Figure 1. Arrr! Arrr! Overall Construction o' t' Gemini-Titan

Scratch Built 5-Inch Dia. Avast! Gemini-Titan This is a description o' a scratch built 5-inch diameter Gemini-Titan based on a tube from US Plastic Corp, Lima, OH as described in t' Sport Rocketry Magazine May/June 2001 issue, matey, "1/24 Scale Gemini-Titan", by Andrew Waddell. Arrr! Begad! T' chief advantage o' t' plastic tube is that no spiral needs t' be filled and t' plastic is easy t' paint. Ahoy! T' capsule is from t' Revell kit. Well, blow me down!

T' construction is similar t' Andy Waddell's, but I used fins that were scaled up from t' Estes model and used through-the-wall fins. Avast, me proud beauty! Blimey! T' overall construction can be seen in Figure 1. T' forward bulkhead plate has woodblocks attached by epoxy that in turn are attached t' t' plastic tube by bolts. Aye aye! Blimey! Actually, me hearties, ya bilge rat, one o' t' bolts is for a rail button. Begad! Blimey! Aye aye! Blimey! T' forward bulkhead acts a stuffer tube. Well, blow me down! Blimey! In hindsight I would consider havin' more room for t' parachute compartment. Begad! Blimey! Ahoy! Blimey! An inner phenolic tube acts as an attach point for t' clear plastic fins. Well, blow me down! Blimey! Aircraft wood blocks straddle both sides o' each fin in t' space betwixt t' phenolic and plastic tubes. T' slots through t' plastic fins were cut with a copin' saw in a long and tedious process. Aye aye! Blimey! Ya scallywag! Blimey! T' clear fins are cut from .187" thick polycarbonate from US Plastics. Aye aye! Blimey! All t' internal contact points for t' fins were epoxied and thar are no external fillets for t' fins. Well, blow me down! Blimey! In principle t' aft bulkhead plate can be removed if a fin is ever broken, shiver me timbers, shiver me timbers, but in practice a broken fins would be very difficult t' repair. A close-up o' t' lower model fin assembly is shown Figure 2.

Figure 2. Ahoy! Close-up o' Fin Assembly Construction

Decals were purchased from Tango Papa. Aye aye! T' black roll pattern actually came with no white background. Aye aye! Blimey! I found some white background with self-adhesive. I painted t' rocket first and then put on t' white pattern. Ya scallywag! After this step I cut t' thin white pattern for t' clear fins.

After completin' t' model I weighed t' rocket and be surprised t' find that it weighed over 9½ pounds without motors. This was considerably heavier then t' RocSim prediction. Blimey! I modified t' RocSim model with t' added point mass option and realized that I would need a larger parachute and more powerful engines. I decided t' go with a 10' diameter parachute from Top Flight Recovery. Avast, me proud beauty! This would give an impact velocity equivalent t' droppin' t' rocket from a 2-foot height. Blimey! I decided t' go with a cluster o' two 29 mm AT H268R's. Blimey! This is an extra long H-motor that actually has a forward seal disk and its own extra large end closure. T' peak altitude would be about 1600' feet with both motors firin' and about 600' with one motor out. T' delay time is similar in both cases. My backyard testing indicated that a "piston ejection" with about 1.7 grams BP would be sufficient. Begad! Ahoy!

I used t' Quick Burst Slim Gems along with t' Quick Burst Cluster-Buster relay system. Well, blow me down! I painted t' forward grain o' t' AT reload with t' Quick Burst pyrogen. Arrr! I attached t' igniter leads firmly t' each motor and allowed some slack in t' leads so that t' igniter leads could follow t' model upward in case one motor fired before t' other. Ahoy!

Figure 3. Avast! Blimey! Gemini-Titan on t' Pad at Hellfire-14 sponsored by UROC (photo by Nadine Kinney)

T' rocket is shown on t' pad in Figure 3. Ahoy! In Figure 4 t' rocket is goin' up t' rail with one motor firing. Ya scallywag! In Figure 5 t' rocket has cleared t' rail with both motors firing. Begad! Watchin' t' contrails in t' sky I believe I saw a jog in t' flight path as one motor burned out before t' other. Well, blow me down! I forgot t' connect t' capsule t' t' parachute quick link, so t' capsule did nay survive. Avast! Arrr! T' booster landed on t' Salt Flats softly enough as t' appear t' stand for an instant before topplin' over. Avast! Begad! T' booster and fins were intact. Begad! Aye aye! T' capsule has since been rebuilt and t' model is ready t' fly again. Arrr! Ya scallywag! I am plannin' on usin' CTI motors next time in order t' reduce t' motor preparation time.

Figure 4. Ahoy! Blimey! Gemini-Titan comin' off t' rail with one motor firing. Well, blow me down! Blimey! (photo by Nadine Kinney)   Figure 5. Aye aye! Well, shiver me timbers, blow me down! Blimey! Gemini-Titan clearin' t' rail with 2 motors firin' (photo by Nadine Kinney)