Cox 3 blade pusher prop cracks

I personally wouldn't boil any props. It doesn't work and for the cost of a new prop in good shape it's not worth it. I owned 30 or more of those pusher props and all went into the trash due to the same reason. You need to flex the props prior to using them. They've more than exceeded their lifespan. I was running a Super Tiger .51 with a Top Flite nylon which I did boil. After several minutes of bench running, the engine started to vibrate and I reached over to pinch off the fuel line. The blade let go and went into my rib cage between two ribs. I really don't know how it didn't hit my lung. So the lesson learned that day was to just throw them out. Just the hours lost in the emergency room alone wasn't worth it to me not too mention the two additional trips to my doctor afterwards. Now one can argue that the engine I was using was large compared to the .049 but I can assure it's not and I have seen more injured by the .049 over any other engine.

Back in the 1980's, used to be a manufacturer's white paper gum label on each Top Flight narrow blade white nylon with red silk screen lettering and stripes. It stated that before use to boil the props.

Nylon has a certain amount of water moisture contained therein. Boiling helped to restore the moisture to the nylon.

That said, nylon also can crack from aging, hence why as a general ruled it has been recommended to retire old props.

I really liked the T/F white nylons, because they were very inexpensive plus could stand up to a certain amount strike damage (grass, weeds, dirt, etc.) But, they seemed to be notoriously out of balance. One had to sand the back side of the heavier blade to get it to balance.

When the Masters fibre filled props came out, they were a touch more, but they were much better in balance (when their manufacturing dies were new, later seemed to have a lot of untrimmed flashing, which I gather were probably from well worn moulds.) Plus, with T/F discontinuing the white nylons, the Masters became my prop of choice.