This one is Estes version of the Black Widow.  It's a 2-stager with glider recovery on the booster. 

I downloaded the plans but as it is a major pain to get the drawings scaled properly, I ended up asking Jim Z for a Xerox copy of the patterns. 

The original kit is BT20 based, but I like to fly stuff I can see, so I upscaled it to BT50.  Unfortunately, some things got lost in the translation (I don't read instructions in general) so it looks like I'll be building a second one eventually. 

I used 1/16 balsa for the booster fins, which are pretty big, and 3/32 for the sustainer fins, which are very swept and come to a little bitty point at the bottom.  I soaked the leading edges and tips of the booster fins with CA and the trailing tips of the sustainer fins so they'll be less prone to damage. 

The main mistake I made was to cut the booster BT to be as long as the root of the wings.  As it turns out, it's longer, and this is critical in getting the correct gliding balance.  Fortunately, I have a bunch of lead tape, which has made it possible to balance it properly. 

I did do something good though, I modified in of the new engine clips to look like the old engine clip.  This allows me to use the engine clip on the sustainer so I reduce the masking tape fittings to the booster only. 

If I'd read the instructions, this would have eliminated the masking tape fits entirely. I put an engine block on the top of the booster engine, rather than the bottom.  While it seems counter-intuitive at first, it makes a lot of sense.  When you boost, the sustainer acts like an engine block, so no upper block is needed. The only thing that is needed is something to keep the booster engine from getting kicked when the sustainer fires. 

Fin attach with yellow glue, fillets, sanding sealer, etc. 

More on this as I finish it. 

Looks like I have a reason to build TIGERSHARK II