C of G

[Hogster]

Hi all, I got another newbie question. I have an aero40 trainer and the CofG label on the fuselage does not match the distance from the LE written in the manual. Its about a 1/2" forward. I used the c of g calculator from http://adamone.rchomepage.com/cg_calc.htm and the result agrees with the manual.

So which do you think I should I take notice of, the label or the manual.?

[Adam Lomax]

personaly i would go with the manual, or you could go in the the middle of both

Edited By Adam Lomax on 27/02/2010 19:45:49

[Peter Miller]

The trainer will have a parallel wing. Check how far back a 1/4 of the chord is. i.e 25%.

 

Simply divide the width of the wing by 4. See which that measurement coincides with. 25% is safe, further back may make the model more twitchy. Much further abck is bad news. Further forward is not too much of a problem, you will just need a bit of "up" trim.

[Hogster]

Thanks for your quick replies chaps

Well, the wing chord is 285. So 25% of that is 71.25. The manual states 88 - 101 and the label is set at 82mm. The thing is that to get the balance right at 82mm I need to add 3-4oz to the nose but not at 101mm. The CoG calculator gives the answer 88.6. Which would actually give me good balance without having to add or move any wieght.

Edited By Hogster on 27/02/2010 20:26:03

[Biggles' Elder Brother - Moderator]

Assuming a typical flat bottomed trainer wing section the CoG can generally be placed anywhere from 25% to 33% of the chord without anything getting too exciting!

 

25% would be 71mm

33% would be 95mm

 

I would suggest anywhere in that range would be OK. As 82mm is kind of 'middle of the shop' I think starting there should be OK - and it agrees with the manual. I'd think twice about anything much more than 95mm, while 101mm sounds a little "adventurous"!

 

BEB

[Hogster]

Thanks BEB. Thats put my mind at rest