Washers on Vans spinner

Blain · #1 05-31-2016, 10:42 PM

RV-8, Sensenich FP, Vans spinner. Quick search doesn't return any recent threads on the topic.

Vans says use a 2" diameter washer under bolt head and trim them to clear spinner bulkhead. I have a set of these from another builder. It just doesn't seem like the thing to do. An email to Sensenich got me "Do what Vans recommends".

The only reason I can see to use this size washer is for the increased clamping area on the forward bulkhead.

As usual I may be over thinking it but I find a couple of drawbacks to this.

The trimmed washer will still turn when applying final torque until it hits the step in the spinner. Seems like that will create a stress zone.

Another issue which is probably easy to cure is the imbalance between the weight of the trimmed washers. I found 0.1 OZ difference. Even though they have a short arm to the center of rotation it must contribute to a harmonic imbalance.

Then the stack weighs 7.4 OZ, standard diameter washers only 1.8 OZ. that is rotating mass about as far forward as you can get.

I've learned over the coarse of this build what looks improper usually has a reason. Am I missing something?

Lycosaurus · #2 06-01-2016, 06:05 AM

Quote:

Originally Posted by Blain

RV-8, Sensenich FP, Vans spinner. Quick search doesn't return any recent threads on the topic.

Vans says use a 2" diameter washer under bolt head and trim them to clear spinner bulkhead. I have a set of these from another builder. It just doesn't seem like the thing to do. An email to Sensenich got me "Do what Vans recommends".

I don't recall the 2" diameter washers being recommended for the prop/spinner bulkhead by Vans. Is this some new recommendation or did I miss it? I have followed Sensenich install and used their recommended washers.
http://www.sensenich.com/files/docum...1261679442.pdf

All good for last 8 years and over 700 hours.

bret · #3 06-01-2016, 07:45 AM

On the subject of spinners, what is everyone using for the FG spinner to bulkheads, pan head, or tinnerman?

Carl Froehlich · #4 06-01-2016, 07:53 AM

Quote:

Originally Posted by bret

On the subject of spinners, what is everyone using for the FG spinner to bulkheads, pan head, or tinnerman?

On the rear bulkhead #8 flush screws with #8 tinnermans. On the forward bulkhead #8 flush screws with #6 tinnermnans drilled out to fit the #8 screw. The reason is the radius of the forward bulkhead is much less so I like the look of the smaller tinnerman on for those screws.

Carl

Auburntsts · #5 06-01-2016, 07:56 AM

Quote:

Originally Posted by bret

On the subject of spinners, what is everyone using for the FG spinner to bulkheads, pan head, or tinnerman?

I used a standard AN526 truss head machine screw with a nylon washer as called out in my plans (I say that because I don't know if every RV model has the same hardware call out). No issues so far.

IowaRV9Dreamer · #6 06-01-2016, 08:20 AM

My drawing C4 shows AN970 washers for the metal prop. No note about trimming them that I can see. They look round in the drawing. The drawing says it applies to "ALL RV's"

boom3 · #7 06-01-2016, 08:26 AM

I trimmed the washers just like the picture in the original post. Still looks great after 725 hours. (just recently inspected again during annual)

I thought it seemed a little goofy too but went with it.

reak · #8 06-01-2016, 08:45 AM

Hello Blain, to bring this thread more in line with the orginal question, I had the same problem with the washers being way to large. I also tried trimming them as you did. Trimming doesn't work; as the bolt is torqued the washer turns and creates a huge dent in the backplate when the corner of the washer meets the rise and n the backplate. My solution was to buy smaller AN fender washers and ream the hole to fit the bolt. I've forgotten, but I think I had to go down 2 sizes. This worked well.

aerhed · #9 06-01-2016, 09:45 AM

If you're thinking about flush screws and tinnermans, your spinner has to be thick enough that the tinnermans can't bottom out. If they contact the bulkheads the holes will vibe out.

Steve Melton · #10 06-01-2016, 09:56 AM

Quote:

Originally Posted by Blain

RV-8, Sensenich FP, Vans spinner. Quick search doesn't return any recent threads on the topic.

Vans says use a 2" diameter washer under bolt head and trim them to clear spinner bulkhead. I have a set of these from another builder. It just doesn't seem like the thing to do. An email to Sensenich got me "Do what Vans recommends".

The only reason I can see to use this size washer is for the increased clamping area on the forward bulkhead.

As usual I may be over thinking it but I find a couple of drawbacks to this.

The trimmed washer will still turn when applying final torque until it hits the step in the spinner. Seems like that will create a stress zone.

Another issue which is probably easy to cure is the imbalance between the weight of the trimmed washers. I found 0.1 OZ difference. Even though they have a short arm to the center of rotation it must contribute to a harmonic imbalance.

Then the stack weighs 7.4 OZ, standard diameter washers only 1.8 OZ. that is rotating mass about as far forward as you can get.

I've learned over the coarse of this build what looks improper usually has a reason. Am I missing something?

that looks goofy to me.