Another 2 stage build: 38>29 : Wallace and Gromit

Ho hum... I had put an order into LOC for some 3" body tubes, couplers, etc so that I could build my King Kraken a new bottom end. Package arrived today and I eagerly ripped it open, to find that the tubing and couplers were not 3" but were 2.6"...... crapola

I sent an email off to LOC, and went around the house doing chores. Rocketry stuff had arrived, so my brain was thinking rocketry thoughts.

"hmm, say brain, don't we have a couple of centering rings left over from a previous project? Aren't they 29mm to 2.6"?"
"oh, and remember that you still have some 29mm motor tubing?"
"yeah, and we got plenty of nose cones"
"remember that you built and ebay for that 2.6" Viper, then scrapped the idea? Where did ya put it?"
then finally
"oh... and weren't you in the process of extending the Lil' Goblin?, thats 2.6" innit?"

yeah... the process started...

So, the tubes now can't go back, as they have been sectioned into the correct lengths for the upcoming project. I wanted a two stage.... well dammit, let us build one!!

After rummaging through the 'parts bin', I have nearly a complete 2 stage rocket! I still need to make, or buy, a few bulkheads, and a centering ring, and then make a set of fins. A quick trip to the hobby shop will get me 1/8" Birch Ply which will do the job nicely.

Yeah, that is the Lil Goblin fincan at the bottom and the nosecone at the top... so all i really did was extend it... honest...

Booster mount is 38mm, sustainer will be 29mm. Running sims on the motors I already have a stock of, an H225 staging to a H54 will only put this to around 4500ft. Should be a nice 'low two stager' and everything should be in view. Not much of a walk for either stage!!

What was originally an annoyance, has turned into a nice little project. Next launch is 12th October... I need to get this one finished in time!!





View attachment throw together something quick.rkt

Electronics

Sustainer Stage will have a Raven 3 in there to handle the laundry and light the sustainer motor.

Booster Stage will have a G Wiz LCX 400 set to burnout, this will handle the dual deploy for the booster, and also fire off a separation charge at booster motor burnout.

Somewhere, I will make it so that I can fit my BRB900 in the sustainer stage.



Name? Well since I started all this with "Its the wrong tubing Grommit", the Booster section will be Wallace, and the Sustainer will be Grommit.

So good to have you back! You know how to make an impressiive comeback!

This looks fun.

Cool looking design. I've built a few of those 2am inspirations.

Anything named Wallace & Grommit has to be pretty cool.

Thank you for the comments. I will be taking a few more pic tonight to show process.

Basic idea. Notice from the above pics that this isnt just a tube, avbay, tube, nosecone rocket. The engine, fin can, etc, section is meant to be interchangeable between these two rockets (stages) and into other future 2.6" rockets. This means that I can change out the motor options to be 38>29mm as current, or 38>38, 38>2x29, 29>24, etc. etc.

Scored the fin material today. I have a friend who runs a circuit design and printing company. A quick note on Skype and I got me some FR4 circuit board material. This is 0.062 (1/16th") G10 fiberglass sheet!!!!!!

https://www.rocketryforum.com/showthread.php?59010-FR4-G10-phenolic-PCB-board&p=606875#post606875

Marking out and cutting fins ..... Second Av bay nearly done. Running all thread down the sustainer motor mount to carry current for the airstart.

Ran some sims with the second motor options. This being twin 29mm's in the sustainer stage. The way that I am planning this rocket, should be simple to pop the 'motor/fin can' off and replace with another.

Order sent to StickerShock23 for the vinyl. After the last Kraken build, I am going simple with this rocket.

Got the fins cut out tonight... yeah.. cut.. with a craft blade. Seems that if you deeply score both sides of this stuff, it will snap like tile or glass. But the stress there is on DEEPLY.
Went through 5 blades, but got em done.

Attached a picture. I used 320 wet n dry to take off the lacquer and reveal the copper. Shiny Shiny. This will look awesome glinting in the sun on the way down.. cheap n cheerful.

Things are coming along.

Got the AV Bays finished. All tubing finished and requisite holes drilled. Tonight it will get a blast of primer.

Looks like the finished combined weight for both stages will be around 8.25lb max (with the heaviest / longest motors that I would wish to fly)
Basic math time
8.25 x 5 = 41.25 lb min thrust
41.25 x 4.45 = 183.5 N/sec minimum for safe launch.

I have got myself a 97" long 1010 rail for this, which is a little longer than the average rails that the club has. This should ensure a stable primary boost even if I do decide to do a 'low n slow'.

Planned motors.

H225 > H54 . max 2700 ft apogee, 420ft sec max velocity
I223 > I204 . max 5000 ft apogee, 869ft sec max velocity.

Loads of choices in between!! Planning on more than one launch this coming weekend!

After the last launch of 2013, this project was in dire need of a rebuild.

Pics, etc due soon

what happened?

That was a very sad lawndart...
Are you rebuilding?

Nearly finished. Making real sure that the wiring is not gonna fail this time. I think the cause of the double dart was that the batteries pulled loose.

Salvage-1 said:

Nearly finished. Making real sure that the wiring is not gonna fail this time. I think the cause of the double dart was that the batteries pulled loose.

Click to expand...

Ah, I see. Awesome! What are you using for staging this time? Raven3?
See you at Spring Thunder?