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Old 07-09-2018, 11:15 AM
jacksel jacksel is offline
Join Date: Jul 2005
Posts: 108
Default Difficulty fitting spinner after prop repair

I have a Hartzell C/S on my RV-6. After 14 years and 800 hours it started seeping grease out a small section of the hub split. I sent it in for inspection and repair, and when I put it back on the airplane the front plate holes didn't line up with the corresponding holes in the spinner (~1/4" off). Is this a normal potential consequence of disassembly and reassembly of the prop? A mechanic friend of mine told me the 4 holes attaching the front plate to the prop are usually elongated (more like curved slots), allowing some rotation of the front plate before it is tightened in.
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Old 07-09-2018, 11:37 AM
Ironflight's Avatar
Ironflight Ironflight is offline
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Join Date: Jan 2005
Location: Dayton, NV
Posts: 11,763

Yes, this is normal. The front cylinder doesn’t always end up at exactly the same spot when the prop is re-assembled. I have never slotted the bolt holes - have either made a new bulkhead or if the offset is far enough, mounted new nutplates.

Paul F. Dye
Editor in Chief - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
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Old 07-09-2018, 11:44 AM
jacksel jacksel is offline
Join Date: Jul 2005
Posts: 108

Thank you Paul.

John Walsh
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Old 07-09-2018, 11:44 AM
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Dale D Dale D is online now
Join Date: Aug 2017
Location: Zeeland, MI
Posts: 21
Default Elongate the Front Plate Holes

I just went through this same experience with my RV-9a and Hartzell C/S prop a couple of months ago.
My prop was resealed by a reputable prop shop. When they reassembled the front hub to the specified torque, the front spinner plate holes no longer matched the spinner's holes. They were off by 1/4" - 3/8".

As a side note, the prop shop told me that those 4 threaded prop hub holes were originally intended for assembly/disassembly. Vans conveniently uses them for the front spinner plate.

The solution was to create a template with curved, slightly elongated holes where the 4 bolts mount through the front plate. Remember, if you are off by 1/4" on the perimeter of the front plate, it won't take much near the mounting holes to achieve this.

I actually drew up my template in AutoCAD to make an accurate template of the elongated holes. I then taped the template to the front plate. Then, I took a Dremel tool and appropriate bits to slowly and carefully elongate each of the 4 holes, according to my template. I finished the the holes by lightly filing them smooth with round files.

If you would like any help developing an accurate pattern with CAD, just PM me. I would be glad to help.

Dale DeWeese
RV-9A Owner
EAA Chapter 211 Member
Zeeland, MI (Z98)
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Old 07-09-2018, 09:05 PM
jacksel jacksel is offline
Join Date: Jul 2005
Posts: 108

Thank you Dale. I actually hadn't thought of that geometric relationship between the screw holes and the plate attach bolts. Makes sense. If the holes are off by ~3/8" then the elongation required at the bolt holes is considerably less.

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Old 07-09-2018, 09:25 PM
Ralph Inkster Ralph Inkster is offline
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 465

Much easier to mount front plate 90 degrees from original position and remark new hole positions thru the spinner screw holes, followed with drilling & mounting new nutplates. This will insure that plate and spinner stay true.

I'd worry about maintaining true centerline if elongated holes were used.
Maintain lots, upgraded - repaired - & modified more, rebuild a few, & built some too.
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Old 07-09-2018, 09:48 PM
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JonJay JonJay is offline
Join Date: Jan 2007
Location: Battleground
Posts: 4,064

I just drew three large circles on the bulkhead, center line bisecting the existing holes, inner line, outer line, drilled my new holes and used a rat tail file and filed to the lines to make an arc between the holes.
My spinner remained true. Not sure how it could get out of true at the front bulkhead. The backplate is pretty stiff and there are a lot of screws holding the spinner to it. You would have to force something, not even sure you could.

Mine where out about 1/4" final slot length.
It took no time at all to do this.
Smart People do Stupid things all the time. I know, I've seen me do'em.

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Last edited by JonJay : 07-09-2018 at 10:01 PM.
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