Guide Sizing – Inner Diameter

In earlier postings,  I documented my understanding of the static weight of affixed guides on a fly rod blank (top) and determine there was a point of diminishing returns.  Also after some experiments, I have decided to move away from the 90’s wisdom that larger guides are better for shooting line and created a baseline for guide size selection.

I continue reading and came across a couple of articles-discussions from one of the old masters – Tom Morgan – who advocates for the smallest guide possible – weight saving and better directional control (reduce wobble-vibration) on the cast. On the Snake Brand’s website Tom recommendations were finer than mine.

Having never seen a guide fail, I asked when is a guide to small?  My answer became, when it is too small to “freely” pass a line.

So I started measuring some lines and using Al Buhr’s Line Design Book as a reference, here are my observations:

• The fly line is not the big object to get through the guides, but it is the junction between leaders, multi-tip loops if you have them and the connectionn to the backing. The importance of these junctions is dependent upon the application. Examples:

Starting with Trout Rods and Lines

• In trout fishing, rarely do you get into the backing and with the exception of European Nymphing Techniques, the leader is usually fully extended beyond the rod. As such for a traditional trout rod, you are only concerned with the diameter of the fly line.  Typical maximum diameters on a specific plastic fly line  (from measurements) being:
  • 3wt: 0.039″ to 0.043″
  • 4wt: 0.043″ to 0.49″
  • 5wt: 0.044″ to 0.050″
  • 6wt: 0.052″ to 0.060″
• It was noted the thickest lines were Wulff TT and Airflo 40+ Tapers (no surprise).
• Silk Lines are reported to be finer.
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• Given all these diameters are much smaller than any snake guide, there is no such thing as too small of a guide for  a traditional trout rod!  The only consideration-exception is some European Nymphing Technicques, such as the French Leader, were the leader to line connection is often in the guides, so here we need to consider the impact of junction.
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• How big is this junction? Having measured my many lines, I notice the variance in the diameter of these loops was substantial, from 0.090″ to 0.165″ (excluding Spey Lines). Admittedly some of the fat connections were ones I created, so I set off to  create the best junction with the resulting construction being (as illustrated below):
  • Maxima Chameleon 25 lb Mail Knot onto to a fly line with a prefection loop f0r the leader. The resulting maximum diameter being 0.090″ to 0.100″ – matching or better than the best OEM Loop (a RIO Trout LT 5 over 0.100″).
  • If you are trying to pass OEM loops, be prepared loops as large as 0.150″ on a trout line. If the OEM loop is bulky (greater than 0.150″) replace with the aforemention nail knot 25lb Maxima Chameleon loop.
    • Sidebar, I was once advised to use Mason Hard 30lb for this connection, but I found it too stiff, in that it harm the even energy transfer from line to leader and tied bulky nail knots.  After some experimentation and casting, I settle on Maxima’s 25 lb Chameleon to transition from line to leader.

How does the opinions of Tom, my measurements and reflection influence my line guide selection (at the top)?

• 3wt & 4wt Traditional Fly Rod: Use  Size 1/0 Snake Brand Guides.
• 5wt  & 6wt Traditional Fly Rod: Use Size 1 Snake Brand Guides.
• An European Nymph Rod: REC Single Foot Recoil – Size 2.
  • Also exploring the Hopkins Holloway Single Foot Guides to.
• And if I (you) fancy a finer rod, then go one size down!  But for now, I will keep a little more space to pass through the leader knots.

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Some guide inner diameters to help me reaffirmed matching “line size” to the guide.

Please note the measurements were not with the best tools (to counter the twist), so my estimated accuracy is +- 0.01″. And yes, Snake Brand Guides are smaller.

Next posting(s), measurements as it pertains to Bass, Pike and Spey Rods.

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