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N44VY · 19 September 2009, 10:14 AM

Vet: after I talked with you, I did talk with the prop maker, Ed Sterba. His point, based on experiences with other pusher-types he builds props for is this: If the prop is too close to the trailing edge on a faster plane and/or one turning a higher RPM, there is a pulse every time the blades cross the trailing edge. Depending on the relative strengths of the prop or the trailing edge, one will crack after it reaches its respective fatique cycle. At 60 MPH and about 2500 RPM maximum, we do not figure to encounter pulses proportional enough to cause damage on my Curtiss Model D replica. Still, as Ed says, very close monitoring is required. We determined that the closest I could place the prop to the trailing edge is 3 inches, with 4" better. You and I discussed the possibility that the engine itself might flex fore and aft with power, based on the way the engine is mounted. There are plenty of cross tubes and diagonals, but there is still a possibility for shifting. It sure would be helpful if someone with Curtiss Pusher experience would sound off about this topic!

Back to the shop. I have all the leading edge cuffs formed, so today is scheduled for bending the turnbuckle and cable ears. I still haven't welded the sockets for the interplane struts, all 32 of them. That will be a good job for the winter.

Those cowls are Taylorcraft - one is Andrew King's, the other is for our T-craft project, but it's for a Lycoming, so we'll have to cut some, weld some, shape some more to fit the A-65-8. Regards, Bob C.

19 September 2009, 10:14 AM	#13 (permalink)
N44VY Observer Join Date: Mar 2009 Location: Shenandoah Valley Posts: 58	Thanks for input Vet: after I talked with you, I did talk with the prop maker, Ed Sterba. His point, based on experiences with other pusher-types he builds props for is this: If the prop is too close to the trailing edge on a faster plane and/or one turning a higher RPM, there is a pulse every time the blades cross the trailing edge. Depending on the relative strengths of the prop or the trailing edge, one will crack after it reaches its respective fatique cycle. At 60 MPH and about 2500 RPM maximum, we do not figure to encounter pulses proportional enough to cause damage on my Curtiss Model D replica. Still, as Ed says, very close monitoring is required. We determined that the closest I could place the prop to the trailing edge is 3 inches, with 4" better. You and I discussed the possibility that the engine itself might flex fore and aft with power, based on the way the engine is mounted. There are plenty of cross tubes and diagonals, but there is still a possibility for shifting. It sure would be helpful if someone with Curtiss Pusher experience would sound off about this topic! Back to the shop. I have all the leading edge cuffs formed, so today is scheduled for bending the turnbuckle and cable ears. I still haven't welded the sockets for the interplane struts, all 32 of them. That will be a good job for the winter. Those cowls are Taylorcraft - one is Andrew King's, the other is for our T-craft project, but it's for a Lycoming, so we'll have to cut some, weld some, shape some more to fit the A-65-8. Regards, Bob C.