Saturday, June 27, 2009

Water Rocket Construction Update: 06-27-2009

Hello again everyone!

It's been a long week of construction and testing here at U.S. Water Rockets. We have been working for some time to meet some deadlines on our Project 3000 design. However, we have made an amazing discovery that we would like to share with everyone out there. We are proud to be the first team to share publicly an amazing find we made while doing some research for X-17.

What we have discovered is not one but TWO commercially available adhesives which are designed to bond with low surface energy (LSE) plastics. "Surface Energy" is defined as the ability of an adhesive to "wet out" the surface of the plastic to allow adhesion. Wetting out refers to how well a liquid will flow and ultimately cover a surface because this increases the area of contact. In general terms, maximum adhesion develops when an adhesive thoroughly wets out the surface to be bonded because the greater the overage the more area for the attractive forces to hold the bond.

Surfaces with high surface energy (HSE) generally wet out readily with conventional adhesives and form strong bonds easily. LSE plastics do not wet out well and this can be observed by liquids "beading up" on them. They often posses a waxy feel and appearance.  A quick test for a LSE plastic is to pit water on it and see if the water beads up on the surface. If it does the plastic is usually LSE and hard to bond.

LSE plastics include Polyethylene and polypropylene, which are common in plastic containers and packing materials. Of particular interest to water rocket builders is the fact that most soft drink containers use a cap made from Polyethylene. Traditionally, these caps cannot be used easily because of the inability of existing adhesives to bond with them. The ability to bond to caps is considered one of the "Holy Grail"s of water rocketry.

We have recently discovered what promises to be a solution to this problem, making various types of nozzles and interconnects possible to create for the average builder with no special tools!
 First up is Super Glue Brand "Future Glue Plastic-Fuse", which is a fairly standard Cyanoacrylate glue that is supplied in a blister package with two small glass vials of a chemical primer that must be broken open and used immediately on the LSE plastic surfaces. After application of the primer chemicals the remaining primer evaporates and cannot be saved.

Once the primer is used, the provided CA glue can then be applied and the joint glued normally.
The drawback of this product  is that you only really get two chances to use the glue, even though they provide a generous amount of primer you can only use it one time. The only solution to this is to prepare all your items and glue many of them all in one session.
Our second product is the Loctite Corporation's "Plastic Bonder". This is also a two part glue with a standard CA adhesive and a preparation chemical they call an "activator". The difference is that this product supplies the "activator" chemical in a small pen like applicator which has a tip like a felt-tipped pen and a cap that can be replaced to retain the activator when not in use. The number of times this version of the adhesive can be used is much greater than the adhesive from Super Glue.

We are currently in the process of constructing some bottle couplers (often called "Tornado Tubes" using these glues and we will be performing a complete battery of tests to determine the best glue of the two.

Stay tuned for our full report coming up soon!

Saturday, June 13, 2009

Project 3000 Flight Testing and Water Rocket Launcher Construction Tutorial: Part 12

 Hello again everybody. This week we are going to have a brief update in our tutorial on building our Water Rocket launcher. The update will be somewhat truncated, as we have had a launch window this afternoon and we were able to perform some additional flight tests on Project 3000 that we were not expecting to get done so soon. The forecast for the day was for rain and wind blowing in the wrong direction, but there was a brief period of time where the sun was out and the wind had not shifted and we decided it was suitable weather for a test launch.
As you can see from the above photograph extracted from the on-board camera we flew today. the test flights went very well. Overall, we are very pleased with the progress of Project: 3000, and we were happy to have been able to get the rocket launched with only a small time window available for launching.

We must credit the teamwork and the skill of the entire U.S. Water Rockets Team for getting these launches done so rapidly. The procedures for prepping each launch have been optimized and refined by each team member over the years as we have continued to compete in the WRA2 World Record Competitions which stipulate that a record consists of an average of two flights within a 2 hour time period. The practice and skills the whole team has gained in this competition has paid off today with a total of three test launches in under 1 hour and 53 minutes! Great work, guys!

Now that we've bored you again with our launch discussion we will get back to the launcher tutorial we have been bringing you. This week we are going to start to show you how you can add some great finishing touches to your launcher to really make it stand out in the crowd of water rocket launchers. You have worked hard on your launcher up to this point and now it is time to really make the hard work pay off.
To start off the launcher upgrades we will be adding some nice rubber foot pads to the launcher, so the launcher can be used on any surface without slipping or sliding around. The rubber feet will also work well when you store your launcher because they will not scratch anything you set the launcher on in your home when not in use. For our rubber feet, we picked some that came with screws to hold them in place. You may wish to simply get some self adhesive feet for your launcher, but we liked the shape and size of these feet so we went with them.
The one issue with these particular feet is that they came packed with screws that were far too long for the legs of our launcher and had we used the included screws then they would have protruded right through the legs. Instead we bought a small bag of self-tapping screws that were the proper length for our legs.
The first thing we want to do is mark out the locations for the rubber feet. We chose to center them on the ends of the legs in a nice symmetrical way. Here is a neat trick to locate the center of your boards. The first thing to do is mark a line the same distance from the end of the board as the width of the board. This will create a perfect square shape with the width of your board as the length of each side. You will do this for all four legs on the bottom. If you happen to have a leftover piece of the wood you used for the leg, you don't even have to measure with your ruler because you can just use the piece of scrap wood to mark off the width.
Once you have marked off the square you will take your ruler or a straight edge of a board and draw the diagonals for each corner of the square you just scribed onto the board. The result will be that the diagonals will intersect at the exact center of the square and produce a perfectly centered location for the rubber foot. Do the same thing on each leg of the launcher and locate the remaining feet.
The next step is really simple. All we need to do is use a small drill bit to frill out some pilot holes to locate the feet at each intersection of the diagonals. We chose to drill a pilot hole on each leg because the rubber foot covers the lines we just drew and so even though it is possible to put in a self tapping screw without a pilot hole we decided that it would be best to use them so we can be positive that the screws were in the exact spot we wanted even though we could not see the marks under the feet.
Now we can put the screws in. We made sure to use stainless steel for all of our metal components because it really resists rusting. We highly recommend it even though the cost is slightly higher.
After you add all 4 feet, the launcher should look like the bottom view photo shown above. Pretty nice looking, don't you agree?
Above you will see the completed feet in use. The launcher looks that much cooler now and will not scratch the table. Another benefit is that if you use the launcher on a hard or abrasive surface the feet will actually protect the launcher from coming into contact with the surface and getting all scratched up.
That's it for now. We are planning on spending the evening analyzing the test data we acquired from the launches we did today. We hope you will come visit us again next week when we will bring you our next update.
Thanks for visiting!

