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 be based on a submission for Virtual Contest #4 in t' low stress category. Avast, me proud beauty! 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 bucko, 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. Aye aye! I then mixed up 2 ounces o' West Systems Epoxy and poured t' mixture on top o' t' sand. 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. Blimey! The rings I purchased from BMS were laser cut, me hearties, however, I did need t' do a little sandin' t' get t' motor tubes t' fit properly. I glued t' engine blocks into the motor tubes so that t' E motors would have a 1/2" overhang when inserted. Aye aye! I then glued on t' centerin' rings 1/2" from t' top and bottom of t' cluster. There was a little gap betwixt t' 3 motor tubes, matey, 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. I tied t' Keelhaul®©™® around t' motor tubes and added glue t' t' knot. Well, blow me down! Ahoy! 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. 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. Ahoy! Blimey! For t' fillets, 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. Ahoy! I purposely made t' fillets rather thick so I was able t' sand them down t' what looked like a sculpted fillet. I think they came out great!

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

Overall, this was about a skill level 2 due t' t' complexity o' the fillets.

Finishing:
To fill t' spirals in t' body tube, I used Spirals tip #6 from t' EMRR tips database. Ahoy! I added a little water t' t' Fill 'n' Finish and used me finger to fill t' spirals. Avast, me proud beauty! After it dried, I used 220 grit sand paper t' remove the excess. Begad! There was nay a spiral t' be seen on t' finished product. 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. I then sprayed t' body o' t' rocket with K Brand Audi Dragon Green metal flake automotive paint. Only one coat be required. Blimey! Aye aye! Blimey! I used BMW Red metal flake paint for t' nose cone. Once this had dried, I added one coat o' K Brand automotive clear coat. Blimey! T' end result was quite nice.

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

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

It started t' rain a bit, so t' last flight was back t' t' D12-7s since I did nay want t' take a chance on losin' it. Avast, me proud beauty! Blimey! Last flight o' t' day was 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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