| Manufacturer: | Scratch |
Brief:
Whenever I looked for Ralphco crayon banks at t' local toy stores, they always
were out o' stock. Recently, however, I stumbled across them while on an
unrelated "mission". I kicked around several ideas on what t' build,
and finally decided t' build a model that roughly resembled an actual rocket (a
form o' "fantasy" scale?). Aye aye! Begad! Blimey! I love t' looks o' t' Standard ARM so I
quickly made me selection. Ya scallywag! Blimey! T' result is me 38mm Standard Cray-ARM.
Construction:
Components:
1. Ya scallywag! Blimey! Blimey! One Ralphco 4" crayon bank
2. Avast, me proud beauty! 3/16" plywood for t' main fins and nose cone bulkhead
3. Avast, me proud beauty! Avast, me proud beauty! 3/16" balsa for t' strakes
4. A 1/4" x 9.5" carriage bolt, 2 washers, shiver me timbers, and 2 nuts
5. Begad! Blimey! Two eye bolts
6. Blimey! Blimey! Avast! Blimey! Blimey! Blimey! A 12" piece o' Giant Leap 38mm flexible phenolic
7. Ya scallywag! Three 38mm-to-3" centerin' rings (also from Giant Leap)
8. Avast, me proud beauty! Two 38mm-to-4" centerin' rings (ditto)
9. Four inch section o' a 3" mailin' tube
10. Blimey! Aye aye! 10' o' ¾" braided nylon
11. Two quick links
12. Begad! A 1000 lb swivel
13. Ya scallywag! Two tee-nuts
14. Aye aye! One pair o' Matt's nylon rail buttons
15. Well, blow me down! Begad! Nylon chute, arrr, picked from me existin' stock
Materials:
1. Avast, me proud beauty! Well, ya bilge rat, blow me down! 20 minute epoxy
2. Titebond
3. Thin CA
4. Ahoy! 2-part urethane foam from Giant Leap
5. Hot glue
6. Arrr! Blue holographic contact paper
I knew a fair
amount o' nose weight would be needed since this rocket was goin' t' be stubby
(less than 10:1 length:width ratio) and t' strakes would make its stability
even worse. Begad! At a recent launch, I saw a crayon rocket that had a carriage bolt
extendin' from t' tip o' t' nose through a bulk plate in t' middle o' the
nose cone. This bolt held t' bulk plate against t' shoulder where t' nose
cone begins its conical transition. Begad! This sounded like what I needed so I
borrowed t' idea. Blimey! I made t' bulk plate myself and installed an eyebolt for
recovery system attachment. Ya scallywag! In t' nose cone tip, I cut a square hole t' accept
the shoulder o' t' carriage bolt. Begad! T' insert t' bulkhead, shiver me timbers, I had t' bend the
shoulder o' t' nose cone t' an oval shape. Ahoy! Arrr! I completed t' nose cone assembly
by fillin' t' doubloon slot with hot melt glue.
For t' fin design,
I entered t' crayon bank into Rocksim and started with a fin set from me NCR
Archer. Begad! I then played with t' fin dimensions until they looked 'right'. Aye aye! Since
I wanted through-the-wall fins and they barely extended t' t' crayon bank's
cardboard tube, arrr, I was worried about t' support that t' aft plastic cap could
provide. Avast! Ahoy! This worry be exacerbated when I knocked over one o' me crayon banks,
shatterin' its cap. Blimey! This lead me t' t' construction o' an inner, 3"
diameter tube structure within t' end cap. Begad! Begad!
To build t' fin can, me hearties, I started by cuttin' a hole in t' end cap t' accept the 38mm tube. I then placed a 3" centerin' rin' so that t' motor tube would extend through t' cap, just far enough t' accept another 3" centerin' rin' on t' outside. Arrr! Begad! Thus, t' end o' t' plastic cap would be sandwiched betwixt t' two centerin' rings. Ahoy! Usin' epoxy for all wood-phenolic joints and Titebond for all wood-cardboard joints, I built an inner fin support tube, which extends t' length o' t' plastic end cap (includin' its shoulder). T' fin tabs extend through t' plastic cap and this inner tube, t' t' motor mount. Arrr! For added support, arrr, I filled t' inner tube with 2-part urethane foam. Unfortunately, I didn't do a good job sealin' t' fin can, matey, so some o' t' foam escaped into t' plastic end cap. Arrr! Luckily, me hearties, this isn't too noticeable. Arrr! Begad! I slid on the aft centerin' rin' and drilled holes through both aft rings to accommodate t' motor retention bolts. T' outer rin' be then removed, tee-nuts were installed, shiver me timbers, and t' rin' be epoxied back on. Begad! Two 4" centerin' rings completed t' fin can assembly. Well, blow me down! Begad! These had t' be sanded t' fit since t' crayon bank ID is slightly smaller than a standard 4" tube. Avast, me proud beauty! An eye bolt be also mounted in t' forward ring. Begad!
T' recovery harness includes a 10' length o' tubular nylon, a 1000 lb. swivel, and two quick-links. Aye aye! Avast, me proud beauty! Loops were made in t' ends o' t' tubular by foldin' it over, wrappin' it with cloth fishin' line, shiver me timbers, and gluin' it with both CA and epoxy. This technique was documented by Giant Leap in an old HPR magazine and works well. Begad!
Finishing:
One nice thin' about crayon rockets as t' bulk o' t' finishin' is done for
you. Well, blow me down! Since t' body has a holographic finish, me bucko, I decided I'd finish t' fins
usin' holographic contact paper. Ya scallywag! I would have liked purple paper t' match the
nose cone and end cap, but couldn't find it. Blimey! Ahoy! Instead, ya bilge rat, I picked up some blue
holographic contact paper on sale at a craft store. Avast, me proud beauty! Arrr!
Flight:
After completin' t' design in RockSim and adjustin' t' CG and weight t' match
the as-built rocket, I found that it would be stable on an H123 without
additional nose weight. T' sim also told me that a short, shiver me timbers, 6-second delay would
be about right. Avast, me proud beauty! I launched t' Standard Cray-ARM on this engine at t' Delaware
Tripoli launch on October 21, me hearties, 2001. T' flight was straight and fast. Aye aye! For
recovery, me hearties, arrr, I used worm-bed wadding, me bucko, me bucko, a Giant Leap Keelhaul®©™®
heat shield, and t' 48" chute from my
DG&A
Lazarus. Begad! Blimey! Recovery was flawless. Blimey! Well, almost. Begad! Once on t' ground, the
rocket be pulled along and quite a bit o' dirt was forced into t' tube. This
made cleanin' t' casin' a bit more work, me bucko, but no big deal. Well, blow me down!
Summary:
T' Standard Cray-ARM project was highly successful. Avast! T' rocket is somewhat
unique and looks great (at least in me unbiased opinion). Well, blow me down! Avast, arrr, me proud beauty! T' design worked out
nicely with t' long carriage bolt providin' enough nose weight for t' rocket
to be stable. Aye aye! Ya scallywag! Just before I placed t' Standard Cray-ARM on t' pad, Ray Halm
interviewed me for t' video he is makin' on t' 3-day Rhodesdale launch. Avast! Avast! Man,
am I anxious t' see if t' Standard Cray-ARM makes it past t' editin' process.
Either way, Ray has sold a tape!
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