My Line Knotting Machine (mk 1)

Introduction

Ever since I did my PADI Cavern course in Florida way back in 2007, cave diving as entranced me. There were a couple things that really hooked me about it :

1. The exploration – I’m going somewhere that only SCUBA divers can go, and even then about 0.01% of the diving population can do it successfully and safely (for once I’m glad to be a statistic). The idea that I could be travelling and seeing things that no one has seen is fascinating
2. Because of this, just the thrill of swimming along and seeing your torch light disappear ahead of you is exciting.
3. Ironically, hitting your turn pressure and looking down the passage way one last time to see the passage bend and travel beyond your light makes  you think “I wonder what’s down there…”

Once I got into cave diving, I then started hearing about WKPP. Watching some of the documentaries shows how incredible the diving is that they are doing. But one thing that really caught my imagination is the surveying of caves to model where they are going. And as such its something I want to get formal training in, but , this is where this article kicks in, one of the main tools that you need for cave survey is a knotted line.

Knotting

Knotting line is actually a bit of an art, certainly not one I've perfected, but I have found some bad ways thats for sure! I’d tried in the past pulling the line of my reel and using a tape measure but that lead to a very slow process and actually wasn't that accurate. I came across a video on YouTube by Steve Bogaerts who showed his basic rig for knotting vast amounts of line very quickly.

Steve Bogaerts Line Knotting

All credit must go to Steve for my MK1 line knotting machine for its design.

Chris’s Line Knotting Machine

One thing I wanted to do differently to Steve was to knot my line every metre, whereas he was knotting every 10’, approximately 3.3m. The first important design parameter is that rather than knot his line at 10’ intervals, he actually knotted at 9’8’’ to account for tension and line stretching. This is about 3.4%. So whereas I want to knot at 1.0m intervals, I will actually be putting in a knot at about 96cm.

Making the line knotting machine

The line knotting machine is extremely simple, the main body is just a length of wood. The length of this needs to be at least two-thirds, ideally three-quarters of the spacing of your line knots. For me, my knots are at 1M (effective) intervals, so my piece of wood needs to be about 66-75cm long.
Bill of materials:

• 1 piece of wood (length described above)
• 2 off eyelets
• 1 off spike/carriage bolt
• Spool of line

All you need to get knotting!

 Step 1 - Insert spike

At one end, drill a hole for your spike or carriage bolt, then screw the spike/carriage bolt in place. This will hold the bobbin in place when you come to making your knotted line.

Pre-drill then screw in your carriage bolt/spike.

Step 2 - Mark far eyelet

At the opposite end you will need to insert one of your eyelets. Measure a point about 1cm back from the end of the wood so to prevent splitting when you insert your eyelet. Mark the point with a biro pen.

Step 3- Identify knotting point

Next has a bit of maths... So I'll do it step by step.

1. Decide on your distance interval between knots.
2. Take off 3.4%
3. Divide it by two.

In my case I wanted 1 metre between knots so following the steps above for me is :

1. Interval = 100cm
2. Remainder = 96.4cm
3. Half = 48.2cm

This is the distance from your first mark going towards your spike. Measure this point out and mark it on the wood with a biro. You should make this mark as heavy as you can as you want this to be permenant.

Measure the distance carefully.

Step 4- Pre-drill holes

Pre-drill and insert your eyelets at the first point you marked. You will want a second eyelet about 1-2 inches away from the heavy line you marked.

Eyelets inserted.

JOB DONE!

Using the knotting machine

To use the knotting machine, you need to unwrap your spool and make a loop - this will be the start of your line when you are pulling it off your reel. You then want to thread it up through the first eyelet (the eyelet in the middle in the image above) through the far second eyelet (in eyelet on the right in the image above) and then back through the first eyelet (the eyelet in the middle in the image above).

With the loop and knot in your right hand hold it on the line you have marked, then put a gentle bit of tension on the line with your left hand. Pinch this point with your left hand - this is where you will knot the line with a simple overhand knot.

Pull the line through so that the knot you just made is now on the marked line, repeat the process for more knots.

I've tried to explain this a bit better with my sketch below:

Running line through the knotting machine.

 Conclusion

That sums up my implementation of a line knotting machine as per Steve Bogaerts. Hopefully you will find that helpful for making your own if you are interested in cave/wreck survey and in need of knotted lines as part of your diving.