Octura M or X

[jetskier]

What's the difference between M445 and X445 all the spec seems the same.
Thanks,

[785boats]

In the link below, if you look at the X series at the top of the page & compare them with the M series lower down you will see that the tongues have been removed on the M series. That's basically the difference.
This unloads the prop a bit & therefore the motor can rev a bit faster & therefore the boat runs a bit faster, & should have a slightly less amp draw as a byproduct.

http://www.offshoreelectrics.com/cat...ura+Propellers

[J.W. Pepper]

What's the difference between M445 and X445 all the spec seems the same.
Thanks,

Found this explanation while searching for props for my IM-31... add's a little more detail to 785boats' post.

An Octura M series prop is basically a de-tongued (de-eared) X series. The M series gives you higher top RPM, but less torque or off the line grunt. They also produce less lift, less prop walk & less prop torque than the same size X series prop. It's known as a cleaver style propeller.

Found that info here... http://www.funrcboats.com/ProductInf...oductid=OCM440

Hey 785boats... What the heck is prop walk?? And what do they mean by a "cleaver style prop"?? -- Lotta people on this forum recommend a M445 for the PB IM-31's, so needless to say I have reason for wanting to learn why.

Also, I attached a prop diagram, think I found it here... http://www.offshoreelectrics.com/inf...s_Tips_&_Info_ - tons of great info, highly recommend you spend some time there. The "ears" 785 referred to are at the bottom of the tongue / very beginning of the leading edge.

[TheShaughnessy]

Prop walk is when the thrust cone inherently steers the boat to one direction. This usually happens when using large props. How large depends on the size of the hull. A cleaver style prop refers to the shape of the blade

[wayne middlemiss]

the idea behind the de tounged m series or x series is to remove an area of the prop that acts as a govenor and basicly increase the leading edge pitch so it allows more water on the prop to give you more positives with the prop= better boat performance.

[J.W. Pepper]

Prop walk is when the thrust cone inherently steers the boat to one direction. This usually happens when using large props. How large depends on the size of the hull. A cleaver style prop refers to the shape of the blade

Is the thrust cone part of / inside the concave part of the prop??

How does one determine what is considered a large prop for a given hull size?? Also, does it matter if the hull is a mono or a cat??

[TheShaughnessy]

The thrust cone isn't a part of the prop more a function of it. 47mm would be considered on the large size for a 27-30 inch hull. Yes different hull types react differently. Have a look at sweet accords gallery, should be a pic illustrating a thrust cone.

[TheShaughnessy]

http://rcraceboats.webnode.gr/news/gas-prop-essentials/

Check out the pic at the bottom. Should give you the jist of prop wash/ thrust cone

[jetskier]

great info guys. thanks again

[J.W. Pepper]

http://rcraceboats.webnode.gr/news/gas-prop-essentials/

Check out the pic at the bottom. Should give you the jist of prop wash/ thrust cone

Well, I just got one of my questions answered... http://rcraceboats.webnode.gr/news/propwalk/

Then discovered that I have one hella-va lot to learn Example I heard the term chine walking and thought to myself... great, wt* does that mean?? Still don't know, but at least now I know what the hell the chine is, that's a good place to start.

Thank you so much for the link, wish more people would do that, I love to learn, point me in the right direction and I'll take of the rest. Trust me, I will be spending quite a bit of time there the next couple / three / four days, a ton of info to absorb.

[wayne middlemiss]

the prop info has been used from marty davis site www.rcboat.com nothing new there.

corection guy's that site is no longer but go to this www engine analysys software.com and look in the old tech files and other info.

[Randy Rapedius]

One thing to remember is that the M series might give you a little extra top end speed however, it could cause cornering handling issues especially in a mono.

[hydro_pyro]

"Prop walking" is the effect of a surfacing prop exerting a slightly "sideways" thrust torque due to the prop being half-submerged, causing the back of the boat to skate sideways or strafe across the water. The "taller" the prop's pitch and the higher it's run, the worse the effect can be. Also called "paddle-wheeling."

"Chine walking" is what mono Vee hulls sometimes do at high speeds when there's a small area of the hull in the water. It pitches side-to-side, or "chine-to-chine", trying to find balance. On a 1:1 performance boat, the driver uses steering input to keep it balanced on the keel or pad.

[jetskier]

"Prop walking" is the effect of a surfacing prop exerting a slightly "sideways" thrust torque due to the prop being half-submerged, causing the back of the boat to skate sideways or strafe across the water. The "taller" the prop's pitch and the higher it's run, the worse the effect can be. Also called "paddle-wheeling."

"Chine walking" is what mono Vee hulls sometimes do at high speeds when there's a small area of the hull in the water. It pitches side-to-side, or "chine-to-chine", trying to find balance. On a 1:1 performance boat, the driver uses steering input to keep it balanced on the keel or pad.

good inputs.
my Kawi SXR 800 chine walks like crazy on glass, give it a little chop it handles like a dream, choppier the better till it gets too crazy then your hanging on for dear life.

[Brushless55]

Great info in here!

[785boats]

One thing to remember is that the M series might give you a little extra top end speed however, it could cause cornering handling issues especially in a mono.

Randy. I've never heard that before.
Could you expand on that a bit please? I'm always eager to learn.

[J.W. Pepper]

One thing to remember is that the M series might give you a little extra top end speed however, it could cause cornering handling issues especially in a mono.

Is that caused by the fact that it's been de-tongued??

I got out my prop can and started doing comparisons, I don't have any "M" series props, but a side-by-side comparison of the PB 1.6 x 2.5 (same as Prather S215) & one of Jan's x440 CNC'ed props allowed me to see enough of a diffrence to understand what they mean when they say the prop has been de-tongued (de-eared).

[785boats]

J.W. Pepper.

