Gray Beard

My Feedback: (-1)

A quick heads up on your engine and prop. Going up in pitch you lost some thrust, it wasn't a big change but it was a change. Your needle was too far out so when you turned it out more you fattened up/richened the engine so you lost more RPMs. Turning it in leans it and you gain rpms. You want to listen to the engine and got to the top rpm then back off/turn the needle out until you hear a drop in rpms. Someone else can tell you how to pinch test the engine.
OK, rule of thumb for prop selection and testing. A longer prop with a lower pitch will give you better thrust but a slower top speed. A smaller prop with more pitch will give you more speed but less thrust. This will give you longer run outs at take off and less vertical pull but a faster plane. We use the smaller props with a lot of pitch for racing and pattern. If you look in a tower book at the props they lable what some of the props are for, it's a good idea to look at them. A 3-D pilot runs a long prop with very little pitch.
Just food for thought.

SushiSeeker

Understand. I hadn't considered that the power curve on an electric was not flat, but it makes sense. My only experience with electrics is on my Mistral glider. I use the motor to haul it up into the thermals and shut it down.

CGRetired

My Feedback: (1)

Yeah, that was the very first issue I noticed when flying electric. It can easily be overcome with... well, throttle management!!

CGr.

armody

My Feedback: (10)

Thanks Gray Beard,

I've been using mostly 11 size props, I'm not sure if I ever used 10 diameter prop. As I mentioned I'm currently Using 11X7, I love vertical climb and .46 size engine can give you a good vertical but not unlimited. I like speed of the planes but I'm not very crazy for them, more crazy I'm for is vertical climb. So rather than using 11X7 I should be using 10X7? cos currently I'm using 11X7 and cos of today I could not fly, and bummer, I should have used the longer pliers to hold the crankshaft nut and unscrew the prop nut, which I did at home not at the flying field.

Anyway for more vertical I gotta use lower diameter prop with higher pitch? and with WOT take off, I'd be flying 1/2 throttle for that plane, which I'm gonna do next week hopefully.

Gray Beard

My Feedback: (-1)

No, stick with the 11 and try a 4 or 5 pitch Some people, not myself, use a 12X4. Longer prop with a lower pitch gives you more torque. I no longer fly anything of my own with the .46 but when I was into fun fly events I used only the .46 engines, mostly the OS .46 LAs and the GP Up-Roar plane. I did have some of the small 40 size planes like the Extra and Super Sportster that I used some of the better OS engines like the FX. After a lot of testing I sort of stuck with the APC 11X6 but it depends a lot on the plane itself. If you want to go faster then try the 10s with 8 or 10 pitch. It's up to the pilot to test props on there planes/engines to discover what they, the Pilots like best. Any prop in the engines prop range will fly the plane, it's up to you to test props until YOU find the prop that will fly the plane the way YOU want. Prop testing is the only way to find out what YOU like.
Hold the prop and loosen the crank nut, hold the prop and tighten the nut. If you want to hold the engine from turning buy a piston stop, it's just a glow plug with a soft metal rod in the center to keep the engine from rolling over. I make my own but almost never need to use one. A wrench on the thrust washer just boogers up the washer!!!

armody

My Feedback: (10)

Gray Beard,


Your suggesting that I should keep the dia to 11 but reduce the pitch from 7 to 5 or 4 which would reduce the speed but increase the thrust, reducing the speed means reducing the rpms too?

Larger the pitch higher the speed and smaller the pitch lower the speed but thrust would increase, and increase in thrust would help with vertical climb as well?


I don't wanna take this topic from Throttle stick setting to prop setting but just clearing my thoughts up.

I'd still like to have more inputs about throttle.

Gray Beard

My Feedback: (-1)

Throttle stick goes up and down, back and forth. Forward makes the engine go faster, back makes the engine go slower. Play with it until you get the hang of it!!

armody

My Feedback: (10)

I'm gonna buy me APC 11X5 and 11X4 and try both of 'em especially their thrust & vertical climb. Should I go for APC or Master Airscrew? in fact I had been using APC mostly, I like MAS's S-2 Scimitar series as well. With these 2 props, I'm gonna play with the throttle and vertical and slow fly byes. Tomorrow my new ASP .52 is being delivered and for break in I'm using MAS 11X7 and I bought 11X8 for the future use, but as of today's discussion I'm gonna change APC 11X8 to 12X6, also I'm kinda indecisive between these 2 planes.

http://www.nitroplanes.com/90a119y-g...yellow-v2.html

http://www.nitroplanes.com/20redyak523d.html

I'd certainly post the results of 11X5.

