Scratch V2 Original Design / Scratch Built

Scratch - V2 {Scratch}

Contributed by Brian Kain

Manufacturer: Scratch
(Contributed - by Brian Kain)

Brief:
Scratch 4" V-2. Avast, me proud beauty! Flies on H through J 38mm motors. Avast! T' nose has interchangeable weights so t' rocket can be properly weighted for any given motor. Arrr! Blimey! I use a silk 36" chute I got from AEROCON.

Construction:

  • 1- 4" dia LOC body tube 8.5" long. Glassed with 6oz cloth and 30 min epoxy. Begad! This rocket has no payload section but one can be added inside the nose cone. Avast, me proud beauty!
  • LOC 4" NC for t' nose
  • 4" PML NC for t' boat tail, arrr, which is cut t' 11.5" exposed length. Begad! Aye aye!
  • 4 fins made from 3/16" 4 ply plywood, me hearties, also glassed with 6oz.
  • 1- 3/16" 54mm centerin' ring, me bucko,
  • 2- 3/16" 4" centerin' rings. Begad! Blimey!
  • All rings have a 38mm hole and are birch plywood.
  • 14" 38mm LOC motor mount.
  • 3/8" strap Keelhaul®©™® for shock cord. 2 pieces o' this form t' harness that mounts t' 2- 1/4" by 3/4" u-bolts, which are located on t' top CR o' t' MMT. Avast, me proud beauty! There is 20' o' Keelhaul®©™® from thar t' t' nose cone, me hearties, which mounts in a similar fashion t' 2- u-bolts mounted on a bulkhead inside o' t' nose cone. Ahoy! Blimey!

Nose Cone:
This be t' most complex area o' t' rocket. Begad! Blimey! I cut t' shoulder off o' t' LOC NC t' 2.5". Blimey! Blimey! I sanded t' tip o' t' NC flat and drilled a 1/4" hole in t' tip. I took 15.5" o' stainless steel 1/4" allthread and ran that through t' hole. Begad! Blimey! Before that I used a small 1/4" washer and 1/4" nut and secured that about 2" from t' tip o' t' allthread. Then inserted t' allthread from t' shoulder side o' t' NC through t' hole in t' tip. Avast, me proud beauty! Blimey! That gave me 1" exposed through t' tip. I used another 1/4" washer and nut and secured t' allthread tight at t' tip. Ahoy! Blimey! Then took some 1/4" fender washers which are about 1.3" dia and slipped them down t' allthread from t' shoulder side. I got some round/flat lead fishing weights in various weights rangin' from 3 t' 5 oz, me hearties, me bucko, drilled 1/4" holes through t' center, slip those down t' t' big washers, put another big washer on top o' t' weights and then used a 1/2" stainless steel tube about 8" long t' push down on t' weights. Ya scallywag! Blimey! Avast! Blimey! I used a bulk head with t' same fender washers on each side, matey, put that over t' tube and secured t' bulk head with a 1" section o' 1/4" coupler. Arrr! Blimey! All metal parts are stainless steel. Ya scallywag! Blimey! Ya scallywag! Blimey! There are two u-bolts on t' bulk head for recovery harness attachment. Begad! Blimey! Aye aye! Blimey!

I can change t' rockets weight in under a minute. Begad! T' only problem was the allthread stickin' out o' t' tip o' t' NC. Blimey! I was goin' t' fake it out with glass and epoxy, me bucko, but since I had cut t' tip off t' PML NC for t' boat tail, I had a perfect tip t' put over t' allthread. I took an extra piece of allthread, ya bilge rat, put a nut on it and heated it up with a torch. Then took t' tip of the PML NC and sunk it into t' HOT nut that was on t' allthread. Blimey! Ya scallywag! This worked out better than I had hoped. I now had a tip that I can screw onto the allthread, and I finished it off with sand paper t' make a perfect fit.


Rocket Pic
Rocket Pic
Rocket Pic
Rocket Pic
Rocket Pic
Rocket Pic

This is a complex rocket with way too many gotcha's. Avast, me proud beauty! Avast, me proud beauty! First off I had t' cut the 3/16" slots down t' boat tail. Well, blow me down! This was nay easy. Well, blow me down! Arrr! Actually it was, but gettin' t' lines straight was hard. Well, arrr, blow me down! I used a dremel tool with extension. One fiberglass cuttin' wheel sandwiched with three small cuttin' wheels on each side o' that gave me t' 3/16" needed for t' fins. Arrr! After I got t' lines straight I followed them with t' cuttin' jig makin' perfect 3/16" slots in one shot. Well, blow me down! Construction o' t' nose cone was a bit hard also. Begad! See above description for details. Everythin' fit nice and t' rocket is very sturdy.

Rocket Pic

Flight:
Any 38mm H motor will send this guy up nice. Aye aye! I haven't tried t' J-570 yet, me hearties, but I think it will handle it fine. I chose t' H-242 for it's first flight. Avast! Aye aye! I used a stainless steel pot scrubber for a baffle inside t' MMT. Well, blow me down! I used some small allthread epoxied into t' back centerin' rin' with a custom bracket with nuts and washers for retention. Ya scallywag! T' rocket flew very straight on t' H-242. I just stuffed t' cord into t' airframe with t' chute and connected t' harness with 3/16" quick links. Ahoy! T' rocket be recovered about 900' from t' pad with no damage at all. Aye aye! Deployment occurred around apogee.

Summary:
Pro's..... A very fun and challengin' rocket t' build. Avast, me proud beauty! Well, matey, blow me down! It looks nice too. I love those V-2's. Con's..... Price. Ahoy! T' nose cones were $14.00 each. 4" BT $5.00. Ya scallywag! Arrr! 3/16" birch fin material $4.00 with extra left over. Aye aye! 38mm MMT $3.00. Baffle $2.00. Keelhaul®©™® $22.00 for 100'. Begad! 3 feet o' 1/4" stainless steel allthread $4.50 Stainless washers and nuts $5.00. Lead fishin' weights $4.00. Ahoy! Fiberglass 6oz $5.00. Well, blow me down! Epoxy $3.00. Begad! Avast, me hearties, me proud beauty! Chute $8.00. Arrr! Avast, me bucko, me proud beauty! Quick links $4.00. Ahoy! That brings t' total t' around $80.00, arrr, but I had enough BT t' make 2 more V-2's and some other stuff left over as well.

Other:
One good tip..... Ahoy! It is very hard t' cut slots in t' boat tail without a vertical mill or some other tool or custom jig.

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