On my first glider, the CG ended up being different from where the instructions say it should be, possibly because the laser cut pieces for the fuselage and/or wings were slightly off from the original (here you can see that the end of the fuse sits a little forward of the wing’s T.E. by about 4mm).
The Estes instructions specify the CG location should be 1” forward of the wing trailing edge at the root, while a Nighthawk trimming article I read locates the CG at 0.9” from the rear of the fuse based on the aerodynamic coefficient and maximum glide duration
of the glider.
My prelim trimming tosses put it at 0.75” forward of the wing’s T.E. at its root. Not totally unexpected, as the Estes instructions mention the CG location may be different based on things like the final airfoil and finish of the glider. I’d also add that the density of the balsa fuse and wings and density distribution also makes a big difference. My glider only required 1.14 grams of nose weight to get a nice flat glide.
For my 2nd
clone, I decided to make the end of the fuse go all the way to the wing’s trailing edge where they join, by sanding off the front edge
of the wings where they come to a point. This seems to more closely match the illustrations in the original build instructions.
Should be interesting to see where the CG ends up with this one, since it uses a more traditional airfoil and the wings are just a tiny bit further forward. My guess is that the CG will end up having to be a bit further back than the first glider because the wing’s leading edge on this second one is a bit thicker (so heavier), biasing the overall weight toward the front.