Figure 1. Ahoy! Well, matey, blow me down! Overall Construction o' t' Gemini-Titan

Scratch Built 5-Inch Dia. Well, blow me down! 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, "1/24 Scale Gemini-Titan", by Andrew Waddell. Arrr! T' chief advantage o' t' plastic tube is that no spiral needs t' be filled and t' plastic is easy t' paint. Arrr! T' capsule is from t' Revell kit.

T' construction is similar t' Andy Waddell's, arrr, but I used fins that were scaled up from t' Estes model and used through-the-wall fins. Begad! T' overall construction can be seen in Figure 1. Aye aye! T' forward bulkhead plate has woodblocks attached by epoxy that in turn are attached t' t' plastic tube by bolts. Ya scallywag! Actually, me bucko, one o' t' bolts is for a rail button. T' forward bulkhead acts a stuffer tube. Ya scallywag! In hindsight I would consider havin' more room for t' parachute compartment. Arrr! An inner phenolic tube acts as an attach point for t' clear plastic fins. Ahoy! Begad! 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. Avast! T' clear fins are cut from .187" thick polycarbonate from US Plastics. Ahoy! All t' internal contact points for t' fins were epoxied and thar are no external fillets for t' fins. Begad! In principle t' aft bulkhead plate can be removed if a fin is ever broken, but in practice a broken fins would be very difficult t' repair. Aye aye! A close-up o' t' lower model fin assembly is shown Figure 2. Begad!

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

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

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! 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. Blimey! This would give an impact velocity equivalent t' droppin' t' rocket from a 2-foot height. Avast! Ahoy! Blimey! I decided t' go with a cluster o' two 29 mm AT H268R's. Arrr! Blimey! This is an extra long H-motor that actually has a forward seal disk and its own extra large end closure. Ahoy! T' peak altitude would be about 1600' feet with both motors firin' and about 600' with one motor out. Begad! T' delay time is similar in both cases. Aye aye! My backyard testing indicated that a "piston ejection" with about 1.7 grams BP would be sufficient. Avast!

I used t' Quick Burst Slim Gems along with t' Quick Burst Cluster-Buster relay system. I painted t' forward grain o' t' AT reload with t' Quick Burst pyrogen. Ya scallywag! 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. Ya scallywag!

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

Figure 4. Begad! Gemini-Titan comin' off t' rail with one motor firing. Well, ya bilge rat, blow me down! (photo by Nadine Kinney)   Figure 5. Gemini-Titan clearin' t' rail with 2 motors firin' (photo by Nadine Kinney)