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Author Topic: Saito 56/TopFilte Score  (Read 2016 times)
Dan McEntee
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« on: July 19, 2009, 11:43:51 PM »

    I have a new to me TopFlite Score with a like new Saito 56 installed in it. This is a former Crist Rigotti model that he sold a year ago or so that I missed out on, but recently purchased it from Leester who bought it from Crist. The model weighs 65 ounces and came with a Bolley 13/6 prop (which I have since ruined, a story not worth telling really), carbon fibre landing gear and Tom Morris controls. It looks like a really nice airplane with some good potential, I just have to learn four strokes.
    Two years ago, while at the SIG contest, Keith Sandburg MADE me try his Legacy with a Saito 56 in it. He had the R/C carb on, set at about 3/4 throttle, and I think he had a Rev-Up 12/5 on it. HE fired it up, and boy what a sweet flying model. He said that once I tried four strokes, I would give up everything else! I don't know about that, but I was sure I wanted to duplicate what he had! Saito had just come out with the .62 a little while after that, so I bought one of those, but didn't have a model to put it in yet. I missed out on Crist's model the first time he had it for sale, but fate was kind to me and now it's mine!
   The engine has the UHP venturi set up, and the Hoffman wedge style tank with 4 1/4 ounce capacity and I have line length of 68' from handle to model centerline. I flew it for the first time today, and the model does have a lot of promise, but like I said, just have to figure out these beasts now! I flew it with a Zinger Pro 13/6. Seemed like a lot of prop but  I have been following the four stroke posts and know that they "like" a lot of prop load. I had no idea where to set the engine. These things REALLY are different, and by my tach and my ear, I thought I had it about right, and I had a 4.6 lap time race horse!! The engine run time was in the 8 minute range, so that at least mad me feel that the tank was big enough. I refueled (PowerMaster YS-20/20) and set the RPM at about 8000 RPM for this flight. The lap time was still a bit fast at 5 seconds, but at least I could try a few maneuvers and see how the model handled. The engine slowed a bit inverted, but not to any detriment, and the model has a pretty good corner. I did like the line tension everywhere I had, and can really see some potential. Then the engine ran out of fuel after only about 5 minutes of running. My concern is finding the right RPM and fuel consumption to avoid over runs or possibly loosing the model by having the engine quit at the wrong time!Trimming will be easy once I figure the engine out. I do have a few questions for you 4-stroke guys:
      1) How critical is tank location as far as high and low? do I raise and lower the tank the same as for my ST.51's or any other s-stroke?
      2) Can I go down to a 12/6 Zinger Pro, increase the RPM some again to slow the lap times down a bit more and help me get through the pattern on 4 1/4 ounces of fuel?
      4) This is for Bob Reeves: I've searched out some of your posts on these engines and your method of using a nylon bolt to adjust the choke area of the venturi. In this model, the venturi angles back toward the firewall slightly, so installing one like I saw illustrated in one of your posts might not be practical. Can a smaller one be threaded into the side of the venturi to achieve the same desired affect? What size venturi would you recommend for this size and weight model?
       5) I live in the St. Louis area at around 400 feet above sea level. What would the the suggested take off RPM with the set up I currently have installed in  airplane?
   I may or may not fly this model in competition. My main purpose for it is to use it as a mule to learn the natures of this beast, break in the .62 I have in the box, then build a new model for it later on. I do like what I have seen so far, even only the two or three flights I have on it. Thanks in advance for any and all help.
    Type at you later,
     Dan McEntee
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« Reply #1 on: July 20, 2009, 06:06:23 AM »

Hi Dan,

Sorry about your Bolly 13-6 but as far as the Saito 56 it's not a great loss. I had read that some were having good luck with that prop on the Saito so when I first put my Score/56 in the air that was the prop I used. I also had a UHP venturi using (I think) the middle insert. It wasn't too bad until one day I took it up in a 12 MPH breeze. That thing was doing about 9000 MPH at the bottom of the vertical eight, almost re-kitted it.

Prior to this I had played with a Saito 40 enough to find what worked for me which was the high pitch choked down venturi setup I've been talking up. Applying this to the 56 worked and I ended up with the setup you probably found. Rev-Up 13-7 and the choke screw. I have since had it beaten into my head by the Dallas gang and further experiments have proven that it isn't so much pitch but prop load that makes these things work. They like to be loaded, 7 pitch worked great on my Score but not so well on my new ship. I believe the new ship is much slicker (less drag) and that made the difference. I'm now running a 3 blade CF 13-5.5 launching at 83-8400 and so far so good..

