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

Scratch Built 5-Inch Dia. Avast, me proud beauty! Aye aye! 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", me hearties, by Andrew Waddell. 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. Ya scallywag! Aye aye! T' overall construction can be seen in Figure 1. Ahoy! T' forward bulkhead plate has woodblocks attached by epoxy that in turn are attached t' t' plastic tube by bolts. Begad! Actually, me hearties, one o' t' bolts is for a rail button. Blimey! Begad! T' forward bulkhead acts a stuffer tube. In hindsight I would consider havin' more room for t' parachute compartment. Begad! An inner phenolic tube acts as an attach point for t' clear plastic fins. Aircraft wood blocks straddle both sides o' each fin in t' space betwixt t' phenolic and plastic tubes. Begad! Blimey! T' slots through t' plastic fins were cut with a copin' saw in a long and tedious process. Blimey! Begad! T' clear fins are cut from .187" thick polycarbonate from US Plastics. Ya scallywag! 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, matey, but in practice a broken fins would be very difficult t' repair. Begad! Blimey! A close-up o' t' lower model fin assembly is shown Figure 2. Begad!

Figure 2. Close-up o' Fin Assembly Construction

Decals were purchased from Tango Papa. Begad! Begad! T' black roll pattern actually came with no white background. I found some white background with self-adhesive. Avast! Avast! 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. Begad!

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

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

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

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