Item 1072

DESIGN: UniCopter ~ Rotor - Blade - General - Root

Drawing:

 Sleeve for Bearings:

Consider using a very thin steel sleeve on the root end of the blade. The inner races of the pitch bearing will sit on this sleeve. The carbon composite will be preasure and heat bonded to the inside of this sleeve and when the curing of the blade is done and the heat is reduced to room temperature, the sleeve will shrink onto an expanding carbon composite.

 Notes:

Pultruded rods and unidirectional tape that tapers down to smaller diameter at the very end is to be wound (bound) with unidirectional tape to note allow the pultruded rode to open up.

What about thermal expansion between bearings and carbon root?

 Spar:

Pictures; [Source ~ TH# p.118] There is also about 2 pages of German text with the pictures, which might be of interest.

See also [FWCS, Section 8.1.3] for a sketch and patent re wrapping around holes.

Idea for Construction:
    1. Consider producing the blade as per DESIGN: UniCopter - Rotor - Blade - VR-modified - Spar except that each pultruded group of thread around a single spindle is produced as a single item. In other words, there will be a number identical of pultruded carbon rods with a 90º bend and sleeve at one end.
    2. These rods are then ground to conform to the desired shape for a specific segment of the spar.
    3. These spar segments are then located in their final position.
    4. Unidirectional carbon cloth, with the threads running vertically, is located between two segment in the upper surface and also between two segments in the lower surface. A cloth will run the full span length and there will be a number of them. There purpose is to assure that the spar will not expand in the out-of-plane direction during usage. This intent is the same as the core assuring that the spar contract in the out-of-plane direction during usage.
    5. The unidirectional clothes are bonded to the pultruded segments by a flexible epoxy.
    6. The intent of the above is to produce a spar that has extreme rigidity in the ni-plane and out-of-plane but will have a relatively low resistance to twist about the feathering axis.

 Outside Information:

Development of an efficient root design for a composite rotor blade; http://www.arcs.ac.at/AMTT/reports/report28.pdf

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Last Revised: October 20, 2005