Hi,
I just purchased second hand Zen 120 and i am thinking what engine to use. since i don't want to use 2 cycle nitro engine or YS, i have left with the following options :

OS-155 4 cycle , SAP-180 Gas, DLE-30 ( i want only engines with build in pump )

any advice ?

There's four that fly in our local competitions. All are using 1.40 RX os motors.

I'd be looking for something of that kind of power.

i am not going to compete, but still want to be able to perform advance sequences.

Ruling out 2C nitro (and nitro in general IMHO because of the exorbitant cost of glow fuel), for this size model you will find the SAP 180 has plenty of oomph with its standard Pitts exhaust, and being rear induction/rear exhaust it will all fit under the cowl. Maybe need to cut away some of the motor box to make room for the carb, but this is not difficult.

I am flying this engine on a 2-meter Focus II with an ES pipe. While it has plenty of power, it does not have the midrange grunt that is the Holy Grail for pattern power plants. So it must spool up quite high (9200 rpm with an APC 16x12 or 15.5x12W) to match up powerwise with the midrange beasties in vertical elements, which there are a lot of in pattern. This makes it a bit noisy, even on a pipe.

Recently I assembled a Sickle electric 2-meter (from F3A Unlimited) with a good power set-up and I can see why so many pattern guys are going electric. Hard to beat a modern design with electric power. Pretty much pattern Nirvana.

I got SAP-180 from some friend on our field so i will be able to test it. the engine include the standard muffler
do you think 16x10 regular APC prop will be ok ?

Thanks

30cc is the way to go if you don't want to go electric.

Been running in my TWM SPot on with DLE20 in the nose. Plenty of vertical poke in a plane weighing under 4kg.
With a 30cc in the ZEN, it will go straight up till it runs out of atmosphere.

I used to fly my Zen120 with the YS120AC and Hattori muffler with 15x10 APC, excellent combination.

Regards

Alejandro P.

Hi Alejandro
What was your Zen total weight including fuel ?

Not quite enough prop. 17x10 or 16x12 will work fine.

Does the muffler have the "tone inserts"? They restrict the power a little, but really reduce noise. Even with a little power restriction you will still have plenty of power.

In order to reduce the weight of the model, you can use the [link=http://www.tech-aero.net/ultra-ibec]Ultra IBEC[/link] to power the ignition. It uses power from the Rx battery, so you will want a larger Rx battery such as a (regulated) 2600mAh Li-Ion or LiPo battery of the 2-cell variety.

Thanks
At the time my friend bought it without the tones ( i will probaby order it soon ) i have the Ultra IBEC.
at the beggining i am going to use dual nicd batteries and swithces ( this is the setup that i have used on my other airplanes )
i thought that the 16x12 works fine only on tuned pipe, what is the ground rpm i should get ? do you think i will get the upper of 8K ?

You are correct... I am thinking about my piped set-up! Mine turns the 16x12 or 15.5x12W at 9200 rpm static.

So the 16x10 is okay for the Pitts muffler with the inserts, maybe try the 17x10 after a little break-in. I can only guess at the rpm, but perhaps 8200-8500???

How much do you anticipate the flying weight will be? If around 9 lbs - or anything less than 10 lbs - you won't be lacking for power.

Looking forward to some photos and video. Should be a great performer.

the total weight including fuel will be ~ 11 lbs

Hello Selnekav,

Sorry, but honestly I don't remember the weight as I only weighed the airplane once.

Best regards

Alejandro P.

The weight sounds a little high for a 71-inch wingspan model, but it will fly fine if that is the "ramp weight".

With the extra wing loading, it should fly very well in windy conditions!

it's second hand airplane, originally it flew with webra bully 120 so i guess the weight was 10lb but since i am going to put the SAP-180 and also my dual battery NICD packs it will be 11lb. i am F3A sport flier and my only concern is first time to have real unlimited vertical ability. after 27 years in the hobby i puting my hopes on the SAP.... i guess 1lb should have no real problem to achive my goal....

I am thinking the weight might be less than anticipated.

With two 1100-mAh NiCd's and the IBEC you will be able to do 7-8 full flights with a good safety margin. Power consumption will be approximately 150-200 mAh per flight for both servos and ignition.

This makes it easier since you won't have to use a voltage regulator for the Rx.

Also, you will need only a 11 or 12 oz fuel tank, and you could get away with a much smaller tank if you limit it to 8-minute flights.

A lot of guys are flying this engine in 3D models such as the Extreme Flight Extra, 78-inch wingspan, and some other 3D models. some weighing over 12 lbs. However, they are using a Vess prop, either an 18x6 or a special 18.5x15.5 version, both developing more than 20 lbs of thrust. Noisy as hell but pulls like a beast.

Thanks Bob
I wil take your advices.