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RV7 CS spinner bulkhead crack...carbon fiber?

turbosaaber

Well Known Member
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
 
carbon fiber spinner backplate

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
 
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.
 
Chris z

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
 
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.
 
possible problem fixed

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.
 
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.
 
no loosing of screws or bolts.

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.
 
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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?
 
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?

Screws in the front bulkhead are not an absolute requirement. However, without screws, zero clearance between the bulkhead flange and the inside of the spinner is a must.

The problem seems to take two forms. The flange angle may not precisely match the spinner, and/or the spinner does not fit tightly against the flange at all 360 degrees. With screws, the screw heads will not be perpendicular to the spinner surface, or they will be pulling the fiberglass in when tight. To check, just start a long screw in the flange nutplate and eyeball it for 90 degrees to the spinner. Now eyeball a tight screw; any surface depression?

I've been running a "screwless" spinner about 830 hours now. Rear bulkhead is flat 0.100 6061 with axial screws from the rear, through a fiberglass flange added to the spinner. There are no front bulkhead screws. To ensure zero freeplay at the front bulkhead flange, the inside of the fitted spinner was sanded to be sure it was smooth, then shot with a few coats of PVA release agent. The front bulkhead flange was roughed up with some 120 grit, and a bead of proseal was applied. The spinner was then installed with rear screws tight. After time for cure, the spinner was removed and the excess proseal was cut along the flange edges. What remains is just a thin band of sealant on the flange, formed in place, which ensures zero gap or angle mismatch.
 
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No screws in fwd bulkhead

Also I do have a depression in a section of the aft spinner as dan describes so perhaps I should redo backplate and add screws up front too
 
I've been running a "screwless" spinner about 830 hours now. Rear bulkhead is flat 0.100 6061 with axial screws from the rear, through a fiberglass flange added to the spinner. There are no front bulkhead screws. To ensure zero freeplay at the front bulkhead flange, the inside of the fitted spinner was sanded to be sure it was smooth, then shot with a few coats of PVA release agent. The front bulkhead flange was roughed up with some 120 grit, and a bead of proseal was applied. The spinner was then installed with rear screws tight. After time for cure, the spinner was removed and the excess proseal was cut along the flange edges. What remains is just a thin band of sealant on the flange, formed in place, which ensures zero gap or angle mismatch.

Identical set-up, and no issues whatsoever. In fact, it's one of the parts of the build that I like most...600+ hours now, no problems. (Knock on wood).
 
Possible prop

Well I just looked inside the spinner and to d a bunch of prop grease built up by the blade. It?s an A hub so looks like the hub will need to be changed at the least. Might be a time to upgrade to a BA or other prop.

Thank you all for your thoughts and advise.
 
7k overhaul

Just talked to the prop shop near my house. Switch to a suffix b hub and overhaul 7k. Prop was overhauled 5 years ago. With vans price of 8k for a BA why would anyone overhaul a prop?
 
Just talked to the prop shop near my house. Switch to a suffix b hub and overhaul 7k. Prop was overhauled 5 years ago. With vans price of 8k for a BA why would anyone overhaul a prop?

Agreed but will Vans sell you a second prop at that price? Assuming that you purchased the original one from them, It's been said that they will only sell one per project? let us know what they say. Larry
 
Screws in the front bulkhead are not an absolute requirement. However, without screws, zero clearance between the bulkhead flange and the inside of the spinner is a must.

The problem seems to take two forms. The flange angle may not precisely match the spinner, and/or the spinner does not fit tightly against the flange at all 360 degrees. With screws, the screw heads will not be perpendicular to the spinner surface, or they will be pulling the fiberglass in when tight. To check, just start a long screw in the flange nutplate and eyeball it for 90 degrees to the spinner. Now eyeball a tight screw; any surface depression?

I've been running a "screwless" spinner about 830 hours now. Rear bulkhead is flat 0.100 6061 with axial screws from the rear, through a fiberglass flange added to the spinner. There are no front bulkhead screws. To ensure zero freeplay at the front bulkhead flange, the inside of the fitted spinner was sanded to be sure it was smooth, then shot with a few coats of PVA release agent. The front bulkhead flange was roughed up with some 120 grit, and a bead of proseal was applied. The spinner was then installed with rear screws tight. After time for cure, the spinner was removed and the excess proseal was cut along the flange edges. What remains is just a thin band of sealant on the flange, formed in place, which ensures zero gap or angle mismatch.

Until you spin it up.... I wonder how much the diameter of the spinner at that point grows at 2400 rpm? Probably doesn't matter, just wondering. There might be air in that gap when spun up.
 
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