Once I got the rough spinner from Catto, next task was to make the prop cutouts and screw holes. One of the reasons of my spinner replacement was improper tracking so I really wanted to emphasize on a precise tracking for this new one.
I found this interesting article on the EAA website on spinners. It explains how to make a blade cut-out template. I did try a few ways of making a template by using cardboard or scrap aluminum but I found it difficult to make an accurate and easy to use template on top of this double-curved surface.
The old spinner had the same diameter and length as the new one. The shape looked very similar so I tried using a piece of the old fiberglass spinner to make a blade cut-out template. I used a dremel with a thin cutting disk for all the rough cutting, including in the carbon fiber for the cutouts described later on.
When putting the piece on top of the new spinner surface, it did match the shape pretty well. I therefore decided to use it as my template material. I used my cardboard template attempt to trace the rough lines on the fiberglass template:
The curved line above shows the actual shape of the back end surface of the prop. It became clear that cutting this shape would make the spinner impossible to install, so I thought a line parallel to the forward cut was a good compromise.
Then a rather long iterative process began. With the new spinner aft bulkhead, prop and old spinner forward bulkhead installed on the engine, I made gradual adjustments to the template until reaching a cut-out with a 1/8 inch prop clearance. I could firmly hold the template against the bulkheads using side grip clamps and Cleco pins. I used a Sharpie pen to mark the areas where material removal was needed. Then to remove material I used a curved file and most importantly, patience.
After 2 hours of back-and-forth, I finally ended up with a template I was happy with. The picture below shows the template on top of the new spinner:
I used the template to mark both cutouts on the new spinner using a fine point pen. Then I carefully cut offset cutouts with the Dremel and then refined the cutout to match the lines using a file. When trying to fit the new spinner in place, I realized the centering dowel was preventing the spinner to fully get in its position. I initially thought it was just long enough to fit in the prop crushplate. It was in fact longer than that and designed to get also into the prop hub. My Prince prop having only a 1 inch diameter center hole vs the 2.25 inch dowel diameter, I had to find an alternative. After a confirmation call with the friendly staff at Catto, I decided to shorten the dowel to ensure the spinner could slide all the way aft until reaching the bulkhead, while still performing its self-centering in the crushplate:
This allowed me to get a final fit on the airplane. I did have to make very small adjustments to the cutouts, probably due to the effect of the template thickness, but nothing compared to the making of the template itself.
For tracking, I simply used a piece of MDF wood clamped on a trestle as a ground reference. As recommended in the EAA article, I removed one spark plug per cylinder to freely rotate the prop. The centering dowel made the tracking exercise fairly easy. Only had to make small adjustments to find the symmetrical position and mark crew holes:
I was then ready for clear coat! I could have painted it black like the old spinner, but I thought a clear coat on carbon fiber was going to make a good match with the CF weaves on the Prince prop.
Since I hate painting, I sent the spinner to a good paint shop. Really anxious to get it back!
Stay tuned for the final look and final weight numbers.
