The NTX Pressure Recovery Spinner
Last updated 12-13-12


The NTX Spinner installed - a Berkut 13 exclusive, for now.


As you may remember, I almost lost my Catto race propeller during the 2009 Texoma 100 race in Texas. Long story short....when I landed, there were bits of propeller hub sticking out of the spinner cone opening. All but bolts 1 & 2 were only finger tight, the washers were loose, and the safety wire had actually loosened (yup, bolts had turned to the right). The heat generated by the friction severely damaged the prop hub, charred the wood core, and the burned away epoxy in the spinner bulkhead is quite evident. It was literally seconds from departure. Unlike another well researched failure, this was not a maintenance issue - I had installed the race prop/spinner and torqued the bolts the day before in preparation for the race. The propeller had raced before, but the spinner was brand new. Total flight time on the combo from install to failure was about an hour. I was very VERY lucky...and was able to have Craig Catto examine both the badly damaged propeller and spinner bulkhead. In talking to him, he mentioned another recent prop failure at Reno with a composite spinner bulkhead. It was both our opinions - This application is no place for room-temp cure epoxies!

Now, with 3 standard spinners either destroyed or on the shelf...I decided that the only spinner I would EVER put on Thirteen would be built specifically for this application...mean time, I HATED the look of the Berkut without a spinner. Some time later, I found myself working with high end pre-preg technologies and along side one of the world's most skilled composites craftsmen - Barry Koebernick. Blessed with knowledge and access to unmatched resources, I decided to commit to improving the status-quo technology, take advantage of the technologies available to me and build a "proper" spinner...one that can stand up to the task. The pressure recover spinner is well known and tested, so I wanted to stay with that basic shape. Barry and I began a laundry list of features that had to be included - high temp stable, structurally improved, smooth 'metal-like' bulkhead faces, reduced build time, optically true surface, lower maintenance, and a STUNNING appearance. OK...it was not as "easy" as Barry said it would be...but I was at least able to keep up. ;-) It all started with a new plug and a plan. The plan...well, it was to not only create the perfect spinner for Thirteen...but to possibly offer it to the canard community as well. After all, they need it too. It was specifically designed to install on a Lycoming 320/360/540 type with a SAE2/6 flanges and a 8" Saber extension with a harmonic balancer (optional) or a 6" extension without the balancer, with 3/8", 7/16" or 1/2" prop bolts.

New molds were made from the master plug and we were on our way. The custom pre-preg material selected was not cheap...but it is very capable for the task. The spinner would be made from all carbon pre-preg, high temperature stable, with UV protectant in the epoxy. This alone allows several improvements - high temperature stability (critical), improved structural integrity, and the UV protection means the surface can be left exposed without yellowing or deterioration (more on that later). OK, the tooling is proprietary...so, we'll skip that part...!poof! tools (molds) exist. We made two prototypes...the first was a POC and the second is the one that I installed on Thirteen for testing. All the parts are cured in a high temp oven and computer controlled autoclave under both vacuum and pressure. This is the only way to guarantee the high Tg and material density for assured friction transfer through the bulkhead to the propeller. Suffice it to say...the combo exceeded its design goals.

The NTX design utilizes a one-piece Bulkhead/Flowguide to simplify the build process and provide additional stability. The Lycoming flywheel has a small lip around the parameter of the starter ring. The flowguide was designed to fit net/net with this lip - no fill or flox required. It also includes an internal lip that fits against the bulkhead face and prevents cone movement and screw hole fretting over time - this keeps the spinner rotating true. These parts were carefully designed and constructed for a near perfect net/net fit - and they did without any additional work. I was also very pleased to find that the spinner cone is stronger, stiffer AND lighter than the old spinner - even without the blade cut-out holes. Fully assembled, the spinner is 27-inches long and is has a diameter of 10 3/8-inches at the bulkhead. I was truly amazed at the accuracy of this assembly...right out of the molds the fit was perfect. This will allow for a substantially reduced build time as no additional filling or lay-ups would be necessary to achieve a perfect fit.

