Hi y'all

It's me again with a new question. As I get a lot of great insights/advices from great well-experienced flyers.

Ok, What is better for 2 Stroke engines ranging from size .46 to .90. Revs or thrust? I have Evolution PTS .45 which is almost .46. it's installed on my Hangar 9's P51 Mustang MKII, I was told that I should install 10X7 prop instead of 11X6 both APC 2 Bladed. I told the owner of my LHS who advised me for 10X7, he said your plane would fly good, I told him it would give me more rpm's than I'm getting from 11X6, he said more rpms are better for your engine.

Correct me if I'm wrong please; more the diameter and shorter the pitch higher the Thrust? Lower the diameter with little more the pitch higher the RPM's correct?

Thrust is power of the engine to push the air back if I'm right, and more revs means more thrust? It just gets confusing if somebody can give great idea about revs and rpms, plus what is best for what engine and for planes like warbirds, P51 Mustang, Hell Cat and so on.

Thanks in advance[8D]

Mody

Determine the optimum engine RPM by using different props. Run it that way.

Noise does not equate to power. If you get to high in RPM, you gain nothing but noise and wear and tear on the engine. If the manufacturer states in the engine specs something like "3.2HP at 16,000 RPM", well, it's theorically possible, but not very practical. It's trial and error in selecting the right prop for your plane and you probably will find that it runs best and pulls best at, say, 12000 rpm.


CGr.

Hi,

What is far more important than thrust vs revs (unless you are into pylon racing) is the reliability and longevity of the motor. Choose a reputable brand of motor in the size needed to power (or overpower) your model and experiment with props to find what best suits your model and flying style.
In a very rough analogy pitch on the prop is like the gear ratios on your car the lower the pitch the lower the gear, the higher the pitch the higher the gear=speed.

Cheers,

Colin

CGR & Colins

Thank you very much for your input. Currently I own P51 Mustang PTS of Hangar 9 with the same engine it came with Evolution .45 Two stroke. The other engine I have is Magnum .46 Two stroke which I used in my Escapade which unfortunately crashed. So my question is which prop should I use with my P51 Mustang with Evolution .45 engine on it. APC 11X6 or 10X7 as per my LHS owner's advice. I do understand and agree what high Revs would wear the motor out faster.

Thanks

Mody

I would recommend the 10x7 if you are interested in going faster...

The APC 11x5 would be a better choice if you want quicker accelleration, shorter T.O. roll and stronger vertical perf.

The APC 11x6 is just a wee bit much for a stock Evo Alpha .455/.46 (w/ stock muffler )

If you really want that Evo to run great, put a Tower .46 (Aquacraft .46 / GMS ) muffler on it (15 bucks ) with either the APC 10x7 or 11x5 and use 15% nitro...don't worry about letting it rev up a bit. Mine spins over 14K with the afore mentioned combination, which is well within specs.

Just make sure your prop and spinner is balanced...an un-balanced prop and/or spinner will wear out bearings faster than a few "extra" revs.

FWIW 14K is not really "high" r.p.m.
If you were going much over that though, I'd say to consider the bearings...but the rest of the engine isn't going to know the difference.

Hi,

I would start with the 10x7 and try the 11x6 later. The differences will be subtle and require slight retuning of the high speed needle. The 10x6 will give you better ground clearance for the inevitable heavier landings as you become comfortable with the modle. When the carby is properly tuned neither prop will "over prop" or risk damage to your motor, a "lean run" will risk damage. Always err on the side of a little rich.

Cheers,

Colin

proptop,

Thanks for your great input. I have almost brand new Magnum .46 which I had installed on my Escapade. It only ran 4 tanks, and I got a brand new carb for it as the threads in carb hole stripped out. How about Magnum .46 with 11X6 prop or 11X5?

Mody

Colin

I run rich mostly my engines, I know running lean is risking the engine's life as well as it gets heated up more faster than on rich.

The Magnum is made in the same factory as the Evo...and is pretty darn close to being the same engine internally...so the same advice applies to the Magnum.

These Evo (and Magnum ) engines can really run well, with just a few tweaks...meaning mainly changing to the Tower muffler.

I have one (Evo Alpha .455 ) that I use an APC 12x4 on in a 3D type airplane...runs as well as an O.S. or TT .46

I'm gonna give it a try first to APC 10X7 if I don't like I'd prolly go for 11X5.

Thanks

Mody

I had the older first p-51 pts and I had a 10x6 or 11x6 I will check and let you know. I think it was a 11x6 and the thing was a screamer.

rowdog_14,

I flew with 11X6 I liked it, but my LHS owner said try 10X7 and he handed me the free APC prop, he said use it and then let me know the result, it's been a almost more than 2 weeks and I haven't flown yet, due to weather and my moving to new house. I hope I'm gonna try this weekend.

I had old Mustang PTS the first one and it crashed due to Rx failure, but I'd appreciate that once done trying both and post your feed back


Mody

Get your LHS to lend you an APC 11x7 if they will and try that. I have had great success with that prop and the stock engine.

