1351

Item 1351

DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Core(s)

Drawing:

Eventually some of this work must be moved over to DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Spar & Strength

Increase the chord at the tip by 1 or 2"??

Note:

There will be 4 (or possibly 5) cores.

One core in the Torque Tube.
One core between the leading edge and the elastomer.
One core behind the elastomer and ahead of the trailing twist bar.
One core between the twist bar and the Trailing Edge Block.

All cores can probably be light weight foam.

Could there be a need for a fifth core behind a trail edge stiffening brace?

The two cores inside the spar will most likely require a single layer of cloth on the side next to the elastomeric. This is so that it can transmit the torque from the torque tube to the spar. Consider bi-directional fiberglass cloth or hoop wind in fiberglass with a few spanwise threads. Why. The load is equally distributed across the ID surface of the core and that is all the layer of cloth will do. Perhaps consider denser foam.

It looks like the core length will be 92" to NACA0009 less 10" at root = 82" = 6'-10".

If the spar at the root has an ID of 2.5" and and an OD of 3.0 ' then the area is 2.1607²".

The spar circumference of 2.5" ID is 7.8571", which if flattened would be 3.9286".

The spar circumference of 3.0" OD is 9.4286", which if flattened would be 4.7143'.

There may be a leading core, if the spar and leading edge weight do not require all the room.

The spar profile;

If oval profile, it will require 4 cores.

Strong core inside oval and light core outside?

If wide flange I-beam profile, it will require 2 cores. The mockup shows that it will need 4 cores.

Which profile will give less resistance to twisting? The mockup shows that I-beam will resist the twist the most, unless a better wrapping configuration can be found.

This will include a trailing edge core, if the skin is not strong enough to resist deflection.

How is the very thin core at the tip end machined?
Any filler will add weight but no strength.

It may be better to use dense foam instead of honeycomb. This is because the core will be a small percentage of the blade. A dense core may negate the need for a (bi-directional) web in the spar.

"The core material has little effect on the flapwise-bending-twist coupling" ~ Stiffness Characteristics of Composite Rotor Blades With Elastic Couplings. NASA

Foam Melting:

From CNCzone;

"I have been using a .125 dremel drywall cutting bit. They work bretty good as long as you move pretty fast and run the tool just above stalling out. I still get a bit of melting. I do need to clean the bit every few panels. On parts that come to a point you can see the foam pullinging into the point due to the minimal amount of material."

"I tried a 3/16 carbide up sprial bit and it works very good! no melting at all running at 25ipm."

Generating of G-code using Access ~ CNC Workstation

FORM: Core:

For producing cores for the blade.

Last Revised: September 9, 2005