0884

Item 0884

DESIGN: UniCopter ~ Rotor - Blade - VR-7modified - Planform, Profiles and Lift
The red below is the start of converting the airfoil to 8-blade 1150# UniCopter, using VR-9 at very tip only and making R = 8'-6". ~ January 15, 2004
Overview:

Blade tapers from 5.25" chord at tip to 18" chord at centerline of hub.

Airfoil changes from VR-8 at tip to VR-7 at 70% of R., to thicker VR-7s toward hub.

The blade may be given an average active twist of 6º during hover, which as a twist of 0.7058º per foot. (A twist of .6667 degrees per foot appears to reduce the required horsepower by 3% as well as bring the center of lift closer to the hub). This does mean that the elements on the lower advancing blade have greater airspeed and greater pitch than those of the elements directly above when crossing. So what.

Drawing:

Calculations re Airfoil Profile Locations:

		Maximum distance from chord line to top of airfoil as a percentage of chord.	Maximum distance from chord line to bottom of airfoil as a percentage of chord.	Total distance	If R= 96" then 'r' for the following is	Chord at 'r'. Theoretical for 4/ and 5/
		Maximum distance from chord line to top of airfoil as a percentage of chord.	Maximum distance from chord line to bottom of airfoil as a percentage of chord.	Total distance	If R= 102" then 'r' for the following is	Chord at 'r'. Theoretical for 4/ and 5/
1/	VR-9 profile at the tip.	03.360% @ 35%	-02.700% @ 35%	06.060%	102.0"	5.25"
1/	VR-8 at	05.353% @ 34%	-02.799% @ 34%	08.512%	xx.x"	x.x"
2/	VR-7 at xx% of R	09.142% @ 32%	-02.900% @ 37%	12.042%	xx.x"	x.x"
1/	VR-8 profile at the tip.	05.353% @ 34%	-02.799% @ 34%	08.512%	96.0"	5.0"
2/	VR-7 at 70% of R	09.142% @ 32%	-02.900% @ 35%	12.026%	67.2"	5.9"
3/	VR-7 modified to 15%	11.427% @ 32%	-03.627% @ 35%	15.054%	42.2"	6.6812"
4/	VR-7 modified to 16.5%	12.567% @ 33%	-03.988% @ 37%	16.565%	29.8"	7.0687
5/	VR-7 modified to 18%	13.714% @ 32%	-04.353% @ 35%	18.067%	17.3"	7.4594

30% of R is located between 1/ and 2/. A (12.026 - 8.512) = 03.514 change in thickness takes place between 1/ and 2/. This is a change of (3.514 / 30) = 0.117 per percent of change of R. The change of thickness between 2/ and 3/ is (15.054 -12.026) = 3.028 therefore 3/ will be located at (3.028 / 0.117) = 26% further in toward the hub i.e. @ 44% of R.

The change of thickness between 3/ and 5/ is (18.067 - 15.054) = 3.013 therefore 5/ will be located at (3.013 / 0.117) = 26% further in toward the hub i.e. @ 18% of R.

The change of thickness between 3/ and 4/ is (16.565 - 15.054) = 1.511 therefore 4/ will be located at (1.551 / 0.117) = 13% further in toward the hub i.e. @ 31% of R.

Thickness:

This blade has a greater thickness than Item 0850 for the full length except near the tip. GOOD

% of Radius	Distance from center of hub	Airfoil	Chord	Thickness
30%	28.8"			* ( + ) = "
50%	48"	VR-7 14.3%	6.5000"	* ( + ) = 0.9365"
70%	67.2"	VR-7	5.8998"	* (0.0914 + 0.0290) = 0.7103"
90%	86.4"	>VR7<VR8	5.3000"	* ( + ) = 0.6094"

This one has a greater distance between centroids (thickness) [except for near the tip but the chord is slightly less here] and has the center of lift slightly closer to the hub. That means that this blade can be lighter.

Thrust Force and Moment:

From: DESIGN: UniCopter ~ Rotor - Disk - Blade Generated Forces

Back to top | UniCopter Home Page | SynchroLite Home Page | Dragonfly Home Page

Last Revised: October 3, 2004