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