ORIGINAL: Tired Old Man
Ralph,
The old arguement between a single center bolt and a multi bolt hub is a non sequiter here. It doesn't matter because none of the manufacturers will revert to a single bolt application.
However, for the sake of arguement, how does one compensate for the severe hub compression experienced when using a wood propeller and a single center bolt? Previous comments about using large wrenches to get the center bolt or nut tight enough to prevent slippage do not provide for the prevention of severe hub compression, which most certainly does happen. A correclty torqued propeller using a multi-bolt hub exhibits virtually zero hub compression. One over torqued propeller will indent both sides of the prop with the aft face usually more compressed than the front.
Happy birthday again btw.
TOM, You address the issue correctly. Only friction can hold the prop in place. Friction is clamping force times friction coefficient. (note that clamping surface does not enter the picture here)
In order for the prop to resist the required clamping force, it must have sufficient compression strength (enter clamping surface here)
Hard materials like carbon reinforced plastics have a higher compression resistance than wood. So wood needs large prop washers. If it compresses with the required clamping force, just use larger washers. That is all there is to it.
No locating pins, just the required surface. That should end the single vs multiple bolt discussion. In both cases, the required surfaceto prevent propshiftis the same!
To humour Ralph on his birthday: (here's to you Ralph!)
When the chosen solution is inadequate (engineering error!), the single bolt construction is safer, save for overcompressed hubs like in the original picture of TOM, where the prop parts company with the motor anyway.