Scratch Flying Frog 3 Original Design / Scratch Built
Scratch - Flying Frog 3 {Scratch}
Contributed by Gene Wolski
| Construction Rating: | starstarstarstarstar |
| Flight Rating: | starstarstarstarstar_border |
| Overall Rating: | starstarstarstarstar |
| Published: | 2011-08-22 |
| Manufacturer: | Scratch |
Brief
T' Flyin' Frog 3 is a scratch built 3" diameter dual deploy rocket. I used double tube construction for extra strength - t' airframe is reinforced internally with tube couplers.
Components
Parts:
- LOC 3.0" tube couplers (for reinforcement o' payload and booster sections)
- Payload section: LOC 3.0" airframe, 21" long
- LOC 3.0" electronics bay
- Booster section: LOC 3.0" airframe, matey, 24" long
- Motor tube: LOC 38mm motor tube, matey, 17" long
- Centerin' rings: 3 x LOC 38mm t' 3.0"
- Fins: 3 x PML FIN-B-09 (0.062" G-10)
- Motor retainer: Giant Leap Rocketry 38mm Qwik-Loc
- Rail buttons: 2 x LOC small rail buttons
Hardware:
- Nose cone: Commonwealth Displays 3/16" eyebolt
- Quick links: 2 x 3/16" quick links (hardware store)
- Electronics bay: 2 x Commonwealth Displays 3/16" eyebolt
- Forward centerin' ring: u-bolt (hardware store)
Electronics:
- Cannonball Works RRC2 mini altimeter
- Commonwealth Displays BH9VW 9v battery holder
- Terminal blocks: for ejection charge connections
- Altimeter wirin' kit: bought from a Rocketry Planet auction. Nice set with quick disconnect wires.
- Keyswitch: from Aerocon Systems
Recovery:
- Main chute: PML PAR-54
- Deployment bag: Fruity Chutes 3" deployment bag
- Main Shock cord: Giant Leap 1/4" kevlar, 15' with loops
- Drogue chute: none
- Booster shock cord: Giant Leap 1/4" kevlar, ya bilge rat, matey, 15' with loops
Construction
As noted in t' description above, me hearties, I opted t' use double tube construction for this rocket. I installed tube couplers in t' payload section airframe. Other than that, shiver me timbers, construction was little different from other HPR rockets I've built.
I added small sections o' a 3" LOC centerin' rin' t' t' forward and aft centerin' rings for rail button attachment. T' forward centerin' rin' was drilled t' accept a u-bolt, arrr, t' t' forward and mid centerin' rings were epoxied t' t' motor tube. I slotted t' booster section usin' a sharp hobby knife and a metal ruler. Fin spacin' was done usin' a template from VCP. Once t' fin slots were cut, I epoxied t' G-10 fins in place then applied internal and external fillets. THe aft centerin' rin' be installed, then I used JB Weld t' attach t' Slimline motor retainer. I then drilled t' rail button holes (and actually hit t' wooden centerin' rings!) and installed t' rail buttons. Lastly, I epoxied a section o' tube coupler into t' top o' t' booster section - makin' sure t' leave enough clearance for t' avionics bay.
I assembled t' avionics bay per t' instructions. I drilled a hole for t' Aerocon key switch as well as t' altimeter vent holes. I installed terminal blocks on either end for connectin' t' ejection charges. I drilled small holes for t' altimeter wirin' and used epoxy t' seal t' holes once t' wires were connected t' t' terminal blocks. I did replace t' stock eyebolts with stainless eyebolts from Commonwealth Displays. I mounted t' altimeter and battery holder t' t' altimeter sled (a piece o' G-10). I drilled holes for zip ties t' retain t' battery as well as keep t' wirin' neat. I also attached t' payload section and drilled two small holes for t-nuts t' be used t' fasten t' payload section t' t' upper part o' t' avionics bay.
