Wierd Prop Flex and failure Picture

[1bwana1]

I had a prop fail this weekend. On my second flight of the day, I heard weird noises as I applied power to take off. The plane also had almost no power. I immediately cut the power to low idle, limped around the pattern, and thankfully landed the plane safely. At first we all thought I had lost a cylinder on the motor. As I went to remove the spinner, I noticed that the prop had delaminated, and split along the leading edge. I was really lucky it didn't totally fail in flight, as this would have surely done a lot of damage to the plane.

So here's the question. The prop is a Mejzlik 30 X 12 CF, which I bought new only a few weeks ago, because I heard it is a good prop for the windy conditions at the Shootout. It only had about 15 flights on it. The picture below shows the prop on it's second day of flying. A friend took the picture and sent it to me. When I first saw the picture it looked to me like the prop was flexing in a weird way. But thought either it was supposed to do that, or that it was just a weird photographic effect. After the failure, I went back and looked more closely. The plane was clearly at low idle, which is only about 1,300 RPM. This is shown by the fact that it is still attached to safety starting strap which is slack, at high idle (1,800 RPM), the plane would be pulling on the strap. Even at this low RPM, look at the flex in the prop.

What do you guys think? The prop showed no exceptional vibration or noise at this point. Are props supposed to flex like this? Does this show a weakness in the prop from the beginning, that indicated this prop would fail? I'd really like to hear from you prop experts out there.

Click on Picture to View it larger.

[SmoothFlying]

I think it is just the picture. Meizlic's are exceptional props. I've run them for years and probably have over a 100 hundred flights on mine. It might have had just an unforseen crack in it and just decided to crack further. Dont let this get you down about Meizlic props. They are awesome. They have hardly no flex in them. Thats what you want in a carbon prop. Strap another one on there. I'm sure you just got a fluke.

[tony-amps]

bwanba,

I have had a similar failure of a 28.5 x 12 three blade. Failures happen even with the best products. Send it back for warranty. Mine delaminated along the leading edge as well but only on one blade.

Tony Fandino

[Scott Gerber]

	Quote: Originally Posted by TeamFlatout
	I think it is just the picture. Meizlic's are exceptional props. I've run them for years and probably have over a 100 hundred flights on mine. It might have had just an unforseen crack in it and just decided to crack further. Dont let this get you down about Meizlic props. They are awesome. They have hardly no flex in them. Thats what you want in a carbon prop. Strap another one on there. I'm sure you just got a fluke.

I agree that it's the photo and the shutter speed of the camera taking the pic. I've see that effect a number of times on line before and it's is kinda cool to see a prop or rotor blades on a heli appear to bend in rotation...


Scott

[Tired Old Man]

You would have had to use a fish eye lens for that effect to be lens induced. The prop was likely defective from the get go.

[Vic3D]

I believe the delamination bit, because it has happened to me. But that picture is photoshop..

[SmoothFlying]

The picture is not photoshop. I dont think he would post something like that with a question about it delaminating.

[pepatrick]

I love the photo forensic expert wannabes. Ive seen a prop do that in pictures without fisheys lenses. Its not a photoshop...not everyone wastes their time photoshopping bent props on their plane. Its probably not related at all to the failed prop. The prop could have just been one of the defective props that are out there. You build enough of them your going to get some bad ones every once in a while.

[cadconversions]

I first noticed a prop looking like this on an electric flight model with a GWS prop. It was discovered that it is the way that a digital camera "records" the incoming data for the picture. Although it happens extremely fast, it writes from top to bottom - so the prop is in a different position as the camera "scans" the scheme to record the image. It's on RCGroups somewhere if you wanna search.

[Tired Old Man]

I've been shooting pictures a long time, both film and digital, models and full scale. Never had that effect without a fisheye even with helicoptor rotor blades. The prop is likely actually flexing that amount. There's some budget wood props that have always done similar. A good carbon prop should never do that. The author of the original post probably knows how stiff the prop was prior to use.


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[1bwana1]

Let's get the photo-shop issue out of the way. This picture has not been photo chopped in any way. The only thing I did to it was reduce it's size so it could be posted here on the web. I have no motive in posting, except the sincere desire to understand why the prop failed.

The camera that took the picture was just one of those cheap point and shoot models. I doubt it had a fish eye lens. I guess the flex could be some sort of artifact from the way digital cameras work with really fast moving objects. This seems to be a likely explanation, because if you look at the lower blade, it appears to be hanging in air, and not 180 degrees from the top prop. That is definitely a camera induced anomaly. But I am no photography expert, so who knows whats really going on.

I also am not trying to bash Mejzlik. I use their carbon props on all my big planes, and have had great success with them. This is the first one that has been anything but perfect. They are my favorite prop, and I will continue to use them. The prop I put back on this plane is my regular Mejzlik 32 X 10 CF that has hundreds of trouble free flight on it.

I did not post in order to bash anyone, fool anyone, create controversy, or gather info for a warranty claim. I bought the prop from DA so customer service is the last of my worries. The prop failed, I thought the picture looked weird, and might be related to the failure. I found this interesting, thought the Giants community might as well, and maybe we could all learn something from members who have knowledge in this area.

Vic3D, I guess you think the whole moon landing thing was a photo-shop job too. LOL! Just kidding amigo.

Thanks to all the guys who responded, I would like to hear more.

[octanehuffer]

The prop was actually flexing like that while running and it should be very ,very ridgid. If the force from the prop pitch was causing the blades to bend you should be able to duplicate the bending by hand. Does the prop bend in your hands?

[1bwana1]

I never noticed it flexing while I was drilling, mounting it. Of course, now that it has delaminated, it has no structural integrity on one side.

[Blip]

Can you identify any porosity in the laminate of the broken blade? Just wondering if it was laid up badly.

[SleepyC]

That there is a photo anomaly having to do with shutter speed.
Sometimes you will get them where the prop looks like its at a 90 deg angle to itself, and sometimes like there is an extra blade that is horizontal to the actual prop.

The lighting has to be right and the shutter speed compared to the prop speed has to be just right.

Its like when you point a video camera at a computer screen and it appears to be blinking and moving up, depending what your FPS is can make that happen or take it away.

Cool Pic Steve!