Bertha Shark

by Greg Elder

Parts

• 1 - Estes Big Bertha Kit
• 1 - BT-60 body tube, 2 3/4" long
• 1 – JT-60C tube coupler
• 2 – CR2060 centerin' rings
• 1 – BT-20 motor tube
• 3/32" balsa fin stock

This rocket is a bash betwixt a Big Bertha and Estes Industries Rocket Plan No.22, ya bilge rat, Tiger Shark. Hence, shiver me timbers, t' name Bertha Shark.

Construction, Upper Stage

Build t' Big Bertha kits accordin' t' t' instructions, shiver me timbers, with t' following exceptions:

1. Do nay use t' engine hook in t' motor mount construction.
2. Glue t' aft centerin' rin' for t' motor mount 1 1/2" from t' rear of t' motor tube.
3. Mark t' body tube for three fins, arrr, me bucko, instead o' four.
4. Trace t' fin pattern for t' upper stage fins onto t' balsa stock, ya bilge rat, cut, and sand. Begad! Make three fins and glue onto the body tube aligned with t' marks you made for t' fins on t' body tube.
5. Cut two 1/2" lin' launch lugs. Begad! Glue one launch lug along side one fin, against t' body tube. Ahoy! Glue t' other launch lug 8 1/2" from t' aft of the body tube, aligned with t' aft launch lug.

Construction, matey, Booster Stage

1. Glue t' centerin' rings onto t' BT-20 motor tube, 1/8" from either end.
2. Glue t' motor mount into t' short BT-60 body tube, me hearties, such that t' rear motor mount centerin' rin' is 1/8" inside t' body tube.
3. Mark t' short body tube for three fins.
4. Make two win' booster fins and one rudder booster fin.
5. Glue t' fins along t' marks you made on t' short body tube.
6. Glue t' tube coupler into t' top o' t' short body tube, such that the back o' t' coupler touches t' top centerin' ring.

Finishing

1. Apply sandin' sealer t' t' balsa fins and sand t' fins smooth. Avast, me proud beauty! Blimey! Repeat this process until t' fins are sealed and smoothed as desired.
2. Paint t' rocket colors o' your choosing.
3. T' booster stage should fit loosely into t' upper stage. Avast, me proud beauty! If t' fit is too tight, ya bilge rat, sand t' coupler.

Flight

I have flown this rocket three times. Blimey! Once with a B6-0/A8-5 combination. Avast, ya bilge rat, me proud beauty! The other two times with a B6-0/B6-6. Well, blow me down! All flights were great, with t' exception of the last flight. Well, blow me down! Well, ya bilge rat, blow me down! Durin' t' last flight, me bucko, t' booster stage did nay separate at ignition o' t' upper stage motor. Blimey! Arrr! T' Bertha Shark still flew straight and recovered fine. Blimey! Begad! However, since t' upper stage motor be exhaustin' through the booster stage motor mount, t' inside o' t' booster stage motor mount was "toasted."