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Old 11-14-2013, 06:48 PM
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Part of your answer to comparing 7.5 lb models is the UCanDo is pretty draggy from what I remember. The Extra should have a sleeker cowl area and a smaller airfoil, right?

Last edited by blw; 11-14-2013 at 06:51 PM.
Old 11-14-2013, 07:14 PM
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I may have erred, I thought HS was talking about a Cub, I see that its an Extra 330, might need a 1.00 or a 1.25 as Pete suggested for that.
Old 11-14-2013, 08:09 PM
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Originally Posted by hsukaria
I need help deciding between a Saito FA-82 and FA-91. I have a 60-size sport plane, a Phoenix Extra 330S that has been using a 74 and a 90 2-stroke glow engines. But now I would like to switch it to 4-stroke. The plane weighs about 7.5 lbs. I would like to get unilimited vertical so that I can do some 3D flying also. Would the 82 be enough, or should I get a 91? I already have an FA-82 on a 7.5 lbs Great Planes UCD46 and it gives unlimited performance. Weight or space are not an issue with the Extra 60.
I would think that the UCD46 weighs less than the Extra 330s is my first thought. My second thought is that ALL of my 80 class 4s are outclassed by my 91's. *I* would get the 91. I have to be honest and admit that I have not run an 82 so my comparison may be slightly whacked.
Old 11-14-2013, 09:03 PM
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I used to have a Phoenix Extra 330 with a Fa-125a on it. No issues to balance the model. It flew great. I got correct CG with the battery mounted just behind the servos.

Last edited by AeroFinn; 11-14-2013 at 09:08 PM.
Old 11-15-2013, 05:37 AM
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thanks guys. The Phoenix Extra does have thinner airfoil than the UCD. It also has a vast range for placing the battery pack. I was also trying to get more static torque rather than top-end power. It flies fast enough at half-throttle, but can't do much with instant torque response with the 2-stroke like I can get with a 4-stroke.

Last edited by hsukaria; 11-15-2013 at 05:40 AM.
Old 11-15-2013, 05:55 AM
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Speaking of a Saito 82AAC. I am investigating that engine for a scale project. I have a Dave Platt Waco Bipe kit in 1/6 (60" span). The engine bearers were designed for a 45 to 60 two stroke. I have read where people were happy with an old 72 four stroke for scale flying and it was also flown with a 90FS. I have read where the the newly designed crankcase in the 72 replaced a 60 and the 82 is the same size as the 72? If that is the case it seems like the 82 would be the way to go. Does this seem correct? The plane itself tended to be a floater, especially on landings. Thanks.
Old 11-15-2013, 06:03 AM
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Skypup,
The Saito 50, 56, 72 and 82 all share the same mounting bolt pattern, but not necessarily the same case width at the beams. The 82 would turn a larger prop (14" easily) and, IMHO, be a fine choice.
Regards,
Jim
Old 11-15-2013, 06:05 AM
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Thanks Jim. Greatly appreciated!
Old 11-15-2013, 06:32 AM
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I am still amazed at the performance of the FA-82. It spanks the OS, TT, and Magnum 4-strokes of similar size.
Old 11-15-2013, 07:16 AM
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Originally Posted by hsukaria
I am still amazed at the performance of the FA-82. It spanks the OS, TT, and Magnum 4-strokes of similar size.
That's great to know. It won't quite fit under the cowl from what I can determine at a quick glance.
Old 11-15-2013, 07:27 AM
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Originally Posted by skypup50
That's great to know. It won't quite fit under the cowl from what I can determine at a quick glance.
The TT75 is shorter stroke than the Saito, OS, and Magnums/ASP., but larger bore. So, the TT75 might fit under your cowl. Check the dimensions.
Old 11-15-2013, 08:41 AM
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Originally Posted by hsukaria
The TT75 is shorter stroke than the Saito, OS, and Magnums/ASP., but larger bore. So, the TT75 might fit under your cowl. Check the dimensions.
From the lugs to the cylinder top the TT is 83mm vs 111mm. Good call. Thanks.
Old 11-15-2013, 08:50 AM
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Originally Posted by skypup50
From the lugs to the cylinder top the TT is 83mm vs 111mm. Good call. Thanks.
Glad to help.
Old 11-15-2013, 11:08 AM
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Ok, I decided and bought the Saito FA-91 from a local guy. I have it in my hand as we speak. No time to waste!! It is brand new but the previous owner lost the muffler. I am debating whether to buy a stock muffler and header or go for the Turboheader muffler. I won't need the Turboheader adapter for this application.