(NOTE: This section has been updated below - we no longer use the center hub for centering, the bolt holes are now precision located) The next most important attribute is for the prop extension's center hub to be accurately centered on the rotational mass. To achieve that, the bulkhead was precision machine cut to perfectly fit the center hub of the Saber prop extension. It is also worth mentioning that the bulkhead is double molded to create a smooth surface on both sides to accurately transfer the friction between the extension and propeller just as metal does. A drill fixture was then used to accurately place the bolt holes. OK...I was impressed with how it was turning out so far, but now it was time to see how Thirteen likes it. (END OF OUTDATED SECTION)

The fittment to the engine was much easier than the previous spinners. The bulkhead/flowguide was installed on the engine with some mock-up bolts and washers and the top spark plugs were removed from the engine to make it easier to spin. I hooked up a remote starter button to the starter relay and Barry and I centered the spinner cone. Thanks to the internal lip and accurate fit, this process literally took 30-seconds to complete. No joke! We marked the blade positions and screw hole locations on the masking tape and installed clecos to hold it all in position. I made some paper templates and cut out the propeller blade openings and re-installed the fillets. There were only two small lay-ups on this assembly - the two fillet flanges...that's it...easy as pie! Nutplates and screws finish off the installation.

One of the best benefits of this NTX Spinner is that the surface is nearly perfect right out of the molds and can be left raw and exposed to the environment thanks to the UV protection. This means that all that is needed from here is some polishing and waxing to end up with a show quality, raw carbon fiber, 3D look...that is truly SPECTACULAR!!! Pictures just don't come close to capturing the carbon fiber effect. You just have to see it in person.

I have to truly admit this is one project that has exceeded every design goal and expectation I had for it. Maintenance and cleaning is a breeze - just wipe it off. No paint chips to ever worry about and if scratched...just buff it out. It's strong enough to survive abuse by the ignorant public at air shows, takes half the time to build as a standard spinner, works great, and looks FABULOUS!!! Many weeks later, I still find myself gazing at the reflections in the spinner. WOW!! Thirteen has a real diamond on her tail!!!


The NTX Spinner Kit:

I will be looking into offering this spinner kit to the canard public over the next few months. It won't be cheap, but I have no doubt that it will be the most advanced and reliable spinner technology that has ever been on the market...and not to mention, the BEST LOOKING! Here are few more high-res pictures of the finished product that you can download and take a closer look at: right side, top view, left side, side view. Feel free to download and zoom in.

If you are seriously interested in purchasing one, please use the email link below and let me know. It's simple economics, the more that can be sold - the lower the price can be. Check back here from time to time - I'll be posting more info here as things progress.


UPDATE (6-23-11): Over the last few months, I have been putting some flight time on my NTX spinner and demonstrating it at some fly-ins. It is performing flawlessly and has NO signs of movement, fretting, or wear. We have also been further developing the production tooling. The latest development is a precision drill jig for PERFECTLY placing the propeller power lug holes with net/net precision every time. To achieve this, we partnered with Sabre Manufacturing (the same folks that build the prop extensions) to create a jig with the same precision tolerances (.0005") as the actual extensions. To verify that the assembly maintained center, we put the fixture on the lathe and measured the bulkhead's run-out - less than .005" for the total assembly. The first of the production bulkheads was drilled, reamed and...as you can see...with perfect results! This achieves a tight fit on the extension lugs and allows absolutely no movement or slop.


UPDATE (8-10-11): I just got back from EAA AirVenture 2011 a few days ago with the first production version of the NTX Spinner installed on Thirteen. Because my new Catto 3-blade will not be ready for some time, I took the opportunity to test the production of the spinner kit on my airplane with the old 3-blade prop. The prop is getting a little tired and needs resurfacing, but the spinner performed perfectly! I assembled it from raw kit parts through clear coat in 18hrs. over 3-days. I simply could not believe how easy and quick it was to install. I even spent time taking detailed pictures and documenting this build to use as kit instructions (they will be web based and can be printed) - the most complete instructions of all the spinner kits available today. It only took less than 30 seconds (again) to get the spinner cone running true (1.5mb .MPG). It was a good thing it was easy to build as it was completed only days before I left SMO for Texas. It was quite a hit sitting out in Showplane parking...lots of picture takers and gazers. Can't wait till next year when Thirteen will finally have her deserved paint job.

