1104

Item 1104

DESIGN: UniCopter ~ Fuselage - Tail - Boom

Drawing:

xxx

Notes:

Reasons for larger than normal diameter:

Must be quite strong; to support a large(?) movable(?) appendage? 'T'-tail (?). This is not totally true since the horizontal distance between the boom and the rotor disks is quite small, because off rigid rotor, there for the distance from the 'T' horizontal to the boom is not that great.

Large diameter will, to some degree, act the same as a horizontal stabilizer that is located in the rotor's downwash.

The exhaust can travel down an inner (boron?) tube to the end of the tail. This will allow for a tuned exhaust and a reduction in the sound of the exhaust.

The cooling air from the engine can pass down the boom, between the boom's outer tube and the exhaust tube.

Strength: The two tubes can be linked together to give a 'laminated' construction (Consider the rate of thermal expansion between the tubes)

Yaw: The exhaust gas and the cooling gas can interact with a rudder appendage at the end of the tail, which will assist with yaw. (while the engine is running).

Reasons for smaller than normal diameter:

To minimize the vibration resulting from the downwash of the blades. Blade downwash is greater near the tip than near the root, therefor decrease the diameter of the boom at its aft end, so that the diameter at any point along its length is only sufficient to provide the required strength. Vent some of the cooling air out of longitudinal slots in the bottom of the boom. See: DESIGN: UniCopter ~ Vibration Analysis - Rotor Induced - Downwash on Fuselage ~ on Tail Boom

Aerodynamically cleaner body means smaller stabilizers, means thinner boom.

Core:

Would it be advantageous to have a core in the tail boom or not. The core may add a little weight but the skin may be able to be lighter. The core may assist in absorbing vibration and sounds. The core may require a hardened surface so that the tow will not sink into it as it is being wrapped.

Ideas:

Consider giving more support to the boom by bracing off the propeller shaft. This aerodynamic brace may reduce the size of the vertical stabilizer slightly.

Wishbone Boom:

A wishbone configuration for the boom, where the two arms originate at the two hubs may allow for a higher elevation propeller and a stronger boom.

Possibly Relevant Outside Web Pages:

Document # 48 Headline: Aerodynamic Characteristics of Several Current Helicopter Tail Boom Cross Sectio DocID: 0 2476 /usr/local/web/htdocs/ltrs/refer/1986/NASA-86-tp2506.refer.html

Document # 2362 Headline: Exploratory Investigation of Aerodynamic Characteristics of Helicopter Tail Boom DocID: 0 2855 /usr/local/web/htdocs/ltrs/refer/2000/tp/NASA-2000-tp210083.refer.html

John C. Wilson and Henry L. Kelly , Aerodynamic Characteristics of Several Current Helicopter Tail Boom Cross Sections Including the Effect of Spoilers , NASA TP-2506, AVSCOM TR-85-B-3, January 1986, pp. 73, (3.9MB). http://techreports.larc.nasa.gov/ltrs/dublincore/1986/NASA-86-tp2506.html

Daniel W. Banks and Henry L. Kelley, Exploratory Investigation of Aerodynamic Characteristics of Helicopter Tail Boom Cross-Section Models With Passive Venting , NASA/TP-2000-210083, AMCOM-AFDD/TR-00-A-007, June 2000, pp. 53, (772KB). http://techreports.larc.nasa.gov/ltrs/dublincore/2000/tp/NASA-2000-tp210083.html

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Last Revised: August 3, 2004