How to Match Fly Line to Fly Rod when the Line Weight isn’t Marked on the Rod
By Allan Burgess
Some years ago, I purchased a two-piece graphite fly rod blank at an auction for a very good price. I checked it out before the auction began but there wasn’t any info about the blank. It looked to be of good quality, however, there were no markings on the rod so I couldn’t tell exactly what line weight it was designed to cast. From memory, I don’t think there were any other bidders. Building up your own rod blank from scratch seems to have gone out of fashion a long time ago. The matching fly line to rod could potentially pose a problem.
When I got it home, on comparing its stiffness to several of my other flyrods, I concluded that it was a fairly heavy blank and possibly an #8 or #9 weight. That would have been ideal because it was exactly what I was looking for as I intended to use it to fly fish for salmon and as a saltwater fly rod for kahawai and maybe even kingfish. I have a very strong Alvey saltwater fly reel with a powerful drag that works great on kahawai.
At the time I had no way of knowing for sure exactly what weight of fly line it was designed to cast. I was only guessing. I knew it was a 9-foot (2.75m) blank.
I decided to attach line guides and a reel seat to the blank and try it out. I wanted to use it as a purpose-built saltwater fly rod. Starting at the bottom I went for a stainless-steel reel seat with a fighting butt. This meant the rod would have an up-locking reel seat.
One advantage to making up a fly rod is that components are relatively cheap compared to say a big game fishing rod so I was able to use a quality reel seat and line guides.
Then I added two agate stripping guides to the bottom section, along with eight stainless steel snake guides and an agate tip guide to the top section. I won’t go into how I spaced or attached the line guides in this article.
Recently, I discovered “Calculating rod weight to choose the right fly line” by the Frugal Fly Rodder on YouTube. I made the test following the instructions exactly as described in the video, and the description below the video, and came up with a grams/length ratio of 3.8 making it a #9 weight fly rod. A tiny bit of maths is involved but it is easy with a calculator.
A graphite rod can be quite stiff for its diameter making it difficult for the inexperienced angler to gauge by just waving it around. The test confirmed my guess regarding the required line weight, though I admit it was purely by chance.
Anyway, I thought you might be interested in this, both to check the accuracy of the recommended line weights marked on your fly rods, and also if there are no markings on the rod at all.
I’m now much more confident that my 9-weight fly rod should be pretty good for catching a kingfish on the Collingwood flats. I reckon I need something like a Scientific Anglers Sonar Titan Clear tip WF-9-F/I Saltwater Fly Line?