Thanks Gray Beard

ameyam

A lower pitch prop has its advantages. It gives more static thrust, desirable for 3D. When my mentor took up my Reactor 46 for the first time, the throttle got stuck at WOT. (The EZ connector had come undone). With no option left, we flew it till the engine cut. We did loop after loop trying to have it cut or run out of fuel. Normally, this would have caused flutter in a 3D airplane and trashed it. But I was using a 13x4 prop, we noticed a tendency not to gain speed even though at WOT. Got my Reactor back in one piece! As a bonus, it checked my plumbing thoroughly and I have good pullout in hover

Ameyam

CGRetired

My Feedback: (1)

There are both advantages and disadvantages to changing prop pitch.

I was "playing" with my Skylark 70 a couple weeks ago and wanted to see how the plane would react with a 15-4 that I had in my prop box. What I had on the plane was a 15-8. The engine is an OS .75 AX, which flew just fine, by the way. But, I was looking to see how it would react on verticals.

The engine (prop) noise was louder because the RPM increased quite a bit. The takeoff roll when going to full throttle almost immediately (fast gradual.. if there is such a term.. ), was very short.. no surprise there. Verticals were "unlimited".. again, no surprise there.

But, the differences were not something that I would want to keep that prop on that engine / plane combination. The noise level was high enough to cause problems, especially when going from half to full throttle in flight, and pulling to a vertical climb.

So, as I said, there are advantages to switching over to lower pitch, but, there is also a down side. For you guys flying out in the desert, quite a few of us on the east coast envy that freedom. But we have neighbors (one in particular that complains about everything) and would hate to lose the field because of a ripping prop noise causing complaints to the Forestry people or to our local politician.

I don't do 3D so the hovering part of it just doesn't matter to me. But, I'm sure that with that engine/prop combination, the Skylark would hover. But, again, it's pretty loud as compared to the old standby 15-8 which keeps the RPM's down below 10,000 and gives me great performance.

CGr.

sandal

Going from a 15x8 to a 15x4 will, as you noticed, increase rpms significantly. A 15x4 needs less engine power than a 15x8 to turn at the same rpm. To keep rpms the same, you need to increase diameter. A 16x6 will load the engine about the same as a 15x8, but give more thrust (and lower top speed).

CGRetired

My Feedback: (1)

Yes, I realize that. But, what I had on hand was the 15-4 and what I was looking for was to see what differences in the vertical I would get with the 4" pitch. I am going back to the 15-8. As far as I am concerned, the noise differences far out weighed the benefits.

I have a box full of props ranging in size from a pretty small electric power prop to a 16-8. The 16-8 is for my OS 1.20 AX which spins that very well with a minimum of noise.

The point of my post is that decreasing pitch has some down sides to it. And, as you pointed out, increasing the diameter helps in that respect. But, again, even with the collection of props that I have accumulated over the years, and it's fairly considerable, what I had in the size range for the OS .75 AX was the 15-4 and the 15-8. I have smaller diameter of course, but that would be a waste of time on that engine.

CGr.

sandal

Now I understand what you meant. I agree with you on the downsides, especially when it comes to noise. And I believe it doesn't only apply to full throttle flight. To fly at a certain speed, a 15x4 needs higher rpm than a 15x8, so I believe that it produced more noise all the time, not only when running at full throttle. In my experience, a medium pitch prop sounds softer than a low pitch prop when flying at "medium cruise speed", do you agree?

CGRetired

My Feedback: (1)

Oh, absolutely. The noise you hear are both a combination of prop speed as well as exhaust noise. But, for a given throttle setting, your RPM may be higher than it was with a higher pitch because the engine is working less, and will turn at a higher RPM.

Prop tip speed is a real problem in some areas. We have neighbors, well, one in particular, that complains about everything. It seems that he is unhappy in the fact that the Forestry folks drive by his home on the way to the field to fly their air tanker. We live in the middle of the "Pine Barrens" where there is a large forest area with a lot of, well, pine trees and scrub pines. So, they keep a pair of air-tankers at the field during peak months of potential forest fires. So, the noise generated from the full scale aircraft as well as the cars and trucks (fuel and water tankers) drive past his house, bothers him.

I've been at his house when we were flying and could not hear a darned thing. I brougt a sound meter to measure the background noise when we were flying.. and there was nothing to detect. But, he knows when we are there and seems to want to complain about us, even though we don't drive by his house (we have a separate entrance about a mile east of his house) and don't fly over that portion of our field.

