Saito 100, or OS 91FX,
Well I can't decide between the two. I mainly like to stick with two strokes however I havent' known the OS 91 to be a very good engine.
I fly allmost a mile high so much of our power is taken away up here and I wan't this plane for hovering and torque rolling.

What do you all think?

YS120FZ, SC or NC
DKjens

kris,
i have had 3 of these planes . i used a YS .91 w/ a 14x6 prop and 30% fuel. plenty of power w/ out affecting the wing loading by going bigger. you'll find the plane is great for learnig to hover, very easy. doesn't always want to start the torque roll but it's easy wants it gets going,
hope this helps,
steve

put OS 108 with apc 16x4 or apc 15x6
perfect combination

I had a saito 91 on mine, and it just wasn't enough. It would fly great, but long vertical up lines, it would stall out. Pulling out of a hover was real slow.

I now have a ST90 with a moosecan muffler on it, and it pulls out a lot better. Its swinging a 15x4W prop about 1000RPM faster than the Saito 91, and my ST90 isn't completely broken in yet.

when it gets warmer, I will start to realy enjoy this plane,

Wow, I've looked and looked, but still I'm riding the fence. I don't feel better about any one engine than another. I'm really wanting to stay away from ys because I'm not familiar with them at all in their pressurizing and all. I did have a saito 72 that ran alright so the saito 100 seems like a good choice because it weighs in around 20 oz. with the muffler while the OS 91 FX is 24.4 with muffler.

I don't want to start on a brand that I haven't run before so I guess it's between the Saito, the OS 91 and the 108.

Any other ideas?

Kris,

If you haven't already, look at the rather lengthy thread on the UCD. Here is a link.

http://www.rcuniverse.com/showthread...20&forumid=230

You will find lots of information and opinions about the best engine for the UCD.

Ericc

Hi

I just bought mine yesterday and a saito 120 too, I fly at 5000´above msl, and I just want unlimited vertical, I will glad
to hear from you about this combo, and any prop selection advice
Thank´s

Hey there, Kris -

OH... I know your EXACT feeling! I went back & forth forever about which engine to use. After having great success with a Saito .72 on another plane, I am a huge Saito fan. After reading all through those HUGE UCD threads and reading all the engine choices, I found a lot of satisfaction with those running the Saito 100s with either a 15x6 or 16x4W APC prop. Lots of others too, but these were the most listed.

SO! I'm putting a Satio 100 in mine, and like another fellow did, I think I'm mounting mine at 90 degrees rather than inverted. Just like everything, there were some who were and some who were not experienceing "inverted engine issues". Some readjusted, some added pumps, some added regulators. I think I'm going 90 degrees and hopefully things will be as smooth as my .72 that I run upright in another plane.

Well, that's my choice and I hope it proves to be a winner... although I do like the sound of those 120/140 rockets.

-s

Just found a video of a UCD at www.down onthedeck.com (remove the space).

Kris,

I just put a 91 FX on mine, and did some prop taching/thrust measurements.

43 degrees, very dry air.

APC 15/4 prop (not modified at all)

Stock muffler w/baffle

New OS#8 plug

Tank at the firewall (new engine to me, so I wanted to take out all variables)

Dubro final filter (large)

15% RedMax fuel.


Tached as high as 10,600, but ran best at about 9600-9900. Transition was much better than I expected.

Idle in the 1800-2000 range. Wobbled alot without the wing on, so I think it would consistently idle at 1800 in flight.

Static thrust was measured several times with a digital fish scale, and we took the average of them.

11.6 lbs at the lowest, and 12.4lbs of thrust at the highest over the course of 10 pulls at full throttle. This gave an average pull of 11.8 lbs of thrust on the plane/engine.

Throttle setting to pull 7 1/2 lbs is just under 1/2 throttle.

This is on a plane that is 7lbs 6oz. Can you say this thing is going to be a blast in the air???? Power to weight ratio is now 1.5-1 or so on a non broken in engine.


Once I get the engine tuned properly and a few tanks run thru it, I will start experimenting with it. Macs header, mousse can pipe, and a perry pump (to move the tank back to the CG again). I had an enya 80 four stroke turning an apc 14/4 prop and it would hover, and pull out, but very slowly.

