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dashvii(at)hotmail.com
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 Posted: Thu Aug 13, 2009 7:21 pm Post subject: Lightning C.G. Change? + question for Johnny Thompson |
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| Quote: | | All C Can anybody tell me what the difference in C.G. between an aircraft with the shorter motor mount verses the longer motor mount is? Has any aircraft had one and then switched to the other?Johnny C You had a write up in a recent Lightning newsletter about Greg's version 2.0 Lightning. I had flown his first version previously. Do you know if he switched motor mounts to the longer C or is that entire C.G. movement due to the lighter fuselage than the original? I am working on a new article for the newsletter and these things would help me to figure a couple of things out. Thanks C Brian W. |
Get back to school stuff for them and cashback for you. Try Bing now. [quote][b]
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8wn(at)comcast.net
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| Posted: Thu Aug 13, 2009 8:47 pm Post subject: Lightning C.G. Change? + question for Johnny Thompson |
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Hello Brian
Greg's lightning went from short mount to long. There are some major differences in his old fuselage to others. His tail section was very heavy so he put about 14 pounds of lead on the very front of the engine. This was done to bring his CG forward to match other aircraft in the fleet. All this being said, the long engine mount was the main reason the CG shifted forward even with the weights removed from the engine. I weighed it on my certified aircraft scales and will look up the numbers and get back to you. Johnny
[quote] ---
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Clive J
Joined: 03 Nov 2007
Posts: 340
Location: UK
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| Posted: Thu Aug 13, 2009 11:18 pm Post subject: Lightning C.G. Change? + question for Johnny Thompson |
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Can't you just use the standard spreadsheet and take the engine weight
off at the old station and put it back at the new one?
I used this approach to see what the difference was with the new mount
that Arion send me. Early indications was the engine would be just over
an inch forward of it's old position so I used 30 mm
If you take the two lines in yellow out you can see the resultant C of G
move back. I was surprised how little the C of G moved with engine
position movement.
Or am I missing something?
Regards, Clive
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EAFerguson(at)aol.com
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| Posted: Fri Aug 14, 2009 4:39 am Post subject: Lightning C.G. Change? + question for Johnny Thompson |
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In a message dated 8/14/2009 3:19:12 A.M. Eastern Daylight Time, clive.james(at)uk.bp.com writes:
| Quote: | Can't you just use the standard spreadsheet and take the engine weight
off at the old station and put it back at the new one?
I used this approach to see what the difference was with the new mount
that Arion send me. Early indications was the engine would be just over
an inch forward of it's old position so I used 30 mm
If you take the two lines in yellow out you can see the resultant C of G
move back. I was surprised how little the C of G moved with engine
position movement.
Or am I missing something?
Regards, Clive
|
Don't forget to move the prop, spinner and any other accessories not included in the engine weight.
Earl
[quote][b]
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Clive J
Joined: 03 Nov 2007
Posts: 340
Location: UK
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| Posted: Fri Aug 14, 2009 7:47 am Post subject: Lightning C.G. Change? + question for Johnny Thompson |
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That's a good point, WR Earl, these will be at a different station of
course, further forward more effect.
With such changes why aren't you re-weighing?
CJ
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8wn(at)comcast.net
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| Posted: Fri Aug 14, 2009 12:42 pm Post subject: Lightning C.G. Change? + question for Johnny Thompson |
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Brian
Greg's CG moved forward 3.5" but remember his was the 2nd to fly and many, many changes have taken place. He had 1 pound of led in the rudder the glass was heaver in the rear so he had to put 13 pounds of lead on the very front of the engine case. Then removing the lead weight forward and aft,new fuselage, extended eng mount he now has moved the CG forward 3.5 inches.
In the next two weeks I will do a new W&B on my aircraft. I have installed the 30 gallon tanks and will add weight to the front of the Eng to compensate for not having the extended mount. Will let you know. Johnny
[quote] ---
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