Damn, props get expensive. And it gets very discouraging to come back from a flight attempt with nothing but another repair and paying for replacement parts. I almost quit. Winter made it easier to decide to experiment with repairing the propeller. I figured I could do it … motivation to do so was the issue. I am not happy that the prop tip and spar ends somehow manage to get within reach of each other. Thanks to Mateo at E-Props for cutting me a deal on a shorter prop, and John at Bailey for taking care of my parts orders. If I still had my Tig welder I would make my own parts.
I suppose if there was always someone knowledgeable, or with a camera in the appropriate spot I could solve these conundrums quicker and with more confidence. But it is mostly just me at launch. Definitely, the Matrix frame is not an adequate design - probably why Bailey stopped offering it a long time ago (although they still have spare parts). It will sag with just the slightest jostling due to not being adequately triangulated. When I was flying it conventionally on my back, the frame would sag while just being transported a few hundred yards on the rear car rack. It sagged so far that the muffler almost made contact with the gas tank! I do as thorough a pre and post flight as possible to spot these things. I tore the entire frame down twice to straighten it. Eventually I made pipe supports to use with the car rack to prevent this. Just on your back the frame is fine. Obviously, on the trike I also took this into consideration. Still the original frame strut eventually failed, with the aluminum stub (press-fit? bonded?) pulling free. It is directly bolted now. Repeat after me: “Experimental Aircraft, fly at your own risk!”
When doing carburetor work and replacing it, if clearances are not carefully checked, it can make contact with the motor mount causing abrasion severe enough to wear through the carburetor. I was lucky to spot this before it abraded through the bottom of the primer/accelerator pump. It was fixed by filing the aluminum motor mount to create more clearance, and watching this more closely. There is not much wiggle-room room for error here, and plenty of vibration to cause damage.
It was not my intent as part of this video to show how to repair a propeller. If you don’t have mold making experience I would not even try this. It is challenging due to the constantly changing parting-line for this type of mold. I had all the materials from previous projects so, having no additional out-of-pocket expense, I took it on as a winter project. Primarily small scrap fiberglass pieces were used to make the mold. Trying to film it would have just been frustrating for me as it is not my intention to be a Kyle or a Tucker. For more details, here is a video from Kyle Oglee’s channel:
Paramotor Propeller Mold Fabrication & Damage Repair Composites Carbon Fiber & Fiberglass - KZitem
I will add that I used thin packing foam to replicate the foam interior of the E-Prop; to displace and prevent excess resin buildup. The carbon was pre-cut to match the mold and damaged tip. The foam was pushed into the prop tip after cleaning the cavity of some of the existing foam with a Dremel tool. After wetting out the to-be-inserted portion of the first layer of carbon fiber, it was then pushed between the foam and the existing carbon fiber to anchor it securely. After completing the wet out of this layer of carbon, two additional layers of carbon were added with enough resin added to assure no bubbles. This was done on one side and then placed into the mold and secured with a clamp, followed by the same layup on the opposite side. The tips and edges were also finished off with some additional strands of carbon for strength, and to displace excess resin. The clamp was carefully removed and the top half of the mold set into place. The mold was then clamped securely, and I crossed my fingers for a good result as I saw the expected excess resin squeeze out from the small channels cut into the mold. As can be seen in the photos, the excess resin forced out when the two halves of the mold came together caused the outer strands of carbon fiber to be displaced. This can occur with carbon even with simple hand layups. Oh well, it was nice and neat beforehand and there is little loss in strength - just my pride hurt. (Blue tape on the prop provided an accurate guide for the initial insertion distance into the mold, as the prop tip doesn’t exist yet.) Waterless, alcohol-based hair spray used as mold release (read the label) after 4 coats of Johnson’s Wax - worked well. And much cheaper than buying PVA! This repair resulted in about a 5g weight difference between the prop halves. Four coats of clear coat on the opposite/lighter tip, resulting in a smaller lead solder weight insert brought everything into balance. With the two halves accurately aligned, I used a PVC pipe and some vibration when balancing. It ran-up just like new after remounting.
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