But, we've instituted noise limits in the "just in case" mode, to prevent problems from coming up.

Anyway, this is drifting away from the point of this post and I don't want to hijack it any further.

Thanks for the input, though. Any of this sort of information is helpful for those that are thinking of experimenting. There is more than aircraft performance to think about when changing props. And, as I said, I envy those that fly at fields that are well away from populated areas.

CGr.

armody

My Feedback: (10)

Ameyam, CGRetired, sandal,

You guys came out with great input, appreciate it. Finally today I have bought 2 props APC 11X5 and 1 APC 11X4 for my Magnum .46 XLS on Strega. I already installed 11X5 on it and honestly speaking I don't wanna go below 5 but in case I bought 11X4 as well. I have set up the high needle valve, it's running pretty well, on nose up, revs do increase but somehow I'm not getting the sound of the full rpms which I'm used to, I still feel it's kinda lean and if I try run it lil more rich, it tends to bog down, so it means that the highest rpms what I'm supposed to get, I'm getting, what do y'all say?

For my ASP .52 I got it today, as I had another topic for that engine, I'm gonna update it and let you know the details and pix of the engine there.

Here is the link http://www.rcuniverse.com/forum/m_10220201/tm.htm



Mody

armody

My Feedback: (10)

Some pix of my ASP .52 which I posted in other post that somehow does not have the name ASP engraved on it. A video to of breaking in, which is not complete yet, I'd be breaking it in on weekend, but on rpm my bench would easily be 70 to 90lbs and that engine was moving it and it started scooting so I had to put my foot on it.

Why the engine does not have ASP name engraved on it I don't know, if somebody knows why is it so please lemme know.

Thanks

Here is a short video of breaking in process -> http://www.youtube.com/watch?v=kj1HEb2A04Q

ameyam

Ok, I always wanted to ask this question- what difference does and APC make over a MAS of the same size (other than that the APC breaks more often)?

Ameyam

CGRetired

My Feedback: (1)

For the most part, it comes down to personal choice, just like radio systems and engines.

You can break an APC just as easily as you can a wooden MAS if you hit the ground with the prop on landing. That's just a way of life. And, that's why a lot of us have a quite large collection of props.. you know.. like potato chips, you can't buy just one!!!

There was a time when I was buying 10-7's by the bag full!!!

CGr.

Gray Beard

My Feedback: (-1)

Some makes and material works better then others, more efficient. APC is a much more efficient than a MAS. If you are off to the side of a running engine, {not a great idea but it happens} and the engine is brought up to full RPM you can see the MAS flex due to the material it's made of, that robs power. No prop is made or designed to be hitting the ground but I use MAS on trainers and they last a very long time even with all the ground strikes. Other then that I don't use them. Wood props are usually lighter and will spool up faster but some engines, for the most part four strokes, will idle better with a prop with more weight. There are a number of good articles writen about props and there selection. If you are breaking props then you are doing something wrong, they are made to move air, not dirt. I did at one point teach three people to fly using the same old trainer and I only used the one MAS prop. I think that was some sort of record!!

CGRetired

My Feedback: (1)

Gene: I moved a lot of dirt in my learning days.. I blamed on the soft landing gear that would squish down when I touched down for a landing.. but now that I have all this experience.. I can say it was my landing technique.... or whatever you would call it.

For me, I use APC because.. and we "hear" this often, because my instructor used APC and because that's what the local hobby shop had in stock.

CGr.

armody

My Feedback: (10)

I heard that MAS props tend to bend unlike APC. APC's are more rugged and solid. I enjoy APC on the other hand I also wanna try MAS. In the past I used the Thunder Tiger's 11X7.7 and I still have it with no broken or chipped tips. I still have Xoar 12X6 or 12X7, still in good condition, and I gotta say TT and Xoar they are really good props. I'd certainly use 'em.

Gray Beard

My Feedback: (-1)

Dick, I think I used the same LG as you did but at the time I kept a box of the APCs on hand. The small sizes are cheap so a fist full doesn't cost much. From 12 inch on they start to cost but I do try to always buy at least one every trip to the LHS, Usually 15 and 16 inch.
I haven't tried any of the small Xoars but I hear good things about them. I do use Xoars but the smallest ones I have are 20 inch. Compared to the Zingers putting on a Xoar is like getting a bigger engine!! I still use Zingers on all new planes until I have the plane/landing figured out. I tend to nip the props on landings with a new plane. Must be that crappy LG CG mentioned??
I can't stress prop testing enough. You must try them all in different sizes and pitch. I do have a number of the MAS in my filght box. I haven't found any of my planes that fly the way I like with one but if I have a bad prop day at least I have a few spares that will work. Keeps me from having to go home early.

