Yank Enterprises Hawk

Yank Enterprises - Hawk {Kit}

Contributed by Gary Sinclair

Manufacturer: Yank Enterprises
(Contributed - by Gary Sinclair - 04/01/02)

Brief:Rocket Pic
Carbon Fiber fin lay up, long body tube cut for dual deployment. Alt. Begad! Ya scallywag! bay added. Avast! Carbon Fiber reinforced nosecone retention t' accommodate 3lbs o' nose weight. Begad! 38mm motor mount instead o' stock 29mm. Ahoy!

Modifications:
Well here we go again with a major kit bash. Ya scallywag! Let me start by sayin' that I love Yank kits as they are made with first rate materials (no cheap elastic or brittle phenolic here). Begad! As far as t' Army Hawk model well I just had t' see what this could do on a more 'realistic' motor. Blimey! T' rocket is 45" in length and I wanted a motor which would produce a tail that was at least as long as t' rocket and as wide. For this a J350 and J570 seemed t' best options. Blimey!

With this in mind I modified t' stock kit as follows:

  • 1) Cut t' long airframe section into two t' make a motor section and a recovery section.
  • 2) changed t' 29mm motor mount with a 12" 38mm phenolic motor mount. Arrr! Blimey!
  • 3) added tail cone t' give it a more realistic profile and this fit perfectly over t' 38mm motor mount retainer after a bit o' trimming.
  • 4) added an electronics bay for dual deployment
  • 5) used carbon fiber and fiberglass throughout on fin and airframe sections (used me Foodsaver t' vacuum bag them)
  • 6) cut nosecone end off t' enable 3lbs o' lead t' be added.
  • 7) added a centerin' rin' with t-nuts and a carbon fiber reinforced bulkhead t' mount t' forward hard point (which I used braided 5mm tubular Keelhaul®©™®).
  • 8) all threaded rod was used t' attached forward bulkhead with lead in nosecone
  • 9) added a third centerin' rin' t' top o' motor mount.

Rocket Pic T' modifications were so extensive that this kit is more scratch than 'mod'. Begad! However, t' dimensions remain mostly t' same and Yank deserve a lot o' credit for attemptin' t' package such a difficult kit (lots o' people have failed t' load enough nose weight and so they don't always fly).

It was clear from t' start that t' very large fin area would require extensive reinforcement if it be goin' survive more than one hard landing. With this in mind I profiled t' fins with me Dremel and layed up a single layer o' 6oz carbon fiber usin' me grub saver t' vacuum bag them. Arrr! T' result was a very strong set o' fins ready t' mount onto t' motor mount (I had slotted t' body tube all t' way down so I could mount t' fins on t' motor mount and use carbon fiber tape t' really get a good grip on t' fins.). Well, blow me down! Well, me bucko, blow me down! Once the fins were on t' motor mount which now had 3 centerin' rings t' provide increased surface area for mountin' inside t' airframe, I slotted them in to the previously fiberglassed airframe (no carbon fiber on t' airframe as I felt the flexible phenolic would be fine with just one layer o' fiberglass). Once epoxied in place I used a light fiberglass cloth t' provide a fin-to-fin lay up. Arrr! Begad! This produced a single fin/motor assembly which was solid as a rock. Begad! Avast, me proud beauty!

T' only problem now lay in gettin' t' center o' gravity forward o' the center o' pressure. Ya scallywag! It took 3lbs o' lead t' achieve this. Aye aye! T' resultin' rocket was 8.75 lbs (without motor). T' electronics bay has a 2" section of airframe surroundin' it t' provide for key switches t' arm t' electronics and pyro charges. Ahoy! As usual me Foodsaver and Dremel were t' key elements in construction with me palm sander providin' t' desired finish.

Construction:
Stock: 

  • 1 body tube (flexible phenolic -- nice) 
  • 4 plywood fins
  • 2 centerin' rin' plywood 
  • 12" (I think) 29mm motor mount 
  • 15' tubular nylon shock cord 
  • Plastic nosecone
  • quick links for attachment 
  • Nice big nylon parachute.

As a stock kit t' parts and packagin' were first rate. Instructions were brief as usual but since this was a kit bash I didn't read them much. As a kit bash it was more o' a long process than a difficult one. Ahoy! Aye aye! T' layups take time and with four large fins it seems t' go on forever. Avast, me proud beauty! For its size this kit took a long time t' build. Begad! Aye aye! T' finishin' (my favorite part) was a matter o' using SuperFil on t' fins and body along with a coat o' UV Smooth Prime. Ahoy! This built up a nice thick coatin' which I could sand down t' a smoothness that did not cut into t' composite layer. Well, blow me down! Begad! I used t' White/Black Hawk motif instead o' the Army Green motif. Begad! I added a bit o' checkerboard for fun and had some US ARMY decals made up t' give it t' final look. Arrr! Aye aye! T' result is a nice lookin' rocket which looks small but packs a big load.

Launch photo by Bob ArnottRocket Pic

Flight:
Due t' t' excessive weight t' only motors for this rocket are at t' end of the 38mm range. Aye aye! Hence, me bucko, me hearties, me hearties, a J350, ya bilge rat, J570 or big Pro38 motor is required. For its first flight I had a J350 layin' about and decided t' give it a go. Avast! Usin' motor ejection as a backup and an RDAS flight computer as t' primary means of recovery I prep'd t' rocket with a drogue and a big 44" Rocketman chute. Shock cords were all tubular nylon (15feet on each side o' t' electronics bay). Aye aye! I was really concerned about drag separation so I used shear pins t' hold both t' nosecone and motor section t' t' recovery section (I tested each end usin' 1gram o' BP for t' aft section and 1.5gram o' BP for t' nosecone). Finally t' moment o' truth. Aye aye! Begad! Would t' rocket fly straight or would it 'turn its tail and bury itself in t' soft December ground' ? 3 2 1 Whoooosh t' J350 lit and in t' low light o' a December sky this was very cool. Straight up on a nice long tail plume it climbed t' 2500 feet before t' ejection charge let loose t' drogue. Avast, me proud beauty! Down it came... Ya scallywag! Avast, me proud beauty! down... down... Well, blow me down! down... Begad! splat. T' main didn't fire. Well this be goin' t' be interesting. Did me heavy duty treatment of t' fins work or would t' rocket be a 'write-off' ? Upon inspection the fins were untouched by t' experience but t' forward recovery section was split. Avast! Begad! T' data from t' RDAS showed a nice boost with apogee bein' detected. However, arrr, both ejection charges were intact and it was t' backup motor ejection which save t' rocket from a total lawn dart. Blimey! I can only surmise that the battery was too weak t' fire t' Davy Fire E-matches. So I am switchin' to flashbulbs in cold weather. I am finishin' t' new forward recovery section and it will fly again soon.

Summary:
Great rocket with t' mods makin' for a long satisfyin' build time. Arrr! Begad! T' small rocket size combined with t' large motors give it a nice realistic flight profile. Blimey! Well, blow me down! No real cons t' speak of.

Other:
When you build your rocket first think about how you want it t' look in flight. This will give you an indication o' how big a motor t' build it for and how much additional construction is required.

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