I'm a little confused now. I have people who have been in RC for a while (10+ years) telling me to keep a 10-6 prop on my Tucano .40 with a ROYAL .46 installed. I see on most charts that for regular flying, an 11-6 is the average recommended prop. Won't the Tucano fly a little lower in the RPM range with a larger prop, rather than the smaller? I have been under the impression that with a .46 you would keep a smaller prop like a 10-6 or 10-7 to get speed type performance. An 11-6 thru 11-10 would get me a more stable idle on the ground, slower approach speeds, and generally more controllability in .40-.46 size model. Is this correct? Thanks in advance.

Here's how it goes, if what your looking for is good sport performance and engine longevity...

Our engines in the 40 size range (46 included) generally perform well and live long in the 10000-13000 rpm range. We try to prop them for that. Racers and other performance folks will happily run them much faster than this, but they buy more engines than you and I.

I'm not intimately familiar with the Royal engine, but the OS and ST .46's I've run have tached in the 13K range with 11x6. Way too fast on 10x6 (14K or better!). An 11x6 running 13K static will give better than 80mph in the air with a sleek airframe, and pulls about 7# static.

If you wanted more speed, or more thrust, you'd change both the diameter and the pitch. If the aim was speed, I'd suggest trying 11x7, 10x8, 9x9. If it over or under revs with any one, change the diameter to correct this. If the aim was thrust, then something like a 12x4 or 12x5 might be in order.

Noone can tell ya what prop is best for your plane, buy a variety in the size ranges I mentioned, and try'em! You'll find one you love!

Be sure to re-tune the hs needle with each prop...

J

GIVEN THE SAME RPM:
A larger diameter/lower pitch prop will give you more pull and less top speed.
A smaller diameter/higher pitch prop will give you more speed, less pull.

The manufacturer's HP rating is almost useless to us since it may peak with a prop too large or too small to actually fly the plane.

If you're dissatisfied with your plane's performance, buy several props within a sensible range and test them.

Dr.1

Eleven ten??????

I'm going to make a wild guess that the people who know you have a reason to suggest you keep on flying slow, at high RPM, with that 10x6. When you have practiced all the maneuvers, and consistently gotten out of trouble with your present configuration, you might want a bit more speed, and the 11-6 or 7 would do that for you. And yes, a more reliable idle might result. I'm not understanding (or agreeing with) the "slower approach speeds" or "generally more controllability. "

I, for one, am not going to second-guess your experienced colleagues.

Best wishes,
Dave Olson

I never flew a tucano or Royal engine but I have several 46 size engines and they run best with 11x7 or 11x6 props.
I use 10x6 with my 40 size engines.

Appreciate the advice and info guys. My comment about "slower approach speeds" was because the Tucano tends to come in kind of hot, speedwise, and the 10x6 on a .40 or .46 on this plane seems to need a lot higher revs to keep it airborne on approach. The FOX .40 and ROYAL .46 need to be revved higher to keep running on approaches and taxing because the engine is installed inverted on this plane. I am installing a glow power system to help this out. The comment about using an 11x10 came from a prop chart of a manufacturer's .46. The Tucano is kind of touchy and will side-slip during approach/landing banking maneouvers using the 10x6 prop if you get the rpms too low on approach. It's a great aerobat. I'll be the first one to admit that I tend to over-control my bird, and don't have a lot of hours yet, but on the G3.5 Sim, I have doing better flights, approaches, and landings with higher pitch props and even those in the 11" range. I don't want it to fly like a trainer, but I don't want to high rev the engine all the time. A lot the guys giving the advice are either 4 stroke owners, or guys using .91 2 strokes, or 110 ys engines in .40 size warbirds to fly fast. So, I figured it would be good to run it by others on the forum. Thanks a mill for the info.

Help choosing the right propeller for my boat ive got a a weedeater engine in the boat i believe its in the ball park of 25-30cc the boat itself weighs 38 pounds the boat is 56 1/2 inches long from nose to rudder... anyone have any suggestions on prop type, size and pitch........HELP HELP HELP will post pics soon

duplicate post?

It's a trade off. Smaller diameter & more pitch gives you speed. Larger diameter & less pitch gives more torque. It's like driving in 5th gear vs. 3rd gear. You go faster in 5th, but you are more maneuverable and have more precise control in 3rd. Difference from the car analogy is the longer prop is more massive, has more motion arm and is therefore slower. You also get better "braking" for landings and downward legs at low throttle.

Personally, I like torque over raw speed. Doing a large loop at 1/3 throttle or a series of 100 ft hammerheads is eye-pleasing.

I have an 11x5 APCon my ThunderTiger Pro.46. Good match and still plenty fast on a Saratoga 40.