Scratch Rumble Bee Original Design / Scratch Built

Scratch - Rumble Bee {Scratch}

Contributed by Jack Anderson

Manufacturer: Scratch
(by Jack Anderson - 12/20/02)

Note: This is a slightly condensed version o' all the information that Jack has produced for his Level 3 project. Begad! Arrr! Visit his site t' read t' additional information and enjoy additional pictures.

PartsParts
T' picture t' t' left is most o' t' parts that I have purchased for this project. Arrr! Blimey! T' two big airframe tubes came from Eagle Hardware in t' cement section, they are t' same inner diameter as a PML 7.51 inch airframe and they sell for $3.85 each. They sell them for makin' cement pillars. Begad! Blimey! T' motor mount tubes came from All-Hobbies as did t' 7.51 inch couplers. Avast! Blimey! T' motor tubes are 75mm and 38mm. Ahoy! Blimey! Aye aye! Blimey! T' fiberglass and epoxy came from TAP Plastics in Bellevue, I have some 8.6 once cloth and some 1.4 once cloth. Arrr! Blimey! Aye aye! Blimey! T' nose cone is borrowed from me LOC Precision Bruiser. Ya scallywag! Blimey! T' centerin' rings and fins were special ordered from PML and had nay arrived yet when this picture was taken.

Airframe
T' first thin' I like t' do is get t' fiberglass on t' airframe. Avast, me proud beauty! Because I live in an apartment with no shop or garage, I do most o' me work in the kitchen. Aye aye! T' first step in fiber glassin' a tube is t' cut t' fiber glass cloth down t' t' approximate length that you will need. Avast, me proud beauty! Do this by rollin' the cloth around t' tube and markin' t' cloth, shiver me timbers, arrr, allow for some overlap o' the cloth. Ya scallywag! Begad! Once you have t' cloth cut, ya bilge rat, I like t' suspend t' airframe tube horizontally. Well, blow me down! Begad! Ideally you could run a 2 x 2 or a heavy dowel through your airframe and hang it across two saw horses. Avast! I have t' settle for a piece of speaker wire tied t' t' backs o' two chairs. Begad! I prefer usin' speaker wire over cord or rope because t' epoxy resign does nay soak into it and therefore it is easy t' untie and reuse. Avast! Ahoy! Once your air frame is suspended horizontally, mix up enough epoxy t' coat t' entire surface. Begad! T' resign that I used on this project was a 1 t' 1 mix and I used 3 ounces o' each part (6 ounces o' mixed epoxy). Then spread t' epoxy over t' entire surface o' t' tube. Blimey! Aye aye! T' photo above shows t' tube just before completin' this step. Avast! I use t' cheapest paint brushes I can find t' spread t' epoxy. Avast, me proud beauty! You can get a 1 1/2 inch wide brush for around $.50. Aye aye! You can try t' clean them with acetone in betwixt uses, arrr, but I just throw them out and use a new one each time.

FiberglassThe next step is t' apply t' cloth. I stretch it across t' top o' t' tube as in the picture. Then pat it down against t' wet tube and rotate t' tube as you go. Avast! You can work out t' wrinkles and air bubbles with your hands or you can use some type o' scraper or spatula. Well, blow me down! Some people like t' wear surgical gloves durin' this process, shiver me timbers, matey, me hands don't seem sensitive t' t' epoxy and I prefer to just use me bare hands. Blimey! O' course you will want t' have paper towels or a rag handy for when you complete this step.

After you have worked your way all t' way around t' tube you can trim the cloth near t' edges. There may be some places where t' cloth is still dry. Avast, me proud beauty! At this point I usually mix up a small amount o' epoxy and soak t' dry spots on the cloth and especially soak t' seam where t' fiberglass overlaps itself.

After your epoxy is thoroughly dry it should look somethin' like this. Arrr! The epoxy that you choose is very important. Ya scallywag! You don't want somethin' that will set up too smartly and cause you t' rush when workin' out t' air bubbles and wrinkles. Well, blow me down! On t' other hand you don't want t' wait for days in betwixt steps. T' epoxy that I bought actually set up a little too fast for t' size project that I am workin' on. Blimey! I had about 30 minutes from t' time that I mixed it until it was t' sticky t' work with. Begad! Fortunately I was able t' get everything finished before it set up. Well, blow me down! I always let me fiberglass cure for 8 or 9 hours before movin' t' t' next step. You don't want it t' be even t' slightest bit tacky.

