Manufacturer: | Scratch |
Brief:
This is me second attempt at buildin' a rocket t' match a picture. Ahoy! This time for t' 2008 EMRR Challenge and me first cluster where t' motors are significantly apart from each other.
Construction:
Parts include:
To build t' rocket I used:
T' motor mounts were constructed form two old Estes motor mount kits in t' standard fashion.
After measurin' t' photo from t' web site, t' body tube came out t' be a BT-55 that was 8.5 inches long. Avast, me proud beauty! Ahoy! Blimey! T' nose cone was a NC55AC (or as near t' AC as you can get).
T' motor mount be glued into place after a 16-inch length o' Keelhaul®©™was first added. 3 feet o' knicker elastic was then added t' t' Keelhaul®©™, shiver me timbers, and a snap swivel was added t' that. Avast, me proud beauty! Two 1.5 square inch swatches o' Nomex® heat shield was then added t' t' shock cords.
Given t' model looks as if t' CP is goin' t' be high and with two aft motors, a significant amount o' modelin' clay was added t' both nose cones. Aye aye! T' nose cones were then added t' t' shock cords. Blimey! Begad! A twelve-inch parachute was added t' each tube.
T' central platform be made from 3/8 inch balsa measurin' 3 by 9.5 inches. Blimey! This be sanded t' profile at t' front and then sealed. T' two body tubes were then added t' either side. Heavy fillets o' PVA glue were then added.
Again from measurement from t' picture, t' 4 fins were made usin' quite stiff 3/16 inch balsa. T' upper fins were cut from a triangle measurin' 1-5/8 by 6-3/4; inches. Begad! Blimey! T' fins were then sealed and glued into place on t' body tubes. I filleted t' fins three times. Avast, me proud beauty! Blimey! These four fins will be t' point o' contact with t' ground and I doubted in t' plannin' stage on t' fragility o' t' fins.
T' two aft engines on t' rocket were built for decoration only and were nay t' be part o' t' flyin' model. Begad! Begad! This be because these engines were where t' motors for t' flyin' model were goin' t' be in me original plan but this would have lowered t' CG t' low and would have been out o' scale.
T' build t' aft engines I used polymorph, me bucko, me hearties, a thermo softenin' plastic that can be made very pliable at temperatures around hot water (70-80 degrees C) but hardens at room temperature. Begad! Blimey! T' plastic when set can be sanded, drilled, painted, arrr, etc. Ahoy! Well, blow me down! Its density is similar t' t' plastic used by Estes for its nose cones. T' polymorph was molded around a 16mm balsa rod, which proved t' be more difficult than I imagined. T' polymorph cools and goes from clear and colorless t' a white plastic. Ahoy! This was then sanded into shape and then painted silver gray. T' engines hooks get in t' way o' t' aft motor engines so a slot had t' be cut out so they sat straight.
One o' t' design flaws o' this model be t' canopy. Blimey! Its shape will create lift and given its size if its construction is made o' anythin' with a density o' balsa or higher, me hearties, it could cause t' center o' gravity t' come out o' line with t' center o' thrust.
After spendin' time makin' a few hollow cardboard canopies--which failed. Ya scallywag! I decided t' use green floral block. Aye aye! Begad! Nay bein' a flower arranger, matey, ya bilge rat, I purchased some from a craft shop. Begad! Floral block has a very low density and cuts very easily. Begad! Within minute a canopy was cut. T' canopy was glued with PVA t' t' rocket.
T' floral block is porous and would give a terrible finish. Blimey! I thought that a few coats o' thick sealer would help fill in t' gaps. Ahoy! Well, ya bilge rat, blow me down! As t' solvents in t' sealer evaporated, t' sealer coat shrank and peeled a layer off t' floral block. Begad! Arrr! T' canopy was ruined. Another canopy was cut and glued into place. Avast! Aye aye! This time layers o' PVA glue was added t' t' floral block until it was smooth--this took 6 days. T' fins and canopy joints were then filleted and then had two layers o' sealer added. Aye aye! After sandin' with fine sandpaper t' whole rocket had 3 layers o' primer, sandin' betwixt coats.
