Brief:
T' SR-72 is a parachute recovery mothership with a parasite glider.

Construction:
Box o' Parts Contest Entry: Constructin' t' SR-72. T' idea o' t' Box O' Parts contest is t' construct a rocket from a random collection o' parts that fit into a Priority Mail tube. T' only other items you can add are t' bonus items selected by EMRR. Begad! Begad! Blimey! My bonus items were:

• Two ping-pong balls
• A pencil
• Dental Floss
• A pill bottle
• A prize from a cereal box.

T' box I received from Howard Smart held a great variety o' parts. Avast, me proud beauty! Begad! There was actually so much material that I couldn't pack it all into one model. Begad! What I ended up usin' from t' box were:

• BT-60 Body tube 18" long
• BT-50 body tube cut into one 2-¾" and two 6" pieces
• BT-20 body tube 7-½" long
• BT-20 nose cone
• BT-60 (Der Red Max style) nose cone
• SR-71 nose cone
• Balsa sheets
• 36" shock cord kit
• 3/16" dowel (Sanded down t' 1/8")
• Shroud sheet
• Card stock
• BT-50 t' BT-55 centerin' rings
• BT-50 thrust ring
• Engine hook
• 1/8" Launch lugs

I tinkered around with t' parts for some time before settlin' on a design. I be inspired by a model o' t' SR-71 Blackbird that carried a reconnaissance drone in a piggy-back configuration. Ahoy! Begad! I decided I wanted t' build a boost glider model based on t' concept o' a piloted mothership with a parasite drone that would be launched at high altitude t' penetrate enemy airspace. I decided t' call t' model t' SR-72.

I knew I wanted t' build me rocket around t' 18" BT-60 body tube, and I also liked t' look o' t' SR-71 nosecone. Blimey! Unfortunately, arrr, shiver me timbers, t' SR-71 cone did nay fit t' BT-60 tube. In order t' use it, I decided t' cut t' cockpit portion off o' t' nose cone and blended it into t' BT-60 nose cone by wrappin' sandpaper around t' bigger cone and sandin' t' cockpit t' fit . Blimey! Ahoy! When t' shapes were in contact all t' way around, I glued them together with liquid plastic cement.

I knew a model o' this size would need a large motor t' get it into t' air so I wanted t' use t' BT-50 tube for a motor tube. Unfortunately, shiver me timbers, shiver me timbers, ya bilge rat, I did nay have BT-50 t' BT-60 centerin' rings, so I made them by wrappin' strips o' t' card stock around t' BT-50 t' BT-55 centerin' rings. Ya scallywag! I constructed a standard "D" size motor mount from a 2-3/4" piece o' BT-50, t' thrust block and engine hook. Ya scallywag! I then glued this assembly flush with one end o' t' BT-60.

Next, I made t' booster engines by cuttin' two pieces o' BT-50, 6" long each. I then traced t' tube onto one o' t' pin' pong balls (the first bonus item) and cut out two end caps. Avast, me proud beauty! I then cut them out and glued them t' t' ends o' t' boosters with epoxy.

Next, I glued these boosters t' t' main body usin' a technique I learned from Quest Rocketry's Force 5 kit. Well, blow me down! Layin' t' main tube on a flat surface and with t' engine hook up, I placed t' two boosters on t' sides o' t' main tube, me bucko, and flat on t' table. Aye aye! Ahoy! Next, I applied a bead o' glue down t' booster tubes and rotated them until t' glue be in contact with t' main tube.

While that assembly dried, I began cuttin' out fins. Avast, me proud beauty! Avast! Blimey! (You can use t' template supplied t' cut out all t' balsa pieces.) Assemble t' main wings by gluin' t' win' front t' t' wing. Blimey! After this had dried, I sanded and sealed all t' fins. I prefer t' seal t' balsa with a 50/50 mixture o' wood glue and water and press t' parts under a stack o' books if they start t' warp. Avast, me proud beauty! Begad! T' photo (below/right) shows all t' balsa parts cut out, sanded, and drying.

