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Water Rocket Self Aligning Fin Brackets

When building our rockets, we noticed that the alignment of the fins has a profound effect on the amount of rolling or spin the rocket experiences in flight. The spinning can be annoying because onboard videos from a spinning rocket make some viewers experience a mild motion sickness, and the spinning action takes energy that would otherwise make the rocket go higher. Our solution to the problem was to create a self aligning fin section that we call the Box Fin Assembly. We have a tutorial showing how this is made on our website that the following link: Box Fin Tutorial

The box fin does a great job eliminating the rolling motion because it forces the fins into perfect alignment at all times, but because of the shape of the box fins, it is difficult to add side boosters to a tocket that uses them. We decided that it would be good to have a self aligning fin assembly that had a traditional form factor that would allow the use of boosters. After a bit of brainstorming, we came up with a special fin bracket that does the job very well.

We put our new 3D Printer to use making our fin brackets, but there's no reason something similar could not be made from scratch using fiberglass, plastic, wood, etc. The 3D Printer just makes producing a lot of brackets as easy as pressing a button, walking away, and coming back later to collect the parts. Using this technology also allows us to configure the printer to print the brackets as hollow shapes, meaning that they are very lightweight.

Each bracket mates with the one next to it and forms a channel that holds the fin in place, while features on each of the bracket ends will allow the brackets to mate and lock together in alignment.

The fins are cut from a corrugated plastic known as Corriflute, which is strong and very lightweight, since it is hollow. We made notches in the fins so that they would accept the brackets, and then drilled holes so the brackets could be fastened through them with nylon screws.

These brackets are designed to interlock together and form a channel that holds the fins in perfect alignment. Holes in each end of the bracket connect them together and to the fins, using nylon screws, which makes the brackets totally nonmetallic, and therefore competition legal.

Brackets are connected together in the same manner, until the entire rocket is encircled. Since our fins are large, we chose to use two rows of brackets, instead of one large one.

The Fin Brackets are flexible enough to withstand the swelling of the Water Rocket when pressure is added, because they are made from semi rigid plastic. Even when pressurized, they do not flex or shift position.

In testing we found that the brackets helped with the rolling motion considerably, and they also make the rocket look much more polished.

During our testing, we even had an unplanned durability test that was caused by a ballistic flight and crash that damaged the rocket but left the fins perfectly fine. In case you were wondering, the crash was due to leaving the rocket powered up between flights which accidentally drained the battery.

We have a video on our YouTube Channel that goes into more detail, and shows our rolling test measurement test flights. If you'd like to see how impressive the difference is, then go check out the video:

3D Printed Fins Video:

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