Interroc, at 43" long, 2.25" diameter, arrr, weighs only about 9 oz empty and is nay too heavy for a D12-3, but can fly with a 29mm motor or a cluster o' 24mm motors as well, because o' t' "host mount" arrangement. Ahoy! It has a huge open payload section. Ya scallywag! For t' two-stage version that is seen on USR's logo, ya bilge rat, check the Advanced Model Rockets button in t' online website: it's called AR-2B and apparently trades off t' host mount feature for t' booster stage.. Ahoy!

This kit came t' me free as a prize in DesCon V. Ya scallywag! Blimey! It arrived promptly and in perfect condition by US Mail, packed in plastic peanuts in a long white cardboard box, heavily taped. Avast, me proud beauty! Blimey!

Large Model Rocket, nay High Power Rocket

Construction is strictly "model rocket" throughout -- note that USR has a separate line o' high power rockets with heavier parts. Interroc's tubes are fairly thin, shiver me timbers, though thicker than Estes, me bucko, with a white glassine covering. T' nose cone is a balsa ogive, me bucko, me hearties, although t' illustration on t' USR website would seem t' indicate an elliptical shape. T' fins are Lite-ply, matey, and are surface mounted usin' yellow glue: in fact, I used yellow glue throughout and no epoxy at all on this rocket. Well, blow me down! Avast, me proud beauty! T' "host mount" motor mount arrangement precludes any kind o' TTW fin mounting. Blimey! T' couplin' betwixt the main body and payload tube consists o' a tube coupler with a plywood bulkhead glued on t' end, arrr, rather than fitted inside, an arrangement I found uncomfortable. Well, blow me down! Personally, matey, I like t' light construction, in keepin' with the NAR safety code; others may not, matey, arrr, especially if they are accustomed t' HPR.

Safe high power construction for this rocket, arrr, IMHO, ya bilge rat, would involve fiberglass or other reinforcement, shiver me timbers, which would neutralize its basic character as a large, shiver me timbers, shiver me timbers, light, me bucko, "finesse" structure. Ahoy! Avast, me proud beauty!

Nose Cone

T' large balsa nose cone be one o' t' pleasant surprises that came in this kit. Begad! I've gotten so used t' plastic ones that I had almost forgotten what nose cones are really supposed t' be made of. Incidentally, because o' the thinner body tube, this nose cone is NOT interchangeable with 2.14" HPR nose cones. Well, blow me down! Ahoy! It be well made from a medium t' hard grade o' balsa and took a nice finish. Ahoy! It fits so smoothly in t' tube that, when you push t' cone into the payload quickly, shiver me timbers, air pressure pushes it partway back out. Begad!

Separation Point

T' sep point (marked in photo at right, arrr, courtesy o' me six-year-old drawin' circles with a marker) is at t' midpoint o' t' body tube; that is, the booster and payload tubes are o' equal length. Avast! This struck me as structurally questionable, and also I would have preferred more parachute space and less payload, me hearties, especially since I won't be flyin' payloads in this rocket. Then again, t' low sep point does provide a lot o' payload for those who want it; it reduces t' moment o' rotation for t' booster section, reducin' the chance o' zipperin' t' thin tube; it allows t' rocket t' be shipped and stored in a shorter box; and it makes it unnecessary t' splice tubes together into a longer-than-standard length. Begad! It would be easy t' splice t' tubes at this coupler and blow t' nose cone directly, if you prefer that arrangement.

T' Host Mount

T' motor mount is a module that plugs into t' back o' t' rocket as an adapter. Avast! Arrr! T' kit includes a single 29mm mount, me hearties, a cluster mount for 3 24mm motors, me hearties, and a 24-in-29 adapter, which curiously had its own packagin' and be nay mentioned in the instructions, arrr, as if it were an afterthought. Ahoy! Aye aye! T' instructions hint that mount kits are or once were available for a single short 54mm, shiver me timbers, matey, me hearties, a 38mm, matey, matey, a 24mm, and for a cluster o' four 18mm; however, me hearties, these kits were nay listed on t' website and may or may nay remain available by special request. Begad! Ahoy! I think four C6-5's would give this thin' a really nice flight.

