High Performance MPX Foil/Self-righting Trimaran-The Test Model

WOLF daughter of fire arrow
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Going ahead with two changes to the design:
1) lowering the crossarm/two-stage ama assembly slightly,
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2) flattening the crossarm dihedral a small amount.
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After lots of studying I'm convinced these will result in improvements in handling of the boat while still retaining a major attribute of the design-UptiP foil clearance. The dihedral reduction and lowering of the crossarms will still allow the windward ama UptiP foil to be clear of the water when not foiling and substantially clear when foiling. This allows tacking and gybing without having to fool with the foils like has to be done when using these foils on a catamaran and on some tri's. The greatest advantage is reduced crew workload making it easier and more fun to sail especially singlehanded.

Unmodified model picture:

 

Fire Arrow Foils--








Original smaller ama UptiP foils:

 

WOLF daughter of fire arrow
Bottom view of two-stage amas and main hull:

 

Wolf -daughter of Fire Arrow-Foils:
The WOLF will use the same basic foil system as the Fire Arrow. It will have a target takeoff in a 5 knot wind at an estimated boat speed of 7 knots. On all foilers I have designed the load on the main foils at takeoff is 80% as I was taught by Dr. Sam Bradfield. However, the Fire Arrow and Wolf are different since they have a unique,dynamic foil system with dual altitude control systems. At light wind takeoff, the main foil(daggerboard foil) will have most of the load with the lee ama foil having just a small proportion of the load and the rudder foil having 20 % of the load. As the boat speeds up, the wand controlled main foil begins to unload as the main hull approaches its designed flight altitude/angle of heel and the lee ama foil begins to load up. At around 15 knots(or less) boat speed the main foil is no longer developing vertical lift(except as necessary due to pitch changes) since the main hull is nearly 100% supported by heeling force created by the wind pressure on the rig. At this point, the lee ama foil is supporting close to 80% of the total weight. If the boat is not depowered/ reefed and the wind continues to increase, the main foil will begin to develop downforce adding to the righting moment and the lee ama UptiP foil will begin to carry more of the total load approaching 100% and, as this happens, the rudder foil will reduce its lift and begin to pull down-automatically-further adding to the ama foil load. Maximum load before depowering on the lee ama UptiP foil will be about 120% of total weight and it will be designed to take about three times* this load.
* still under review.
The Fire Arrow/WOLF Foil System allows the boat to carry the full rig w/o depowering in a higher TWS(true wind speed) than almost any boat her size which coupled with her light wind takeoff and oversquare beam gives the boat great speed potential and the ability to foil throughout the usable wind range.

 

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Well, you miss a major point on the Fire Arrow/Wolf design: the boat is designed to sail at a 10 degree angle of heel in order to eliminate the requirement to raise and lower the ama UptiP foils with each tack or gybe! This is the only design that I'm familiar with that uses UptiP ama foils without having to retract/deploy them with each tack or gybe-and that is a big reduction in crew workload and a huge boost in ease of sailing. The boat is NOT designed for high top end speed-it is designed for early takeoff in light air , extreme comfort and ease of handling. The UptiP foils themselves contribute to ease of sailing with their automatic altitude control which will require little to no adjustment while on foils. The wand controlled main foil will also require little to no adjustment while flying.
Comfort, easy handling and light air flying are the main attributes of the Fire Arrow/Wolf design.

 

Last shots before lowering crossarms and reducing dihedral:
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WOLF mainfoil design considerations, Part 1 of 2:

One of the things I've been working on, on and off, is the idea of recessing the main foil in a sort of notch in the hull so the boat could be easily beached. There may be a solution with a curved foil molded to the bottom shape which would beep the notch to about 1 inch deep at the deepest. Along with this is the possibility of using a "semi-surface piercing foil" with two partial span flaps that would be wand controlled. The wand control could be turned off or on and would be most valuable in allowing the foil to take off early and generate downforce when desirable. The early takeoff wand function could potentially be built into the surface piercing portion of the foil but that needs some more thought.
Maybe a further development of this foil from my first foiler but curved :

 

WOLF mainfoil design considerations, Part 2 of 2:
Another idea to help this work would be to use some easily compressible foam with some kind of "skin" on it. The foam would be glued inside the notch built into the hull for the main foil and would help reduce drag just before takeoff. Any ideas for the right kind of foam?

 

WOLF final dihedral/ ama height compared with original:
This allows the windward ama UptiP foil to be clear of the water when the boat is flying and eliminates the need to retract/deploy the ama foils when tacking/gybing as is necessary with every other current boat using UptiP foils, greatly reducing crew workload. The advantage of automatic altitude control that UptiP foils are known for is not diminished at all-so WOLF has all the advantages and none of the major disadvantages of these remarkable foils , including easy retracting and shallow draft compared with foils like "Z" foils .

 

WOLF---daughter of fire arrow
Updated 6/12/17 specs and notes:

NOTE: I'm sure various changes will continue until(and after) the boat is launched-that's what development is all about.

