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General control line discussion => For Safety sake => Topic started by: Jim Svitko on March 12, 2025, 04:24:44 PM
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I have one LA 46 that sometimes likes to stop with the prop in straight up and down position. Even though I set the prop horizontal as the engine comes up on compression, this engine will sometimes stop with the prop straight up and down.
We fly over grass so the surface is a bit rough in spots. After a flight recently, the engine stopped with the prop straight up and down, and I tried my best to make a smooth landing. The plane bounced a bit, and I heard a faint cracking sound. At the pit, I saw no damage to the prop. Maybe I am hearing things. I am not so young anymore. I removed the spinner for a better look and there it was. A very small, hardly visible crack at the hub of the B Y & O prop.
I was not going to take any chances and I scrapped that prop. Taking a few seconds to remove the spinner was worth the effort.
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I know wood props have been around for quite some time, but they have always made me nervous.
There was a post on SH a few months back where a guy was running an engine in his test stand and was using a wood prop. All of a sudden, the prop came apart and wood fragments hit his arm (as I remember) causing serious injury. Luckily it did not hit him in the face. He said it was a new prop. It may have been a factory flaw or maybe the prop nut was over-tightened causing a crack at the hub. Not really sure.
As a result, I shy away from wood and primarily use APC and MAS props. But when I need to use a wood prop I am more careful.
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I know wood props have been around for quite some time, but they have always made me nervous.
There was a post on SH a few months back where a guy was running an engine in his test stand and was using a wood prop. All of a sudden, the prop came apart and wood fragments hit his arm (as I remember) causing serious injury. Luckily it did not hit him in the face. He said it was a new prop. It may have been a factory flaw or maybe the prop nut was over-tightened causing a crack at the hub. Not really sure.
As a result, I shy away from wood and primarily use APC and MAS props. But when I need to use a wood prop I am more careful.
Plastic props are just as capable of shedding a blade just the same as a wood prop!!
Type at you later,
Dan McEntee
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Safety tip - Stay out of the line of fire of a spinning prop. D>K
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Injuries from wood props are generally a lot less serious than what can be inflicted with the stronger and thinner plastic/carbon/fiberglass props.
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Some time back I got a ton of props via e-bay.. Included were several of those old Top Flite white plastic props from the 70's.. Remember we had to boil them for ten minutes before use according to the little slip of paper in the box with the props?.. Well out of curiosity, I bent one in my hand and it snapped in two. I tossed all 9 of them..Still using the wood props from that batch.
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Do you mean plastic or white nylon?
I have a big batch of Top White white nylon props and they've always worked OK for, but not on a high RPM contest engine. From the Fox Mark III onward, prop strength became a BIG issue. Also an issue with ST G15's when run at the RPM you need for FAI Combat.
The failure mode was a quick tight turn at maximum speed. Gyroscopic precession in action. The plane wanted to turn an the prop said "no, I'm going straight".
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The white nylon props with the red stripes on the tips..
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Many years ago, in a land far away...when I was in Jr. High, one of our group over in Pullman had a Berkley Grumman Guardian "stunter" with a McCoy .36 throw a blade off a 10-6 TF nylon. Tore the engine right off the front of the airplane. They were flying inside the "Field House" on the WSC campus, the engine hit the concrete/brick wall and destroyed the engine. When he complained, TF sent him a new prop, which he promptly put in the circular file.
Only about 25 years ago, we had a NWSR flying day and one of the members, Chris Gomez, had a NOS (new old stock) yellow Tornado nylon prop break immediately when he just flipped the propeller on his McCoy .19. I was watching, and the engine never even started, a blessing. I'm not sure if it backfired, but will try to ask today at the meeting. IMO, old nylon props should be 86'd. Screw them to a display board if that suits you, but don't even think about using them.
Many years ago, I had modified an early (wedge head) K&B .40 for a buddy for FF use. I had the PGF Chinn test from MAN (or Aero Modeller) and thought I'd see how it stacked up with a stock one. The test included rpm data for 40% nitro and a 9-8 TF Super M prop. I and went down to the LHS and bought a quart of Fox 40% and a 9-6 TF Super M. Fired right up and threw a blade, with no harm done. Bad wood grain. Lesson learned: Just because it made it through the maker's QC dept. doesn't mean it's good enough...buyer beware! R%%%% Steve
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Hello I like many have had nylon props throw a blade, I'm sure a lot is due to age of the prop and loosing its flexibility over time. Recently had a Mk17 diesel 1.5cc engine throw a blade which was a first for a slow revving diesel but the prop was an old English prop made by Davis Charlton.
On the other hand many of us here in NZ and Australia are using new Taipan nylon props for slow combat and rev them hard and they don't throw blades and you very rarely brake them as they are new and flexible. Probably not as good thrust as a rigid APC but the Taipans outlast those in combat. I think in 40 years maybe the APC and MAS props will be too old and brittle like the plastic (fibreglass?) spoiler that flew off my Holden Commodore when driving along at 60mph (Australian made GM RWD car with 3.8 Buick engine).
The remaining bits attached to the car were crumbly and brittle from the sun and ageing , luckily nobody was driving close behind me at the time which is like being outside of my prop arc and safely out of reach of flying debris.
Regards Gerald