Hope this helps.

Steve

Thanks for all the replies is such a short time.

stevezero, what altitude do you fly at? Those numbers would be incredible if they were at 4600'.

Smartwork. Would it be possible for you to get some thrust readings? That would be great.

I just really need all the thrust I can get up here.

Hey there, Kris -

Plane is still in assembly mode with radio equipment on the way. Engine will go on in the next few days depending on life schedule.

Really looking forward to it though!

-s

\


Cool video.................cool song...........gotta love the Sopranos!

I don't know why I never thought about putting the Sopranos themesong to a flight video.

In my UCD3D, I have a .91 FX. I used that engine for two reasons.
1) I didn't want to pay the extra money for a Saito 100 right now.(that engine would be my first choice)
2) I just don't believe all that hooey about the O.S. being a bad engine and I'm going to prove them all wrong!(wink wink)
I even mounted it inverted (after much reflection) and other than the typical initial starting problems associated with inverted two strokes, it runs STRONG!
Weather has been poor, so I haven't been able to really fly it. But It looks like a winner so far.

Thanks to the inspiration of RC_Junky's install of his .91, I decided to try to squish my 100 in sideways to help eliminate that inverted engine issue(s).

Plane's comin' along great. Radio install as soon as the flight pack arrives.

-s

Would a glow driver alleviate the inverted issues?

Kris, the YS is not all that complicated. As a matter of fact, once you see the fuel line illustration that's in the manual, it's actually pretty self explanetary. The YS already has a pump and regulator and you can mount the tank on the CG so the plane flies similar from full tank to almost empty. See below. First photo shows how you just pt a "tee" in the lines. The line on the left goes to the clunk, and the one on the right goes to the tank vent. The fuel line on the "tees" just goes down to the bottom and comes out the bottom of the cowl. (see next photo)

..........Mark

The fuel lines running down the left side of the photo are attached to the tees at the top. To fuel just pull the plugs and fill it up. On the engine side, you simply have the clunk line running into the motor, and a the vent line coming out with a small check valve in-line to simply keep the pressure in the tank and not allowing it to dissipate backward. Stay away from the fuel fillers as the add weight and will eventually leak.

The YS is the way to go IMHO. If you have any questions, just shot me a p-mail.


Also, make SURE you add right thrust to the engine. The instructions say it's built in to the firewall but mine and may others were at 0 degrees.

See below for the illustration of the fuel line set-up. Very simple. Just visualize the "tees" inplace where the fuel filters are (which I don't use.....I filter from my fuel can). Also the check valve can be anywhere on the vent line side. Before or after the "tee" doesn't matter.

Hope this helps........Mark

You go Man! I just bought one for mine too, but i will try to mount it at an angle and get the muffler in the tunnel if possible.

Just checked out a thread in the engines section, turns out the big problem with the OS 91 FX is some of the needle valves don't seal and allow air to get into the line. Easy to spot, and easy to fix. Folks were having good luck with the Cline regulator. The Ultra thrust muffler is supposed to be a hot mod too, for those who decide they want a bit more.

hopefully my UCD will arrive soon.

Sorry about the delay in replying to my earlier post. I am at about 750ft above sea level here. I picked up a macs header for mine (which is the same as the one for the os61, so I'll give building a mousse can for it in the near future. I havent been able to fly it yet (got called out of town for a week immediately after making that post.)

Will post inflight data ASAP.

Steve

I am very confused with all of these large, heavy engines being used, I have a Satio 91 w/APC 15x6 and it is a rocket. Hovers between 1/4 and 1/3 throttle and shoots out if needed be. I suppose it's the joy of being at 6lbs, 7oz.

Darrin C

DarrinC,

How in the world did yours come out at 6lbs 7oz, mines weights 7.5lbs without cowl, and wheelpants.

I orginally had a Saito91 on mine and pull out was very, slow.

m.gramling, I've got a Saito 1.80 in mine w/ cowling and pants and weight is 7lbs/ 4oz. I made some slight mods, but nothing too drastic. and that's w/ 1.75oz's in the tail. Could wood quality actually make such a significant differance in weight?