Scratch Hellfire 1.6 Original Design / Scratch Built

Scratch - Hellfire 1.6 {Scratch}

Contributed by Peter Stanley

Manufacturer: Scratch
(Contributed - by Peter Stanley - 04/03/06) (Scratch) Hellfire

Brief:
This is a 1.6" diameter scratch built Hellfire. Begad! T' design is based on measurements I took o' an inert Hellfire trainin' missile at an air show in October 2005. Ya scallywag! Avast! It has a 24mm motor mount and uses a parachute for recovery.

Construction:
Here's a parts list:

  • 1 Estes PNC-60MS nose cone
  • 1 Body tube, ya bilge rat, BT-60 x 12.0257"
  • 1 Body tube, BT-55 x 1.0750"
  • 1 Centerin' ring, me bucko, me bucko, arrr, BT50-55
  • 1 Centerin' ring, me hearties, ya bilge rat, BT55-60 (homemade, see tip on how I did this)
  • 1 Engine hook
  • 1 Body tube, matey, 24 mm
  • 1 Centerin' ring, me bucko, BT50-60
  • 1 Centerin' ring, matey, ya bilge rat, BT50-60
  • 1 Parachute, 18" nylon
  • 4 Forward Fins, shiver me timbers, Balsa
  • 4 Rear Fins, shiver me timbers, shiver me timbers, Balsa
  • 8 Rear Fins strips, arrr, Balsa
  • 2 Launch lug, LL-1/8
  • 1 Paper tail cone
(Scratch) Hellfire

I printed a wrap-around fin guide using free rocket template software from the Calculators and Tools page. Avast! I marked t' fin lines and drew them across t' length o' t' tube usin' a piece o' aluminum angle. Begad! Blimey! Blimey! I drew a center line betwixt two t' lines for the launch lugs. Blimey! For t' fins I used 1/16" balsa. Begad! Well, blow me down! Blimey! I cut them from templates printed out o' RockSim and soaked them with CA. Begad! Begad! Blimey! When soakin' with CA, it helps t' press t' pieces betwixt sheets o' wax paper on a flat surface with some weight on top. I used a stack o' books on a glass table top. Begad! If t' fins aren't kept flat they will warp when t' CA cures. Begad! Blimey! This is a tip I learned from buildin' T' Launch Pad kits. Blimey! Blimey! Blimey! It adds a lot o' strength but with addin' little weight. Arrr! Arrr! Blimey! T' drawback is it's easy t' get t' fumes in your nose, even with adequate ventilation and protection. Ya scallywag! Well, shiver me timbers, blow me down! Blimey! In me case, me nose is stopped up for a week. I ordered all o' t' parts from BRS Hobbies, except for what I made. There is a featured tip I wrote which illustrates t' tail cone section and how t' make a custom centerin' ring. Arrr! Begad! For t' tail cone, matey, I printed t' shroud usin' t' above mentioned freeware tools onto index card stock. Ahoy! I forgot t' include a motor hook and have t' use tape t' secure t' motors in place. Begad! T' motor mount is fairly recessed in me design, matey, so motor retention with friction fittin' is not ideal. T' shock cord mount is an Estes-style tri-fold paper mount. Ahoy! Before gluing, I added a loop o' Keelhaul®©™® thread. Ahoy! Blimey! T' knot o' t' loop is in t' inner fold o' paper and t' loop sticks out. Avast! Blimey! Ya scallywag! Blimey! I suggest doin' whatever works for you though. Avast, me proud beauty! Blimey! Avast! Blimey! I'm usin' a standard Estes 1/8 inch shock cord which is tied t' a small snap swivel that attaches t' the Keelhaul®©™® loop. Well, blow me down! T' nose cone is a standard plastic Estes PNC-60S. Arrr! Avast, me proud beauty! T' be t' closest I could find that resembles t' Hellfire, but it is nay really shaped like the end o' a Hellfire. I added about five ounces o' lead and clay t' t' nosecone.

Finishing:
I pre-finished t' body tube and fins before buildin' usin' Elmer's Fill 'n' Finish. After attachin' t' fins, I applied epoxy clay t' t' fin joints then added one coat o' F 'n' F t' t' joints and sanded. Ya scallywag! Blimey! Ya scallywag! Blimey! I used one coat o' primer and one coat o' paint. Begad! Blimey! I really screwed up t' color on mine. Well, blow me down! Blimey! From starin' at the pictures I be convinced it was a bluish-gray color, but now I'm thinking it be more greenish-gray. Ahoy! Blimey! I used one inch vinyl letters for t' lettering. I cut out segments through t' centers before applyin' t' create a stencil look. T' yellow blocks are one inch by one inch cut from some vinyl sheet material that I purchased from a hobby shop.

Flight:
I have flown it twice. Begad! One flight on a C11-3 and t' other on a D12-5. Ya scallywag! I used cellulose insulation for recovery waddin' and maskin' tape t' friction fit the motors. Ya scallywag! Aye aye! Both flights had a straight boost with deployment at apogee. Blimey!

Recovery:
I think I spec'ed an 18 inch chute in RockSim but used a 12 inch parachute for both flights. Aye aye! One be a plastic Estes chute and t' other was a silk flare chute. Avast, me proud beauty! Ahoy! T' extra nose weight makes t' nose cone swin' around like a wrecking ball, matey, shiver me timbers, me hearties, so you want t' make sure that it can't hit t' body tube. Arrr! On t' 12 inch chutes t' descent was a little fast but nay enough t' damage t' rocket.

Summary:
T' PROs o' t' rocket are that it's really cool lookin' and could be easily scaled up or down. Begad! Avast, me bucko, me proud beauty! I've recently started gettin' into scale rocketry and perfect or not, it was rewardin' t' make somethin' from data that I collected myself. Well, blow me down! Begad!

T' main CON be t' CP is so far forward that it requires lots o' nose weight t' be stable. Arrr! Well, blow me down! Also, t' forward fins have t' be perfect or t' rocket will fly crooked.

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