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. Well, blow me down! Blimey! 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. Avast! 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. Ahoy! T' motor mount tubes came from All-Hobbies as did t' 7.51 inch couplers. Ya scallywag! Ya scallywag! T' motor tubes are 75mm and 38mm. T' fiberglass and epoxy came from TAP Plastics in Bellevue, me hearties, I have some 8.6 once cloth and some 1.4 once cloth. Ya scallywag! T' nose cone is borrowed from me LOC Precision Bruiser. Begad! 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. Ya scallywag! Ya scallywag! Because I live in an apartment with no shop or garage, shiver me timbers, I do most o' me work in the kitchen. Begad! T' first step in fiber glassin' a tube is t' cut t' fiber glass cloth down t' t' approximate length that you will need. Begad! Do this by rollin' the cloth around t' tube and markin' t' cloth, allow for some overlap o' the cloth. Well, blow me down! Once you have t' cloth cut, I like t' suspend t' airframe tube horizontally. Ahoy! Ideally you could run a 2 x 2 or a heavy dowel through your airframe and hang it across two saw horses. I have t' settle for a piece of speaker wire tied t' t' backs o' two chairs. 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. Once your air frame is suspended horizontally, arrr, shiver me timbers, mix up enough epoxy t' coat t' entire surface. 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. T' photo above shows t' tube just before completin' this step. Begad! I use t' cheapest paint brushes I can find t' spread t' epoxy. Well, blow me down! You can get a 1 1/2 inch wide brush for around $.50. You can try t' clean them with acetone in betwixt uses, me bucko, ya bilge rat, but I just throw them out and use a new one each time.

FiberglassThe next step is t' apply t' cloth. Ahoy! I stretch it across t' top o' t' tube as in the picture. Blimey! Then pat it down against t' wet tube and rotate t' tube as you go. Ahoy! You can work out t' wrinkles and air bubbles with your hands or you can use some type o' scraper or spatula. Blimey! Arrr! Some people like t' wear surgical gloves durin' this process, me bucko, me hands don't seem sensitive t' t' epoxy and I prefer to just use me bare hands. 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. Well, blow me down! Arrr! Blimey! There may be some places where t' cloth is still dry. Begad! Ya scallywag! Blimey! 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! Ahoy! The epoxy that you choose is very important. Avast, me proud beauty! You don't want somethin' that will set up too smartly and cause you t' rush when workin' out t' air bubbles and wrinkles. Avast, me proud beauty! 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. Arrr! Begad! I had about 30 minutes from t' time that I mixed it until it be t' sticky t' work with. Fortunately I was able t' get everything finished before it set up. I always let me fiberglass cure for 8 or 9 hours before movin' t' t' next step. Begad! Ahoy! 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. Ya scallywag! Most o' it can be a quick couple o' strokes. Well, blow me down! T' edges o' t' tube and t' seam where t' fiber glass overlaps itself will need a little more attention. Blimey! By sandin' t' edges o' the tube you trim off any fibers that may be stickin' up. Well, blow me down! Ya scallywag! This is nay t' final surface and therefore does nay need t' be glassy smooth. Arrr! Begad! It fact with t' 8.6 ounce fiberglass that I used here that would be very unlikely. Well, blow me down! You can clearly see and feel t' weave o' t' cloth still. Aye aye!

FiberglassingOnce you have t' tube sanded, it is time t' put it back it t' horizontal position. At this point I mix up another batch o' epoxy and paint it on. Well, blow me down! Blimey! T' picture shows the tube just before finishin' this coat o' epoxy. Ahoy! Avast! Like before, me bucko, you will want this t' dry for 8 or 9 hours before t' next step. Avast, me proud beauty! Next is more sanding. Well, blow me down! I finally broke down and bought myself an orbital palm sander (best $30 I ever spent). This time you will want t' sand t' tube thoroughly. Well, blow me down! 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. Avast, me proud beauty! 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. Arrr! This time the fiberglass that I am usin' is only 1.4 ounce cloth. Avast! It will cover up any pits from t' first layer. Arrr! Well, blow me down! T' finer cloth is more difficult t' work with than the heavier weaves. Ya scallywag! It is more prone t' wrinkling, but it sure gives you a nice surface. I follow t' same steps as before. Begad! Begad! Paint on t' epoxy and work the cloth as you rotate t' tube. Ahoy! I do make sure that t' seam from this layer is not t' same place as t' first, shiver me timbers, just t' add a little strength and it helps to cover up t' first seam.