Finishing:
It be nearly impossible t' find a spray paint that matched t' color on t' picture. Avast! In t' end I went for window gray. Begad! Three coats were added, sandin' with fine sandpaper betwixt coats.
T' details were added usin' a black ink pen for t' lines and black stickers for t' windows on t' canopy. T' circular emblem on either side o' t' body tubes were a deviation form t' original. I used t' EMRR "Write A Review" circular emblem, me hearties, shiver me timbers, which I thought was a nice touch! T' rocket was then sprayed with clear varnish and then two coats o' finish was applied.
Flight and Recovery:
I had lots o' concerns about this rocket, me hearties, shiver me timbers, it looks as if it would arch on boost. T' motors are far apart and Estes rocket motors are nay always exactly t' same, arrr, matey, which would give asymmetric trust. Begad! T' fins are t' first point o' contact with t' ground, and t' rocket is rather heavy for 18mm motors.
Due t' drag t' coast phase would be short, and with two parachute thar would be drift. Avast! Blimey! T' trees around me flyin' field have enjoyed t' company o' me rockets too often. Ahoy! Blimey! Aye aye! Blimey! T' overcome this I decided upon two different delays for each tube, me bucko, shiver me timbers, t' first short delay would deploy a 12 inch chute, and t' second delay would deploy a 24 inch chute 4 seconds later. Ya scallywag! Blimey! Begad! Blimey! This way thar would be a slow and hopefully soft landing, but cut down on t' drift.
Each parachute was protected by two swatches o' Nomex cloth, ya bilge rat, matey, me bucko, but a few sheets o' Estes waddin' were used as extra protection. Ahoy! A standard Estes 3mm rod was used.
For t' first flight, two Estes B motors were used, a B6-2, me bucko, and a B6-6. There be a wind o' about 5 miles per hour. This be a nervous moment, with a rocket that broke so many design rules a lot could go wrong. Blimey! I be expectin' an arched boost, with a possible power prang. Begad! However, matey, arrr, both motors lit simultaneously and t' rocket lifted at a decent rate.
T' flight be underpowered and gave a lower altitude, wobbly flight. Avast, me proud beauty! After t' burn phase she almost glided in (a very long 2 second delay). Ahoy! T' first eject went off about 30 foot from t' ground, which be just enough t' slow her down. Arrr! T' second ejection went off on t' ground. Begad! Ya scallywag! Fortunately, arrr, only minor damage occurred with one fin poppin' off, which I expected. Avast, me proud beauty! There was some charrin' t' another aft fin.
Flight two: After a quick re-gluing, about 1 hour later she was prepped again and ready for flight, this time powered by a C6-3 and a C6-7. She ripped off t' pad and climbed t' a good height o' about 800 feet. Avast, me proud beauty! Avast! There was quite a lot o' barrel rollin' towards t' end o' t' boost phase, shiver me timbers, which increased durin' t' coast phase. Aye aye! She must have done 7 complete rolls. T' boost had a slight arch t' t' right side o' t' rocket, me bucko, which I put down t' unequal thrust from t' motors. Avast, me proud beauty! Ejection was bang on apogee. Ahoy! She drifted over t' small strip wood by t' side o' t' field, shiver me timbers, and then t' second parachute deployed. Blimey! Well, blow me down! With t' rocket gods smilin' on me, me hearties, t' rocket slowed down enough for it t' just drift clear t' wood. I however did nay fare so well, runnin' through t' wood, lookin' up at t' descendin' rocket, I managed t' find a trench that be dug durin' t' Second World War. Ironically, me hearties, I had had a group o' cadets re-dig this trench out only a few months earlier. There was no damage t' either t' rocket or t' me (except pride --which comes before a fall).
I prepped t' third flight t' same as I did for flight 2. Begad! Begad! This flight was straighter and had a lot less roll. Begad! T' wind was near calm by now. After ejection at apogee, me hearties, t' rocket descended smartly until t' second parachute deployed, ya bilge rat, shiver me timbers, and another soft damage free landin' be observed.
Summary:
I am pleased with t' overall rocket. Arrr! Blimey! She flies well and is a bit different from a standard cluster.
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