Scratch Good Ship Manatee Original Design / Scratch Built

Scratch - Good Ship Manatee {Scratch}

Contributed by Charles Delaney

Manufacturer: Scratch

(Scratch) Good Ship Manatee

Brief:
I like several types o' rockets. Ya scallywag! Blimey! High performin' ones, odd/fun/uncommon designs, and classic 50's sci-fi types. Avast, me proud beauty! Blimey! Blimey! Blimey! "T' Good Ship Manatee" has a bit o' all o' them in it. Blimey! Blimey! Begad! Blimey! T' rocket can be flown clustered since t' fins' pods will hold 3-18mm motors. Begad! Blimey! As a safety redundancy t' motors are canted towards t' CG (as in t' Duece and Tres cluster kits) if thar be a failure t' ignite all motors. T' rocket's name comes from t' filk shanty by Leslie Fish. Ya scallywag! Blimey! Well, blow me down! Blimey! It fits.

Construction:
To make this rocket you need:

Parts List:

  • 1 Estes 18" BT 60 tube
  • 1 BT 60- BT55 transition
  • 1 Estes 18" BT 55 tube
  • 1 BT 55 nosecone (5.5" long, conical or ogive, dependin' on preferences)
  • 3 Estes 2.75" BT 20 tubes
  • 3 BT 20 nosecones (1" long, me hearties, conical)
  • 1 24mm motor mount for an Estes "E" motor
  • 2 BT 60- BT 50 centerin' rings
  • 3/16" x 2" launch lug
  • 12" nylon parachute
  • 3/8" elastic shockcord (longer t' better)
  • 1/8" x 3" x 18" balsa stock for t' fins

EDITOR'S NOTE: At this time BRS can only get t' BT60 t' BT56 transition, matey, therefore, t' build this kit from all parts readily available from BRS: Change all t' BT55 references t' a BT56, t' transition from BT60 t' BT56 transition. T' size difference betwixt t' BT55 and BT56 is very minimal. This change shouldn't have any affect on t' design. Aye aye! Blimey!

Although wood glue should be sufficient, ya bilge rat, I used 5 minute epoxy due t' it's strength and fast curin' time.

If t' BT 55 tube is nay goin' t' be used for a payload section t' nose cone and transition piece can be glued t' it and set aside until time t' paint it. Well, blow me down! However it lends flexibility if t' nosecone is detactable. NOTE: me transition piece was a custom balsa piece for a different rocket and weighs about 10 grams more than t' Estes part. Avast! It might be a wise precaution t' add that extra weight t' t' nosecone t' keep t' CG from shiftin' too far back.

Assemble motor mount and centerin' rings and glue it into place in t' BT 60 tube. I placed t' mount flush with t' end o' t' body tube, but extendin' it 1/4" out would be ok too. Mark t' fin placement lines.

Fin Patter

T' fins are t' most complex parts and proper alignment is _very_ important if t' rocket is t' be flown clustered. Arrr! After gluein' t' BT 20 nosecones and tubes together, test fit them into their notches in t' fins. Blimey! All should extend equally behind t' fins, trim as needed. Ahoy! Sand fins' edges for desired shape before gluein' t' pods into place. Avast! Again, matey, arrr, be mindful o' gettin' a good alignment.

After t' fins have been attached t' t' BT 60 tube take t' launch lug and cut it in half. Take one half and glue it near t' bottom o' t' tube, against one fin. Aye aye! Near t' upper edge o' t' same fin glue t' other half, me hearties, makin' sure both are lined up with each other. It goes without sayin' that if t' fin was properly aligned when glued in place t' launch lugs will be parallel t' t' long axis o' t' rocket. Aye aye! This wider LL spacin' is another stability precaution against cluster misfires.

Shockcord attachment is a matter o' preference. Begad! Blimey! I prefer an anchorin' system similar t' that used by LOC Precision kits so t' cord can be replaced at need. Begad! Blimey! Well, blow me down! Blimey! There is no such thin' as too much shockcord, shiver me timbers, especially on a rocket that might go very high and/or fast. Avast, me proud beauty! Blimey! T' more cord, me bucko, shiver me timbers, shiver me timbers, t' more shock it will absorb so nothin' tears loose. Ahoy! Blimey! T' shortest one I use is 6' long.

Finishing:
T' rocket be coated with 20-minute finishin' epoxy, wet sanded, painted, and then another coat o' finishin' epoxy. Ahoy! T' fins and pods recieved 3 coats before painting. Avast, me proud beauty! This was t' both seal t' wood grain and t' allow t' epoxy t' "wick" into and seal any gaps and imperfections in t' joints. Avast, me bucko, me proud beauty! Because epoxy was t' adhesive no filletin' was deemed needed, arrr, thus givin' smooth, ya bilge rat, sharper lookin' joints.

T' colors were chosen because no self respectin' sci-fi spaceship worth it's blaster ray would be anythin' but silver. T' red be chosen for contrast t' increase in-flight visibility and t' give t' illusion o' it still bein' hot from re-entry's heat. Most early ships' design/paint schemes tended t' be bold but nay very detailed, ya bilge rat, so I did t' same here.