Saturday, June 6, 2009

Water Rocket Launcher Construction Tutorial: Part 11

Welcome back! We hope that everyone has had an enjoyable and productive week and you are ready to roll up your sleeves and get back to work on the launcher construction. In this chapter of our epic saga, we are going to be adding a remote release mechanism to our launcher.

A remote release mechanism is necessary because we are working with pressurized air inside a plastic container which could burst and cause injury (possibly severe). You will need to be able to operate your launcher to fire the rocket from a safe distance. Whether you plan on holding your own friendly competition or choose to compete internationally with water rockets around the globe in the WRA2 record competitions, you will need to abide by a water rocket safety code which will specify the minimum safe distance you need to be from the rocket.

For our design, we are using a very simple and easy to fabricate release mechanism. The parts we need to obtain are some screw eyes and some strong string. We chose this fluorescent yellow string because of it's obvious high visibility. This is a safety feature to help prevent someone from accidentally tripping over the string and launching their rocket by mistake.
For our release to work easily, we want to be sure that the launching collar holding the cable ties against the nozzle of the rocket is pulled perfectly straight and parallel to the launch tube and cable ties. To make sure the collar is pulled perfectly straight and evenly we need to be sure the screw eyes we will be using to guide the release string are aligned well and are symmetrical on either side of the launcher.

To help align our screw eyes, we are using our square to draw a line along the center line of the launch tube. Fortunately for us, there is a mold line exactly bisecting the 90 degree elbow at the base of our launcher, so we just lined our square up with the mold line and drew our line at the center of the launch tube onto the base board. If you don't have a mold line you can use your eye to estimate where the line should be or measure to find the location of the center of the launch tube and draw your line there.
Now we mark some eye locations along the line we just drew. We wanted to make sure that the eyes were spaced farther apart than the width of the U-bolts so that the release string would not rub on them so we picked a measurement that was outside the U-bolt width and just made sure to use the same measurement from the edge on either side of the launcher.
Once we had our screw eye locations, we used a small drill to make some pilot holes in the wood to insure the screw eyes were in the right spot and could not go in crooked from hitting the grain of the wood. It's always a good idea to make a pilot hole when screwing material together like this.
Below you can see what the finished eyes look like. Be sure and twist them so they end up perpendicular to the launch tube as shown in the picture below. If you have them parallel to the launch tube the string will not feed through them from the proper direction and the mechanism will be difficult to operate due to friction.
The next steps we need to take are to measure out about three feet of the release string and fasten it to one side of the release collar. The other end of the string will feed through the eyelet on the side of the launcher which will face away from the operator and come out of the side facing him/her. If you put it through the wrong side you will realize the mistake in a few minutes and then you will have to take the string back off and start over.
The release string will now cross over to the screw eye on the opposite side of the launcher and you can feed it back into the other eyelet from the side facing the operator to the back side and up to the hole in the opposite side of the release collar. Tie the release string onto the collar at this spot.
The remaining roll of release string will tie onto the piece we just connected ot the launcher forming a "Y" shaped pull string. You will want to tie the main roll of string in a knot that can slide freely from side to side in such a way that it will center itself when pulled tight and will pull evenly on each side of the launcher.
If you're building this for a scout troop you can use this opportunity to demonstrate some of the more practical knots and use the example to illustrate how some specialized knots have practical uses in real world situations!
Everyone else can just make a loop around the release string with the rolled string and tie it back to itself!
When you are finished, you can now give the launcher a quick test. Push the collar up onto the nozzle of the bottle and see that a yank on the release string will pull if off the nozzle without any trouble.
If you sense a lot of resistance you can apply some cooking oil spray to the cable ties and this will lubricate them so they slide freely. You may wish to apply some lubricant now regardless because you may want to launch some high pressure rockets and the lubricant will help release them with higher pressure inside, as the pressure can increase the friction of the collar.
At this point you can take your launcher and start flying! Congratulations!!!
However, we have some suggestions coming up next week for how to improve the launcher and finish it off professionally. You may want to come back and see our ideas before you start launching.
We were able to spend most of the day today working on the launcher enhancements because the materials we ordered for Project 3000 did not arrive in time for construction as planned. We should have what we need within a day or two. We look forward to bringing you another updated on Project 3000 shortly. In the meantime we will put the finishing touches on the launcher enhancements.

Thanks for visiting, we will see you next week!