BTW: I've had both a 56 and a 62 in the new ship and I really don't see much difference between the two engines. The 62 might turn a little more prop if the airframe needs it but in this case running the same prop at the same RPM the airplane didn't care which one was in the nose. I'm confident either engine is more than enough for anything around 680 sq/in and 68 oz with a Genisis or Legacy airfoil. See what happens, get me talking about Saito's and I just don't shut up.

Anyway, I still believe the variable choke is almost a must have as it allows adjusting the engine to the prop/airframe rather than trying to find a prop that works with a fixed intake. You can run a 1/4-20 nylon screw down the throat of the UHP just like I did on the Score. It will go in at an angle but works the same. You can also run a 10-32 into the side just have to weigh the options and try to come up with something that's fairly easy to adjust with the engine running.

When you say you set the RPM at 8000 with Zinger, did you simply richen the needle to lower the RPM? If so that isn't really the way to get there.. Keep the Zinger (for now) and add some means to reduce the choke area. Keep (and re-adjust as needed) the needle set just to the rich side of peak. Start choking the engine down a little at a time, you will hear the rpm drop, re-adjust the needle and it will come back up.. Keep doing this till you have it running at 8000 or so with the needle set about 100 RPM down from peak. Fly it to check your lap times and do the final choke/needle adjustments to get your lap time where the airplane likes to fly. Once you are happy check the RPM and make a note so you know what it needs to be.

Couple items I've found are indications of having everything working right.. The engine should have a noticeable smoke trail, not like a piped engine or a Fox on Super fuel but it should be smoking enough to see it. If you are getting 8 or 9 minute runs on 4 ounces you ain't using enough fuel. You should be getting ~6 minutes on 4 ounces.

Hope this helps and let us know what your findings are. The above is what I've found works for me, disclaimer.. your milage may vary and if so I would like to hear about it. Lately I've gone back to playing with the 40's just to see if I could improve on what is an already great engine run. I've noticed marked differences in the different venturi configurations I've tried but think that might be a good subject for another thread.
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Dan McEntee
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« Reply #2 on: August 05, 2009, 12:54:38 AM »

    Hi Bob;
     Finally got a chance to add the screw to the venturi and get a few flights on it. I measured up the venturi while I had it out and it's a 7mm. I was at Oshkosh this past week to work the KidVenture venue, and had a cnahce to talk to Gilbert and Remi Berenger about their set ups.
   I test ran the engine in my drive way, and hardly noticed any change as I ran the screw in. I finally turned it in all the way and flew it like that at Oshkosh. I was at 5 second laps at 8000 RPM and right at 6 minutes run Time. I would like to get the lap times down to 5.5 or 5.6 seconds. I was afraid to open up the needle valve any more or the run time would suffer. The results made me wonder if the &mm is too large. Gilbert said he runs 5mm with the screw like you mentioned, but they run small diameter spray bars. I didn't measure the one that was with my engine.  Just for giggles and grins I went down to a 12-6 Zinger Pro and put up a flight at 8800 RPM on take off. The flight time went up to better than 7 minutes, and lap times were still in the 5 second range. Line tension was still great everywhere. I didn't get a chance to try it out at a slower engine speed, but hope to this weekend.
    What size venturi do you usually run, and does this 7mm sound too large for the choke screw to have much effect?
    Thanks a lot for your help.
    Dan McEntee
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« Reply #3 on: August 05, 2009, 03:30:47 AM »

Hi Dan,

Sounds like you are on the right track and for sure Gilbert and Remi know what they are doing with 4 strokes. To be honest I've never really given much thought to the starting size of the intake other than on the carbs I modify making it a little smaller than the stock RC barrel (little over 6mm) . On the UHP conversions I just use the middle insert that comes with the kit and never measured it. The screw changes it so much I don't think other than starting out way too large it's really critical. I do know that once everything is set and working you end up with a really small hole and I wouldn't doubt that starting at 5mm would work fine.

Also I've never really tried to get my lap times over about 5.2 seconds so your in uncharted territory. Try the Zinger with it slowed down and let us know how it does. As you alluded to it's best to set your RPM with the choke screw and keep the needle set just on the rich side of peak. Also be critical of it slowing down overhead and in the sq8, exceptional fuel mileage is an indication you may be running on the ragged edge of burn down..
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Dan McEntee
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« Reply #4 on: October 16, 2010, 02:02:38 AM »

