I'm sure this has been so sorry for repeating questions, But I am looking to put a bigger motor in my Hanger p-51. I'v had mine since they very first came out and the motor after hundreds of flights is getting to the end. And I'd like to get a motor that is bigger. I'd like to stay with Evo motors since I had such good luck with the stock one. Looks like my options are a .52 or .61 so if someone could tell me which would work best and what I may have to do to install it that would be great. I'd rather put in the .61 so if someone has done this please tell me what you all got and did to get it to fit.

Thanks guys,
'

I am looking to add a 4-stroke. I will be double-check with Horizon to ensure it will fit first. Should though.
http://www.horizonhobby.com/Products...ProdID=SAIE056

Both will fit, but the .61 may require some minor modifications.

The .52NX will be a "drop in".

opjose, with the Saito .56 4 stroke, could I use a 4-blade prop or is a 2 blade the way to go?

Ouch a .56 4 stroker in the PTS will be like putting in an O.S. .32 2stroke FX engine.

Very underpowered.

Add to that the inefficiency of a 4 blade prop, and ugh....

With our model engines the biggest problem with 4-blade props is finding one that suits the engine/airplane combination. The lack of choice in 3-bladers and 4-bladers really makes the efficiency question insignificant. 3 and 4 bladers have a bad reputation more because they offer almost no choice, not that there is any real difference in efficiency. We simply don't have but one to try most times. No way to find the best 3-blader when there isn't but one that might or might not work. But we've almost always got 8 or 20 two bladers to sort through.

da Rock, I read through the 4-blade thread in the warbird section and I am not sure if anything got resolved. I have to admit that I am asking only due to "cool" looks and not for performance. I don't need a 100mph PTS mustang, just one that won't be way underpowered. Would I need a larger 4-stroke or is it not that simple?

Well going from a Master Airscrew 10x6x3 to a 11x6x2 APC prop makes a WORLD of difference.

I initially put the MA prop on the PTS but after moving to the 11x6x2 I haven't looked back.

The two props are equivalent pitch & size wise...

Most of the performance improvement, which was substantial, had to come from the better efficiency of the 2 blade versus the 3 blades.

I have a Saito .80 on a PTS, and it's not overpowered at all. In fact, with a Master Airscrew 13x6 "Scimitar Profile" prop, it's a bit slower than with the normal PTS 2-stroke engine, but the vertical performance is great. The only caveat is that the .80, being an older engine, is large and doesn't fit the cowl very well. A new .72 or .82 would be a lot easier to fit.

Unfortunately, after about 15 flights I discovered that I hadn't fuel-proofed the firewall as well as I'd thought. Fuel had gotten in around the edge and the firewall was starting to turn to mush and pull away from the fuselage. So she's grounded until I can get that fixed.

Wouldn't the 75 AX work for spinning more blades and the size is supposed to be comparable to the 46AX in mounting.

rsteffen42:

Eh, no one really said it would be.

CowboyLifesaver:

2 blades are said to be more efficient than 3 blades no matter what the engine size.

This is one reason racers have even tried single blade props on their planes.

I have been training a guy with the pts mustang with a pro 46 with a 12*4 an the airbrakes removed It has loads of power super vertical
I know another guy that has a tigre 45 using the same set up an it is also just as strong

No problem with the 2 strokers.

The comparison was with a .56 4 stroker instead.

So, the .56 4 stroke I asked about with a 4 blade prop equals bad... Fine. Can anyone suggest a 4 stroke w/ 4 blade prop setup that will fit the PTS and pull the airplane around the sky? Or am I barking up the wrong tree here?

No, the "efficiency" discussion is not resolved. There probably won't ever be a clear comparison that shows clearly how little that "efficiency" sound byte "knowledge" really applies.

Problem is that we don't have truly similar choices for our props. The prop selection in 2blades is massive. We've usually got 3 choices of pitch for every diameter PLUS we've got maybe 6 manufactures offering those 3 choices for every diameter PLUS they often offer two or three different shapes. So each of us has no problem testing the available 2bladers, and there are thousands of fliers who have experience doing just that for exactly the engine we have. And some of them have tried different props for our engine AND our airplane. There is no problem with the depth of our data base of knowledge when it comes to finding a very good fit of 2blade to whatever airplane/engine we're interested in.

On the other hand, I just looked for a suitable 3blade for a couple of my models. I found ONE each. And they are expensive. The chance that those two props are going to effectively suit those two airplanes is little better than 50-50. And I've got to spend appreciably more to find out than I'd have to spend to try a couple of 2bladers.

