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Old Oct 08, 2012, 05:55 PM
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Ian Easton's Avatar
United Kingdom, Scotland, Fife
Joined May 1999
2,849 Posts
Welcome aboard Julian!
Anyone have anything to say about the CG location?
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Old Oct 08, 2012, 08:24 PM
Registered User
New Zealand, Waikato, Ngahinapouri
Joined Jan 2011
57 Posts
Most utility aircraft have a CG range of 25% to 35% of chord measured from the leading edge, some aerobatic aircraft go as far forward as 20%.
On my models I usually start with 25 to 30%. As they say a forward CG plane flys like a pig, and rear CG plane flies only once!
Julian
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Old Oct 09, 2012, 03:59 PM
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Ian Easton's Avatar
United Kingdom, Scotland, Fife
Joined May 1999
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Well, I decided to move the CG forward to the "bent and buckled" location of 213mm from the TE. That should be a safe place to start and I only had to add 4ozs in the nose to make it happen.
Now I'm starting to feel like Felix Baumgartner about when I'll get that first flight in
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Old Oct 14, 2012, 04:26 AM
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New Zealand, Waikato, Ngahinapouri
Joined Jan 2011
57 Posts
Just measured my wing chord tonight and it is 335 mm.
CG of 25% would be 84 mm from LE or 251 mm from TE which is just about over the rear edge of the front spar.
CG at 35% would be 117 mm from LE or 218 mm from TE .
Can't help feeling that 213 mm from the TE edge is a little far back at 37% of the chord
Cheers
Julian
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Old Oct 14, 2012, 12:03 PM
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Ian Easton's Avatar
United Kingdom, Scotland, Fife
Joined May 1999
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Hmmm. I hope that someone that's flying one chimes in here.
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Old Oct 15, 2012, 02:50 AM
Registered User
New Zealand, Waikato, Ngahinapouri
Joined Jan 2011
57 Posts
Out of interest have a look at this CG calculator
http://adamone.rchomepage.com/cg_calc.htm
cheers
Julian
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Old Oct 15, 2012, 11:09 PM
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New Zealand, Waikato, Ngahinapouri
Joined Jan 2011
57 Posts
Hi
Have used dowels to locate and hold the front of the wing and two bolts at the rear. Some pics
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Old Oct 16, 2012, 04:53 AM
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Oxford, UK
Joined Mar 2009
65 Posts
Have to admire your build techniques Julian and speed of assembly. Will watch your progress with great interest.
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Old Oct 17, 2012, 02:24 PM
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Tim Trick's Avatar
The Netherlands
Joined Apr 2004
593 Posts
Ian,

My falcon has the C of G located at 118 mm from the leading edge (full chord is 340 mm). I took it from the Buckle plans and so far it has worked fine.

Cheers

Tim
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Old Oct 17, 2012, 03:44 PM
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Ian Easton's Avatar
United Kingdom, Scotland, Fife
Joined May 1999
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Thanks Tim.

I think I'll bump my CG forward a little bit more just to be safe for that initial flight. I experienced tail heavy models before on first flights and they're no fun.
Plan is to get it in the air this upcoming Monday, weather permitting (ie, high winds).
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Old Oct 19, 2012, 10:59 PM
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New Zealand, Waikato, Ngahinapouri
Joined Jan 2011
57 Posts
Been busy with making the undercarriage, making a movable engine mount to help later with CG position, and ailerons. Will make a start on the tail feathers next.
Good luck Ian with your maiden, 118 mm from the LE sounds like a good place to start, puts it at 35%
Cheers
Julian
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Old Oct 20, 2012, 04:50 PM
Experienced Balsa Mangler
United States, AL, Tillmans Corner
Joined Oct 2012
716 Posts
Hi, all!

I'm new to the group, but not to building. Following along through these multiple builds has been a pleasure, such that I'm starting to cut some cardstock patterns for the pieces. Maybe I can post some pics (if and) when I start mangling balsa...

Question for those of you who have built and flown your Falcons -- Which engine (size) are you suggesting as the "ideal" for this bird? I've heard anything from 4S52 to 4S91, which is a broad range. I tend to think a 4S91 would be a bit much, personally, as this was more a "floater" than a "hole puncher" of a design. I also think the 4S52 might be a bit light for that 98" wing. It reminds me of the 72" J-3 kit (Sig/Berkeley) I built 10 years ago with a Saito 30. It flew, smooth and slow, but you had to keep full throttle to do anything more than glide back down.

Julian, I'm especially following your aileron conversion, as that's how I plan to work mine up.

Ian, I like your solution of mounting servos in the tail. Given the thickness of the fin and stab, I presume those are not "standard-size" servos, but something much smaller. Any general suggestions as to which servos would be strong enough yet small enough to fit in that narrow area?

Beautiful frame-ups, everyone!
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Old Oct 22, 2012, 05:01 PM
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Ian Easton's Avatar
United Kingdom, Scotland, Fife
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Thanks CP. I didn't mount servos in the tail, I think Old timer did that.
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Old Oct 23, 2012, 04:32 AM
Registered User
Oxford, UK
Joined Mar 2009
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Servos used in the tail - Hitec HS82MG
Ray
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Old Oct 23, 2012, 09:35 AM
Experienced Balsa Mangler
United States, AL, Tillmans Corner
Joined Oct 2012
716 Posts
Ray and Ian,

Thanks for the correction and update. Using the metal gear version makes sense.
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