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How to tie bands with dyneema wishbone

dyneema wishboneby: Pau Diazbel

Dyneema wishbones are the must of especially the wooden guns. Silence, safety and easiness of change can be listed as some of the pros of them. Our forum member Pau Diazbel listed the steps that one has to follow in an operation to have some.

dyneema wishboneThis time I used black 19mm Ø bands. We will apply the most popular rule of TRIPLE EXTENSION.

To cut the band, we have to measure the distance between the muzzle band hole where we pass the rubber, up to the last notch in the spear (there is no standard measures).

In our case it is 92 cm in this speargun. If the distance was 100, I would have to change the numbers.

Formula : 92 – 3.5 cm of wishbone = 88.5 cm

88.5 cm/ 3 = 29.5 x 2 (the both sides of section) = 59 cm

But finally I decided to cut it shorter, exactly at 57 cm (from knot to knot) plus 1 cm to have the margin necessary to make the cones. Don’t worry, it will resist.

dyneema wishboneIts necessary to use a strong cutter or pliers to cut a band. I tested different pieces to put into the band to form our loop and finally I chose as the best option the green one in the photo.

You can use 2mm Dyneema like the black one in the photo as the diameter of this knot is enough to ensure the right resistance. In this post I have used 1.5mm Dyneema and inserted a plastic ball into the band for extra support. This method and dyneema of 2mm gives me most confidence.

The little ball has 8 mm Ø exterior and a hole of 3.8 mm Ø. It’s good for dyneema 2 mm Ø, but too wide for the 1.5 one.

dyneema wishboneWe need a bit of soap to put the piece into the band, if not it’s impossible.

Use pliers to insert the balls in the bands until we reach the correct position

dyneema wishbone

To do the constrictor knot you can use different lines 1.4mm Ø, in any case you’ll need at least 35 cm. A small amount of soap/wax over the band is good to avoid cutting on the band with the tight knot.

Preparing the knot

knotAfter I took the photo, I realised it had not been tied correctly and it was retied. Follow the instructions on the following picture to tie a constrictor knot correctly:

We need to tie the knot as tight as possible to make it secure. Once you are done cut the excess constrictor knot line and burn the tips. Don’t worry if the flame is too close to the bands.

dyneema wishboneWith a robust pair of scissors we can cut the excess band rubber quite easily, to make the ende as a little cones, more hydrodynamic.

We then smooth the cones with a grinding stone . We can also use a drill mounted sander, but that is more dangerous.

We then join the two loops we made with 2mm dyneema. For this we need to cut dyneema of about 10cm as less could be difficult to work with. I believe the simplest and best knot is the “Sheet Bend” which is shown below


Pay close attention to the length of the wishbone. There should be a max distance of about 8cm between constrictor knots (7 in this case) The wishbone length should be around 3cm . There are some that use 2cm and swear that it works properly.

As you can see, the cones are minimum.

For further information: Forum Medfish

dyneema wishbone

Categories: Tips - Tricks