I trust that the relative difference in potential speeds would have more to do with increases in hull length over what another pair of oars would add? 

Be interesting to read what other, more experienced contributors will post in reply. 

   I make no claim to special expertise, but here is my take:

The NEDory is a blast to row solo. I can cruise along at 3.7 - 4 mph.

If my wife comes along and she is just a passenger, is a bit more work to row and a bit slower (but more fun). Maybe 3.3 - 3.6 mph.

If she feels like putting a blade in the water, the boat comes back to life again with average speeds about the same as solo.

With two guys in the boat, working hard, it feels like a rocket! (No data, but I've done this briefly with my son.)

Birch2 I think your comments well illustrate what I'm getting at in mine!

One rower in a NED puts all the work on one pair of arms. Add a passenger the displacement goes up, wetted area goes up, work goes up... until the passenger takes over maybe one of those two oars, splitting the work between two bodies.

Once that passenger grabs their own pair of oars the increased muscle-power being put into the water doesn't really move the NED much faster but maintaining top speed is a lot easier on both rowers.

Rowing sculls pretty much maximize the equation - very long, skinny shallow hulls fitted out with several rowing stations, lots of muscle-power driving those skinny hulls to maximum speeds.

Putting a search into Google just now I've learned it's possible for modern displacement hull designs to exceed their hull speed which, before I read this Wikipedia entry, I thought wasn't possible. There's a link down that page that takes you to a table more to the point for rowed boats.

���Hay thanks for replying, good points, i didn't really know either way but more water line plus extra rower equaling close to same speed as less water line and solo rower makes since to me. So ive decided to row my skary under one set of oars, with or without my wife. I figure we can take turns or paddle a canoe if we both want to paddle, besides the skerry will be for mainly sailing.. thx again..

I remember reading something by Phil Bolger (can't remember the exact source) wherein he suggested that, for the long haul in a boat with two rowers available, it was better for them to switch off, one rowing while the other rested.  If the rowers were of unequal strength, having the stronger one row a longer shift, say 40 minutes to 20 minutes in an hour, would keep things going along at a good clip for a long period of time.  The whole idea was to keep both rowers reasonably fresh so that they could row in tandem more effectively when the extra horsepower was needed, say getting through a tight place againse a foul current or a stretch straight upwind against a stiffish breeze.

I always thought the Chester Yawl, with her flexibility of rowing stations and clear, flat floorboards, would make a good boat for a pair of hearty rowers to try the Everglades Challenge.  With one rowing while the other rested, slept, ate, fixed coffee, etc., taking turns at it, I should think they could keep her going along nicely, steadily covering a lot of ground without killing themselves, being able to quickly get both rowers working together when necessary to get over the foul current stretches.

.....Michael