IMAC Scratch build Laser 200

[TonyHallo]

I opened the dranwing and measured the root on my screen, 5 3/8", I find the cg at 1 3/8" back, that's 23 1/2% at the root. The tip is 3 1/8" with the cg at 7/8", that's 28%. I get the cg at 25% of the MAC.
I put the platform into one those fancy calculators online ( do prefer the HP with RPN however) I got 25% at 1.32" back at the root and 33% at 1.66" back at the root.

 

[Forgues-Research]

thanks guys , I will have to look at this very carefully ,

 

[Forgues-Research]

I was looking at this , can this be used to calculate ?

 

[Snoopy1]

I was looking at this , can this be used to calculate ?

Yes that is the one I always use.

 

[Forgues-Research]

Yes that is the one I always use.

I did use this and it says the cg should be in the center of the tube/spar, so I should be good to go

 

[TonyHallo]

Roger,
Try this calculator https://www.ecalc.ch/wingdesigner.htm

 

[Forgues-Research]

Roger,
Try this calculator https://www.ecalc.ch/wingdesigner.htm

Hmm seems very interesting, will definitely take a look

 

[Forgues-Research]

I was looking at this , can this be used to calculate ?

using this method I find the CG at the center of the spar,

 

[Forgues-Research]

Hmm seems very interesting, will definitely take a look

now using this method, I find the CG is where it says on the plans, I am perplexed but doing it this way I will be sure it is not tail heavy, and then can adjust .

 

[Snoopy1]

now using this method, I find the CG is where it says on the plans, I am perplexed but doing it this way I will be sure it is not tail heavy, and then can adjust .

Just opinion the Ecalc has some fudge factors in it also the safety margin that is why I am not fond of it. The one you showed on the drawing is the true method of find Mac.