Making a pouch and sling

The steps in making a pouch are presented here, either as a Visio Version 5 drawing, or as a graphic image (portable network graphics format, supported by most browsers in these modern times).  Either save the Visio file to your computer to print directly from Visio on your PC, or if you don't have Visio then download a Visio viewer or use the links below for graphics versions of the plans. You can search for downloads of Visio viewers at Google

Here are the steps in PNG format, print them to fit an A4 page and they should print close to actual size.

This method probably isn't suitable for large trebuchets, though I'd imagine that if you used canvas or tarpaulin you could probably make something sufficiently strong to throw a counterweight that weighs a couple of pounds.

My chosen material is a plain and simple plastic carrier bag.  It's a bit tricky to work with as it's a little slippery when folding, but it produces a strong and light pouch suitable for small trebuchets.

The steps

Here are the step by step instructions, with photos of a piece of paper being folded.  You should start with a rectangle of your chosen material, which should be as wide as the circumference of your projectile and as long as twice the circumference of your projectile.

Step 1

Start by folding one long edge to meet the other, and opening the fold again leaving a crease running along the middle of the material.

Which should look like this...

Step 2

Next, fold each long edge to meet the crease in the middle.

Which should look like this...

Step 3

Again, fold each long edge to meet the crease in the middle.

Which should look like this...

Step 4

Your pouch material should look something like the image below, when viewed from one end.

Using a rule, you should mark two points along each long edge.  The distance between the two points should be half of the diameter of the projectile, such that the marks are a quarter of the diameter away from the centre of the long edge.

Which should look something like this...

Step 5

Take the left corner of the long edge closest to you, and make a fold that runs diagonally from the left hand mark on the edge closest to you to the left corner of the long edge furthest from you.  Do the same on the right hand side.

Which should look like this...

Step 6

Now, take the short edge you've created and fold it over to meet the long edge on the other side, and make a good crease.  Then unfold that last crease.

The crease that you make should look like this...

Step 7

Undo the two diagonal folds.

Step 8

Now turn the whole thing through 180 degrees.

Step 9

And repeat steps 5, 6 and 7 above.

Step 10

Now, take note of the folds that you've created, and take a sneak peak at the photos below because we're going to use some reverse folds to bring the ends of the material together.

Step 11

So, work the folds by squeezing the middle crease down while bringing the long edges together at each end of the material.  As you do it, it should look like this...

Then fold the two sloped edges together and press the whole thing flat.

Which should look like this... (Note, I've used staples to keep the paper example flat for ease of taking photos and because this paper pouch won't get stitched together to be made in to a sling.  You shouldn't use staples.)

Step 12

Now, snip off the ends as shown here and trim the pointy bits that have no hope of holding a stitch in place.

Finishing the pouch

Using the cord that you'll be using for the sling, you should stitch together the sides at each end of the pouch.  The stitches will be more-or-less where the staples are placed in the photo above.  Start from the inside end of the sides and blanket stitch along the edge to the tip of the end.  When you cast off the stitch leave an inch or two of cord with a knot tied in the end.  Make sure that the amount of cord you leave after casting off is of equal length on each end of the pouch, and position the knot on each cord at the same distance from the pouch.  We're doing this so that the sling lengths don't have to be adjusted should we have more than one pouch.

Forming the pouch

To form the pouch you need to part the sides of the pouch, and pull up the floor of the pouch to make walls.

The finished pouch

And here is the finished pouch, I've temporarily linked the cords on the ends of the pouch here just so you can see the formed pouch.

Completing the sling

The pouch becomes a sling when a piece of cord is attached to either side of pouch and attached to the trebuchet.  There is a fixed end, physically attached to the arm, and a loose end which is slipped over the pin at the tip of the arm.

My preferred method is to attach an eyelet to the underside of the arm not too far from the tip.  This is the fixing point for the fixed end of the sling.  Tie a loop in a piece of cord, thread the loop partly through the eyelet and then thread the other end of the cord through the loop and pull it tight.  The cord will then be attached to the arm.  Tie a loop in the free end of the cord and then use it to form a lark's head knot and attach the cord to the pouch.  Here's how:-

Now, the loose end of the sling is another length of cord with a loop tied at each end.  One loop is attached to the other side of the pouch using a lark's head.  The loop at the other end of the sling is used to hold a ring or washer that goes over the pin at the tip of the arm.  On a very small trebuchet, you'll get away with just putting the loop over the pin (i.e. with no ring/washer.)

With this method, the sling length can be changed just by using different lengths of cord with the same pouch, and the pouch can be changed without changing the sling length.  When you're tuning a treb this comes in very handy.  Small changes in sling length can be accommodated by putting a figure-of-8 stop knot in each side of the sling cord to reduce the length little by little.  Large changes are easily accommodated by replacing the cord and keeping the pouch.

This page last updated on October 29th, 2004
Created by hand using 1st Page 2000