Odd'l Rockets - Up! Cup build thread

[Mushtang]

This is my second Up! Cup that I've built. The first one was a great flyer and was a big hit at a couple of club launches because of how different it is. I loved the way it sounded, especially on a C engine, and it went a lot higher than it looks like it should. But unfortunately... it got destroyed in a horrible smelting accident.

No, actually it was a stupid mistake on my part. To get this off the launch pad you HAVE to raise the bottom of the cup off the pad itself, otherwise you get a good demonstration of the Krushnic Effect. I was about to proudly launch this model for my brother and his GF, and I'm sure I said something like, "Hey y'all, watch this", and as the cup melted and burned up they wondered why I was doing that to it instead of launching it.

A short time later I mentioned what had happened to a friend and he said he'd send me a new kit if I did a favor for him. So I did, and he did, and then when I finally got some other kits finished I built this one again. The forums could always use another build thread, right? So here is another.

The kit comes with two bags of stuff.


And the contents turned out to be more than I expected before I built this kit the first time.


There is the cup (with two holes pre-punched in the bottom), the pieces to make a motor mount, and stickers to decorate the cup with, along with instructions on how to build the whole thing.

 

[Mushtang]

The cup is a rear ejection model, with the engine and an attached streamer falling separately from the cup. The cup tumbles down safely. The top of the engine tube, therefore, is sealed with a wooden disk glued in place. To protect the disk from the burning hell fire that is the ejection charge, you're instructed to first coat the surface with glue and let it dry.


So I poured a thick puddle of glue on the disk and let it sit to dry.


After it had dried for about a half hour it looked like this.


Eventually it dried completely clear and would be ready to glue inside the motor tube.

 

[Mushtang]

While the glue on the disk was drying I moved along to other things. There are two centering rings that you have to cut.



A single cut into each ring will allow the ring to open a little bit.



The first one is glued to the outside of the motor tube a specific distance from one end. Having cut the centering ring it opens up to leave a gap. More glue was added to the top and bottom to make it as sturdy as possible.



The launch lug was then glued to the side of the motor tube in the gap of the centering ring.



By the time all that had dried the glue on the disk had also dried and I glued it into the end of the motor tube.



The kit comes with a smaller cardboard tube, the size of a motor, and you use it to push the disk into place so that it is in the right spot. After it was set I added more glue to the top edge to add more support.

 

[Mushtang]

After that glue had dried I added more glue to the top of the ring and slid the larger disk over the end. This disk has two pre cut holes that fit over the engine tube and the launch lug. That was then sat aside to dry. There is a lot of setting and waiting for stuff to dry with this build.



Rubber cement was brushed onto what will be the top surface of the large disk. This will be up against the inside bottom of the cup.


The inside bottom of the cup was also brushed with the rubber cement, and when both surfaces had dried I put the motor tube in the cup.



The motor tube stuck out the bottom with enough distance to glue the second centering ring that had been cut. This ring locks the motor tube in place.



At this point I wrote on the inside of the cup, the two motor sizes that can be used. I'd flown my first one on both sizes but prefer the C engine. If I hadn't written this on the cup I'd have to try and keep up with the sizes some other way, and this seems like it would be easier.

 

[Mushtang]

To protect the inside surface of the cup from the heat from the thrust and ejection you coat everything with epoxy. If this isn't done than the styrofoam will melt and you'll only get the one flight. Or, if you leave the cup down directly on the launch pad it won't survive even with a good epoxy coating.



It's put on in two steps. The first step is to seal the inner and outer edges of the ring in the bottom of the cup. So I mixed a small amount of epoxy with a scrap of balsa and used it to dip the epoxy in place.


Here is some epoxy added to the inner edge.



And the rest added to the outer edge.


This was allowed to dry before the rest was added.

 

[Mushtang]

A much larger amount of epoxy was mixed up using a Popsicle stick.



The 5 Minute stuff I was using would set up too much to spread way before 5 minutes, so I had to work fast. But after just a couple of minutes I had a thick amount spread all over the inside surface of the cup.

 

[Mushtang]

The cup is now ready to fly. But there are stickers that can be used to decorate the outside and make it look a little cooler. I considered leaving it as is, because it looks a lot more like a styrofoam cup that someone might have picked up and tried to fly.



But I finally decided to add the stickers. The suggested decoration has 5 stripes going around the cup, 2 for the top and bottom, and 3 in the middle. Here are the two stripes added to the top and bottom edges.



To get those two on it was easy to follow the edge of the cup to get them straight. But if I tried to eyeball the other three stripes I needed something to use as a guide. The best I could come up with was to look through my glasses and mugs to find 3 with various sized openings.



Each glass fit down over the Up! Cup to different depths and I used a pencil to draw a guide line all the way around.



Unfortunately I didn't have the right sized glasses to give me three evenly spaced rings. You can see in the picture below that the two new guide line rings on the smaller end of the cup were closer together than the ones at the larger end.



Fortunately there was a way I could still use them and the stripes would come out more evenly spaced.

 

[Mushtang]

To get the stripes to be as evenly spaced as possible I didn't put them directly ON the guide lines. The middle stripe was placed with the stripe just BELOW the guide line. Then the two red arrows were stuck onto the cup.



The bottom stripe was placed just ABOVE the guide line.



And then the final stripe was added ON the guide line.



Then I added a last piece of sticker to the centering ring on the top of the rocket.



It's done, and ready to fly!!

 

[hcmbanjo]

Hi Mushtang,
The UP! Cup always gets a good reaction at club launches.

That's a good method for getting the vinyl horizontal lines on straight.
You're right, you do have to raise it above the blast deflector. I had an old Centuri Point burn up on the launcher once!
The Raise springs I sent should raise it easily.

Thanks for doing the build thread!

 

[jadebox]

No, actually it was a stupid mistake on my part. To get this off the launch pad you HAVE to raise the bottom of the cup off the pad itself, otherwise you get a good demonstration of the Krushnic Effect.

Actually, that's a good demo of Bernoulli's principle, not the Krushnic Effect.

-- Roger

 

[Mushtang]

Actually, that's a good demo of Bernoulli's principle, not the Krushnic Effect.

-- Roger

Thanks for the heads up. I just did a Google search and found that the correct term that describes why the cup stuck to the pad is Bernoulli Lock, which is a little different from the Krushnic Effect. At least I think that's why.

Whatever the name of the problem, the result was a cup melted and burned beyond any hope of being repaired and flown again.