What is the advantage of useing a 13X6-10 prop over say a 13X6?

I have seem them before but never thought to ask. Today when I was in the LHS I did ask but then I was reminded that nobody in there flies. There should be a law that requires having an R/C flyer in a store selling R/C planes.

OK, forget that law quote. I don't want to start a conversation on constitutional law. I just want to find out if I should consider using a 6-10 prop or not. I have 2 and 4 stroke engines, ranging from .15 2 stroke up to .91 4 stroke.

Never heard of a 13x6-10 prop. you mean a 13x10 for example or (13x7, 13x8, 13x9 etc.) instead of a 13x6? Also, What brand are you referring to?

I need clarification to properly answer your question---

Consequently, I go to Hobby People and just ask them if I can come behind the counter because they never kno what I am asking for or talking about [X(]

Moki
Irvine
Jett

They just push Magnums at me

Salt, there is indeed such a thing, go here for an explanation, http://www.zingerpropeller.com/Dual%20Pitch.htm

Hobbsy - so does that mean its a "compound" pitch, get more coarse towards the tip.

Yes, it has 6 inches of pitch at the root and 10 inches of pitch at the tip.

This dual-pitch sounds pretty odd to me.

If you look at a conventional (constant pitch) prop, the angle of the blade reduces as you move further away from the hub (towards the tip). This provides a constant aerodynamic pitch which means that, at flying speeds, the effective angle of attack of that blade is the same across its entire span.

If you use one of these dual-pitch props, the tip will be operating at a higher angle of attack than the root. This means that if the aircraft is flying such that the tip section sees a slip of just 15%, then the root will be operating at an effective *negative* angle of attack -- possibly even stalled.

Of course, when the plane is static or moving slowly, the highly angled root section of a conventional prop is usually operating in a stalled condition -- producing lots of drag and little thrust. I can see that these dual-pitch props seek to unstall the inner section of the blades sooner than happens with a constant-pitch prop and that might work -- but I'm still a little skeptical because...

The reality is that the tips of a prop do most of the work anyway so it doesn't much matter what the root pitch is. Do the math and you'll see that the inner-most 50% of the blade really just comes along for the ride.

These props sound like a triumph of marketing over substance :-)

Razor, If you go the Hobby People down south, in El Cajon, I remember the guys in there not knowing too much. The one up north, on Convoy, had guys with plenty of knowledge. However, I understand things have changed a lot since I left that area so who knows what's going on now.

Hobbsy, I'll check the website; thanks for the info.

Hi!
Used those (zinger wood) 20 years ago .....was good.... but modern props like APC is much better!
Regards!
Jan K
Sweden

I think wood props still have a place in R/C flying, just like the APC props.

I was looking at the K series by MasterAirscrew anyway.

I read the link and now know what the dual pitch is but that still doesn't tell me why I would want to use one, or why not. I guess my question is are the dual pitch props better for sport flying, or should I stick with a single pitch prop?

[sm=confused.gif]

The way I interpret the function of the dual-pitch prop is that they *should* provide more thrust when the plane is flying slowly (such as on take-off or when climbing steeply). They do this by ensuring that the root section of the blades isn't stalled like on a normal prop.

When the root of the blades is stalled they contribute very little to the thrust but absorb power from the engine.

A dual pitch prop *should* allow the engine to spool up more quickly than a constant-pitch one and that should mean that your engine produces more static thrust so that the plane will accelerate more quickly and climb more steeply.

The downside will be a performance hit at high-speed.

Or I could be completely wrong :-)

more prop blast at the outer radius of the prop arc clears fuselage while placing less load on engine than 13/10 would. this is just what I heard and am not 100% sure.