C of G issue.

[Paul Holmes 2]

I'm in the process of refurbishing my mini CRAFT JAVELIN after being left dormant for many years. A couple of repairs were nessceary so everything was stripped down. Now it's all back together again I'm trying to set the C of G back into position. As it seems of misplaced the manual for it can anyone help me please.

[Paul Holmes 2]

This is the smaller SC52 powered version.

[Cuban8]

Conventional enough wing, so I'd balance the model at 25-30% back from the leading edge at the root for starters. Keep the elevator movement to no more than 1/2" either way (slightly less on rates) for the first flight to see how things are.

 

You can use this...https://rcplanes.online/cg_calc.htm  but I think the figures will come out about the same.

Edited November 20, 2023 by Cuban8

[Paul Holmes 2]

It seems to balance out at about 27% of the wing cord which amounts to 87mm back from the leading edge.

[Simon Chaddock]

27% chord should be quite a 'safe' position so you are good to go.

Not knowing the nature or location of the repairs you need to be sure the relationship of the wing to tail plane incidence has not changed. If it has it can make a big difference to how the plane behaves.  

 

[Martin Harris - Moderator]

I can't recall the recommended engine sizes but I flew mine quite successfully for many months on either an Irvine 40 or 46. I have a feeling that 46 was the largest recommended size.

 

I then had the bright idea of fitting an MDS58.  With dire warnings of dead sticks ruining my day ringing in my ears, I flew it numerous times with splendid performance...until on a low pass, there was the ominous buzz of elevator flutter, followed a fraction later by an uncontrollable dive into the ground.  There was little left of any use although the engine still runs strongly nearly 20 years later in a winter hack Extra, wearing a strap on silencer due to the silencer mounts being smashed off the crankcase casting.

 

What I'm trying to say is be very careful that your elevator linkages are in good condition and without slop with what I believe is quite a large engine for the model.  You might do well to pay attention to the control horns as I've found that some types can deteriorate badly with age and go brittle.