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

D4Z / Batfoil Testing

The D4Z Batfoils have been modified:
1) Inboard iFlap removed,
2) Outboard iFlap reduced from 50% tip area to 30%.
The foils are still twisted 3 degrees from zero at center to +3 degrees at the tip(washin instead of washout). Flaps remain at down 15 degrees.
The foils are set up on the boat to have an angle of incidence at the center of +3 degrees to +6 degrees at the tip.
The idea is that they will develop high lift at low speed and low drag at high speed. The mods have been germinating for months but observation of the boat underway in very light air at displacement speeds helped to finalize the decision to reduce low speed drag.

 

Makes sense sort of, in a DL sort of way, now get out and start testing before making any more mods, you might just have gone one step to far and you will never have known whether it was a good mod or bad.

 

D4Z / Batfoil Testing and Development

Interesting. When I went from the low area ama foils to the larger foils after the second test sail of the Fire Arrow, I skipped a step and that was testing the increased area foil before adding the 15 degree fixed iFlap. The larger foils worked well with the flaps and the boat flew but this next time out I have removed the iFlap from the port ama foil so that the two ama foils have the same exact area but only the stb foil has the flap.
Fixing the D4Z foils was important as I had begun to understand the extra drag caused by the inboard flap at takeoff with the boat level or nearly level. The foils are very easy to change........

Left, the updated foil, center-the original foil, right- iFlap(15 degrees down) view from bottom of foil:

 

Testing and video-Fire Arrow and D4Z

Dan is not available any more this year because of his football schedule. So I need a "crew" to help with the boats and to take video with my camera. Needs to be free in early mornings during the week-not on weekends-starting when it gets a bit cooler.
So if you're local and interested in working for free to help develop one of a kind test models please let me know.

Fire Arrow at the moment of takeoff:

 

Doug,

How can you ever hope to get any usefull information if you keep changing things even before they have proved or disproved their intent. From where I'm sitting you are either a fool or a genius. And at this stage I'm not sure you are the latter.

For someone who professes to be the "God" of all things foiley there sure isn't any science that I can see in your testing to date.

Bas

ps Just to prove me wrong why did you reduce the foil area prior to getting the thing foiling? I know you've given the reason why, but that sure sounds like a half cocked reason to me? Would you like to give a scientific reason why.

 

====================
Basil, it was obvious, in the low speed runs, that the iFlaps were generating too much drag by studying the wave formation around the boat.
Also, since the foils are canted outboard at the bottom 10 degrees AND I use the Trapeze Power Ballast System to keep the boat close to level, it was obvious that I screwed up having symmetrical iFlaps on these foils. As the thing begins to take off, it became clear to me that the inboard iFlap would cause a great deal of drag just when the boat needs to accelerate.
Those two factors resulted in a reduction of the size of the outboard iFlap and elimination of the inboard iFlap.
Any time the boat sails it's possible to learn something- especially with 25+ years experience in testing foils!
Most rc sailboats have multiple rigs because it's impossible to sail efficiently with the same rig you use in a 5mph breeze in a 10mph breeze. The big rig on this boat can't be used in over around 5mph of wind because once on foils the boat will sail at twice windspeed or more making the apparent wind over the limit for the big rig.
So the rig was cut down to the size of the first reef(designed into the rig) rather than roll the reef into the sail each time. The jib was left untouched so SA was reduced around 19% and the CE lowered about a foot. This will allow testing in a broader range of wind than possible with the big rig.

 

Quote Doug Lord,

The idea is that they will develop high lift at low speed and low drag at high speed. The mods have been germinating for months but observation of the boat underway in very light air at displacement speeds helped to finalize the decision to reduce low speed drag.

Hi Doug,

New to forum and though I would start by saying I love your foil design concept, but not necessarily the actual design of the bat foil.

I have been doing foil calcs for over 12 months now on a tri project I have in my minds eye, I have looked at just about every design from the day dot through to now.

Your statement while seemingly simplistic is dead on the money.

High lift at low speed can be achieved via:

1. Large foil area.
or
2. High AOA. (Angle of Attack).

But this also leads to high drag.

