Hi, I'm new in the RC world and I would like to learn more about propellers. Let's say 10X7 what does it mean exactly?
The first number is the length I guess... what's the second number? and how to determine the best propeller for your plane and needs?

Thanks in advance.

10x7

10= length

7= pitch, or how many inches forward it will go in one revolution (Theoretically)


It's best to follow the recommended size range for your engine. From there you can change depending on your needs.

For example, if your engine is designed for a 10x7 but it won't slow down for landing (And it's not nose heavy which will cause excessive landing speed) you can switch to an 11x6, or even a 10x6, or maybe you want to try 3D and need a lot of pull in which case you could try a 12x3 or 4

Basic rule is for every number you increase in length, you need to decrease one in pitch

Can my OS MAX 46AX run a 12x6 propeller on my trainer?

That would be a bit much. It could turn it but would be happier with an 11x6
see page 15 of the attached manual. It says 12x6 is OK but I think that is a lot.
http://www.osengines.com/manuals/46ax-manual.pdf

Better ground clearance too.

The spool up time would be slow with a 12-6 and the top rpm would be marginal. The OS AX engines work better when they can rev up. You would get more usable power form an 11-6. An 11-5 actually works better on some trainers because you have good pull when you need it to get out of trouble. [8D]

Try a 12x4 or 12x5 on that engine. Those are the props I run on my O.S. .46 on my pulse and they are great!

Hi all,

Regarding the Props, I have a question. Yes if a prop is 10x6 naturally 10 is length and 6 is its pitch, which means it would go 6 inch per revolution. There are many props manufacturers, master airscrew etc. My question is does it make any difference if you are using wooden prop or nylon prop, another question, some props are 2 bladed, some are 3 bladed and some are 4 bladed props, does this make any difference that 2 bladed works better than 3 or 4 bladed works better than 2 bladed, pls clarify.

Thanks

You'll find as many answers to that question as there are members of this forum
for most aplications a 2 blade will work best
there are times for 3 and 4 blades but they are more for scale look and some pattern guys like them for downline braking
as far as the different brands you'll find most in the same size perform differently only you can dicide which brand works for you
beginners are better off not using wood until the prop bashing phase is over they can break on a blade of grass

The best choice for training are the black Masterairscrew props. You can bump a grass runway throwing mini-clumps of grass, the engine will quit and the prop will usually be ok. Touch any thing with wood prop which are more expensive and the prop will instantly snap in 2 making them even more expensive! The APC are the most efficient, are stronger than wood, but not as resilient as the MAS. They are a good match for 2nd type planes and sport planes. 3 or more blade props aren't efficient at the high rpms that the glow engines spin at. The only good reason to use a 3 blade is if you really need the extra 1/2" of ground clearance. [8D]

G'day Mate,
Yes it can, we run 12x6 APC on Skyraider Mk1 trainer, flys great, will give about 9,500 RPM on the ground, but we use an idle bar or hotter plug, than an OS #8.

thanks
In fact in my Kyosho Calmato trainer manual it says 12x6 propeller, but I went to buy one yesturday and the shop advisor told me it won't turn correctly on your OS 46AX engine...

G'day Mate,
Well I'm telling you it will. But if you are unsure, check out your manual, it states that the 46AX will handle up to a 12x7 prop. I'm sure your hobby shop owner knows more than OS, but just in case check it out anyway. I have flown lots of trainers for a lot of students, all different, but the best speed for a trainer was obtained with an APC 12x6 on an OS 46AX, the extra diameter helps with pulling power, but the overall speed is not excessive, & the motor does not have to gain many revs to get the plane flying again if you need to go around after a not so great approach, whereas the smaller props, eg. 11x5 or 6 need to gain a lot more revs before the plane will accelerate enough to keep flying.
And with this combination on a Skyraider Mk1, I can fly our Gold wings schedule, here in Australia with ease.
But you decide, you can always go to a smaller prop as you get better at flying.

