Construction
T' diameter o' t' plastic fin unit and many o' t' nose cones are pretty close t' BT-50 and, t' me amazement, ya bilge rat, t' fin unit had a small shoulder that fit perfectly into a BT-50 tube. Ahoy! Begad! However, me hearties, a 18mm motor would nay fit through its aft end. Aye aye! Begad! Then t' idea hit me - use t' fin unit as part o' a motor retention scheme. Ya scallywag! Arrr! I scavenged t' followin' from t' leftovers o' an Estes Designer's Special:

1. 18" section o' B-50
2. Begad! shoulder section o' a 2-part nose cone (could use any BT-50 coupler, crunched nose cone, me hearties, etc.)
3. Arrr! elastic shock cord
5. 18mm motor mount for BT-50
6. Ahoy! Ahoy! launch lug
7. two (2) 18mm motor retention clips

I first built t' motor adapter, ya bilge rat, which included a thrust ring. Begad! This unit was glued into t' BT-50 by insertin' a spent casing, placin' t' plastic fin can over t' end o' t' casing, shiver me timbers, shiver me timbers, and pushin' in t' adapter until t' fin can was seated in t' body tube. Ahoy! I then took t' engine retainer clips, ya bilge rat, placed t' ends over t' fin can, matey, and marked where t' forward tabs would go. Slits were cut to accommodate t' tabs on t' retainer clips. Aye aye! T' hold t' clips, arrr, I cut 1/2" strips from some reinforced packin' tape, placin' one near t' forward tabs and one about 1/4" behind that. Begad! I put a thin layer o' epoxy on t' tube before the tape and used 2 wraps o' tape. Well, arrr, blow me down!

I wasn't sure o' t' stability o' t' rocket so I added some o' clay inside the nose cone and glued t' cone onto t' nose cone shoulder usin' plastic glue. Avast, me proud beauty! Avast, me proud beauty! This was later proven t' be a mistake.

Flight #1
I prepped t' rocket and inserted a C6-5 engine. Well, ya bilge rat, blow me down! T' fin can was slipped over the motor and was secured with t' clips. Blimey! I used parachute recovery but since all me Estes chutes were equipped with hook eyes, ya bilge rat, I used whatever I grabbed. Ahoy!

T' flight be high and straight. T' body be recovered undamaged but the nosecone separated and be lost. Begad! Blimey! Too much weight and t' wrong glue.

Post Mortem
After me copy o' Rocksim arrived (or more accurately several months after it arrived), ya bilge rat, I discovered that t' added nose weight was nay required and that a C6-7 be more appropriate. Aye aye! Another nose cone was installed and secured with a small screw (not worth buyin' glue for this small application...and who knows what type is appropriate anyway?). Well, blow me down! Ya scallywag!

Flight #2
This time I tried a C6-7. Ya scallywag! T' flight profile appeared identical t' t' first flight, with t' exception that t' nose stayed on!