Hi Folks
Does any one have any experience of using an 91FX in a pattern plane.
I got an MK SKYSTAR 90 for my xmas from the girlfriend and I was hoping to put my OS into it.
The bug bears being I will need to run the beast with a pump and probably on a tuned pipe.
Does anyone have an experience ( good or bad) of using this beast in this manner.

I guess most of you are wondering why I am not dropping a YS engine into the plane well the answer is simple 30% nitro is not cheap over here in the UK and I have the OS sitting doing nothing anyway.
But MK kits are alot more reasonably priced over here.
Thats life I guess.

Any help would be gratefully accepted

Mike

Some guys are having trouble with them, but some other guys are having a great time with them. OS were supposed to bring out a new O ring or something, but I don't know if it made a difference. I think though, that if you know how to run in an engine properly, then it'll run goooood. Compared to the YS, here it is in short. The OS has more power, but worse throttle response. I will be putting one in my Widebody 60 in a couple of months time.

Robert
Thanks for the reply.
Do you intend to use your OS with a tuned pipe?

I might put one of these on to increase performance, and to better the throttle. I also plan to put a pump, although I don't know which.


http://www.westonuk.co.uk/aero.html

Robert
I was planning on a perry pump and maybe the matching carb.
As for a suitable tuned pipe I have no idea. I was going to get Just engines of the uk to make me up a swan neck manifold to keep everything clean.
An alernative would be the cline regulator but i have no experience of this animal.

Mike

My Goldberg extra used a OS 91 Fx on 15% fuel and no pipe-BCM pitts muffler. it had great preformance with a 15X6 and the plane wieghed 8.5 pounds. I plan on the same set up with my Widebody 60, but maybe the stock muffler instead of the pitts.

I used the OS91 in a Dick Hanson Elite with good success (about an 8 lb plane), using 10 and 15% nitro. I used an APC 14-10 prop and standard muffler. Made for a nice, no messing around, light set up. I never had it noise checked, so don't know if it would pass, but it was fairly quiet. I then came into a used YS91 cheap which I retrofitted and promptly trashed a tru turn spinner when it back fired! The YS throttled better, but I had to use 25% nitro to get the same kind of power (same prop size).

Jeff, Do you have any RPM measurements for the OS91 on that APC 14x10? Just want to know how it compares against my old Super Tigre 90 before it bit the dust. I was using a pipe so that's probably worth 3-400 revs. On a good day it would turn a 14x10 at 9,400-9,500RPM on 10% fuel. Trouble was, not all days were good!!

Mike, I would try to get hold of an OS Hanno pump and check if it fits (no better pump ever made IMHO). Failing that, try a Cline regulator. The pipe from the Cline to the carb needs to be short (3/4") to work well but with the OS being a rear mounted needle, that shouldn't be difficult. Allow enough room behind the engine for the regulator & plumbing and don't hard mount the reg. as it doesn't like vibration.

Alan.

Mine (on a Calypso) does 10200 with a APC13/10 15% nitro. With a ultrathrust muffler it does 10800. That's adjusted for flight. With a Master 13/8 3 blade it does 10400 and 11400.

No, I've sold the plane and engine last summer. I remember it turned higher than the YS91, but not by a lot. The Ys is one strong 90! too bad it weighs as much as a 1.20
Jeff

Hi Mike,
First, I'm jealous that you have a Skystar 90 already. Second, that they are cheaper over there - how much are they (in US dollars? maybe your local hobby shop would consider shipping here )
I have a G-Trick which first flew with an OS 91FX. I modified a wrap-around header made for the ST2300 (I just drilled and tapped one new hole). THe plane flew well and the engine ran great - very user friendly. However, curiosity got the better of me and I put one of my Hanno specials in it. I hate to say it, but the Hanno has more power. Enough to be noticable, but you can still fly all the maneuvers (I've flown all the FAI sequences) with either engine. I ran my 91 just with pipe pressure (no pump) and the tank close - it was very reliable. You might try the Hatori wrap around header made for the OS 1.60FX (I think you wil still need to drill and tap another hole). I run 10% nitro and my G-Trick weighs around 8.5lbs (3.8 kilos).
If you keep the weight at 8lbs (3.5kilos) or less it should fly great on any engine. By the way, does the kit include the fixed gear or did you have to purchase it separately?
Happy building!!!
-Will B

Hi Willy
Thanks for the info.
To answer your questions the fixed gear comes seperate to the kit but you have all the bits( woodwork) to make it retract or fixed capable.
I intend to put the wood work in for both so I have the option.
Second I live in the frozen north of Scotland ( Thurso is the Uk most northly town) If you are looking on a map, Scotland is sort of flat on top I live about third of the way along that flat bit measured form the right hand corner.
I get all my pattern stuff mail order through Probuild UK. ( they have a web site and as far as I know they will ship anywhere in the world). It cost £250ish shipped to my home.

I am planning in trying the FX without a tuned pipe but due to the tank location I will be running it with some kind of pump or regualtor and see how it goes. The plans quote 7.5 to 8 Lbs but i am guessing that is with a YS91 so i am hoping to get a good bit under that.
As it is being built as a bit of fun I will be happy if it is not quite completely ballastic. (Saturn 5 will be fine I am not quite aiming for the Shuttle).
I will let everyone know how it turn out .

Mike