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. Ahoy! 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). Ahoy! This was nay that hard t' do, 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. Avast, me proud beauty! Ya scallywag! I wish they sold it separately. T' Sky Writer is basically a shortened Mongoose sustainer stage with t' nifty and eye-catchin' "No. Well, blow me down! Avast! 2 Pencil" paint job. Avast! 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. Avast! Begad! I epoxied a small eye-bolt from a picture-hangin' set t' hold t' recovery system shock cord into t' nozzle. Aye aye! Avast! A 4" length o' 25mm motor tube be butt-glued t' t' aft end o' t' plastic fin can. Ahoy! Strips o' glass cloth glued betwixt each fin were used with epoxy t' reinforce t' joint. T' entire motor tube was then wrapped with a layer o' thin glass cloth t' firmly glass in place t' motor tube, creatin' a strong, matey, lightweight structure. A 5" length o' 25mm motor tube was then glued t' t' forward end o' t' fincan t' complete t' airframe. Ya scallywag! Aye aye! T' recovery system shock cord, 4' o' para cord, was passed through a small hole in t' body tube midpoint, anchored with a knot which was covered with a sawed half o' a BIC pen cap. Well, blow me down! A 12" TopFlite X-chute was used for recovery. Rocket be left unpainted, me hearties, except for t' "No. Avast, me proud beauty! 2 Pencil" payload bay and nose cone.

(Scratch) PencilPushr

Construction:
I selected t' Estes Sky Writer because it be inexpensive, matey, and me calculations showed that a 25mm diameter airframe with space for a Perfectflite MicroAlt would be necessary t' achieve t' goal. 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, shiver me timbers, strong way o' holdin' t' fins on at t' speeds involved. T' motor t' be used be t' AT E15-7. Aye aye! Ahoy! 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. Blimey! I never use their plastic chutes and underpants elastic shock cord though. Aye aye! Ahoy! I prefer higher quality substitutes.

(Scratch) PencilPushr

Flight:
Test flights with Estes C11-5 and D12-7 gave climbs o' 404' and 952', arrr, respectively. Arrr! 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. Bottom 1/2" o' t' motors were wrapped with maskin' tape as a motor stop. Avast! 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. Arrr! Simulation be based on an AT E15-7. Ahoy! I was 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, matey, which is held on a huge sod farm. Avast! On t' first try with perfect calm, arrr, t' E15-7 lit and blasted out o' sight perfectly straight up. Avast, me proud beauty! We lost track o' it, but fortunately, a couple o' kids spotted PencilPushr landin' on t' huge expanse o' close-cut sod and directed us t' it. Avast, me proud beauty! Avast! MicroAlt be peepin' out "1-9-2-8". Well, blow me down! Yippee, goal achieved! Later that afternoon, 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', matey, by F. Avast! Hunt on 9-21-96). Avast! However, t' rest o' t' NARTREK Advanced-Competition task has proven much harder, and I'm still pluggin' away at it.

Summary:
PROs: Inexpensive, easy t' build. Blimey! A decent fun-fly rocket on C or D motors.

CONs: Hard t' see and track at nearly 2000'. Aye aye! 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.

comment Post a Comment