Is that caused by the fact that it's been de-tongued??

That must be the case but I'm not sure how & what the effects are. We'll have to wait for Randy.

You said in one of your posts that all you wanted was to be pointed in the right direction.
Let me point you here.
http://www.fastelectrics.net/fe_manual.php
If you read each chapter in the manual you will be a long way to understanding the idiosyncrasies of this sport. It's certainly helped me.
Since we're talking props, start with the chapter 'Propeller Effects'.
Cheers.
Paul.

[NativePaul]

Thanks for the link Paul.

I haven't noticed any handling issues with M series props, but all boats are different, sometimes even ones that came out of the same mould. While nearly all my props are de-tongued to some extent, I don't have many actual M series props, as I generally buy X series and cut to my desired shape, but I have noticed that M seem to have thicker blades than X, so if you are just doing basic sharpening not thinning down to the root there is the potential for more prop walk and torque roll, quite a small effect though I would have thought it wouldn't be noticeable. Another possibility is if an M series was either not big enough for the hull and was cavitating coming out of the bends, when it hooks up the sudden onset of thrust, lift, torque and prop walk could bring with it some bad handling traits that would be fixed by a little more blade area from an X, or a bigger M to stop the initial cavitation and keep things smooth.

There could well be something I haven't thought of or experienced maybe something particular to un-stepped monos that I am not very familiar with, I also await Randy's comment as like the other Paul I am always eager to learn.

[Randy Rapedius]

The tongue on the X series are there to assist in getting the hull on plane and the added blade area makes for smoother turning. Some monos need cornering stability. At top speed, the tongues actually hinder speed. This is why people like to remove them. Last year I took a stock x470/3 for a 90 nitro mono and removed the tongues. The boat was ballistic fast in the straights but in the corners it was squirrely. Put the stock prop back on and it cornered like a dream. Not always does removing the tongue improve over all performance. It's a balance. There are no guarantees that removing the tongues or going from an X to a M Octura series prop will help or hinder. Test, test, and test some more.

[mtbenjamin77]

Its a balance. Usually remove slightly more tongue than the m series and it seems to work well for my FE setups

[mtbenjamin77]

Knowing how to work props is a priceless skill. I can usually run only two different props on the same setup and know how to custom cut a prop to maximize performance based on the handling characteristics of the two

[Brushless55]

so are M props not a good choice for Mono hulls?
I was going to try a M445 on my PSpec Mono next time out and now I'm going to put a X445 on it

[Doug Smock]

FWIW, M series props or X series that I have removed the entire tongue on are all I run on FE monos.

[Brushless55]

FWIW, M series props or X series that I have removed the entire tongue on are all I run on FE monos.

ok hold up..
I am trying to wrap my brain around what you guys are saying...
so the M props as they are could even need more tongue removed and they will run great on monos??

[Doug Smock]

Todd,
Do they "need" more tongue removed? It depends on the boat, RPM, etc. Yes they will run great on monos if they are ''great running" monos.
http://www.youtube.com/watch?v=Ahy6nfMKSx0

Like Randy said, test, test, and test some more. There is no silver bullet one cut fits all.
Randy's 90 mono experience is going to differ from your P Limited mono experience. They are apples and oranges. (different hulls different power requirements)

[Brushless55]

Todd,
Do they "need" more tongue removed? It depends on the boat, RPM, etc. Yes they will run great on monos if they are ''great running" monos.
http://www.youtube.com/watch?v=Ahy6nfMKSx0

Like Randy said, test, test, and test some more. There is no silver bullet one cut fits all.
Randy's 90 mono experience is going to differ from your P Limited mono experience. They are apples and oranges. (different hulls different power requirements)

that one in the video looks really good...
turns nice!

[785boats]

Thanks guys.
I run a lot of de-tongued X series & also the M series & haven't noticed any bad behaviour. That's why I was curious. Thanks again for the explanation. No doubt I'll come across the problem one day.

[J.W. Pepper]

Thanks for the link Paul.

I haven't noticed any handling issues with M series props, but all boats are different, sometimes even ones that came out of the same mould. While nearly all my props are de-tongued to some extent, I don't have many actual M series props, as I generally buy X series and cut to my desired shape, but I have noticed that M seem to have thicker blades than X, so if you are just doing basic sharpening not thinning down to the root there is the potential for more prop walk and torque roll, quite a small effect though I would have thought it wouldn't be noticeable. Another possibility is if an M series was either not big enough for the hull and was cavitating coming out of the bends, when it hooks up the sudden onset of thrust, lift, torque and prop walk could bring with it some bad handling traits that would be fixed by a little more blade area from an X, or a bigger M to stop the initial cavitation and keep things smooth.

There could well be something I haven't thought of or experienced maybe something particular to un-stepped monos that I am not very familiar with, I also await Randy's comment as like the other Paul I am always eager to learn.

Thanks for the link Paul... +1

[Accessable]

This is all well and good for monos.
So what's the go for serious outboard FE F1 tunnels?
I currently have a range of Octura X series props ranging from X430 through all variations to X450.
All are balanced and sharpened per me.
I currently have a Thunder Power 6S 8G 70C LiPo setup running thru a Swordfish 300 Pro Plus so power is NOT an issue.
This is delivering to a variety of TP 4060 (1800 - 2100 Kv) brushless on a TFL OB leg.
BTW: From my ski race experience: There is a little thing called the "paddle wheel effect".
This is a semi-surfacing propeller's desire to "walk" sideways" across the water at the same time as pushing the boat forwards. - aka as "chine walking".
I've experienced this problem 1st hand having done a 180 loop at 100+ MPH.
My once dislocated shoulder still aches!
Dual counter-rotating propellers or offsetting the horsepower supply sorts the problem out.
WTF would I know???