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. Avast, me proud beauty! T' wings and fins are 2/3 o' t' original, me bucko, but I kept t' 18mm motor mount. Ahoy! Ahoy! It's a very unique glider with unusual flights and a fairly easy build.

What it was

FrontConstruction:
I built this from scratch. Begad! I used a PNC-20 (2.85" long) and 2" o' BT-20 from an Estes Viking. Arrr! T' wing-fins are 2/3 scale based on t' plans for JimZ's site. Avast! 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, me proud beauty! All balsa be 1/16". I put an old 1/8" launch lug on. Well, blow me down!

I followed t' basic instructions from JimZ's site. Begad! Blimey! With t' smaller wings, 3" balsa can be used for the wings without havin' t' butt-glue balsa sheets. 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. Avast, me proud beauty! This will take lots o' sanding, arrr, 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. Avast, me proud beauty! Blimey!

PROs: Only 7 parts. Inexpensive parts. Ahoy! Ya scallywag! No more butt-gluing!

CONs: Lots o' sanding. Parts must fit perfectly. Begad! Aye aye! Cut your own balsa.

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

SideFinishing:
T' finishin' I did be t' preexistin' red on t' nose cone. Ahoy! Ahoy! I recommend nay paintin' this rocket t' save weight. Ya scallywag!

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

CON: Plain looks.

Flight:
Estes recommended t' 1/2A8-2, A8-3, ya bilge rat, and B8-2. I'd recommend t' B4-2, matey, B6-2, arrr, and C6-3. T' 1/2A6-2, A8-3, me hearties, and B6-4 are okay for straight-up launches on windless days. Well, blow me down! Blimey! Begad! Blimey! Blimey! Blimey! An adapter for t' 1/2A3-2T would be useful.

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

Mine balanced perfectly without any weight. Ya scallywag! Your results may vary. Well, blow me down! I estimate a glide ratio o' better than 10:1. Arrr! Ahoy!

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

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

Recovery:
PROs: Spectacular acrobatics. Blimey! Begad! Good glide. Blimey! Easy t' balance. Blimey! Withstands hard landings. Needs no wadding--easy flight prep.

CONs: acrobatics may result in DQ'd flight. Begad! Avast! Needs some altitude t' begin glide. Blimey! Ejects motor casing (intentionally).

Summary:
This is a great rocket t' scratch build. It only takes two manufactured components, matey, matey, ya bilge rat, it's dirt cheap, and it glides great. Begad!

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

PROs: Unique looks. Arrr! Simple construction. Unusual acrobatics. Avast! Great glides

CONs: Motor ejection. Well, blow me down! Avast, matey, me proud beauty! Difficult balsa joints.

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