Low drag at high speed:

1. Small Foil area.
and / or
2. Low AOA.

But depending on the foil design can vent and cavitate and hence loose lift and come crashing down with current foil designs.

In the current foiling mindset everyone is looking for a single element, or combinations that can do it all, be it an L, J, C, T or adjustable AOA system.

Everyone seems to be copying the current style of large cats.

My contact and post is to see if you would be interested in discussion, either here or privately regarding a different way of looking at solving the problem without the need for all the fancy trimmings?

Essentially it looks like you have elements of it in your bat wing design but have not entirely twigged on what it is that is happening.

Not saying I have the final or best concept just need to discuss with someone who has a very sound appreciation of foiling and overall boat design and dynamics.

Essentially in theory the design is self regulating - Lifting force and drag are self regulating in the foil design.

I am currently trying to build a scale model of the idea for proof of concept but am limited with time and ability to achieve this.

Would appreciate any advice or comments.

Thanks,

Hydroman

 

Fire Arrow Foiling System Testing and Development

Welcome to the forum, Hydroman! You might do better to start a thread in this forum-still here at boatdesign.net : http://www.boatdesign.net/forums/hydrodynamics-aerodynamics/
I'd be glad to discuss your ideas here, in the Hydrodynamics forum or by e-mail -your choice.
The most important thing about the Batfoils is that they are surface piercing T-foils where altitude is regulated by speed( no wands required). The iFlap is an attempt to improve low speed takeoff where the flap drag is eliminated as the foil speeds up and the flap comes out of the water. The Batfoil is primarily directed at allowing a simple hydrofoil for RC model cats and as a possible replacement for the wand controlled main foil on the Fire Arrow. There would be problems with its use on a full size boat: 3 surface piercings per main foil and a possible propensity to ventilate(not a problem at RC model size). These may or may not be able to be overcome.

PS-just noticed where you are from-you should try to see and talk to John Ilett of Fastacraft-the father of the production foiling Moth who adapted Dr. Sam Bradfields wand system to the Moth. He might be real helpful.

 

Bat Foil

Hi Doug,

Thanks for the reply.

Have spoken to John briefly once, he is very focused on moth development and seemed not completely open to discussion on other hull concepts. The thing is the moth design would lend itself directly as a platform from which to build my concept.

What I have in mind is a complete breakaway from current thinking on hull design, buoyancy and foil integration. My design integrates 3 modes of operation into one concept, displacement, planing, then foiling.

Your Batfoil / theory on foil performance contains elements of some of my concepts. I take this as a bit of a confirmation of my theories and logic process that I have used to develop my concept and designs.

If you work from the bottom up, that is to look at the current designs and their shortcomings then the answers are blatantly obvious.


Thanks again,

Hydromann

 

Fire Arrow Foiling System Testing and Development

==========================
Interesting, my concept does the exact same thing!(but maybe in a different way than your concept does)
1)Planing main hull but only to facilitate buoyancy forward in the event of a pitchpole-to allow righting. That happened on the second test sail(2nd video) and she recovered because of the buoyancy of the hull and deck forward.
The main hull flys before it can plane-in other words it goes from displacement mode directly to flying.
2) Planing ama but only for incidental contact when on foils. However, the smaller concept model(see pix below) was originally conceived to allow planing on the ama with foil assist-not full flying of the ama. That changed with the Fire Arrow though I still think it would be fun to plane on just the ama!
3) Main foil is wand controlled to maintain the flight altitude and angle of heel of the whole boat. It flies the main hull before it would fly due to wind pressure alone. It begins to unload immediately after takeoff and will go to zero lift and then begin to develop downforce(increasing RM) if desired.
A Batfoil may work in place of the wand controlled foil with or without downforce.
4) The ama foil is an UptiP(invented by TNZ for AC 34) foil because it is the only single foil that can maintain a more or less fixed altitude regardless of speed and load. If variable altitude is acceptable a single surface piercing foil (Batfoil or similar to Hydropteres foils) would work.
--
Look forward to hearing more about your concept!

Concept model of a 12 footer using the basic Fire Arrow System with or without an ama foil:

 

mmmm... very interesting.

