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

Fire Arrow Main Hull ,July 2011---the beginning. Shows the original bottom. After initial testing the bottom from mid-ship aft was changed and extended:

 

Fire Arrow, July 2014:

 

"The Great Leap....." My friend and mentor Eric Sponberg and his wife Arliss are about to leave(or have already left) the western end of the Panama Canal for the Marquesas -some 4000 miles away! Arliss is a novelist and writes a blog documenting their trip that is well worth reading: The Old Woman and the Sea – Arliss Ryan http://www.arlissryan.com/blog/

Corroboree https://www.ericwsponberg.com/boat-designs/corroboree/

 

Downforce from main foil-- Fire Arrow,WOLF, Gitana 17, Banque Pop:
I had a great e-mail from Guillaume Verdier* a short while ago in response to an e-mail I sent about whether or not downforce from the main foil would be an asset in preventing a capsize with Gitana 17 if it was in a situation similar to Banque Pop just before her capsize with the boat starting to lift(roll).
His answer was "yes" particularly if the mainfoil flap was tied into the autopilot so that the flap was moved up automatically and very quickly. Unfortunately, that is illegal in the Ultim Class for the time being. But the fact that he thought it would work was tremendous.
It might be possible to come up with a manual system that requires only pushing a button in the meantime. *Banque Pop needs to rake the whole daggerboard in order to change the angle of incidence of the mainfoil so their ability to respond might have taken longer than would Gitana because mainfoil lift is controlled with a flap.
*This is incorrect-in reading more about Banque Pop I discovered that the main foil does use a small flap.
I asked ,also, if there would be any structural issue with an instant application of max downforce and his answer was that there would be none with Gitana 17. He also pointed out that the daggerboard foil provides a great deal of roll damping.
* designer of Gitana 17-the first full size trimaran designed from scratch to use the foil system pioneered by Fire Arrow. Also designer of the foil system on Maserati.
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UPDATE From Guillaume Verdier 4/26/18: I wrote to Guillaume last night and sent him the picture below(originally posted yesterday by Corley). I asked for his thoughts .He was of the opinion that the loss of the mainfoil "may well have caused the capsize" of Banque Pop.
UPDATE #2 From Guillaume : he was told that the horizontal mainfoil was removed for towing after the capsize.
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Fire Arrow and WOLF use a wand controlled mainfoil so that any tendency to lift the main hull beyond its designed flight altitude would result in the instant application of downforce resulting in a substantial increase in righting moment-in other words: instant gust response.

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Banque Pop minus her main foil:

 

Interesting comment by Tom Speer regarding riblets:
Henry Bilinsky - Inventor of Drag Reducing "Shark Skin" https://www.boatdesign.net/threads/henry-bilinsky-inventor-of-drag-reducing-shark-skin.60116/#post-828856 post#8

"FWIW, besides Stars and Stripes in 1987, riblets were also used on the amas of USA 17 in 2010. The latter had finer grooves because of the higher speed of the trimaran."

 

Mainfoil Wand Based Electronic Ama Foil Incidence Control: The Fire Arrow Foil System uses a wand controlled main foil where the wand increases lift for takeoff and reduces mainfoil lift as the boat speeds up automatically converting to downforce as necessary. But the ama foils are twisted to help them takeoff when the mainfoil does. This can be draggy particularly as the boat speeds up.
With the electronics available today it may be possible to use a signal originating from the mainfoil wand to move an actuator that would change the AOI of the ama foils eliminating the need for twisting them. This could be a pretty simple system I would think and be a major drag reducer at moderate and high speeds while still allowing low wind speed takeoff.

 

Fire Arrow System Advantages:
This is a document I put together for a friend to help her understand the boat a bit better. I sent pictures separately after having trouble adding them to the document......

 

Downforce from main foil-- Fire Arrow,WOLF, Gitana 17, Banque Pop:
I wrote to Vincent Prevost of VPLP about the Banque Pop capsize and he sent me a very detailed answer. One startling thing he said was that as far as he knew, Banque Pop lost their daggerboard foil the day before the capsize.
Check it out below for more informative and interesting comments from the designer of only the second ULTIM tri to use the equivalent of the basic Fire Arrow Foil System.
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Here is a most gracious, detailed response from Vincent Prevost. (Thanks again for the suggestion, Dolfiman!).
First, my question:
Hi, I’m very interested in the foil systems being used by Banque Populaire and Gitana-particularly the main foil on the daggerboard. I saw a picture yesterday of BP upside down and noticed there was no foil on the daggerboard-I’m curious: was it removed due to damage or just to get it out of the way? Was it possible to use that foil to develop downforce and could it be used to prevent or slow down a capsize ? If the Ultim rules were changed could the flap be tied in to the autopilot in such a way that at the very beginning of a capsize the flap was moved max up to generate maximum downforce? Would there be any structural issues with this?

