Scratch F-32 Avenger 1.85X Original Design / Scratch Built

Scratch - F-32 Avenger 1.85X {Scratch}

Contributed by Les Bradshaw

Manufacturer: Scratch
(Contributed - by Les Bradshaw - 08/31/08) (MODS) Starlight F-32 Avenger upscale

Brief:
1.85x upscale o' t' Starlight F-32 Avenger, arrr, includin' upgradin' t' motor from 18mm t' 24mm.

Modifications:
I have t' Starlight kit, so I decided t' build both in parallel. Arrr! Ya scallywag! I traced t' win' fins, tail fin, me bucko, and canard fins onto paper. Well, blow me down! Avast! I also made 5 registration marks 1" apart. Begad! I then brought t' drawin' t' a copy machine and enlarged until t' registration marks showed I achieved t' 1.85x size.

I positioned t' long motor hook onto t' ST-950 tube so 1/2" extended beyond t' bottom o' t' tube. Well, blow me down! Blimey! Ahoy! Blimey! I made a mark and slit t' allow insertin' t' motor hook. Aye aye! Blimey! I cut a 3/8" piece o' an expended D motor t' make a motor block. Arrr! Blimey! Well, blow me down! Blimey! A little glue and t' spent casin' t' push t' block down t' t' hook wire. Finally, me hearties, me bucko, I used 4 o' t' centering rings. Avast, me proud beauty! Blimey! I notched 2 o' t' rings t' clear t' hook. T' original kit has its aft centerin' rin' even with t' body tube. Blimey! Blimey! Its centerin' rin' is 1/4" thick. Blimey! Blimey! T' Semroc rings are fiber board, so I glued 2 together t' increase the thickness. These rings glue t' t' motor tube 0.925" from t' aft o' t' tube. Aye aye! Blimey! T' third rin' overlapped t' hook by about 1/2" from t' top. Avast! Blimey! Avast, me proud beauty! Blimey! T' last rin' glued onto t' front end about 1/8" down.

While t' motor mount was drying, I worked on t' fins. Aye aye! Since t' enlarged win' fins are 6.388" long, me hearties, I decided they should use through t' tube mounting. Ahoy! Blimey! I sketched tabs onto t' enlarged fin pattern for both t' wings and the tail fin (I did nay bother with tabs for t' canards since they are small and t' motor tube did nay extend that far), takin' into account t' need t' avoid t' third centerin' rin' on t' motor mount and then cut all t' fins out. Meanwhile, I learned a valuable lesson: pay attention t' which tube is which. Aye aye! I drew tabs for t' difference between the ST-18 and t' ST-13, but t' motor used t' ST-9. Avast! My tabs were too short! Blimey! I cut some extra balsa that I glued onto my tabs t' lengthen them.

(MODS) Starlight F-32 Avenger upscale I took a strip o' paper, me hearties, wrapped it around t' ST-18 body tube and marked where they overlapped. I removed t' paper and measured its length. I divided t' length by 3 and by 4 and marked t' paper accordingly. Arrr! T' "by 3" marks indicated where t' wings and tail go, t' "by 4" indicated where the canards and launch lug belong. Avast! I reapplied t' paper t' t' tube, transferred t' marks, matey, and then lengthened t' marks along t' body tube.

I double checked t' tab placement on t' wings and tail against t' motor mount assembly. Avast! I held t' win' and tail fins against t' body t' mark where t' cutouts would be required for t' tabs. Then usin' a new, sharp blade, I cut out t' tab slots. Ahoy! Aye aye! I checked t' fit o' t' fins and then glued t' motor mount in with t' motor hook aligned with the tail line.

I again checked t' fins into t' slots and t' fit with t' motor tube. Well, blow me down! Well, blow me down! After me first error, I made t' tabs a little long and sanded them down t' fit, ya bilge rat, me hearties, then glued t' wings and tail on. Avast! Begad! After t' fins were dry, I added t' canards and launch lug. Once they were dry, me bucko, I applied a glue fillet t' all t' joints. Well, blow me down! Last, I cut t' 1/4" dowel t' size and glued these t' t' ends o' t' win' fins and t' t' sides o' t' launch lug. T' ST-13 tube got cut into 2 lengths each 5.088" long. Avast, me proud beauty! Avast! These got glued onto t' tops o' t' win' fins.