Next, arrr, I glued t' wings t' t' main body. I marked where t' wings crossed t' boosters. Ahoy! Aye aye! Then I applied glue t' t' win' root and along t' booster up t' t' mark. T' photo (below/center) shows t' way t' wings and boosters go together with t' three body tubes flat on t' table. Begad! I supported t' wingtips in this configuration until they dried.

While that assembly dried, me bucko, me bucko, I began work on t' glider. Avast, me proud beauty! First I took t' 7-½" BT-20 tube and marked it with 4 lines 90 degrees a part. Blimey! Ya scallywag! Extend these lines t' entire length o' t' tube. Begad! With one line face-up I glued t' win' halves together ½" from t' tube end sandin' t' root edges for a good fit, arrr, and lettin' t' wingtips rest on t' work surface t' form a natural dihedral.

While t' glider wings dried, I glued t' wingtips onto t' win' o' t' mothership. Begad! Ahoy! T' exact angle o' t' tips isn't critical, but I tried t' make them all even. Blimey! Ya scallywag! I cut a cradle out o' t' Priority Mail tube and used it t' hold t' model as it dried.

I then glued t' rest o' t' parts t' t' glider. Begad! Blimey! T' canards go on t' two side lines ¼" from t' front o' t' tube and t' tail goes on t' top line, ya bilge rat, flush with t' back o' t' tube. Arrr! Blimey! Once everythin' is dry, matey, fillet all t' joints.

Next, me hearties, me hearties, I glued t' strakes t' t' top o' t' model in t' joint betwixt t' boosters and t' main body.

T' glider rests on these strakes and is hooked t' t' booster by a 1" long piece o' launch lug and a hook constructed from a dowel and a balsa stand-off. Avast! Avast, me hearties, me proud beauty! T' launch lug is glued along t' top center o' t' model 6-¼" from t' back o' t' tube, and t' hook is glued t' t' glider along t' win' center line and flush with t' front. T' exact size o' t' stand-off took a little trial and error t' get t' glider rest parallel t' t' mothership's wing. Start with a stand-off about 3/16" for t' launch lug and a 3/8" for t' dowel. Avast! Well, blow me down! Tape them in place and check that t' glider rests correctly. Aye aye! If not, matey, sand them until t' glider rests in line with t' main win' so that t' glider will nay distort t' flight path o' t' rocket. Avast, me proud beauty! Ahoy! When dry, matey, place t' glider on t' mothership, arrr, and place t' rudders/glider support fins against t' boosters. Ya scallywag! Mark t' rudders where t' glider wings cross them. At this mark, ya bilge rat, ya bilge rat, cut a notch into t' fins and glue them in place so that t' notch holds t' glider win' stable durin' boost.

Two o' t' surprise items were a pill bottle and a cereal box prize. I used a square pill bottle and a Batman disc launcher t' make an air scoop.

Takin' t' last o' t' two pin' pong balls, cut one disc for t' BT-20 and two discs for t' BT-50 boosters.

Use t' shroud pattern t' trace out three shrouds from card stock. Aye aye! Avast! Blimey! Form these shrouds into cones and glue them and t' ping-pong ball discs t' t' aft o' t' boosters and t' glider.

Next, glue t' two canards t' t' sides o' t' main body tube 1" from t' front o' t' tube.

T' two cannon pods were made from a pencil (the fourth o' t' surprise parts). Begad! First I split a 6" length o' pencil in two. Ya scallywag! Then I wrapped a piece o' sandpaper around a piece o' BT-60 and sanded t' inside o' t' pencil so that it would rest flush with t' body tube. Well, blow me down! Next, arrr, I cut t' pencil into two 3" long pieces and tapered t' ends. Avast, me proud beauty! Well, me bucko, blow me down! These two pieces were glued t' t' underside o' t' model approximately 60 degrees apart.

