I'm wanting to learn sportsman pattern and i have an older os 40 if i remember right its a fs model.i'm looking into the tower hobbies kaos 40 and i'm wondering if that would be a good set up for my motor? Later on i would like to build either a dirty birdy or a phoenix 7. So i figured this setup would give me plenty of practice considering the landing gear is the same. Another thing what prop should i try with this plane?
Thanks

FD,

The OS 40FS is a four stroke engine and won't have enough power for the Kaos 40. The 40 specified refers to a 2-stroke engine. If your engine is an OS 40SF (subtle difference), that engine will be fine.

The typical prop used on 2-stroke 40's is a 10x6. The SF might also be happy with a 10x7 but I'd stick to the 6" pitch.

David

its a 2 stroke so it must be the sf
thanks

Fly Dat,
David is right FS series are 4-stroke engines and yours must be a SF which is the side exhaust modification of the RF- rear exhaust - engines. you can see one of the first generations of the FS series in the image below.


but maybe your engine is a FS R which is an old famous 2-stroke engine. the image below refers to FS R series. and a 10X6 or 10X7 will be a good choice for your engine. I have used both of them on my old FX .40 with no problem.


In the chart below there are some options for 40 FX but I suggest to chose the proper propeller based on its performance an the engine output during flight.
another proper power choice will be the .46 FX or AX.


Ehsan

Ehsan,

I suspect you are right - the engine is probably an FSR. Using another more modern OS engine, the FX would do nicely but my feeling is the AX series are designed for slightly larger props at lower rpm. I believe the 46 AX might be happier with an 11x6.

As a minor aside and to avoid confusion, there was no 40/46 RF (rear exhaust). The RE counterpart if the 40/46 FSR was the 40/46 VF but the 40/46 SF had no RE counterparts with the VF series probably still in production.

Whatever the engine in question, if it is an FSR, SF or FX, they will all serve well. Even the RE VF could be made to work with a tuned pipe either side mounted or with pipe over the fuse vertically mounted.

David

David,

I do agree with you about AX. based on my experience on a great planes Easy sport MK 2 the AX engines will provide slightly more power than FX series, after it crashed I changed the .46 Fx with a FX.
Though the repair procedure made my plane heavier but it flew even more powerful.
and about the RF and SF engines I think I was in a big mistake till now.
Thank you for sharing your knowledge.

Ehsan