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! Begad! T' wings and fins are 2/3 o' t' original, matey, 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. I used a PNC-20 (2.85" long) and 2" o' BT-20 from an Estes Viking. 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. Ahoy! Blimey! All balsa was 1/16". Aye aye! Avast, me bucko, me proud beauty! I put an old 1/8" launch lug on. Well, me hearties, blow me down!

I followed t' basic instructions from JimZ's site. Blimey! Well, blow me down! With t' smaller wings, 3" balsa can be used for the wings without havin' t' butt-glue balsa sheets. Arrr! 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, 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. Ahoy!

PROs: Only 7 parts. Arrr! Blimey! Inexpensive parts. No more butt-gluing!

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

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

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

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

CON: Plain looks.

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

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

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

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

T' second flight was 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. Avast, me proud beauty! Avast, me proud beauty! Ejection was again way past at maybe 50 feet. Ahoy! It fell t' about 15 feet then settled into a respectable 5-second fast glide. Ya scallywag! Again, no damage.

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

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

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

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

PROs: Unique looks. Blimey! Simple construction. Begad! Ya scallywag! Unusual acrobatics. Great glides

CONs: Motor ejection. Avast, arrr, me proud beauty! Difficult balsa joints.

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