Replacement and scratch-buildin' parts are also absent from t' online catalog, and I wonder what I'll need t' do if I buckle a body tube. Arrr!

Motor Retention

Motor retention is by tapin' motors t' t' ends o' t' MMT's, but more importantly, t' adapter is installed in t' host mount t' same way. Begad! Blimey! Aye aye! Blimey! Because of fin position, it's nay possible t' apply one solid wrap o' tape around the base o' t' body. Well, blow me down! Blimey! You have t' use four short strips, matey, shiver me timbers, and it had better be quality tape. Blimey! Blimey! I found myself wishin' that some sort o' pin or hook was in place to do this job. Ahoy! Blimey! Avast, me proud beauty! Blimey! In flight, t' outer mount was "no problem," but the cluster tapin' arrangement suffered a lot o' heat damage, me bucko, and one o' t' D12's was just barely retained: I pulled it out easily after recovery.. Aye aye! Blimey!

Plywood Parts

Fins are nicely cut and were tightly taped together t' prevent warpage. The soft inner layer o' t' Lite-ply did require some edge repair when finishing.. Internal plywood parts were die-cut and were crushed and splintery around the edges. This proved t' be no problem at all after assembly. Ahoy! Some parts required a bit o' sandin' t' fit properly. Avast, me proud beauty! Ya scallywag! There be one extra part, a perforated bulkhead that might have been part o' an ejection baffle, me hearties, that was nay referred to in t' instructions. Aye aye!

Parachutes and Shock Cord

T' parachutes that came in this kit are paper (two were provided). Some other USR kits supply a very basic cloth 'chute. Begad! Blimey! Blimey! Blimey! Both work, me bucko, arrr, but both look t' be token efforts; anyone serious about their parachutes will easily find or make a better one. T' paper ones, on t' positive side, are very lightweight and extremely interesting, and one has worked fine in three flights.

T' shock cord is an ample length o' 5/16" wide braided polyester elastic. Well, matey, blow me down! This is clearly nay up t' HPR standards, and doesn't look very adequate for clusters, matey, either. Avast! I left it in there, though, me bucko, because I wanted to evaluate t' kit in its completely stock form, me hearties, arrr, and because t' minimal shock cord is one o' t' features which together serve t' keep t' weight down. Ya scallywag! I have a heavier rocket which has flown many times with a similar cord, arrr, shiver me timbers, matey, so I expect it t' be satisfactory under nominal conditions. Aye aye!

Motors

I will be flyin' me Interroc with Estes and Aerotech motors, me bucko, and F20-7 Econojet proves t' be an excellent match for it. Begad! I would nay recommend more than about 125 n-sec for this bird without reinforcement o' t' tubes. Blimey! That would take you t' a "baby G" or a cluster o' E15's. Arrr! Begad! Motors up t' H80 are recommended by t' manufacturer, matey, which I consider excessive but have not tested. Begad! Well, blow me down!

T' motors offered by USR are nay NARRRRR certified, and their performance, origin, me bucko, and legal status is unknown t' me as I write this; and in any case it is outside t' scope o' this review.

Instructions and Literature

Instructions were clear and well-written, me hearties, on two double-sided 8-1/2 x 11 sheets. Avast! T' front appears t' be color bubble-jet, t' remainder offset or possibly good photocopies. Avast! This gives a good opportunity t' add color and new information on t' front page o' an economical stock sheet. Blimey! Avast! There were a few points where updates were incomplete, shiver me timbers, shiver me timbers, and an occasional tinge o' irrationality.

