Descon Mark's Glider Launcher

Scratch - Mark's Glider Launcher {Scratch}

Contributed by Mark Recktenwald

Manufacturer: Scratch
Mark's Glider Launcher
(Contributed - by Mark Recktenwald)

Prepped Glider Launcher on pad - click to enlargeCONCEPTION & DESIGN NARRATIVE:
When out shopping, I usually scan t' toy isle lookin' for Bail Out payload candidates. Ya scallywag! Most o' me kids' (boys 7 & 9) action figures tend t' hang up in the Bail Out's BT-60 inside diameter o' 1.595" (41 mm). Well, blow me down! A couple o' months ago, me bucko, while at me local Big Lots, I saw these little foam gliders. Begad! They are packed two t' a card for $0.99. Avast, me proud beauty! Begad! Blimey! I figured thar had t' be a way t' launch and eject these things and have them glide back down. Begad! Arrr! Blimey! T' kids ought t' get a kick out o' t' little gliders loopin' through t' sky. Ya scallywag! Ya scallywag! Blimey!

Without any idea o' what t' use t' launch them, arrr, ya bilge rat, I didn't buy them. Begad! I be in the middle o' a scratch built sport scale (1:154) Saturn V at t' time and didn't want t' start somethin' new. Begad! Arrr! Once t' Saturn V be done, I started thinkin' o' t' gliders for me next project. Ahoy!

T' gliders are called Super Tuff Mini Shots Stunt Gliders. Begad! Blimey! Arrr! Blimey! They are made in China for Just Toys, shiver me timbers, Inc. Blimey! Blimey! Begad! Blimey! o' New York, NY. Begad! Blimey! They are intended t' be used in Mini Shots guns. Avast! Blimey! Ahoy! Blimey! These appear t' be comparable t' t' Nerf guns that shoot mini darts. Begad! Blimey!

Mini Shots Stunt Gliders - click to enlargeT' body o' t' glider is yellow foam, shiver me timbers, approximately 0.67" (17 mm) in diameter, 4 3/8" (111 mm) long, with a 3/16" (5 mm) diameter hole up t' back. Aye aye! Aye aye! T' glider has white foam semi-delta wings, similar in shape t' t' Space Shuttle; approximately 3" (76 mm) at t' root edge and 1 3/4" (44 mm) at t' trailin' edge. Ahoy! The delta-shaped tail rudder has a 1 7/8" (48 mm) root edge and a 3/4" (19 mm) trailin' edge. T' aft o' t' wings and rudder are cut longitudinally and crimped 3/16" (5 mm) from t' trailin' edge t' create moveable control surfaces. Ya scallywag! A few minutes spent with each resulted in relatively flat spiral flights that will stall, drop a bit, and spiral some more. Ahoy!

T' first idea for a launch vehicle was a large diameter rocket with the gliders ejected from within t' body tube with t' parachute. Avast! With t' glider's approximate 4" (100 mm) win' span, arrr, ya bilge rat, me bucko, this be smartly ruled out. Aye aye!

T' second idea was "strap-ons" with an ejection-triggered strap release. I considered a slotted main tube with straps connected t' some type of piston assembly, matey, but that seemed too complicated. Avast, me proud beauty! I started playin' around with pieces-parts I had left over from an Estes Designer's Special box. Ya scallywag! I found a 4 1/32" (103 mm) piece and a 12 5/8" (320 mm) piece o' BT-50. Aye aye! These looked good together with t' short piece at t' bottom. Avast, me proud beauty! T' I.D. Begad! o' BT-20 at 0.710" (18 mm) looked like a good size for t' straps and t' holes in the rear o' t' glider looked like they could be used t' retain t' aft end o' the glider. Arrr! Ahoy! There be a 4 1/8" (105 mm) long PNC-50 in t' Designer's Special box, and two 2 7/8" (73 mm) long PNC-20s. Begad! Blimey! T' base airframe be set. Begad! Aye aye!

