Viper lifting foils

http://catsailingnews.blogspot.com.au/2012/02/ac45s-ahpc-airborne-lfoils.html

Interesting. Allowed in the rules or not?

Still not lifting the boat out like a moth. But they say 25 knots in 20 knots of breeze. But are they sustaining those types of speeds for long periods of time or just spikes?

My standard Viper gets 10 sec averages over 20 kts so maybe it can.

I heard a rumour that these things will fit the old boats as well. You dont need to lift outof the water like a moth when you have as much power as an F16.

I wonder if there will be any more surprises before the trials.

And the next big new thing will be T foils on rudders to maintain the front foils AOA, making the boat feel like an 18fter.

Followed by variable AOA on the front so it doesn't hobby horse downwind. Can't imagine hobby horsing downwind is fast, but looks good for about 20secs.

I imagine a standard curved foil will stay in place just fine but what about these?
Are they locked or lashed in place somehow?

F16 Rule 1.6.4 says its prohibited...

It's not the shoal draft option?

OK...so how did they get the L boards down into the hulls? Can they be slid up from underneath?

Hobie figured out how to 'foil' a long time ago, yet it never really caught on as a racing class.

Can any of you older guys who were active 'back in the day' of the Hobie Tri Foiler shed some light on some of the issues? I remember seeing a fleet of them, once, at the Wildcat regatta, but they looked like a real pita to put in the water, and weeds on the foils were always a problem.

http://www.youtube.com/watch?v=zXSgZCDVWOM

Stick with it, at about 2:37 it shows some of the design concept and the L foils, and how the ski at the front adjusts the up/down lift. It also shows Russel Long going 43 knots in his "Long Shot" during a speed run in France, in the ditch and a two up regular version going 35knots at the end. But I notice all the video speed shots are done with good wind...on FLAT WATER. Great for a lake.

I'd love to have one here on my lake, but I'm not convinced a 'lifting' foil, if C boards or L boards, is going to be fast on lumpy water, in the kind of racing we do in the ocean or lage bay. All that porpoising up and down can't be fast. You may get a small burst of speed when you come up, but when you nose dive back down, it could get ugly. They'd have to come up with a device to controld the AOA to yeild a steady ride over rough seas.

Anyone know where Gregg Ketterman is today? I wonder what he's up to, design wise.

I'm sure you will see these at the Olympic trials.

Timbo,
Thats probably want they did, guessing here, but that isn't allowed in the F16 rules either. You have to be able to lift the board up out of the well. Again, F16 rule.

Mike

Would a board with a hinged tip be illegal? If you made the tip asymetric with a hing it could be pulled up the well and the shape would push the tip to the correct possition when under speed.

Yes, that is illegal. According to F16 rules: "End fences/horizontal appendages below the waterline will not be allowed."

In my opinion not allowed under current F16 rules:






I dont see any interpretation that will allow for this on daggerboards. On rudders I read this in such a way that fences are allowed (like used on the Stealth).

Will be interesting to see if they send a boat with these daggers to the olympic trials. I dont know about any substantial two boat testing with this technology where the results are public.

I think it's safe to say that the f16 rules weren't a consideration when coming up with this new development. The Olympic trials are the aim.

As for the foils I had a conversation with Greg about curved foils and the like. He said that someone has done some serious work for them on this topic, and the conclusion was curved foils are quite draggy, and that straight assymetric boards is where the effort should be directed.

Oracle are also testing the same thing. I think we can draw our own conclusions from this.

WHAT IF....

Put the dagger slot in the hull at a 45 degree angle, so you'd have a long, straight dagger board, but on a 45 degree angle, which would provide some amount of lift, perhaps even more than a C board...yes? And you'd be within the rules, yes?

Has that been tried yet?

seven degrees max angle on boards

Ahh...well, we could change the rules. I think I'd rather have straight boards at a 45, than have to deal with C, or L boards, and I think that would provide more lift too.

except if you pull the board out and clip the boat next to you...

Agreed. Whatever the angle, I can't imagine that moving curved boards back and forth is as easy as straight boards (not to mention the obstruction when they are up).