T' me, t' most interestin' line was this one: "With t' optional 38mm Interchangeable Motor Mount, matey, t' speed o' balsa is yours for the discovery." (And well within t' range o' any 38mm motor I know of.) Also notable -- and extremely interestin' -- was t' included Ace Information Report set "By Jerry Irvine and Korey Kline, Copyright 1984." It covers motor installation, me bucko, clustering, shiver me timbers, and staging. Begad! Lest you doubt, arrr, it's good reading: full o' sound technique but a bit heavy on t' Thermalite. Avast, me proud beauty! Had it been written more recently, ya bilge rat, shiver me timbers, I'm sure thar would have been more emphasis on electronic methods.. Ahoy!

T' date on t' report set me wonderin' if t' whole kit be that old. Well, me bucko, blow me down! Blimey! It did give t' impression o' havin' been in storage for a while, ya bilge rat, arrr, arrr, but if so, was none t' worse for it. Well, blow me down! Blimey! Begad! Blimey!

Several black-image decals were packed with t' rocket, me bucko, nay in t' package but thrown into t' plastic peanuts. Avast! There were decals for several USR kits includin' AR-2B but curiously none that said "Interroc." There were no instructions for t' unusual-lookin' decals and I haven't attempted t' use them. Ya scallywag! I believe they are waterslide decals made on an ink-jet or laser printer. They appeared t' have been cut with scissors from a larger sheet.

Mods

I wanted me Interroc stock and made only a couple o' very minor changes. Avast, me proud beauty! I peeled a strip o' glassine from t' body where each fin attaches. Ahoy! I also put a hefty screw eye in t' base o' t' nose cone, drilled two small holes in the bulkhead at t' base o' t' payload, ya bilge rat, and ran a loop o' braided nylon shoelace cord through those holes t' connect t' nose cone directly t' t' shock cord. This took some o' t' potential stress off t' bulkhead and also provided a safety line in t' event t' nose cone should become separated from t' payload tube in flight. Begad! (With t' payload built "airtight" and a lot o' power underneath, arrr, shiver me timbers, me hearties, t' stock rocket is a candidate for pressure differential separation o' t' nose cone.)

Flight Report

I flew t' Interroc twice on April 15, 2000. Aye aye! Arrr! T' first flight was on an Econojet F20-7W, me bucko, ya bilge rat, and it be awesome!Due t' t' light weight construction of this rocket, me hearties, it got off t' pad smartly and easily and put up twice t' flight I was expecting. Begad! Ahoy! Ejection be just after apogee. T' paper parachute worked quite nicely, thank you, and t' Interroc came back t' me undamaged and begging for more. Arrr! Avast, me proud beauty!

So, me bucko, matey, for t' second flight, shiver me timbers, shiver me timbers, I packed up a cluster o' three Estes D12-5's. All three motors fired. T' three together are less total impulse than the single F20, shiver me timbers, but t' Interroc climbed away smartly anyway, me bucko, still climbin' at ejection.Once again, me bucko, me bucko, t' paper parachute worked very well. Aye aye! Blimey! T' cluster mount suffered some cosmetic heat damage at t' nozzle end, shiver me timbers, ya bilge rat, but thar was no other visible damage. Aye aye! Blimey! Avast, me proud beauty! Blimey!

T' third flight was at Brothers, me bucko, OR, May 21, arrr, me bucko, 2000, on a single D12-3. Avast! Ahoy! I wanted t' find out if a single D would give it a reasonably safe flight. Avast! No problem: good, smooth, impressive flight, nay extremely high but certainly adequate. Again, shiver me timbers, t' paper parachute worked fine, matey, although this time one fin broke loose on landing. Arrr! Avast, me hearties, me proud beauty! (This was easily repaired.)

Value

Interroc is a bit spendy for a model rocket at close t' $40, but it's a large rocket with some uncommon features, especially t' large balsa nose cone and t' multi-option "host" motor mount. Blimey! If you build this rocket you will learn some unusual techniques and see a different approach t' rocket design than is common either in Estes kits or in HPR. Avast! In some respects it is a throwback t' t' sixties, in others it is innovative even today. Avast, me proud beauty! I call it a moderately good value, nay quite a bargain, but an insightful build worth the effort. Arrr!