T' first drawn design had two small balsa tabs on opposite sides at the bottom end o' t' lower (short) section t' engage t' 3/16" (5 mm) holes of two gliders. Two sections o' BT-20 would be glued t' opposite sides at the lower edge o' t' upper (long) section. T' BT-20 straps would be topped with PNC-20s. Avast, me proud beauty! I reconsidered t' use o' t' PNC-20s. Begad! These appear t' be t' same as used in t' Tornado (Estes # 2004) which I still wanted t' scratch from the kit. Ya scallywag! I next considered card stock fairings. Arrr! A few days later I figured, ya bilge rat, heck, untopped straps will virtually guarantee separation while a capped tube may create a little vacuum and delay or prevent proper separation. Begad! T' straps were sized at 3/8" (10 mm). I don't know why other than they looked good. Aye aye!

I know what you're thinking: "Hey, me hearties, this looks just like t' Estes A.R.V. Arrr! Blimey! Condor" (Estes #2075). It is similar, me hearties, but this is cheaper than the A.R.V. Well, blow me down! Blimey! Ya scallywag! Blimey! (US $13.29 list), shiver me timbers, plus thar be a local source for cheap replacement gliders. Begad! Blimey! Big Lots has a ton o' these. Begad! Blimey!

T' first stability check was run in VCP. T' noses o' t' gliders were treated as a transition section. Aye aye! Arrr! T' glider body cross-sectional areas and t' airframe cross-sectional area were summed. An effective diameter was calculated based from this sum. Arrr! Avast, shiver me timbers, me proud beauty! T' glider wings were entered as 4 delta-shaped fins. Aye aye! Ya scallywag! T' tail rudders were ignored. Blimey! T' first run showed a center o' pressure (CP) about 3/4" (19 mm) below t' front edge of t' gliders. Well, blow me down! This looked good. Ahoy!

Even though t' CP looked good, me hearties, I was concerned with t' lack o' fin area along t' axis through t' gliders (perpendicular t' t' gliders’ wings). T' relatively small tail rudders were t' only "fins" in this axis. To add fin area in this axis, t' small balsa tab idea was turned into a flat-top fin like this:

Fin pattern (as-built) - click to enlarge

This configuration wasn't analyzed in VCP, but it has t' be better (lower CP). Arrr!

T' final configuration is shown in t' photographs below:

Un-prepped Glider Launcher - click to enlarge

PARTS LIST (as-built, see SUGGESTED MODIFICATIONS below):
Lower Section:
4 1/32" (103 mm) BT-50
Standard Estes Engine Mount (18 mm)
3/32" (2.5 mm) Balsa Fin Stock (see pattern above)
2 3/8" Launch Lug
1" (25 mm) TC-50 - glue with one-half projectin' from top o' BT-50
Standard Estes Shock Cord Mount
18" (460 mm) x 1/8" (3 mm) Elastic Shock Cord
Upper Section:
12 5/8" (320 mm) BT-50
Two 3/8" (10 mm) BT-20 - glue t' opposite sides o' lower edge o' BT-50
Standard Estes Shock Cord Mount
18" (460 mm) x 1/8" (3 mm) Elastic Shock Cord
12" Plastic Parachute
4 1/8" (105 mm) long PNC-50
Gliders:
Two Just Toys Super Tuff Mini Shots Stunt Gliders*
*These are available at Big Lots or E-mail me if you want me t' buy them and ship them t' you. Begad!

PREPARATION:

