40 inch pounds is between 3 and 4 foot pounds. About the time a hex wrench snugs up to the hub you made 40 inch pounds. The down side is that props have to be checked about every four or five flights for bolt security. Add a spinner over the prop and it's pretty clear why prop bolts don't get much attention. They end up an install and forget item, which is exactly opposite of what they should be. Full scale and uav's have checking the prop security before every flight part of the pre flight process, and the reality is our gassers are no different. Many uav's use engines the same size as what we use. Ifthey feel they need to check the propeller before every flight, perhaps we should consider doing it a bit more often that we do.

The longer a prop is used the deeper a prop washer will sink into a wood hub. That time span is extended considerably if the correct torque amount is used. Those that crank down on a new wood hub do about 4 months of hub compression in the first installation. Each successive installation of the prop compresses the hub even more. At a certain point a split starts at the hub. At 40 inch pounds there is generally only a slight marring of the finish on a wood prop, but no compression.

Many of us store our models indoors, and the process of moving them in and out has been noted as a danger period creating a lot of "hanger rash" Typically propellers, rudders, and horizontal stabs manage to run into door frames and parts of automobiles during the transport process. Each one of those dratted moments has the ability to generate minor propeller damage that won't be discovered until after the prop reaches a high rpm level and loads up. That's when that invisible stress fracture becomes very visible...

Propellers most certainly do wear out, so checking them often is a good thing.