Mohawks 30 Lb Draw PVC Recurve Bow

About:

An inexpensive, fun, relatively easy, and effective way to make your very own recurve bow.

Welcome

Hi, we are Michael Grebeck and Dylan Romero of the Wilkes-Barre Area STEM Academy. For this year's BEST Award we have decided to create a PVC Recurve Bow. We worked very hard on it for over a month to get this bow just right! We had many problems along the way that needed to be solved such as finding the correct type of PVC pipe to use, symmetry and balance of the bow, and making due with a lack of convenient tools. Being in the STEM program helped us to come up with innovative solutions to the various problems we encountered along the way.

STEM:

- Science: We used this aspect of STEM when observing the effects of exposing PVC pipe to high amounts of heat and noticing that when exposed to high amounts of heat, the PVC becomes extremely malleable for a short amount of time and is able to be molded into whatever shape without becoming significantly more brittle to where it would effect the strength of the bow

- Technology: Technology, in this project, was one of the lesser needed aspects of STEM for this bow, as it is mainly a mechanical object. However, we did need to use aspects of technology such as a heat gun to heat the bow into its malleable state.

- Engineering: This part of STEM was probably the most utilized in our project. We had to use this in the actual shaping and balancing of our project with a high degree of exactness for the bow to be able to function correctly

- Math: We used this part of STEM when figuring out all of our measurements for the bow such as how long the bow should be, how long the recurve tips should be, and how long to make the handle so that the bow could function as well as we wanted it to.

All in all, we ended up creating a 30 pound test recurve bow out of PVC pipe and paracord string. It's pretty amazing what you can do with such simple materials, as well as it looking and feeling just like a regular Recurve bow you would buy at the store.

We went to our local Home Depot, for most of materials we bought and used. The following is a list of items and their cost.

Items Needed + Cost of The Parts We Bought

1. 1 - Dry erase marker

2. 1 - Measuring tape (Must be at least 4 feet long)

3. 1 - Length of 3/4 inch diameter Electrical Grade PVC pipe (Must be at least 4 feet in length)

4. 1 - 1500 watt heat gun (sold at Harbor Freight for $15.00)

5. 1/8 in. x 50 ft. Polypropylene Paracord Rope, 160 lb work load. (bought at home depot for $2.48)

6. 1 - Rag or thick piece of cloth

7. 1 - Hacksaw (or any saw that can cleanly cut through PVC)

8. 1 pair of sheet metal clamp locking pliers (We used a trigger clamp instead of this as we did not have access to a pair of these)

9. 1 - 1/8 in diameter rat tail file

10. Optional: Spray paint cans (Approx.$6 a can) In all we spent about $31 to make this bow. If we hadn't used any spay paint we would have spent about $23 in all on this project.

1. The first thing you want to do, is measure your PVC out to 48 in. and cut your bow at the 48 in. mark.

2. Next, you should make a dark line with the marker, 6 inches from the end of both sides. This is going to be the part of your bow that will be Recurved.

3. Make a dark line on the halfway point (24 inches) and then make a mark 2 inches in both directions from the center mark. This area will be the handle of your bow.

(be warned, this is a relatively small bow comparable to that of a sort of cavalry bow, so don't be disappointed with the size if you were expecting something bigger. It is still a fully functional and powerful bow)

Step 1: Set up your heat gun so that it is standing up as shown in the video. We found this to be the easiest way to heat up the PVC evenly.

Step 2: Turn your heat gun on to high heat and hold the PVC about 3 to 4 inches above the nozzle. While rotating the PVC, run the section on either side back and forth between the 6 inch mark from the end, and the 2 inch mark from the center, slowly to evenly distribute the heat throughout the limb. (if the PVC starts to brown and burn, you are holding it too close to the heat gun)

Step 3: You will notice the PVC start to sag and flop around, DO NOT get over excited and take the PVC off the heat right away. Make sure the PVC is evenly softened throughout the entire limb. When this happens, take the PVC off the heat (turn off your heat gun) and place it on a flat surface (you will have to act rather quickly here) You will then take your rag and push down on the PVC starting lightly at the handle and gradually increasing pressure into the center region then decreasing in pressure out to the 6 inch mark. Continue pressing down going back and forth up the PVC until it is approximately 1/2 inch thick in the center region.

Step 4: When your bow limbs have cooled but are still slightly warm, bend the limbs slightly to give the limbs a slight curvature that would be characteristic of a bow

Step 5: Repeat this exact process on the other side (If at any point the PVC cools too much to press, Just reheat the PVC until it is malleable again)

This is a relatively simple step. Once your bow limbs have cooled down fully, turn your heat gun back on and now heat the middle section of the bow where your handle will be. once this softens, press the sides of the handle to make it thinner and wider, opposite the thickness and wideness of the bow limbs. Refer to the video for an further explanation.

This is a three part step for both sides of the bow.

Part 1:

Step 1: with your marker, make a mark 3 inches from the end of your bow.

Step 2: Heat the PVC with the heat gun and bend the area from the 6 inch mark to the 3 inch mark, in the opposite direction of the curvature of your bow. Making sure to keep the shape of the PVC normal without any divots.

Allow to cool.

Part 2:

Step 1: Now heat from the 3 inch mark to the end of the bow and curve upward in the same direction as part 1 until the end of the bow seems to be level with the handle of the bow.

Part 3:

Step 1: While the end 3 inches is still warm (reheat if needed) use the sheet metal clamp pliers to clamp from the 3 inch mark diagonally to the end of the bow leaving about 1/4 in of PVC not clamped at the end of the bow.

Step 2: When it cools, remove the clamp pliers and use the hacksaw to saw off the excess PVC at the line created by the clamp. Use sand paper to smooth out the jagged edges.

