Fly weight & drag

[Dave Warren]

Hi all, I sell a lot of pike flies and fly fish for pike using larger 8-12” long flies. Some people also request flies as long as 16”! Now a question I see a lot from ‘pike fly’ anglers is what line should they use to throw these larger flies. Of course it’s probably not all that simple to answer as some of the flies have far more drag than others, some are heavier, some weigh a lot more when wet etc. Some anglers are only casting 20-30’ and when I watch them it looks awkward like the fly line isn’t really doing the work. The majority in the UK are throwing or trying to throw these flies on #9 and #10 rods, some of the flies may way 7g plus when wet.

My question to you, is there a correlation between fly weight and recommended fly line? I guess there must be but has anyone tried to figure it out?

[Paul Arden]

Hi Dave, yes there is in fact it’s something that’s come up quite a few times recently for example here viewtopic.php?f=11&t=3299
And indeed James page today https://www.sexyloops.com/index.php/ps/cross-over And a couple of other topics. James has proposed a few experiments because it’s an interesting question!

Cheers, Paul

[Merlin]

Would a skagit outfit be appropriate?

Merlin

[Torsten]

Hi,

I think there are lots of variables involved such as mass, balance point/center of mass, drag of the fly etc.

I could imagine that you can optimize the flight of the fly by tuning the balance point. I know that this is for tournament casting / spinning gear critical - we had once some plugs that performed badly, you lost about ~10m distance - the old trainer sawed one plug into two halves and found an asymmetric gas hole.

Today was an off day and I did some experiments - I tried cast one of my old pike flies on my 7.5g accuracy rod (that is a 1,8m long spinning rod). This fly is approx. 20 cm long and weighs 2.4 grams. Unweighted - I had trouble to cast much further than 10m, also the trajectory was strange. Then I added a 2,5 g lead bead in front of it, that easily helped to double the distance, now the flight was really nicely straight.

Another experiment was to cast such a fly with a cheap 200 grains micro skagit head that I've recently bought out of curiosity. So I tied a similar fly to this head with a 9 ft. leader, added 0.50mm running line and cast it on a 9ft/ERN6 rod. With very little wind support I got 25-27m - not bad actually - my usual gear is a 9ft/8wt. rod and a 9m/18 grams shooting head. I'd conclude that the linear mass density of the fly line is a factor for casting large flies.

So next time (when the travel restrictions are eased) I'll try to catch pike with a 5wt. rod - perhaps even a glass rod (?) - and a micro skagit head - I'm sure that will be fun.

Torsten.

[Merlin]

My question to you, is there a correlation between fly weight and recommended fly line?

I'm afraid there is no clear answer. What is pretty sure is that casting a heavy fly requires a short and heavy head. Line size is related to air drag, the larger the fly is, the higher line size must be. In terms of weight, a possible "scale" could be beyond the actual line characteristics. Let's take Torsten's example and the micro skagit head. 200 grains for let's say 7 foot head and the linear density of the line is close to 30 grains/ft. The heaviest current line (#15) has a belly around 20 grains/ft. A bit short.

Merlin

[James9118]

What is pretty sure is that casting a heavy fly requires a short and heavy head.
Merlin

Why short?

Cheers, James

[gordonjudd]

the old trainer sawed one plug into two halves and found an asymmetric gas hole.

Thorsten,
Does that mean its mass was smaller than other plugs of the same wind profile because of the interior void in the plug or did it tend to have a bigger drag profile because the shift in its center of mass caused by the void caused it to have a bigger form drag profile?

I think James idea of hollowing out a plug and filling it with varying amounts of shot is a good one. You would expect as the plug's mass increased its terminal velocity would also increase assuming its form drag profile remained the same.

Gordy

[John Waters]

Hi Gordy,

7.5 gram plastic plugs used for tournament distance casting have been known to have been drilled at the front end and heavy matter inserted, then had the plastic filings glued back over the hole. Same profile, greater weight. Certainly cast further than the unaltered plug. There was also a lot of experimentation done years ago to alter the smooth surface of the plug that presented to the air whilst in flight. The background was to replicate the surface of a golf ball and gain metres in distance. The comparative distance achieved by the standard weight, smooth surface plugs was less than that achieved by altered plugs, either added weight or surface modifications. Rules were changed to have plugs examined to prevent these modification occurring.

John

[Merlin]

Hi James

I consider fishings casts and the necessity to have a minimum of momentum for the line to avoid the (large) fly overtaking it soon (it will likely overtake in the end). On the other side the rod and line system should remain fast enough, so there is a limit for adding weight with the line. Consequently the necessary weight of the line (linear density) has to be moved forward which means that if I consider a heavier/larger line for a given rod, the length of the "head" will correspond to that necessary weight and will be relatively short.

Cheers

Merlin

[Torsten]

Hi Gordy,

Does that mean its mass was smaller than other plugs of the same wind profile because of the interior void in the plug or did it tend to have a bigger drag profile because the shift in its center of mass caused by the void caused it to have a bigger form drag profile?

As far as I remember he said this was an official plug that they got from the tournament organizer - weight was OK but an asymmetrical void inside. Such casting plugs have the tendency to "flutter". Some tournament casters check their plugs by rotation (with a bit of mono attached), if they're unstable (trundle) they're sorted out. Heinz does this here at 3:10

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Back to the topic:

Merlin wrote: ↑Wed Mar 10, 2021 1:08 pm
What is pretty sure is that casting a heavy fly requires a short and heavy head.
Merlin
Why short?

Many pike lines have today a ~30ft. head. I like myself also such a length for shooting heads, the reason are minimizing of false casts, restricted casting space, often I'm using a float tube. I'm choosing the head weight between +1 or +2 classes of the rod spec, for an #8 rod between 15-18 grams. This works for me with up to 25cm flies. For larger flies I'd probably choose a 10wt. and 25 grams heads, but I don't enjoy casting that.
Integrated lines with such short heads often don't conform to the AFTTA standard so you need to check the head weight.

Micro skagit heads are just an experiment for me, have yet to try that on water.

Torsten.