Flight Tests/Motor Recommendations:
T' computer sims recommend t' C11-3, matey, D12-5, and E9-6 for single motor flights. Well, blow me down! Ya scallywag! Predicted altitudes range from 350' on a single C11 t' 1800' for a full cluster o' an E9 and 3-C6's.

Obviously clustered flights should have longer delays for t' primary motor than t' above recommendations. Well, blow me down! Pod motor delays should be shorter than but close t' t' primary's delay as a precaution against becomin' low altitude projectile hazards as they eject.

Flight Picture

T' first flight was on a single D12-7. Ya scallywag! Blimey! Arrow straight and picture perfect, me hearties, givin' a "slow" majestic lift-off. Blimey! Blimey! No single E9 flights will be attempted after seein' t' slow lift-off o' t' single D12, arrr, E's will only be used in clusters.

Second flight was a "destructive testing" flight with a purposeful cluster "misfire". Motors were a D12-3 and a single A6-5. Ahoy! T' D12's shorter delay be in case o' problems t' flight would be cut short. Aye aye! Again t' Manatee gave a perfect flight without a hint o' instability.

T' first full cluster flight be on a C11-7 and three A8-5's. Aye aye! Begad! This was one o' two cluster configurations that be expected t' give t' most trouble. T' C11 due t' it's lower power, shiver me timbers, shiver me timbers, ya bilge rat, and t' E9 due t' it's lower thrust. Aye aye! Begad! There turned out t' be another problem, t' launch system wasn't able t' provide enough current t' fire 4 motors at once and only t' C11 lit. Aye aye! As expected t' C11 wasn't powerful enough when hampered with t' weight o' 3 unlit motors, me hearties, arrr, fortunately damage was limited t' a broken fin that was field repaired for another try. Ahoy! Changes were made in t' launch system t' increase current so t' 2nd attempt was successful, arrr, though one outboard motor didn't light, arrr, and t' Manatee landed safely.

Flight Picture

As o' this writin' an E9 cluster has nay been tried due t' t' motor bein' out off stock at t' local hobby shop. Ahoy! Blimey! Well, blow me down! Blimey! Blimey! Blimey! However, based on t' above 4 flights, t' followin' assumptions seems reasonable. Ahoy! Blimey! T' C11-3 and D12-5 are viable single motors while an E9 likely is not. In clusters t' C11 should remain a short delay motor, due t' it's lower power, in case o' cluster misfires. Blimey! Blimey! Blimey! Blimey! In general do nay use a longer delay if usin' A motors in t' cluster. Arrr! Blimey! Blimey! Blimey! Blimey! Blimey! T' D12 be t' optimum motor for all applications. Cluster launches _are_ impressive. Aye aye! Blimey! Blimey! Blimey! T' altitude predictions were overly optimistic.

Launch12/6/04 Update: Yesterday's launch was t' final flight test for t' Good Ship Manatee. Avast, me proud beauty! Planned were two full cluster flights. Well, blow me down! One D12/threeC6 and one E9/threeC6. Ya scallywag! Aye aye! Blimey! T' D12 flight be first since t' E9 flight would triple t' total power o' any previous flight. T' flight was very showy for spectators as t' outboard motors left a triple spiral o' smoke as t' Manatee spun on accent. Ya scallywag! Blimey! It's assumed this be caused by a slight misalignment o' t' outboards, arrr, but it wasn't a bad thin' given t' visual effect. Arrr! It was at appogee however it was discovered t' central D12 had failed t' ignite and t' rocket did a very impressive lawndart since t' outboards alone still provided 50% more power than any prior flight and had sent t' Manatee t' highest yet. Begad! Begad! Blimey! T' payload section be destroyed, me hearties, ya bilge rat, absorbin' t' bulk o' t' impact and sparin' t' booster section which, though damaged, is repairable. Well, blow me down! Blimey! Obviously t' E9 flight was scrubbed.

It's nay known if thar will be another launch where t' repaired Manatee can be flown before t' contest dead line. Blimey! Thus this might be all t' information that can be provided. Aye aye! In general t' design has proven very stable in flight with t' only problem bein' t' reliablity o' gettin' all motors t' ignite. Ahoy! Arrr! This re-enforces t' opinion that this is nay a rocket recommended for a first cluster attempt. One possible solution come t' mind, me bucko, t' have t' central motor on it's own circuit separate from t' outboard motors so t' increase it's reliablity. Blimey! Avast, me proud beauty! This assumes a launch system that can handle simultaneous launches, such as with drag races. Blimey! An upscale o' t' design so it could carry electronics t' control recovery in case o' mishap might be fun t' try too (G40 and 3 E9's!!!!).

Summary:
Pros - Flexible in t' range o' motors it can use, ya bilge rat, t' adapt t' local flight conditions, me bucko, arrr, while still givin' good performance across t' board. Begad! Cluster flights put on a show for spectators. Blimey! It should be able t' mount an Estes MaxTrax altimeter for those wantin' t' know how high is goes.

Cons - Nay a rocket I would recommend for your first cluster flight. Mis-alignments in t' fins/pods could cause "interesting" flight paths. Begad! Blimey! Ya scallywag! Blimey! Make VERY sure your launch system can provide adaquate power for cluster flights. Aye aye! Blimey! Well, blow me down! Blimey! It might fly too high and never come back because it "landed in Oz."

comment Post a Comment