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

WOLF daughter of fire arrow- finally decided to cut the "side tanks" so that the bottom of the side extension is raised up about 6"on the fullsize boat. I'm concerned about wave impacts in choppy conditions which could slow down takeoff. It will make the cockpit sole smaller but the cockpit width will remain the same at deck level.
It will be done and finished including re-painting by tomorrow night if the weather doesn't interfere......

 

Hello Doug,

I had a look at your foiling concept "Wolf"
Your design has amazed me.

1. What strikes me is the choice to have the outer legs of the trimaran with zero buoyancy. This is an interesting design option, as it goes against conventional logic, and therefore is especially interesting, as you may have identified a flaw in conventional logic.
The buoyancy in side legs of trimarans is a blessing and a curse. Blessing as it stabilizes the vessel during floating operation and at rough seas; a curse because high waves can make the trimaran to capsize.
From the looks of it, that curse has gone, although there is not yet a guarantee for stability (but that could be added).

2. I note you use several delta wing type shapes with sharp apex angle. This is known from aerodynamic to create a strong bound vortex. For example the F18 Hornet jet fighter uses a delta wing structure ahead of the main wing to ensure lift at very high angle of attack. You seem to be using this principle; I wonder what you design objectives are. My guess is that delta wings of this type will work, provided they are fully submerged.

3. Your design bears some resemblance to the Hobie Trifoiler. Have you considered discussing this design with Greg Ketterman (the designer of the TriFoiler)?

I wish you good luck with this design, and am interested in any progress you are making.

Kind regards
High Spirit
The Netherlands

 

WOLF daughter of fire arrow- Thanks HS!
1-The amas on WOLF and Fire Arrow are "two stage amas" in that they consist of a planing ama hull with a "curved piece"-see pictures in spec sheet below. The idea is to allow a great increase in crossarm dihedral as well as to reduce the drag of the whole assembly in intermittent contact with the water at speed. At slow speed, the two stages together have substantial buoyancy- the "curved piece" and ama hull have about the same buoyancy . If you turn the boat sideways at 90 degrees you can see that the buoyancy from both stages will tend to right the boat-the high dihedral crossarms coupled with the total buoyancy from the ama hull and "curved piece" make it very hard to capsize and will right the boat from a 45 degree pitchpole. The two-stage amas together support around 90% of the total weight of the boat when fully immersed but their buoyancy is simply organized differently than a conventional tri which helps prevent a capsize and aids recovery from a pitchpole. Both boats are oversquare and these two stage amas work real well with the extra beam. Two stage amas with a much narrower beam probably wouldn't work too well.
2-The planing surface of each ama is designed to reduce drag during intermittent contact with the water at speed.The shape is not really a delta- its shape stems from the integration of the relatively flat planing surface with the "U" shaped forward sections of the ama hull.
At slow speed, both the ama hull and curved piece are designed for relatively low drag. These amas are not designed to be sailed "on"-they're designed for the lowest drag for momentary contact with the water. The forward section of each ama hull is designed to go thru waves with relatively low drag during intermittent contact. The ama hull is inspired by a stepped planing hull with a different front end and minus the rest of the hull (as on a "normal" stepped planing hull).
3- I haven't discussed this particular design with Greg but he has been a big help in foil discussions particularly with regard to the use of downforce. The Fire Arrow and WOLF both use a center mounted wand controlled foil on the daggerboard in addition to a rudder T-foil and an uptip foil* on each ama. The wand controlled main foil on the daggerboard helps the boat takeoff in very light air and develops downforce in heavier air to add to righting moment. Using the mainfoil like this was inspired by discussions I was lucky enough to have with Dr. Sam Bradfield, an American hydrofoil pioneer, who was also a great teacher. The concept of using the wand controlled mainfoil coupled with the automatic altitude control of the the uptip ama foils(one at a time) was originated on the Fire Arrow Test Model and ,more recently, has been used on several much larger tri's (see posts on previous page). It has tremendous benefits especially in making an oversquare small tri possible , increasing RM thru instantaneous downforce when required, and roll stabilization on any size trimaran.
*Uptip ama foils are used because they can be designed to control ama flight altitude virtually automatically with very little adjustment required(see post on previous page).