I'm very curious to see how well the AC crew handles curved dagger boards on the AC72s.

I wonder if a removable T(orY) foil extending off the dolphin striker would provided enough lift or practical/doable?

That would be absolutely doable and thanks for that idea. I might steal it from you.

You could hinge it off the front beam, so you could retract it for launching/retrieving, then flip it down once in deep water. Might have to figure a way to work it around the spin pole, or have it pull up tight to the underside of the snuffer bag when up.

Timbo is on the right track here

Hinge it off the mainbeam with a retainer line of the spi pole. This line will allow the AoA to be set. Place the foil at the tip of a round alu tube and make a loose sitting fairing from foam that youbslide ove the tube. This fairing will weathervane around the tube and thus not act as a daggerboard. As a result this appendage will not be loaded up much in the sideways direction. Two dyneema line may be run from the mainbeam just inside the hulls to the tube just above the waterlevel and thus make for a low cost hinge mechanism and sideways support.

When traversing the surf and landing just pull the foil horinzontal towards the spi pole and clear of the water.

The T- foil may be made of a single 300 by 100 mm piece of multiplex shaped by hand and glassed over. Fit it to the end of the support tube in such a way that it can rotate freely downwards with its trailing edge but never upward past the horizontal. That way the foil can never pull you down. The hinge needs to relatively closevto the leading egde for this. About 25% - 30% down the foil.

A simple rubber end stop will suffice to prevent rotation upward.

At relatively slow speed you pull the assembly a little forward thus maximizing AoA, with increasing speed you relax the line progressively thus reducing AoA and preventing excessive drag and pranching. Fiddle about with a bungee in parallel with the retaining line and get an automated AoA sytem, one that also recognizes pranching by the excessive drag that is associated with it and adjusts the AoA accordingly.

Hell, this may actually work !

Note how even a small diameter tube will be able to withstand the 30-60 kg buckling load. And how a single foil in the middle off the boat with twice the area will have exactly the same overall behaviour with respecttomrighting moments etc as two foils half the size at the tips of the daggerboards.

With respect to foil area.

The total area of boat daggerboards will carry about 120 kg that is the sideways loading of the sails.

However it is best to start with relatively small assymetric foils.

Or make a "U" that just slides vertically in a cassette.

Ummmmm.......

Central mounted foil is a really bad idea. Any lift from it is going to act as negative righting moment against the leward hull so you have added a heap of drag and you have to depower sooner.. if it is tall enough to get both hulls out of the water, you have still almost halved your available righting moment and there for will need to carry much less power.

Having sailed a moth for a few years now, Wouter your T-foil solution won't be reliable. Once a boat is on foils, the pivot point for righting movement is now all on the foil as opposed to being on a 16ft hull touching the water. The foil has to be super strong and can't flex at all. Part of the reason why a Mach2 is faster than a Bladerider is due to the Bladerider foils flexing where Mach2 does not. Plus many many bladerider foils broke due to the loads. The mach2 foil can have a person jumping on them when suspending between 2 benches without any concern at all. And this is the lengths needed for a 30kg boat. Imagine now a boat that is 107kgs and has 2 persons onboard. Breakage city if not done correctly.

The other thing is that there can't be any slop in the system. Has to be rigid. The lengths we go to minimise slop is quite extensive. Reason is that slop means loss of control.

I'm figuring that the difference between full foiling a 30 + 70 kg moth and a partially lifted 107+ 140 kg F16 (for only < 30%) may be an important difference. The F16 will still be carried by the leeward hull for 70% and thus be stabilized. This is basically what the nacra20c and A-cats are doing as well.

Additionally what is the difference between the righting moment of a viper with both L- foils in the water and a single foil in the middle of the viper ? When it comes to righting moment both setups will result in the same overall moment.

Personally, I don't believe that foils are much of a performance gain in most conditions. Hwever the reason I'm interested in them is improved stability of my taipan under spi in big waves especially during long distance racing. For me it is either T-foil rudders or this. This is easier for me to make and try.

