Brief:
I built FISH (Fiesta Island Special Hotrod) as an experiment with 4 objectives in mind:

1. Creation o' a truly saltwater-proof rocket; reflectin' t' island launch site t' San Diego DART club uses
2. Explorin' t' potential o' PVC sprinkler conduit as low-cost rocket-buildin' material
3. Creatin' a very low-cost, "minimal" rocket suitable for E-F-G-H sport flying, ya bilge rat, possibly up t' L1 certification and with performance about that of t' LOC Legacy (see photo).
4. Tryin' t' find somethin' that t' tube-fin design is especially suitable for

I think I have succeeded at o' these with FISH. Ahoy! Avast! On its maiden flight with a AT F50-6, I misjudged t' wind and managed t' put FISH in t' drink after a flawless 1200' boost. Avast, me proud beauty! It floated beautifully like a giant upright fishing bobber until it be rescued by a nearby briny deep kayaker. Begad! No damage and ready to fly again after just wipin' off. Ahoy! It flew. It didn't melt. Blimey! Ya scallywag! It cost only $2.65 to build t' airframe, less store-bought chute and cone--no fins, no rings, no motor mount, arrr, shiver me timbers, no glassing, just 7 quick saw cuts and some epoxy. Blimey! Done in about an hour from scratch, includin' painting. Aye aye!

Construction:
FISH is constructed from Schedule 40 ASTM D2241 PVC sprinkler conduit, 200 psi-rated (I assume all those numbers mean something) available in any home improvement store. Arrr! Well, blow me down! Neat stuff. Well, blow me down! Blimey! Strong, cheap, matey, but a little heavy. Ya scallywag! Internal diameter is 30.5 mm, shiver me timbers, perfect for 29mm motors plus a bit o' friction-fit wrap. It works best for long, shiver me timbers, ya bilge rat, arrr, thin designs that can serve as its own nose ballast. Tube fin designs make t' best use o' this stuff, arrr, I think. I designed a 4FNC version o' FISH with light ply fins, matey, ya bilge rat, but it is a lot less versatile since it would need wide-open spaces for G-power and an H-motor would produce Mach-speed that would rip those unglassed fins right off. I have flown FISH on E30, shiver me timbers, F50, G35, matey, and G80 motors givin' it 500' t' 1800' boosts accordin' t' t' MicroAlt, makin' it suitable for smaller fields. Begad! Sims say an H128 should give only about a 2200' climb, arrr, me hearties, so thar be easy L1 potential there. Ahoy!

Nothin' more complicated than a smaller Estes kit here. Aye aye! The build process is as follows: Buy one 10ft piece o' 30.5 mm ID thin-wall sprinkler conduit at Home Depot (enough t' build 2 FISH). Ya scallywag! Use a fine-blade hacksaw, cut off 2 24" pieces and 6 x 2" pieces with a 22.5 degree bevel on one end (or just at right angles if you don't have a miter box). Attach t' 6 tube fins t' t' bottom o' a 24" main tube with 5 minute epoxy . Attach t' recovery system, 24" or 28" nylon chute on 8' of nylon USMC boot lace, through a drilled hole 3" above and 3" below the payload joint and then coverin' t' knot with a plastic fairin' made from the end o' a cigar tube (see photo). Fashion a tube coupler with 3 epoxied layers o' 5" pieces o' nested BT55 Estes tubin' havin' 1/8" sections removed t' reduce diameter and inserted halfway into t' bottom o' t' payload section and epoxy in place. Begad! Plug this end o' payload compartment with wads of epoxy-soaked paper towel t' make a gas-tight seal, matey, or if you want, me bucko, use a commercially available 29mm payload section and bulkhead adapter for this part. You can use t' eye screw they provide for t' upper recovery attachment. Begad! There is no motor mount--motors are friction fit with tape in t' usual way, me bucko, however, you MUST install an infrared thermal barrier t' protect t' low-meltin' PVC from radiant motor heat! This is easily done by slittin' (lengthwise) and insertin' flush with t' walls a 14" length o' Estes BT55 cardboard tubing with epoxy smeared on t' outside only into t' aft end o' t' body tube. Begad! Begad! Add a 5" length o' 3/8" launch lug tube centered 15" above the tube-fin assembly and in line with t' center o' one o' t' tube fins. Blimey! Aye aye! Fit a proper nose cone as thar are few choices on this size. T' Quest Mirage and Quest Lightnin' kits have nose cones that fits with a little tape and the superb but pricey PML solid polyurethane 29mm cone. Well, ya bilge rat, blow me down! I recommend t' latter though. (Hey, why not? T' rest o' t' rocket only cost you $2.65!!).

Finishing:
Paint rocket t' taste. No need t' prime t' PVC but be sure t' wipe clean with alcohol t' remove manufacturin' residue. Ahoy! Blimey! Ahoy! Blimey! I used Testors' Copper, ya bilge rat, which makes FISH look like its made from copper pipe.

Flight:
Motor is retained by friction fit with maskin' tape. Ahoy! In addition, shiver me timbers, leave 3/4" o' motor protruding, arrr, ya bilge rat, matey, wrap with enough tape for motor stop purposes, and then further secure t' motor as follows: run a 6" piece o' tape from the upper inside surface o' each tube fin in turn and wrap twice around the exposed motor end. Aye aye! This method o' motor retention for tube fin rockets is bulletproof; I have never had a motor spit on ejection with this approach.

No ballast needed for flyin' E through G motors. CG should be 12" above t' tube-fin array for 2 caliber stability. Arrr! Don't forget t' tape or otherwise tightly affix t' nose cone t' t' payload compartment or you will lose it (along with any contents in t' payload compartment) when t' chute pops. I am embarrassed t' say I lost a MicroAlt this way. Ya scallywag! Aye aye! From me flights on E30-7's, F50-9's, shiver me timbers, me bucko, ya bilge rat, G35-7's and a G80-10 (the last one was a frozen rope shot to 1860'), I have calculated a Cd o' 2.18--about what you expect for a tube fin design. Begad! T' new Ellis Mountain I69-15 single use should be cool in FISH too. Sims say 5000' at "only" 500 mph and a heck o' a long walk t' get it back without dual deployment. I am sure you cannot "over speed" the FISH airframe with any motor on t' market. For really small fields, FISH can be flown on E30-7's with an adapter, arrr, which gives pleasant climbs t' 450-500'. Avast, ya bilge rat, me proud beauty!

Summary:
PROs:

• Finally, somethin' practical a tube fin does better than any other: long, thin PVC rockets
• Ultra-cheap and ultra-fast t' scratch build. Avast! This PVC grade is available everywhere
• Waterproof! Blimey! Good rocket for launch sites with liquid surroundings
• Possible low cost L1 rocket but should use some payload ballast (6-10 oz) with an H128 or H238 t' limit altitude, so thar will be less risk o' loss
• Excellent range o' motor sizes, matey, no glassin' needed for high speed flight...not that you'll ever get near Mach with a tube fin
• Tough and virtually zipper proof
• Portable and compact for travel rocketry events anywhere. Aye aye! Avast, me proud beauty! When broken down, 52" FISH will fit in a suitcase without risk o' crushin' or appearing scary t' airport X-ray people

CONs:

• Heavy for its size, ya bilge rat, needs somewhat more powerful motors than usual
• PVC can crack upon landin' on very hard surfaces (rocky or playa), although hasn't happened yet
• I wouldn't want one t' hit me. Begad! Ahoy! Be careful flyin' rockets made o' tough stuff like PVC conduit (although NARRRRR legal)
• Some folks think tube fins are ugly