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E-Props / Cowl - Spinner Centering


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E-Prop arrived this week - very pleased with appearance and everything about it.  I've been thinking the engine needs to be centered up prior to installing, knowing the comments about overlap & clearance concerns.  My spinner was not too far off, but enough to want to dial it in, as well as looking for that performance gain along with the prop.  I didn't want to simply guess and stab at this, here's how to calculate adjustments, and it resulted spot on first shot.

Step 1, measure the offset at four locations top / bottom / right / left, use a consistent reference point on the spinner, rotating it around to each point.  My current Neuform was not concentric which would be noise in determining centerline shift required.  Ultimately I needed 6mm to passenger side, and 4mm up.

The engine mount will likely have some amount of distortion in the installed state, depending on how many washers are currently installed and who's done what reassembling after past hose changes.  Mine had 4 washers at top, 3 in middle, and 4 at bottom.  Work from your current washer situation, don't just blow it all apart, this preserves the "baseline distortion" leading to the current location of spinner.

Here's a representation of the mount and some numbers to reference in next step:


The upper two mounts are primary for adjusting R & L, needing 6mm and the space of 30" being further than the spinner is projected out front, equals .883 movement at spinner for every 1mm of movement at mount.  So, 4 washers = ~ 7.2mm, * .833 = 5.997mm at spinner.  Knowing the next step requiring up adjustment will need either adding washers at bottom, or removing washers at top, I decided to remove 3 from the 4 to work with on R, (need to keep min of 1 washer) and then would only have to add 1 on the L to develop a shift of 4 washers in height.  Buttoned up the cowl and had R&L moved perfectly, rechecked the up/down adjustment as the top of mount did come in a bit, but it was still about 4mm needed. 

On to the bottom.  Jacked & supported under fuse to take weight off nose.  Loosened all 4 lower fasteners.   1 washer results in more movement at spinner than thickness as these are closer to centerline, washer at the mid mount creates 1.8 * 1.786 = 3.215, I figured that is close enough to 4 and liked idea of not having to adjust much at bottom due to rudder cable tension.  Slipped in 1 washer each location and tightened everything up.   I will adjust rod ends the thickness of washer and have tension in theory back to the starting point.

Cowl back on and spinner is about 1mm less at top, as calculated, darn near perfection.

This was not as difficult as I thought it might be.  About two hours of shop time, but I still need to reinstall the gascolator, that blocks lower L mount bolt.

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