ORIGINAL: Rocketman_
[
]Does the Saito 100 have some kind of inherent fuel flow problem. Is there a real need to buy a pump/regulator if the tank is located at the firewall of the UCD 60? It seems that some people may be trying to solve a problem that doesn't exist. The Saito 72 in my UCD 46 has no such problem.
If the tank is moved to some location that is distant from the engine a pump/regulator may be necessary. Is it correct to assume that some fliers relocate the tank farther back in the UCD fuselage to achieve a more favorable CG location for 3d flying?
I moved the CG farther back in one of my UCD 60's (I have two) by moving the battery to the rear of the fuselage in a hatch I made in the bottom. In this way I avoided having to move the tank, the throttle servo, the receiver and having to buy a regulator for $43.00 plus shipping. I did notice that the plane becomes a little squirrelly with 3d elevator throws.
My two UCD 60's are powered by OS 91 2-strokes. The OS 2-stroke with its giant muffler weighs 24.3 oz which is more than the Saito 100 4-stroke. A Saito in the nose may move the CG a little farther rearward.
My next engine purchase may be a Saito 100 4-stroke and I was hoping to use it without buying any additional gadgetry to attach to it.
There is no inherent problem with a Saito 100. The reason people use a regulator on UCD's is because Great Planes did a poor job of engineering the plane itself. The stock location of the tank puts the centerline of the tank at least 1 inch above the carb centerline. It only makes sense that if a tank is higher than the carb it's going to syphon down into the carb and flood the engine. When the tank and the carb at at the same level they are at equalibrium and there is no tendency to load up the carb with fuel. A regulator stops the flow of fuel when there is no demand for it (suction). Thats why they work perfectly in this application.
Great planes should've dropped the tank down about an inch or so and there never would've been a problem.