There is another way to look at the prop material question. I personally prefer wooden props since the break on impact and transfer very little stress to the engine and the airframe. The nylon/ plastic props do hold up better to little dings and scrapes but on any decent impact (really rough trainer landing) they won't break as easily and could damage the plane when a wood prop might not.

Allan, I just bought the 12x6 prop!
I don't really trust hobby shop :P

Will try it tonight...

3 and 4 blade props aren't as efficient as 2 blades at any rpm
but in high power applications a 2 blade would be so big that the stress it puts on the engine would tear the crank apart so in that case a 2 blade wouldn't be very efficient
that is why you see 3 and 4 blades on acrobatic full scale planes and the old warbirds
on the acro planes a 2 blade puts stress on the engine from all the rapid change of directions
also as I said some pattern guy use 3 and 4 blades for the downline braking they offer
If flat out speed isn't your main goal you can try a 3 blade I run them sometimes just to do it they sound different and are quieter in most cases.

G'day again Mate,
Just be aware, that we found that a slightly hotter plug works best, here we use a Taipan green idlebar plug, but I don't know if you can get them, so just try to find a hot plug & you will see what I mean. Enjoy.

humm.. well I have the oS 3 for now...

Why do you you run a prop that runs 6500 less rpm then the engine makes peak power at just curious
An os46 can turn upwards of 17000rpm

I've never reached 17000rpms with my 46AX, and even if I could I would never run it as that limit!!
The max I reached was 14500rpm with an 11x6 but still I lowered it to 13000rpm.

I am using 10%nitro, 20%oil byron fuel with a #8 OS glow plug. Outisde temperature 33deg C

The horsepower rating at extreme rpms doesn't mean much. For the 46 AX or FX engines on an 11" prop, tune to get a touch over 14,000 rpm and your good to go. My engines seem to like to run nicely at 14,200 rpm. [8D]

I was just wondering 2000-17000 is what OS list as the pratical rpm I know these engine have been pipe to run more then that
9500 just seems way to slow for top end I can't see the engine being very happy lugging that low much less have good throttle response
I've always found that 2 strokes like to spin granted if they're way under propped there just beating the air
I've settled on the apc 10x6 for my 46 size planes I don't know if that prop gives the best numbers on paper but it gives me the shortest takeoff rolls and pulls the best for my style of flying

Hi Guys,

Great info about props about their structure etc. While reading all that, RPM came to my mind. It's very common that the smaller the engine higher the RPM's, bigger the engine lower the RPM's but higher torque right? like its discussed some engine's have highest RPM like 17,500 but being run on 14,500. I have evolution's PTS .455 engine, highest rpm is 16,500 to 17,000. My question is how would I know its running on highest RPM? is there any meter to detect, like I dont have any meter to diagnose it, how would I find out its running on that much RPM? is it it's sound or what? and what should be the lowest rpm on Idle?

Pls clarify


Thanks again

Well you always have tachometers to measure your rpm.
I usually lean the engine to the point beyond wich it just turns off. Take a measurement at that setup and this is your highest rpm.

Careful, do not run for a long time at that setting, you should lower it by 300 to 500rpm as soon as you get your reading, and this will be your optimal setting for WOT

Hey i see you are running the same set-up as me. Kyosho Calmato trainer with 46AX. I tried the 12x6 prop on for size and i wasnt comfortable with how close it was to the ground. with my landing skills i need some clearance there. I learnt with the 10x6 all along and now switched to 11x6. The 46AX seems to a lot happier with this and sounds really smooth.

BTW, did you buy yours at HobbyCentre?

G'day Mate,
Because it's on a trainer, & the last thing you want when you are learning, is too much speed, the motor will still turn faster, when the pilot is ready for more speed, but this thing still flies happily at 1/2 throttle, then they can just open it up & fly aerobatics when needed, with the same prop.