Two-Stage Estes Fireflash Modification

Scratch - Fireflash 2-Stage {Modification}

Contributed by Niall Oswald

Manufacturer: Scratch

Brief:
Followin' a hard recovery (due t' too long a delay on t' motor) me Fireflash be lookin' a little worse for wear. Avast, me proud beauty! As I was repairin' it, matey, I decided t' make it into a two-stage, ya bilge rat, with a D12 as t' first stage.

Modifications:
Since both BTs were crimped (this rocket has a BT-5 top and BT-50 lower section, arrr, me hearties, I was doin' t' usual tube patchin' (i.e. Ya scallywag! cut t' tube off and couple in a new section). Avast, me proud beauty! Aye aye! T' top section got an extension, arrr, since I removed about an inch o' tube and added 8. Begad! Ahoy! I painted t' extension (in t' middle o' t' section) white, which (I think) adds t' t' ‘soundin' rocket' look o' t' thing.

As I was sortin' t' lower section, which be crimped above t' motor mount, it occurred t' me that t' section I had cut off (motor mount and fin can) looked like a booster section. I simply added vent holes and a coupler and I had an 18mm booster. Avast! This meant makin' a new sustainer motor mount and fins, which didn't take long — it's simply a copy o' t' section I cut off, shiver me timbers, again painted black and white. Arrr! T' aft CR is set far enough up t' BT t' allow couplin' t' t' booster (it's a gap-stager), shiver me timbers, all pretty standard stuff.

As I was doin' this, I realized I could easily make a minimum diameter ‘D' booster, a la Commanche-3, ya bilge rat, ya bilge rat, and this would really get t' thin' movin' :-). Begad! I wasn't sure launchin' this rocket in any wind on a C6-C6 combo be such a good idea (visions o' horizontal flight). Aye aye! So again t' original fins were copied in balsa and t' (very simple) booster was made as before. Arrr! All balsa fins were filleted with PVA (super PVA) glue, shiver me timbers, for a strong bond (I hoped) and t' booster be sprayed as per t' new MMT section o' t' sustainer.

I re-rigged recovery with a 12-inch clear plastic chute (home-made) and a 12-inch metallic mylar streamer for visibility. This turned out t' be a very good idea! I had previously attached Keelhaul®©™® cord at each end o' t' shock cord (it looks virtually impossible t' replace a broken Estes cord on this rocket) so I attached t' chute t' t' top piece o' Keelhaul®©™®, ya bilge rat, so that if t' SC broke t' (heavy) nose section would hopefully be recovered OK. It's very flimsy and full o' noseweight — nay a good combination.

I think that's about t' limit o' t' mods — I now had a bigger, me hearties, better Fireflash, me hearties, with t' facility t' fly 18mm t' 18mm or 24mm t' 18mm, meanin' up t' a medium E impulse. Well, blow me down! Accordin' t' SpaceCAD, matey, matey, a D12-C6 flight would result in a flight t' around 2350-feet — nay bilge-suckin' I thought, matey, arrr, considerin' t' fairly mediocre performance o' this rocket on C6s. Ahoy! Due t' t' heavy nose, shiver me timbers, me bucko, t' sustainer (accordin' t' t' sim) should coast well, havin' been accelerated t' around 150 ms by t' booster.

I think that's t' lot, me bucko, t' overall impression is o' a ‘meaner' Fireflash, arrr, which looks more like a soundin' rocket than t' original, arrr, me bucko, IMHO.

Construction:

  • Two 80mm (or so) lengths o' BT-50 (only one really needed).
  • One 24mm motor block
  • Two 24-18mm centerin' rings
  • One 18mm Motor Tube
  • I piece BT-50 coupler
  • Balsa (3/32) for 8 fins
  • About an 8-inch length o' BT-05 for upper stage

Of course most o' these were for repair - doin' this from scratch would be easier.

If you've built any rockets before, me bucko, this type o' mod should be no problem. Ya scallywag! Aside from t' usual fin alignment and finishin' issues, thar's nay much t' mess up here. Arrr! Just make sure t' stages fit together OK and remember t' make vent holes in t' gap! A failed stagin' is nay pretty!