UPDATE (9-15-11): I am proud to announce that the first group of production spinners have been shipped to the beta clients. I am opening the doors to the rest of the Canard world now and am accepting refundable deposits to hold your place in line. Here is how it's going to work: I will be asking for the $400 deposit with your initial order information. Your position on the build list will be “first in, first out” in order of deposit receipt. The deposit is refundable until the spinner is built and ready to drill, trim and prep for shipment. We will build based on interest/need and in small batches. When the spinner build is complete, I will contact you for the remainder of the spinner payment + $50 packing/ground shipping. Once the final payment clears, your spinner will be shipped.

UPDATE (11-15-11): NTX Spinner to the RESCUE!! I have now had my SECOND personal experience with a 'near propeller loss event'. Not on Thirteen, thankfully...but this time on the Stagger-EZ. The local new owner of the Stagger-EZ asked me for some assistance (EAA Technical Councelor) on re-torqing and proper safety wiring his custom Steve Wright spinner/propeller combo. No problem...at least until he taxied up. I immediately noticed the spinner cap was wobbling. Even before we disassembled it, I could already see some soot from the fretting spinner interface and charring hub inside. All three alignment pins in the spinner base had been sheared (-3 bolt stafts), the propeller hub and spinner interior was covered with black soot...and the smell of burned Epoxy was rather strong. There was a deep gouge around the perimeter of the prop extension interface. The extension also showed signs of fretting, heat stress and corrosion. The owner mentioned that the bolts had just been re-torqed to 45-50ft/lbs. (by someone else) less than 15 flight hours ago...they were now down to 15-20ft/lbs on average, some less. The safety wire was intact and had not moved - the hub had been heat compromised. Steve's spinner configuration captured room-temp Epoxy and glass BID on both the front and aft sides of the propeller hub. In fact the long flowguide was actually bonded directly to the propeller...but was not mated to the flywheel lip - that interface also showed signs of fretting. Both sides of the hub showed heat damage, charring and fretting marks - and the forward face of the prop hub itself was not inspectable due to the bonded flowguide. The glass plys between the propeller hub and the extension had seperated - I assume it had been bonded to the hub at one time in the same way as the surrounding flowguide structure. Needless to say - this propeller/spinner configuration had flown it's last hour...and was very likely only a few minutes/hours from departing the airplane. AGAIN...another example of what materials should NOT be used between an engine and it's propeller! So, next up for the Stagger-EZ - a new Sabre extension, a new Catto 3-blade propeller, and a NTX Spinner. Another airplane saved! I can not stress enough how important it is to perform SCHEDULED propeller maintenance, re-torque your propeller to manufacturer specifications and inspect your spinner installation.

UPDATE (11-22-11): We are currently working several production spinners that will ship in early December. I am trying to forecast the need for additional pre-preg material (it's a custom order and takes time to produce) to simply complete or continue the production run a little longer. If there are no more orders, I will begin shutting down the runs. Deposits received by the end of 2011 will be filled...after that, I can not promise anything. On the development front, I will be testing the Belleville washer installation (as proposed by Marc Zeitlin) and use with a NTX Spinner/Catto propeller combo. I'll let you all know how it goes.

UPDATE (2-21-12): The third batch of spinners is done and will be shipping at the end of this month. I am taking orders for the next (and possibly final) batch. The Belleville Washer testing is going great and I now fully support the concept and implementation as proposed by Mark with (or without) the NTX Spinner. The margin of safety increase simply can not be ignored - just do it!

UPDATE (12-13-12):We offer the optically clean ($1,250 shipped) version only. The optically clean version is what you have seen displayed thus far on my Berkut - near perfect carbon pattern/ply alignment and ready for clear coat right out of the box.

Again, I have to emphasize, if you want one - speak up. I have an inventory of complete spinner sets and extra cones (for existing customers that change props).

Contact me directly by email if you are serious about owning one of these unique works of art, function and technology.

Stay tuned for more developments as they happen...


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