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Building Tips and technical articles. => ARF'S => Topic started by: Larry Fulwider on June 03, 2010, 03:14:06 PM
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I just finished a Tutor II, and the leadouts can't be set far enough forward (using Line III numbers).
Here is what I have:
Wing LE Sweep: 2 1/2"
CG: 3" from LE (root)
Front line (all the way forward): 1 3/8" from tip
Rear Line (all the way forward): 2 3/4" from tip
Actual Line Rake from CG: 1 9/16" behind CG
Line III Spec (most rearward of combos tried): .8559 (<7/8")
Tutor II rearward "error": > 11/16"
Wow, that seems like a ton to be off :o . Am I missing something? I had a previous Tutor II, but it met its demise before I finished trimming it -- although, it seemed to be doing great at that point. I think I left the leadouts alone on that one, as someone else had assembled it. However, the wreckage confirms the leadouts were in fact as forward as possible.
Any ideas what might be wrong here? (Hopefully, a bonehead error on my part)
Larry Fulwider
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Are you sure that CG location is really correct? I don't mean correct per the plans...it seems to me that TF screwed up the FS CG location instructions, and maybe the Nobler, too. Or, is something wrong with the L.O. guide, limiting its travel? D>K Steve
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Are you sure that CG location is really correct? I don't mean correct per the plans...it seems to me that TF screwed up the FS CG location instructions, and maybe the Nobler, too. . . .
. . .
Steve –
Thanks! Yes, you are correct. The CG location is part of the problem – but not the entire problem. Here is the info from the TF manual:
Recommended: 3”
Most Rearward: 3 3/8”
Most Forward: 2 ¾”
My calculations show the following CGs as % MAC:
2 ¾: 14.2%
3 : 16.5%
3 3/8: 19.8%
3 7/16: 20.4% (now)
3 ½: 20.9%
With the CG at 3” (required half ounce of nose weight), the Tutor II flew like a truck. Removing the nose weights put the CG at 3 1/4'” -- Still nose heavy. Adding tail weight, ended up (temporarily) at 3 7/16”. At that point, I changed to a lighter muffler (after a few calculations, which worked out fine), and I have started over on tail weight, keeping the CG at 3 7/16”.
However, even if I go 3 ½” as we proceed, that still leaves a 3/16” discrepancy between Line III and what is available.
. . . Or, is something wrong with the L.O. guide, limiting its travel? D>K Steve
No, I tore into the crashed one, and that is the way the guide is made – two parts, one rear slot, one front slot, and not easy to change (would require cutting into the wing).
Larry Fulwider
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Have you even flown the plane with the leadouts set at mid range? There have been too many Tutor II's out an flying that the leadouts are wrong in my opinion. Also I think some of these programs complicate things too much. H^^