Hi.
Just finished a Protech Onyx 140 with Saito 180, currently running a Graupner 16x8 prop, what do you guys think as regards other prop options.

Cheers

hi
i think 16/8 is small for a saito 180, we use this prop on YS 120, try an 15/12W , 16/11-12 or 17/12N.
Post some pics of your Onyx.
Regards Mirco

Hi Mirco.
Here are a couple of pics of Onyx (I hope), I know the purists will disapprove, but I can't stand inverted motors.
Cheers.

I like it with the engine hanging out. And, if there is an engine problem, it's more practical as well.

Sam

Definitely a bit small, that would be more suitable for the 150. If the 180 responds like my 150 did, aim for about 9k rpm, it seems to be more reliable there than at lower rpm. The prop you will need to use depends on the nitro levels you are using and where you are, I would try something like a 16x10 or 17x8, I suspect some of the props mentioned above will be a bit heavy for the engine even with 30% fuel.

Good luck with it. BTW, what engine mount have you used and how much airframe vibration have you got? You will notice my recent post about problems with vibration in an Onyx...

James

Hi James.
The vibration isn't too bad, about the same as my pals Swallow EX / YS110 set up, have used the standard glass T mount however, I have strengthened the motor mount box on the plane significantly, in stock form it just did not seem stout enough to take the punishment of a 30cc four stroke. Still a bit unsure about props, the 16x8 is giving 9500rpm, which according to thrusthp is 3.2hp for 17.5lbs static and 73mph, the model weighs in at 10.6lbs all up dry, the thing that confuses me, is a prop such as a 16x12 would pull the rpm down so much, the motor would not be making anywhere near it's optimum power, so why are they used?
Cheers Martin.

dear d-i-c-k-h-e-a-d, where do i begin??? saito, beautiful engine for a sopwith pup. YS or OS.. there is no other option.

yer my great planes cub is the s-h-i-t with a side mounted saito 180 tork rolls all day long...
peace out

f-u-c-k man look at that b-i-t-c-h under your name, i recon she would have big enough flaps to slow down the awsome power of a fully nitroed up saito with fames out the exaust.

dont forget the blow off valve...your not fully sick without a blow off valve..............

peace

ill pop my vale on her clam

Acrobat.
Most eloquently put, wish I had your command of the language........ Unfortunately you don't explain why.

hi Futaba
this is my Onyx with a little modified engine mount in order to use YS soft mount.
Regards Mirco

I suggest trying an APC 17x8N with the Saito-180
The rpm will be a bit less than the 16x8 but I think you will get more thrust moving vertically.
I am using the APC 17x8N on both Saito 150's and Saito 180, in a pattern model and
Goldberg Extra that each weigh about 10.5 lbs similar to your model.

If you want to put the tank back near the center of gravity you can use a
Perry pressure pump as shown on my web site.
http://saito-engines.info/pumps.html
There are other pump options but I like the Perry pressure pump best.

You need the prop which will put the engine at the speed it likes to turn. For the Saito 150 (and I would guess the 180 would be the same) this is about 9k. For a YS 140 for example (and this is not the start of at YS v. the world comment...) they like low to mid 8k's, hence a bigger prop turning more slowly.

The YS 140, especially the dingo, is also more powerful than the saito 180, again another reason for a bigger prop.

It will probably be ok with a 16x8 but you would almost certainly get more thrust, as well as less noise, from the 17x8 prop mentioned above. For the bigger engines and especially four strokes, bhp is a rather misleading way of comparing set-ups. It comes down more to torque, so just because you put a larger prop turning more slowly you can get better performance despite being lower on the bhp curve.

James