Apart from that I'm looking at th following calcs

170 kg crew on my 120 kg Taipan F16
45 kg lift of centrally placed foil
Combined weight carried by bouyancy will then be 245 kg or 110 kg + 135 kg crew.
New rightingmoment will be transformed from 170*3.5+120*2.5*0.5 = 745 kgm
Into 745-45 = 700 kgm = 157*3.5 + 120*2.5*0.5

basically by adding the central foil I expect to get a boat that will partially lift its bows at speed then without thus reduce the dependence of bouyancy to carry to sail loads and wave action.

Secondly I expect to get a boat that thinks that it sailed by a 45 kg lighter crew with the righting moment of a crew that is only 13 kg lighter. The reduction in overall weight ( by 15%) is more then the reduction in righting moment by ( by 6 %).

However, I still don't expect much if any perormance gain except for what is th result if increases stability under spi in waves/ chop

Consider the angle how the t-foil lifts. There is a reason why moths heel to windward. Heeling to leeward like a normal boat just doesn't work.

How about two cassettes(think rudder cassettes) on either side of the mast attached to the front cross bar, with a T foil between the two. You could use the dolphin striker for additional support. Just lower the foil down and raise it back up when not in use. Maybe using a V shaped foil to increase stability and allow the foil to shape around the spin pole.

Doesn't work or doesn't work as well ... ?

I feel flying moths have very little daggerboard in the water and dependent on the Veal-heel canting of the lifting foil to compensate for that.

Doesn't seem the partially lifted cats have the same issues (nacra 20c, A-cats, New Viper)

Wouter. trying to do what you want by hinging off the beam would be an engineering nightmare to get that all important tolerance free fitting, any movement at the beam will be lots of movement at the tip. By engineering a solution will mean lots of extra weight which is going to mean larger foils, more induced drag, even bigger foils to overcome the drag and weight penalties, its a vicious spiral ending in failing to acheive what you wanted in the first place.

Wouter, can you instead use your time and computer model skills to design some nice J boards, they overcome most of the problems, giving good lateral support and some lift. Getting them in and out of the boat is actually quite easy if you think things through a bit. It would mean making up a new case but then even fitting assymetric boards will mean making new cases.

Doesn't work.

We have little daggerboard in the water but this is because you don't need much. When you turn, you aren't trying to turn a 16ft hull that is in the water hence very small amount of vertical foil in the water.

But as for leeward heel being bad, the foils will lift you in the direction of the heel. So if you are heeled to leeward, then when you start foiling they lift more to leeward and on the moth no amount of hiking can counteract this as the foil forces are too high. You have to drop the mainsheet and get the boat flat and then try again being flat or slight to windward. It is a classic newbie moth mistake.

So if you are going to try a t-foil on a cat, the boat has to be sailed flat. But how to get power to foil? The Canadian c-class guys tried all this and brought in Veal but couldn't get it going faster than normal c-class.

J or S foil on each hull a better solution I think.

From above assuming partial lift, an upside down 'Y' appears better than a 'T' ?
Then again assuming partial lift, V or U from the inside shear of each hull at the main beam?

I think the bigger question we need to address is;

1. Do we want to sail in the traditional sense, ie. no foiling, no lifing boards, etc.? (call it Old School)

2. Or do we want to go down the path of full foiling?

(the C cats and Moths have already figured it out, Dave Carlson was foiling his A cat 20 years ago)

3. Or some half-way, in-between measure, ie. C-boards, L boards, J boards... or what have you?

As a class what does the F16 want to be?

1. To even semi foil we add expense and complexity. We further separate the guys who can sail from any potential “new blood”. How many people would we attract, vs. how many would fade away if the class goes on this path? I’m too old to effectively run a spin against younger athletic teams, never mind trying to balance on foils.
2. Do we want to go completely generic and have a heavy 16 footer as being promoted by a number of builders rushing off to Asia. Hack 2 feet off the hulls and recycle all your parts and call it a new thing.
3. For me the excitement in the F16 is what was promised when the rule set first was presented. A light weight fast platform that allowed versatility for its members. Purpose designed and built F16’s can be light. It is still new and the potential for this has not been realized yet, but for a few.
The 16 class has flexibility, where it is not so likely to get caught up in the quagmire the F18 class has going for itself now. There are though, some reasonably thought out restrictions that allow for experimentation, but from a practical standpoint does not force high tech to be mandatory.

