Eganwp

My Feedback: (1)

Before I start, here are my performance numbers for you comparing APC 11x7 with the MA 11x7 S-2 G/F props on mynew broken-in OS 55ax engine on my Pulse XT 40.(All on 10% Omega, 3500ft ASL, +5*C, 1gallon of break-in done following Dar's break-in)

w/ baffle:
12,840 rpm 11x7 MA G/F S2
12,000 rpm 11x7 APC

w/ out baffle:
13,100 rpm 11x7 MA G/F S2
12,220 rpm 11x7 APC


I'm posting this because I'm trying to decide which prop to use between the two. I've read absolutely every post Icould find on Google comparing APC with MA but still can't find much info regarding both. It seems not many people have done much testing between these props for top speed, efficiency or thrust.

Tried flying both these props and I still think the MA prop flies faster at WOT. Both props have unlimited vertical. Couldn't tell a whole lot of difference between the two. I do like the sound of the engine at higher RPM with the MA prop however (over 1000 rpm faster at WOT). Sounds insane with the baffle removed.

I do understand that the MA flex under load, so 7"of pitch is more than likely a bit closer to 6.5" whereas APC don't flex as much. This isnt always a bad thing however, as MA flexing will provide more torque when needed most under flex, such as take-off or near stall point.Plugging all values into the propcalculator.xls yields about 5mph faster top speed with the MA which confirms my suspicions. (MA = 1.1 prop constant vs APC 1.2 prop constant).I wish someone could radar these two props for trueWOT pass comparison. I'm looking for good speed and realize I could jump to 10x9, but I'll miss the unlimited vertical.

Overall, I really can't understand why sport flyers using props ofthis size go for APC. They're weaker, brittle, heavier, slower, less torque, 3x the price,and have less downline breaking.APC are quieterand likelya bit more efficient because of the rounded tips to reduce energy loss through noise. I'm very interested to try the MA Scimitar props now, as I think they'd be the best all around with their rounded tips.

What do you guys think? Or what have you concluded with your testing? Include your rpm values if possible!


Eganwp

BiggerDanno

I run an APC11 x 8 on my 55. It turns it at 14020 rpms with a tuned pipe. With stock muffler including baffle, it turns it at 12050. Not sure what rpms it will turn with the 7 pitch, never put a tach on it. This is with 15% Powermaster fuel with 18% oil. The engine has about 15-20 gallons through it.

I have not run the MA, just gave the above info for reference.

If you are looking for speed, try the 11 x 8.

daven

My Feedback: (1)

Run what you like, no one elses opinion really matters. If your happy with MA, stick with em.

combatpigg

My Feedback: (3)

Ditto. Slight differences don't reveal themselves unless you are chasing or are being chased by a close copy of what you are flying.

MJD

My Feedback: (1)

Comparing an APC 11-7 to a MAS 11-7 on a test stand tells you very little, except:

- they aren't the same prop
- they load the engine a bit differently
- they are probably close to being a "true" 11-7 but not exactly
- neither one is better than the other, without other factors in the equation

I'm not being sarcastic here, but what I am saying is that those rpm differences don't matter very much and don't merit a lot of deep thought. The lower static figure could for example be - counterintuitively - a slightly lower pitch prop than the other, but whose blade design generates more aerodynamic load on a test stand.

Better to select each one based on the the fact that 11-7 is the diameter/pitch combo you want to test, then try them each and compare. The one you like best is the best - for that plane/engine/pilot combination.

MJD

mk1spitfire

Master aircrew do a range of props, some flex more than others. I've been recently using the s2 (old name,schimiter prop),so called because it resembles aschimeter sword.
The reson for this choice is it looks similar to an apc,It doesn't flex as much as the k series,its more resistant to nose overs not breakingand best, its cheap and black so it has alot going for it.

Now saying this, I've only run theseprops on my warbirds with much success but I have yet to try on a fast plane,like the magnum. I do have a 9x7 to try when eventually the current apc 9x7 breaks so will let you know,

However I'm sure this prop is only designed for 17k?

Saying its cheap is in respect to the larger apc's.

Flyboy Dave

My Feedback: (21)

daven

My Feedback: (1)

Ok, here is another variable to throw in the mix.

Take 10 different APC or Master Airscrew 11x7 props and put them on a pitch gauge. I would be more than surprised if half were at a true 7 pitch. These props vary from batch to batch due to a ton of variables in materials, temp, humidity, pressure, and cooling.

freakingfast

My Feedback: (3)

I run a OS 55AX  with Ultra Thrust muffler on a Carl Goldberg Tiger 40. For speed and climb rate, the best prop I have found for this plane is the Master Airscrew 11X7 S-2 series at about 13,900. The difference between the props were pronounced.
The 11X6 APC was not enough and the 11X7 APC was too much for this combo.

