D/L has everything to do with the weight of the boat.
Don't kid yourself. That Sundeer is way overweight. Look at how it's dragging its transom. Do you think it was designed to ride like that?
From Steve Dashew's "Cruising Encyclopedia"
"Because of our low D/L ratios,stern waves are quite small in magnitude and quickly move aft of the hull itself once the vessel in question has attained a relatively modest forward velocity.
As a result, we design some of our hulls to have a small amount of immersed transom at rest and at low speeds (typically below S/L ratios of one).
Practical experience has shown that this immersion costs us between 4% of speed at S/L ratios of .4 to .6 andhalf of this between an S/L ratio of .6 and .8.
While this is a huge number in racing terms, it seems nearly meaningless in a cruising context.
If we are talking about 4% or 4 knots , it is less than 4 miles in a 24 hour passage.
And when you look at the advantages (better performance at top speed, more efficient powering, much better prop characteristics when powering into head seas, higher longitudinal stability) this seems like a small price to pay, especially in light of the fact that with an efficient powering set-up, you are going to be motorsailing on passages during light airs anyway - regardless of how fast the boat sails in these conditions."
The book also has a series of pictures showing the stern wave still attached to the transom at S/L ratios under 1 and astern of the transom at S/L ratios of 1.125 while heavily loaded in a true wind speed of 10 knots.
So according to Steve it is designed to immerse the transom at rest and at slower speeds for gains at higher speeds of 25 to 40 miles per day.
His designs have been focused on one thing - offshore cruising with couples in mind. They have done this quite well I think. On his blog there is a chart showing his designs and their mileage. 32 boats, 21 circumnavigations (including the one I pictured) and an average mileage per boat of over 55,000 miles. They seem to do well what they are designed for.
SetSail» Blog Archive » Deerfoot and Sundeer History