I have a hangar nine Ultra stick .40 with a thunder tiger pro .46 on it. i use 10% cool and have a 11*4 prop( recommended by a friend)
the elevation of potch(where I'm flying) is about 5000ft. what is a good size prop to get good vertical power on my plane?performance its not too bad at the moment, were just wondering if there is another size prop that will make it even better?

verticle performance on a .46 Try a APC 12X4

Unlimited vertical w/ my H-9 Twist/magnum .50 BlueHead/APC 12x4/ 10% PowerMaster.[sm=thumbup.gif] Rob

Ya know I didn't really think there would be that much difference in performance between 10% & 15% fuels when being used in little .46 size sport engines. Just recently I realized how wrong I was. I always buy 15%, usually Wildcat because that is the best priced around here & 30% Cool Power for the Saito. A friend that flies helis gave me a full gallon of 10% that he wasn't going to use, so I said sure I'll burn it, won't even notice it with my little engines. Lol, As soon as I started burning it I noticed that all my OS .46's & my Tower .46 seemed like they needed to be re-tuned or something. It felt like I lost the top 20% of my power-band. Now these engines never need tuning, they run great all the time. I finally remembered I was running that 10% he gave me so I ran a tank of 15% just to see & sure enough all my power came back! So apparently even as little as a 5% increase in Nitro makes a significant difference in power. We get real good vertical performance on my WM Ultimate 40 with an OS .46FXI swinging an APC 11X6 with 15% fuel.

I'll bet you pick up performance just going to 15% fuel. Then if you still need more vertical you could try that APC 12X4 prop.

I don't think the price difference for the 15% is but a buck or two at the very most. I have a lot of friends with the TT .46 PRO engine & they all run great on 15%. They run so good I've come to like them better than my OS engines. I think they give more bang for your buck!

I have tried that exact set up and I liked an 11x6 the 12x4 seemed sluggish to me

Prop selection is directly determined by flying style. If you want to go fast with it go for a 11x7 11x8 but if you want pulling power (aka unlimited virtical) go for a shalower pitch like an APC 12x4 or the ultimate .46 sized prop an APC 12.25x3.75 and it will be about as good as you can get for that engine. Definately bump up your Nitro to 15% as you will be pleasantly suprised. Still this does not garantee unlimited virtical especially at your elevation.

I had a TT46pro on my Ultra Stick and if I remember correctly an 11x5 prop seemed to be the sweet spot for me.
While the plane flew well enough, it really didn't have much vertical ability, and I do understand your desire for it to be able to fly straight up for at least a little while.
Wifey bought me an OS 70 for b-day or Christmas (can't remember which) and it really brought the plane to life.
Someone else already mentioned switching fuel, I used to run 10% fuel, got a good deal on a case of 15%, I didn't expect any noticable performance differences, boy was I ever surprised.
Switching fuel is well worth trying to see if the extra nitro will get you where you want to be.

Like chashint I love the 11x5, much better than the 12.25x3.75, you get better throttle response.

That's because they did need tuning! Yes, you will get more top end power with higher nitro, but any time you change fuel, you need to retune your needle valves to get the best performance from the fuel you're using. If your engine is tuned to burn the 10% fuel, and you change to 15%, it won't run right until you retune, either.

Phil

Sorry this is kind of off topic, and correct me if I'm wrong here, But Nitro is just an accelerant and the real fuel is methanol. While there is a power loss, it doesn't even need the nitro to run. In fact I think I heard that most fuels available in europe don't even contain nitro.

Agreed, I add a li'l 10 % to my FAI for my Moki 1.8 to help out w/ the idle mix.

thanx for all the advice guys!went and buy myself 15% heli fuel today and a 11*6 APC.while tuning the engine again I could feel it has more power,especially if I held it vertical!it always just rest lightly in my hands, but now it wants to go up!just have three more questions;
1.I did tune the high speed needle valve,must i tune the low speed as well?(from idle to full throttle was just as good as always,no hesitation or blubbering, it just ran!)
2. is 15% heli fuel fine?(the shop doesn't have any 15% airplane fuel, but the ingredients and stuff are precisely the same.)
3.after i was done and the engine cooled off, i'm always in the habit of swinging the prop with my hand to feel the compression, it made less than the usual nice "thud" sound almost as if the compression is a bit less.is that possible or just my imagination?must I worry about it?

About the only use I have for the APC APC 12.25x3.75 is when hovering.
For all other phases of flight I have found the APC 11.5x6 to be a better choice for my SSE equipped with an OS46SF.

/Red B.

Hi!
Been flying for 30 years ...and never noticed any reall difference in using 10% or 15% nitroat least when you fly at sea level.
Did you really set the high speed needle when you switched over to 10% nitro???
Props make difference though!

1. If it's not broken, don't fix it. If it idles and transitions well, leave it alone.
2. As long as it has the amount of oil you like (and the type you like) the "heli" or "plane" label is just decoration
3. I can't answer

#3, yes, you did feel less compression because the engine was warm which means the cylinder sleeve expanded and left the piston effectively smaller in the hole. Totally normal. When your engine is realy worn out it will have so little compression when hot that it won't stay running...then it is rebuild or new engine time.