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! Ya scallywag! 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. Avast, me proud beauty! 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. Ya scallywag! Arrr! I used light balsa for t' two vertical fins, ya bilge rat, medium for t' keel, and hard balsa for t' two win' halves and two pylons. Arrr! Ya scallywag! All balsa be 1/16". Ahoy! Ahoy! I put an old 1/8" launch lug on. Well, blow me down! Avast, ya bilge rat, me proud beauty!

I followed t' basic instructions from JimZ's site. Begad! With t' smaller wings, 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, me hearties, 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. Ya scallywag! Avast, matey, me proud beauty!

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

CONs: Lots o' sanding. Avast! Parts must fit perfectly. Well, blow me down! Begad! Cut your own balsa.

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

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

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

CON: Plain looks.

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

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

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

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

T' second flight was on a B6-4 in t' same conditions. Well, blow me down! Begad! Blimey! It did rather spectacular acrobatics at about 50 feet then again returned t' normal flight t' about 200 feet. Arrr! Blimey! Ejection was again way past at maybe 50 feet. Avast, me proud beauty! Blimey! It fell t' about 15 feet then settled into a respectable 5-second fast glide. Begad! Blimey! Again, ya bilge rat, no damage.

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

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

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

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

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

CONs: Motor ejection. Ya scallywag! Blimey! Begad! Blimey! Difficult balsa joints.

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