So what does our huge modeling community actually know about 3bladers, given the situation ALL of us are in? Not too much. Except that a bunch have heard the sound byte wisdom, "more blades is less efficient". And have no reservation parroting it. And some have turned it into, "more blades suck" or simply blurt out whatever comes to mind.

And we suffer further from not having an accurate way to figure equality between 2blades and 3blades. There is one prop mfg who suggests the appropriate way to choose a 3blade is to reduce the diameter and increase the pitch. A bunch of our prop "experts" have missed the pitch detail and think it's correct to simply reduce the diameter and they've got equality. Ain't even close. And some of them even compare props of different shape and from different mfg. Again, it's apples and oranges when the subject is efficiency.

so what is the deal with the comparisons..............

We have to operate our engines in their power band for them to produce their best horsepower.

The number and length and width and airfoil and tip shape and progression of pitch all effect the props ability to move our airplanes. And diameter is the simplest for us to see and understand when trying to keep an engine turning to a chosen rpm. So the sound byte wisdom says we should reduce the diameter to bring up rpm. And when we throw extra blades at an engine, it slows and we then figure we need less diameter on that new, slower prop.

Higher aspect wings and higher aspect prop blades are aerodynamically more efficent all else being equal. In our situation, all else won't be, but what the heck. We only need to sound like an expert, not actually prove it.

And longer blades are almost always higher aspect ratio blades. So there is one probably true part to the efficiency buzz phrase. And it's actually based in fact. So how "much" efficiency are we talking about? Darned if anyone has any numbers I've ever seen.

One problem we have is that we also don't have any really proven and tested way to get the numbers. So it's cool to live with our sound byte wisdom.

I recently tried a couple of airplanes with 3bladers. Both airplanes have been tested with a number of 2bladers and the best found for each. I went through different diameters and pitches. Didn't have to make a crusade out of it because I've got a fair amount of experience doing it PLUS there is a huge resource of flyers who've fun the same engines and the same models and the same engines on the same models. When I looked around for 3bladers to try, I found one each for the two airplanes to try first. They're expensive so I didn't buy up the other two 3bladers that might work.

With one airplane the 3blader I tried worked measurably better than all but one of the 2bladers I tried out on that airplane. I figured that was lucky to have hit so close to the bullseye with just one bullet. The airplane is overpowered with my choice of engine. I'm using a 90 on a 60 size/weight airplane. The flight envelope I'm applying to that airplane has no place in it for efficiency (whatever that'd be) because I chose not to include it. I'll fly that airplane until it's worn out with that 3blader, and it does more than I want from it.

The other 3blader on the other airplane didn't stack up as well against the list of 2bladers tested on that airplane. I'm not flying that 3blade on it now, but plan to buy another whenever I find one that looks like it'd apply. Did that prop "fail" because it wasn't efficient enough. lol..... who knows, but maybe the other 2bladers that didn't do as well as the chosen best 2blader were not chosen because they were less efficient than the winning 2blader.

"efficiency" is a great sound byte word.
Why? Because our props only come with diameter and pitch numbers printed on them, no efficiency ratings. So whatever we want to say about efficiency only has to sound "expert".

Showtime100,
The Saito .56 is probably comparable to a .40 two cycle. Have you found anyone selling a 4blader they recommend for a .40?

If I were going to try any prop for that .56, I'd look at whatever is suggested for a .45 two cycle. The FourStokess turn less rpms than TwoStrokes, so the prop will necessarily be larger in one dimension or the other or both.

And BTW, did you know that "slower props are more efficient". lol..... no lie...........

Yeah, yeah, rub it in.

There is validity to the lower blade count arguements though.

The same thing is seen in other areas, such as boaters finding that a 3 bladed racing prop is better than a 4 bladed, etc.

In all cases the lower blade count results in higher speeds or better acceleration, something which is echoed on RC planes...

So "efficiency" as such is not such a misused sound byte.

I was thinking he just wanted the cool factor and for it to be a bit more than just a 46 with a 2 blade. I know what you mean though. I have a 3 on my hangar 9 mustang (60 size) with the 120 pump. It spins a 15X7 3 blade, but I still get about 130 140 out of it. I'm sure I'd increase speed dramatically with a 2 blade. But it will pull straight up forever with the 3, besides 3 looks better........ Can't wait to get the 14X7 4 made for it........[8D]

Don't bet on that.

