What is a Grain Window?

A grain window defines the engineered grain carrying capability of a fly rod blank under line load.

The primary purpose of posting the grain window on our two handed fly rods is to aide the caster in achieving a correct and balanced rod/line marriage. what is a grain window

How to use a Grain Window

The S2H13678MKS has a grain window of 500 to 800 grains, and we will use this rod as an example.

S2H13678MKS blank description:

  • 13'6" 7/8 wt MKS 4 pc
  • Speed of recovery: Fast/medium fast
  • Flex: Deep flex
  • Action: Progressive
  • Taper: Regressed butt
Recommended Lines     
13'6" 4 pc 7/8 wt MKS S2H13678MKS-4 <> Grain Window: 500 to 800 Grains
Short belly Spey Belly length to 55' Belly wt. To 600 grains
Mid belly Spey Belly length to 70' Belly wt. To 650 grains
Skagit Head Head wt. 550 to 600 grainsTips: To 200 grains
Scandi Head Head wt. 500 to 600 grains Head: 2.65 X rod length


How to use the low end of the grain window:  

The low end of the grain window for this rod is 500 to 600 +- grains, and would define the minimal amount of grains that will allow the blank to load efficiently.  
  • The low end of the grain window would most often be applied by those casters that will be sourcing power from the top 2/3 of the blank. Some casters may refer to this as "tip casting" or casting off the tip of the rod.  
  • Casting off the tip of the rod is often applied by those casters that will wish to deliver light grained shooting heads utilizing minimal anchor at both the D and dangle release. This is typical of classic Scandinavian style touch-and-go technique. This delivery is best performed with a very economic compact stroke, minimal caster expended energy, and predominant power sourced from the lower hand.
  How to use the high end of the grain window:  

The high end of the grain window for this rod is 600 to 800 +- grains, and would define the maximum amount of grains that  the rod will allow the blank to load efficiently.
  • The high end of the grain window would most often be applied by those casters that will wish to distribute power and grain load in such a way as to utilize the full work capability of the entire blank; taking power well into the cork. Some casters may refer to this as butt loading or deep loading the rod.
  • This is best demonstrated in two scenarios:
  1. In situations of sustained anchor management typical of Skagit style shooting heads with extreme sink tips in tow. The grain total managed here would be the combination of head and tip weight. A Skagit shooting head of 600 grain with 200 grains of T-14 in tow would net 800 grains... This would meet the high end of the grain window.  Overall anchor management and achieving constant tension of Skagits will best be accomplished with a compact economic stroke and minimal caster expended energy; utilizing predominant power sourced from the lower hand.  
  2. In situations of full-belly length line management of actual aerialized grains beyond the rod tip of mid to long belly classic Spey line systems. This scenario is often best accomplished with a more open stroke and longer sweep to manage longer belly beyond the rod tip. For this: Relative even power is best sourced from a balanced combination of both the high and low hand.