The MA S-2 series props are very, very efficient under 15k on the 11" props, much above that, than the APC sport prop is the clear winner.

Eganwp, if you keep the stock muffler on your plane, Id go with an APC 11X6 to get your engine closer to the 14K sweet spot on the 55 AX. The MA 11X6 S-2 is too light a load the your needs.
Or if you have/make a pitch gage its very easy to reduse the pitch with a heat gun on the 11X7 S-2.  Or you can try cutting down a MA 11X8 S-2 to 10 1/2".

Eganwp

My Feedback: (1)

Thanks for the replies.I'm going to stick with it for now and pick up a few MA S-2 props if Ican find them locally. The 11x7 MA fits nicely between the 11x6 APC and 11x7. Going to try an 11x6 APC also, to see if Ican hit the 14k sweet spot. I'm guessing I wont like it as much however, as my graphing is showing me Ineed at least a 1500RPMincrease to make up for 1" of pitch loss. I doubt an 11x6 APC will grant me much more than 500 RPM, hence about 6mph less speed.Might also try 10x8 and 10x9.

On a side note, Iknow all these tuned pipes increase performance on the OS 55ax, but which provides the most performance upgrade?

Jett Steam
Ultra Thrust
Macs 8.5
Macs Red
Tower Hobbies .46 Pipe

Would prefer one similar to the stock muffler so Idon't have to buy a new cowl to re-cut. Also would prefer one of the shorter mufflers rather than the huge mufflers like Mac. Thoughts? Is the Tower .46 tuned pipe any good?I've heard people getting 600-800 rpm over stock on the OS .46 and it only costs $15!!! What about on the 55ax; similar results?

Eganwp

still4given

I would go with the Ultra Thrust or Sport Jett mufflers. I doubt you would notice a difference using the Tower muffler. I also wouldn't go with the shorter racing muffler. It is designed for quite high RPM, which is not what the OS55 is designed for.

Kmot

My Feedback: (24)

APC's are better at cutting beef steak.

RocketRob

My Feedback: (1)

And fingers

combatpigg

My Feedback: (3)

Beef Steak?!? How fast were you going when you hit it?

daven

My Feedback: (1)

Quote "APC's are better at cutting beef steak"

Looks like road kill to me

Razor-RCU

My Feedback: (50)

I knew Tom and Super-Dave would beat me to this.

APC is superior for performance, MA is superior for durability.  Soo....Do you bang your prop on the ground much?

daven

My Feedback: (1)

lol

Kmot

My Feedback: (24)

And mighty tasty roadkill it was! 

combatpigg

My Feedback: (3)

Well, at least you could come up with a story like, "you hit a stray Black Angus Bull at 201 mph [verified] at Rabbit Lake and saved the Revvers from sure starvation"?

RocketRob

My Feedback: (1)

or was it a javelina?

bob27s

My Feedback: (19)

Years ago we had a club picnic at the field...... and Ibrought a watermellon, but forgot the carving knife to cut it.

Turned out a MA 11x7 worked just fine for the task

As for the props......

Pick the one that works best on your application prop is a match needed between the aircraft and the engine. Sometimes just a bit of trial and testing.

As for the OS55 exhaust, the videos posted by Blade47 of his F-16 and F-18 with the OS55/Jett combination say more than Ican about the setup. It just works very well.

Bob

Jezmo

I know it's an old thread but I wanted to add an observation made at a Club 40 Pylon event I participated in last year. One particular gent. spent the entire day changing props and then test flying. He used APC and MAS props of varying sizes and eventually won the main race at the end with a MAS S2 prop. I had tried some of the MAS props and didn't find a combo that worked on my plane but the point of my story is he did find one that worked on his plane through trial and error and proceeded to kick some butt in the end. It's all about what works best for your particular setup and sometimes the only way to find that out is trial and error also known in the racing world as R&D.

combatpigg

My Feedback: (3)

MAS props lend themselves well to chopping, shaving and reshaping. Those warning stickers shave right off on the first pass.

daven

My Feedback: (1)

Ding ding ding, we have a winner.

Jezmo, you hit the nail on the head.

NO one prop will be the best from day to day or with the same motor. Find what works with your setup and go from there.

JeffH

My Feedback: (43)

I have used both on the same plane and same engine, and the MA would do everything better. Logically, lets try a MA on my other plane(s), found out that the APC was WAY better on that plane. Like everyone has said, fly it and see which one you like better.
One thing I will warn you about with the MAs. In cold weather I have seen them break on the runups. They were not mine, so I do not know how they were treated, nose overs, spinner rubbing etc. The material that MA uses seems to be temperature sensitive since the failures were all in colder weather.