Hello all,
I'm building my new pattern plane, it will be equipped with a new OS 140RX. I'm thinking about propellers: I see most people suggest APC 17x12 (N? why?), while others love 15.5x12 4 blades for its breaking effect. Actually, I'm very interested in breaking on downlines, since my plane is a bit old, not like those new planes with thick airfoils and fuselages...

So the 15.5x12 is the best choice? What do you use and what amount of nitro? It is ok this 4 blade with 10% nitro? Its is not too much for that engine? And the 17x12?

Thank you all for the replies.

In the Northeast US and scattered around the US in other locations, a number of people including myself are using an APC 15.75X13 3-blade prop repitched by Dave Lockhart to 15.75X10 on the OS 1.40 RX. Most use one brand or another of 15% nitro fuel. I also use the 15.75X13 repitched to 15.75X11 on a Webra 1.60. These props are great, even if your idle is a little on the high side it will break in the downlines nicely.

Hi Joe,
how is it possible to repitch a propeller??? Are they for sale?

Thank you!

As far as 2 blade props go I have seen people use the 16.5x12W, 17x12N and the 17x10 (full blade). My two blade of choice is the 17x10. I like it's speed and pulling ability. In the 4 blade area I like the 15x11 better than the 15.5x12. I find that the 15x11 gives me quicker acceleration out of snaps and better up line performance while maintaining that excellent 4 blade down line braking.

Jon Carter

I support what others have said:
APC 17x10 or 17x12n 2-blade
APC 16x10 3-blade (repitched)
Bolly 17.5x12 2-blade

I have tried the 15.25x12 4-blade and it was too much load and too slow transition for my taste, the 15x11 4-blade would be a better solution.

I am currently using an APC 17x10 (good acceleration after the upline snap), but also really like the APC 16x10 3-blade for slower downline and horizontal flight.

I've been using the apc 15.5 X 12 4 blade for a couple of years on a jupiter using a bolly muffler. It's a very light plane and the 4blade really smooths out the power. I used the 17-10 on my Focus (again on the muffler) with good results. The 17-10 on the jupiter has noticeable improvement in thrust, but it also makes the plane "jumpy" on throttle application.

Dave Lockhart charges $25 to repitch them which is cheap considering the time he puts into it. He uses a Prather pitch gage, heat gun and whatever tools he uses to twist the blade at a particular spot on the blade. I don't know if he is taking any International orders but I guess you could contact him and ask. His e-mail address is: [email protected]

Hi there
As always it depends. In this case of your model, your flying style etc. What's also influencing is wether your airfield is noise-sensitive or not. For several years the APC 17x13 was my favourite, now I find the APC 18x10 to be best. I have also used the 18x12, but it's a little bit on the heavy side (for the engine). The N (narrow) 17" is not any good in my opinion, neiher is the 18x10PN (more noise and less performance than the normal 18x10). The 16.5" series is narrow bladed and not particulary good. Maybe the new 17x12W is a good one, I have not tried. From my humble experience with the engine (from '98), I can not understad how anybody can pass the 94db noise limit with a 17x10.
As you can see, the engine is very flexible and can do well with a lot of different props. For a good balance between power and noise, keep the static RPM between 7300 and 8000.
Best luck
Ola

Thank you guys! Ola, contratulations for your flights at WC, I was there!!!

From the various replies it seems this engine has huge flexibility!!! I din't think that it could spin a 18" propeller!!!

I see that in local contests here in Italy the APC 16x14 is also quite used: it could yeld little more speed vs little less vertical thrust?

Everybody agrees about 15% nitro?

Thanks again for your help, very appreciated.

17X12 APC regular 17x13 APC on calm days
18x10 PN APc
15.75x10 or 11 3 blade(Lockhart)
15% nitro
OS or YS 4 stroke plug
Adjusting pipe length will generally get any of these props in the 8-8300 rpm range.

About 16-17lbs of static thrust with these props. speeds vary between the props.

Wayne Galligan

Thank you Wayne!

Since I'm new to piped engines, what is the criteria used to adjust pipe length? I should only check maximum rpms and try to be around 8000? What are the effects of lengthening the pipe?

I have tried the 18x12 and it's too much for the motor. I ran a 17x13 and it was my favorite until..................

15.5x12 4 blade. What great downline speed now. I have so much time in between manuevers. I'm running mine with a greve's pipe which give's it a little extra ummmpppphhh. I am going to try a 15x11 4 blade this weekend as I just got one to try from Central. I'm running magnum 1 fuel. I'll tach it with both blades this weekend. I love this motor, pipe, 4 blade combo.

Chris

I haven´t try with 3 or 4 blades, now I am using 16.5 x 12 W 2 blade with the standar set-up, hatori - OS pipe and header, burning 10% nitro and runnig great, 1600 -1700 idle and 7800 WOT. flying 3000 feet over the sea level.

Chris, have you tried the 15x11 4 blades? How was it like? Uplines velocity? Whay kind of airplane are you using?

I didn't put it on as I was having a great practice session on Sunday with no wind. I'll try it after the contest this weekend and post results if I get a chance. I know plenty of others running the 15x11 and they like it. Great downline and upline speed.
Chris.

Thank you Chris, I'll wait for your impressions. Good luck for the contest!

Hi Guys,
I have experience with the OS140Fi and 160FI. The difference is around +100rpm for the OS160FI.
My set up is a ES composite "2C160S90" exhaust, Hyde type engine mount and 10% Cool Power.
I dont try to get the best power on the ground (shortest exhaust set up) but lets say 100/200rpm lower (around +1 inch)
I like the APC 17/12W around 7800rpm (17/12 is too light for my taste), its really soft in the air with good vertical power and average breaking in the downlines, easy speed management.
I flew the APC 18/10 WNP (7900/8000rpm) at the WC (only on the OS160FI, I crashed the plane with the OS140FI :-( ). Great vertical up and down lines, good throttle management is required.
I tried the normal 18/10, too light with 8300rpm.
About the 15.5/12 4 blades. Good down lines but not easy to go out of the vertical snap.
The Engel modell silence 18/11 carbon prop is too light as well (8300 rpm)

Hope it helps a bit.
2 strokes are not dead yet!

Happy loops,
Benoit

Hi stek79, i'm seb from the french forum,
you can also try 17x12,5 N with 15%nitro, it works good.

17x13 gives a little more downline braking if you go two blade. But four blade is where its at for me. Until I go electric.
chris

Chris,

have you eventually tried 15x11 4 blades?

Hi seb! How are you?

Sometimes I would like to post questions to your forum also, so to collect (perhaps different) answers from european pilots... but my french is so bad!

Anyhow, thank you for your reply.

Hi Stek,

Unfortunately, I had a very close friend pass away and haven't had a chance to. I was going to put it on this weekend at the sacramento contest, but never needed to. I was sure I would need to as it was quite windy on Saturday, but for some reason the 15.5x12 worked well. I balanced it at the field and I will put it on tonight probably as we have a contest again this next weekend.
I will post the results, I promise...
Chris

Thank you Chris, don't be in a hurry!

you can ask for it in englsih , many guys understand english

Hi Guys,
I fitted an Os 140 Rx and carbon pipe on a 2mtr Fantana (Sebastiano Design) and I tried to give the engine the running in.The engine when started didn`t want to work on the rich side and to hold stable running it is working on 3/4 opening of the needle.I made 2 flights with no ded sticks but it seams to have still a rich transmitiion.I am using fuel with 18% oil and APC 17x10.Can you help me pls.
Promlem is rich transmittion,when I lean more I am loosing the climb in the vertical.