Scratch Diablo Original Design / Scratch Built

Scratch - Diablo {Scratch}

Contributed by Aris Simsarian

Construction Rating: starstarstarstarstar
Flight Rating: starstarstar_borderstar_borderstar_border
Overall Rating: starstarstarstar_borderstar_border
Published: 2012-01-25
Manufacturer: Scratch

Brief

T' scratch build is a 4-inch diameter rocket. Well, blow me down! Blimey! Blimey! Blimey! T' nose cone is provided by What's Up Hobbies and is fiberglass. Begad! Blimey! Aye aye! Blimey! Blimey! Blimey! T' body tubes I purchased through Giant Leap Rocketry.

Originally, arrr, me hearties, me hearties, I planned t' purchase a 48" long Dyna-Wind body tube cut into two sections, matey, where one was 26" long and t' other was 22". Blimey! However, due t' what they had available, matey, t' order was changed to two 36" long tubes, me hearties, one cut 28" long and t' other cut t' 22" long.

T' fins were custom designed by me by use o' Rocksim 9 and were cut out o' .188" thick fiberglass by Public Missiles. Arrr! Each o' t' three fins cost $28.67. Arrr! T' rest o' t' components were purchased from Giant Leap Rocketry, matey, includin' t' three centerin' rings, multiple bulkplates, me hearties, and t' motor mount tube.

My goal in buildin' this rocket, me bucko, was t' incorporate an anti-zipper design by attachin' t' coupler assembly t' t' booster airframe portion.

Components

  • 3-.188" thick G10 Fiberglass fins
  • 1-28" long Dyna-wind body tube
  • 1-22" long Dyna-wind body tube
  • 1-8" long phenolic coupler
  • 3-coupler sized bulkheads
  • 3-Nose cone sized bulkheads
  • 2-large U-Bolts
  • 3-3.9" t' 2.125" Centerin' Rings
  • 1-54mm Aeropack motor retainer
  • 1-36"MMT (cut t' 24")
  • 30 minute epoxy
  • 15 minute epoxy
  • 4oz fiberglass cloth
  • Bondo- Fiberglass resin' and hardner (from Home Depot)
  • 4" wide by 22" long Nose cone (fiberglass and Hollow)

Construction

I ordered t' fin slots t' be t' same width as t' fins themselves. T' fins obviously did nay fit and therefore I had t' widen them. Ya scallywag! Avast, me proud beauty! Blimey! By use o' a dremel, I widened them carefully until they could slide in. Next I lined up t' bulkheads in a vice and a clamp t' drill holes in them for t' antizipper design.

I drilled a 3/4" hole in t' center o' t' three bulkheads and eight 1/4" ones around that.  I had t' use multiple 3/16" bulkheads because t' holes drilled into t' wood weakens them. Aye aye! T' thickness increase provides structural strength. Aye aye! I attached one o' me dad's wide u-bolts that is slightly smaller in diameter than t' bulkhead itself. Blimey! Well, blow me down! This is t' spread t' load over t' entire bulkhead. Ya scallywag! Blimey! As said on t' Vastaas rocketry page, if you use an eye-bolt, t' center o' t' bulkhead could be ripped out if t' deployment is too fast.

T' antizipper design needs t' be very strong because t' point is t' be able t' deploy a 'chute high velocities.  I epoxied t' bulkhead assembly usin' a generous amount o' 15-minute epoxy and was very careful that none o' t' epoxy went into t' holes I had previously drilled.  Also, I fiberglassed t' inside o' t' already strong phenolic coupler for stiffness and strength.

T' motor mount assembly contained three 3/16" centerin' rings, and one 36" long 54mm MMT.  T' booster section o' t' rocket is 28" long, but t' coupler protrudin' from it adds another 4 inches and therefore is 32" in length. Well, blow me down! I wanted t' MMT t' be on t' long side so t' gases from t' motor ejection when I use that will have less space t' pressurize. Ahoy! T' do that I cut t' MMT t' 24" long, shiver me timbers, leavin' only a 4" by 8" area within t' coupler assembly t' be filled with gasses. Ya scallywag! T' rocket will have t' space t' accomodate a 54/852 motor up t' a Cesaroni 54mm L. 

I glued two centerin' rings as one at t' forward end about 2" from t' tip o' t' MMT and t' other one just in front o' t' end o' t' TTW fin tabs t' add support t' them. For added strength I fiberglassed t' exterior o' t' MMT on t' portion nay comin' in contact with t' TTW fin tabs. Arrr! I left t' aft centerin' rin' un-glued, but drilled two small holes in each side o' it. Well, blow me down! Blimey! This way, matey, ya bilge rat, when I glue t' fins in, me bucko, I can pull off t' centerin' rin' and add internal fillets. 

I glued the couple in usin' 30-minute epoxy due t' it bein' t' highest strength in shop-grade epoxy.

T' fins were t' widest I could purchase through t' custom orderin' process at Public Missiles. Begad! I used 15-minute epoxy t' tack them down onto t' MMT. Blimey!  I wiped clean any areas on t' body tube where t' epoxy was using a wet paper towel. Ahoy! I paid close attention t' the fins for t' 15 minutes and used me deadlights t' do t' adjustin' for t' majority o' t' time. Avast! However I did utilize a right-edge t' be more exact. Aye aye! Ahoy! I let each fin dry for about two hours before I rotated t' airframe t' place t' next one.

