Jezmo

I am not going to try and pine for MA or for that matter APC. I have however witnessed a pylon race won by a gentleman running a Master Airscrew when every other competitor was using an APC. That prompted me to start experimenting with MA on my racers and I can say the same. I am not going to get into what might or might not have been done to the various props we used but the Master Airscrew props are not as bad as some would have us believe. I have also turned a 14X6 Master Airscrew in excess of 14,000 static and in the air the prop was ripping so loud it was obnoxious. That prop is still in use to this day and has been for over 4 years. Something happened to those broken props and I have no idea what because I was not present during their short lifetime (If I tried to say it would be purely speculation). Whatever happened could surely have been before the OP purchased them including some sort of manufacturing problem. It is impossible to say for certain.

On another note I have used clothes dye on APC props with success and it makes the color far less irritating to the eye improving the overall appeal of the aircraft on which they are mounted. Can't believe the APC folks haven't brought out black colored props by now. Or at least a very dark grey.

DougB1

My Feedback: (11)

Can you share the method with coloring the props, I would like to try a couple and not tell anyone in the club and tell them I bought them this way.

p51Dpony

Negative Houston.   Never had a problem with master airscrew other than slicing peoples fingers when they want to flip the engine by hand as the trailing edge is so damn sharp.  I know the kids here running .46ax engines with 10x6 master airscrew g/f props turing 13k-14k rpm all day long and no fails and we fly in cold weather (20's and 30's F) with some regularity.  I would look for a prob other than the prop:  extra vibration from unbalanced spinner/ wrong prop reaming/ bad motor bearing (never seen this if they're bad they usually fail before ruining props..), dessicated prop (never seen this but the stiff grey resin graupners have a warning to soak prop in warm water if its "been dry a long time" )and the things already mentioned which are more common issues:  spinner touching prop/ prop getting stressed during tightening.  

But... having said all that I'm amazed how all the "safety first" guys often have their engines running where a thrown prop could hit someone.  In many years of flying I've seen a few thrown props (think 4-strokes in winter weather!) and can recall only one or two prop fails that I think we found one of the above reasons the culprit.  I got into nylon props in the 1980's when I went through a float plane stint and at the time nylon was recommended superior to wood but really if you're not dunking your nose very much wood is just fine on the lake..  happy flying all and Merry Christmas!

Bozarth

My Feedback: (15)

So are you concluding that these two items were the culprit?

Kurt

bigjohnrav

My Feedback: (5)

Reinforced plastic is ideally molded with virgin material with the full fiber length.Suppliers will add regrind ie. sprues and assorted scrap, the result is much shorter fibers and compromised strength all to save a few pennies.John

jmb52760

No, I've just decided that it's best to play it safe. These things could definitely play a part in the failure.

I think that a high performance prop is just a good idea for a classic pattern plane.

I have also decided to move up to a 12-6 for the Curare, even though this is contrary to most classic pattern planes.

tony0707

hi
you should be balancing your props ,not just for the sake of the prop ,but for the sake of protecting your radio equipment in the fuse
did you ever feel the fuse with the engine running on a balanced prop ?
you will not believe the vibration you will feel ,when you do just that
i have seen the vibration unscrew 4 of the screw holding in a servo in someones plane
regarding the prop i glue two of my screws inuse only alan key screws so i can get them outand add 1/4 x 3/8 hard wood under my servo trayso screw is always deep into wood
sorry you had the problem ,with the prop breaking
i mostly us APC propS-did a very extensive amount of testing to find i get the best vertical performance from them over wood or MAS of the same size and pitch
i judge all performance by vertical performance
MERRY CHRISTMAS TO ALL TONY

TimT2000

My Feedback: (1)

[quote]ORIGINAL: jmb52760

I'm going to give facts here, you can draw your own conclusions.

Last week, I was flying my OS .55 AX powered Deception 40 and in a down-line with the engine turning very high rpms, the prop let go. The firewall was ripped from the plane and the cowling was trashed. I brought her back dead-stick and landed with the engine, firewall, and what was left of the cowl hanging from the throttle cable.

[/quote

Wow, I had the very same landing with my Q500 racer and a APC 9x8. The Magnum .52 was getting 16,500rpm on the ground and
this was about the 30th flight on this prop. Well it through a blade on a fast fly by and ripped the firewall from the plane. I landed it just
as you did with the engine and pipe hanging from the throttle rod right at my feet. I did repair the plane, put on another APC 9x8 and it
now has about 20 more flights.

Just thought your landing was interesting as it was just like mine. My APC failure is the second at our field that I have seen. The other was
a APC 16x4 on a 3D plane. I have never seen a MA failure in flight yet. Probably will now if they have creases in them now, or have had a
bad run.

Cheers
Tim

jmb52760

It was quite a sight to see the airplane rolling down the runway with the engine hanging straight down.

