Scratch 1.6X Praetor Upscale Original Design / Scratch Built

Scratch - 1.6X Praetor Upscale {Scratch}

Contributed by John McClure

Manufacturer: Scratch
Style: Futuristic/Exotic, Upscale
(by John McClure - 11/13/05) (Scratch) Upscale FlisKits Praetor

Brief:
Single stage, parachute recovery, 29mm MMT 1.6X Upscale o' t' FlisKits Praetor.

Construction:
T' lower main body tube is a BT-80H tube ("H" for heavy wall). The upper body tube is a standard wall thickness BT-70 tube. T' original Praetor model rocket design breaks at t' transition, me bucko, ya bilge rat, but on me mid power version, matey, the nose cone separates for deployment. Begad! T' BT-70 tube extends down into t' lower BT-80 tube and butts against t' top MMT centerin' ring. This makes a "double wall" tube for extra strength. Ya scallywag! T' transition piece is made from two wraps o' Bristol Board soaked in CA glue. Ahoy! Once assembled, t' entire body tube was sanded then wrapped in 1.4oz fiberglass cloth usin' ACP's EZLam-60 resin.

T' four fins are constructed o' 3/16" thick Nomex® honeycomb/Carbon Fiber composite material from AeroSpace Composite Products. T' fins were edged in 3/16" square basswood then covered with 1.4oz fiberglass cloth. Avast! They are thru-the-wall construction with 6oz fiberglass gloss providin' extra strength on t' internal fillets. Due t' t' high-aspect ratio of t' Praetor's fins I was hopin' t' get a lightweight, arrr, ya bilge rat, me hearties, yet stiff fin can. Begad! I believe I succeeded.

(Scratch) Upscale FlisKits Praetor(Scratch) Upscale FlisKits Praetor

T' motor mount tube is a BT-52H, me hearties, shiver me timbers, heavy wall 29mm tube. There are three 3/16" thick custom laser cut centerin' by BMS on t' MMT. Arrr! Blimey! Ahoy! Blimey! Blimey! Blimey! T' recovery system consists o' a 1/4" tubular Keelhaul®©™® shock cord epoxied t' t' MMT. T' tubular Keelhaul®©™® is attached t' a length o' 5mm climber's accessory cord. Aye aye! For t' nose cone, arrr, ya bilge rat, I used an Apogee P/N 19470 BT-70 plastic nose cone. T' nose cone is nay true to the upscale, me bucko, arrr, but is sure looks cool and be a lot easier t' source than a custom cone.

This be t' first time I've used composite honeycomb materials. Arrr! Avast! Other than the fins, construction is fairly standard mid-power. Aye aye! Begad! Cuttin' t' Nomex®/CF material is a breeze as long as you use t' special saw blade from ACP. Begad! Avast! I tried makin' t' first cut usin' an X-Acto knife with #11 blade. Avast! Ahoy! Although I did cut it eventually, shiver me timbers, I would nay recommend it. T' composite blade fits on a coping saw and makes t' job much easier.

Finishing:
T' fiberglass on t' body tube made finishin' much nicer. Well, blow me down! Avast, me hearties, me proud beauty! There were no spirals t' fill! Jim Flis was kind enough t' share t' "official" Praetor letterin' font with me so I could make me own version o' a Praetor logo. Avast! T' graphics were traced onto self-adhesive vinyl sheets and cut out with an X-Acto knife so they could used as maskin' stencils. Begad! Avast! T' paintin' took a while with all o' t' maskin' and spraying, but it turned out pretty good. There wasn't anythin' exotic with t' paint, just good old Krylon rattle cans. A final coat o' Future Acrylic polish gives it some gloss.

Flight:
T' first two flights were with AeroTech G38-7FJ Single Use motors. Avast! Blimey! Begad! Blimey! I got lucky. Aye aye! Blimey! Ahoy! Blimey! These motors/delays are a perfect match for this rocket. Aye aye! Blimey! T' third flight be on a G33-7J load in me AT RMS 29/40-120 case. Well, blow me down! Blimey! T' G33 is also a good motor for this bird, but t' 7 second delay was a bit long. Ahoy! Blimey!

(Scratch) Upscale FlisKits Praetor(Scratch) Upscale FlisKits Praetor

All three flights so far have been great. Blimey! Three perfect recoveries.

Flight prep is standard fare. Avast, me proud beauty! Kaplow clips for motor retention. Begad! Avast! I use a bit o' dog barf waddin' even though thar be a Keelhaul®©™® chute protector attached. Begad! Blimey! T' dog barf is mostly out o' habit, but it does protect t' chute protector.

Flights are a larger version o' t' mod-roc Praetor. Well, blow me down! Slow lift off and straight as an arrow. Arrr! One neat side effect o' t' long fins be t' aerodynamic whistle that can be heard once t' motor burns out and t' rocket coasts to apogee. Begad!

(Scratch) Upscale FlisKits Praetor

Summary:
I absolutely love this rocket. With it's long fins, it always gets looks at the flight line. T' mod-roc Praetor is one o' me all-time favorites. Aye aye! Ahoy! This mid power version is more o' t' same. Avast, me proud beauty! I was initially worried about t' fins holdin' up t' landin' stresses, but after three perfect flights, shiver me timbers, me worries are gone. Begad! Avast, me hearties, me proud beauty! This is a rocket I hope t' keep around for a long time.

comment Post a Comment