Propellers , spacers and long bolts

[DennisRhodes]

Propellers , spacers and long bolts question for A&P

I have a 0320 RV9 that has 500+ hours on an arrangement where the Prince P tip "wood " prop is thru bolted to the LYC crank flange . It has a 1/8 spacer and 1/2" AL spacer to make up for the spinner front bulkhd. It also has the 2 1/4 thru bolt spacer between the rear spinner bulkhd and the LYC starter ring flywheel.
Have been toying with the idea of removing the 1/2 inch Al front crush plate and replacing with a Saber steel 1 inch thick crush plate. Effectively adding 10 Lbs weight to the 13FS and improving the rear CG loading issue. My Concerns are primarily the additional 1/2 Inch of prop bolt length needed and the 10 Lb wt with that arrangement. Present Prop bolt length are AN7 X 8 5/16 in Would have to go to an AN7 X 8 3/4 in to get my required 3/4 in threads into the inserts.
Do the longer bolts raise a concern for this new arrangement? Only other option would be to replace the spacer with a new Prop Extension with separate bolting to flange.

 

[DennisRhodes]

edit and bump

 

[DanH]

Dennis, the bolts are clamping devices, really springs which are stretched to a specific tension. In this application, the bolts do not transmit engine torque. They merely clamp the parts together, and here you are not changing the clamping force.

Actually, when clamping a wood prop, the longer bolts are safer. Given a short bolt, a very high percentage of the bolt tension goes away with only a small shrinkage of the wood hub. For the same hub shrinkage, the reduction in tension is less as the bolt becomes longer.

I don't think the additional mass of the 1" steel plate would make any practical difference in terms of the prop assembly. Technically there would be a tiny addition to precession load given a high pitch or yaw rate, but we're talkin' tiny, and power-on flat spins. I suppose it could be off center and cause a balance problem if your prop holes are oversize. You could fix that by adding a centering stub into the prop center hole.