I was really glad that the throttle cable held the whole mess together.

TimT2000

My Feedback: (1)

Me too !! The engine just drug along the ground right to my feet.
One of the best landings I have made with the thing.
Tim

jmb52760

Your pics are similar to what mine looked like except for the pieces of carved balsa cowling hanging around the engine.

Here are two "before" pics:

jmb52760

And a pic of the Curare, just for fun:

The damage to the Curare was amazingly light. There were just nicks in the paint around the engine, and a spot on the wing where the prop blade must have bounced.

eddieC

My Feedback: (2)

IIRC, the Rit dye is dissolved in a small pan of very hot water and let the items soak a few minutes. For best penetration and deepest color, leave on low heat (below a boil) and leave soak. The longer it soaks, the better. Very simple process.

TimT2000

My Feedback: (1)

Nice planes. Kit built right? I see you had a good spinner gap on the metal one so that was not the problem.
I also had about an eighth inch around the good blade so it was not spinner to prop contact. The prop was balanced
and was turning 17,750 in the air per the doplar in my phone.

Fun Times !

Tim

jmb52760

Deception (the red plane) is scratch-built from plans. Wing and Stab Cores and the Canopy were developed from this effort. You can search on "Deception 40 Scratch Build" and find the whole story.

Curare is from a short kit by Eureka. It's also a build thread.

When I don't feel so lazy, I'll edit this post and put in the links.

Bozarth

My Feedback: (15)

Balancing a prop is a good idea - but are the forces created by an unbalanced prop imparted on the prop (i.e. leading to blade failure) or on the crank, motor, firewall, airframe, etc.?

Kurt

jmb52760

For each action, there is an equal and opposite reaction.

So the vibration forces are imparted on the prop, the crank, the motor, the firewall, the airframe and all of the equipment inside.

One can only reduce the forces by providing damping or a softer spring-rate mounting so that the energy is absorbed over a longer displacement. Thus the foam around the radio gear and the rubber grommets on the servo mounts.

Bozarth

My Feedback: (15)

I would think the prop is creating the forces.

Kurt

rgburrill

According to Master Airscrew the maximum RPM for the GF series is 165,000/ prop diameter. So in this case it is 15000 RPM which is NOT well above the RPM limits of those engines. And he is flying with a smaller prop so at max throttle could be turning 18000 RPM.

The GF is a sport prop for a sport engine. The AX and FX series are high performance engines, not sport engines and using a GF is going to lead to problems.

iflyrcmodels

My Feedback: (10)

Just had the same thing happen with an MDS .46 on an easy sport. However the cable came loos from the throttle and it was hung wide open. it took to large circles to slow the plane down enough spining half a prop wide open to land. The motor mount bolts were loose but still intact. Amazingly enough I bench ran the motor with a new prop and it still runs like a new one. That was a master airscrew 10 6 and it seperated in the same place as yours.

jet22b

Hi All;
I have been in the background reading this thread and all the very good info people have posted. About two months ago, I was helping one of my club member start his 90 size 2 stroke airplane. The plane was on the starting table when the right blade of his prop let go!! He told me that he felt something zip by his right ear. We look all over the starting line and did not find the blade. We look at the prop and found that the left blade was ready to go too. I forgot what prop he was using at the time. Now to give you some info from the heli side. On my 90 size T-Rex heli, my head speed is 19,000 rpm, so when one of the blade let go, it can become a bad day!!! I can remember one time I had a bad crash with the T-Rex and found one of the the main blade 500 feet from the crash site stuck in the side of a large trash can we have on the field. Now that could have been a person!!!
On all my planes, I go with APC and Masterscrew props and only had one prop let go on the Hangar 9 Jackal 50 with the EVO .60NT engine. On all new props I pick up now, I check every part of is for anything out of the norm.
Fly hard and play safe everyone. Merry Xmas to all!!!
Sonny
aka
jet22b

eddieC

My Feedback: (2)

I think that's one-too-many zeroes on that headspeed !   [X(]

Jezmo

Used RIT dye and a large stainless pot with very warm water. I had to experiment a bit with soak time and such but even the first one looked far better than the plain grey. I brought the water to near boil and added the dye, let it soak for 15 to 20 mins and removed it. That's all if memory serves correctly other than letting it dry which doesn't take long due to the warmth.

DougB1

My Feedback: (11)

I take it that the almost boiling water does not warp the prop any?

speedracerntrixie

My Feedback: (29)

I have not seen something not mentioned here yet. If the engine is running a bit on the lean side, it can pre-ignite ( Same situation as your car pinging ) the end result is alot of unequal force being applied to the prop. What happens is the engine fires early enough as to want to run backwards and it's the momentum of the crank/prop that keeps it running the same direction.