Fine!
Ned Farinholt posts are concentrated on essential points in el-boat hull design. Perhaps now importance of large L/B ratios are better understood.
Rescue Minor can be studied here:
http://www.boat-
The narrow keel section indeed is in principle less wave drag.
But Rescue Minor hull is quite complicated = more wetted area and weight. Also this keel secton does not improve stability. Paradoxically it may degrade the stability, as shallow chines are lifting easily out of water?
Actuallu Rescue Minor was primarily designed for shallow waters use!
Not sure of this narrow keel section benefits?
redu
On 08/03/2010 11:57 PM, Ned Farinholt wrote:
Sirdarnell, Eric, Myles, redu, et al,
Thanks for the inputs. I am now convinced of the need to go to LiFePO batteries but 600 lbs busts the budget. 8 kWh of battery and a Honda EU2000 is now my thinking.
An intriguing thought, which probably shows my ignorance of hydrodynamics more than anything, is the use of a boxed keel. The recent article in Wooden Boat about the efficiency of the Atkins Rescue Minor at S/L of 2 to 3 got my attention. It would seem that L/B ( > 12) allows one to exceed Fn of .4. So if the keel carries 50-75% of the displacement, the hull will be very lightly loaded and generate very little wave drag. The surface resistance of the keel could be minimized by making it mostly semicircular cross-section. The keel would be ballasted with batteries of whatever type and the motor generator. The Honda is only 11.4 inches wide. Naturally, there would be a bilge pump in the keel and the boat would be mostly decked. The keel would be open to the inside the boat and formed with the hull. The hull above the keel could be a canoe or a light planing hull ala Atkins. So the keel acts as a high L/B displacement hull above which is a light planing hull. LOA about 25', keel about 20' displacement including batteries, motor, m/g, passengers and hull less than 1000 lb. What do you think?Thanks for you patience,Ned
On Aug 3, 2010, at 12:34 PM, Myles Twete wrote:
Eric-
That was an awesome analysis!
-Myles
>Honestly, these calcs came out more favorable than I expected, so I thought that I would share with the group.
Fair winds,
Eric
Marina del Rey, CA
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