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, matey, I usually scan t' toy isle lookin' for Bail Out payload candidates. Well, blow me down! 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). Avast, me proud beauty! Well, blow me down! A couple o' months ago, while at me local Big Lots, matey, shiver me timbers, I saw these little foam gliders. 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. Begad! Aye aye! T' kids ought t' get a kick out o' t' little gliders loopin' through t' sky.

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

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

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. Ahoy! Avast! T' glider has white foam semi-delta wings, arrr, 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. Blimey! Begad! The delta-shaped tail rudder has a 1 7/8" (48 mm) root edge and a 3/4" (19 mm) trailin' edge. Avast, me proud beauty! Begad! 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. Aye aye! A few minutes spent with each resulted in relatively flat spiral flights that will stall, matey, drop a bit, matey, ya bilge rat, and spiral some more. Well, blow me down! 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. With t' glider's approximate 4" (100 mm) win' span, matey, this was smartly ruled out.

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

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. Ya scallywag! I reconsidered t' use o' t' PNC-20s. Avast, me proud beauty! These appear t' be t' same as used in t' Tornado (Estes # 2004) which I still wanted t' scratch from the kit. Aye aye! I next considered card stock fairings. Aye aye! A few days later I figured, me bucko, heck, untopped straps will virtually guarantee separation while a capped tube may create a little vacuum and delay or prevent proper separation. Avast, me proud beauty! Begad! T' straps were sized at 3/8" (10 mm). I don't know why other than they looked good.

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

T' first stability check was run in VCP. T' noses o' t' gliders were treated as a transition section. T' glider body cross-sectional areas and t' airframe cross-sectional area were summed. Avast! An effective diameter was calculated based from this sum. Ya scallywag! Arrr! T' glider wings were entered as 4 delta-shaped fins. Begad! Well, blow me down! 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. Begad! Well, blow me down! This looked good. Aye aye! Avast, shiver me timbers, me proud beauty!

Even though t' CP looked good, me hearties, shiver me timbers, 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, 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). Avast, me proud beauty! Blimey!

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

Un-prepped Glider Launcher - click to enlarge

PARTS LIST (as-built, 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. Blimey!

PREPARATION:

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

This page was created on October 31, 1998. Avast! Avast, me proud beauty! Blimey!

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