I think this chart might help you out. http://www.flyfishingforum.com/expertise/knowledge/lineratings.htm

...and here is an article that explains the line weights in more detail.
http://www.activeangler.com/articles/flyfishing/articles/doug_macnair/lines1.asp

Trevor

 

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From the charts that Trevor posted I can see that grain weight and line weight or rod weight are the same thing. The article I was reading referred to grain weight of floating lines so I assumed it had nothing to do with their floating or sinking ability.
I think that to avoid confusion this particular guide service should use rod weight instead of grain weight or use both.
Thanks for the reply :thumb:
Blessings
jesse clark

 

. . . I think that to avoid confusion this particular guide service should use rod weight instead of grain weight or use both.

In the context of your original post, you're exactly right. But for me and perhaps others, the grain weight of a line is an important consideration for a couple of reasons.

First, I have many more lines than I do reels or spools to put 'em on, so I've got a number of lines in my drawer that aren't always labeled with their weight or type. Umpqua's line scale comes in handy when I'm trying to remember whether that yellow line is a 4wt or the 2wt I misplaced. I just measure out and weigh the first 30 feet of line (without a leader) and the scale indicates its grain and line weight.

Secondly, recommended line weights aren't always indicated on bamboo rods, especially on older ones, or the recommended line is in the old letter weights (ie. HDG) which don't always translate into our modern numeric weights. By accidentally fishing a cane rod with too heavy a line, I managed to put a major set into its tip (a set is bend in one of the sections usually induced by stressing the section from playing a heavy fish or overlining.)

When I had the set removed, the craftsman also calculated a stress graph with various line weights for the rod showing points along its length where it would be weakest and thus more likely to take a set when overlined. From this we determined that the rod was best with a 5wt line. Using the Umpqua line scale, I measured the sinking line I had been using and found it was about a 6-1/2wt or 7wt.

K

 

For accurately weighing and identifying heads and lines; Aaron Reimer, our own "Speybum", has a nice little electronic gram scale offered on his River Run Anglers webpage. I saw them a few months ago in the shop- my next new toy:

www.speyshop.com

 

Jesse - that would be way too easy!

To complicate things, many folks use a line with an AFTMA rating that exceeds the AFTMA rating for the rod, in order to overload the rod. I think the guide service is looking at the weight of the line that is commonly needed for the conditions reasonably expected to be found in their locale, regardless of the rating of the rod you use to throw it.

 

As for the sinking line part, keep in mind that grain weight has very little or nothing to do with sinking lines. Sink rate is all about the density of the line. The analagy of a pound of feathers sinking WAY slower than a pound of lead helpd. Very dense and thin lines (sink types III+) "slice" through the water and sink relativley quick and sink types of "intermediate" or type I or II are "fatter, less dense" (but have the same grain weight for rod loading) and sink slower.