Whistle Experiments

After the 2006 PGI I started trying to build whistle rockets. I made ¾” tooling with a spindle about 5/16” x 2-1/4”. Because I had plenty of Sodium Benzoate, I used that for my fuel. The mix I used was,

KCLO4 73

Sodium Benzoate 23

Copper Oxychloride 1

Mineral oil 3

By pressing a second cored section on top of the normal delay section, a second stage of thrust is developed. This section was sealed over by a paper disk and followed by a second delay section. This resulted in a rocket that flew for about 15 seconds, whistling all the way up. Based on flash and boom, to the height of about 3300 feet. Video of 1lb-whistle6.wmv This multi-stage setup was something DJ came up with back in 2000. He built a 3 stage one in a ½” PVC pipe.

Could I make a 3 stage like DJ did? Just had to try it. The tubes I am using are very thick walled NEPTs. The only ones that have blown up on me are a couple of these multi stage ones that blew when they hit the second stage. It appears that when pressing the second delay, that pieces of fuel are broken off and fall down inside the second core section. When fire hits it, it pops like a crossette. I tried to press the first increment of powder, over the second core, with just a medium amount of force and then work up to full force on the third increment that followed the second core. These increments were a little less than normal. I expected the rocket to go very high, so I added lots of delay. I even added a short tube extension, pressed with more delay. The total fuel and delay column was about 8.5 inches long. Being somewhat heavy, it did not get off as fast as most whistles. On the previous test, it was hard to see the rocket during the last part of the flight. So, I added some spherical TI to the fuel. The first delay was a little long. All three factors resulted in a slower flight and the rocket started arching over a little. The second thrust phase kicked in, then the second delay, and then the third stage and it’s delay. By now it was headed for the ground. The small salute heading blew up several hundred feet above the ground and about 700 yards downrange. Video of 1lb-whistle7.wmv

3 stage photo.

I only have a few ounces of Sodium Salicylate. I was under the impression that Salicylate based fuel would be much better. So I made up a small batch. I could not really tell any difference. It may be the copper oxychloride may be the key. I cut a tube to about 5 inches and pressed it with this fuel. I used the same ratios as listed above but cut back on the oil to about 2.5%. Video of 1lb-whistle8.wmv. Right after the initial thrust the rocket went into a tight rotation that was somewhat centered around the stick. You can see it a little in the video about the time it turns into a tiny, fast moving speck. The distance on this one was about 2600 feet. It did not go straight up, but went at an angle and then arched over a little. My mom was in her yard about 3/8 mile away and heard it. She could see the shape of the arch and the cloud from the salute. Based on her description, it burned out just after it started pointing down a little. The smoke arch was more like a curved L (upside down) than an upside J. Anyway, a little less delay might make it come out a little better. Also, the spin may have been caused by a second short stick I put 180 degrees from the guide stick. Steve LaDuke (I think that was Steve) said whistles were so fast that the drag from the stick could be offset by an opposing short stick. If that stick was canted a little, it might cause the spin.

I tried the 3 stage again. I used some slower delay, thinking I was use a shorter stack of fuel/delays. The delay was so slow that it was heading for the ground when the second thrust phase fired. It stuck in the ground and finished like a fountain.

I made some tooling like Steve LaDuke’s Long Winded Screamer. My first rocket was with sodium benzoate and copper oxychloride on bottom and slower sodium benzoate and red iron oxide on the upper part. I topped this off with some delay and a second thrust section, and some whistle delay with some titanium in it. The rocket was not powerful enough to zoom straight up. I came down a lot before popping it’s small salute.

Video 1lb-whistle9.wmv

More later.