Saturday, July 12, 2008

Sport Boat Foilers

With the phenominal new Super Foiler Mirabaud making history NOW it seems like a good time to revisit these ideas I've thought about and worked on for several years:

There are some really exciting sportboats available now and at the end of this post are some interesting websites particularly the one with comparison statistics of a few current boats. For purposes of this post I'll define sportboats as high powered keelboats between about 20' and 40'. Some boats are much higher powered than others as you'll see in the comparison table. They should be able to plane (or foil). Ocean racing versions should be self-righting.
After doing an exploration of the feasibility of a foiling 60' monohull keelboat, it occurred to me that the next big advance in monohull foiling would probably be with a boat that fits the definition of sportboat so I 'm presenting very preliminary numbers for a two person and three person "Sportboat Foiler":
Two Person
---LOA 24'
---LWL 24'
---Beam 18.6' (overall, incl. racks)
2.4' at waterline
---Draft 6.5' keel,foils retractable
---Sail Area 586sq.ft. upwind and downwind
---Boat weight,incl. rig and ballast-1100lb.
---Ballast 490lb. (110° canting keel) 44% ballast/displacement ratio w/o crew
---Displacement (incl crew)-1420lb.
Three Person:---LOA 24'

---LWL 24'
---Beam 10.73' (overall incl. racks)
2.4' at waterline
---Draft 6.5' keel and foils retractable
---Sail Area-600 sq.ft. upwind and downwind
--- Boat weight- including rig and ballast-1100lb
--- Ballast 490lb.( 110° canting keel) 44% ballast/Displacement ratio w/o crew
---Displacement, incl. crew 1580

---LWL 24'
---Beam 18' (overall incl. racks)(2 on trapeze optional)
2.4' at waterline
---Draft 6.5' keel and foils retractable
---Sail Area-650 sq.ft. upwind and downwind(except in light air then 1200 downwind)
--- Boat weight- including rig and ballast-1100lb --- Ballast 490lb. 44% ballast/Displacement
ratio w/o crew
---Displacement, incl. crew 1580
Take Off Boat Speed is 6.5 knots which would be achieved in a 6-7 knot wind with 650sq.ft SA
Configured for early take off using a 63412 section at a mainfoil angle of attack of 6 degrees and a 20 degree mainfoil down flap angle.


Other comparisons:
-- -Sail Loading(weight divided by SA)- Two Person=2.42 lb. sq. ft. ; Three Person= 2.69 lb. sq.ft.; Three FIXED 2.43(#2 & #3 this ratio better than a MOTH)
---Mainfoil Area- Two Person=7.1 sq.ft. ; Three
Person= 7.48 sq.ft., Three Fixed 7.64 sq.ft
---Mainfoil Loading- Two Person=158lb. per sq.ft.
Three Person=169 lb. per sq.ft.
---Sail area per sq.ft. mainfoil area- Two Person =82.5 ; Three Person=80.2 ; Three Fixed=86.8
Note: Two person takeoff profile is approximately equal to a Moth with Rohan Veal aboard;
Three Person approx. equal to a Moth with a 160lb. person aboard.
---D/L Two=45.6 Three= 51
---SA/D Two= 74.3 Three=70.9 Three Fixed=78.4
---SCP/total weight Two=42% Three=34% Three FIXED 38%
Three person fixed keel would be 100% selfrighting w/o crew interaction:BALLAST/DISPL. RATIO SIGNIFICANTLY BETTER THAN T780. Ballast in this keel is not used for sailing RM-just for RIGHTING. Boat sails with 20 degrees veal heel adding 21 % to RM.
Both canting keel boats would be designed to be rightable by moving the keel; and a 100% self-righting foiler(no crew action required) is possible------------------
Weights for the hull and rig were derived from EXISTING boats that have hulls ,for the most part, twice as wide with over double the area anticipated with these boats. The hull would be very narrow -not much over three feet wide(at the deck) with possible flare out forward for a minimal cuddy cabin. The hull would be double-ended. In comparisons with the other boats in the table below the Sail area to wetted surface ratio of both versions above is probably greater than any other boat even INCLUDING the wetted area of the hydrofoils.(8.27/1 vs. 4.7/1 for the Martin 243).

I did this to show how incredibly close we are to having one of these boats actually built; the technology required to do this is available now and I hope it won't be long before "Flying Keelboat" really means flying...