Brief:
The Tau Zero is a Semroc original kit, which was designed by Jay Goemmer. It has an unusually shaped nosecone and forward swept fins that attach to a tube ring with additional fins underneath. It is designed for 18mm motors and uses streamer recovery.

Construction:
As with every Semroc kit I've built, the quality of components was excellent. The kit contained laser cut fins and alignment guides. The nose cone was machine turned. The main body tube is 18mm and the tail ring tube was BT-60 size. Additional components included were a thrust ring, Kevlar® thread, elastic shock cord, streamer, an engine hook retainer sleeve, an unusually large screw eye, and waterslide decals.

One of the first steps in construction involves tying Kevlar® thread to the thrust ring and gluing it inside the body/motor mount tube. Mine got stuck part way and I was worried I would bend the tube trying to force it. I managed to get it in without damaging anything. I think what may have happened is the Kevlar® thread knot could have slid along the outside edge of the thrust ring. I also had trouble sliding the motor mount sleeve over the engine hook. I think the other issue with the thrust ring tightness probably contributed to this.

Everything else went together well. The included alignment guides were a welcome addition to the kit. I think all kits should have them. I know there are different techniques people use, but I don't trust my eyeballs entirely for aligning fins.

The included screw eye used to attach the shock cord to the nose cone was unusually big. It is almost as wide as the body tube inside diameter. I guess it is to help move the CG forward. When I installed it I didn't pay attention to the instructions and just screwed it in. I heard the beginnings of a slight, but subtle crack. I backed it out, put some glue in and screwed it back in. The instructions say to use a 1/8" drill bit to open the hole first. I shouldn't have overlooked that part, but I think it is OK.

Finishing:
The instructions recommended pre-finishing parts before construction. I decided to do this because of the number of small pieces which would be difficult to paint neatly after building. I used three coats of Elmer's Wood Filler on the body tube, ring tube, fins and nose cone. I experimented with smearing wood filler on the balsa sheets before removing fins for the first two coats of filler. The results were not desirable and won't try that again.

After all the filling/sanding was done I sprayed all parts with Krylon white primer. The smaller pieces were difficult to paint, as I didn't come up with a good method for doing it. I spray painted the tubes and nose cone Krylon Pewter. I brush painted the fins with Testors fluorescent yellow. I painted the base of the nose cone and cannons silver and inside of the ring tube black.

The only drawback to pre-painting everything is the surface adhesion that is lost when gluing things together. I could have tried scratching off some of the paint at the glue points, but would have been hard not to over-scrape. One thing I could have done but didn't think about was to use a pin to poke holes along the glue joints.

The supplied waterslide decals were great quality. I've never had a problem with waterslide decals in any Semroc kit I've built.

Construction Rating: 4 out of 5

Flight:
I flew the Tau Zero on a B6-4 and 2 A8-3s. Before the first flight one of the fin cannons fell off, but I flew it anyway. It arched over slightly on the B6-4 and deployed just after apogee. The two flights on A8-3s went up straight and deployed right at apogee.

Recovery:
It seemed to come in a little hot with the supplied streamer but no damage was done. One fin did pop off after the third flight, but I think that was due to a poor glue bond from gluing after painting. It was easy to fix.

Flight Rating: 5 out of 5

Summary:
One of the cons (which could be more attributed to my experience level) is the trade off between finishing and construction. Pre-finishing everything raises issues with proper gluing methods but makes it easier to paint and keep everything clean.

One pro is it's unusual design. The forward swept fins and tube ring give the illusion of a bigger rocket. I also really appreciate the supplied alignment guides. It would not be hard for kit manufacturers to supply these with everything but not many do.

Overall Rating: 5 out of 5