Thank you for considering my questions-I greatly appreciate it!

Take Care, Doug Lord

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Vincent's response:
---
Hello Doug
thanks for your email relative to BP capsize
As far as I know, they had lost the T of the board a day before.(bold emphasis dl)
Considering the T board may push up or down for about 2.5 to 3 tons , the RM can be increased or decreased by 15 to 20% which is a lot in terms of overlaoding the platform and mast.
In ocean racing world, we enter in a new era where , as for the Foiling Imoca 60, the righting moment of the boat is function of the dynamic forces generated by the foils
It means that the skipper will have to sail taking into account these variations of RM caused by dynamics loads from the foils if he doesn't want to break the boat
sensors , alarms have to be installed now to have the knowledge of the loads on the elements of structure impacted by RM variations
So in theory ,for your last question, answer is yes to delay a capsize with 2 warnings:
- increase the RM affects the designed structure of the boat , and ,
- at the heel angle where the board is out the water, you brutally loose 20% of your righting moment
So to be used being seriously informed and controlled (bold emphasis dl)

hope that helps
regards
vincent

 

littleWOLF
In my struggle to try and find a viable way to build(or have built) some version of the Fire Arrow concept full size for my own personal boat I originally settled on the 15.5' X 18.75'(wide) WOLF. That has turned out to be a pretty expensive way to go. The best part of WOLF other than the Fire Arrow Foil System(with its ability to foil in light air) was the extreme comfort and the ability to take two people out for a ride at near top performance,upwind and down.
I've been tossing around the idea of a version of WOLF/Fire Arrow that would be much smaller .Here are the tentative specs of what would be basically a big model: just a little over twice the length of the Fire Arrow Test Model.
littleWOLF specs(tentative) :
LOA 13.8' / ama LOA 8'
Beam 14'
Target weight 150-180lb
SA-
--upwind: 149 sq.ft
--downwind: 249 sq.ft
--max pressure before depowering/reefing: 1.58lb/sq.ft*
* NOTE-see following post for max pressure comparison with an F18.
Cost about 56% of WOLF
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Advantages /disadvantages:
1- ama/curved piece/ crossarms will be a single structure that can simply be pivoted for trailering.
2-slight disadvantage of this arrangement is an ama that is proportionately shorter than on WOLF/Fire Arrow.
3-much easier to handle on the beach.
4-will not have the capability of taking two people for a ride with high performance upwind and downwind. Downwind will foil with a crew weight around 340lb in 6.5-7.5 knots of wind.
5-Singlehanded (200lb crew) will foil in 5 knots of wind .
6-Carbon rotating wing mast.
7-Retractable foils(from cockpit).
8-Extremely comfortable.

littleWOLF would look very much like this but with shorter amas
and raked aft forward cross:

 

Fire Arrow Foil System: Automatic Mainfoil Control
Vincent Prevost's comment* in post 2693 is interesting and surely an important consideration.
*"at the heel angle where the board is out the water, you brutally loose 20% of your righting moment."
Early in the design of Fire Arrow that was very much on my mind hence the relatively deep daggerboard. On Fire Arrow, the boat is designed to sail at a 10 degree angle of heel in order to keep the windward ama foil clear of the water without the crew having to raise or lower it after a tack or gybe.
In addition, the boat was designed from scratch to be able to effectively utilize mainfoil downforce. The purpose of the wand controlled mainfoil is to lift the mainhull early -before it would lift due to wind pressure on the rig. Since the mainfoil is relied upon to do that, I was able to increase beam so that the platform is oversquare. On a "normal" tri an oversquare beam can be problematic because the RM is then so great that it takes a relatively strong wind to fly the main hull. But with the wand controlled mainfoil the main hull lifts in very light air-about 5mph.
The oversquare beam helps the mainfoil downforce to work more efficiently due to the distance between the mainfoil and ama foil. And the downforce from the mainfoil can substantially increase righting moment. The automatic wand control of the mainfoil flap can allow almost instantaneous gust response.
The fact that the functioning of the mainfoil is essential to the performance of the Fire Arrow from the lightest air to the strongest wind means that it is mandatory that the mainfoil is low enough not to be at risk of "popping out" at any time. The extra depth can add a bit of drag but the increase in power to carry sail due to the oversquare platform(made practical by the wand controlled mainfoil) is a huge performance gain for the boat and completely offsets any additional drag due to the deep daggerboard-in light or heavy air.
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If the big boats could use some sort of electronic system that would fly the mainfoil like the wand does on Fire Arrow, it might be possible to increase beam/daggerboard depth to take advantage of the characteristics of an automatically controlled main foil. At this point in time, automatic electronic foil control is illegal in the ULTIM class and a wand probably impractical. The biggest boat,so far, to use wands to develop lift and righting moment was Dr. Bradfields 40' SKAT.
I believe a Formula 40 tri could use a wand controlled mainfoil almost identical to the Fire Arrow System.