The word "dramatically" blows the idea apart. It's exactly the problem we have in our hobby with sound byte ideas. One true concept gets expanded and interpreted. And winds up screwed.

It's not a good bet that a change to a 2blade is going to even increase the speed. It will if the 3blade is a really bad match to the engine/airplane, but even then, the speed difference might be so slight as to be meaningless.

I've been flying a H9 P47 alternating a good 3blade with the best 2blade I've found for the airplane. The guys watching can't tell which prop is on the airplane until I shut the engine off. I'm not sure that I'd know which is being flown if I hadn't been the one changing the props.

I've also been flying the ARF SkyBolt alternating props. Same deal with the guys, and in this airplane's testing, I'd bet good money the top speeds with the different props isn't measurable.

You can try a 70 magnum it should pull a 13 3 or four blade prop an still fit in the pts

kerwin50, Thank You. That is all I really wanted to know. A place to start.

I agree, it is apples and oranges. The efficiency of a prop is relative. Relative to what you are wanting to get out of the prop. Are you wanting speed or vertical lift? Do want fast acceleration and high rpm like for a pattern plane or gut wrenching torq to hang a 3D on at 1/4 throttle. How efficient the prop is, depends on what you want it to do. The comparison I like to use for 2 vs 3 or more blades is the difference between a gas engine vs a diesel engine. A 300hp gas engine and a 300hp diesel engine have the same hp but are two very different animals. The gas engine has fast acceleration and high rpms and the car goes fast but if you hook it to a 2000 pound trailer it stuggles. The diesel has slower acceleration but more torq at lower rpms. It will pull the trailer without breaking a sweat but its not going to win any races. With 3 & 4 bladed props you have more blades digging in to the air so more torq or pulling power at lower rpms and a little slower throttle response. That is what H9 wanted for their trainer. Now the downside is the at higher rpms 3 & 4 blade props start to kind of catch up to themselves. The blade behind is passing through the disturbed air from the blade in front and becomes less "efficient". There is not enough time between blade passes to let new air in between to bite into. Which keeps the top speed down, something else H9 wanted on the PTS. First you have to decide what you want your plane to do, then you can start making engine and prop choices. Actually you need to first decide what kind of flying you want to do and then decide what plane to get. The P-51 PTS is a great trainer and intermediate plane and will do basic aerobatics but the dehydril keeps it from doing them as clean as a 3D or pattern plane. For that kind of flying I fly my Twist 40 or my Kaos 40. Choose a plane for the type of flying you want to do. Trying to get a plane to fly in a way it wasn't designed for is asking for heartache.

In Showtime100's case, he wants the cool look of a 4 blade prop without sacrificing a lot of performance. The problem with a 40 size plane is the choices are few on 3's and almost non-existent on 4's. There seem to be more multi-blade prop choices for larger planes. I'm looking for a good 4 blade for my PTS as well. A nice black one so I can dip the tips into yellow paint for that cool authentic P-51 look. I don't care if it goes fast or has a lot of verticle. I just want it to look as good on the ground as it does in the air. As for choosing an engine, the argument for 2-stroke vs 4-stroke is just as fierce. But in my own opinion good rule of thumb is for 4-stroke you need to go up 2 to 3 sizes from a 2-stroke. Correct me if I'm wrong guys, I've never used a 4-stroke. I have been pleased with the evolution engines so far. I have three in my planes and they start easy everytime and run flawless. Most of the others in my club use O.S. and they seem to just as reliable. So, if you have your heart set on a 4-stroke then I would go with the biggest one you can shoe horn in at least a .60. Go buy the only 40 size 4-blade prop your LHS has in stock (if they have one) I'd say a 10x4x4 or 10x6x4 but thats just a guess. Your choices are going be very limited on props but no your not barking up the wrong tree.

-Andy

PS: Sorry for the long post. I tend to ramble. (too much free time not flying)

The PTS engines on my PTS P-51 and my daughters Alpha 40 have been reliable and relatively easy to deal with ( the Alpha's engine never seemed to "walk" as badly as it did on my PTS P-51 ).

Another Evolution .46 has also been wonderful.


My Evolution 1.00NX has been a horror show!

I replaced it's carb with a new one, but I've always have had problem.

I've given up and I just put in a SuperTigre carb on it, that I had on hand.

I haven't flown it yet, but anything has to be better than the 1.00NX carb.