   Well, here we are a year later, and I thought I would update my progress with the Saito/Score combination. At this time last year, I was still getting some inconsistent runs. I was at a point where I could see why some guys loved 4 strokes and some guys use them for paper weights! I finally decided to change tanks to a straight plumbed Sullivan plastic tank, as per something I read on the net somewhere. As soon as I did that, things got pretty steady. It would speed up a bit at the end of the tank, but nothing to make me uncomfortable, maybe a tenth or two. I played around with props some more and found some Rev-Up 13-7s that the engine and I like a lot, and I even started opening up the screw to let more air/fuel in for a bit more power and fuel consumption in the warmer weather. It was a weird summer, with the SIG contest getting canceled, and other things getting in the way, that I only flew in two contests this year. One was at the Paducah contest where I was fifth with no practice and won the Highest Scoring Arf Award ( Highest Scoring Score!! y1 y1) and our contest here in St. Louis. Vastly different conditions. Paducah was HOT!!!!! (95 degrees or so) but the engine and model performed well. I had settled on a screw setting where I had to short tank the fuel load to 3 1/4 ounces to avoid an over run and it was shutting down clean at about 6:35. As we got to the point on the calendar for our contest, it was cool and damp, with temps in the low 60's. Again, I didn't get the chance to practice and test the conditions, and my first official flight answered a question I had about 4 strokes and how fuel consumption was affected by temperature, I ran out of fuel in the overheads! Head bang Head bang I put on a little more than the 3 1/4 ounces I had been running and it obviously wasn't enough. Just for the sake of experimentation, I closed the screw in the venturi about two full turns and filled the tank to a full four ounces. .The second flight went well and the engine shut off at about the seven minute mark. It seemed to me that the engine was really happy and ran more consistent speed in the cooler air.    I haven't had a chance to fly it since but will get out some more this weekend. This session will be to test the current intake setting and to try a different prop. We got some of the Vess wood props in at the hobby shop I work part time at and I want to try one of those. I also had been looking at the different mufflers that are available for the Saito. The .56 in the Score came with a smallish. tube type muffler with a baffle that I think came from a Saito .72. My .62 came with a very small tube type muffler that I made a copy of tonight. I also made a copy of the .72 muffler but without the baffle and hopefully these will all get tried out. It's SO easy to change the muffler on these things!
   I would like to hear any thoughts or experiences with operating in different weather conditions, and if anyone else has treid the Vess props? I used to drink Vess Root Beer here in the St. Louis area, but never seen Vess props!
   Thanks a lot,
   Dan McEntee
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« Reply #5 on: October 31, 2010, 07:38:39 AM »

Dan,
can't comment on the Vess props  - never heard of them, but I have certainly experienced the same cold weather effect with regards to the Saito's fuel consumption.  It makes sense - colder air is more dense.  Engine gets more oxygen on the intake cycle (compared to thinner, warmer air), and therefore requires more fuel to maintain the same fuel-oxygen ratio.  Power output is predictably more, too. I use a 5-oz syringe for fueling, and measure fuel for every flight.  Sometimes there are variations between cold morning air and hot afternoon air on the same day.  Keep in mind, however, that I am not of the Bob Reeves / Moon brothers school of 4-strokes, with all due respect to their work.  I do not over-choke the intake, and I do use uniflow tanks. FWIW
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« Reply #6 on: November 01, 2010, 03:10:32 PM »

Dan,
can't comment on the Vess props  - never heard of them, but I have certainly experienced the same cold weather effect with regards to the Saito's fuel consumption.  It makes sense - colder air is more dense.  Engine gets more oxygen on the intake cycle (compared to thinner, warmer air), and therefore requires more fuel to maintain the same fuel-oxygen ratio.

Four strokes are much more sensitive to atmospheric conditions then 2 strokes. In particular, altitude. The Saitos are really very powerful air pumps. If you have kids, my guess is that, you could hook them up to one of those kiddy "Jumper Houses" and save yourself some compressor costs!!!
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« Reply #7 on: November 01, 2010, 09:57:41 PM »


I like to use props with more pitch in hot days and less pitch in cold.  Most wood props have a different pitch then it is marked.  For my OS 70 Ultimate I end up making a set of several Top Flite 14x6 props with true pitch from 5.0 to 8.0. It is hard to find two props that are exactly the same, not to mention props that have 7.5 pitch in one blade and 5.5 in the other.

In a very hot day with dead air I use a 8.0 pitch prop and in a very cold and windy day I use a 5.0 pitch prop.

My experience with an OS 70 Ultimate,  is that it is a lot less sensitive to weather and altitude change then 2S engines. I used this engine for 2 seasons and it was always within 2.9 Oz and 3.0 Oz of fuel.  From cold to hot, from 900ft to 4600ft elevation I could hardly feel any difference in engine performance. Seems it does not care about fluid dynamics and thermodynamics laws.

Martin
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