Enhancing the Removable Box Fin Design.
Introduction:In this tutorial we will demonstrate a few enhancements to the Removable Box Fin Tutorial which you may find useful. Before you begin this tutorial, you should familiarize yourself with the construction of the box fin design by reading the box fin tutorial first.
The first improvement we will make is to modify the fin design so that it is adjustable to fit multiple bottle diameters. This way you can make a single set of fin designs and use them on multiple water rockets. You can even change them or exchange them depending on wind conditions or if you alter the length of the rocket by adding or subtracting pressure vessel modules.
The next improvement we will make is to alter the attachment method for the fins. If you fly in an area prone to landing in trees, you can modify the design so that it will break away from the rocket with less force. This can make the rocket easier to rescue from a tree.
Step 1: Measure your bottles and construct a box fin set:The Adjustable Box Fin design will fit multiple bottles, but you must make sure that the fins will fit the largest bottle you intend to use. Locate a bottle of that size and consult the Removable Box Fin Tutorial for instructions how to measure and cut a box fin template to fit that bottle. All other smaller bottles will automatically fit.
Step 2: Score the fins to make hinges:Score each fin along both edges of the Velcro tape. Only cut through the top layer of the corriflute plastic, forming a "living hinge" on either side of the Velcro. The fins can now be taped together in the usual manner to form the fin box.
Step 3: Test the hinges:Squeeze the fin set and see how it constricts toward the center. This is the way in which the fins will be adjustable. By contracting to the middle, the fins can shrink down to fit any bottle size smaller than the one used in the original template design.
Step 4: Make fin attachments for each rocket:For each rocket in your arsenal that you wish to use this fin set with, you will need to apply the appropriate Velcro strips as described in the Removable Box Fin Tutorial. Make sure you have the correct mating strips (hooks or loops) before you place them on the rocket. The adhesive can be difficult to get off once applied.
Step 5: Attach the fins:You may now slide the adjustable box fin set over one of the rockets and contract it until the fin set contacts the Velcro on each strip and the Velcro hooks together.
This completes the adjustable part of the box fin design. The photo gallery shows what the fins look like in various rocket applications.
Step 6: Customized fins:You already are aware that you can customize the shape of the fins themselves, but you can also change the number of fins in your fin set. The adjustable nature of this design means you can add more fins to 'grow' the fin set for even larger rocket diameters.
Step 7: Breakaway Fin Modification:If your launch area has a large potential for snagging your rockets in trees or other obstructions, you can modify the attachment of your adjustable fins to for a 'breakaway' mounting scheme which will make it easier to recover the rocket should the fins become snagged in something.
Instead of using Velcro, you will create only a single living hinge on your fins and you will trap the hinges against the rocket using bits of a small wooden dowel which are held against the rocket body using rubber bands.
In the event of a tree capture, the rocket will be easier to recover because the rubber bands can be pulled off if the fins snag on something.
Also, if the rocket is snagged by the fins in a tree that is out of reach, the rubber bands will deteriorate over a few weeks as they are exposed to the weather and will eventually fail, which can free the rocket without any intervention.