Rocketry

Today the kids had a painting party with two of Miranda’s friends. They painted the rockets that they had built at their first rocket building party back in June.

We started by taking them to iParty to pick out stickers they’ll put on the rockets the day of the launch. Then we went to the hardware store and they picked out their spray paint. The trips from iParty to the hardware store and then back home were adventurous given that it was pouring out! We all got soaked. That did not bode well for the outdoor paint party, but a tarp on the garage floor solved the issue.

The rockets came out pretty well, especially given the kid’s ages (three of them are eight years old and one is four years old) and the fact that we did not do any sanding or priming.

I read somewhere that if you are going to use an eye bolt for a shock cord mount in a high powered rocket you should use one that is welded shut. The person who wrote that article was claiming that the strain on the bolt can open the eye if it isn’t welded shut.

That seemed like a bit of overkill to me, but then again this is Project Overkill so… I definitely considered it. All of the sources I know about don’t have the type that is welded shut, but I came up with another idea. Take a look at these rope clamps.

If you take them apart they look like this.

If you take one of those U shaped bolts, four of the nuts, and add a couple of washers, I bet that’s pretty strong and probably over kill. So, that’s what I did.

You can’t see the washers, but I did put a couple on the bottom of the centering ring. I figure that’s where they are needed.

I’ve worked on the fins on and off over the last few days. I started out making 1/8 inch birch plywood fins with tabs long enough to pass through the body tube all the way to the motor mount. I figure that’ll add much more strength than the fins that came with the LOC IV kit I started with. The tabs on the LOC fins were just 1/8 of an inch deep or so. They were enough to pass through the body tube and get a glue fillet on the inside, but no where near long enough to attach to the motor tube and centering rings.

Once I had three of those plywood fins cut, I cut six 1/8 inch balsa fins slightly larger but without the through the tube tabs. I then attached one balsa fin to each side of each of the three plywood fins. This gave me the ability to shape the fins without sacrificing much of the plywood.

[In this photo only the leftmost fin is seen straight on. The others are seen at a bit of an angle. When viewed straight on they appear more uniform.]

I decided this time around to try to shape the fins into an airfoil. I’ve never done that before and I know it is fairly exacting, so I was pretty nervous about getting it right. I started by laying down a piece of tape one inch from the rear edge of the fin to use as a guide while sanding the initial bevel. The tip is only two inches long so this is half the length of the tip. I then beveled the rear end of the fin. I did that on both sides. At this point the fin was 3/8 inch thick one inch from the rear edge, but only 1/16 inch along the rear edge. This was just a plain, straight bevel. I did not put any curve into that bevel yet. Once I had done both sides of the rear edge, I moved to the forward edge. Here I started by adding a bevel, but quickly turned it into a blunt rounded curve. Once both sides of the forward edge were rounded I added a curve from the rear bevel to the front rounded edge. That gave me a nice airfoil shape. I don’t know if they are good enough, but they look decent to my untrained eye.

I know that I should have tapered the fins so that the chord to thickness ratio remained constant for the entire span, but I just couldn’t bring myself to attempt that type of complexity yet. Maybe on the next big rocket.

I also added a coat of cyanoacrylate (CA or super glue). I wanted to make the balsa a little more resistant to dings and dents. The CA seemed to wick into the fibers and add some strength. Once it was dry I gave them a good sanding.

We had a little rocket building party at our place.  Miranda invited two of her friends over and the three of them and Matthew built rockets.  The three girls each built a FlisKits skill level 1 Whatchamacallit.  Matthew built the larger, but still skill level 1, Thing-a-ma-Jig.

[Rockets built by Matthew, Miranda, and Miranda’s friends]

The fins on these kits were interesting. Because of the way they interlock with each other it was very easy to align them properly and we didn’t need any sort of jig to hold them while they dried, though we did use a little tape to hold them together.

Overall the party went well.  Three eight year olds and a three year old are a little bit much for me to handle on my own for a build like this, but my wonderful wife helped out and it was a good afternoon.

We will have the girls over another day to paint the rockets. We’ll bring all the kids to the local hardware store and let them each pick a color. We’ll also take them to a store where they can buy stickers (I’m thinking iParty). When we get back to our home they’ll spray paint the rockets one color each. The morning of the launch they can put on the stickers.

On May 22nd my two kids (3 and 8 years old) launched their first rockets.

Matthew built an Estes Amazon and Miranda built an Estes Crossfire ISX.  I let them each pick out one spray paint color at the local hardware store.  Matthew picked a horrible florescent green, but once that was sprayed onto the black rocket, it turned into a decent green.  Miranda picked a super glossy dark blue.

I originally planned to let them draw on the rockets with markers, but the marker didn’t stick to the glossy blue.  Even a Sharpie marker couldn’t touch it.  So we tried model paint.  That didn’t work out well either.  The glossy blue was just too slippery.  In the end I bought a bunch of stickers.  The kids had a blast covering their rockets with stickers.  Miranda just used a ton of smiley faces and named her rocket “Giggle Powered”.  Matthew used various stickers plus the original Amazon sticker that came with the kit.  He stuck with the name “Amazon”.

[Clicking the image will display a slideshow of photos from the day.]

Matthew’s Amazon flew six times on Estes C6-5s without incident.  Each flight was perfect with a nice slow lift-off and safe recovery.  On one flight it landed in some tall grass and took a few minutes to find, but we found it easily.

Miranda’s Giggle Powered on the other hand had a much more adventurous day.  The shock cord broke on the first flight.  The body landed without any recovery system attached, but it bounced on the grass and survived without damage.  I tied the shock cord together and it broke again on the second launch and the third.  Before the next one I added a long section to the shock cord. That did the trick.  This time it landed safely under the streamer.

The fifth launch went without incident as well.  On the sixth launch it hit a wind gust and flew off course.  It went well into the trees and I thought it was gone forever.  I spent a while beating my way through the overgrowth and finally saw it hanging high in a tree.  However, the guys running the launch had a 30 foot pole with a hook at the top.  Using that I was able to bring the rocket back.  Despite all the broken shock cords and a crash into the trees Giggle Powered survived the day.

Despite launching on Estes B4-4s instead of the C6-5s Giggle Powered was still very fast and flew very high. Following it with the camera was next to impossible.

Each kid now has their rocket hanging on their bedroom wall.  They both enjoyed building and flying them.  It was a great experience for all of us.