possible option to maintain visibility.

Good luck and congrats on your work so far

[wagonman76]

as transparent plexiglass wouldn't let you see through at such an angle.

I've never tried looking through plexiglass at much of an angle, so I will take your word for it. I will have to keep that in mind for my kammback/boattail too.

I would agree with keeping it simple, and I would rather have visibility all the time without having to think about it. If you can't see through plexiglass, then how about fitting in a used windshield from say a 90-96 Lumina APV van, or something similar?