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Hints & Tips 2

Dr Paul Davis makes regular appearances in the Guild's newsletter contributing - amongst other things - many useful hints and tips. Here are some of them:


A tip worth the weight!

As I was tying a batch of north country spiders that had wire ribs the other day the following came to me - and although this may be well known by some of you and written about elsewhere I thought it was worthy of passing on because I have not heard it mentioned before, and, in the words of Blackadder, this idea is so cunning you could pin a tail on it and call it a fox.
It is easy to spot weighted flies that have bead heads or super heavy lead underbodies (such as Czech nymphs) - however, if you tie patterns that can be both unweighted and also moderately weighted with an underbody of wire then it is difficult, if not impossible to tell them apart when you look in your fly box on the bankside. As depth is one of the critical factors in catching fish how can you then select the correctly weighted version of a fly?
Well, I now use the following rule. If one of my flies is tied unweighted then the rib is tied in clockwise - so if you look at the body of the fly it will look like this



However, if you have put a weighted underbody on the fly then the rib is tied in anticlockwise and the body of the fly will look like this.


This is from my perspective as a right-hander but of course, if you're left-handed it will be the other way around.
Now at a quick glance, it is simple to see which is the heavier fly and appropriate for getting down to the correct feeding depth of the fish.

Hanging by a Thread

Thread, silk, cotton whatever you call it, it is probably the most important part of a fly other than the hook. Have you ever experimented with different threads early in your fly tying career leading you to choose a favourite thread? I certainly did. Human nature being what it is means we often stick with that same thread through thick and thin and only change it when we can't get it anymore. Well, I started to wonder what those other threads were like, of course, my favourite thread got jealous and we had a bit of an argument along the lines 'how could you leave me after so long which was quickly resolved when I was only doing this in the name of science and the fly dressers guild.

Therefore for those with an enquiring mind but don't want to upset 'the thread indoors' do you ever wonder how the different threads compare against each other? What does 70 denier mean and is this the same as 8/0. Does 8/0 thread break with 2lb of pull or 2ozs?

Well, I decided to try and pull together a definitive chart. I hope that I have got all of your favourites in here - if not send me details and I'll add them to the chart. It is not complete, by any stretch of the imagination but it'll do for now and I'll add extras if anyone wants to send me a spool of thread to test. I have tried to get the manufacturer specifications for each of the threads and where there are gaps either the manufacturer doesn't know or isn't saying! One other thing I also need to point out is that Gudebrod has stopped making fly tying threads and only a few suppliers in the US and UK still sell this - but seeing it is still found in some fly tyers boxes I've put it in.

If we are going to make any sense of the comparison table we are going to have to go back to basics with the fundamental questions of what do those strange symbols and language mean on a spool of thread? Well, basically they are a notation for the fineness or sheerness of the thread.

The first attempt at some sort of thread notation was the 'nought' scale. This was based on a system where the number 0 or "nought" was the base point (i.e. the company standard) and as the thread became smaller additional zeros were added indicating that the thread was finer. As an example, a thread with six zeros (000000) translated to a 6/0 thread. As other manufacturers appeared they followed the same system however each company had a different standard for its base point. As more brands became available, the accuracy of the "nought" became pointless unless compared within the same company. Now it is often I say this but thank goodness for the French as they 'invented' the Denier scale.

For those who didn't know Denier is a measure of the fineness/sheerness of thread. It is based on the number of grams per 9000 metres. Therefore a 70 denier thread weighs 70 grams. Therefore the finest thread has the smallest number.

Of course, it couldn't stay this simple. The international drive for decimalisation and the use of SI units (mm, km, kg instead of inches, miles and pounds) created the Decitex, which is the weight in grams per 10,000 metres and is the officially adopted unit of thread fineness (NB, of course, it has been adopted by the EU which means that nobody actually uses it but it is here in my table just for completeness).

There is a correlation between denier and breaking strength of nylon and polyester thread. The smaller the denier numbers the lower breaking strain sounds obvious and of course, it is however when you get onto comparing Kevlar and GSP (Gel Spun Polypropylene) threads they are much stronger than their equivalent nylon of polyester threads therefore they can have a higher breaking strain for the same denier.

The fineness or breaking strain of a thread is not the end of the matter, there are other issues such as can the thread be split for dubbing loops? does the thread lie flat if twisted against the roll of the individual fibres? how slippery is the thread? and does it grip all materials well? The list goes on - but basically, you will need to try the threads to find the ones you like and suits your tying style (just like choosing a rod to match your casting style). Hopefully, this table will point you in the right direction to start trying other threads. Good luck if you do!

NB Don't forget that you can view, print or download the PDF of the definitive chart by clicking here.

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