Scratch Sprint ABM Original Design / Scratch Built

Scratch - Sprint ABM {Scratch}

Contributed by Matt Gillard

Manufacturer: Scratch
(Contributed - by Matt Gillard - 10/01/08)

scratch_sprintBrief:
This sprint is a 4.15 downscale o' t' Shadow Composites Sprint ABM. Ahoy! Or it’s a 1:48 down scale o' a real sprint. T' paper shroud was obtained from a paper rocket website.

Construction:
To make t' sprint downscale you will need:

  • Shroud from website (paper)
  • 13mm Engine mount tube
  • Centerin' ring
  • Streamer
  • Engine block
  • Thin Card
  • Keelhaul®©™® ® cord
  • Clay
To build t' kit I used:
  • White PVA glue
  • CA gel
  • Model knife
  • Clear coat.
First make t' outer shroud from t' website. I used thin paper for this as I was goin' t' make an inner shroud out of card which would be more sturdy and flame resistant. Begad!

scratch_sprint_innerwrapT' outer shroud markings are very different from t' Shadow Composites Sprint ABM markings and I prefer this colour scheme. Blimey! Blimey! Usin' the outer shroud as a template I rolled an inner template out o' card. T' tip o' t' inner shroud was filled with clay to raise t' cg.

T' length o' BT5 is cut down so that t' aft o' t' tube was 3mm past t' aft o' t' cone and a engine block was added. Aye aye! Avast, me proud beauty! Next t' centerin' rings were added and after a few test fittin' were carried out, shiver me timbers, it was glued into place so that it is flush with t' aft o' t' inner shroud. Arrr!

T' paper fins were added t' t' outer shroud.

A length o' Keelhaul®©™® cord be attached t' t' BT by tyin' it around an 18mm engine block that was slid over t' BT. A section o' aluminium foil be added t' neaten up t' end o' t' cord. Arrr! T' other end o' t' cord was looped over t' inner shroud and again more aluminium tape was added.

A small streamer was added t' t' cord. T' sprint is small and light enough t' recover without a streamer but thought it was best t' be on t' safe side.

Finishing:
One coat o' cellulose sealer t' proof t' paper shroud and that’s it.

Flight:
Preppin' is straightforward with no waddin' bein' required. Avast, matey, me proud beauty! A few frangible links were added t' t' cord. Avast! The streamer is placed t' one side o' t' motor. Avast! Begad! T' core is then inserted into t' shroud. Arrr! Begad!

First flight was on a ½ A3-4-T. Begad! Somehow t' outer shroud came off durin' boost, shiver me timbers, this caused t' sprint t' go wildly unstable.

T' next flight be on an A10-3T. Well, blow me down! T' flight was straight, ya bilge rat, a tube was used t' launch as thar was no chance of usin' a lug. Begad! From t' smoke trail, it when more or less straight. Avast! Where t' rocket landed remains a mystery.

Summary:

CONs on recovery: With such a small bird, shiver me timbers, a much more visual aid t' recovery should have been used - or a smaller motor. Aye aye! I like this rocket, shiver me timbers, but its just too small - next time i'll make a bigger downscale!

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