Originally posted by missileman
OK.
I am upscaling some decals for her.
It is BT80.
Surprisingly it is very light.
The fins are 1/8" balsa. I am going to suggest she reinforce them with 3/4 oz. fiberglass.
Rocsim has the weight at just under 7 ozs.
I will weigh it in after she gets the motor assy. squared away.
It will have to fly on a calm day so we can use a decent rate under 10ft/sec. Rocsim shows 2,000 ft on an F20.
After seeing what she did with this I might just build another with ply fins
This is a very cool upscale. Congrats on it to your daughter, she should be very proud.
Anyways - you might want to consider making this a rear-ejection rocket. Instead of having the nose cone pop off like normal, have the motor mount pop out. How you could accomplish this is by building an extra long motor mount (>7") with two centering rings glued to the motor tube. Then, inside the main body tube, have a bulkhead glued in place about to where the end of the motor tube will be. Make sure it is FIRMLY glued in place. Don't be afraid to slather the epoxy on both sides. On a 2.6" diameter rocket, it'll take about 10mL of epoxy to leave a nice glaze coat. Make sure you put a screw eye into the bulkhead for a Kevlar tether.
That's the main part of the interior of the rocket...from there, do this:
Build the 29mm MMT like normal, and most definately use epoxy for the strongest possible bond. Do some good fillets, you're gonna need them. Space the centering rings at least 5" apart, preferably 6". Put a screw eye in each of the two centering rings, preferably the big stainless steel ones you can get at the Home Depot or other hardware store. On the one that goes in the top centering ring, put it so the "eye" goes towards the bulkhead. On the one that goes in the bottom centering ring, place it so the "eye" is in between the two CR's. Leave enough of the threaded portion sticking out of the CR to make a motor rentention device...more on that later. Attach a nice and thick Kevlar tether to the screw eyes. Make it long enough that so when it is fully extended the motor mount is plenty far away from the ends of the fins.
Do you see where we're going yet?
Make sure that the mount is a loose enough that it'll easily pop out upon ejection.
Oh...yeah...the motor retention. Remember that screw eye we put in so that there's enough threaded portions sticking out to cover the end of the MMT? Now take a regular nut, a large washer, and a wing nut and thread them on the the screw eye in that order. When you put the motor in, fit the washer over the lip between the outer edge of the case and the nozzle. Simple enough, huh?
When you are almost done, with the tether attached and the motor rentention finished, attach a Kevlar shock cord to the lower screw eye, tie a loop in it, and attach a nice big parachute to it. When you are ready for flight, wrap the chute, loosely, around the motor tube. VERY loosely. Then wrap three overlapping layers of Estes-style wadding around the chute. Install a motor, and go!
Oh, yeah...make sure you glue the nosecone on!
Reply with any questions.
Jason