fiberglass spinner fitting

[Vince Frazier]

fiberglass spinner set

Things you’ll need:
dial indicator, resin, flox, nutplates, structural adhesive to glue the steel plates to the fiberglass, and screws, 1″ wide (or wider) HDPE tape, rivets, and the usual fiberglass and aircraft tools

Purpose:
Fit the spinner to the Hartzell (or other, YMMV) propeller without any wobble when finished

General procedure:

* Deburr the parts as needed.

* Maintain the relationship between the parts so that everything will go back into its own position for best fit.

* Refer to your Hartzell (or other) prop manual for general installation info. It should tell you things like how much fore and aft positioning is allowable, etc.

* Apply HDPE tape to the Hartzell prop dome circumference where the forward bulkhead will fit against it to prevent wear on the prop dome.

* Install the forward bulkhead on the prop dome. It should fit snugly, but not so tightly that you can’t remove the spinner assembly later. Sand the ID of the forward bulkhead if needed to obtain a snug fit.

* Using your dial indicator, check that the forward bulkhead is reasonably round and centered on the prop dome. You’ll bond it to the spinner later, so some minor slop is allowable.

* Using the Hartzell spinner bolts, which may not be the exact diameter as AN or hardware store bolts, check that they will fit in the steel plate and spinner backplate holes. Ream if needed for a snug fit.

* Center the spinner backplate and steel reinforcing plates on the prop hub. Use temporary bolts to hold it in place while you use the dial indicator to confirm that everything is centered properly. Make sure that the steel plates and the backplate will fit on the prop hub without rubbing. The bolt holes of the parts must align perfectly. Remove the parts and install the steel reinforcing plates to the aft side of the spinner backplate using adhesive and rivets. (Solid soft rivets won’t crush the fiberglass.)

* With the forward bulkhead and the spinner backplate in place, it’s time to install the spinner onto the assembly. This is where you realize that the untrimmed spinner won’t fit over the prop blades! So, carefully make some cardboard templates so that you can trim cutouts for the prop blades. Don’t forget to leave enough clearance for the blade pitch to change in flight. NOTE: Try to carefully cut out the fiberglass in one piece. You’ll want to trim those later and reinstall them to close up the bottom of the cutout.

* With the newly trimmed spinner in place on the hub/forward bulkhead/spinner bulkhead assembly, use your dial indicator to remove as much wobble as possible. A wobbly spinner looks bad, but it also wears out quicker and could contribute to vibration problems.

* Once the spinner is suitably centered and wobble free, drill 3/32″ holes through the spinner and backplate for the screws and nutplates that will hold everything in place. Put a cleco in each hole. You might also want to CAREFULLY drill about 4 holes in the front bulkhead so that you can reinstall it in the exact position later when gluing it. You can fill those holes later as they won’t need screws once the adhesive is set.

* Double check the whole thing for wobble and correct as needed.

* At this point, the forward bulkhead should have a snug fit and the spinner bulkhead should also have a snug fit. Both with no play detectable. If so, disassemble the parts so that you can rough up the forward bulkhead and spinner interior in order to bond the 2 parts together. Typically resin and flox is the desired adhesive, but there are other “modern” adhesives that could work too.

* Glue the forward bulkhead in place, remove any gross excess ooze and put the assembly back together so that the adhesive can cure. Make sure that the forward bulkhead is in the right position.

* Once the adhesive has set, you may work on trimming and fitting the fiberglass gap covers that will close up the hole between the prop blades and the spinner bulkhead. Leave enough room for the blades to change pitch in flight. These parts may be bonded, screwed, or riveted in place permanently. They normally don’t require removal later on.

* Prep the spinner parts for painting as you normally would other fiberglass parts, but minimize any filler added.

• This topic was modified 1 year, 1 month ago by Vince Frazier.
• This topic was modified 1 year, 1 month ago by Vince Frazier.

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