Scratch Pushing the Envelope Original Design / Scratch Built

Scratch - Pushing the Envelope {Scratch}

Contributed by Brian Kain

Manufacturer: Scratch

 

Brief:
I wanted t' build a rocket with t' smallest fins I could get away with.....So I came up with this.

Rocket Pic

I used Rocsim, VCP and WRASP t' get me optimal size fin. Blimey! Oddly enough, most o' t' programs agreed with me rocket. This is a single stage rocket, with an interchangeable MMT. Arrr! Begad! Anythin' from 54mm down t' 24mm motors will push this little guy. Begad! It uses a PML 30" chute with t' shroud lines tied in a knot half way up...This speeds t' descent rate a little since t' chute is oversized. Ahoy! Ya scallywag! I use 20' o' tubular nylon I got from REI. Avast! Painted with automotive lacquer through an HVLP spray gun, me hearties, it came out very nice...I just wish I filled t' grooves better. Avast! It be kind o' spur o' t' moment paint job with no time t' prep, just primer and wet sand.

Construction:

  • 2 Phenolic Body tubes.
  • 3 G-10 1/16" fins
  • 3 1/8" birch CR's for MMT adapter
  • 2 2.1" coupler tubes
  • 1 LOC 2.1" nose cone
  • 1 Pair ACME 1/4" lugs for 2.1" airframe
  • 1 29mm 8" MMT (as an adaptor)
  • 20' o' tubular nylon
  • 2 3/16" stainless steel quick links for shock cord
  • 1 30" chute
  • 1 pair o' motherboard mountin' posts w/nuts and washers
  • 1 pair o' computer board retainers for motor retention

Rocket PicVery sturdy, even though it is nay a TTW rocket. Avast! Blimey! I just sliced mini fin slots in t' BT with an X-Acto blade about half way through t' airframe. Begad! Tacked t' fins on with CA t' make sure they are straight before committin' t' epoxy. Arrr! I applied generous fin fillets since it isn't TTW. Countersunk t' area where t' lugs went, me bucko, just about 1/3 o' t' way through t' airframe.

I always use 30 min epoxy, matey, though I have tried many different brands I used t' Devcon from TAP Plastics, me hearties, 2 ton 30 min epoxy.

I used a coupler t' attach t' shock cord lead t' by cuttin' slits in t' coupler and weavin' t' cord through it, tied it in a knot and epoxied over all that. Aye aye! Blimey! This is where t' 2 body tubes join together usin' t' coupler with t' shock cord lead. Well, blow me down! I tied t' upper half o' t' shock cord lead in an overhand knot, then epoxied over that... Begad! This is where I attach t' 20' o' TN with Quick Links sewn on each end.

Construction o' t' MMT is simple.... Avast, me proud beauty! First I drilled holes for t' retention hardware, matey, matey, then attached t' posts usin' washers and nuts. Avast, me proud beauty! I epoxied over those. Ya scallywag! I put t' CR's on t' motor tube and epoxied fillets on each CR. Ahoy! Then I applied a generous amount o' epoxy on t' CR's and in betwixt and slipped t' coupler tube over that. Aye aye! Blimey! I held t' MMT in me hands and turned it very smartly usin' centrifugal force t' spread t' epoxy inside.

Flight:
It can fly on small F motors usin' an elastic shock cord t' save weight. Blimey! T' rocket is designed without a permanent motor mount and therefore with a motor adapter I can use 24mm, matey, 29mm and 38mm motors with t' proper weight added t' t' nose. Arrr! Well, matey, blow me down! Blimey! I could even go for it without an adapter and try a 54mm motor. I would recommend F40-4 up t' J350-14 if it was glassed. Begad! I fly it most on 29mm G-64's for a nice flight. Aye aye! Blimey! I used a Nomex® chute protector from Pratt Hobbies. Aye aye! I used a tiny handful o' cellulose waddin' too. Ahoy! It flew exactly where it was pointed. Aye aye! T' wind did nay effect it at all. On t' 30" chute with t' shroud lines tied in a knot, arrr, ya bilge rat, it descended at a nice rate t' brin' it home safe on t' Black Rock Desert floor. Aye aye! I have flown this rocket quite a few times now.

Summary:
There are nay many con's t' point out so lets skip t' t' pro's. Cheap, simple, ya bilge rat, easy t' build and fun t' fly are some o' t' best I can think of..... Begad! Try it, I think you'll like it.

Other:
I think I learned from this rocket...... I will never build a rocket that is nay through t' wall again, most likely one that is nay glassed with some sort o' weight glass.

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