plastic crush washers on spinner?

[eman1200]

been flying a '75 F for 8 years now with no washers of any kind on the spinner screws, using several different mechanics.  new mechanic just put plastic crush washers on them.  that seems......odd to me.  what say you all?  tcds doesn't say anything specific about it.  checking parts manual as we speak.....

[Hank]

I use Teflon washers under screws that go against paint, but it's difficult keeping them on the spinner--whenever I remove a screw, the washer seems to drop to the floor and roll away. And with a 3-blade prop, there's a LOT of screws on the spinner!

[KSMooniac]

It is good practice... protects the spinner finish from the frequent R&R of the screws, and I think helps absorb some of the vibration and reduce the chances of cracking.

[N201MKTurbo]

Because we have always done it.

Nylon is preferred over teflon. It is much tougher and doesn't cold flow as much.

[N201MKTurbo]

 

 

[Hank]

8 minutes ago, N201MKTurbo said:

Because we have always done it.

Nylon is preferred over teflon. It is much tougher and doesn't cold flow as much.

I used Teflon because they're cheaper, and because there's less friction than taking them out. Primarily to protect the paint . . .

[N201MKTurbo]

https://www.digikey.com/en/products/detail/keystone-electronics/3129/315866

[eman1200]

5 minutes ago, N201MKTurbo said:

 

 

 

TYVM.  I guess I'm just surprised 2 mooney service centers didn't feel the need to add them and I also wouldn't have thought you could tighten them up sufficiently with the washers.  I'll be less nervous now, thank you.

 

[47U]

8 minutes ago, eman1200 said:

I also wouldn't have thought you could tighten them up sufficiently with the washers.

Do not over-torque spinner screws.  Hand-snug, that’s it.

[Greg Ellis]

My C model has never had them in the 20 years I have owned it.  I looked in the maintenance manual and parts manual and cannot find anything that references the need for washers.  The image that @N201MKTurbo posted, what model Mooney is that for?  I found references to the spinner in the parts catalog for my airplane but no reference to the use of washers under the spinner screws.   

[philiplane]

cracking and corrosion are big problems with spinners. That's why fiber or nylon washers are used. To allow some relative movement and relieve stress. And to insulate the aluminum from the stainless steel, to prevent corrosion. While stainless itself doesn't corrode, it is always electrically active. When placed against bare aluminum, and exposed to water, it will form a corrosion cell. Nylon washers should be used under all stainless fasteners, or the screws should be installed using wet paint or primer. 

The same goes for carbon fiber spinners. They have to be isolated from bare aluminum and stainless steel.

Edited May 21 by philiplane

[eman1200]

12 minutes ago, philiplane said:

cracking and corrosion are big problems with spinners. That's why fiber or nylon washers are used. To allow some relative movement and relieve stress. And to insulate the aluminum from the stainless steel, to prevent corrosion. While stainless itself doesn't corrode, it is always electrically active. When placed against bare aluminum, and exposed to water, it will form a corrosion cell. Nylon washers should be used under all stainless fasteners, or the screws should be installed using wet paint or primer. 

The same goes for carbon fiber spinners. They have to be isolated from bare aluminum and stainless steel.

I would have thought the need for a snug fit would be more important for balance reasons.

[Aerodon]

Macfarlane supplies the at about $5 each:

 

https://www.mcfarlaneaviation.com/products/M1020-10/?q=spinner washers&search_type=product&index=6&page=1

[N201MKTurbo]

56 minutes ago, Aerodon said:

Macfarlane supplies the at about $5 each:

 

https://www.mcfarlaneaviation.com/products/M1020-10/?q=spinner washers&search_type=product&index=6&page=1

I think those are a gimmick, just use the nylon washers for Pennies each.

[N201MKTurbo]

1 hour ago, Greg Ellis said:

My C model has never had them in the 20 years I have owned it.  I looked in the maintenance manual and parts manual and cannot find anything that references the need for washers.  The image that @N201MKTurbo posted, what model Mooney is that for?  I found references to the spinner in the parts catalog for my airplane but no reference to the use of washers under the spinner screws.   

That was from the J manual.

[PT20J]

1 hour ago, 47U said:

Do not over-torque spinner screws.  Hand-snug, that’s it.

THIS^^^. Most people over tighten screws. The nutplates have an interference fit that retains the screws. Phillips screws cam out if over tightened..

[larryb]

They can also loosen up. Every couple of months I like to take a screw driver to them and make sure all are snug. On my previous Mooney I had a loose screw cause a lot of wear ruining the spinner. And the tightening order matters too.

[PT20J]

Nutplates wear out. If the screws lose torque, I might consider replacing the nutplates. 

[cliffy]

In the 70s I was flying a Navajo and we were cracking spinners left and right. Talked to Piper and when they

looked into it they said their fix was nylon washers under the screw heads.

Once we added them we didn't crack another spinner. back then.

We might have been the first to use then

[MB65E]

Extra Aircraft use the fiber washer on all of their screws. Their spinners are composite. I like the plastic washer idea on the metal spinner better than the fiber washer. 
While I like the fiber washers on the airplane, they do tend to wick dirt and the fresh look of the fiber washer goes away quickly. 
 

Thanks for the PN of the fiber washer. I would always order them from Germany, Extra wouldn’t list the PN. 

-Matt

Edited May 26 by MB65E

[Fly Boomer]

On 5/21/2025 at 7:31 AM, eman1200 said:

new mechanic just put plastic crush washers on them

Why are they called "crush" washers?  Mine don't appear to be crushed.  Maybe they were not adequately torqued?

[eman1200]

Why are they called "crush" washers?  Mine don't appear to be crushed.  Maybe they were not adequately torqued?

There are washers and there are crush washers, both metal and plastic/nylon. Some use metal crush washers with spark plugs that are meant to be, wait for it….crushed, and help form a seal and put pressure to prevent the plug (or bolt etc) from coming loose. I don’t think I said mine were crushed either, just that he used them when previously I had NO washers at all.

[Fly Boomer]

42 minutes ago, eman1200 said:

There are washers and there are crush washers, both metal and plastic/nylon. Some use metal crush washers with spark plugs that are meant to be, wait for it….crushed, and help form a seal and put pressure to prevent the plug (or bolt etc) from coming loose. I don’t think I said mine were crushed either, just that he used them when previously I had NO washers at all.

Good to know.  Thanks!