R21 EC full displacement hull

[LAKERtoo]

.. was the full displacement hull used on only the first year of the 21EC before going to the modified hull ?? 2006 and 2007 EC hulls ?? ... is there much difference in top cruising speed between the hulls and if so, is there a savings or penalty in fuel consumption ?? .. TIA .. this is a very involved forum group .. great information .. Rob ( Wannabee Ranger)

 

[Stevan47]

Hi Rob: I can't answer your question as I also am relatively new to the Tug fraternity, having bought my vessel only last November. I have a question though: 'Rhapsody' is a 2010 model Tug. Does that make her hull a semi-displacement hull? Anyone out there care to enlighten me? Happy to receive lots of good advice. Kind regards to all, from 'Down Under'. Stevan

 

[SGIDAVE]

Perhaps the factory will chime in.

My understanding is the original R21 (before MY 2006) was a displacement hull. Full displacement means the hull is not meant to be driven faster than "hull" speed [as derived from the calculation: Hull Speed in KNOTS = 1.34 x square root of waterline length in feet] Therefore, in the case of the ORIGINAL R21, hull speed = 1.34 x 4.58 = 6.1 Knots.

With the advent of the R21-EC, the hull was redesigned and is now a semi-displacement hull which means its design combines both displacement and planing hull attributes. WOT speed in my 21-EC is 9.5-10 mph. I cruise at much lower speeds, however. Somewhere between 2000-2600 rpm (which yield SOG of 6-7.5 mph) are very comfortable in my boat. These are NOT 'go fast' boats. In actual practice, I doubt the normally-enjoyed cruising speeds are much different between the two hull designs (unless somewone enjoys pushing their boat at 80%+ power). Even then, my guess is the speed gain is only 1-2 mph. I believe all 21ECs are the same (no early models with displacement hulls).

I don't know when the original R-21 was released, but it was AT LEAST as early as 1987 since there is an example of that vintage listed in the Tugnuts for sale forum.

Again, accurate history from the factory will clear this up and prevent propagation of incorrect information on the interweb.

Try it, you'll like it!

Dave

 

[wefings]

As far as I know , it has always been, and still is a displacement hull . The year model 2006.5 EC model introduced lengthened the cabin and widened the stern section to carry more weight and add width .The pre 2006s had more of a "double ender" shape , like the Bristol Bay salmon trawler it was modeled after . At 9 MPH you are simply "muscling" a displacement hull over the hull speed . That's why it squats and pushes water . Some of the original boats had 18 HP and 24 HP Yanmars in them , which provided hull speed .
Marc

 

[LAKERtoo]

.. so general consensus is that all 21EC's are semi-displacement hulls unless someone knows to the contrary .. in keeping an eye on Ranger 21 and 21EC's for sale, I thought that I had come across a description on a 2006 EC for sale that was a full displacement hull but that may have been a misconception .. Rob