Okay, as of a couple weeks ago, I've built a lot of the airframe! I have a couple thoughts already before I finish it up, so this post is going to be a big jumble of those.
Wing:
The alignment features for Wing1 (leading edge of a wingtip) and Wing4 (trailing edge of a wingtip) don't work super well, so it's difficult to get the trailing edge of Wing4 to line up with the rest of the trailing edge. This system is also a bit of an issue when attaching HTP2, but that part is smaller so it's a bit easier to keep it in place.
If the main mating faces were't curved, this would solve the problem though. The same tab and slot system is used to align the parts of the vertical tail, but with flat mating faces and that works much better.
Also, the video doesn't show the builder applying CA to glue the two wing halves together where they join at the center, but it's clearly there just before the parts are joined! There's a cut at 2:40 and CA appears around the edge of one wing half:
The wing gets treated as one piece in the rest of the video, so I don't think it's meant to split in half like on a Radian. Definitely something for builders to watch out for!
Fuselage/HTP:
An FT pushrod (23") is long enough for the elevator, but the 650mm pushrods I found on Aliexpress seem to be slightly more flexible, which helped a bit with threading it through the curved guide inside the fuse/V-stab. I'm still encountering a bit more resistance than I'd like with the elevator, but the servo can move it so hopefully it won't be a problem. I think the resistance is because I had to drill out the center pivot point hole to accommodate the 2mm CF rod and I didn't do that very cleanly. Definitely take care with this section of the build.
B pack compatibility:
It was a tight fit to get the FT9Gv2 servo into the elevator servo holder, so I'm interested to see if this will also be an issue with the wing servo mounts as well. It's doable though:
Also, make sure you push the servo as far down into the fuselage as you can when gluing the mount in place! I glued it in a little too high on my first attempt, and the linkage stopped would have interfered with the bottom surface of the wing.
I also skipped ahead a little bit and found out that the shaft for an FT B pack motor doesn't fit through the hole in Spinner2, so I quickly modified that in Onshape to enlarge the hole to 6.4mm from 5.2mm and reprinted it. The modified version works great, but I don't know if that's something I can share. I tried drilling out the hole but that was hard to do accurately, so I would recommend just modifying the STL and re-printing if you run into that.
Be sure to print the
FT motor shim as well out of something heat-resistant, since that isn't included in the Spark download.
Ordering parts:
Make sure you get all button head screws for this build! The recommended parts page on the Eclipson website has a link for socket head screws for any M3 screws longer than 20mm (including the M3x30s which are used to hold the Spark's wing down), but the build video shows button head screws at 7:25, which are the more aerodynamic choice anyway. The recommended screw kit for shorter screws is all button heads.
Next steps:
I'm going to work on electronics installation this week, so I need to do some thinking about where to put everything inside the fuselage. The 900mHz antenna of the TD R6 I'm using is probably going to be the biggest challenge, since it's sort of T-shaped. The initial phase of the build went way faster than I was expecting, so I'm excited to finish it up soon!
