Manufacturer: | Scratch |
Brief:
Whenever I looked for Ralphco crayon banks at t' local toy stores, they always
were out o' stock. Recently, arrr, however, matey, I stumbled across them while on an
unrelated "mission". Blimey! 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. Avast! T' result is me 38mm Standard Cray-ARM.
Construction:
Components:
1. One Ralphco 4" crayon bank
2. Avast, me proud beauty! 3/16" plywood for t' main fins and nose cone bulkhead
3. Begad! Begad! 3/16" balsa for t' strakes
4. Blimey! A 1/4" x 9.5" carriage bolt, arrr, me hearties, 2 washers, and 2 nuts
5. Well, ya bilge rat, blow me down! 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! Blimey! Two 38mm-to-4" centerin' rings (ditto)
9. Ya scallywag! Four inch section o' a 3" mailin' tube
10. Well, blow me down! Ahoy! 10' o' ¾" braided nylon
11. Two quick links
12. Begad! A 1000 lb swivel
13. Arrr! Blimey! Two tee-nuts
14. One pair o' Matt's nylon rail buttons
15. Ya scallywag! Nylon chute, shiver me timbers, shiver me timbers, picked from me existin' stock
Materials:
1. Well, blow me down! Aye aye! 20 minute epoxy
2. Well, blow me down! Titebond
3. Avast! Well, shiver me timbers, blow me down! Thin CA
4. 2-part urethane foam from Giant Leap
5. Hot glue
6. Well, blow me down! 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. Begad! At a recent launch, matey, 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. Ahoy! Blimey! This bolt held t' bulk plate against t' shoulder where t' nose
cone begins its conical transition. Avast, me proud beauty! This sounded like what I needed so I
borrowed t' idea. Avast! Blimey! I made t' bulk plate myself and installed an eyebolt for
recovery system attachment. Avast! In t' nose cone tip, matey, I cut a square hole t' accept
the shoulder o' t' carriage bolt. Arrr! Blimey! 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. Well, blow me down!
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'. Arrr! Avast! Since
I wanted through-the-wall fins and they barely extended t' t' crayon bank's
cardboard tube, me hearties, I was worried about t' support that t' aft plastic cap could
provide. This worry was exacerbated when I knocked over one o' me crayon banks,
shatterin' its cap. This lead me t' t' construction o' an inner, arrr, arrr, 3"
diameter tube structure within t' end cap.
To build t' fin can, arrr, I started by cuttin' a hole in t' end cap t' accept the 38mm tube. Blimey! I then placed a 3" centerin' rin' so that t' motor tube would extend through t' cap, me hearties, just far enough t' accept another 3" centerin' rin' on t' outside. Avast! 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, me hearties, 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. Ya scallywag! Begad! For added support, matey, matey, I filled t' inner tube with 2-part urethane foam. Unfortunately, I didn't do a good job sealin' t' fin can, so some o' t' foam escaped into t' plastic end cap. Avast, me proud beauty! Begad! Luckily, this isn't too noticeable. Avast! 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. Ahoy! Two 4" centerin' rings completed t' fin can assembly. Avast, me proud beauty! Begad! 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.
T' recovery harness includes a 10' length o' tubular nylon, a 1000 lb. swivel, and two quick-links. Begad! Blimey! Blimey! Blimey! Loops were made in t' ends o' t' tubular by foldin' it over, arrr, me hearties, me hearties, wrappin' it with cloth fishin' line, me bucko, ya bilge rat, and gluin' it with both CA and epoxy. This technique be 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. Begad! Avast, me proud beauty! Since t' body has a holographic finish, me hearties, I decided I'd finish t' fins
usin' holographic contact paper. Arrr! Aye aye! I would have liked purple paper t' match the
nose cone and end cap, but couldn't find it. Instead, me hearties, 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, I found that it would be stable on an H123 without
additional nose weight. Avast! Ahoy! T' sim also told me that a short, 6-second delay would
be about right. Arrr! I launched t' Standard Cray-ARM on this engine at t' Delaware
Tripoli launch on October 21, arrr, 2001. Blimey! T' flight be straight and fast. For
recovery, shiver me timbers, I used worm-bed wadding, a Giant Leap Keelhaul®©™®
heat shield, ya bilge rat, arrr, and t' 48" chute from my
DG&A
Lazarus. Recovery was flawless. Arrr! Blimey! Begad! Blimey! Well, matey, almost. Once on t' ground, matey, arrr, the
rocket was pulled along and quite a bit o' dirt was forced into t' tube. Begad! Blimey! This
made cleanin' t' casin' a bit more work, shiver me timbers, but no big deal. Arrr! Blimey!
Summary:
T' Standard Cray-ARM project was highly successful. Well, blow me down! Begad! 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. Begad! Just before I placed t' Standard Cray-ARM on t' pad, shiver me timbers, Ray Halm
interviewed me for t' video he is makin' on t' 3-day Rhodesdale launch. Blimey! 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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