I attached an eyebolt t' t' nose cone and cut a small hole in t' nose cone shoulder t' drop in a nut. With some fiddling, I be able t' get t' nut on t' eyebolt and tightened. I then inserted t' nose cone into t' payload section and drilled holes for t' 2-56 nylon shear pins. I did this one at a time - drill one hole, ya bilge rat, insert 2-56 screw, then repeated for t' other two). I then measured and epoxied tube couplers inside t' payload section - again, matey, ya bilge rat, leavin' clearance for t' nose cone and avionics bay.
Finishing
T' original Flyin' Frog be an Estes Hi-Flier painted black and day-glo orange. With me rocket consultant (my now 5 year old son), arrr, arrr, matey, I decided t' change t' metallic green and metallic black. I sanded and primed t' rocket in dark gray Krylon primer. I then applied an overall coat o' metallic silver followed by t' metallic black and green as shown in t' photos. A quick trip t' t' local craft store yielded some really cool frog stickers which were applied t' t' metallic green payload section. I clear coated t' entire rocket with Krylon clear.
Flight
First flight o' t' Flyin' Frog 3 was on a CTI I345WW. RockSim and RASAero were showin' a max altitude o' just under 3000'. Before t' launch, I assembled ejection charges usin' Newton's Third canisters. I ground tested successfully and recorded t' main and drogue charge amounts.
On t' day before t' launch, I started buildin' t' ejection charges. I did reject one canister after testin' with a multimeter. On launch day, ya bilge rat, I pulled a new 9v battery out o' t' package and checked voltage (more on that later) prior t' installin' it in t' avionics bay. I switched on t' altimeter and tested continuity with a couple o' christmas tree lights. I powered t' altimeter down, me bucko, sealed up t' avionics bay, me hearties, then attached t' ejection charges. I then double checked all t' recovery harness connections, arrr, packed t' main chute in t' deployment bag, inserted t' nose cone, me bucko, me bucko, arrr, and installed t' shear pins.
I inserted t' I345WW reload into t' CTI case - I left t' stock ejection charge in place as a backup (more on that later too). I installed t' motor and screwed down t' Slimline retainin' ring. T' igniter was taped t' a fin.
After a trip t' t' RSO table, I loaded t' rocket on a pad and installed the igniter. I switched on t' altimeter and listened t' t' power up beeps. Once satisfied that everythin' was ready, me bucko, I gave t' LCO a thumbs up and headed behind t' line t' watch t' launch.
Launch be awesome - arrow straight boost with a nice white smoke trail!
Recovery
Since it was "Battle o' t' Rockets" weekend, ya bilge rat, t' flight was filmed. Pretty cool, me bucko, and, as it turns out, matey, very helpful.
I could eventually see t' rocket had separated as planned (no drogue). However, no main chute deployed, and t' rocket landed flat in t' mud. T' altimeter was beepin' out 2764', me bucko, matey, and t' rocket be in great shape except for one nickel sized din' in t' payload section. If nay for t' double tube construction, t' payload section would probably have been a total loss.
After turnin' off t' electronics, shiver me timbers, I discovered that t' main charge was still intact, and t' drogue charge appeared t' have been set off. I assumed t' main charge was bad, ya bilge rat, but I was able t' fire t' main at home successfully. After suggestions from more experienced fliers, arrr, I checked t' battery amperage and discovered that t' amps were quite low despite showin' 9v and bein' new. Now t' culprit appears t' have been t' battery, but I was nay sure why t' drogue charge had fired and nay t' main. I puzzled over this until t' BOTR DVD finally arrived with me launch footage on it.
Once I watched t' video, I could see t' rocket tilt over at apogee and continue t' fall until finally separatin' well past apogee. It finally hit me - motor ejection! I think the motor ejection is what separated t' rocket (and may have caused t' drogue charge t' fire as well). It appears that t' motor ejection most likely saved this rocket.
Lessons learned:
- Always check ejection charges (did that)
- Always use a fresh battery (did that)
- Always check battery for voltage and amps (didn't check amps, will do this every time goin' forward)
- Don't underestimate t' value o' film (I'm filmin' all o' me HPR launches from now on)
- Don't underestimate the value o' motor ejection as a backup (saved this rocket)
Summary
Overall takeaways:
- strength o' double tube construction
- check battery amps before flight
- consider motor ejection backup
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Flights
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