Doesn't the prop manufacturer have torque info available? JImChuk
Doesn't the prop manufacturer have torque info available? JImChuk
Jim's right... every propeller I've ever bought, whether wood, composite or metal has had available recommended torque values. Wood props, especially, will vary depending on type of wood, composition & other factors. That is one area you'd be very wise to avoid guessing about. Follow the manufacturer's recommendations/specifications.
John Evens
Arvada, CO
Kitfox SS7 N27JE
EAA Lifetime
Chap. 43 honorary Lifetime
Do you have the torque sequence and is it done in increments?
Phil Nelson
A&P-IA, Maintenance Instructor
KF 5 Outback, Cont. IO-240
Flying since 2016
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.
John Evens
Arvada, CO
Kitfox SS7 N27JE
EAA Lifetime
Chap. 43 honorary Lifetime
Good point John. The torque on my Catto prop is 25 ft-lb.
Phil Nelson
A&P-IA, Maintenance Instructor
KF 5 Outback, Cont. IO-240
Flying since 2016
This sure is one area where you want to get it right! There are many stories of a prop coming off in flight.
Jim Ott
Portland, OR
Kitfox SS7 flying
Rotax 912ULS
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?
Jim Ott
Portland, OR
Kitfox SS7 flying
Rotax 912ULS
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)