Inflatable boattail

[Bicycle Bob]

Originally Posted by dremd

OH wow, new years noise maker is a great idea!
What is that made out of, spring steel?
I had folding plywood on the mind.

Yes, the spring is a length of thin piano wire, carefully enclosed in a a fold of the paper.

Upon reflection, I think that while an inflatable shape does offer the possibility of being retracted for parking, we usually have enough space for a 20' long car anyway, so for most people, folding will be more bother than it is worth. The inflatable raft has morphed into the RIB, which is not usually deflated even when on the highway.

[slopemeno]

Why not just make it unlatch at the bottoms of both the nose and tail, and flip them up onto the hood and deck lid? No deflating required.

[dremd]

for me the retractable nature is more to be removable, low modification to existing vehicle, and cool factor.

For those that don't know me I love things that have a "wow", "gee Whiz" or "man that's cool" factor.

[Bicycle Bob]

Originally Posted by slopemeno

Why not just make it unlatch at the bottoms of both the nose and tail, and flip them up onto the hood and deck lid? No deflating required.

That would work. I hope the parking ticket people don't mind. Front extensions tend to be short and low, so rigid is probably OK there, usually. On the inflatable-back one, maybe a solid belly pan would hinge up for parking only. If there is a blower used for inflation, it can be used for suction to collapse things neatly too. Otherwise, a few internal shock cords, etc may suffice. My buddy reminds me that folding is more important on large vehicles.

BTW, the original Mini could have been a hatchback, but Alec opted for a tailgate which could be piled with lashed-on gear, while the license plate automatically swung down underneath.

[Piwoslaw]

Originally Posted by dremd

And a final thought, wouldn't it be great if it could be collapsed entirely just by sucking the air out? How about using the tension from the top to hold the boat tail from hitting the ground, then having tent poles (or plywood)hinged in 2 (folding so the "V" is inverted) collapse in such a manner that the entire assembly sits between the bumper and the back window?

I see it like this: The inflatable boattail would be made up of 3-5 "layers", extending horizontally from the back. You start by inflating the largest one, closest to the car. The rest of the layers are deflated and snuggled inside the first one. When you speed up you inflate the next one, slightly smaller, and so on, until at cruising speed the very tip is inflated. This lets you have drag reduction before total inflation. The hinged inverted "V" (lambda) would stick up and out while folding.

Another idea is that the boattail is in segments, like descibed above, only they're not inflatable, but stiff and they retract one into the other like a telescope. The first segment is a kammback, the others fit inside of it. This reminds me of a collapsible cup:

[mikel09]

We have taken the boat tail design and integrated it with a durable cargo carrying structure. It is dual function: to carry soft gear increasing cargo capacity and improving rear air flow with the boat tail taper. Our initial tests on a station wagon improved mpg by ~10%, while carrying soft gear. It is patent pending, AeroPACKusa .

It attaches to a lift gate or hatch back. Conceptually one could carry soft gear or use lightweight inflatable spheres (beach balls) inside the structure to achieve the mpg improvement.

Hope this helps.

[aerohead]

Originally Posted by Bicycle Bob

I have considerable experience with inflatable displays, and they always are assumed to leak and require a continuous air supply. Some idea of the possibilities can be found in the hot-air balloon contests. Given a chance, an inflated structure will look as much like a bubble as possible. Cones are easy to produce, but cubes are hard. For a flat panel such as a fastback rear window, some extra structure is needed. Ribs can be added by using separate small-diameter tubes inflated to fairly high pressure. The nicest realization of this is made with two tailored layers separated by deep ribs, much as a really high-quality down sleeping bag is made.

I would favour a lower structure that would curl up like a New-Year's noisemaker to stow the whole inflatable tail in a neat roll at the bumper. It might be necessary to mount the taillights and licence plate on tubes that telescope from the belly pan or roof, and follow the tail in and out.

The German design is much like what you describe.It is shown in Hucho's text on the back of a passenger bus.I don't know if Klemperer or Fachsenfeld,or Jaray came up with it but it's the best form I've seen yet.

[Piwoslaw]

Crossposting:

Originally Posted by todayican

I wanted to do a boat tail, but it would have to be like 80" to come to a full point, I had the idea to make it collapsible! something like one of those old fashioned "travel cups" that telescope out from the base.

Like this: Prius Tv with Tom Bell

The tag and "alternate directionals / reverse light / brake lights will go in the tip section which will be clear, the "stock color" will be faux carbon fiber.

It will add about 15" to the car in total length retracted, so it will be easy to get around town and park etc, and once on the highway, flip a switch and a combination of air venting in from a movable vent and a telescopic mast (like an old power antennae) will deploy it to its full length.

Flip the switch the other way and it gets "reeled in" shouldn't take more then 15 seconds either direction.

I am seriously shooting for a kit that can take the Prius C to 100mpg at 65mph, with no mechanical mods, re-chipping or lowering.

[SiVX]

Originally Posted by AndrewJ

Heck, all you really need is an inflatable "bed" mattress and a big jar of contact-adhesive.
Get one of the inflatable beds with a built-in pump (that inflates and deflates) and cut up the mattress to make your boattail. There's plenty of material there to work with, and its rubber, so it'll glue up with contact cement wonderfully. And for tips on how to properly glue up rubber with contact cement, just watch the Mythbusters episode where they escape from Alcatraz on their homemade inflatable raft.

That sounds like a good idea. If we could make it removable i'd praly give it a shot!

[aerohead]

Here are some recent scans: