RV7 CS spinner bulkhead crack...carbon fiber?

turbosaaber · #1 11-04-2018, 03:27 PM

Well this is the second time my spinner bulkhead cracked. First I suspect was due to prop not being balanced...hartzell CS. Had prop balanced, compression test done, no pulses. One thing I did notice did not have enough clearance on the spinner cutout for the movement of the blades. Fixed that midway through the second bulkhead. Pulled the prop for belt change and saw cracks around two of the 4 mounting bolts for the prop. I'm at a loss here, did some quick internet research and seems like a carbon fiber spinner backplate will fix my problem. Any thoughts as I'm tired of pulling the prop? Spinner does track true.

Thanks,
Carl

turbosaaber · #2 11-04-2018, 03:32 PM

I see on Chris Z website N91cz had the same issue with his lancer and he fabricated a carbon fiber backplate which fixed the problem. I think he used an autoclave along with vacuum bagging but not sure. Anyone in that biz that can help?

Carl

FORANE · #3 11-04-2018, 04:54 PM

Carl

Chris Z is active on the Lancair forum and has a thread in WTS on that forum. I believe it is only visible to forum members so I will post a redacted version of his post here:
WTS Lancair 320/360 Carbon Backplate and Spinner

These are made of high temperature epoxy cured at 350 deg F and 150 psi. Precision milled bolt and hub pattern fits the Hartzell compact hub.

Light Weight Carbon Spinners also available.
(includes section to back fill behind blades)

You might contact him if you have not done so. I have also suffered issues of cracking with aluminum spinners. Zero issues for me since going composite.

turbosaaber · #4 11-04-2018, 04:58 PM

Thank you so much! I sent Chris a pm but I know he is not too active here and it was only hours ago. Thanks again...hopefully we will get this fixed.

carl

Walt · #5 11-04-2018, 05:30 PM

Quote:

Originally Posted by turbosaaber

Well this is the second time my spinner bulkhead cracked. First I suspect was due to prop not being balanced...hartzell CS. Had prop balanced, compression test done, no pulses. One thing I did notice did not have enough clearance on the spinner cutout for the movement of the blades. Fixed that midway through the second bulkhead. Pulled the prop for belt change and saw cracks around two of the 4 mounting bolts for the prop. I'm at a loss here, did some quick internet research and seems like a carbon fiber spinner backplate will fix my problem. Any thoughts as I'm tired of pulling the prop? Spinner does track true.

Thanks,
Carl

Thousands of RV's flying without this issue, I would suggest you look for the root cause of the problem rather than looking for a band aid fix to mask the the issue.

turbosaaber · #6 11-04-2018, 05:43 PM

Thank you Walt very true statement and good advice.

I believe the problem which led to two failures was the blade to spinner clearance was not adequate causing the spinner to wobble putting stress on the backplate. Since then the blade to spinner was opened up which I believe solved my problem but the damage was already done.

Walt · #7 11-04-2018, 05:46 PM

Quote:

Originally Posted by turbosaaber

Thank you Walt very true statement and good advice.

I believe the problem which led to two failures was the blade to spinner clearance was not adequate causing the spinner to wobble putting stress on the backplate. Since then the blade to spinner was opened up which I believe solved my problem but the damage was already done.

You should definately inspect the prop shank for damage, Hartzell allows zero damage in the blade root area.
If you're certain this was the issue than by far the simplest repair would to be make and install a new spinner and mount.

turbosaaber · #8 11-04-2018, 05:49 PM

IO-360-a1b6. Had a little vibration 2400 20-24". Since the clearance increased no vibration. Vans spinner with forward and aft bulkheads aft having a doubler. Nuts not bottomed out, plenty of threads showing. Luckily no damage in the blade root area. when I clearance the spinner I called hartzell about the problem and they gave me a template which I recommend to all.

RV7A Flyer · #9 11-04-2018, 10:47 PM

Quote:

Originally Posted by turbosaaber

saw cracks around two of the 4 mounting bolts for the prop.

I'd look at two things right off: proper deburring of the holes in the backplate to eliminate stress risers, and torque on the bolts/nuts.

Timberwolf · #10 11-05-2018, 05:13 AM

I had my back late crack recently and after looking at what was the root cause and allowing the backplate to flex, I discovered there were no screws in the front bulkhead. I cut out a new piece and riveted it in, along with adding fasteners to the front bulkhead and haven?t seen any further issues. I?m with Walt in that there?s thousands of these setups, what makes yours/mine so special when these issues are otherwise unheard of?