 

WOLF daughter of fire arrow
Latest Update 8/27/18
==================
WOLF specs(tentative) :
LOA 14.8' changed 6/2/18
Max Beam 16'changed 6/14/18
CL ama hull to CL ama hull-14' added 6/14/18
Target weight 175-190lb
SA-(mast length 24' all carbon wing mast) added 8/8/18
--upwind: 167 sq.ft changed 8/7/18
--downwind: 267 sq.ft changed 9/7/18
--max pressure before depowering/reefing: 1.79lb/sq.ft changed 8/7/18*
* NOTE-see post below- 2763- for max pressure comparison with an F18.
RM-max righting moment=4460ft.lb.. added 8/8/18

------------------------------------------------
Advantages:

1-Singlehander-will not have the capability of taking two people for a ride with high performance upwind. Downwind will foil with a crew weight around 340lb in 6.5-7.5 knots of wind. Excellent upwind performance with 220lb crew. changed 8/8/18
2- Will foil in 5 knots of wind with 220lb crew . changed 8/8/18
3-Carbon rotating wing mast, carbon cross arms and carbon foils.
4-Retractable foils(from cockpit). Mainfoil retracts flush with bottom and tips are designed to not dig into sand. Rudder foil retracts above bottom. Ama foils retract above waterline when boat is level.
5-Extremely comfortable sliding seat on each side. Allows crew to move 1.75' outboard very quickly. expanded 8/27/18
6-Uses the Fire Arrow Foil System(like Fire Arrow, Gitana 17, Banque Pop, Macif and Maserati)-- the same as the original system first used on the Test Model- except the larger boats use two rudder t-foils on each tack. WOLF has two UptiP ama foils-one used at a time-and one wand controlled mainfoil for very early takeoff and capable of substantial downforce- all working with a single rudder T-foil. Downforce can be virtually instantaneous adding RM in response to gusts. expanded 8/27/18
7-Foiling throughout the wind range -including very light air-the essence of 3D SAILING!
8- Assy Spin/Screecher retracted under the front deck. added 6/3/18
9- Boat folds from max beam to trailerable width in about 4 minutes. No waterstays. added 6/14/18
10-Mid (wish)boom mainsheet so sheet is always in forward hand and extention tiller always in aft hand. added 6/14/18
11-Quickly self-draining cockpit-large scuppers with backflow flap. added 6/14/18
12-Adjustable angle of incidence of planing surface of each ama simultaneously. Angle of incidence of ama foil has to be changed when this is done. Planing surface starts at +4 degrees. added 6/29/18
13- Uses Two-Stage Amas-see pictures below. They consist of a planing ama hull(Stage One) coupled to a "curved piece"(Stage Two) that provides extra buoyancy in the event of a knockdown. Curved piece facilitates high dihedral crossarms which keep the crossarms clear of the water. added 8/8/18
14- Aerodynamic surfaces added to forward and aft crossarms. Adjustable flaps added on rear cross each side. Jib foot and forward part of main foot to be sealed to deck. changed 8/8/18
15- Planing ama hulls designed for incidental contact with water at speed and for inadvertent contact at slow speed. added 8/8/18
-------
==================
---Memorable quote from JG Baker, Designer and Builder of the Monitor foiler in the 1950's:
" The main need is to lower the wind velocities required for flying in order to increase the opportunities for high speed travel"
added 8/8/18
================
--- Fire Arrow Foil System-first of its kind on any trimaran. Elements developed first by Fire Arrow include:
1) the first trimaran in history to use uptip ama foils,
2) the first trimaran in history to use a single wand controlled main foil capable of downforce,
3) the first trimaran in history to use Two Stage Amas.(see below for Two-Stage Ama pictures)
added 8/27/18

 

WOLF daughter of fire arrow---surgery: -see post 2776 above. The "step" in the cockpit is the result of removing the cockpit extensions on each side. All done except cosmeti-size-ing! I really didn't want to do this job with the concept model 99% done-wish I could have had the foresight to design it this way from the start. Oh, well -it's right now. Thats the purpose of the model: study,study,study and make whatever changes are required......And soon- God willing and the creek don't rise-get it built and flying!

 

Hi Doug,

Thanks for the additional explanation.
Previously I have had a thorough look at the Ketterman Trifoiler, and learned that the reason this Tri works so well is that the L shaped foils are self-stabilizing. This feature occurs because of (1) the L-shape and orientation and (2) the angle of attack is increasing / decreasing as required (this feature is due to the sensor-ski's in front). All of this is explained in Ketterman's patent (WO91/08944).

I was wondering if your design has such a self stabilizing feature (because that would increase the dynamic stability and ease-of sail considerably).
When watching youtube films of the Hobie TriFoiler, you can observe that the vehicle remains level trim at any speed or any maneuver. Specifically, it does not heel over at a wind gust, where any other sailboat would do that. This merit of the Ketterman design cannot be overstated.

