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Front Spinner Bulkhead Deforming?

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Supporting Member
Feb 1, 2007
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I have been in the process of fitting a polished aluminum spinner to my O-360 powered Acro Sport II. I have a Sensenich metal prop, and an AC-1 spinner that I got from Aircraft Spruce.The prop bolts are 1/2" bolts, with washers, that I purchased from Sensenich.

Anyway, while I was cutting the blade openings, I just had the prop, with both spinner bulkheads, snugged down with the bolts. Everything was fully seated, but the bolts weren't torqued to 60-65 ft-lbs. Yesterday, I wanted to test run the engine, so I removed the prop, and the bulkheads, and then cleanedand reinstalled them. I noticed, as I was bringing the prop bolts up to torque, that they weren't coming up to torque as quickly as they should.I noticed real quick that the front spinner bulkhead was deforming under the prop bolts. Are spinner bulkheads made of really soft aluminum or something? Material was actually squeezed out from under the bolts, which made the bulkhead bulge a little around the bolt holes.I'll try and post a pic later today.

In my mind, the solution to my problem would to be to use thicker washers, with a bigger diameter under thebolts, or to install a6 hole,.125" thick aluminum plateunder theboltheads, so that the front bulkhead will be clamped moreevenly.

So...is this a typical problem to have? This is the first spinner that I have ever cut and installed and my problem couldjust be from my ignorance. Or, is my spinner bulkhead defective in some way.

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