Banque Pop's main foil "popping out"-note daggerboard may have been intentionally up but nevertheless it shows how the foil can come "loose" intentionally or not-see one minute eight seconds in:


Fire Arrow deep daggerboard:



Dr. Bradfields 40' SKAT- the mainfoils developed most of the RM for the boat:

 

Cormorant on the dock this morning-just beautiful:

 

littleWOLF--max upwind pressure compared with an F18:
A C2 F18 by Greg Goodall has a maximum upwind pressure before depowering of 1.38lb./sq.ft.. Thats with two 180lb guys on trapezes. The littleWOLF max pressure occurs with the boat on foils and the crew sitting comfortably to the windward side of the cockpit!
littleWOLF has a max upwind pressure* of 1.58lb/sq.ft. with the single 200lb crew sitting very comfortably to the windward side of the cockpit. No having to run 8' side to side with every tack or gybe! This is one of the biggest advantages of the Fire Arrow Foil System coupled with the unique oversquare platform design. The system not only allows a high maximum pressure but allows very light air takeoff allowing extremely comfortable foiling in the whole windrange from 5 knots to 20+ knots. There is no current foiling multihull under 20' that can do this while matching the comfort that is intrinsic to the Fire Arrow** configuration.
*Downforce from the main foil can increase power to carry sail-and result in increased pressure on the sails. Further, the wand controlled main foil provides almost instantaneous gust response-increasing RM as needed.
** or WOLF or littleWOLF!
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>see post 2694 above.....

 

The story of "3D SAILING"--- A few years ago as I became more excited by foiling and its future and while I was building the first RC production sailing foiler ever, I came up with the idea for a trademark that I felt was a "high tech" description of foiling-"3D SAILING". My patent attorney filed for it and all seemed well until we both received a letter from representatives of North Sails who had been using the trademark "3D SAILS". Well, both marks were completely different in what they represented and North lost.That was very cool.
Next in the saga of 3D SAILING was a letter from a lawyer in Beverly Hills, California offering me $1000 for the mark. I said no way but they didn't give up. Over about a two week period we haggled back and forth and finally I made an offer: I would sell it for $8,000. I didn't think there was a chance of them accepting but boy was I surprised when they did! It took some time but I finally found out that the Company that bought 3D SAILING was a giant Canadian boat builder-mostly powerboats. So as time went by I'd check on their product line expecting to see a new foiler.
Years went by and no foiler from Bombardier.
So a while ago I looked up the mark and it was expired! Unbelievably, they had done nothing with it and paid 8 grand for the privilege of doing that.
So I asked my patent attorney if there was any reason I couldn't use the mark though I realized that I wouldn't have exclusive rights to it. He said to go ahead. I still think it is a great description of foiling and well worth using.

3D SAILING:

 

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I've looked again at this concept as it would be applied to the littleWOLF(see post 2694 above). The boat's overall beam with foils retracted would be 8', with foils deployed a bit over 16'. This time I looked closely at righting moment. The version of the boat with a 14' beam and UptiP ama foils would have the same RM as the version with Welbourn foils. Though the overall beam is more with the Welbourn foils , they can be retracted making the whole package trailerable with no more effort than retracting the foils.
The systems would otherwise be identical-same rig, same wand controlled daggerboard lifting foil , same relatively small amas.
The main difference is that the Welbourn foils don't develop lateral resistance whereas the UptiP foils do

 

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Same max RM but the narrow platform* version has poor response to a 10 knot gust while not moving-- rolling too much. This would make it a handful in gusty conditions with moderate waves especially when tacking.
*narrow version has a platform beam of 8' but an overall beam of 16' with Welbourn foils extended each side.