I was flying the other day and in midair, my prop came off.. my enging immediately screamed to 5 billion rpms and died.. luckilly the engine is fine but I lost my prop, the nut and the plate that the prop sits against. (15.00 and 2 weeks of waiting) I got the idea to use 2 prop nuts that I picked up at wally world for a dollar ot hold teh prop on.. Just tighten one down and then snug the other one against it and I dont think I will ever have this problem agaian.. does anyone else do this or am I just a genius

G'day Mate,
No need for 2 nuts, just make sure the one you have is TIGHT.
And it won't come loose, you only need Jam nuts when you get to or above a 75.

Using a four stroke ?

G'day Mate,
Yep, even with a four stroke, the main nut needs to be TIGHT. Then the jam nut can do it's job.

Using a jam nut is always a good idea, but alan0899 is totally correct that both must be tight. Make sure that you are using the thrust washer in front of the prop every time.

Were you using a wooden prop? Wooden props will swell and shrink with humidity this will help the prop nut to loosen...
the only props I've ever seen fly off were wooden....
Use plastic props and tighten the prop nut very tight ..You can use a jam nut if you want as long as you have room.....

I always use the jam nut , even on a Corsair with a scale large Nut , I try to use the original nut , Jam nut then scale nut , no problems with prop coming off .
also when starting a plan if you flood the engine , then use a eletric starter you are creating major back pressure that the starter trys to overcome at the expense of the prop nuts , chances are if the engine starts those nuts will want to come loose