What would be a good prop for this engine on a sport/pattern/3D plane? 14x8? 15x6?

Last edited by hsukaria; 11-15-2013 at 11:48 AM.
Old 11-15-2013, 12:22 PM
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http://sceptreflight.net/Model%20Eng...%20FA-91S.html

HS, you can find most of the skinny on the .91S right here, I keep that site as one of My Favorites.
Old 11-15-2013, 01:07 PM
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thanks Hobbsy, I read the whole article.
I will try 14x8 and 15x6 props. I will look around for the procedure to break-in the engine. I probably will run the first few tankfuls with 5% nitro and synth. 18% and 2% castor. Later when on the plane, I will run 20/20 nitro/all synthetic oil.
Old 11-15-2013, 01:27 PM
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I generally run an engine with the fuel it will be fed for the rest of its operationing life. With the new Saitos they are very specific in the literature we get here in OZ to run only synthetic and 20% oil content by volume. Our comp CD's who supply fuel for some of the O/Timer events are slowly learning to supply the correct fuels.
Old 11-15-2013, 01:44 PM
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Originally Posted by FNQFLYER
I generally run an engine with the fuel it will be fed for the rest of its operationing life. With the new Saitos they are very specific in the literature we get here in OZ to run only synthetic and 20% oil content by volume. Our comp CD's who supply fuel for some of the O/Timer events are slowly learning to supply the correct fuels.
Well then, I have plenty of 20/20 all synthetic. Will run-in with that too.

I have to say it, this FA-91 looks voluptuous!!!
Old 11-15-2013, 03:29 PM
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HS, I'm sure you've seen my little break in program, on here, I'll gladly re-post it if needed.
Old 11-15-2013, 03:31 PM
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Break it in by the book. Set the needles by the book and run it on a test stand below 4000 the first 10 minutes just as sloppy rich as the manual states. Run the next tank around 5000-5500 for 10 minutes. 6000-6500 for the next tank, and 7000 on the last. While saying I run it at 5000, I also cycle it slower and faster at times. Ditto for the other 2 tankfulls. I think that's close to what Hobbsy suggests. Also, I begin short wide open runs on the second tank. Longer WOT runs as it builds up time. I probably run mine harder than most do when breaking in. You should see the point where it suddenly smooths out. Begin leaning the high and low speed needles and set them for flying after the 40 minute runs and when installed on the model. I think Hobbsy sets his needles just right on the second tank. I usually do too, or kinda close depending on how the engine runs. I use Omega 15% with a couple of oz castor added.

i recently broke in an 82 and it sounded as as smooth as a well broken in Saito on the second tank. On the other hand, my 125 sounded rough and vibrated a lot until the 4th tank. Each engine will act it's own way.
Old 11-15-2013, 03:55 PM
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Barry, many times during the second 10 minute period at 5,000 rpm, the engine will slowly accelerate to about 5,300 to 5,500, just from limbering up or the ring sealing better, who knows. As you said, its obvious when it smooths out.
Old 11-15-2013, 04:50 PM
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Thanks for the help guys. I will go back and check your break-in. This Saito 91 will actually be my first new Saito. The previous 2 Saitos I bought used.
Old 11-15-2013, 08:06 PM
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Originally Posted by Hobbsy
Barry, many times during the second 10 minute period at 5,000 rpm, the engine will slowly accelerate to about 5,300 to 5,500, just from limbering up or the ring sealing better, who knows. As you said, its obvious when it smooths out.
Fuel economy suddenly gets much better when it smooths out like that.
Old 11-16-2013, 04:20 AM
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(quote), comp CD's who supply fuel for some of the O/Timer events are slowly learning to supply the correct fuels.

Are they actually supplying the correct fuel or just the one they think is correct?
Old 11-16-2013, 02:45 PM
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Hobbsy, Our Cd's are stuck in a time warp. One of those "we've done this for the last 100year things". The arguments are many fold, like castor has not hurt my 20 year old engine so it won't hurt these new things to why are you worrying it is only 20 mls.(multiply that by a factor of 5 for the rounds flown). I won an argument on this one day when I refused "supplied fuel" took the penalty and watched my main competitors YS clog up under castor over load. What we now generally have is a castor based fuel, a caster/synthetic fuel and a synthetic fuel available for the Texaco event which keeps us all happy most of the time.

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