Engine basics > Four strokes only

Saito 56/62 carb mod for CL

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Bob Reeves:
Think I have it finished..

Check this out and let me know if something isn't clear or I missed anything.

http://www.tulsacl.com/SaitoCarb.html

BillLee:
Hi, Bob;

Good article! However, ... (isn't there ALWAYS a "however"?  :) )

You say in the article:

"... this particular prop ... is effectively at least a 6.5 even though the pitch gauge measures 5.5."

Could you expand on that a bit?

Second: You say
"Plastic Clunk tank plumbed conventionally on muffler pressure."

and then
"...with a conventional tank is you will get a slight speed up during the flight as the fuel is used up."

Do you attribute the speed up to the use of the conventional tank? Would a uniflow eliminate that characteristic?

Regards,

Bill Lee

Bob Reeves:
Thanks Bill, will try to answer your questions as best I can.

I'm not real sure what brand the carbon 3 blade prop is, I purchased 3 of the silly things from Modusa when they were selling Stalkers. It's very possibly a Kaz Minato prop as it looks just like a couple others I've seen from him. I just stuck it on the 62 one day to see what it would do and it worked. I don't have his prop list but if he is selling a 3 blade CF 13-5.5 for the Stalker 61 I would almost bet it's the same prop.

Actually I didn't just stick it on.. First I repitched one to 6.5 thinking a 5.5 pitch couldn't possibly work and tried it, at this pitch it was too much load for the 62 and the poor thing wouldn't rev over 8100 wide open. I then went down to 6 pitch, it was flyable but still quite a load on the engine. Finally I just stuck on a stock one, adjusted the intake for 8300 and it worked.

When I say effective pitch I'm going by what the lap times are for a given RPM using a Rev-Up 7 pitch prop as a reference. I only had to increase the engine RPM by about 100 to get the same lap times I was with a Rev-Up. If it was a real 5.5 pitch prop I would have thought the difference would be more like 4-500.

Another example is the Evolution 11-7, it actually measures a 7 on my pitch gauge as does a Rev-Up 11-7.5 but I have to increase the engine RPM by about 200 with the Evo prop in order to get the same lap time as the Rev-Up. I don't claim to fully understand why, I just try things till something works. Maybe someone that really understands prop efficiency can enlighten us.

Yes the conventionally plumbed tank is responsible for the speed up but it also gives the most consistant runs. A conventional tank gives up it's fuel load much easier than a uniflow tank and 4 strokes need all the help with fuel delivery they can get. Some have said they can make a uniflow tank work but I have not been able to without experiencing inconsistent run issues that were much worse than a slight speed up during the flight. It's a compromise I am willing to make considering the alternatives.

When I had the Saito 30 on the TwistMaster I was bound and determined to make a hard uniflow tank work. I built 4 different uniflow tanks during this ordeal and tried every configuration I could think of including two versions of chicken hoppers. Finally I stuck on a plastic clunk tank with one vent in the top inside corner and haven't looked back.

One configuration I haven't tried is one I received from Martin Quartim along with the Rogue venturi info. It sure looks like it would be worth trying, I just haven't gotten around to it...

john e. holliday:
Bob, that is a great artical on your set ups.  But, for guys like me that have no machining experience let alone a lathe are up a creek so to speak.  When I was flying F2C I always had a pilot that was a machinest also.  Thanks for all the info.  DOC Holliday

Bob Reeves:

--- Quote from: john e. holliday on August 04, 2009, 09:14:41 AM ---Bob, that is a great artical on your set ups.  But, for guys like me that have no machining experience let alone a lathe are up a creek so to speak.  When I was flying F2C I always had a pilot that was a machinest also.  Thanks for all the info.  DOC Holliday

--- End quote ---

Thanks Doc. Actually Allan sent me an email hopfully volunteering to put together how he did his Saito 40. He doesn't make a new barrel which is the machinist part, instead he takes the temper out of the stock steel barrel so it can be drilled and taped. When he gets it together I will post it on the Tulsa site. This would allow anyone without a lathe to accomplish almost the same setup. Personally I like the idea of replacing a 1/4 ounce chunk of steel with aluminum but I also have the means to make it happen and realize many don't.

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