Showing papers on "Spar published in 1974"

Stabilized, towable spar buoy

Abstract: A spar buoy is dynamically stabilized by providing a streamlined, V-shaped wing just above the center of gravity of the spar. The wing has a dihedral sufficient to stabilize the spar in three axes while under tow. The buoy may be equipped with a radio transmitter and a flasher beacon for tracking by an automatic direction finder.

Hingeless in-plane rotor blade design

Abstract: A hingeless rotor wing system having a relatively stiff in-plane blade which has a one-piece spar of substantially rectangular cross section which is untwisted at the mean blade angle and airfoil defining structure surrounding the spar, the blade angle of the structure relative to the spar being preset to the mean operating angle of the blade in order to reduce the variation of the in-plane natural frequency during operation.

Helicopter blade structure

Abstract: A helicopter main rotor blade having a metallic nose spar extending the length of the leading edge of the blade and a trailing edge skin attached to the nose spar. A closure channel fixed within the nose spar extends the length thereof with unidirectional fiberglass material fixed to and extending along the length of the closure channel. A bushing on the inboard end of the blade preferably is attached both to the nose spar and the fiberglass bands for transfer of centrifugal forces in the blade to a grip.

Fabrication and Testing of Prestressed Composite Rotor Blade Spar Specimens.

Abstract: Prestressed composite spar specimens were fabricated and evaluated by crack propagation and ballistic penetration tests. The crack propagation tests on flawed specimens showed that the prestressed composite spar construction significantly suppresses crack growth. Damage from three high velocity 30 caliber projectile hits was confined to three small holes in the ballistic test specimen. No fragmentation or crack propagation was observed indicating good ballistic damage resistance. Rotor attachment approaches and improved structural performance configurations were identified. Design theory was verified by tests. The prestressed composite spar configuration consisted of a compressively prestressed high strength ARDEFORM 301 stainless steel liner overwrapped with pretensioned S-994 fiberglass.

Current measurements using a tilting spar

Abstract: The dynamic response of the spar to oscillatory flow has been examined by modeling as well as computer analysis of the non-linear differential equation. Field measurements using the tilting spar have been made. These measurements are compared with theory and with other more direct measurements of the wave field. The tilting spar has been used to estimate wave direction. These estimates generally agree well with directional estimates made using a pressure sensor array and a two-component current meter.

SPAR demonstration problems

Abstract: A series of examples are presented to indicate some of the principal functions of the SPAR system and to illustrate SPAR's control card-data card structure. Information in the following categories is given: (1) a description of the problem and, in most cases, comparisons with analytical solutions; (2) a list of the input cards; (3) a printout of the table of contents of the direct access library into which all SPAR output was directed; and (4) a few representative plots.