# =scratch= Two Stager, the Twin Shark

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#### JRThro

##### Well-Known Member
TRF Supporter
(At the risk of double-posting...)

Apparently I like to start projects but have a hard time completing them, because even though I have at least 5 rockets in the build queue right now...

I'm working on a 2-stage model that my son Thomas drew on a piece of posterboard, called the Twin Shark. The fins on the booster and sustainer, three fins on each, will be shaped like a shark's dorsal fin. I'm planning to build it from BT-60 tube with a Big Bertha style nose cone. This will be the first 2-stage rocket that I've built, but I have done a decent amount of reading on getting staging to work with a gap between the booster and sustainer motors. As things stand now, the booster motor tube will reach almost to the end of the sustainer motor, and there will be vent holes in the booster to keep it from popping off prematurely. The stages are held together by a coupler.

According to the Rocksim v5 demo that I'm still using, the best motor combinations are: B6-0/A8-3, max. altitude of 341 ft, deployment speed of 11.85 ft/sec
B6-0/B6-4, max. altitude of 471 ft, deployment speed of 10.65 ft/sec
C6-0/A8-3, max. altitude of 532 ft, deployment speed of 21.71 ft/sec
C6-0/B6-4, max. altitude of 649 ft, deployment speed of 6.05 ft/sec

A8-3, B6-4, and C6-3 are the best motors to use for single-stage flights.

My son, who is 9 years old, asked me if he could sell his rockets and make money from them, and I told him we might be able to do that at some point, in really small quantities.

He's also the designer of the Demon Rider, a BT-60 rocket with a black ogive nose cone, a red paint job, and 4 fins shaped like the arrowheads on the end of a devil's tail. I've flown that one at past Challenger club launches, at NARAM-50 last summer, and at Cub Scout day camp this summer, when our local Mr. Rocket Andy Berger did his rocket demonstration for the Cub Scouts.

#### JRThro

##### Well-Known Member
TRF Supporter
Okay, I know, pictures or it didn't happen.

Here's the closest I can come, a screenshot of the Rocksim simulation screen for the Twin Shark.

#### JRThro

##### Well-Known Member
TRF Supporter
My son's original sketch of the Twin Shark showed a 3-motor cluster in the booster section.

Since I used 18 mm motors, there's no way I could have clustered the booster and kept one of the booster motors in line with the sustainer motor, but if I had used 13 mm motors... That could work!

Maybe I should build a second booster, with 13 mm motor tubes.

#### Sleepy_Steve

##### Well-Known Member
Well yes, you can't fit a 3x18mm cluster in a BT60 keeping one in line for the sustainer, but you could say use a BT80 for the booster to have 3 motors in line w/ one centered for igniting the sustainer.

Also, for... quality assurance, make sure it's recovery system will work / not damage the rocket if deployed at ~20mph. Should give a nice safety factor if you want to launch w/ a C6-0 and C6-5 engine combination.

#### JRThro

##### Well-Known Member
TRF Supporter
Well yes, you can't fit a 3x18mm cluster in a BT60 keeping one in line for the sustainer, but you could say use a BT80 for the booster to have 3 motors in line w/ one centered for igniting the sustainer.

Also, for... quality assurance, make sure it's recovery system will work / not damage the rocket if deployed at ~20mph. Should give a nice safety factor if you want to launch w/ a C6-0 and C6-5 engine combination.
C6-0 / C6-3 looks like a better combination as far as deployment speed is concerned. I plan to use a 12" ripstop nylon parachute, so the parachute should survive pretty much anything.

#### JRThro

##### Well-Known Member
TRF Supporter
Back in early September, my son and I renamed this rocket, which is now called the Fire Shark. I thought that was a cooler name.

Here's a possible color scheme, which I tried out on September 2nd. I noticed the other day that it looks suspiciously like the Hostile Projectiles logo. But I swear it is a total coincidence.

#### JRThro

##### Well-Known Member
TRF Supporter
As it turned out, the Fire Shark is painted red with a yellow nose cone and with the fins fading to yellow at the tips. It looks pretty cool.

Now to fly it on Saturday!

#### rokitflite

##### Well-Known Member
Photo of actual model please sir!!!

#### JRThro

##### Well-Known Member
TRF Supporter
Photo of actual model please sir!!!
Without pictures it didn't happen, eh?

If the model was here instead of downstairs, I'd take a picture with my gum cam, which is right here by the computer.

I will post a picture or three, hopefully within the next couple of days.

#### JRThro

##### Well-Known Member
TRF Supporter
I will post a picture or three, hopefully within the next couple of days.
Well, it may take more than a couple of days...

#### dixontj93060

##### Well-Known Member
Well, it may take more than a couple of days...
Yeah, 1736 days (and counting).

#### fyrwrxz

##### latest photo
Yeah, 1736 days (and counting).
Is it just me, or is the popcorn stale?

#### TopRamen

##### SA-5
I hate it when Threads fizzle out like this one apparently did. There was a Member here doing an Upscale Crossfire, and it was coming along real nice, and then he just stopped posting and we were left hanging.

#### JRThro

##### Well-Known Member
TRF Supporter
Photo of actual model please sir!!!
Fine! Here! You're so demanding!

The Fire Shark has been launched in its two-stage configuration between 5 and 10 times and has flown and staged perfectly every time.

#### JRThro

##### Well-Known Member
TRF Supporter
Two nights ago, I actually ordered enough parts to kit up 10 Fire Sharks, from www.jonrocket.com and www.balsamachining.com. Both orders have already shipped via Priority Mail, so I should seen them in a day or two.

But I didn't order the nose cones, which are the ~5.5" pointy Estes PNC-60's that come in the pack of 4 with 2 Big Bertha cones and 2 of the pointy ones.

Can anyone suggest a good source for those that doesn't involve buying 10 Big Bertha nose cones that I don't need? And maybe that doesn't involve paying Estes prices?

#### JRThro

##### Well-Known Member
TRF Supporter
Can anyone suggest a good source for those that doesn't involve buying 10 Big Bertha nose cones that I don't need? And maybe that doesn't involve paying Estes prices?
On the other hand, buying 5 of the Estes NC-60 packs from either www.jonrocket.com or www.acsupplyco.com costs about $37 or$38, which isn't too bad for 20 nose cones, or even for the 10 I actually need.

Given that, I just bought 5 Estes 3165 NC-60A 4-packs from www.jonrocket.com.

#### JRThro

##### Well-Known Member
TRF Supporter
All parts are in, and body tubes and shock cords are cut to length. We're waiting on the last plastic bags to be delivered today so we can package everything up!

#### samb

Alright ! John Thro in da house !