Prop choices for .020, .049 and .061
 

Hello! Just wanted to get some prop recommendations for the PeeWee .020, the Cox reedie .049, Norvel/Areo/Ame .049 r/c and Norvel revlite .061 r/c. I currently have examples of each of these engines and am in the planning stages of some projects (some may recall I'm fixin' to build some PZL P.11 parasol-wing planes).

Anywho, any prop recommendations would be appreciated. Keep in mind I'm interested in slow (the slower the better) leisurely flight rather than all out speed or aerobatics. As always, thanks in advance.

RE: Prop choices for .020, .049 and .061
 

Since your scratch building, the prop your looking for is likely to be found by you. A good starting point is to use the largest prop in the manufacturors recommended range. Reducing the pitch will allow the larger props to give more rpm and allow the use of larger diameter more effiecent props. The norvel engines need to turn some rpm's to make power. I hope this helps.

An example for a .46- (not accurate---exaggerated for clarity)
10x7 - 16000rpm fast prop (100mph) 6lbs thrust
12x4 - 16000rpm slow and powerful prop (60mph) 12lbs thrust

RE: Prop choices for .020, .049 and .061
 

Let's go with your .46 example....So if I have a fairly heavy model then it would be better to go for the 12lb thrust and the 12X4 instead of the 10X7? But then I don't understand why you have 16,000 rpm listed for both? Wouldn't the 12X4 turn slower than the 16,000 if the 10X7 turns 16,000?

RE: Prop choices for .020, .049 and .061
 

meowy,

A good place to start is the Cox 5x2 for the .020. I understand the APC 5.2x2 is alos overy good. For the Cox .049 it depends on the plane and engine set up. Anything from 5x3 to 7x3! The Norvels like to sing but again anything from 5x3 black Cox to 6x3. Being you have the .061 the 6x3 should work for you. also since you are talking "slow flight" maybe add a couple of head gaskets to the Norvel and go up in prop size alittle.

Later,
Tim

RE: Prop choices for .020, .049 and .061
 

Meowy84, in Ptulmer's example the RPM's are the same because the loading is the same. Lower pitch will load the engine less. The rule of thumb is 1 pitch is roughly equivalent to 1" of diameter. So a 10X7 and a 12X4 give about the same loading and about the same RPMs. A heavier model doesn't necessarily need more thrust unless you are looking for better vertical. Heavier models often require more airspeed to fly than a lighter model. A good example is in some geared electric models where the quest for thrust has become so extreme that they hardly fly on the wing anymore, and have to be built extremely light so that they can fly on the prop. Your best bet is to try a range of props with the knowledge that if, after a test flight, you want more thrust you need to go up in diameter and down in pitch and vice versa for speed.

A PeeWee .020 comes with a 4.5X2 prop, but can spin up to a 5X3. A Norvel .061 can use anything from a 5X3 to 6X4. I prefer an APC 6X2 for the .061, but a COX 5X3 or an APC 5.7X3 work well too.

RE: Prop choices for .020, .049 and .061
 

I sat here and wrote a long response, saw a notice come in and now all I need to do is agree with Bipe!:D
The norvel 061 RIPS with a cox 5x3. Slow it down a little with the 6x2. The cox reedie's run extremely well with the 5x3. Final performance is difficult to predict because it depends on the airplane. Like Bipe says, bring some different choices and try them all.

RE: Prop choices for .020, .049 and .061
 

My Goldberg Ranger 42 foamy flies very well with full-size gear (RET) and a Norvel .049 with a Cox black 5X3 @ 17,500 on 25%. I also have one in a Astro Flite Mini Challenger 56" sailplane that swings a 8X4 Cox gray @ 7,500 on 15% fuel and 3 head shims. My buddy MikeSell has a clipped-wing Herr Cub with a .061 that flat cooks with a Cox 6X3 & 35% heli fuel.

RE: Prop choices for .020, .049 and .061
 

As always, the input of the gurus is appreciated. :) Thanks guys.