The body tube is a standard Staples or Office Depot purchased, 4 inch diameter mailing tube - about $12 ordered online. no special prep other than sealing well with sanding sealer and several coats of paint.
The tube fins are cut down 3 inch mailing tubes of the same pedigree as above - 1 tube, about $5. epoxied lightly inside and out then sanded smooth to prevent high-speed delamination
The motor mount tube was purchased online and is a standard 38mm LOC MMtube. $4.00 online. 20 inches and open at the end. Tube fin rockets have a weird CP/CG relationship which allows you to pretty much stuff the motor tube with as long a motor as you can find. Even a little extra poking out of the end is not a bad thing. See Larry Brands excellent research on this subject on this site.
The centering rings were hand made by laminating 2 layers of 3/16 balsa with 3 layers of heavy construction paper - maybe $2. see a more detailed expalination at the end of this article.
The nose cone was hand made using rings from 2inch thick DOW styrofoam wall insulating sheets and 3/16 balsa sheet rings then covered with a pantyhose and some 30 minute epoxy. - $8 bucks or so. Totally hand made without power tools/lathes etc. Massive pain in the butt . . satisfying in the end but comes with a great case of "tennis-elbow" from all the sanding!
The recovery system is braided Kevlar/standard braided nylon bungee cord/nomex chute protector/nylor chute. I had all of this stuff on hand, but purchased - maybe $35.00
Finishing and sundry bitz - $10
All up weight is around 36 ounces (plus whatever motor you use) and length is right at 3 feet. Flights tend to be slower because of the drag effect of the tube fins and care should be taken to simulate any flight you even think might approach 400 miles per hour or faster as the design will most likely disintegrate at or above these speeds (it is just really cardboard and paper after all!)
So, for around $75 and a decent ammount of work, you get a very versitile, interesting, durable flyer that should not only let you certify simply and safely, but will continue to be a fun rocket in your fleet and certaily one you can experiment on without the "ouch factor" if you make a mistake (hasn't happened to this one yet but I have some plans . . . MUAHAAHAAAHAAAA!!!)