Sagitta 900 CG, throws, wing strength

[iflyelectric]

I recently inherited a Sagitta 900. Can someone please tell me where the CG is, along with the suggestion for throws? I also keep hearing about strength issues on the wing spar. I'm pretty sure this plane was built with no mods to the wing, as it was carried aloft via aerotow. So, will this construction be OK for a heavy duty high start, or do I need to remove the covering at the spar, and add some strength?

[Ollie]

A well constructed stock Sagitta 900 should be fine for any highstart up to 3/8 OD X 1/8 ID rubber tubing. The Sagitta can be safely winch launched if you don't go wild and hold the pedal down for more than a second or so. Just pulse it up with short pedal pulses. In winds over 10 MPH the launches should be done a little more gently by not pulsing the winch so much or by stretching the highstart a bit less than maximum.

You should begin flight testing with the CG at a safe 33 to 35% of the root chord. Remove 1/4 ounce of nose weight at a time between test flights until the plane becomes very slightly uncomfortable for you to fly perfectly smoothly. Fly it that way for a while and see if you become acustomed to it. As you become thoroughly familiar with the plane you may be able to tolerate a slightly more aft CG. Much depends on your eyesight, reflexes and preferred flying style. For the straight scoop on CG adjustments see:
http://www.polecataero.com/
Go to Articles in the menu and select the article by Dr. Mark Drela on CG.

Begin flight testing with 30 to 40 degrees of maximum rudder throw each way and about 10 degrees of stabilizer maximum throw each way. You may find it advantageous to put dual rates or exponential on the elevator to prevent over controlling as the CG is moved aft.

The Sagitta is a very sweet handling plane when it has been tuned to the pilots needs. It also has an exceptional wide useful speed range for a model of that era (circa 1981).

[iflyelectric]

Thank you Ollie, that helps a lot!

[iflyelectric]

OK, one more question about throws. The stabilzer throw is about 3/8" up, and 1/4" down) Is that about right? I'm not sure what maximum throw is, because of the servo arm length that I am using.

[Ollie]

By maximum, I meant with the stick at its limit, not the maximum obtainable by changing arm lengths. If you are referring to 1/4 and 3/8 inch deflection at the extreme trailing edge of the stab, that should be plenty. You may want to reduce that a bit after some flight testing, depending on your flying style. Please be careful not to over control on your first few flights.