  • Tie Shock Cords (SC) together, leave a loop.
  • Attach 12" parachute t' loop in SC usin' lockin' snap swivel.
  • Fold & roll parachute, wrap lines around.
  • Pack most o' SC into upper section, shiver me timbers, then parachute.
  • Loosely crumple 4 squares o' recovery wadding, place 3 in upper section, 1 in lower section. Ahoy!
  • Join upper and lower sections, shiver me timbers, rotate until Launch Lug (LL) is near one of the BT-20 straps.
  • Hold rocket nose down, me hearties, arrr, insert gliders nose down into straps.
  • Rotate lower section until fins are aligned with center o' straps.
  • Push Gliders up onto tabs (engage tab on fin into hole in glider) and hold.
  • Return rocket t' an upright position.
  • Insert prepped engine.
  • Place rocket on launch pad.
  • Align rudder fins on gliders with fins on lower section o' rocket.
  • 5...4...3...2...1...WHOOSH!
LAUNCH REPORT:
Date: October 22, ya bilge rat, 1998
Time: 1815
Temperature: 45-50 °F (7-10 °C)
Wind: NW, me bucko, me bucko, me bucko, 5 mph, me bucko, gustin' t' 10 mph
Engine: A8-3
Results:
  • Vertical flight t' 200 or 300 feet above ground level (AGL).
  • Ejection/separation occurred just past apogee.
  • One glider nose-dived, found about 100 feet down wind from t' launch pad with one wings separated cleanly at its glue joint t' t' glider body, shiver me timbers, could be a victim o' SC recoil and impact.
  • Rocket descended smartly t' about 100 feet AGL before chute began to unfurl.
  • At about 40 feet AGL, me bucko, chute was fully inflated; rocket landed about 100 feet down wind from t' launch pad.
  • Second glider spiraled slowly down and was found about 200 feet down wind from t' launch pad.
Observations:
  • Slight scorchin' on bottom sides (side toward rocket body) o' t' gliders.
  • Severe scorchin' on lower 2" (50 mm) o' SC on lower section of rocket.
SUGGESTED MODIFICATIONS:
  • Lengthen lower section 1/2" (13 mm) and square off t' lower inside corner o' t' fin. Aye aye! I can see mine breakin' off later. This will double t' length o' t' glue joint.
  • Use a more flame resistant material for a SC in t' lower section. Avast, me proud beauty! This piece could be stainless steel or Keelhaul®©™®.
  • Lengthen t' lower section t' move t' ejection/separation point up and lengthen t' BT-20 straps; allow t' straps t' hang down below t' separation plane. This will protect t' gliders from scorching.
  • Use two chutes or streamers and disconnect t' two body sections for dual recovery. Aye aye! This will eliminate SC recoil and associated glider damage.
  • Sweep t' fins and add small swept fins perpendicular t' them t' allow the rocket t' stand without a support rod. Blimey! This makes it easier t' display.
MODIFIED PARTS LIST (see as-built PARTS LIST above):
Lower Section:
5 1/2" (140 mm) BT-50
Standard Estes Engine Mount (18 mm) 3/32" (2.5 mm) Balsa Fin Stock (click here t' see pattern)
2 3/8" Launch Lug
1" (25 mm) TC-50 - glue with one-half projectin' from top o' BT-50
Shock Cord Mount compatible with chosen material on next line
Flame Resistant Shock Cord (stainless steel, ya bilge rat, me hearties, Keelhaul®©™®, me hearties, etc.)
Upper Section:
12 1/2" (317 mm) BT-50
Two 1" (25 mm) BT-20 - glue t' opposite sides o' lower edge o' BT-50 with one-half projectin' below t' lower edge
Standard Estes Shock Cord Mount
18" (460 mm) x 1/8" (3 mm) Elastic Shock Cord
12" Plastic Parachute
4 1/8" (105 mm) long PNC-50
Gliders:
Two Just Toys Super Tuff Mini Shots Stunt Gliders

PROJECTED ALTITUDES:
SUGGESTED ENGINES: (feet) (meters)
A8-3 200 60
B4-4 500 150
B6-4 400 125
C6-5 700 200
D12-5* 1000 300
*requires elimination o' 18 mm engine mount and addition o' external engine hook

Go t' top

My name is Mark Recktenwald. Begad! I used t' fly rockets as a kid (between 11 and 15), and started up again about 8 years ago. Arrr! Arrr! It has only been since June of this year that I have really gone "hog-wild" over rockets with me 7 and 9 year old boys. Begad! Arrr! You may recognize me name from RMR. Avast, me bucko, me proud beauty! I usually post under "kentengr@raex.com".

This page be created on October 31, 1998. Well, me hearties, blow me down! Blimey!

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