Is it possible to build an ultra-light small trout rod on

a fly rod blank?

Yes, using a multi-piece fly rod as the base for a creating a conversion rod is something that IRC specializes in.  You should be completely comfortable knowing that when built correctly, these rods will be extremely durable and hold up as well as any other.

Is it possible to centre-pin, fly fish, and cast light spey on the same rod?

Exactly!  The switch is made by merely changing the reel, reel position, and possibly the butt extension.

 

 

What exactly is a "switch rod?" 

Plainly put, it is a word phrase to describe a rod's multi-functional capacity.  The term switch rod can be used to describe a float to fly rod, a traditional fly to two handed fly rod, a fly to spey rod, or fly, spey, and float rod capabilities.  What it means to the consumer is more function from their investment and consequently a savings to one degree or another.

 

 

How do these switch rods become multi-functional?

There are several configurations that will allow a rod to be used for more than one purpose.  Using a sliding ring reelseat or a series of removable fighting butts in different lengths are a couple of ways.  Selecting guides and blanks that can operate in a dual or triple purpose situation is done with your needs in mind.

 

 

What about species, can a "switch rod" be used for more than one type?

To some degree, the answer is yes. The most effective rods will built with a certain species "strength" in mind.  (example:  steelhead, carp, small salmon is one group or native trout & stockers, smallmouth, and small catfish as another grouping)