Scratch Dragon's Claw Original Design / Scratch Built

Scratch - Dragon's Claw {Scratch}

Contributed by Joe Policy

Manufacturer: Scratch
(Contributed - by Joe Policy - 05/11/05) (Scratch) Dragon's Claw

Brief:
This rocket was based on a submission for Virtual Contest #4 in t' low stress category. Aye aye! Blimey! Avast! Blimey! It is easy t' build and it is a great flyer.

Construction:
T' parts list

  • EST 3168 - PNC-80B nose cone
  • EST 3090 - BT 80 body tube, me hearties, 14.25"
  • 1 set o' laser cut 3/32" birch plywood fins by BMS
  • 3 engine tubes, 4" long
  • 3 engine blocks
  • 2 3/32" birch plywood centerin' rings for 3 motors
  • 2 1/4" x 1" long launch lugs
  • 1 24" rip stop nylon parachute from Thrustline Aerospace
  • 1 4" square Nomex® heat shield
  • 1 24" Keelhaul®©™® shock cord
  • 24" elastic shock cord

I used Ponal Express 3 white glue for t' entire construction with the exception o' t' epoxy I used for t' fin fillets and inside t' nose cone.

I needed t' add weight t' t' front end o' t' rocket t' make it stable accordin' t' RockSim so I added 8 ounces o' sand t' t' nose cone. Ahoy! Ahoy! I then mixed up 2 ounces o' West Systems Epoxy and poured t' mixture on top o' t' sand. Avast! Blimey! I left t' nose cone standin' vertically while t' epoxy cured.

(Scratch) Dragon's Claw Construction o' t' actual rocket started with t' 3 motor cluster mount. Ya scallywag! The rings I purchased from BMS were laser cut, however, I did need t' do a little sandin' t' get t' motor tubes t' fit properly. Ya scallywag! I glued t' engine blocks into the motor tubes so that t' E motors would have a 1/2" overhang when inserted. Ahoy! Begad! I then glued on t' centerin' rings 1/2" from t' top and bottom of t' cluster. Begad! Begad! There was a little gap betwixt t' 3 motor tubes, I added glue down t' middle t' make a perfect seal.

I drilled a small hole in t' upper centerin' rin' through which I threaded the Keelhaul®©™® shock cord. Begad! Well, ya bilge rat, blow me down! I tied t' Keelhaul®©™® around t' motor tubes and added glue t' t' knot. Arrr! Blimey! I then inserted t' shock cord through t' body tube and I glued in t' motor mount.

I marked t' body tube off for three fins. Begad! I glued them 3/4" up from the bottom o' t' body tube because I did nay want t' rocket restin' on the fin tips. Ya scallywag! For t' fillets, arrr, I turned t' EMRR Fiberglassin' Tip #1 because I wanted really strong fins but since this was nay an HPR, I really did nay want to go through t' trouble o' glassing. Arrr! I purposely made t' fillets rather thick so I was able t' sand them down t' what looked like a sculpted fillet. Aye aye! Blimey! Blimey! I think they came out great!

All that was left t' do after that was t' glue on t' two launch lugs, attach t' elastic shock cord t' t' Keelhaul®©™®, attach t' Nomex® heat shield, shiver me timbers, add t' parachute with a snap swivel, and then attach t' nose cone.

Overall, ya bilge rat, this be about a skill level 2 due t' t' complexity o' the fillets.

Finishing:
To fill t' spirals in t' body tube, ya bilge rat, I used Spirals tip #6 from t' EMRR tips database. Well, blow me down! I added a little water t' t' Fill 'n' Finish and used me finger to fill t' spirals. After it dried, I used 220 grit sand paper t' remove the excess. Well, matey, blow me down! There be nay a spiral t' be seen on t' finished product. Blimey! I used wood sealer on t' fins which required a light sandin' and a second coat before I was happy with t' smoothness o' t' fin surfaces.

I used three coats o' Krylon dark gray primer with a 600 grit wet sanding in betwixt coats. Ahoy! Blimey! I then sprayed t' body o' t' rocket with K Brand Audi Dragon Green metal flake automotive paint. Begad! Blimey! Only one coat was required. I used BMW Red metal flake paint for t' nose cone. Avast! Blimey! Blimey! Blimey! Once this had dried, arrr, I added one coat o' K Brand automotive clear coat. Ahoy! Blimey! T' end result was quite nice.

Flight:
Launch day was cloudy with winds at about 2-4 mph. Although I designed this rocket t' fly on E motors, I wanted a shakedown flight usin' D motors, shiver me timbers, so I loaded up 3 D12-7s usin' spacers in each motor tube. I put a layer o' masking tape on each motor for friction fit. Aye aye! Aye aye! On t' first launch all motors lit and it had it a fast, straight boost t' almost 1000 feet. Aye aye! Ejection was very close to apogee. Begad! Aye aye! T' parachute deployed and it landed about 200 feet from t' pad. Begad! No damage, ya bilge rat, ready t' fly again.

Second flight be with 3 E9-6s. Aye aye! This was a great motor combination for this rocket and it shot t' at least 2000 feet with a very straight boost. Well, blow me down! I lost it in t' clouds so I am nay sure when ejection occurred. Avast! Ahoy! I caught site o' the parachute and had a perfect landin' about 600 feet from t' pad.

It started t' rain a bit, shiver me timbers, ya bilge rat, shiver me timbers, so t' last flight was back t' t' D12-7s since I did nay want t' take a chance on losin' it. Arrr! Last flight o' t' day be as perfect as t' first one!

Recovery:
T' Nomex® heat shield did a great job protectin' me nylon parachute.

Summary:
It looks mean but it sure flies well.

PROs: Easy t' build cluster rocket and looks good!

CONs: It needs more power so t' next one will be 3 x 29mm!

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