: After looking at alot of the commercial Sea/Touring Kayaks available, I
: noticed that many are in the 13.5 to 16 foot range while most plans or
: kits for strip builts are starting at around 17.5 to 19+ feet. Are there
: reasons why strip builders don't build the shorter boats?

Aside from lee's comments, which I am in complete agreement with; most strip built designers are skilled paddlers and they design boats that they themselves would like to paddle. They're generally 'sea' kayakers and not 'recreational' kayakers.

: What are the advantages to longer kayaks other than speed?

Longer kayaks have a higher top end speed. This is only useful if you are a good enough paddler to keep the boat up at that speed. Otherwise, it's unused wetted surface which contributes to drag.

Narrower kayaks have less wetted surface than wider kayaks with the same LWL.

: Are they harder to
: navigate

No--navigation is in the hands of the paddler. Boats don't navigate themselves! ;) Longer boats, though, generally track better than shorter boats of the same design, so not having to fight with corrective strokes all the way across a multi-mile crossing is a plus.

: (are they harder to)..turn around than shorter boats.

Yes.

:Does a person's weight and
: height mean anything in selecting a kayak design??

Yes--your weight more than anything, but your height is important in that you must find a boat that can accommodate long legs and big feet, if you have long legs and big feet. Like the mutant who is posting this response with his 6'-6" frame, 38" inseam, and size 14's.

: I don't plan on encountering much rough or coastal water mostly small rivers
: and lakes.

A boat in the 16' range and 24" beam might be fun. Boat selection, though, is highly subjective, and I can't tell you what's best for you.