Repeat this process on the other side of the Bow. (should closely resemble the picture)

Step 1: Measure 1/2 in. from either end of the bow and mark with your dry erase marker

Step 2: On the inner side of the curved end of the bow file out the nock for the Paracord as seen in the video. Stop filing when the file is about 1/8 of an inch deeper than the outside of the PVC.

Step 3: Use the file to smooth out any sharp edges that may cause the Paracord to rip or break.

Step 4: Repeat Steps 1-3 on the other side of the bow

Step 1: First you will need to cut your Paracord to an approximate length and tie your knots. (Refer to video for explanation on how to tie your knot.)

Step 2: Put both loops of your knots through the bow and attach one loop to one knock.

Step 3: Keeping the string taut, flip your bow and place the crook of the recurved end of the bow so that it is resting around your ankle. with your other leg, step through between the Paracord and the bow and move your leg so that the handle of your bow is resting on the underside of your knee.

Step 4: Now flex the bow while keeping the handle underneath your knee and move the Paracord up the bow until you've flexed it enough so that the string can be placed into the other nock.

You have successfully strung your PVC bow! Congratulations! you now have your very own PVC bow which costed you next to nothing!

This is what your final design should look like!

Optional:

Now what we did is bought specialty spray paint that sticks to plastic. You can find this at your local Home Depot or department store. We decided to use the colors of our school, blue and gold! You can now customize your bow to your liking!

Probably the most important aspect of any bow is how accurate the bow actually is. You may ask yourself "now how accurate is it really? It's only PVC". After doing many tests from different distances we have found out that Dylan is a better Bowman than Michael, but seriously, we concluded that it is quite accurate. Throughout our testing, we both shot the bow 15 times from both 20 ft, and 50 ft. From the 20 ft mark, Dylan hit the target 13/15 times and Michael shot 9/15. From the 50 ft mark, Dylan hit the target 13/15 times, and Michael hit the target 7/15. Dylan having a better shot that Michael, we can agree that it is considerably accurate. The videos above were just some of our trails. Another important aspect of any bow is how heavy the draw weight of it is. What we did to test this, is we took a 30 pound weight and tied it to the bow string, Leaving the weight on the ground, we pulled up on the bow, and as it pulls the string back to a certain point while being able to lift the 30 lb weight, we can determine that it has a 30 pound draw, as seen in the video. For people who hunt deer, the required poundage of draw, is 35 pounds. Our 30 pound draw is pretty close to being able to use to hunt deer. These tests were essential to testing the overall quality of the bow. As seen, for being a piece of PVC and Paracord string, it exceeds all expectations!

The chart above expresses the time we put in to the individual steps. In total the bow took approximately 13/14 hours.The majority of the time was spent on building the actual bow, making sure every measurement and action was taken correctly. There were a few problems we encountered when designing, such as the type of PVC to use. In order to find the correct pipe we not only had to find the best type of pipe we had to test each piece of pipe to make sure it was usable. Some lengths of PVC are more brittle than others due to ways they are stored or the way they are built, so we had to use a sort of hammer test with each piece of PVC. If you hit the PVC with a hammer as hard as you can, the PVC should bend and split. If the PVC shatters upon hitting it with a hammer, this PVC should not be used to build a bow. If the PVC is too brittle it may break under the stress of pulling the bow string back.

Main Idea:

Now that it is all said and done, we really thought it through, for what improvements we could make to a second version. When beginning our journey into making the bow, we were expecting the bow to have a 40 pound draw. Thinking about the design of our bow, we realized two things.

1. The limbs of both sides of the bow, are a bit thin. If somehow we were able to make them just a bit more thicker, that could fix the problem for our draw poundage. When pulling back the bow, all of the stress, is going directly to the thinnest part of the limbs, because that were it is the most flexible on the bow, and if this is too thin, it will be too easy to pull back. If we make it a bit thicker, it is going to decrease that flexibility. With the stress gone, it is going to make thee bow sturdier, causing it to increase the drawback. Overall, this would increase the draw poundage, making it harder to pull the string back.

2. As seen on the image above, the bow in the image compared to our bow, is more curved. What that does is, it puts more stress on those curves and adds tension which will allow for a heavier draw weight. If we were to make it more curved, this would increase the draw weight of our bow even more.

All in all, adding these improvements would essentially cause the bow be sturdier and firmer, therefore causing it to have a heavier draw, solving our biggest problem.

We both thought this section was necessary for you to understand the development in builders and working in collaboration that we have learned. In any type of project, especially when collaborating, there is going to be different type of workers. There's going to be different personality types, work ethics, and even ways of thinking. Understanding your role and your importance to the team is important. In this case Dylan was a Do-er. He was the one to get his hands dirty during construction and building of the bow. At first Michael was not sure if he liked it, but both realized what role they were going to play, and why it is important. During this process, Michael was more of a thinking and designer, not going directly hands on with the project, more or less supervision and explaining what and how to do something. We both felt like we weren't doing enough, but realized that this is a team. That we are the pieces to a puzzle, and we can't do everything. The things we are doing now is essential to the construction of our project. Overall, we thought it was necessary for you to understand the development as a person and as a collaborator, this experience gave us. Dylan learned in this situation, he was a Do-er, more on a hands on constructor. Michael realized that in this situation he was more of a thinker, and a supervisor, coming up with designs and how to execute them.

It’s been a long and heartfelt journey. From start to end, we have worked diligently and determined, to make the best possible bow out of PVC. We enjoyed every minute of this process, and can’t wait for next year. It was amazing how we were able to extend our meaning of being in the STEM academy to new limits. We would just like to thank you for this amazing opportunity to do this. We hope you enjoyed our instructable and take it into careful consideration.