Hatchling (oz15293)

 

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There is a small piece of conflicting information in the instructions. Under Part I Constructing the Flying Surfaces, Step 6. ‘Make a mark 3/8” from the wing trailing edge on the bottom surface of each wing. This is the desired Center of Gravity.’ Then the author does nothing with this bit of information. However, if you revise Part III Final assembly to read:
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19. Make a mark ¾” from the rear of the straw: this sets the location for the trailing edge of the V-tail (the ¾” at the tail is where you’ll grip the fuselage while stretching the catapult for release).
20. Load your glue gun, and plug it in. Pinch a clothespin onto the fuselage nose, and another one at the tail, such that the fuselage stands on the legs of the clothespins, and the catapult hook is pointing downward. Add a clothespin to each standing clothespin to steady the setup (see photo). (The clothespins aren’t really necessary; you can get the same alignment by carefully holding it.)
21. Holding the V-tail in place, and checking proper fore/aft placement, centerline placement and V-tail alignment, tack glue the leading and trailing edges of the V-tail to the straw and hold in place while the glue cools. If it looks good, move on to the next step. If it doesn’t, re-melt the glue spots with the hot metal nose of the glue gun, and try again.
22. Steadily and slowly apply a bead of hot glue the entire length of the chord on one side, let dry and harden, then repeat on the other side. These beads of glue don’t have to be perfect, but you’ll find your technique improves with repetition. Try not to push the V-tail out of alignment with the glue gun.
23. Now remove the clothespins (if you’ve used them,) and find and mark the balance point on the fuselage of this assembly so far. Next place the wing over the straw and locate the wing CG mark made in Step I, No.6 above over this balance point then mark the location of the leading edge of the wing.
24. Being mindful of alignment to the fuselage and V-tail, tack glue the wing to the marked location on the fuselage. Once satisfied with placement, squeeze a bead of hot glue on either side of the chord of wing.
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If the model is built following the instructions as written with the wing just two inches aft of the front of the straw, at least on my first build it took a rather large amount of tape to get a reasonable glide. Models built putting the wing CG over the CG of the fuselage came out needing no CG adjusting tape at all!
Thomas Solinski - 01/01/2025
Thomas, Thanks for trying the design! I hope you got as much joy out of flying it as I have.
I experimented with wing placement when building prototypes, and found that any appreciable gap between the back of the nose dowel and the leading edge of the wing could potentially produce a "failure point" there. This is why I recommend a 2 inch dowel and a 2 inch nose-to-wing leading edge measurement. Additionally, moving the wing aft shortens the aft fuselage length which can affect stability. All that said, one could certainly save some nose weight by moving the wing aft. I'm happy you found success with your method of CG location and am glad you've offered it as an alternative!
Mark Ferstl - 06/01/2025
Here's a couple more Hatchling photos [main pic, 004]. Thanks,
Mark Ferstl - 06/01/2025
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