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