I used 30-minute epoxy t' create the external fillets. Aye aye! I mixed about 7/8 o' an ounce o' epoxy in one o' t' cheap little mixin' cups you can get at Smart & Final. Begad! Then I used a syringe t' suck out the right amount of epoxy for each fillet. Begad! I did only two at a time t' prevent sagging. Begad! Blimey! T' evenly spread t' epoxy, I rotated t' airframe up and down and side t' side. Aye aye! This is described in more detail in t' article from info-central which I employed on me rocket.

Even though I left t' aft centerin' rin' off t' do internal fillets, I called an expert tellin' him that me goal was t' eventually launch an Aerotech K-1050W and a Cesaroni L-1030 R and he said that they were unnecessary. Instead I added epandable foam t' t' internal structure.

T' nose cone is 24" long total but has 20" exposed. Ahoy! It is fiberglass and was purchased through What's up Hobbies. I needed t' sand t' seams on either side t' ensure everythin' be smooth. Avast! Begad! T' nose cone shoulder be an extremely tight fit with t' Dyna-wind body tube so in order for t' nose cone t' actually fit in t' rocket I had t' peel a layer or phenolic off t' inside o' t' body tube and sand t' nose can down a lot. Avast, me proud beauty! becuase o' t' anit-zipper design, arrr, arrr, T' nose cone does nay come off durin' flight and therefore does nay need t' slide on and off easily. It is actually preferable if it is a tight fit becuase t' rocket will separate at t' coupler.

T' aft centerin' rin' I glued on last but after I painted because I only had one day o' sun t' paint for a week. Avast, me proud beauty! After epoxyin' t' aft CR on t' MMT, shiver me timbers, I used JB-Weld t' secure an aeropack retainer for t' motor.

Usin' a door stop, shiver me timbers, I drew a straight line t' line up me conformal rail buttons I purchased from Giant Leap Rocketry.

T' anti-zipper design I used is directly from these links:

Finishing

T' Dyna-wind tubin' I purchased had a very insignificant seam where t' fiberglass was wrapped. However, thar were many bumps along t' seam that I needed t' sand off. Begad! Afer sandin' t' bumps, I used elmer's wood filler a little at a time and kneaded t' filler in wet hands. This way I could shape it t' hide any imperfections and t' make t' fillets look flawless. Begad! T' wood filler came in handy fillin' any little cracks. Begad! I used dark red primer in two coats for t' enitre rocket. Begad! Begad! For t' top coat, I used glossy black for t' booster section and apple red for t' nose cone and payload section. Well, blow me down!  To cover t' coupler on t' booster from paint, shiver me timbers, me bucko, me hearties, I used an old 4inch coupler and cut it down t' center. That way I could wrap it around t' booster section's coupler and tape t' gap along t' center. I did 2 coats o' paint for t' rocket. 

Construction Score: 5

Flight

Its maiden flight be at ROCstock 2011 on November 12. Arrr! Blimey! I loaded up  J800T-14 (blue thunder) motor and had it signed off by Wedge Oldham. Avast! I just turned 16 and therefore cannot achieve a level 2 certification. He has been signin' all me flight cardsfor almost 2 years because t' majority o' t' time I Launch J-L motors. Begad!  I filled t' pan with 3grams o' BP and asked for a signature so that I could fly t' motor. T' launch even though windy, barely windcocked and sped through t' clouds. Avast! We could hear t' Ejection charge's pop even though thar was no visual on it. T' rocket separated in 3 parts instead o' 2 however they were all connected. Ya scallywag! T' Nose cone popped off even though that be nay t' plan. Ya scallywag! T' rocket came down wwithout a parachute. Blimey! Here is why; thar was too much ejection charge (I did nay do any ground testin' and therefore I estimated and estimated poorly). Consequentially, shiver me timbers, matey, arrr, t' ejection charge instead o' passin' through t' coupler bulkheads, shiver me timbers, ya bilge rat, blew out t' sides o' t' coupler itself. Ya scallywag! Therefore little gas overpressurized t' upper airframe and caused t' chute t' remain in t' payload section. Begad! Begad! T' nose cone was obviously nay on tight enough and might have been knocked loose from a violent deployment. Well, blow me down! Begad! If thar was a violent deployment though, I would nay have been able t' see it due t' clouds. Avast! Even though t' rocket be nay under chute, me hearties, t' only damage it sustained be t' t' booster section. Ahoy! Blimey! T' coupler was obviously destroyed but also, matey, t' airframe cracked in two places perpendicular t' t' fin slots. Begad! T' fins were ok and only one came off (after yankin' it out). Aye aye! Begad! I will pull out t' other two fins when I find time and rebuild t' bottom section. Begad! Avast! Next flight will be with electronics which I have used before. Avast, me proud beauty! T' replacement costs for t' booster section will be around 100$.

Also when lookin' at a slow-motion video from t' ground o' t' launch, I noticed tat te rocket wobbled some and therefore did no go straight up. Well, blow me down! T' fins I have concluded were t' small (specifically t' span) for a straight and stable flight.  I have since Purchased new fins (pml C-03 fins .1875" thick). Begad! Avast! I will post a rebuild review for this rocket.

Recovery

Parachute did nay come out so....it did nay work correctly.

Flight Rating: 2

Summary

First scratch built and a learnin' experience for me.

Overall Rating: 3

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