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bennelson 02-02-2008 07:57 AM

Inflatable boattail
I just found an article on semi-truck aerodynamics located here.

Scroll down a bit and it mentions the concept of an INFLATABLE BOAT-TAIL.

Why not? I have seen giant inflatable movie projection screens and even heard of an inflatable car.

An inflated boat tail sure would be light.

Who wants to be the first to make one of these things!?

aerohead 02-02-2008 05:11 PM

Inflated boattail worked on T-100
Back in the 90s I did a inflatable boattail for the T-100 ,when it was John Gilkison's.We took it on a camping trip near the Very Large Array,in New Mexico,and did a roundabout long way home,just to get more miles.For about 600 miles of driving,the inflated tail gave over 30-mpg.We were quite pleased with the performance.It was constructed of sewn naughahyde,tailored over patterns drawn for a 12-degree convergence angle (top and sides),stapled to an airtight box constructed to fit the tailgate region of the truck.A 12-VDC heater fan out of a Volkswagen Westfalia camper van provided the inflation pressure,which was powered through a simple electrical umbilical cord, alligator-clamped onto the truck's battery,and strung underneath the truck to the rear.A larger unit would no doubt help a 18-wheeler,although thats outside the scope of what I can take on.A fellow in Lubbock,Texas has a U.S.Patent on such a device for 18-wheelers.I've seen photographs of it.He has a lot to learn about aerodynamics,and could look to the German designs of the 1920s,where the concept originated.Hucho's book,"Aerodynamics of Road Vehicles",published by Butterworth's has a beautiful image of an ideal design.

Gone4 02-02-2008 08:46 PM

It would be neat to inflate for highway travel and deflate ot park in the cities, too.

buckyball 02-04-2008 09:44 PM

Nuts. And here I thought I'd come up with a Great Idea (tm).

I've been noodling on this for a couple of weeks since I read the thesis from the guy at the Naval Post-Graduate School. There was a picture in there about research NASA did in the 80's (IIRC) on the optimal shape for a large truck/bus design.

A sloped bedcap + an inflatable boattail would be great for my monster F-350. When the weather improves, I plan to have another go at grille block mods, as the bed cap is a larger project and/or expense.

mattW 02-04-2008 10:29 PM

Plus in a rear collision you would be in the privileged position of having air bags outside your car! It would good to have one with a semi rigid bottom section that allowed the tail to curl upwards as it deflated into the pick up bed. I'm imagining two hollow tubes on top of each other with a cord or strap through the middle of each of them (sort of like those poles in modern tents). By pulling the top string as the tail deflated you could have it curl up like a monkey's tail rather than sagging down to the ground. Then you might have the possibility of doing while driving as you entered the city and needed a shorter length. I am considering buying an inflatable kiddies pool or large beach ball to carry out some experiments hehehe.

bennelson 02-04-2008 11:12 PM

A shop vac is a great way to inflate anything.

I made the mistake once of inflating a queen-size airmattress in my livingroom with the shop vac. Took about a second and a half. Almost smashed a couple of lamps with the mattress.

Shop vacs can also be setup to suck or blow - so you could inflate or deflate your boattail.

Frederick 02-05-2008 08:29 AM

How about using the exhaust to inflate it? After all an engine is an air pump. Many moons ago, in design school we "invented" a low cost shelter . Take an igloo shaped "balloon", blow it up with exhaust, keep inflated and spray water on it in fine droplets. In sub zero weather. You can tint the water with food coloring. Spray till you have a 1 -2 inch thickness of ice. Pull out deflated igloo and enjoy.
I was looking for a low cost shelter for the ice fishermen here on the Richelieu river, then I proposed the idea to the national capital Commission in Ottawa. We have after all the world's longest skating rink, 7 miles of it, and a few of these shelters could be enjoyed. At night a candle light placed inside would transform them in giant lanterns. Anyway, I used the exhaust from the water pump to inflate....I got off track....

bennelson 02-05-2008 09:49 AM

Years ago, I saw an infomercial for a car jack that was just a big plastic bag you stick under your car, then use your exhaust pipe to inflate it.

I wouldn't trust that to hold up my car, but might work great for inflatable aeromods.

Frederick 02-05-2008 10:01 AM

I saw that one too. Very rugged. Made in England, second world war technology. Same stuff as the curtains around a hovercraft.

bestmapman 02-05-2008 10:55 AM


Originally Posted by bennelson (Post 8304)
Years ago, I saw an infomercial for a car jack that was just a big plastic bag you stick under your car, then use your exhaust pipe to inflate it.

I wouldn't trust that to hold up my car, but might work great for inflatable aeromods.

I had one of those. It worked good. The major drawback was it was large and combersome.

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