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Fitting spinner to front and aft bulkheads

Draker

Well Known Member
Kind of scratching my head at this one. Has anyone encountered an incorrectly sized spinner cone from Vans? Quoth the plans:

Before installing the S-602-1 and S-605 (or S-605SEN) spinner mount plates to the prop, fit them to the spinner. This will verify that the prop hub thickness corresponds to the relative diameters of the mount plates. [...] When both the front and rear plates are aligned with the spinner and with each other, the distance between them will be the required thickness of the prop hub.

OK, so I'll measure the prop hub first. The distance between the aft side of the front bulkhead and the aft edge of the aft bulkhead is exactly 9" on my (Hartzell CS) prop:

i-nDs28NS-L.jpg


Now, I take off the front bulkhead and position it inside Vans spinner cone so that it is exactly perpendicular to the centerline of the cone. Measure the distance between the aft side of the front bulkhead to the plane of the spinner cone edge. Oh, no, it's 9-1/4":

i-gD5bPBf-L.jpg


To verify this, when I mount the cone over the bulkheads attached to the prop, the cone is exactly 1/4" too long.

i-QDsBv4C-L.jpg


Vans:

If the distance is greater than the thickness of your prop hub, spacers may be installed between the front plate and the forward surface of the prop. These spacers are available through Van's Accessories Catalog.

Sounds like I might need 1/4" of these spacers. But, wait: Van's spinner drawing describes building up a few layers of fiberglass to make up for small gaps. Breaking out the trigonometry, given the spinner cone angle in that location, I would need to add about 7/64" of fiberglass to the inside of the spinner to make the bulkhead snug. That seems to be a lot of lumpy weight to add to the fastest-moving piece of the airplane. I suppose I could also carefully trim 1/4" off the aft end of the spinner cone, too.

If you also encountered this, what did you do?

  1. Get 1/4" spacers (part #??) and longer attach bolts for the front bulkhead
  2. Carefully lay up 7/64" of fiberglass inside the spinner cone
  3. Trim 1/4" off the aft end of the cone
  4. Any other options???
 
I just trimmed it. I fit it to the bulkheads first, then took everything apart. I attached only the rear bulk head to the spinner and mark it with a sharpie and cut it carefully. So far so good. The important thing is that its mounted straight and it makes good contact with the bulkheads.
 
While mine was no where near 1/4" too long I trimmed the aft end of my spinner as well. Is your cowl already done? If so, trimming may be your only option as adding spacers would closeup the spinner to cowl gap too much.
 
Yup, cowl is already fit. 1/4" from the aft edge of the aft spinner bulkhead.

Wouldn't spacers bring the front bulkhead forward, not move the aft bulkhead backward?
 
The instructions you referenced are only pertinent to installations on a fixed pitch propeller.
Because there is no industry standard for hub thickness, some propellers require the use of spacers on the fwd face to get proper spacing for the spinner bulkheads.
 
Yup, cowl is already fit. 1/4" from the aft edge of the aft spinner bulkhead.

Wouldn't spacers bring the front bulkhead forward, not move the aft bulkhead backward?

Ah yes, I was thinking of the spacers on the aft bulkhead. Does the Hartzell manual have anything about putting spacers on the fwd one? I find their installation manual to be pretty good.
 
Yup, cowl is already fit. 1/4" from the aft edge of the aft spinner bulkhead.

To clarify...ignoring the length of the thing, are you saying that you can't get it to snugly fit both foreward and aft bulkheads at the same time (again *ignoring* any "extra" spinner or overhang on the aft end, past the aft bulkhead)?
 
To clarify...ignoring the length of the thing, are you saying that you can't get it to snugly fit both foreward and aft bulkheads at the same time (again *ignoring* any "extra" spinner or overhang on the aft end, past the aft bulkhead)?

What I'm saying is: when the front bulkhead snugly fits against the inside the cone, and the aft bulkhead fits snugly inside the cone, the cone aft edge then extends 1/4" past the flange of the aft bulkhead (towards the cowl). I think all I need to do is trim the cone here, but Vans plans recommend using a spacer to "make" the prop hub match the length of the cone. Is the length of the cone as-shipped from Vans that critical? Maybe it's time to ask the mother ship.
 
