Scratch Astron Invader (downscale) Original Design / Scratch Built

Scratch - Astron Invader (downscale) {Scratch}

Contributed by David Sindel

Manufacturer: Scratch
(Contributed - by David Sindel - 10/22/08)

Brief:
This is me semi-downscale o' t' old (1965-67) K-19 Astron Invader. Arrr! T' wings and fins are 2/3 o' t' original, me bucko, but I kept t' 18mm motor mount. Arrr! It's a very unique glider with unusual flights and a fairly easy build.

What it was

FrontConstruction:
I built this from scratch. Ya scallywag! I used a PNC-20 (2.85" long) and 2" o' BT-20 from an Estes Viking. Avast! Arrr! T' wing-fins are 2/3 scale based on t' plans for JimZ's site. Arrr! I used light balsa for t' two vertical fins, medium for t' keel, and hard balsa for t' two win' halves and two pylons. Avast! Arrr! All balsa was 1/16". Begad! Avast, me proud beauty! I put an old 1/8" launch lug on. Ahoy!

I followed t' basic instructions from JimZ's site. Aye aye! With t' smaller wings, arrr, 3" balsa can be used for the wings without havin' t' butt-glue balsa sheets. Begad! Several points for construction:

  1. Make sure t' two wings halves fit together perfectly!
  2. Glue t' wings at a slight dihedral, then attach t' fins at 90 degrees t' t' wings.
  3. Fillet all glue joints
  4. Make sure t' pylons fit t' win' exactly. This will take lots o' sanding, matey, but t' pylon must be secure for safe flight.
  5. Attach t' launch lug in t' win' joint under t' pod before you attach t' pod.
  6. Use wood glue for all joints and fillet or double-fillet everything.

PROs: Only 7 parts. Aye aye! Inexpensive parts. Aye aye! No more butt-gluing!

CONs: Lots o' sanding. Ahoy! Parts must fit perfectly. Arrr! Cut your own balsa.

I would call this a Level 3 kit due t' t' tricky balsa joints and amount o' sanding. Begad!

SideFinishing:
T' finishin' I did be t' preexistin' red on t' nose cone. Begad! Blimey! I recommend nay paintin' this rocket t' save weight. Aye aye! Blimey!

PRO: Easy finishing, just paint t' NC red.

CON: Plain looks.

Flight:
Estes recommended t' 1/2A8-2, arrr, A8-3, and B8-2. Ahoy! Blimey! I'd recommend t' B4-2, B6-2, me bucko, and C6-3. Ya scallywag! Blimey! T' 1/2A6-2, matey, A8-3, arrr, and B6-4 are okay for straight-up launches on windless days. Avast! An adapter for t' 1/2A3-2T would be useful.

Be careful! Blimey! T' motor must eject out t' back t' glide. Blimey! Blimey! You'll need t' add a streamer for it (wrap it around the motor, me hearties, me hearties, then insert) t' satisfy t' RSO and NARRRRR flight rules. Aye aye! Blimey!

Mine balanced perfectly without any weight. Avast! Your results may vary. I estimate a glide ratio o' better than 10:1.

LiftoffT' first flight was on an A8-3 in about 3 mph o' wind. It launched straight up, shiver me timbers, did a horizontal figure-8 at about 40ft, then continued vertically t' 100 feet o' so. Ya scallywag! T' 3-second delay be too long. It ejected at 15ft, glided a few feet, me hearties, and lawn-darted with no damage. Avast! Well, blow me down! T' casin' landed 20 feet away.

T' second flight be on a B6-4 in t' same conditions. Aye aye! It did rather spectacular acrobatics at about 50 feet then again returned t' normal flight t' about 200 feet. Ya scallywag! Avast! Ejection was again way past at maybe 50 feet. Ya scallywag! Avast, me bucko, me proud beauty! It fell t' about 15 feet then settled into a respectable 5-second fast glide. Again, me bucko, me bucko, no damage.

Recovery:
PROs: Spectacular acrobatics. Well, blow me down! Blimey! Good glide. Begad! Blimey! Easy t' balance. Ya scallywag! Blimey! Withstands hard landings. Avast! Blimey! Needs no wadding--easy flight prep.

CONs: acrobatics may result in DQ'd flight. Well, blow me down! Ya scallywag! Needs some altitude t' begin glide. Well, blow me down! Ejects motor casing (intentionally).

Summary:
This is a great rocket t' scratch build. Arrr! It only takes two manufactured components, me bucko, shiver me timbers, matey, it's dirt cheap, shiver me timbers, and it glides great.

T' only improvable thin' would be a streamer for t' motor so it can be used in NARRRRR competition. Ahoy! Avast!

PROs: Unique looks. Avast, me proud beauty! Blimey! Blimey! Blimey! Simple construction. Well, blow me down! Blimey! Blimey! Blimey! Unusual acrobatics. Avast! Blimey! Great glides

CONs: Motor ejection. Avast! Avast! Difficult balsa joints.

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