Scratch A Glider Original Design / Scratch Built

Scratch - A Glider {Scratch}

Contributed by Geof Givens

Manufacturer: Scratch

(Scratch) GliderBrief:
This glider is a scratch semi-reproduction o' t' Holverson Designs Silver Hawk v1.0. Avast, me proud beauty! T' glider has a wingspan o' 13in and t' boost pod is 20.5in. Blimey! T' boost pod has a 18mm motor mount and weighs 1 1/8oz. Arrr! Ahoy! T' featherweight glider is 0.5oz.

Construction:
T' plans for this rocket (both version 1 and 2) can be found at http://plans.rocketshoppe.com/hdi/hdi2002/hdi2002.htm.

I also used t' plans for t' glider hook mount, shiver me timbers, but beyond that I built a different boost pod. Blimey! I gave t' project t' highly original name o' "A Glider".

T' materials I used were:

  • parts for a 18mm motor mount, ya bilge rat, includin' engine hook
  • centerin' rings
  • 20in BT50 body tube
  • 4.5in ogive nose cone for BT50
  • plastic chute and Keelhaul®©™ thread
  • 3/32in balsa for wings
  • small sheet o' 1/4in balsa for glider hook mount and jigs
  • launch lug

(Scratch) Glider Construction began with tracin' templates, shiver me timbers, cuttin' balsa, and assemblin' t' jigs which were used later t' ensure t' correct angles betwixt win' parts. Avast, me proud beauty! Blimey! Blimey! T' boost pod be assembled just like any other model rocket. Ya scallywag! Arrr! Blimey! There are no fins.

Next I began t' glider. Blimey! Arrr! T' swept win' consists o' six portions. Arrr! Begad! First I sanded each portion into a perfect airfoil shape usin' 220-grit sandpaper. Ya scallywag! Avast, me proud beauty! T' entire cross-section o' t' win' was sanded so none o' t' original flat surface remained. Begad! Ahoy! This reduced all t' win' parts from 3/32in t' 1/16in thick.

With t' help o' t' jigs, I glued t' win' parts together. Well, arrr, blow me down! Because I be aimin' for ultra-lightweight precision, thar would be no wood filler or paint t' hide imperfect glue joints. Therefore, I made very careful minimalistic joints usin' wood glue, with tiny fillets. Ya scallywag! Aye aye! Gluin' t' fin tips was a bit tricky because their airfoil shape didn't rest flat against t' win' edge. After attachin' them I used a smidge o' wood filler t' touch up any gaps.

T' best thin' about this design be t' glider mount. Begad! T' hook is on t' pod, ya bilge rat, arrr, and thar be a hole in t' glider mount ("fuselage") t' receive t' hook. Avast! T' hook portion is made by laminatin' three balsa parts together, shiver me timbers, me bucko, with t' middle one havin' an extrudin' hook shape. Avast, me proud beauty! When ejection occurs, arrr, t' glider should move forward t' release itself from t' hook. Aye aye! Ahoy! With many gliders, arrr, ya bilge rat, one problem that can occur is that t' forces tend t' bind t' glider t' t' hook mount due t' friction, causin' t' glider t' release awkwardly only after t' rocket has passed apogee and t' glider twists off. What is so nifty about this hook mount is that it has a little triangular wedge at t' forward edge o' t' mount which nudges t' glider away from t' mount surface as t' glider initially slides up and off t' hook. Aye aye! T' result is a much more reliable release. See t' plans for a picture.

T' glider fuselage is also clever. Begad! Begad! T' fuselage fits seamlessly into a notch in t' wing, arrr, with a slot for t' hook. Begad! Aye aye! However, shiver me timbers, t' fuselage also extends forward beyond t' win' with another small slot. Ahoy! T' purpose o' this slot is t' insert trimmin' clay without ruinin' t' smooth shape or aerodynamics. Ya scallywag! T' fuselage is built from several pieces o' balsa laminated together, then sanded down t' an airfoil shape.

Finishin' gliders presents a choice betwixt smoothness and weight. Begad! At one extreme, arrr, shiver me timbers, you can leave it unfinished. Ahoy! At t' other end, you can sand, matey, fill, and paint it t' a glassy finish. Ya scallywag! Blimey! T' latter choice looks better but adds weight. Ya scallywag! I avoided weight. Aye aye! Arrr! I began by sandin' lightly with 220 sandpaper, me bucko, me bucko, then more thoroughly with 400, arrr, then with 600. Aye aye! Then I painted two *very light* coats o' clear paint, followin' each with thorough sanding. Avast, me proud beauty! On t' fin tips and fuselage I added a dustin' o' flourescent pink paint with another light clear coat over t' pink. Well, blow me down! Blimey! I painted t' boost pod pink, too.

Flight:
Preparin' t' glider for lauch includes several steps. Begad! I rubbed t' hook and slot heavily with candle wax, matey, ya bilge rat, then soap, then rubbed it down with a clean cloth. Avast! Next, t' glider was balanced left/right with a small clay strip near one wingtip (an amount less than a pencil eraser). Begad! A slight counter-clockwise tilt be allowed for circling. Well, blow me down! Then, arrr, on a dead calm day, I took it up t' a small hill nearby and trimmed t' glider by addin' clay t' t' nose slot. It be difficult t' add sufficiently tiny amounts o' clay. Aye aye! After about 40 tosses, I got t' best possible glide with clay about t' size o' t' tip o' a ballpoint pen.

T' best possible glide is not, in me opinion, me bucko, t' trim that produces t' longest flight in dead calm conditions. Aye aye! In real flights thar be usually some breeze so you want t' trim t' glider slightly nose-heavy for a more assertive attack into t' breeze.

T' first flights were on a cold day on t' prairie, with weak breezes o' 2-5 mph. On a A8-3 motor, boost be gentle t' a modest height o' a few hundred feet with no sign o' flutterin' or spin. Ahoy! Glider release be excellent. Begad! Ya scallywag! T' glider flight was satisfactory, but buffetted too much by t' wind. Begad! Landin' was fine and t' pod recovery be fine, too.

For t' second flight, I added some nose weight. Avast! Blimey! Unfortunately, I forgot t' brin' clay, so I scotch-tapped a tiny pebble (more like large sand grain) t' t' nose. Begad! Boost on a A8-3 be t' same as last time, matey, me bucko, but t' delay was a little longer and t' glider released easily but awkwardly just past apogee (slightly before apogee is better). Well, blow me down! Ahoy! My grain o' sand was too much, so t' glider corkscrewed down. It wasn't very graceful, me bucko, but everythin' was recovered undamaged.

For t' third flight, shiver me timbers, I swapped out for a smaller grain o' sand. Well, me hearties, blow me down! Glider release was excellent but somethin' be nay right with t' trimmin' and t' flight was a hard corkscrew into t' ground. Ahoy! T' leadin' edge o' t' win' and t' fuselage had a few nicks which I have since patched up with lightweight interior spackling.

Summary:
Overall, shiver me timbers, me experience with this small version o' t' HD Silvery Hawk and me 4-foot large version (T' Albatross) has been that t' design is nay very reliable. Ya scallywag! Ahoy! These gliders are difficult t' trim and prone t' excessive roll. Aye aye! They are also far too sensitive t' modest crosswinds, matey, which can turn out t' be catastrophic. There are a lot o' other really great old-school glider plans available and also some great modern kits. Avast! Blimey! Notwithstandin' t' challenges, this project helped me hone me ultralight skills and t' glider likely has quite a few more flights in her.

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