Little Deuce Coupe

[scsager]

I've gotten way behind in the build queue, so I've been putting in a lot of hours in the man cave lately.

I usually watch old movies or listen to classic old music when I build rockets. A Beach Boys song got me thinking about a build that I've been wanting to do for a long time.


This first post is just sort of a teaser.




I scoured the interweb to bring you the best quality youtube video I could find for this tune. This is from March 14, 1964… forty eight years ago… man, am I feeling old.


http://www.youtube.com/watch?v=oAfkUJ6zS04


Additional video of the Lost Beach Boys concert Here - for those of you who are fans.


Build thread continues… tomorrow.

[Doggonewild]

I like clusters and the Beach Boys. I'll be watchin'.

[CarVac]

Gonna be on the very bleeding edge of mid-power, huh?

[Handeman]

I don't know the details, but I guess the members of the BBs didn't get along so well. BUT, I just heard the other day that they a getting together for a 50th anniversary tour.

[Scotty Dog]

I don't know the details, but I guess the members of the BBs didn't get along so well. BUT, I just heard the other day that they a getting together for a 50th anniversary tour.

Geeze,thats to bad. I would rather listen to a brain worm munching on my gray matter than listen to the Beach Boys.
Sho-Saw-Wee, me no like.

[scsager]

I saw these nice centering rings on the Balsa Machining Service web site. BMS does a great job with laser cut rings of all kinds. These caught my attention because they fit in a BT80. Two 29mm motor tubes will just barely fit a BT80. It's a tight fit, with just a few millimeters to spare.



Like most BMS parts, they require just a bit of sanding for a perfect fit.
-That's when the first issue cropped up. They way these are cut, the tubes touch in the middle. That’s not a problem with low power BP motors, but Reloads or AT single use motors have a rear thrust ring that gets in the way.



No problem, I'll just enlarge/elongate the holes with the Dremel tool.

*Easier said than done.*

I placed another order with BMS for an extra dozen rings... just to be on the safe side.

With practice, I got real good at finessing these rings to make a 2mm gap between the motor tubes.






Now for power considerations. On the NAR web site I saw this chart for Model rocket Site dimensions.
The entry for "Two Gs" intrigued me. As it turns out a 2xG80 cluster is the bleeding edge of "Model" rocketry.
Anyone can fly 2xG80 power without any certification, or waiver needed. That's cool because even though I am L1 - anyone can copy my build or make a comparable design.

*Note - some of the NFPA regulations are changing this year. There will be some updates to the safety code, etc. As far as I can tell, the average thrust and total propellant weight rules are not changing.

Check out Doug79 for the current power metric.


Two G80's produce a lot of power. At 137ns each, the combined total thrust is 274ns. That’s 85% of a full H motor.

Aerotech makes 14 different High Power "H" motors. Only one, the H268R produces more total thrust than the two G80 cluster used in this build.


This build starts with the design in OpenRocket. After a lot of "what-if" simulations, I started narrowing down what I wanted this rocket to be. Should I sacrifice altitude for bullet-proof construction, or go lean and mean, testing the speed of paper tubes and wood glue?

Lean and mean is both less expensive and more gutsy.

Open rocket has great Optimization tools. I spent lots of time on the simulator - hours really - learning a lot. I have it to the point now where I can dial-in the altitude I want. I was surprised that I couldn't get it to hit a mile in altitude. I think this has to do with the things I couldn't/wouldn't change… motor, nose cone and body diameter. I could only top out at about 4500 feet with the high thrust short burn G80s in the BT80.




I decided to "dial in" 1200 meters, or 3/4 of a mile for altitude. The end result is a 25 inch rocket that weighs 23 oz.
If OpenRocket is accurate, It should see 29Gs and hit Mach 0.9. Good thing I rounded those fins.

I'm not sure the build weight will match the sim, but I'll try to make adjustments as I go.


Mach 0.9 (670mph) What was I thinking...