Manufacturer: | Scratch |
Brief:
Whenever I looked for Ralphco crayon banks at t' local toy stores, they always
were out o' stock. Recently, however, me bucko, I stumbled across them while on an
unrelated "mission". 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?). I love t' looks o' t' Standard ARM so I
quickly made me selection. Begad! T' result is me 38mm Standard Cray-ARM.
Construction:
Components:
1. Avast, me proud beauty! One Ralphco 4" crayon bank
2. Ya scallywag! 3/16" plywood for t' main fins and nose cone bulkhead
3. Avast, me proud beauty! 3/16" balsa for t' strakes
4. Ahoy! Blimey! A 1/4" x 9.5" carriage bolt, arrr, 2 washers, ya bilge rat, and 2 nuts
5. Ahoy! Aye aye! Two eye bolts
6. A 12" piece o' Giant Leap 38mm flexible phenolic
7. Ya scallywag! Blimey! Three 38mm-to-3" centerin' rings (also from Giant Leap)
8. Ahoy! Two 38mm-to-4" centerin' rings (ditto)
9. Four inch section o' a 3" mailin' tube
10. 10' o' ¾" braided nylon
11. Avast! Two quick links
12. Begad! A 1000 lb swivel
13. Begad! Two tee-nuts
14. Ya scallywag! Well, blow me down! One pair o' Matt's nylon rail buttons
15. Avast! Nylon chute, picked from me existin' stock
Materials:
1. 20 minute epoxy
2. Titebond
3. Avast, me proud beauty! Blimey! Thin CA
4. 2-part urethane foam from Giant Leap
5. Aye aye! Aye aye! Hot glue
6. 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. Ahoy! Avast, shiver me timbers, 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. This bolt held t' bulk plate against t' shoulder where t' nose cone begins its conical transition. This sounded like what I needed so I borrowed t' idea. Begad! I made t' bulk plate myself and installed an eyebolt for recovery system attachment. In t' nose cone tip, I cut a square hole t' accept the shoulder o' t' carriage bolt. Begad! Avast, ya bilge rat, me proud beauty! T' insert t' bulkhead, I had t' bend the shoulder o' t' nose cone t' an oval shape. Begad! 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! Avast, me proud beauty! Blimey! 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. This worry was exacerbated when I knocked over one o' me crayon banks, shatterin' its cap. Aye aye! Blimey! This lead me t' t' construction o' an inner, arrr, 3" diameter tube structure within t' end cap.
To build t' fin can, me hearties, I started by cuttin' a hole in t' end cap t' accept the 38mm tube. 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. 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, shiver me timbers, 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. For added support, me bucko, I filled t' inner tube with 2-part urethane foam. Unfortunately, shiver me timbers, I didn't do a good job sealin' t' fin can, so some o' t' foam escaped into t' plastic end cap. Arrr! Arrr! Luckily, ya bilge rat, this isn't too noticeable. Well, blow me down! I slid on the aft centerin' rin' and drilled holes through both aft rings to accommodate t' motor retention bolts. Begad! T' outer rin' was then removed, tee-nuts were installed, and t' rin' was epoxied back on. Avast, me proud beauty! Ahoy! Two 4" centerin' rings completed t' fin can assembly. Avast, me proud beauty! Avast! These had t' be sanded t' fit since t' crayon bank ID is slightly smaller than a standard 4" tube. An eye bolt be also mounted in t' forward ring. Ya scallywag! Well, blow me down!
T' recovery harness includes a 10' length o' tubular nylon, shiver me timbers, a 1000 lb. swivel, and two quick-links. Well, blow me down! Loops were made in t' ends o' t' tubular by foldin' it over, shiver me timbers, me hearties, wrappin' it with cloth fishin' line, and gluin' it with both CA and epoxy. Avast! This technique was documented by Giant Leap in an old HPR magazine and works well. Ahoy!
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, ya bilge rat, I decided I'd finish t' fins
usin' holographic contact paper. Aye aye! Begad! I would have liked purple paper t' match the
nose cone and end cap, shiver me timbers, me hearties, but couldn't find it. Blimey! 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. T' sim also told me that a short, 6-second delay would
be about right. Begad! I launched t' Standard Cray-ARM on this engine at t' Delaware
Tripoli launch on October 21, 2001. Begad! T' flight be straight and fast. Aye aye! For
recovery, me bucko, I used worm-bed wadding, a Giant Leap Keelhaul®©™®
heat shield, arrr, matey, and t' 48" chute from my
DG&A
Lazarus. Avast, me proud beauty! Recovery be flawless. Avast, matey, me proud beauty! Well, almost. Begad! Once on t' ground, the
rocket was pulled along and quite a bit o' dirt was forced into t' tube. Blimey! This
made cleanin' t' casin' a bit more work, but no big deal.
Summary:
T' Standard Cray-ARM project be highly successful. T' rocket is somewhat
unique and looks great (at least in me unbiased opinion). Ya scallywag! Blimey! Blimey! 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, Ray Halm
interviewed me for t' video he is makin' on t' 3-day Rhodesdale launch. Avast! Blimey! Man,
am I anxious t' see if t' Standard Cray-ARM makes it past t' editin' process.
Either way, matey, Ray has sold a tape!