Mody,

Check this article from the late Andy Lennon about propeller selection:

http://findarticles.com/p/articles/m...6/ai_n8988659/

just be advised that if you try the 10x6 on your mustang, watch your take off speed, make sure you have enough before giving it up elevator, these mustangs have a tendancy to tip stall if you don't have your speed built up, don't ask how i know

As you can probably see by now, there really isn't an answer to your question that's useful. Every flier likes a different feel and a different set of flying characteristics, and the prop has a huge impact on both. Broadly, the difference between the 11x6 and 10x7 will be a trade off between acceleration and vetical performance for top end speed. If you go down to an 11x5 or a 10x6 you'll notice quicker acceleration in your engine which may or may not give you more speed or vertical depending on the airframe. What's important is that the plane flies like you want it to. For beginners, I suggest going with more acceleration since takeoffs can be hairy and recovering from stalls is faster with a big prop.

if your using a 11x6 or 7 on a 40-47 engine your have way to much prop for the engine. While the engine may "turn" it it will not like you and won't give you as much power as you could be having. A lot of people fail to understand that our engines (like all engines) have a torque curve where they make the most power. This is around 12500-14000 on the ground. For most .46 engines a 11x5 will put you in the 13000-13500 range and 10x7 in the 14000 range.

The props I was using was a 11x6 and a 11x7. The 11x7 was of the new evolution props, they are great. I think you will be happy with either but I would go with the 11x6, less on the engine and the transition is a little smoother.

jimmyjames213, thanks for the input but you will be surprised what the evolution pts motor will do. It is a .45 engine but it will turn that 11x6 engine with a smile. I tried a 11x6 on another engine .47 supertigre and it about killed it. Most .45 will take a 11x6 so he should not have a problem with a 11x6. I was actually getting around 12800 on the ground with my 11x6 prop. This engine has lasted me 5 years with this setup, I do have it on the self as of last year because my bearing started acting up after about 1million flights. Seriously I have about 400- 500 flights on this engine if not more I lost count and just now had a problem

Hi there,
I got in the habit of running 10x7's on the stronger .46-.49 engines back when I had an enja shneurel ported engine cause it really had the power, one day we broke a prop on an evolution .46 and all we had out at the field was a 10x6 master airscrew.  Lord Almighty that engine came alive with a 10x6, great rpm and faster flying than the 10x7 produced because I guess it let the motor get to the rpm more in its powerband.  As far as engine longevity that motor has been run hard for 5 yrs and still runs great.  An 11x5 gives a totally different engine run characteristic, low rpm, increased fuel economy, quieter, more flywheel effect..... but for all out power try a 10x6!

oops, I mean 11x6! not 11x5..comment above..

The 10x7 will give you higher top speed (power) and possibly land faster. If you want to go the opposite way with greater static thrust, shorter takeoff, more vertical, slower landings, I would even try a 12x4 (assuming you have ground clearance). It might make flying more fun for you, especially if you are new at flying.

Just for the heck of it, try an 11x4 on a .40, a 12x4 on a .46, or a 13x4 on a .50. More thrust, not much less speed, and MUCH more pleasant landings!

You are not going to over-rev the engine with these props. I have run stock Super Tigers over 20,000 on a tuned pipe without problems. Balance the prop, though.

Try those low-pitch props and see how much more fun it is.....

Prop selection is a pilots choice thing, it's up to the pilot to test out different props to find the size that will fly the plane the way they like. As long as the engine is working within it's recommended rpm range there is no correct size. The 11X6 APC is one of the most often used props on .46 two stroke engines. I found the 11X6 worked just the way I wanted on my .46 OS LA engines on my Up-Roar planes for fun fly compition. For racing my pilot liked the APC 10X8 on his webra .55, I thought he was nuts but he liked it and it worked for him. There is really no blanket answer to props, as long as the engine is within it's working RPM range it's pilots choice. All my engines run bigger props with smaller pitch in there lower RPM range, I like it like that, others may want a faster plane and it wouldn't work for them. Works for me.

I wouldn't worry too much about replacing your Evolution TPS .455 dual ball bearing twin needle 2-stroke. It's a good, solid engine that runs well once the needle limiters are removed. Replace the fly wheel with the regular drive washer that came with it, and you can actually try a Master Airscrew 10x7 3-blade prop with your original spinner.

A lot of folks think 3-blade props stink, but it's only the Evolution 3-blade trainer props that are weak. The TPS prop is like a 10.5x4 3-blade, and the pitch is so shallow that the plane can't build up speed even at wide open throttle. It's great for training with an Alpha 40, but it's too slow for flying a Mustang or Raptor PTS.

The two blade props will work just fine as well. The extra surface area of the three blade prop will actually help you slow down for landing a bit more by providing a bit more of an air break effect.

Wether you go with a 2-blade or 3-blade prop, your Evolution TPS should really open up quite a bit with just those couple of recommended changes.

Good luck and good flying!

Gray Beard said it well. It's a pilot's choice and use what makes it fly like you want it to fly. That's probably why I have about 50 or so props of various sizes.

CGr.