Item 0886

DESIGN: UniCopter ~ Rotor - Blade - VR-7mod - Spar

Information related to the load carrying capability of the blade and its rigidity.

Consider using VR-9 at the very tip. ~ February 10, 2002

Drawing:

Blade Loading:

See: DESIGN: UniCopter ~ Rotor Disk - Blade Forces

See: DESIGN: UniCopter ~ Rotor - Blade - General - Spar

Area and Centroid of Spar @ Tip VR-8 ~ 5" chord

 

Zone:

@ Tip:

 

 

Area: *

Centroids

Distance:

 

 

Upper:

Lower:

 

1

.3

.1

."

 

2

.6

.3

."

 

3

.8

.4

."

 

4

.9

.4

."

 

5

1.0

.4

."

 

6

1.0

.5

."

 

7

1.1

.5

."

 

8

1.1

.5

."

 

9

1.05

.5

."

 

10

1.0

.45

."

 

11

.9

.4

."

 

12

.8

.35

."

 

13

.7

.3

."

 

14

.6

.25

."

 

15

.5

.2

."

 

16

.45

.2

."

 

17

.4

.15

."

 

18

.3

.1

0

 

19

.2

.05

0

 

20

.1

.05

0

 

21

.0

0

0

 

Total:

14.8

6.1

 

 

 

20.9 = 1.31 sq-in.**

 

 

 

Average (approx):

 

* Area is number of 1/4" squares. ** This includes the skin. The thin core has not been deducted.

Mass: Carbon fiber weighs 0.0164 pounds per square inch, which is (0.0164 * 1.31) = .0215 pounds per running foot of blade. If THE AMOUNT OF COMPOSITE DOES NOT INCREASE AS ONE MOVES TOWARD THE ROOT and the resin is the same weight then the weight of the carbon then composite portion of the blade is (0.0215 * 2 * 96) = 4.1249 pounds. To this must be added the core, the leading edge weight, the tip and "things" at the root. THIS IS PROBABLY GOING TO WORK OUT TO LIGHTER THAN ACTUAL SINCE THE COMPOSITE MAY HAVE TO INCREASE TOWARD THE ROOT AND THE EPOXY MAY WEIGH MORE.

 

Centroids:

 

Element:

Length of Arm to 75% of element (in.) *

Profile

Chord: (in.)

Thickness - Upper (in.) **

Thickness - Lower (in.)

Thickness - Sum (in.)

Centroids Distance (in.)

 

0

0

~

~

~

~

 

 

 

1

0.2"

Round

~

1.08

1.0800

2.1600

 

 

2

9.8"

 

7.4640

1.0332

0.8000

1.8332

 

 

3

19.5"

 

7.1688

0.9401

0.2911

1.2312

 

 

4

29.0"

 

6.8744

0.8470

0.2623

1.1093

 

 

5

38.6"

 

6.5592

0.7539

0.2335

0.9874

 

 

6

48.2"

 

6.2632

0.6608

0.2047

0.8655

 

 

7

57.8"

VR-7

5.9800

0.5677

0.1759

0.7436

 

 

8

67.4"

 

5.6904

0.4745

0.1612

0.6357

 

 

9

77.0"

 

5.3752

0.3814

0.1511

0.5325

 

 

10

86.6"

VR-8

5.0656

0.2883

0.1410

0.4293

 

 

 

At tip

 

 

0.2650"

0.1385

0.4035

 

 

 Total =

 

 

 

 

 

 

 

* Element is 9.6" long. Moment arm is at the 75% point of element (7.2") and pivot is located at 7" radius. 

** 84" from tip to start of circular root. Change in upper dimension is ( 1.08 - 0.2650) = 0.815. Change per inch is (0.815 / 84) = 0.0097"

 

Strength: Must be increased to a GW of 750 pounds? The Moment values have now changed.

 

Element:

Length of Arm to 75% of element (in.) *

Moment (lb.-in.) **

Profile

Centroids Distance (in.)

 

 

0

0

0

~

 

 

 

1

0.2"

0

Round

 

 

 

2

9.8"

0

 

 

 

 

3

19.5"

60

 

 

 

 

4

29.0"

161

 

 

 

 

5

38.6"

349

 

 

 

 

6

48.2"

657

 

 

 

 

7

57.8"

1250

VR-7

 

 

 

8

67.4"

1464

 

 

 

 

9

77.0"

2034

 

 

 

 

10

86.6"

2496

VR-8

 

 

 

 Total =

 

8221

 

 

 

* Element is 9.6" long. Moment arm is to the 75% point of element (7.2") and pivot (blade root) is located 7" out from the center of the rotor. 

** At; hover, gross weight & out of ground effect. From Access Database calculations.

 

Deflection Notes:

See: DESIGN: UniCopter ~ Rotor - Disk - Anhedral

Miscellaneous Notes:

Spar to utilize pultruded carbon, to achieve highest possible strength.

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Last Revised: July 27, 2003