Makes me feel kinda cluey seeing as I have only been sailing for 9 months.

I guess my engineering background in hydromechanics of pumps has programmed my brain over the last 35 years to understand fluid mechanics at an intuitive level.

A lot of the principles are the same when designing an impeller for a pump and working out the flow streams through the casing / volute design.

Cavitation as well as vortexing / venting for a hydrofoil, all these take place within a pump design.

Pumps aside, you are oh so close to an overall design Doug.

Without wanting to sound like a right royal upstart and suggest that I could possibly tell someone with decades of design and sailing experience how to design something can I make a suggestion?

Rather than have the overall consisting of separate elements try to look at it as a single element / overall design and structure in which all factors contribute to the overall performance. Then work backwards from that to the single elements that make up the overall.

So buoyancy and planing are not just factors of hull volumes and shapes, lift is not just a factor of foil design, righting is not just a factor of mass, displacement is only incurred at low velocity, foil tips do not ventilate due to overall foil / hull / alternative to hulls designs. Heeling has a righting force contributed not just by mass but also velocity....... etc etc.

Fire Arrow is a work of art, your skills are obvious and knowledge is apparent. One thing I have noticed in my modelling so far is that although the model can give me a demonstration of the design and how it works it can not replace the tactile, hands on feed back that full scale design can give you. I am finding that the model is a useful tool in refinement to the final design but then when I rethink engaging with a final design I find shortcomings to the model.

I think it will take a while before we can design out the human interface

Probably something to do with having the greatest computers every designed residing in our heads. Although technology is amazing it will be quite some time before we develop control, feedback and analysis programs that can come close.

How do I contact you via email?

Thanks

Hydromann

 

Yes a little bit and a lot at the same time.

1)Planing main hull but only to facilitate buoyancy forward in the event of a pitchpole-to allow righting. That happened on the second test sail(2nd video) and she recovered because of the buoyancy of the hull and deck forward.

What if you didn't need to rely just on buoyancy to counteract forward pitching moment? What if the overall design contributed to the stability so that it could not pitch forward?

The main hull flys before it can plane-in other words it goes from displacement mode directly to flying.

Yes and no, I dare say that there is a very small planing transition window from hull borne to foil riding. Almost indescribable but still their, your main hull design lends itself to this with the piercing bow rolling out to a flatter stern. Also as per point 2 below the ama have planing bows built in.

2) Planing ama but only for incidental contact when on foils. However, the smaller concept model(see pix below) was originally conceived to allow planing on the ama with foil assist-not full flying of the ama. That changed with the Fire Arrow though I still think it would be fun to plane on just the ama!

Agreed, the main hull and amas are an awsome design. Only issue I would foresee in this is that with any heeling the supports and ama could kick up a lot of spray and induce drag. Have you considered a wishbone shape?

3) Main foil is wand controlled to maintain the flight altitude and angle of heel of the whole boat. It flies the main hull before it would fly due to wind pressure alone. It begins to unload immediately after takeoff and will go to zero lift and then begin to develop downforce(increasing RM) if desired.
A Batfoil may work in place of the wand controlled foil with or without downforce.

Complex mechanics and physics going on here. Or should I say a complex relationship between man made mechanical components and the physics of the elements with which they are engaging in.

Having said that it is also quite simple but being made complex in peoples minds due to the nature in which the technology is being presented in todays sailing.

In reality dear old Mr Bell and others did not have all the fancy building techniques and materials that we have, nor did they have the computers and programs to layout the latest CAD designs with FEA and flow simulation yet they manages to make a ladder foil system work extremely well based on intuition.

One thing that is being overlooked in modern foil design is what the pioneers found and understood in ladder design and V foils was STABILITY.

4) The ama foil is an UptiP(invented by TNZ for AC 34) foil because it is the only single foil that can maintain a more or less fixed altitude regardless of speed and load. If variable altitude is acceptable a single surface piercing foil (Batfoil or similar to Hydropteres foils) would work.