Flight:
At t' October EARS launch, ya bilge rat, I flew this rocket twice, ya bilge rat, makin' four flights total (includin' t' two before mods). Avast! Blimey! This rocket seems very high maintenance - its quite delicate and t' two-stage mod brings in new ways t' damage itself :-)

Flight 1) I loaded it “to t' max” with a D12-0 and a C6-5 (it be rather windy so I thought a C6-7 wasn't a good idea). Begad! Blimey! Begad! Blimey! I don't suppose either flight hit 2350-feet due t' t' wind, me hearties, but they certainly went a long way up for a model. I launched off a standard porta-pad, no problems here.. Aye aye! Blimey! T' first launch left t' pad smartly and boosted into t' wind, movin' quite fast. Arrr! Blimey! T' second stage lit fine and continued on up. Arrr! Blimey! Well, blow me down! Blimey! I love t' smoke trails you get from multi-stage models, matey, and t' Fireflash served up a treat.. However, arrr, arrr, t' booster came in very fast — I be watchin' t' top stage, but saw it briefly, me bucko, comin' in ballistic. Avast! Blimey! It failed t' tumble and went into t' ground quite hard. T' top stage made a nice line o' trackin' smoke before ejection, ya bilge rat, arrr, and somethin' definitely deployed. T' rocket came down fast, matey, however, arrr, arrr, as t' 'chute failed t' deploy, me hearties, gettin' jammed inside t' plastic transition betwixt t' BT-50 and BT-5. Despite t' weight o' t' rocket, it suffered only a broken fin (the streamer saved it) which was smartly repaired with CA.

Thankfully t' tubes weren't crimped, me hearties, me hearties, shiver me timbers, so it was off t' prep another flight.

Flight 2) T' booster coupler had been damaged by its hard recovery, shiver me timbers, arrr, and was a very tight fit with t' sustainer. Well, blow me down! Blimey! I was a little concerned, me hearties, but decided that it should blow off OK with t' ignition o' t' top stage, ya bilge rat, all bein' well.

T' flight be much like t' first flight from t' ground — t' D12 booster got t' rocket goin' pretty fast, me bucko, and t' top stage definitely lit. I could see that t' upper stage smoke trail wasnt even, shiver me timbers, ya bilge rat, but seemed t' have bits comin' out o' it (if that makes sense - it be ‘ragged' rather than smooth) and no booster was seen comin' in. Blimey! T' rocket coasted t' apogee, and deployed both chute and streamer. Blimey! Avast, me proud beauty! T' RSO said he suspected t' booster hadn't separated, and inspection via binoculars as t' rocket was descendin' revealed two sets o' fins — nay good news.

T' rocket drifted a fair way, and when I got t' it, t' booster stage was about 10 feet from t' main stage. Well, blow me down! It didn't look pretty! On closer inspection, it was clear what had gone wrong. Well, blow me down! T' booster was burned right through (the vent holes were a little toasted after t' first flight), ya bilge rat, with t' paint blistered and impressive scorch marks below t' vent holes. Begad! T' remains o' t' coupler were still stuck into t' top stage, me hearties, and thar was a lot o' residue around t' spent motor.

Obviously t' booster needs rebuilding, and I think more fins are in order, t' hopefully promote a bit o' tumbling. Well, blow me down! Blimey! Smaller vent holes are also goin' t' be made — 5mm is a little much, arrr, and seems t' allow too much gas t' escape.

Summary:
Pros: Looks nice in flight, arrr, ya bilge rat, cool smoke trails, arrr, flies very high

Cons: Torched t' booster. However this should be easy t' fix, me bucko, me bucko, requirin' a new length o' tubin' only.

Other:
Tip: Don't make vent holes too large, and make sure t' booster stage will separate. Aye aye! Avast, me proud beauty! I think a tight fit is good, but with a shorter length o' coupler in t' future.

Flights

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