CGRetired

My Feedback: (1)

crappy landing gear. I hear ya.. ha..

Every time I put together a new plane (I say it that way so as not to offend real builders out there by saying "built an ARF".. ) I usually spend the first day at the field with the new plane setting trims, then testing props, then just learning to fly the new beastie. However, often, I settle in on a prop and fly with it for a while, then start the experimentation all over again, as I did with that 15-4 prop (which is coming off, by the way, and getting replaced with my previous choice, the 15-8 that was just fine).

But, as you said, it's easy to collect 10-5's and so on, because they are couple of bucks each, but when we start moving up to the 15, 16 inch'ers, well now, we are beginning to get into a bit larger propellor budget. But, as you, I have a box, actually a drawer from my parts bin (about 20 X 30 X 6 inches) that is absolutely stuffed with props of all sizes, with several makes. But, with the LHS (now closed.. [&o] ) carrying only APC with a few MAS but only in the smaller sizes, well, that stock is mainly APC.

I am buying mostly on-line for now, usually from Tower and Horizon, so when I do, naturally, but with consumables (such as a prop or perhaps glow plugs), I buy more than just one.

Now for my Venus II and Excelleron 90 pattern planes, well, those both have OS 1.20 AX engines and use the 16-8 prop. That was also decided by experimentation, but not very much. I went with what was recommended and flew it and found that it gave me what I needed for pattern, so I just stuck with it. Perhaps there are better choices, but the 16-8 works and I just don't want to spend extra bucks just to "see if" something else might work slightly better. And, they are quiet, which is a good thing at our field.

Speaking of that, we (our club) did a voluntary noise check. We have three different noise meters, I have one which is a pretty nice calibrated hand held unit. We use the AMA and the NSRCA standards and test practices to determine the noise level or our aircraft, and log it. When one is above the noise limits, we try to get the noise down by swapping out props with what we have in our stash. Then, the owner will use our prop until he/she can get one of their own. We are trying to nip any problems in the bud before the neighbor(s) resort to calling their political representatives, which usually is not good for any club.

Anyway, I seem to be long winded this AM.. must be this German coffee I brought back from Munich two weeks ago. Yum!!!

Later.

Dick.

Gray Beard

My Feedback: (-1)

I built a very nice CG Extra as a gift to an old friend. He drove down from Oregon to pick it up. The plane was worth the trip. I took him out to the Lake Bed for the maiden. After I flew it I handed it off to him and the first three flights all he did was shoot touch and goes, no stunts at all?? I asked him about it and he just smiled at me and said you have to be able to land them before you fly them!! That was good advise.
I have flown at events with noise restrictions and never had a problem but I have seen/heard several. Usually in the giant scales. Different brands of props in the same size can create a lot of noise, even props of the same size and make can be different. Last year a fellow came out to the lake bed with a 42% Extra that he installed new cans on. Loud doesn't begin to describe it!! After two flights he changed props, same size, different make and the plane wasn't loud at all. The sonic boom from the first prop was ear shattering!!
There is one field here that noise is a problem but I never go across town to fly. I do go there for events but just to watch. Homes have encroached upon it so they have to really watch it!
Gene

CGRetired

My Feedback: (1)

Gene: Yeah, there are differences and it seems that every time there is a sensitivity to noise, someone will show up with a large scale that makes a lot of noise.

BUT, a couple years ago, a member of long standing, showed up with a flying wing that has set several records for speed. It was a flying wing type aircraft with a small engine.. I don't know what size it was, but .40 size seems to come to mind. He has a tuned pipe on the thing and a very small prop. It was launched by a sling-shot type of device and took some time to climb to altitude.

Once up at about 100 feet, he pushed the throttle to full.. we thought it was full when he launched it.. and did a rather large turn as it sped up.

He went way to the east, slowly turned in toward the field and, at about 50 feet, went across at slightly over 200 miles per hour. We had a police RADAR so we were able to read the speed as he passed by.

The noise that thing made was piercing, and very loud. He estimated the engine RPM at somewhere around 20,000.. and I can believe that.

He made three orbits, each at somewhere around 200 miles per hour. His top speed was 203 mph. We could hear the ripping sound as it echoed back from the woods about 500 yards away. He freely admitted that it was mostly prop noise, but there was some exhaust noise.... BUT, I gotta admit, it was pretty thrilling. Very impressive, no doubt about it.

CGr.