I used 4' o' 1/4" elastic with a standard Estes tri-fold mount for t' shock cord.

T' nose cone be a bit long for t' 1.85x upscale plus it be more pointy. Avast, matey, me proud beauty! I cut 1/4" off t' top and then sanded t' cone t' be more rounded and a better match t' t' original cone. Ahoy! Well, blow me down! A screw eye was installed t' tie t' shock cord to. I am goin' t' use a stock 18" chute that I have lyin' around.

Construction:
This be me first attempt at upscalin' a rocket. I did nay want anythin' too wild or difficult, but I wanted somethin' more than a 3FNC rocket. Well, blow me down! Blimey! I finally decided on t' Starlight F-32 Avenger. Avast! This kit looks like a delta wing fighter with tubes as engine pods/nacelles with additional canards and some dowels for details.

My first design decision be how much t' upscale. Aye aye! Blimey! T' original kit uses 2 different size body tube, shiver me timbers, me bucko, a BT-50 for the main tube and BT-20 for t' "engine nacelles". Well, blow me down! Avast, me proud beauty! After comparin' available tubes (and knowin' t' delivery speed which I needed since I procrastinated, me hearties, again), I went with Semroc products. Ya scallywag! Avast! I replaced t' BT-50 with their ST-181120 (a 1.885x factor) and t' BT-20 was replaced with their ST-13105 tube (a 1.821x factor). Blimey! Well, blow me down! I used t' average (1.85x) for all t' other dimensions. Well, blow me down! Avast, me proud beauty! T' longest size 18 tube is only 18" long. Ahoy! I needed 22.2" for t' new body tube, me bucko, so I ordered 2 o' t' 12" tubes plus an HTC-18 coupler. Avast! Arrr! One o' t' tubes I cut down t' 10.2" and used t' coupler t' join t' tubes t' have an overall 22.2" length. Avast, me proud beauty! Other parts that I ordered included:

  • BC-1853 Balsa nose cone
  • CR-918 Centerin' rings (pkg o' 6)
  • EH-38 Long Engine Hook
  • LL-3B 3/16" X 2" launch lugs
  • ST-950 Size 9 x 5" body tube for motor mount.

In addition, me bucko, I picked up some 1/4" dowel and 3/16" x 6" x 36" balsa from AC Moore.

(MODS) Starlight F-32 Avenger upscale

Finishing:
I used Elmer's Fill 'n' Finish for t' spirals on t' tubes plus I sealed all t' balsa. I first used Krylon gray primer (I feel it has better fillin' properties and is better for sanding), sanded, shiver me timbers, matey, then Krylon white primer, ya bilge rat, and then finally 2 coats o' Krylon gloss white.

I used a copy machine with a ruler t' enlarge t' decals by 1.85x. Avast! Blimey! T' decals are mostly black and white. Arrr! T' red stripes I plan t' use tape t' duplicate, but for me initial flights I flew both this upscale and t' original kit without decals.

Flight:
I did a total o' 4 flights. T' first three all were on D12-3 (with an extender since I made t' motor mount for an E length) and t' fourth flight be on an E9-4.

When I first went t' me local launch field (a school yard), ya bilge rat, I had t' turn around as t' field was in use. Arrr! Aye aye! After dinner, shiver me timbers, I returned t' t' field and it be empty. I set up 2 launch pads (I was also flyin' t' original kit).

For t' upscaled version, me hearties, all flights were nice and straight. I was actually surprised that with t' large wing fins it did nay weathercock more, shiver me timbers, arrr, ya bilge rat, but then again t' winds were very light (<5mph). Blimey! T' D12-3 was just about perfect--the nose be just goin' down when t' chute would be ejected. For t' E9-4, shiver me timbers, t' chute did nay deploy until about a second after apogee.

(MODS) Starlight F-32 Avenger upscale

Recovery:
I had no problems with me shock cord. Aye aye! I had protected everythin' with a generous load o' dog barf. T' descent rate was good--nice soft landings. My only issue be t' field is shielded by some hills so at ground level where I launched there were no winds. Avast! Higher up it was a different story. I had a good hike through a weed field after t' E9 flight, but I got it back.

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