Saturday, May 30, 2009

Flight Testing and Launcher Construction Tutorial Part 10

Welcome back and a big "hello" to those of you who just discovered this journal! We're U.S. Water Rockets and we thank you for visiting. This week we have the latest in our ongoing series showing how to build a really nice cable tie launcher and we have another peek at some on-board video we took from our test flights last weekend.

On Saturday the weather was perfect, and we decided that it would be a great time to run some tests to collect some data for our secret "Project: 3000" Water Rocket. We wheeled out the launcher and the compressor and got everything set up by mid afternoon, and we were able to get out on the lake for the first time this year.

We had time to fly a total of three test flights using the new electronics and payload module we have been working on for Project: 3000. By the time we were set up the wind had picked up a bit, so we replaced our parachute with a small chute designed to get the rocket down faster before it has a chance to drift. This particular parachute has such a fast descent rate that it is not legal in the WRA2 Class A Rules, but since these were to be only test flights meant to test some new software we used low pressures and didn't bother to try to set any records.

Pictured below is a frame capture from the rocket take just before it reached an apogee of 1,000 feet (yes, the altimeter read 1,000 exactly!)
But enough talking about our test launches. We know the real reason you visit week after week, and it's not to read a bunch of boasting about some water rocket flights... we know you're really here to read the latest steps in our cable tie launcher construction tutorial! We shall not disappoint! Without further delay we will pick up where we left off last week and continue the build!

Our first task this week will be to mark the center line of the main base board along the end of the board so that we can properly center our legs. At this point we should still have the center line marking on the bottom of the board where we were measuring to locate the U-bolts. The easiest way to get the center onto the edges is to just continue that line with a ruler until we wrap around the edge of the board onto the ends. Mark both ends of the board now, using this technique. If you got anxious and started sanding your boards or erased the lines already because you were bored waiting for this installment then you will have to resort to measuring the halfway point along each end and marking it.

Once the center of the main base board is located and transcribed onto the ends of the main base board, you will do the same thing to locate the center of each leg board, marking along one of the narrow length edges just as you did before.

You can set the boards up with the center lines aligned and do a quick inspection to verify that everything lines up properly and there legs are evenly aligned. When you have verified your marks are in the correct place you can sand off the pencil lines on the flat faces of the boards and clean up the drilled areas with some sandpaper.
It's best to sand the base board now because the legs will be attached next and this will make sanding the board a lot harder. 
When you have finished cleaning up your boards and making them perfectly smooth and square, you will have three boards resembling the three boards we have pictured in the image below. Please make sure to leave the marks on the main base board's ends and the edges of the leg boards. We're not finished with those lines, so be sure you don't go crazy and sand them off.
Now we are ready to assemble the legs onto the main base board! There are countless methods of connecting these boards together. You can screw them together with wood screws, or you may choose to fasten them together with nails of some sort. These are the fastest and easiest methods, but we have found that they have problems. Nails and steel screws tend to rust, and that can leave a stain and look messy. Nails and screws are also prone to working loose under use.

Our preferred method of connecting the legs to the main base board is to use glue. Of course the best glue for all things water-rocket happens to be PL Premium Polyurethane! We put a small amount on each leg where it attaches, and put the main base board on top.

We assemble each of the legs onto the base the same way, using a clamp to hold the boards firmly together until the glue has cured. If you have clamps like ours with rubber pads to protect your work, you don't really need to take any special precautions. if, however, you have metal faced clamps then you will want to put some scraps of wood under each contact point to protect your wood from getting marred or dented by the clamps.
Before you fully tighten your clamps, make sure the center markings on each leg line up perfectly with the center line markings on the ends of the main base board. Also make sure to use a square or right angle of some form to check that the legs are at a perfect right angle to the main base board. Tap the wood with a block of wood or the palm of your hand until you have it perfectly lines up and tighten the clamp fully. Don't over-tighten!
After the glue has fully cured, you can remove the clamps and you will be nearly finished with this week's tasks. You may want to sand off the center lines and when you have finished beautifying your launcher you can then mount the plumbing loosely on the top of the launcher with the U-Bolts. You can sit back and admire your work and enjoy a job well done!
Come back next week. We hope to have some results of a new parachute test and some results from an effort we have been making to reduce the spinning our rocket has due to the high speed of it's ascent. If the weather holds out, we should have those results for you! In any case we will also put the finishing touches on the release mechanism for our launcher!

See you next week!

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