Item 1445

DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Blade (Spar) Strength

For general information on spar see; DESIGN: UniCopter ~ Rotor - Blade - General - Spar

For construction of spar see; DESIGN: UniCopter ~ Rotor - Blade - Spar - Construction

 The following must be reviewed

Area and Centroid of Spar @ Tip ~ NACA 0006 with 6" chord

 

Zone:

@ Tip:

 

 

Area: *

Centroids

Distance:

 

 

Upper:

Lower:

 

0

.2

.2

."

 

1

.4

.4

."

 

2

.5

.5

."

 

3

.6

.6

."

 

4

.7

.7

."

 

5

.7

.7

."

 

6

.8

.8

."

 

7

.8

.8

."

 

8

.8

.8

."

 

9

.7

.7

."

 

10

.7

.7

."

 

11

.6

.6

."

 

12

.6

.6

."

 

13

.6

.6

."

 

14

.5

.5

."

 

15

.4

.4

."

 

16

.4

.4

."

 

17

.3

.3

."

 

18

.3

.3

0

 

19

.2

.2

0

 

20

.2

.2

0

 

21

.1

.1

0

 

22

.1

.1

0

 

23

.0

.0

0

 

Total:

11.2

11.2

 

 

 

22.4 = 1.4 sq-in.**

 

 

 

Average (approx):

 

* Area is number of 1/4" squares. ** This includes the skin.

Mass: Carbon fiber weighs 0.0164 pounds per square inch, which is (0.0164 * 1.56) = .023 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 (0.023 * 2 * 100) = 4.59 pounds. To this must be added the core, the leading edge weight, the tip and "things" at the root. THE ABOVE IS PROBABLY GOING TO BE LIGHTER THAN ACTUAL SINCE THE COMPOSITE MAY HAVE TO INCREASE TOWARD THE ROOT AND THE EPOXY PROBABLY WEIGHS MORE.

 

Centroids:

 

Element:

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

Profile

Chord: (in.)

Thickness - Upper or Lower (in.) **

Thickness - Sum (in.)

Centroids Distance (in.)

 

0

0

~

~

~

 

 

 

1

0.5"

 

2.16 ?

1.179" ??

2.358" ??

 

 

2

10.5"

 

3.4968

1.071"

2.142"

 

 

3

20.5"

 

5.9336

0.963"

1.926"

 

 

4

30.5"

 

7.9536

0.855"

1.710"

 

 

5

40.5"

 

7.6408

0.747"

1.494"

 

 

6

50.5"

 

7.3288

0.639"

1.278"

 

 

7

60.5"

 

7.0160

0.531"

1.062"

 

 

8

70.5"

 

6.7032

0.423"

0.846"

 

 

9

80.5"

 

6.3912

0.315"

0.630"

 

 

10

90.5"

 

6.0784

0.207"

0.414"

 

 

 

At tip

 

 

0.18"

0.36"

 

 

 Total =

 

 

 

 

 

 

* Element is 10" long. Moment arm is at the 75% point of element (7.5") 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:

 

Element:

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

Moment (lb.-in.) **

Profile

Centroids Distance (in.)

 

 

0

0

0

~

 

 

 

1

0.5"

2

 

 

 

 

2

10.5"

61

 

 

 

 

3

20.5"

166

 

 

 

 

4

30.5"

309

 

 

 

 

5

40.5"

486

 

 

 

 

6

50.5"

695

 

 

 

 

7

60.5"

935

 

 

 

 

8

70.5"

1207

 

 

 

 

9

80.5"

1515

 

 

 

 

10

90.5"

1864

 

 

 

 

 Total =

 

7240

 

 

 

* Element is 10" long. Moment arm is to the 75% point of element (7.5") and pivot is located at 7" radius. 

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

 

Notes re strength:

Deflection:

See: DESIGN: UniCopter ~ Rotor - Disk - Anhedral

Pultruded:

Produce spar as close to pultruded as possible, to achieve highest possible strength.

 

Related Page:

DESIGN: UniCopter ~ Rotor - Blade - General - Spar

MAKE: SynchroLite ~ Rotor - Blade - Composite

 

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Last Revised: July 30, 2005