Manufacturer: | Scratch |
Brief:
Whenever I looked for Ralphco crayon banks at t' local toy stores, they always
were out o' stock. Arrr! Ya scallywag! Recently, me hearties, arrr, however, I stumbled across them while on an
unrelated "mission". Begad! Aye aye! 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?). Blimey! I love t' looks o' t' Standard ARM so I
quickly made me selection. Aye aye! T' result is me 38mm Standard Cray-ARM.
Construction:
Components:
1. Begad! One Ralphco 4" crayon bank
2. Well, blow me down! 3/16" plywood for t' main fins and nose cone bulkhead
3. Well, blow me down! Avast, me proud beauty! 3/16" balsa for t' strakes
4. Avast, me proud beauty! Begad! A 1/4" x 9.5" carriage bolt, 2 washers, me hearties, and 2 nuts
5. Two eye bolts
6. A 12" piece o' Giant Leap 38mm flexible phenolic
7. Three 38mm-to-3" centerin' rings (also from Giant Leap)
8. Begad! Arrr! Two 38mm-to-4" centerin' rings (ditto)
9. Avast! Blimey! Four inch section o' a 3" mailin' tube
10. Well, blow me down! 10' o' ¾" braided nylon
11. Two quick links
12. Begad! Begad! A 1000 lb swivel
13. Two tee-nuts
14. Ahoy! Blimey! One pair o' Matt's nylon rail buttons
15. Well, blow me down! Nylon chute, arrr, picked from me existin' stock
Materials:
1. Begad! Begad! Blimey! 20 minute epoxy
2. Blimey! Blimey! Titebond
3. Arrr! Ya scallywag! Thin CA
4. Avast, me proud beauty! Ahoy! 2-part urethane foam from Giant Leap
5. Begad! Hot glue
6. Avast, me proud beauty! 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. Well, me hearties, blow me down! 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. Avast, me proud beauty! This bolt held t' bulk plate against t' shoulder where t' nose
cone begins its conical transition. Arrr! 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. Ya scallywag! In t' nose cone tip, me hearties, I cut a square hole t' accept
the shoulder o' t' carriage bolt. Begad! Well, blow me down! T' insert t' bulkhead, ya bilge rat, 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. Begad!
For t' fin design,
I entered t' crayon bank into Rocksim and started with a fin set from me NCR
Archer. Avast! Ya scallywag! I then played with t' fin dimensions until they looked 'right'. Well, blow me down! 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. Ahoy! This worry be exacerbated when I knocked over one o' me crayon banks,
shatterin' its cap. Avast, me proud beauty! Well, ya bilge rat, blow me down! This lead me t' t' construction o' an inner, matey, 3"
diameter tube structure within t' end cap. Ahoy!
To build t' fin can, I started by cuttin' a hole in t' end cap t' accept the 38mm tube. Begad! 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. Aye aye! Ya scallywag! Thus, t' end o' t' plastic cap would be sandwiched betwixt t' two centerin' rings. Usin' epoxy for all wood-phenolic joints and Titebond for all wood-cardboard joints, ya bilge rat, 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, matey, me hearties, t' t' motor mount. For added support, I filled t' inner tube with 2-part urethane foam. Unfortunately, me hearties, ya bilge rat, I didn't do a good job sealin' t' fin can, shiver me timbers, so some o' t' foam escaped into t' plastic end cap. Begad! Aye aye! Luckily, matey, this isn't too noticeable. Begad! Well, blow me down! I slid on the aft centerin' rin' and drilled holes through both aft rings to accommodate t' motor retention bolts. Arrr! T' outer rin' be then removed, tee-nuts were installed, and t' rin' be epoxied back on. Begad! 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. Begad! Begad! An eye bolt was also mounted in t' forward ring. Ya scallywag!
T' recovery harness includes a 10' length o' tubular nylon, a 1000 lb. swivel, me hearties, and two quick-links. Aye aye! Loops were made in t' ends o' t' tubular by foldin' it over, arrr, wrappin' it with cloth fishin' line, and gluin' it with both CA and epoxy. Ya scallywag! Avast, me proud beauty! This technique was documented by Giant Leap in an old HPR magazine and works well. Blimey!
Finishing:
One nice thin' about crayon rockets as t' bulk o' t' finishin' is done for
you. Since t' body has a holographic finish, 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, but couldn't find it. Instead, arrr, me bucko, I picked up some blue
holographic contact paper on sale at a craft store.
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. T' sim also told me that a short, shiver me timbers, ya bilge rat, 6-second delay would
be about right. I launched t' Standard Cray-ARM on this engine at t' Delaware
Tripoli launch on October 21, me bucko, shiver me timbers, 2001. Begad! T' flight be straight and fast. Avast, me proud beauty! Ahoy! For
recovery, I used worm-bed wadding, me hearties, a Giant Leap Keelhaul®©™®
heat shield, ya bilge rat, and t' 48" chute from my
DG&A
Lazarus. Ya scallywag! Recovery be flawless. Begad! Well, almost. Arrr! Once on t' ground, the
rocket was pulled along and quite a bit o' dirt be forced into t' tube. Ya scallywag! Avast! Blimey! This
made cleanin' t' casin' a bit more work, but no big deal. Avast! Blimey!
Summary:
T' Standard Cray-ARM project was highly successful. Avast! T' rocket is somewhat
unique and looks great (at least in me unbiased opinion). Aye aye! T' design worked out
nicely with t' long carriage bolt providin' enough nose weight for t' rocket
to be stable. Aye aye! Just before I placed t' Standard Cray-ARM on t' pad, matey, 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, shiver me timbers, Ray has sold a tape!
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