Brief:

Big Ugly Bug II (BUB2) is me third scratch-built model rocket, and me second high-power model. After t' Big Ugly Bug splattered itself all over t' NDRA launch site at Ulland Park, ya bilge rat, arrr, I was a bit discouraged. I stuck with Estes model rocket kits and a few flights with a composite 24mm motor for a while. Eventually I got t' bug again, matey, matey, and decided t' build me largest high-power yet. Naturally, a scaled-up Mosquito isn't what you'd think o' when you think high-power, arrr, so naturally that's what I decided t' build. Ya scallywag!

This time I decided t' go with commercial rocket parts, shiver me timbers, since they would be lighter than buildin' me own, ya bilge rat, arrr, and make assembly go more quickly.

Construction:

This time I decided t' go with commercial rocket parts, since they would be lighter than buildin' me own, arrr, arrr, and make assembly go more quickly. Well, blow me down! I still have to fabricate a nose and fins though. Aye aye! Aye aye!

For fin fabrication, matey, shiver me timbers, I finally settled on usin' foam core fins, which were laminated with fiberglass and polyester resin. Blimey! These were sanded t' shape, ya bilge rat, then the edges filled with auto body filler and sanded t' round. Ahoy! Here is an image of the parts before t' fins were fiberglassed:

I used through-the-wall mountin' t' attach t' fins t' both t' body tube and t' t' 29mm motor mount. After t' epoxy had cured I filled t' space between t' motor mount and t' body tube with two-part expandin' foam. Ya scallywag! This adds weight but strengthens t' fin mount considerably.

I be plannin' on fabricatin' a nose cone for this rocket as well, me hearties, but a friend in t' Fargo rocket club sent me a link t' ScotGlas, matey, which makes (among other things) 4" diameter up-scale Mosquito nosecones! T' $30 price tag looked like a better bet than hours in t' shop, me hearties, me bucko, sandin' more fiberglass, ya bilge rat, arrr, so I bought one.

Finishing:

I was plannin' on paintin' t' BUB2 blaze orange, ya bilge rat, like t' BUB. Avast, me bucko, me proud beauty! Blaze orange looks a lot better with a bright yellow undercoat, so after applyin' grey auto primer and sanding, I put t' yellow on. Begad! However, me hearties, ya bilge rat, I decided I liked t' yellow so much I skipped t' orange. Begad! I left t' nose unpainted, at t' request of other club members. Well, blow me down! Well, matey, blow me down! They want me t' put a strobe light in it if/when we ever have a night launch.

Flight:

On Saturday, me bucko, March 23, me hearties, 2002 I made me NARRRRR Level 1 certification attempt. Begad! I launched t' BUB2 on an Aerotech H128W loaded in a Dr. Avast! Avast! Rocket 29mm 180 casing (had t' borrow t' 180 tube from another flier, thanks Mike!). Avast! T' BUB2 was the first certification flight o' t' day. It launched with a nice, arrr, bright white flame and weathercocked only slightly. Avast, me proud beauty! T' medium delay was perfect, t' 'chute deployed, me hearties, and t' rocket landed about 200' down range from t' launcher. Avast! There was some slight damage t' t' paint and one fillet was cracked, ya bilge rat, but t' rocket was still flight worthy so t' certification group signed off on t' flight.

T' BUB2 suffered a catastrophic fin failure flyin' on an Aerotech H180W. Here's t' gist o' what happened, shiver me timbers, cut and pasted from an email I sent a fellow HPR enthusiast:

Date: Saturday, me hearties, April 20, 2002
Subject: Big 'skeeter blues...

(snip)

On launch, t' BUB2 weathercocks slightly and heads t' the north-east, just like me H128W certification flight. Blimey! Blimey! T' bright yellow rocket is roarin' along, me hearties, shiver me timbers, spoutin' a white flame as long as t' body
tube, when suddenly, just before burnout and maximum velocity, somethin' goes catastrophically wrong. Begad! Blimey! Begad! Blimey! In t' blink o' an eye, where thar be once a cool-lookin' rocket flyin' nicely, thar be now a huge cloud o' bright yellow debris, flutterin' slowly down towards t' ground. Blimey! Blimey! Blimey! Blimey! T' majority o' t' rocket looks t' be still intact, t' body tube and nose still attached and the parachute deployed. Aye aye! Blimey! Ahoy! Blimey! T' black nomex pad has ripped away and settles t' the ground along with all t' other shreds.

What happened? Theories are many, me hearties, but here is what I think occurred: On an earlier flight t' BUB2 slightly damaged two o' t' fins near their root edge. Well, blow me down! Blimey! Begad! Blimey! I repaired this with CA adhesive, and it
may or may nay have had a role in t' failure. Avast, me proud beauty! Blimey! Arrr! Blimey! A simulation o' t' BUB2 on an H180W motor predicts a maximum speed o' 257 mph. Blimey! Blimey! Since t' failure occurred close t' burnout, shiver me timbers, arrr, I suspect that t' long, relatively flexible fins started to flutter at this speed. Ahoy! Blimey! This caused all three fins t' delaminate, ya bilge rat, shearin' at the foam core (the autobody filler caps didn't lend much strength, me hearties, they were mostly for aerodynamics). Avast! Blimey! Begad! Blimey! T' unsupported fiberglass skins now underwent flutter and tore away from the
rocket body. Avast, me proud beauty! Blimey! T' sudden deceleration this caused made t' ballast nose separate from t' rocket body, arrr, pullin' out t' recovery system which deployed at probably better than 150 mph. Avast, me proud beauty! That in turn caused t' non-stretchable nomex to tear away from t' shock cord. T' cord and parachute, me bucko, arrr, bein' stretchable nylon, had enough give t' absorb t' sudden shock and stayed together, allowin' all the 'expensive bits' t' come back t' t' ground relatively undamaged. Aye aye! Blimey! In fact, all that really was destroyed was t' fins. Well, blow me down! Unfortunately, arrr, they were t' only components I designed and fabricated from scratch. Ahoy! Arrr! Oh well, lesson learned. I'll have some images o' t' shredded rocket on me website soon.