What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

New Catto prop - stack crush plates?

P

prkaye

Well Known Member
I just received my new Catto prop (with nickel edges). This is to replace my Catto prop I got about 4 years ago. The new prop is thinner, and they supplied a retrofit crush-plate to make up the difference. I plan to go out to the hangar this weekend to do the prop swap. My question for any other Catto customers who have done this - will I be stacking the two crush plates (my old one and the new one), or just replacing the old one with the new one?
I'm asking here because I think Catto has closed for the day (for the week), and I'd like to install the new prop this weekend.
Thanks!
 
Phil,
I replaced a thick steel crushplate with 2 aluminum crush plates from Saber in order to take some of the weight off my nose. Saber recommended stacking the two aluminum plates together (equalling the thickness of the original steel crushplate) so that I could use my existing (expensive) prop bolts. So, according to Saber, I guess the answer to your question would be yes. Hope this helps.
 
Last edited:
Derek has a good point. You will probably need to put the Catto-supplied crush plate aft of the forward spinner bulkhead so that your spinner still fits. Your original crush plate would then go forward of the fwd spinner bulkhead. Either way, your existing bolts should work so long as the combined thickness of the new prop + catto supplied crushplate = the thickness of your original prop.
 
The thicker crush plate (5/8") was supplied by Catto with the new prop precisely so that I could use my existing prop bolts and spinner. This is what they do for customers like me who are replacing one of the older (thicker) 3-blade props with the new thinner prop. The thicker crush plate is supposed to compensate for the thinner hub of the newer props.
According to my old and new invoices, the old prop thickness was 4.375 and the new prop is 3.75. This is a difference of exactly .625 = 5/8. So, by the arithmetic, I will need to use both crush plates to get the equivalent overall setup I now have.
You will probably need to put the Catto-supplied crush plate aft of the forward spinner bulkhead so that your spinner still fits. Your original crush plate would then go forward of the fwd spinner bulkhead.
Click to expand...
This sounds right to me. Maybe there's some instructions or notes hidden in the prop box... I only peeked inside today - I'll look for notes when I unpack it tomorrow.
Maybe this has been a silly question - I guess I only hesitated because, for an assembly that is so critical and that is spinning around at such high RPMs, it seems to me that one would want to avoid stacking-up any more discrete parts than necessary.
 
Last edited:
Crush plate

You may need the extra crush plate thickness to hold the front spinner bulkhead in the right place.
 
Catto Crush Plate

Phil

I did the same as you ( Replacing a Catto 3 bladded with a new Carbon fiber 3 blades ) and had to buy a new spinner because I sold the old one with the prop.

Once I received the crush plate from Saber ( Craig forgot to put it in the box ) I couldn't installed the spinner with the new crush plate, had to use the old thinner crush plate and the spinner fitted like a glove.

I never use a second crush plate in front of the forward bulkhead, is it a requirement??

Mine is a 12'' spinner installed on an RV-4..

Bruno
[email protected]
 
So it was as was speculated by others. It was pretty obvious once I got the spinner off and looked at things. The 5/8" crush plate goes behind the forward spinner bulkhead. This compensates for the fact that the new prop hub is 5/8" thinner than the old prop hub, and brings the spinner bulkhead properly into position. Then the old crush plate goes on the front of the forward spinner bulkhead, just like before.

The installation was actually pretty seamless - took less than an hour. Looks nice and flies just like my old prop.

I never use a second crush plate in front of the forward bulkhead, is it a requirement??
Click to expand...
Good question - I wondered this myself. So you just put the washers under the prop bolts right up against the spinner bulkhead? The only thing I wonder about is putting that much localized stress directly against the thin bulkhead material (those bolts are torqued to 38 ft lbs). The forward crush plate distributes that stress evenly throughout the whole spinner bulkhead. Also, the new prop is lighter, so the extra crush plate keeps my C of G roughly where it was before.

Question - with composite props I know (from experience) that the prop bolts have to be re-torqued after some initial amount of time... I guess the composite layup gets compressed a bit and sort of settles-in. How many hours of operation, or how many days/weeks of time should I wait before pulling that spinner, cutting the lockwire, and re-torquing those bolts. Do you think I'm safe to go 5-10 hours, say a month?
 
Last edited:
For a new wood prop, I like to recheck after 1st flight, then after maybe 3-5 hrs. After that, the next time the cowl's off/annual.

I do it after 1st flight to verify that everything 'seated' correctly on installation, and that there's no defects that were hidden during installation.

In 20+ years of flying wood props, I've never seen torque change after the 5 hr mark, and I live in the deep south, where humidity varies from sometimes 20% or less in winter to swimming levels in summer.

FWIW,

Charlie
 
alpinelakespilot2000 said:
Phil,
I replaced a thick steel crushplate with 2 aluminum crush plates from Saber in order to take some of the weight off my nose. Saber recommended stacking the two aluminum plates together (equalling the thickness of the original steel crushplate) so that I could use my existing (expensive) prop bolts. So, according to Saber, I guess the answer to your question would be yes. Hope this helps.
Click to expand...