Your "wolf" design also has some bending flexibility (it is not 100% rigid) and this could perhaps be exploited to create the self stabilizing feature as indicated above.

On the topic of the delta wings, apparently you have not considered this in your design. Maybe there is some merit in considering what effect this would have, in view of the potential benefits. Note that sharks and dolphins and marlins and swallows all use delta wing type leading edges for their fins/wings. So clearly Mother Nature is indicating this gives high speed (in case of the sharks, dolphins and marlins) and high agility (in case of the swallows).

Kind regards and good luck
High Spirit.

 

HS, the "L" foils on the Trifoiler are not actually self-stabilizing(like uptip foils) but the "feelers" stabilize the boat by automatically controlling the angle of incidence of the foils providing downforce as necessary and all the righting moment for the boat. Dr. Bradfields Rave, SKAT and Osprey use dual, independent, wand controlled mainfoils that provide all the RM for the boat as do the mainfoil "feelers" on Gregs Trifoiler except with nothing sticking out in front of the boat and the feelers move the entire foil whereas the wands on the Bradfield boats just move a flap attached to the foil.
By the way, Greg told me that the Hobie Trifoiler was faster than the Rave because the Rave used vertical t-foils compared to the inward pointing trifoiler main foils.
Both the Rave and Trifoiler were slow in light air -the Rave needed 8-9 knots of wind to take off and the Trifoiler around 10-12.
--
WOLF uses a combination of the leeward uptip ama foil( automatic ama altitude control) and an automatic wand controlled lifting foil(wand moves a flap) on the daggerboard that is capable of instantly increasing RM as required using downforce. Both these systems together provide 100% automatic foil control with exceptional stability. The WOLF is designed to sail at an angle of heel settable between 6 and 10 degrees. Once set , the foil system maintains that angle of heel very accurately. This allows the windward uptip ama foil to clear the water without having to retract it --which is necessary on every other boat using dual uptip foils. The crew will seldom have to make any adjustments to the foils except for retracting them when finished flying for the day. WOLF will foil in much lighter air than either the Trifoiler or Dr. Bradfields boats which is important.
---
You say that WOLF has "some bending flexibility"--I don't think so because of the large carbon crossarms. I would say that it will be at least as stiff as the Hobie Trifoiler and/or Rave/Osprey. Stiffness and the lack of "bending flexibility" is a critical element in foiler design.
--
PS-Welcome to the forum!

Fire Arrow/WOLF type uptip ama foil with automatic altitude control-no moving parts:


Rave planing wand:


18'LOA, 22' beam Osprey with dual, independent wand controlled main foils:



16' Rave with dual, independent wand controlled foils:

 

Gitana 17 and Macif-both using foil systems nearly identical to the basic Fire Arrow Foil System:

Gitana 17:



Macif:

 

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Introducing WOLFMAN--- This guy is only 5'4" tall at the same scale as the boat but he is easy to get along with........

==========================

 

WOLF daughter of fire arrow ------- The Man has found a new place to sit-but the most comfortable and best way to fly WOLF is from one of the two sliding seats: (WOLF specs near top of page-post 2779)

 

WOLF daughter of fire arrow--- See page 180 for comments from the designers of Gitana and Banque Pop on downforce from the main foil.
Posts 2689 and 2693.

WOLF foils:

 

Ultim Video : I've gathered some video from the three Ultims that are using foil systems similar to the Fire Arrow Foil System pioneered in 2014 on the Fire Arrow Test Model here: posts 13 and 14 in the Route du Rhum thread
Route du Rhum https://www.boatdesign.net/threads/route-du-rhum.60273/#post-839284
The idea is to facilitate studying the flight altitude of all three boats.
One of the most exciting is the newest one from Macif with Jimmy Spithill-the top of the two Macif videos at the bottom of post 13.

Macif:

 

Wolf daughter of fire arrow I'm making a change to the ama Foils on WOLF which will result in a bit less span while moving the center of lift outboard about 6". The foils will be more like the Fire Arrow ama foils. Compare to current WOLF ama foils in the picture above.

Fire Arrow stb ama foil:

 

WOLF daughter of fire Arrow A shot of the new, shorter, side extensions* and the Man illustrates the sizes of the foils:
* see post 2780 above for the beginning and middle of this mod

 

So now we have the addition of the tiny toy man in many, many positions all over and surrounding the toy. Perhaps maybe you could halt this playing on your bedroom floor .... build a real boat. Did I say perhaps? Pigs fly?