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, includin' upgradin' t' motor from 18mm t' 24mm.

Modifications:
I have t' Starlight kit, so I decided t' build both in parallel. Ahoy! I traced t' win' fins, tail fin, shiver me timbers, and canard fins onto paper. Begad! Arrr! I also made 5 registration marks 1" apart. Well, me bucko, blow me down! 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. Begad! I made a mark and slit t' allow insertin' t' motor hook. I cut a 3/8" piece o' an expended D motor t' make a motor block. Ya scallywag! Avast, me proud beauty! A little glue and t' spent casin' t' push t' block down t' t' hook wire. Finally, ya bilge rat, shiver me timbers, arrr, I used 4 o' t' centering rings. Well, blow me down! Begad! I notched 2 o' t' rings t' clear t' hook. T' original kit has its aft centerin' rin' even with t' body tube. Begad! Avast, me proud beauty! Its centerin' rin' is 1/4" thick. T' Semroc rings are fiber board, so I glued 2 together t' increase the thickness. Aye aye! These rings glue t' t' motor tube 0.925" from t' aft o' t' tube. Begad! T' third rin' overlapped t' hook by about 1/2" from t' top. Ya scallywag! T' last rin' glued onto t' front end about 1/8" down.

While t' motor mount be drying, arrr, ya bilge rat, I worked on t' fins. Ya scallywag! Since t' enlarged win' fins are 6.388" long, I decided they should use through t' tube mounting. Arrr! 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. Ya scallywag! Ahoy! I drew tabs for t' difference between the ST-18 and t' ST-13, but t' motor used t' ST-9. Well, blow me down! Aye aye! My tabs were too short! 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, matey, wrapped it around t' ST-18 body tube and marked where they overlapped. Ya scallywag! I removed t' paper and measured its length. Avast! I divided t' length by 3 and by 4 and marked t' paper accordingly. Blimey! T' "by 3" marks indicated where t' wings and tail go, t' "by 4" indicated where the canards and launch lug belong. Blimey! I reapplied t' paper t' t' tube, me bucko, transferred t' marks, 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. Blimey! Blimey! I held t' win' and tail fins against t' body t' mark where t' cutouts would be required for t' tabs. Begad! Aye aye! Then usin' a new, arrr, sharp blade, me hearties, I cut out t' tab slots. Well, blow me down! I checked t' fit o' t' fins and then glued t' motor mount in with t' motor hook aligned with the tail line. Well, blow me down!

I again checked t' fins into t' slots and t' fit with t' motor tube. After me first error, I made t' tabs a little long and sanded them down t' fit, then glued t' wings and tail on. Blimey! After t' fins were dry, I added t' canards and launch lug. Avast! Once they were dry, me hearties, shiver me timbers, matey, I applied a glue fillet t' all t' joints. Blimey! 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. Begad! Aye aye! T' ST-13 tube got cut into 2 lengths each 5.088" long. 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 was a bit long for t' 1.85x upscale plus it be more pointy. I cut 1/4" off t' top and then sanded t' cone t' be more rounded and a better match t' t' original cone. Ya scallywag! A screw eye was installed t' tie t' shock cord to. Ahoy! I am goin' t' use a stock 18" chute that I have lyin' around.

Construction:
This was me first attempt at upscalin' a rocket. Well, blow me down! I did nay want anythin' too wild or difficult, but I wanted somethin' more than a 3FNC rocket. Ahoy! I finally decided on t' Starlight F-32 Avenger. Well, blow me down! Begad! 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. T' original kit uses 2 different size body tube, ya bilge rat, a BT-50 for the main tube and BT-20 for t' "engine nacelles". Avast, me proud beauty! Begad! After comparin' available tubes (and knowin' t' delivery speed which I needed since I procrastinated, again), I went with Semroc products. Begad! Well, arrr, blow me down! I replaced t' BT-50 with their ST-181120 (a 1.885x factor) and t' BT-20 be replaced with their ST-13105 tube (a 1.821x factor). Aye aye! I used t' average (1.85x) for all t' other dimensions. Blimey! T' longest size 18 tube is only 18" long. Blimey! Avast! I needed 22.2" for t' new body tube, so I ordered 2 o' t' 12" tubes plus an HTC-18 coupler. 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. Ya scallywag! Begad! 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, shiver me timbers, 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. Aye aye! I first used Krylon gray primer (I feel it has better fillin' properties and is better for sanding), sanded, ya bilge rat, then Krylon white primer, matey, and then finally 2 coats o' Krylon gloss white.

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

Flight:
I did a total o' 4 flights. Blimey! Begad! 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 was on an E9-4.

When I first went t' me local launch field (a school yard), I had t' turn around as t' field was in use. Ya scallywag! Blimey! Blimey! Blimey! After dinner, arrr, I returned t' t' field and it be empty. Ahoy! Blimey! I set up 2 launch pads (I was also flyin' t' original kit).

For t' upscaled version, me hearties, ya bilge rat, all flights were nice and straight. Ya scallywag! I was actually surprised that with t' large wing fins it did nay weathercock more, but then again t' winds were very light (<5mph). Arrr! Ahoy! T' D12-3 was just about perfect--the nose was just goin' down when t' chute would be ejected. For t' E9-4, arrr, 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. I had protected everythin' with a generous load o' dog barf. Begad! Ya scallywag! T' descent rate was good--nice soft landings. Begad! My only issue be t' field is shielded by some hills so at ground level where I launched there were no winds. Ahoy! Higher up it was a different story. Begad! I had a good hike through a weed field after t' E9 flight, but I got it back.

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