Scale RCM 1/3 Scale Champ Build

[TonyHallo]

I used https://rcplanes.online/cg_calc.htm to calculated the safety margin, it came out at 7%. The wing is 20", so 6 5/8" puts the CG at 33%. According to the calculator the neutral point is at 8" or 40% of the cord. I believe I will make a heavy prop washer out of brass. this could add 1/2 pound to the nose.
Each wheel weighted 15.2 pounds and the tail wheel was 4.5 pounds, 36 pounds total so the 40 pound seems very reasonable.

 

[TonyHallo]

Here is a view from the front seat.

 

[Snoopy1]

40 lbs that is getting up there if my memory serves me right were you not going to put a Roto 85 in the plane.

 

[TonyHallo]

No, it has a the Roto 85 FS. At 40 pounds it has a cubic loading of 7.5, not far from a trainer. The wing is rather large, 2800 sq. in.

 

[Snoopy1]

Wow 7.5 cubic loading is very low. That plane has a very large wing. It will fly for sure.

 

[TonyHallo]

First real project where I appreciate the power crossfeed, mirror finish on the fine feed rate. 0007"/ rev. The other thing I appreciate is McMaster Carr, ordered this 2 1/2" x 1/2" brass disc yesterday afternoon, on my porch this morning. This is replacing the prop washer supplied with the Cub Hub from Tru turn. The 1/4" aluminum weights 1.5 ounces, the brass is 9 ounces right where it does the most good. It's clamped in the milling machine, once it is centered will use the DRO to drill the six holes for the bolts.

 

[TonyHallo]

Center the piece on the mill table and used the bolt circle function on the DRO to lay out the 32 mm bolt circle. I drilled all the holes with a center drill first than went back around and drilled the through holes. Fits perfectly.

 

[Snoopy1]

I used https://rcplanes.online/cg_calc.htm to calculated the safety margin, it came out at 7%. The wing is 20", so 6 5/8" puts the CG at 33%. According to the calculator the neutral point is at 8" or 40% of the cord. I believe I will make a heavy prop washer out of brass. this could add 1/2 pound to the nose.
Each wheel weighted 15.2 pounds and the tail wheel was 4.5 pounds, 36 pounds total so the 40 pound seems very reasonable.

When you use this program what percentage do you use.

 

[TonyHallo]

I started at 5% then increased to 7% since the calculated CG was behind my measurement, They tell you between 5 and 15 is normal. If you enter zero it puts the cg on the neutral point, if you set it to 15 it puts the CG at 25% of the cord.

 

[TonyHallo]

I think I looked at every Champ photo on Airliners.Net and finally decided to paint the interior light gray, I found several examples of this. Started by covering the headliner behind the rear windows with a piece of SeeTemp to finish it off, then sanded and dusted a couple of coats of Rustoleum Stone Gray spray paint. Tomorrow I hope to paint the front posts, a pillars and under the dash flat black.