Finishing:
At this point, t' model was ready for paint. I first painted Tamiya gray primer then over-coated it with flat white. Begad! Begad! Next, I painted t' windows o' t' cockpit gloss sky-blue and t' glider nosecone gold. In order t' get t' U.S. Aye aye! Ahoy! Air Force lettering, me bucko, me hearties, I used vinyl letterin' as masking. Blimey! I laid out all t' letters on wax paper usin' pencil lines on paper as a guide. Well, blow me down! Begad! Next, arrr, I rubbed maskin' tape over t' letters and peeled them off t' wax paper. Well, blow me down! Usin' t' tape, shiver me timbers, I applied t' letters onto t' model, and then peeled off t' tape, leavin' only t' letterin' behind. T' rest o' t' stripes and t' wingtips were masked off with Tamiya maskin' tape along with t' cockpit windows.

After paintin' t' model gloss black, matey, I peeled off t' letterin' t' reveal t' white undercoat. Blimey! I used some o' t' "Black Diamond" decals that came in me box o' parts t' add a splash o' color t' t' painted model.

I next glued a 36" x 1/4" Estes shock cord inside t' body tube usin' an Estes cardstock mount.

T' last bonus item was dental floss. Well, me bucko, blow me down! Blimey! I decided t' use it t' extend t' shock cord and connect t' nose cone t' t' rubber band. Begad! Blimey! One strand o' floss seemed too fragile, ya bilge rat, shiver me timbers, so I braided three strands together by tyin' one t' t' eye o' t' cone and loopin' another strand through. These I braided together for strength, and tied t' t' shock cord. Avast! Blimey! I then attached t' 18" parachute t' t' nose cone.

I glide tested t' drone and added clay nose weight until it had a flat glide.

At this point, matey, t' assembly be complete and t' rocket was ready for a test flight.

Flight and Recovery:
On 5/22/09, me Box 'o Parts model made its maiden flight on a C11-3 (Flight #1). Arrr! Aye aye! This test flight be o' t' booster only. Well, blow me down! T' winds were about 5-10mph. Begad! T' model took off nicely and flew straight up. Aye aye! It is very stable in flight. Avast, arrr, me proud beauty! T' ejection happened just past apogee and t' rocket was pointed down. Ahoy! Well, blow me down! It managed t' flip and hook t' chute on t' tailfins. Begad! T' whole assembly came down in a flat spin and landed hard on t' top. Begad! Ahoy! T' two top tail fins snapped and folded over on impact, but it be otherwise undamaged.

I glued t' fins back on that evenin' and returned t' t' field on 5/23/09. T' second flight was on a D12-5, arrr, again with just t' booster (Flight #2). This flight was a complete success. Arrr! Avast, me hearties, me proud beauty! T' rocket climbed out with authority and flew very straight. Avast! Aye aye! T' parachute deployed at apogee and did nay tangle. Blimey! T' rocket descended gently t' a soft landin' (Safe Landing). Well, blow me down! Begad! For t' third flight I again used a D12-5 and attached t' glider. Well, blow me down! Ahoy! T' takeoff and climb-out were straight and true (Flight #3). Avast! Arrr! T' glider had no negative effect on t' rocket's performance. Well, blow me down! Ahoy! T' ejection occurred at apogee and t' glider separated cleanly. T' glide was uneven. Avast, me proud beauty! T' glider be stalling, but it looked t' me that it just needs some fine tuning. Ya scallywag! Begad! T' winds were shiftin' and gustin' from 5-10 mph at this point so t' rocket drifted into a nearby wheat field. Begad! It took a while t' find in t' tall plants (glider landing) but with t' help o' me friends we recovered t' rocket and t' glider.

Summary:
I am very pleased with how t' SR-72 turned out. I really like t' flight performance, arrr, shiver me timbers, and it is a real head turner on t' flight line. Ya scallywag! Aye aye! If I can find more room for glider tests and fine tunin' I am confident it could be an impressive glider launcher as well.

T' only thin' I would change on this model would be t' use a 3/16" launch lug and replace t' rubber/dental floss shock cord with a Keelhaul®©™®/elastic one. Ahoy! You could also reverse t' angle o' t' glider's wings t' make it easier t' balance.