What I'm saying is: when the front bulkhead snugly fits against the inside the cone, and the aft bulkhead fits snugly inside the cone, the cone aft edge then extends 1/4" past the flange of the aft bulkhead (towards the cowl). I think all I need to do is trim the cone here, but Vans plans recommend using a spacer to "make" the prop hub match the length of the cone. Is the length of the cone as-shipped from Vans that critical? Maybe it's time to ask the mother ship.

If it fits the front and rear bulkheads snugly, and it fits straight (check with a dial indicator while turning the engine), then just fit it temporarily (as described above...yeah, you'll have to remove the rear bulkhead one more time) and sand down the aft edge of the spinner to match the bulkhead flange. Easy peasy. No need to build any fiberglass up or anything like that.

You're lucky...mine was just a tad *short*, necessitating sanding the inside of the spinner so that the front bulkhead could slide further into the spinner.
 
This should have been your first clue that you were going a bit astray:

Before installing the S-602-1 and S-605 (or S-605SEN) spinner mount plates to the prop

A constant-speed prop doesn't use an S-605 mount plate. It uses an S-603.
 
This should have been your first clue that you were going a bit astray:

A constant-speed prop doesn't use an S-605 mount plate. It uses an S-603.

Ahhh, yes, Scott also pointed that out above: The spinner fitting plans apparently only describe the procedure for fixed pitch metal prop:

The following instructions describe mounting the spinner on a fixed pitch propeller. If you are installing a Sensenich fixed-pitch metal prop, use the appropriate front plate.

I suppose I guessed (incorrectly) that most of the instructions were also applicable to other props. I'll need to look elsewhere for the Hartzell CS prop spinner procedure, maybe Hartzell's documentation.
 
Ahhh, yes, Scott also pointed that out above: The spinner fitting plans apparently only describe the procedure for fixed pitch metal prop:

The following instructions describe mounting the spinner on a fixed pitch propeller. If you are installing a Sensenich fixed-pitch metal prop, use the appropriate front plate.

I suppose I guessed (incorrectly) that most of the instructions were also applicable to other props. I'll need to look elsewhere for the Hartzell CS prop spinner procedure, maybe Hartzell's documentation.

SPINNER INSTALLATION
Before installing the spinner, be sure you have the correct parts for YOUR propeller. Constant-speed, wood or fixed pitch metal propellers require different parts. On the constant-speed propeller, the back plate mounts to the hub of the prop and is reinforced with an aluminum ring. The front plate is a different size, as well. Follow the installation instructions included in the constant-speed spinner kit and DWG C4.

p. 12-6 of the Installation Manual

Then, there's a separate document entitled, unsurprisingly, "Installing a Spinner on a Constant Speed Propeller". But you've pretty much done everything it says before it reverts back to the main section in the build manual.

You're overthinking this. If it mounts solidly to both bulkheads and is straight, follow the instructions to mark and drill holes that you can put clecos in, pull it off, assemble off the hub and sand the aft edge to match. Then finish it up per the instructions with full-sized holes, platenuts, etc.
 
I bought my prop and spinner from Ed Wischmeyer here on the forums.:p Thanks Ed for already having the spinner and prop all made up already, saved me a bunch of time.

I hope to test fly this weekend or first part of next week, wx permitting.
 
p. 12-6 of the Installation Manual

Then, there's a separate document entitled, unsurprisingly, "Installing a Spinner on a Constant Speed Propeller". But you've pretty much done everything it says before it reverts back to the main section in the build manual.

Right, I went through that separate sheet--it basically stops before you touch the cone and punts you over to the fixed pitch instructions.

You're overthinking this. If it mounts solidly to both bulkheads and is straight, follow the instructions to mark and drill holes that you can put clecos in, pull it off, assemble off the hub and sand the aft edge to match. Then finish it up per the instructions with full-sized holes, platenuts, etc.

Got it. I guess I'm being paranoid about keeping this thing straight, accurate and balanced, given how important the prop is and how fast it rotates!
 
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