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. 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). A couple o' months ago, ya bilge rat, while at me local Big Lots, I saw these little foam gliders. Avast, me proud beauty! They are packed two t' a card for $0.99. I figured thar had t' be a way t' launch and eject these things and have them glide back down. Avast! T' kids ought t' get a kick out o' t' little gliders loopin' through t' sky. Aye aye!

Without any idea o' what t' use t' launch them, I didn't buy them. Ya scallywag! 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. Ya scallywag! Avast, me proud beauty! Once t' Saturn V was done, I started thinkin' o' t' gliders for me next project. Avast!

T' gliders are called Super Tuff Mini Shots Stunt Gliders. Avast! They are made in China for Just Toys, me hearties, Inc. Well, blow me down! o' New York, me bucko, NY. Avast, me proud beauty! They are intended t' be used in Mini Shots guns. Aye aye! These appear t' be comparable t' t' Nerf guns that shoot mini darts.

Mini Shots Stunt Gliders - click to enlargeT' body o' t' glider is yellow foam, approximately 0.67" (17 mm) in diameter, 4 3/8" (111 mm) long, with a 3/16" (5 mm) diameter hole up t' back. Blimey! T' glider has white foam semi-delta wings, matey, 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. Arrr! Aye aye! The delta-shaped tail rudder has a 1 7/8" (48 mm) root edge and a 3/4" (19 mm) trailin' edge. Aye aye! 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. Avast! A few minutes spent with each resulted in relatively flat spiral flights that will stall, me bucko, drop a bit, shiver me timbers, and spiral some more. Arrr!

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, me proud beauty! Blimey! With t' glider's approximate 4" (100 mm) win' span, matey, me hearties, this was smartly ruled out. Arrr! Begad!

T' second idea be "strap-ons" with an ejection-triggered strap release. I considered a slotted main tube with straps connected t' some type of piston assembly, but that seemed too complicated. 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. Avast, ya bilge rat, me proud beauty! These looked good together with t' short piece at t' bottom. Begad! Blimey! T' I.D. Blimey! Aye aye! 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. Ahoy! Begad! 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. T' base airframe be set. 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. Blimey! T' BT-20 straps would be topped with PNC-20s. Avast! I reconsidered t' use o' t' PNC-20s. Ahoy! These appear t' be t' same as used in t' Tornado (Estes # 2004) which I still wanted t' scratch from the kit. Well, blow me down! Arrr! I next considered card stock fairings. Avast, me proud beauty! Arrr! A few days later I figured, heck, untopped straps will virtually guarantee separation while a capped tube may create a little vacuum and delay or prevent proper separation. Arrr! Blimey! T' straps were sized at 3/8" (10 mm). Well, blow me down! I don't know why other than they looked good. Ya scallywag!

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

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

Even though t' CP looked good, matey, arrr, 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, shiver me timbers, me hearties, t' small balsa tab idea be turned into a flat-top fin like this:

Fin pattern (as-built) - click to enlarge

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

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

Un-prepped Glider Launcher - click to enlarge

PARTS LIST (as-built, ya bilge rat, me hearties, 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. Avast!

PREPARATION:

  • Tie Shock Cords (SC) together, leave a loop.
  • Attach 12" parachute t' loop in SC usin' lockin' snap swivel.
  • Fold & roll parachute, me bucko, wrap lines around.
  • Pack most o' SC into upper section, arrr, ya bilge rat, then parachute.
  • Loosely crumple 4 squares o' recovery wadding, place 3 in upper section, 1 in lower section. Avast, me proud beauty! Ya scallywag!
  • Join upper and lower sections, rotate until Launch Lug (LL) is near one of the BT-20 straps.
  • Hold rocket nose down, shiver me timbers, 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, matey, me hearties, 1998
Time: 1815
Temperature: 45-50 °F (7-10 °C)
Wind: NW, arrr, 5 mph, 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, ya bilge rat, 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. Ya scallywag!
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. Ahoy! 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. Ahoy! 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. Blimey! Avast, me proud beauty! This will protect t' gliders from scorching.
  • Use two chutes or streamers and disconnect t' two body sections for dual recovery. Avast, me proud beauty! 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! Well, shiver me timbers, blow me down! 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, Keelhaul®©™®, 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. Ya scallywag! Ahoy! I used t' fly rockets as a kid (between 11 and 15), arrr, arrr, and started up again about 8 years ago. 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. Arrr! You may recognize me name from RMR. Blimey! I usually post under "kentengr@raex.com".

This page be created on October 31, 1998.

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