After your epoxy is dry you need t' trim t' edges with an exacto knife or box cutter. Blimey! Blimey! Next sand t' entire surface o' t' tube. Most o' it can be a quick couple o' strokes. Begad! Blimey! T' edges o' t' tube and t' seam where t' fiber glass overlaps itself will need a little more attention. By sandin' t' edges o' the tube you trim off any fibers that may be stickin' up. Begad! Blimey! This is nay t' final surface and therefore does nay need t' be glassy smooth. Aye aye! Blimey! It fact with t' 8.6 ounce fiberglass that I used here that would be very unlikely. Begad! Blimey! You can clearly see and feel t' weave o' t' cloth still. Begad! Blimey!

FiberglassingOnce you have t' tube sanded, me hearties, it is time t' put it back it t' horizontal position. Arrr! At this point I mix up another batch o' epoxy and paint it on. Arrr! Begad! T' picture shows the tube just before finishin' this coat o' epoxy. Begad! Like before, shiver me timbers, arrr, you will want this t' dry for 8 or 9 hours before t' next step. Aye aye! Begad! Next is more sanding. Ahoy! I finally broke down and bought myself an orbital palm sander (best $30 I ever spent). Avast! This time you will want t' sand t' tube thoroughly. Aye aye! Ya scallywag! If you are only plannin' on one layer o' fiberglass, this will be your finish surface so you will want t' sand it with 100 grit paper t' take down any imperfections and then again with 220 or finer before painting. Begad! For this project I will apply a finish layer o' fiberglass on top o' this one.

After sandin' t' tube I get it ready for some more epoxy. Aye aye! This time the fiberglass that I am usin' is only 1.4 ounce cloth. Aye aye! It will cover up any pits from t' first layer. T' finer cloth is more difficult t' work with than the heavier weaves. Well, blow me down! It is more prone t' wrinkling, matey, ya bilge rat, but it sure gives you a nice surface. I follow t' same steps as before. Well, blow me down! Paint on t' epoxy and work the cloth as you rotate t' tube. Well, blow me down! I do make sure that t' seam from this layer is not t' same place as t' first, shiver me timbers, me hearties, just t' add a little strength and it helps to cover up t' first seam.

After applyin' t' finer layer o' fiberglass cloth, I sanded t' entire tube again after it had cured for 8 hours. Blimey! Next I applied yet another coat o' epoxy as I had done with t' first layer. After that coat o' epoxy was cured, I sanded t' entire surface o' t' tube with both 100 grit and 220 grit sand paper. T' total length o' t' rocket will be 9 foot 10 inches.

Motor MountWith FinMotor Mount
Here is a picture (right) o' t' motor mount assembly. Arrr! There is a central 75mm motor with two outboard 38mm motors. Arrr! I plan t' set things up so that t' 38mm motors can be air-started. In this picture I have epoxied t' top centering rin' and t' middle rin' in place, but t' bottom centerin' rin' is just in place t' align t' tubes (not epoxied yet). Blimey! I also used some fiberglass t' give additional strength t' t' motor mount assembly. Avast, me proud beauty! T' 38mm tubes are woven to the 75mm tube with fiberglass and t' top centerin' rin' is fiber glassed to the 75mm tube. Avast, me proud beauty! For t' picture I have inserted a 18 inch Dr.Rocket 38mm 1080 motor.

Here is a picture (left) with t' motor mount assembly inserted and the first fin in place. Ahoy! T' red wires that you see run from t' electronics bay to the aft o' t' rocket and will be used for air-startin' motors. As you can see the bottom centerin' rin' is now removed so that I have access t' t' fin tabs. I have pealed off t' inner layer o' paper from t' cement form tubes that I got at Eagle, because they have a wax coatin' on t' inside which would make the bond betwixt t' centerin' rings and t' airframe weaker. Arrr! Ahoy! Blimey! I have also cut slots into t' airframe so t' fins can slide through and attach t' t' motor tube. Avast, me proud beauty! T' fins are .093" G-10 fiberglass from PML. Arrr! Blimey! I use a piece of maskin' tape stretched from t' tip o' t' fin down t' t' airframe t' hold the fin where I want it while t' epoxy dries.

Ready to reinforceHere is a picture just before I begin reinforcin' t' fin joints. Ya scallywag! Blimey! Blimey! I have made a long handled paint brush (pictured) and cut six pieces o' fiberglass t' size. Aye aye! Ya scallywag! Blimey! The plan is t' paint t' full length o' t' motor mount tube, me hearties, matey, fin tab, arrr, and inside of t' airframe with epoxy and then usin' t' paint brush smooth t' fiberglass cloth inside t' rocket.