Any idea of the weight differerance between the aluminum vs steel crushplate of the same thickness?

Just curious as I really need to add some weight on the nose to offset the aft cg. I've been flying 8 years & when I converted from the A model to Taildragger, my cg went further aft.
 
DanLandry said:
Any idea of the weight differerance between the aluminum vs steel crushplate of the same thickness?

Just curious as I really need to add some weight on the nose to offset the aft cg. I've been flying 8 years & when I converted from the A model to Taildragger, my cg went further aft.
Click to expand...

4130 steel is 2.83 times heavier than the equiv. volume of of 2024-T3 alum.
You could also have a custom crush plate made that was thicker than needed, with counter bores at the bolt locations big enough for a socket.... it's probably the best way to add weight to the front of an RV.
 
Everyone needs to be REAL careful with the Catto installs. There is a BIG difference from Gen 1 to Gen 3. Call for advise.
 
rvbuilder2002 said:
4130 steel is 2.83 times heavier than the equiv. volume of of 2024-T3 alum.
You could also have a custom crush plate made that was thicker than needed, with counter bores at the bolt locations big enough for a socket.... it's probably the best way to add weight to the front of an RV.
Click to expand...

Wow! Never thought about that.
Is this something that Saber can build?
Thanks for the info.

You can send me a PM so I don't totally hijack this thread. But, I do think other catto players might be interested,
 
DanLandry said:
Wow! Never thought about that.
Is this something that Saber can build?
Thanks for the info.

You can send me a PM so I don't totally hijack this thread. But, I do think other catto players might be interested,
Click to expand...
Yes. Saber stocks ~19# steel crush plates. I started with one but found it gave me more fwd cg than needed so he gave me two aluminum ones totaling the same thickness (but about 15 # lighter) so that I could use my same bolts.
 
DanLandry said:
Wow! Never thought about that.
Is this something that Saber can build?
Click to expand...

Their web site says....

CRUSH PLATES - 6" dia. x 3/8" thick-- $50 7x3/8-- $62 7x1/2-- $72
Other thicknesses available.

So it sounds like they could make what you want, though it appears that their standard is to make parts out of 2024-T3 alum. Give them a call, they might do custom work.
 
Saber made me a 22# steel crush plate back in 2007, I was told he only deals with aluminum these days. Guess it wouldn't hurt to call and beg. :eek:
 
LifeofReiley said:
Saber made me a 22# steel crush plate back in 2007, I was told he only deals with aluminum these days. Guess it wouldn't hurt to call and beg. :eek:
Click to expand...

I talked to saber today & ordered a 20# steel crush plate?
Looks like it's become the standard when swinging a catto.
Unfortunately, I also had to purchase new prop bolts.

Anyone in the market for the aluminum plate with bolts?
 
DanLandry said:
I talked to saber today & ordered a 20# steel crush plate?
Looks like it's become the standard when swinging a catto.
Unfortunately, I also had to purchase new prop bolts.

Anyone in the market for the aluminum plate with bolts?
Click to expand...

Just a heads up for anyone considering this setup.
I had to return the 20# crush plate.
I have the older style 2 1/4 prop extension that does not attach directly to the crank flange. Therefore, the 20# crush plate would have had to be attached with an AN8*92 prop bolt which is not recommended. The 20# crush plate needs to bolt onto the Saber prop extension which then attaches to the crank flange. This uses 2 sets of prop bolts
 
Yes, you do need the Saber Extension. Sorry it will not work for you. So you did not want to just order one of his extensions and move forward?
 
LifeofReiley said:
Yes, you do need the Saber Extension. Sorry it will not work for you. So you did not want to just order one of his extensions and move forward?
Click to expand...

It was another $400 plus the $294 for the new crush plate/bolts.
I may look at other options. I've been considering a complete upgrade to the newer catto prop.
I may opt to sell my old setup & go with new. Now, would be the right time to do so.
 
just in case someone is searching for answers like I was...

I also needed the 5/8" crush plate with the 'Gen 3' prop. I had to put it behind the front bulkhead, next to the prop to make the spinner bulkheads fit correctly.. so I hope the bolts / washers in just the front bulkhead are ok..no front crush plate forward of front bulkhead..


so flange, 2 1/4 spacer, rear bulkhead, prop, 5/8" crush, front bulkhead.

Those were the advice of Catto/Sabre.. and Catto was VERY helpful on shipping me the correct parts when I received the wrong ones at OSH..
 
Andy, that's exactly how I'm flying mine. It's been ok for about 75 hours now since I got this prop.

At the time, Sam at Saber said I could either put the bolts/washers right up against the front bulkhead or he could make me a 1/8" or 1/4" spacer to be more resistant to possibly damaging the front bulkhead with bolt torque. The same bolts could be used either way. I elected the cheaper option and so far it's been ok. Will be keeping an eye on the front bulkhead for signs of damage from the washers bearing directly on it.

What a great propeller though!
 
Thanks Kurt.. was just reading the instructions for spinner.. and it said put the bulkhead under the crush plate.. good to know it will work this way with the bolts/washers on the bulkhead itself..!
 
You must log in or register to reply here.
Back
Top