Hi Martin:
I wish I had taken a picture of what I did to the venturi, but now I do not want to pull the engine just to take a picture. When I do pull the engine, though, I'll document it so
you can see what I did.
I'll try to explain it verbally here. I originally tried the screw method Bob Reeves is so successful with, but was finding that I was adjusting the screw almost totally into the venturi w/o
much change in run.
So, I pulled the motor, and took a piece of brass tubing that was small enough to sort of fit into the venturi, and I extended it to about 1/2 inch above the existing venturi housing.
I soldered a plate to the outside of it and bent the plate at an angle so that this brass "tab" would reach and cover the 2 closest bolts of the backplate of the engine.
I drilled 2 holes in this brass plate,for the bolts, and bolted the whole sub assembly to the backplate of the engine. I used a high temperature automotive silicon sealer around
the brass tubing to seal it and sort of bond it to the venturi. I also put a fine screen venturi cover over the brass tubing like some guys do to regular 2 stoke intakes - you know,
the kind that is made of rubber and fits tightly around the venturi to keep dust and foreign stuff out of the intake. I did that to keep foreign matter out, and to control spray-back
into the engine compartment.
I fired her up and she immediately calmed down in flight. At that point I started experimenting with all sorts of props. I am not good at re-pitching, and I do not like complicating
things, so I started my quest on what prop woould work the best. Dave Cook felt that for testing purposes, APC props were, very uniform . They do not seem to vary much in
flight characteristics from several props of the same dimensions. So, if you break one, another of the same will fly rather close to the original. Manufacturing duplication seems to be very accurate. So I experimented with various sizes, in APC as well as some wood Zingers.
During this experimentation period, I realized that this Saito 62 4-stroke seems to need a lot of prop to settle it down. My fuel is always Powermaster 20/20, and other fuels do not seem as consistant, for me at least. I ended up using a Bolly three blade 12/6.5, and an APC 13/7 with the APC 7 pitch 13 inch prop giving a slight edge on where I wanted to be with this ship.
I fly on 66 foot lines , eye to eye, and aim for about 5.1 to 5.3 lap speeds. When the ship settles down after takeoff, it maintains the lap speed all the way through the flight. At the end,
the Saito 62 revs up a bit for about one lap and just quits. I am of the opinion I get better runs with high pitch props (7") , and aim to have a release static rpm of 7200 to 7500 at
takeoff. During flight, the plane's speed unloads the prop to probably around 8,000 or so rpm which is close to the max torque . I aim for 2 or 3 clicks shy of top rpm, on the rich side
as most 4-stroker's recommend. It seems to work for me and I get flight after flight in consistent runs. I'm impressed, and so are people who see it fly. When I take the engine out of this bird, I'll take pictures and post them for you. The whole thing was real easy to do.
I fly both 4-stroke and electric. I flew 4-stroke in competition last year because I wanted to get educated about 4-stroke and compare its power the constant power of electric.
Both are similar in that there is no definitive 2-4 break as in 2-stroke glow engines that are muffled. Pipes are probably a different breed variant. I have enjoyed the ride, and
most importantly, I'm having fun. I do not know what it is, but I absolutely love the sound of a properly set up 4-stroke. And the power, well it's just ther, all the time, giving you constant attitude. I actually did a 6 sec. lap speed reverse wing over with this bird. I could not believe it with my own eyes. I'm having FUN!!!!
If you have other questions, feel free to ask. I'm not an authority, but my system works.
Thanks again,
Will Moore
Topic: Another gray airplane (Read 2356 times)