Electronics Bay
This picture (below-left) shows t' electronics bay on t' payload section of the rocket. Well, blow me down! Ya scallywag! There is a rectangle cut out from t' airframe, me bucko, right behind that is a coupler tube with a smaller rectangle cut out. Begad! Avast, me hearties, me proud beauty! T' piece that was cut out from t' airframe acts as a door t' seal off t' electronics bay when the rocket is in flight. Blimey! I will be usin' two altimeters durin' t' flight o' this rocket. Ya scallywag! First is an Olsen Electronics M-2 which is mounted inside the electronics bay on a piece o' plywood which is held in place with epoxy, me bucko, second is a Blacksky AltAcc which is mounted t' t' door o' t' electronics bay.

PrimedElectronicsTo make sure that the forces o' t' parachute openin' would nay pull t' bulkhead plate out o' the rocket, me bucko, arrr, I reinforced those attachments with fiberglass after usin' a standard fillet o' epoxy first. Avast, shiver me timbers, me proud beauty! T' fiberglass covers about 4 inches o' t' airframe above each bulkhead plate, me bucko, ya bilge rat, and also covers most o' t' bulkhead plate. There are two small holes in t' bottom o' t' bulkhead where t' wirin' from the deployment charges will eventually be routed into t' electronics bay.

T' aft centerin' rin' be cemented in place with epoxy. Aye aye! Six bolts which are anchored with T-nuts and will be used for positive motor retention. Ya scallywag! Arrr! There is a wirin' block which is wired t' t' second electronics bay where t' timer will be located for air-startin' t' 38mm outboard motors. Ya scallywag! T' second electronics bay will be located in t' coupler at t' top o' t' booster section o' the rocket, but is nay finished at this time. Begad! Well, blow me down!

Pictured (above-right), me bucko, be t' entire rocket with t' altimeter bay door open after t' first coat o' primer. I think I am goin' t' need a ladder at the launch pads t' activate those altimeters. So far with no motors and no parachutes, t' rocket weighs in at 21 pounds and is 9 foot 10 inches tall.

FinishedFinish
Here be t' finished painted project. Avast! I was plannin' on launchin' it on the Bonneville Salt Flats at Hellfire 6, but was unable t' ship it t' Utah because it be too big for UPS t' ship t' smallest section. Begad! Lesson learned : If you plan t' ship a rocket t' attend a launch out o' state, ya bilge rat, make sure it will fit into a box that can be shipped. Avast, me proud beauty! UPS will take a box as long as t' width + the height + t' depth = 130 inches or less. Ahoy! Aye aye! T' bottom half o' this one needs a box 20 X 20 X 57, me hearties, which is 7 inches too much for UPS. T' next cheapest shipper that I found wanted $205 t' send it, if it was 7 inches shorter UPS would have sent it for $23.

LEVEL 3 - PENDING FLIGHT

Date
Where
Rocket - Scratch Rumble Bee
Weight -
Motor -
Altitude


Lift-offLaunch
This be t' maiden launch o' t' Rumble Bee at Monroe Washington. Blimey! Avast! Blimey! T' motor I chose be t' biggest one allowed on this field... a K-700. T' Blacksky AltAcc2 altimeter that I used reported a maximum altitude o' 2916 feet. Well, blow me down! T' flight was perfect, straight and loud!

T' Rumble Bee as it descends on it's 44 inch PML drogue chute, me hearties, then the Rocketman R14C deployed t' brin' t' Rumble Bee down gently after it's first flight. I am already lookin' forward t' t' day I can brin' it out t' a bigger field and put an L-1120 in it. Ya scallywag! Blimey! Arrr! Blimey!

I be plannin' on flyin' it on an "L" motor at Hellfire in Utah on Sept. Begad! Blimey! 14, 2001. Arrr! Blimey! Aye aye! Blimey! But as we all know t' events o' Sept. 11, 2001 stopped all rocketry activity for awhile. Begad! Blimey!

I finally flew it on an "L" motor last summer at Hellfire 8 (Aug16, matey, shiver me timbers, 2002) usin' an Animal Motor Works Green Gorilla L1060 plus air starting two Aerotech Redline I366 motors about 1 second after lift off. Ya scallywag! Well, blow me down! T' effect was a green flame changin' t' orange and eventually pure red. Well, blow me down! I plan t' do me Level 3 flight next summer. Well, blow me down! Begad!

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