As spring time has rolled around, I am finally working on some of my outdoor models – yes, I am always behind the curve. This prop is for my Jumbo Scale Aircraft Designs Stallion. You may remember – oops, I guess I never posted the assembly pics for the Stallion…
Anyway, I’ll start from the beginning. Back in the late ’90s, I built my first Jumbo Stallion and I put on a fully carved 3-bladed prop to match the full scale aircraft. It broke just about every landing, but I still have it – here it is:
When I built this second Jumbo Stallion last year, I wanted another 3-bladed prop and made it a folder. While it flew the model, I believe it had too little blade area – and – the blades started to pull off the hub. Here is a photo of that prop:
Over the winter, I decided to go with a 2-blade folder of typical design, more suiting to the power loading that I expect for the model. BUT – since I got a 3D printer, I decided the hub would be printed and integrate the base for the spinner. Here are some build pics for this new prop (read the captions for details):
the 3D-printed hub with integrated spinner base. Bushed with a 1/8″ aluminum tube.
The printed hub and the Superior Props 14″ blank. The final prop is 13″ in diameter. The “X” marks the part of the balsa prop to be removed.
The hub and prop blank – now with the center portion removed. ALL of the center of the prop will eventually be removed, but it needs to be there for construction, keeping the blades in proper relative location.
The hub in place with the locating 3/32″ aluminum tubing. The next step is to glue the hub to the balsa – only at the ends of the hub.
Prior to cementing the hub to the balsa, hinge wire had to be installed. Here they are and the basic outline of the prop blades has been marked on the blank.
The completed prop. The hinge wires were bound to the blades, bass leading edges glued to the blades, and the blades finish carved and sanded. The blades were rubbed with medium CA, sanded and balanced. At this point, the blades are still cemented to the hub.
New spinners ere vacu-formed. An accurate plug was printed and sanded (3D printing does NOT leave a smooth surface) and red plastic was formed over it to smooth it all out for final production. Two spinners were pulled from 0.030″ white styrene.
The blades have been painted with Design Master Gray and are still cemented to the hub. Here are the pins embedded in the hub and blades to mount dental bands to hold the prop open. You can also see the three #0 pan-head screws that will hold the spinner to the base. Note that a flange and anchor points had to be printed into the base to accommodate these screws.
The glue joint was cut with a razor saw to complete the folding operation. Full folding alignment is not critical because this folder is always open and only flexes to prevent breakage on landing.
Here is the finished prop mounted on the model fuselage. This prop and hub actually weighed a gram less than the temporary 12″ plastic Chinese prop I used at the end of last season. Testing will happen in two weeks, weather permitting.
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