After applyin' t' finer layer o' fiberglass cloth, me bucko, I sanded t' entire tube again after it had cured for 8 hours. Next I applied yet another coat o' epoxy as I had done with t' first layer. After that coat o' epoxy be cured, I sanded t' entire surface o' t' tube with both 100 grit and 220 grit sand paper. Well, blow me down! 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. Begad! Blimey! There is a central 75mm motor with two outboard 38mm motors. Begad! Blimey! Aye aye! Blimey! I plan t' set things up so that t' 38mm motors can be air-started. Avast, me proud beauty! Blimey! Aye aye! Blimey! In this picture I have epoxied t' top centering rin' and t' middle rin' in place, arrr, but t' bottom centerin' rin' is just in place t' align t' tubes (not epoxied yet). Aye aye! Blimey! I also used some fiberglass t' give additional strength t' t' motor mount assembly. Well, blow me down! Blimey! T' 38mm tubes are woven to the 75mm tube with fiberglass and t' top centerin' rin' is fiber glassed to the 75mm tube. 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. Ya scallywag! 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. Avast! Ya scallywag! 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. Avast! I have also cut slots into t' airframe so t' fins can slide through and attach t' t' motor tube. Arrr! T' fins are .093" G-10 fiberglass from PML. Aye aye! Ahoy! 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. Avast, me proud beauty! Blimey! Arrr! Blimey! I have made a long handled paint brush (pictured) and cut six pieces o' fiberglass t' size. Avast! Blimey! The plan is t' paint t' full length o' t' motor mount tube, fin tab, ya bilge rat, me bucko, 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. Avast, me proud beauty! There is a rectangle cut out from t' airframe, shiver me timbers, ya bilge rat, right behind that is a coupler tube with a smaller rectangle cut out. 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. Ahoy! I will be usin' two altimeters durin' t' flight o' this rocket. 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, 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, I reinforced those attachments with fiberglass after usin' a standard fillet o' epoxy first. T' fiberglass covers about 4 inches o' t' airframe above each bulkhead plate, and also covers most o' t' bulkhead plate. Begad! Begad! 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' was cemented in place with epoxy. Ya scallywag! Six bolts which are anchored with T-nuts and will be used for positive motor retention. 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. 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.

Pictured (above-right), me hearties, be t' entire rocket with t' altimeter bay door open after t' first coat o' primer. Avast, me proud beauty! 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, ya bilge rat, t' rocket weighs in at 21 pounds and is 9 foot 10 inches tall.

FinishedFinish
Here be t' finished painted project. I was plannin' on launchin' it on the Bonneville Salt Flats at Hellfire 6, me hearties, but was unable t' ship it t' Utah because it be too big for UPS t' ship t' smallest section. Lesson learned : If you plan t' ship a rocket t' attend a launch out o' state, make sure it will fit into a box that can be shipped. Begad! Ahoy! UPS will take a box as long as t' width + the height + t' depth = 130 inches or less. Avast! T' bottom half o' this one needs a box 20 X 20 X 57, shiver me timbers, arrr, which is 7 inches too much for UPS. T' next cheapest shipper that I found wanted $205 t' send it, arrr, if it be 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. Avast, me proud beauty! T' motor I chose be t' biggest one allowed on this field... a K-700. Well, blow me down! T' Blacksky AltAcc2 altimeter that I used reported a maximum altitude o' 2916 feet. T' flight was perfect, matey, ya bilge rat, straight and loud!

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

I be plannin' on flyin' it on an "L" motor at Hellfire in Utah on Sept. Begad! Well, blow me down! 14, shiver me timbers, 2001. Aye aye! Begad! But as we all know t' events o' Sept. 11, shiver me timbers, matey, 2001 stopped all rocketry activity for awhile. Avast!

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

comment Post a Comment