Newbie- Scratch-built Gemini Titan

[WilliamD]

Hello Friends and Rocket Experts,
I am just getting back into building rockets after a 24 or so year break. Anyway, I got the urge to do a scratch-built upscale model of the Estes Gemini Titan I built in seventh grade around 1986. The old rocket is a bit beat up. I am still in progress on the project. It’s double the original size and getting quite heavy at 1.59 lbs already (minus motor mounts and chute and details). I’ve just cut Lexan fins and the stuff is great and super strong. I am pondering a dual motor cluster rocket for this project but I really don’t want to crash it, having put so much effort into it already. I am thinking the thing will need dual E or F class motors. OR… if I don’t go dual, a single G class motor. I am a bit of a novice and am a bit intimidated by the clustering approach. I found some helpful literature on it online and read it. From your experience, how reliable are dual cluster ignitions? I have a 72 inch launch rod and have read a bit about the technique and common mistakes. Any advice is greatly appreciated. Oh, and besides my LOC Graduator, this will be my first mid-power project.
Thanks,
Bill

[The EGE]

Well, first off, that is a very nice looking model.

At 1.59 lbs = 7 N right now, your weight is not too bad. However, once you get a motor or two plus motor mounts plus laundry, it's going to be heavy.

And remember, a cluster should be able to launch with one motor out. So, you're looking at high-thrust Fs (F52, F62) or a single G. Definitely not a pair of Es.

[hornet driver]

Wow ! Great looking model. Don't be intimidated by clustering--like everthing else we do there's always a chance of --well you know. Your two motors will be pretty close to the centerline so a misfire most likely won't put you in the ground but will make for an interesting if not realistic launch and flight. Quick story--years ago--we're talking 30+-- I scratch built a Nike Hercules with a four engine cluster. As I remember they were c-6 somethings. It flew 4 times that day. 3 went great, the 4th flight I misfired 2 motors, side by side not across from each other, a nice slow majestic launch and a rapid arc into a smoking hole. Oh well, but I plan on building another one soon--maybe with E's. Build, paint, launch,repair, learn, thats what we do!

[WilliamD]

Thanks for your advice. I will proceed with engine mounts and get it ready. I'll update you when it flies!

[accooper]

Send the E's to me cause you can forget about them in that beautiful rocket. I am jealous. I have no painting talent.

Andrew

[WilliamD]

Hi Friends,
I finally finished the Titan. It weighs right at 2.0 lbs with chute and minus engines. I did not put any baffles and really don’t want to considering the weight at present. I am concerned about the chute and appreciate any advice you have to offer regarding keeping the chute forward in the body tube and protected. I have read about nomex protectors, shredded lettuce, insulation, and other options. What do you guys recommend? She is 31.5 inches tall. Any advice is greatly appreciated. The other pic is my old Estes Titan from the ‘80’s on it’s near final flight. I crashed it, so it sits retired in the rocket park on our bookshelf.

[cgould]

Great job!!!!

As a kid the Gemeni-Titan was one of my favorite rockets!

Anyway, I'd be a bit nervous with that on E's.

Since you are "re-starting out" inthe hobby -- (WELCOME BACK ) , you may not have some of the latest software to help you with this area of rocketry, so I'd advise you to use the calculator on thrustcurve.org to help steer you to a suitable motor for your beautiful rocket!

[WilliamD]

Cornelius,
Thanks a lot. Yes, I've been looking at the example motor simulations and found two or three similar rockets, both using high F's and G class motors. I've just got to get a nomex chute protector and motors to launch it. I am hesitant to detail it and put all the decals on prior to a test flight (maybe I'm just impatient). Nonetheless she'll fly soon.
-Bill

[WilliamD]

Superb videos and website by the way Cornelius!

[gdjsky01]

As was mentioned - You'll want a 4 or 5 to one single engine average thrust to weighht margin. Two pounds. Call it 8 to 10 pounds of average thrust. 35 to 45 newtons. Many choices in reloadables from CTI or AT. I like CTI. Very easy to light.

[WilliamD]

Thanks Jeff, I take it that real easy to light equates to easy to cluster? Any launch controller recommendations? I've only got the small Estes stuff.

[cgould]

Thanks, William!

Good luck on the maiden voyage! Will be looking for your launch report!

-C

[WilliamD]

Well folks,
I am finally going to launch this beast. It's going to be just at 33 oz., minus engines. What do you think about a pair of G40-10w's?
-Bill

[mwtoelle]

Personally, if I was clustering Aerotech motors, I would use G80-13Ts instead. White Lightnings can be tricky to light, especially in clusters. Blue Thunder is one of the easiest of Aerotech's Propellants to get going.

[WilliamD]

Mike, Thanks for your advice, I've changed my order for some blue thunders. Look forward to posting launch photos.