1054

Item 1054

DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Profiles (x-sections)

For associated Planform see;. DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Planform

This page is associated with the spar on pages 1355.html and 1082.html.

Drawing:

Re the root end view above. It will probably be rotated 22.5º so that it can be split vertically, with four bolts on each side.

This is an idea to initially build a NACA 00xx spar, because of its symmetry and greater thickness, which has separate root and tip control.

Take the x-section area at the tip on to the root. The deeper web and the shorter threads will give the extra strength.

The blade has a spar half-thickness at the tip with a NACA 0006 7" chord of 0.1493" and a radius at the root of 1.625" The span is 114" - 10" = 104". This means that the half-thickness increases 0.0142" per inch of span.

Tip [NACA 0006] has a thickness of 0.42". 64" closer to the root, at the widest chord the thickness is 2.2376". The chord at this location is 14.5259", therefore, the profile is NACA0015.4.

Location of Tip Pitch Control:

NACA0007 at r/R = 0.94 ~ 106.7" is the free tip end of the torque tube.
The torque tube projects out beyond location to the 'wand' but it is bonded to the spar from here on out.
The pultruded leading and trailing edges will start at this location.

Location of Start of Machining Spar:

NACA0008 at ????

Dimensions: The entries in this table are new. June 21, 2004

Span r/R	Profile:	Chord:	Max. Thickness Including Skin	Thickness of Two Skins	Max. Thickness of Spar	Area Available for Spar and Core: (sq-in) Approximately
1.0 ~ 114"	0006	7.0"	0.4200	0.104	0.316	14 * .25² = 0.875 sq-in
0.94 ~ 106.7"	0007	7.84"	0.5144	0.104	0.4104	25 * .25² = 1.562 sq-in
0.87 ~ 99.3"	0008	8.68"	0.6088	0.104	0.5048	39 * .25² = 2.44 sq-in
0.807 ~ 92"	0009	9.51"	0.7032	0.104	0.5992	56 * .25² = 3.5 sq-in 34 * .25² = 2.125 sq-in ⁽²⁾
				0.104
				0.104
				0.104
				0.104
				0.104
Not the choice	Round	2.875" dia.	~	0.0	2.875"	1.58 sq-in ⁽¹⁾
This is the choice	Round	3.0" dia.	~	0.0	3"	2.1607 sq-in ⁽¹⁾

Notes:

value from MAKE: UniCopter ~ Rotor - Blade - NACA 00xx - Spar - Root

This area is based on the spar area in front of the axis equals the area at the rear of the axis. This area is the same as the root. From NACA0009 to the tip will be machined down.

The following is from the old idea and is probably irrelevant. The spar consists of a number of pre-pultruded rods.
Calculating Spar's Internal Dimensions from 0021 to Tip:

Profile 0021 has an 8" chord and profile 0018 has a 7.6" chord. Therefore, the inside lines of the 0018 spar are scaled by (7.6 / 8) = 0.95%.

Then the thickness is scaled by 18 / 21) = 0.8751%.

Profile 0018 has an 7.6" chord and profile 0015 has a 7.2" chord. Therefore, the inside lines of the 0015 spar are scaled by (7.2 / 7.6) = 0.9474%.

Then the thickness is scaled by 0.8751%. Am keeping the thickness scaling the same all the way to the tip to give a proportionally greater x-sectional spar area toward the tip.

Profile 0015 has an 7.2" chord and profile 0012 has a 6.8" chord. Therefore, the inside lines of the 0012 spar are scaled by (6.8 / 7.2) = 0.9444%.

Then the thickness is scaled by 0.8751%.

Profile 0012 has an 6.8" chord and profile 0009 has a 6.4" chord. Therefore, the inside lines of the 0009 spar are scaled by (6.4 / 6.8) = 0.9412%.

Then the thickness is scaled by 0.8751%.

Profile 0009 has an 6.4" chord and profile 0006 has a 6.0" chord. Therefore, the inside lines of the 0006 spar are scaled by (6.0 / 6.4) = 0.9375%.

Then the thickness is scaled by 0.8751%.

Calculating Spar Profile for 0024 Location:

Profile 0021 has an 8" chord, therefore profile 0024 will have a theoretical chord of 8.4". This means that the thickness of the airfoil will be .24 x 8.4" = 2.016". The chord will be 4.888" and this means that the actual profile will be 2.016 / 4.888 = NACA 0041.

Therefore, the inside lines of the 0024 (0041) spar are scaled by (8.4 / 8) = 1.05%. Probably not since too weak.

Then the thickness is scaled by 24 / 21) = 1.1429%. Probably not since too weak. Perhaps the thickness should be increased at tne root end where the chord is shortening.

Blade Spar Loading; Approximately

at 0021 Profile:

Moment @ GW is 3,867 in-lb. Moment at 10 g is 38,670 in-lb

Distance between centroids is 1.1 inches.

Load on spar is 38,670 in-lb / 1.1 in = 35,154 lbs.

Area of half spar is 1.75 sq-in

Loading on spar per square inch is 35,154 / 1.75 = 20,088

Carbon is 70,000 to 160,000 psi.

Based on carbon and vacuum bag:

65,000 psi in compression

70,000 psi in tension

This give safety factor (or something) of 3.48 to 7.96. Too OK?

Note:

It may be advantageous to have the core consist of all spar at the NACA 0009 location and then on out to the tip. This will result in the portion of the blade beyond NACA 0009 being proportionately weaker but because of tip loss, this should be OK.

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Last Revised: September 12, 2004