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Blade Construction

A project log for EVPR: Electric Variable Pitch Rotor

An electrically actuated variable pitch rotor with a wireless interface

peter-mccloudPeter McCloud 07/11/2017 at 01:200 Comments

The previous project log showed the assembled prototype complete with rotor blades. However, the construction of the blades for EVPR hadn't been documented. The rotor blades use a similar process as what's documented in #Inexpensive Composite Propellers/Rotors, but with a few tweaks.The blades are built using a composite layup process. The image above shows all of the materials that go into making the rotor blade. The process starts with the pink object, which is the foam core. The core is cut into the shape of the rotor blade using a CNC router. The core as shown above is after the supports have been trimmed off.

To start, epoxy is mixed and a thin layer is applied to the core. Next, the two strips of uni-directional carbon fiber tape (The two black strips on the far right) are applied over the quarter chord on the top and bottom of the blade. Next, 3 layers of fiberglass (white woven fabric in the image) are applied individually and wetted out with epoxy as they are applied. The fiberglass is then covered with Aeroveil (gauze looking material below the fiberglass fabric in the image) which gives the composite a smooth finish when complete.

The next step is to wrap the blade with peel ply (green plastic) which keeps the bagging material from sticking to the epoxy and then with breather cloth (white felt) and then everything is placed it n the vacuum bag (yellowish plastic).

When vacuum is applied to the bag, the air is removed and the excess resin is sucked through tiny holes in the peel ply and into the breather cloth. This makes the part as light as possible. Below is the part after the epoxy has cured and the item has been removed from the vacuum bag.

Finally the ends are trimmed off, and the axle is attached. This is done by drilling a hole into the root side and using epoxy to adhere the axle to the blade. With the axle attached, the blades can then be installed onto the hub.



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