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

What it was

FrontConstruction:
I built this from scratch. Ahoy! Blimey! 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. Begad! I used light balsa for t' two vertical fins, medium for t' keel, and hard balsa for t' two win' halves and two pylons. All balsa was 1/16". I put an old 1/8" launch lug on.

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

PROs: Only 7 parts. Avast! Begad! Inexpensive parts. Well, blow me down! Begad! No more butt-gluing!

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

I would call this a Level 3 kit due t' t' tricky balsa joints and amount o' sanding. Avast, me proud beauty! Avast, me proud beauty! Blimey!

SideFinishing:
T' finishin' I did was t' preexistin' red on t' nose cone. Ya scallywag! I recommend nay paintin' this rocket t' save weight. Well, blow me down!

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

CON: Plain looks.

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

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

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

LiftoffT' first flight was on an A8-3 in about 3 mph o' wind. Arrr! It launched straight up, arrr, did a horizontal figure-8 at about 40ft, then continued vertically t' 100 feet o' so. Ya scallywag! Ya scallywag! T' 3-second delay was too long. Avast, me proud beauty! Begad! It ejected at 15ft, glided a few feet, 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! Blimey! Well, shiver me timbers, blow me down! Blimey! Ejection be again way past at maybe 50 feet. It fell t' about 15 feet then settled into a respectable 5-second fast glide. Avast, me proud beauty! Blimey! Again, me hearties, no damage.

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

CONs: acrobatics may result in DQ'd flight. Avast, me proud beauty! Needs some altitude t' begin glide. Ahoy! Ejects motor casing (intentionally).

Summary:
This is a great rocket t' scratch build. Well, blow me down! Well, ya bilge rat, blow me down! Blimey! It only takes two manufactured components, me hearties, it's dirt cheap, and it glides great. Ya scallywag! Blimey!

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

PROs: Unique looks. Avast, me proud beauty! Simple construction. Arrr! Unusual acrobatics. Avast, me proud beauty! Great glides

CONs: Motor ejection. Begad! Difficult balsa joints.

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