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Cory Bird's Symmetry details

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gschuld

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There are a whole bunch of planes out there that inspire me, and Cory Bird's former Oshkosh Grand Champion is one of them. For those who are not aware, Cory Bird is one of the main guys at Scaled Composites. Besides the concours quality finish(which could arguably be overdone on a practical level) and the flowing unique lines, I am impressed with the mountains of effort he put into making the airplane as "clean" as possible.

For example, note that there are no obvious external signs of fuel tank vents, fuel drains, a pitot tube, etc.











While reading through some of the articles written about the plane, I came across the following.

From here:
Sportsman Pilot Magazine- Article Library- Spring 2003

Cory built the composite landing gear over a particle board former. It's all S-2 glass and high temperature resin, with an overlap of carbon fiber to better resist torsional drag loads. Cleveland 5:00x5 wheels and brakes with low profile tires were used, and gear leg fairings were made for streamlining and enclosing the brake lines and fuel vent lines.

From here:
Aero-News Network: The Aviation and Aerospace World's Daily/Real-Time News and Information Service#

The large pitot tube found on most planes is replaced by a tiny opening on the nose of the left wheel pant.



And from here:
http://www.popsci.com/military-aviation-space/article/2004-01/tiny-perfect-little-flying-machine

The fuel-tank drains on the belly are what the industry calls flush drains, which generally have an eighth-inch protrusion beyond the skin of the airplane. An eighth inch too far for Cory Bird, who totally remachined the stock push-up drains and mounted them in bushings that are, well, flush.

(I couldn't find a picture of it.)

I can see the pitot tube in the picture above and I get the idea what the trimmed flush drains look like. But I haven't yet figured how he did his fuel vents. According to the Sportsmanpilot article: "...and gear leg fairings were made for streamlining and enclosing the brake lines and fuel vent lines." Cory Bird's plane has two fuel tanks mounted just outboard of the pilots leg position along the fuse sides between the seat front and the firewall. The gear legs appear to intersect the fuselage right under each fuel tank. I would assume that each tank has a fuel vent tube running down the gear leg under it. But I don't see and evidence of how the vent system works. I don't see any obvious vent openings on the wheel pant closeup picture. Any ideas?

Any thoughts as to the practicality of any of these concepts for use on other planes. I am all for keeping drag to a minimum and keeping everything as clean as possible, but not at the sacrifice of a healthy degree of function and safety. For example, I wonder how accurate his pitot tube is considering it only seems to protrude about 3/8" or so infront of the wheel pant:lick:.

That plane is a whole bunch of food for thought....

George
 

bmcj

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I suspect the vent lines travel upward from the top of the tank (a "reverse trap" inside the fuselage sidewall) before going down through the gear legs. They may even terminate like the pitot picture (maybe that is the fuel vent) to allow the pressure stop any siphoning tendencies.


As far as the pitot system goes, as long as the tube is mounted at the stagnation point on the wheelpant, it should be OK... after all, a pitot tube takes moving air and stops (stagnates) it to recover the pressure for measurement.

Bruce :)
 

Topaz

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Quite a few (and very many high-performance) sailplanes have the pitot at the very tip of the nose, concentric and flush with the edges of the cockpit vent tube, which is also at the tip of the nose.

As Bruce says, all that matters is that you can measure stagnation pressure (q) at that point on the airframe.

Beyond that, all I have to say is that's one of the downright sexiest airplanes I've ever seen. Ever.
 

gschuld

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BMCJ,

I had kind of figured that the vents went up from the tanks before dropping through the gear legs. But it's where the exit the pants that interest me. The pitot tube is definitely the tube sticking out on the fwd tip of the left wheel pant. Three seperate articles describe the exact same left side pitot tube. I imagine any non pressure vent lines could exit out the bottom of the pants behind the tires or near the trailing edge, but the pressure vent needs to face forward do a degree. I just dont see it:lick:!

Topaz,

Yup, a pretty bird indeed :)


So besides the obvious extra work involved in routing the lines and mounting the vents/pitot tube in the wheel pants, is there any functional reason not to go this route?


George
 

Topaz

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Better watch how your vent line enters the fuel tank. If there's any opportunity to create a siphon, you'll pump fuel overboard until the vent inlet in the tank breaks surface or the tank pressure drops enough. There's enough head there that it might still siphon even if the vent line points forward, especially if there's a redunant vent line in the other leg.
 

gschuld

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Toms River, New Jersey
I was thinking along the lines of routing the vents this way (in the picture the wing is upside down in the picture and the vent tube does run to the highest point in the fuel tank once inside the fitting) This is how the plans call for all the RV8 rockets and RV10s. Instead of having the vent exit through the lower wing skin, it could be run down each gear leg and facing at least partially forward on the wheel pants. Perhaps:lick:



From:
Building Tip - Fuel Tank Vent Line - VAF Forums

George
 

shadow

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I don't see how much of the tire is exposed at the bottom of the wheel pant but it's possible that the vent tube is on the inside of wheel pant just in front of the tire. With at least a portion of the tire hanging in freestream there should be a high (relatively speaking) pressure zone right there, inside the wheel pant.

It's a thought at least, *shrug*
 
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