I have seen the videos of the Gunboat G4 with this design, while impressive she's riding on a hair trigger. Watch closely and you can see she is hunting all over the place, rising, falling, weaving, diving etc. Whilst impressive in what they achieve with 2 or 3 points of engagement it is not a realistic design for the average sailor. All the crew on board the G4 are riding on one side with the ropes in hand and ready to let go if she goes awol. They then splice in a scene that shows a relaxed image of the deck with a bottle of wine, straight after which we go to overhead at full tilt. A lot of marketing propaganda in that one ;-)

But back to the UpTip (another marketing trick). Apart from being made from carbon fibre it does not do much more than a 100 year old V foil design.

This is where foiling has turned into a marketing contrived science which in my old book of engineering is rot.

The central concept of foiling is actually very basic and logical, what is more complex is the execution and application of the concept and understanding the limits of each design.

It has to do not only with lift but also buoyancy and varying loads in a dynamic system.

While the current top end racers and boats like the G4 as well as a raft of smaller cat designs with foiling systems are in the market they are very costly for an average sailor.

My concept will allow the average sailor with limited budget and skills to transform what was once an old catamaran or moth into a very stable high speed excitement machine.

I am currently building my first full scale based around an $1800.00 14 foot catamaran. It does not need expensive moulds or carbon fibre this that and the other but employs traditional wood and metal working skills that will allow an average person to build a foiling craft that will easily compete with any other.

All up I estimate the build will cost in the order of $3k to $4k which is around $20k cheaper than current offerings in the market.

It will also see a lot of old cats and tri's butchered or built into beach-able foiling fun for the whole family and not just elite top end competition.

From my perspective of just having taken up sailing nearly a year ago people are put off from trying due to entry costs. I would love to see that change from the ground up.


Again thanks for your time and comments.

Hydromann

 

Fire Arrow Foiling System Testing and Development

Hydromann, I'd say you were mostly wrong about UptiP(my spelling) foils. I spell it that way as a sort of tribute to Team NZ and to counter the absurd alphabet sea of other names some people call those foils.There are big differences between some uptip foils and "V" foils-the number one is that "V" foils are surface piercing foils whose ride height varies with speed. There are numerous designs for uptip foils-some have more heave stability than others-the differences were highlighted in the 2013 Little America's Cup between Groupama and Hydros. Groupama used uptip foils with more "up" to the tip and had much greater heave stability. Hydros required much more crew effort to control ride height and even though she was sometimes faster than Groupama she lost due to the reduced crew workload on Groupama. The UptiP foils on the Fire Arrow have worked real well since the first foiling video and they don't require any adjustment while sailing-so far.
---
When the Fire Arrow pitchpoled and recovered it was in wind conditions that were too strong for the big rig and I tried to gybe while the boat was in displacement mode. Strictly skipper error though it did show that she would recover. There were problems with the foil system on that 2nd test sail but had she been on foils the pitchpole wannabe might not have happened.
---
Looking forward to hearing more about your concept.

e-mail--- click on my name above and on "send e-mail....".

 

New Mini40 with wand controlled foils

Here is my new boat

















Its a new Mini40 designed and built by Dave Burke and myself. The hulls are somewhere between a Nightmare and a Shinobi in shape, whilst the wing cross-beam was just an experiment, as much because Dave wanted the challenge of building one as anything else but you will not be surprised to learn that the boat is about 500gms too heavy. Very difficult to beat 2 x 16mm tubes for lightweight cross beams! The main purpose of the boat is to experiment with wand-controlled T foils on the floats - and on our first outing today it flew, albeit briefly, and only on port tack. But at least it got airborne! Not sure that the negative lift form the windward T foil was having any affect on the boat, the crash-landings being evidence of this. Unfortunately the self tensioning drum exploded just as we were about to risk the number 1 rig and have some real fun. We then switched to the Nightmare, and cracked a foil - should have stuck with #2 rigs. Such is life....

https://www.youtube.com/watch?v=c0n4sY11ERU

https://www.youtube.com/watch?v=c0n4sY11ERU

Need to do some careful measuring tonight to see what the differences are in the port and starboard foils.

 

Now your talking, I love the acceleration about 55 seconds into the video when she gets up on foils!