WOLF Specifications:

LOA 15.458' (4.7m)
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Beam max-18.75' (5.72m)changed 3/22/17
-beam folded-8' (2.4m)
-main hull beam on deck: 2.625'(.8m)
-main hull beam at wl: 2.125'(.65m)
-main hull L/B at wl:7.27/1 (planing)
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Two Stage Ama-11.5' (3.5m) changed 3/22/17
-ama hull-7.7' (2.35m)
-ama hull beam .58' (.18m)
-ama hull L/B=13.3/1 (planing)
- curved piece-5.9' (1.8m) changed 3/22/17
- overlap- 2' (.61m)
- two stage ama canted bottom out 12 degrees.
- two stage ama buoyancy(not including crossarms)=252lb(61%)
-added 3/25/17 : Note: planing two stage ama is designed for incidental contact with the water. Not to be sailed "on" on a regular basis since foils provide vertical lift. The planing surface is used to reduce drag when the ama does make incidental water/wave contact at speed.
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Weight:updated 6/12/17
-boat-target-275lb/ MAX 299lb (135.9kg)changed 6/12/17
-crew-215lb (97.7kg)
-sailing/flying weight: target-(215+ 275)490lb. (222.7kg.)
MAX-(215+299)=514lb(233.6kg) changed 6/12/17
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Sail Area: updated 6/12/17
-main + jib= 217sq.ft(20.17sq.m)changed 6/12/17
- spin/screecher about 150 sq.ft(13.9sq.m)
-Sail Loading-MAX weight in pounds/SA in sq.ft.:
--upwind=2.37 changed 6/12/17
--downwind=1.4 changed 6/12/17
--max pressure before depowering= 1.76lb/sq.ft.
--max heeling moment=5402ft.lb.*
* not including asy/screecher
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Designed flight angle of heel: 5.5 degrees to 15 degrees. Standard 10 degrees.
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Main hull flight altitude at centerline: .5'(.15m)---2'(.61m),Standard 1.19'(.36m)
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Righting moment at target weight(not max weight) : updated 6/12/17
-crew 215 @14'= 3010ft.lb.( 4081N/m)*
-boat 275 @ 8.7'= 2392.5ft.lb.( 3243.79N/m)
TOTAL RM= 5402.5ft.lb (7324.8N/m)
Downforce from main foil(if used) approx. 1500ft.lb.(2033.7 N/m)
* N/m conversion done from online converter
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Foils:
-uptip foil in each ama, adjustable AOI and up/down(mostly retractable). Tentative AOI-3-5 degrees over twisted foil. Asymmetrical section.-- added 3/25/17
-mainfoil wand altitude control, adjustable AOI(nominal 2.5 degrees),up/down(mostly retractable). Symmetrical section.-- added 3/25/17
-rudder T-foil, adjustable AOI(nominal zero degrees),retractable.
-Note that in their smooth water configuration, the uptip foils can be left down at their flying position when the boat is pulled up on the beach! And, of course, as mentioned before these foils do not have to be raised or lowered each time the boat tacks or gybes. This is not found on any other boat using uptip foils.
The Fire Arrow Type/ WOLF uptip foils are shallow draft compared to most other types of hydrofoil. added 3/29/17
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Planing surface on lee ama hull is designed to be flat when main hull is just clear of the water(6") and that will occur at an angle of heel of 12 degrees.(Depending on foil lift-3/25/17)

 

Wolf--The Rig--
At this point I'm looking at a 7" carbon rotating wing mast about 25' long with a 160.5 sq.ft. main and a 57 sq.ft. jib and a 150 sq.ft asy/screecher downwind. The mast will be built by a nearby company from a production mold with a laminate schedule specifically designed for this boat and its great righting moment. The main will come down to just below the level of the top of the cockpit.
As mentioned previously the boat will not use a canting mast as standard but for really important races the system will be easily fitted.
The WOLF RM is about 1.7 times that of an A Cat*, upwind SA is about 1.45 times an A Cats upwind SA and downwind the WOLF has 2.4 times as much sail area.
* both sailed single handed with the same weight crew on a trapeze on the A Cat and sitting in a comfortable seat on WOLF.
The mast and rig will be represented in exact scale on the completed concept model(which is based on the Fire Arrow).

 

WOLF: Ama UptiP foil trunks:
The trunks will be flush with the outboard side of the ama which maximises RM and makes the inside surfaces of the trunk easily accessible. Problem is facilitating the curve of the vertical portion of the foil within the trunk while keeping it close to the side of the ama.

see post 2564 below:

 

Removable outboard trunk for cat/tri:

 

WOLF-daughter of fire arrow

 

Stepped planing amas: check out the new Superfoiler video showing some good shots of the ama design similar in design to the Hydroptere amas and to the concept of the Fire Arrow/WOLF planing amas. New Trimaran Foilers https://www.boatdesign.net/threads/new-trimaran-foilers.55834/page-7#post-806531 post 98
The Fire Arrow/WOLF amas are not stepped planing hulls like Hydropteres amas or the new Superfoiler amas because , in essence, the ama ends at the back end of the planing surface. But all three are designed for incidental contact with the water at speed and ,as well, the Fire Arrow/WOLF amas are designed to be relatively low drag during wave interaction and during incidental low speed immersion.
Also, the Fire Arrow/WOLF planing amas are supported by high dihedral crossarms with a curved ama "second stage" that keeps the crossarms well clear of the water even in a knockdown.
pictures by DL: