Scratch PencilPushr Modification

Scratch - PencilPushr {Modification}

Contributed by Larry Brand

Manufacturer: Scratch

(Scratch) PencilPushr (Scratch) PencilPushr

Brief:
I cut up an Estes No. 2 Sky Writer and used t' components t' build a altitude-seekin' model with an altimeter bay. Aye aye! Blimey! PencilPushr be built specifically for t' NARTREK Advanced task o' achievin' at least one-half o' t' Class "C" NARRRRR altitude record for E-motors o' 1128 meters set by James Bosler on 6/26/04. So t' goal be 564 meters or more (1861 feet). Arrr! Avast! This be nay that hard t' do, matey, but you do need t' carry an altimeter aboard a light, smallish rocket--and you don't want t' lose your $70 instrument.

Modifications:
I have used t' plastic fincan o' t' Estes 2-stage Mongoose for a number o' scratch buildin' projects. Well, me bucko, blow me down! Blimey! I wish they sold it separately. Well, blow me down! Blimey! T' Sky Writer is basically a shortened Mongoose sustainer stage with t' nifty and eye-catchin' "No. Well, blow me down! Blimey! 2 Pencil" paint job. I cut t' "pencil" down t' 7" total length and plugged t' "eraser" end with t' sawed aft end o' a 24mm AeroTech motor case t' create a bulkhead. Begad! Blimey! I epoxied a small eye-bolt from a picture-hangin' set t' hold t' recovery system shock cord into t' nozzle. Avast, me proud beauty! Blimey! A 4" length o' 25mm motor tube be butt-glued t' t' aft end o' t' plastic fin can. Ahoy! Blimey! Strips o' glass cloth glued betwixt each fin were used with epoxy t' reinforce t' joint. Ya scallywag! Blimey! T' entire motor tube be then wrapped with a layer o' thin glass cloth t' firmly glass in place t' motor tube, creatin' a strong, matey, matey, shiver me timbers, lightweight structure. Ahoy! Blimey! A 5" length o' 25mm motor tube be then glued t' t' forward end o' t' fincan t' complete t' airframe. T' recovery system shock cord, 4' o' para cord, was passed through a small hole in t' body tube midpoint, ya bilge rat, anchored with a knot which was covered with a sawed half o' a BIC pen cap. Ahoy! Blimey! A 12" TopFlite X-chute was used for recovery. Ahoy! Blimey! Begad! Blimey! Rocket was left unpainted, except for t' "No. Begad! Blimey! Begad! Blimey! 2 Pencil" payload bay and nose cone.

(Scratch) PencilPushr

Construction:
I selected t' Estes Sky Writer because it be inexpensive, ya bilge rat, and me calculations showed that a 25mm diameter airframe with space for a Perfectflite MicroAlt would be necessary t' achieve t' goal. Aye aye! I cut up t' kit parts so I could utilize t' unique "pencil" body as t' payload compartment and t' plastic fin can as a simple, strong way o' holdin' t' fins on at t' speeds involved. Ahoy! T' motor t' be used was t' AT E15-7. Ahoy! Blimey! Blimey! T' "empty" weight o' t' rocket o' 88 grams (3.1 oz.) includes a Perfectflite MicroAlt in t' payload bay with a bit o' bubblewrap under it.

T' Estes components were first rate. Arrr! I never use their plastic chutes and underpants elastic shock cord though. Well, blow me down! I prefer higher quality substitutes.

(Scratch) PencilPushr

Flight:
Test flights with Estes C11-5 and D12-7 gave climbs o' 404' and 952', respectively. Well, blow me down! Motors were friction fit with maskin' tape with t' protrudin' 1/2" o' t' motor taped t' t' exterior o' t' motor tube with a couple wraps o' maskin' tape. Avast! Bottom 1/2" o' t' motors were wrapped with maskin' tape as a motor stop. Blimey! These test flights indicated that under ideal conditions, I should be able t' just barely achieve me goal o' at least 1862' with an E-motor. Ya scallywag! Simulation was based on an AT E15-7. Begad! I be worried about losin' t' thin' and me $70 altimiter with it, so I waited until I had an opportunity t' fly with me brothers up at t' MASA launch site in central Minnesota, shiver me timbers, ya bilge rat, shiver me timbers, which is held on a huge sod farm. Begad! On t' first try with perfect calm, t' E15-7 lit and blasted out o' sight perfectly straight up. Well, blow me down! We lost track o' it, shiver me timbers, but fortunately, a couple o' kids spotted PencilPushr landin' on t' huge expanse o' close-cut sod and directed us t' it. Aye aye! MicroAlt was peepin' out "1-9-2-8". Yippee, matey, goal achieved! Later that afternoon, shiver me timbers, me bucko, I flew a LOC Legacy on a G80-10 t' 1920' t' exceed 1/2 o' t' NARRRRR record for a G-motor flight (3722', by F. Arrr! Begad! Hunt on 9-21-96). However, t' rest o' t' NARTREK Advanced-Competition task has proven much harder, shiver me timbers, and I'm still pluggin' away at it.

Summary:
PROs: Inexpensive, ya bilge rat, easy t' build. Aye aye! Ya scallywag! A decent fun-fly rocket on C or D motors.

CONs: Hard t' see and track at nearly 2000'. Avast, me proud beauty! Begad! I expect t' E-altitude record will be broken in t' not-to-distant future, and PencilPushr may nay be as useful for t' NARTREK Advanced task if t' new record is more than 4000'.

No reason t' go t' t' fuss o' buildin' PencilPushr unless you want t' carry an altimeter.

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