If you want foils go join the moths. Every other combination already exists as well somewhere else. You want heavy racing go F18, semi lift foils go A, Line honor racing C20-M20 etc. What is the constant fascination with people to want to f - up the rules all the time.

Just to be clear, I prefer Option 1 from my above post, and fully agree with Mini's last paragraph above.

If it is foiling, it is something else than an F16

Timbo, mini, Rolf,
I thought we already went over the issue of foils in this thread?
http://www.catsailor.com/forums/ubbthreads.php?ubb=showflat&Number=232988&page=1
or is there something new here?

Thanks for the reminder, that was 10 months ago.

Ahhh...the Good Old Days.

My memory is good, but it's short!

Foiling is Dangerous!

And YOU guys are Dangerous!

http://www.funnyordie.com/videos/8afa50b440/iceman-the-later-years-from-nino

At work, they call me Ice Man...but sometimes it sounds a lot like butt-Man!

http://www.youtube.com/watch?v=o2X_XNdmWws

haven't we already answered that in our class rules ?

personally I feel it is wise or the class to sit this one out.

let the hype and huffing and puffing settle down a bit and then decide what to do as a class.

remember the time that all proper cats just had to have outward canted boards ?

wouter

As someone who has raced cats and now sail moths, foils aren't something to rush straight into. It took the moths 5 years of development and the worlds fleet dropped from 100+ to just 30 over that period, but is now re-surging very strong and will probably have its biggest worlds this year. But the development costs were high. Companies like bladerider tried to commercialise it, but the warranty claims and the development costs sent them bankrupt. Plus the main thing is that it nearly made the class extinct. Hindsight could say the move to foils was the best thing the class did. But not a risk for a relatively new class like the F16. And the development is still going on in the moths. We reckon we have added 2 knots of speed every year from the first foilers.

That's the other problem, other than the development costs and bankrutpcy for builders, how many potential newbies are we going to scare off if we go foiling?

As Taipanfc points out, their Worlds went from 100 to 30. Wow! These boats are expensive enough already, without having to pay a Zillion dollars every time you bust a C board.

I doubt I'll stay in the class when the parts get as expensive as the Carbon 20 class (even if only at 16' rates).

Taipanfc, what's a used Moth cost these days? Maybe I'll buy one of those if I want to go foiling:

http://www.mothworlds.org/belmont/

Check out some of those videos, be sure to scroll down to the "Day 5 Highlights", lots of wipe outs in 25knts wind.

New Mach2 moth is US$18k. I believe against F16 cats price and the performance that is good value. Comes with a 2-year warranty.

Used boats for sail found on links on the left-side here: http://www.moth-sailing.org/imca/faces/news.jsp

Yes the fleet numbers dropped significantly, but 2011 worlds had 110 and Italy this year will have more.

Thanks for the link, for all you foiler wanabee's, here's some used Moths...but they make some of our cats look cheap by comparison!

http://www.int-moth.us/used-mothgear-list/

New hull shape. LOL. For casual viewers only. (dangerous)
http://www.gizmag.com/air-support-h...5f8361-UA-2235360-4&utm_medium=email

Who needs a motor, or sails for that matter, when you can foil all by yourself!

(you get a free Mt. Gay Rum comercial too!)

http://www.youtube.com/watch?v=2O5md-0FFGw

They have a moth regatta in Miami on March 16-18. So very good sailors in attendance, so worth checking out: http://forums.sailinganarchy.com/index.php?showtopic=131924

If I can get down there I will check it out, Ben Moon is registered, should be a good show, I hope there's wind!

It's been blowing pretty hard here the past two days, I hope it's not all gone by then.