Torque ? Wood prop, Continental IO-240

[jrevens]

I found out. Any where between 4 and 6 ft lbs.

I sure don't want to muddy the waters, but that sure sounds like a VERY low torque spec for a wood prop. Do you know what kind of wood it is made of? Hard Maple is one of the common woods used by some manufacturers. Are you using a face ("crush") plate? What size bolts?

Here are some common propeller brands in the Experimental world, and their recommended torque values for wood props, 3/8" bolts and a crush plate -

Sensenich : 15 to 19 ft. lbs.
Aymar-DeMuth : 18 ft. lbs.
Pacesetter : 25 ft. lbs.
Prince : 17.5 ft. lbs.

[PapuaPilot]

Good point John. The torque on my Catto prop is 25 ft-lb.

[jiott]

This sure is one area where you want to get it right! There are many stories of a prop coming off in flight.

[jiott]

This sure is one area where you want to get it right! There are many stories of a prop coming off in flight.
Maybe that 4-6 is a metric value?

[nlappos]

Here's what Culver Propellers says (using a backer plate) :
Torque Specifications for Propeller Bolts:
1/4” bolts . . . . . . . . . . . 132 inch pounds (+ or – 10 inch pounds)
5/16” bolts . . . . . . . . . . . 144 inch pounds (+ or – 15 inch pounds)
3/8” bolts . . . . . . . . . . . 200 inch pounds (+ or – 20 inch pounds)
7/16” bolts . . . . . . . . . . . 250 inch pounds (+ or – 25 inch pounds)
1/2” bolts . . . . . . . . . . . 300 inch pounds (+ or – 25 inch pounds)

[David47]

Does anyone lockwire the prop bolts together ?

[efwd]

I thought everybody did.

[jiott]

The Whirlwind props don't use lockwire. They use Nordlock washers.

[David47]

I thought everybody did.

Reason I asked the question about lock wiring of prop bolts was a friend of mine used to work with the Australian ATSB (equivalent to USA NTSB). He was investigating an accident where the aircraft lost a prop and the resulting landing involved a serious injury. Turned out the prop bolts were not positively locked in any way. They merely relied on torquing of the bolts, not even lock washers, and it was a wooden prop. Whether it had a crush plate I can't recall, but for me, it's a no brainer - some form of positive bolt retention is critical.