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Fitting Front Spinner Bulkhead

dbaflyer

Well Known Member
I have an RV9, O-320, Fixed Pitch Catto 3 Blade. It has the 2.25 inch spacer and 5/8 inch crush plate. I mounted the crush plate against the propellor and the forward bulkhead forward of that. I marked the outline of the bulkhead on the spinner as it was positioned on the airplane. When I take it apart and see where the forward bulkhead sits flush against the inside of the spinner it lies about 12/32nds forward of where it is actually going to lie. In order to have it sit flush were it actually goes would require about 1/8 in of additional fiberglass layup on the inside of the spinner. Is this pretty normal? I've read where you need to ensure this space is tight, but I was never thinking 1/8 inch.

In this photo you can see where I marked the aft edge as it was mounted and where it actually sits flush against the inside of the spinner.

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A lot of energy is "stored" in the spinner. I've known of two (other designs) spinners to depart in flight. You don't want to go there.

Adding 1/8" to the ID is problematical for several reasons,

Can you add a spacer to the front so you move the bulkhead forward?

mjb
 
If I recall correctly, I had a similar problem. I called Craig Catto, and he said to move the crush plate ahead of the front spinner bulkhead. I recall both Craig and Sam at Saber saying that was OK. Anyway, it cured most of my misalignment issue. The remaining "looseness" was solved by putting a couple of layers of FG where the front bulkhead screws were.
I admit my memory on this is a tad short of all the details ...
 
Moving the crush plate forward is going to move the bulkhead further aft causing it to be worse. I also received instructions from Catto to put the crush plate against the prop. Many people have used this prop and engine so there must be some kind(s) of resolution.

Maybe I have the wrong spinner?

Moving the entire spinner further aft is not an option either as the rear bulkhead just fits the inside of the aft edge of the spinner.

Why is adding fiberglass to the inside of the spinner problematic? In order to move the bulkhead forward enough the spacer would have to be 3/8 inch thick. That is a really larger spacer.
 
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Why not just use spacers between the prop dome and the front bulkhead. Then you won't unbalance or put a wobble in your spinner.
 
FWIW, the spacer thickness (behind the prop) should make no difference on where the front bulkhead falls. But prop thickness will. IIRC, there's a specific prop thickness that will place the front bulkhead in the right spot for a snug fit. (4 1/4" ?? Been a while since I fitted one, but they all wanted to be in the same spot.) If you call Van's, they can tell you for sure what the right thickness is, then you can use a stackup of crushplates to match that total measurement. ex: if your prop is 3 1/2" thick & Van expects a 4 1/4" prop, you'd need 3/4" of crushplate between the prop & the bulkhead.

As many props as Catto sells, I would have thought he would either match Van's expected thickness, or supply crushplate thickness as needed, or supply a spinner that fits.

The hazard of adding material to the inside of the spinner to fill the gap between bulkhead & spinner, is that it's pretty hard to keep the spinner perfectly balanced, centered, and fully supported all the way around the bulkhead. Missing any of those targets can result in losing the spinner (which can result in losing a prop, or canopy, or...).

Charlie
 
I recommend you call Craig Catto and ask about the misalignment issue. Between he and Sam at Sabre, they've seen about every situation possible.

Thinking more about it, I think they recommended ( and I followed thru) adding a 1/8" spacer plate ..... Same diameter and bolt pattern as the crush plate. Even though I just removed and retorqued my prop in April , I cannot recall the exact parts in there nor the order they're installed in, but it has been trouble free over 300 hrs. :)
 
RV-3 is missing forward bulkhead - sources?

My 22 y/o RV3 is missing the forward bulkhead. It appears Vans has stopped making them. I would prefer not to make one so anyone know of an alternate source?
 
My issue ended up being the size of the crush plate. I initially received a 3/8 with my propellor, but it really needed to be 5/8.
 
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