[teknologika]

I started a similar topic over on the Australian moth forum entitled "Foil development, are we done ?" It was an interesting discussion, so 2 years on with Dougie on the bench I thought we should prove that Doug is not needed for an interesting foiling discussion.

So with crystal ball in hand, I will start things off and try and predict what I think is going to happen.

- Foil shapes will move beyond the square and elliptical shapes to higher aspect albatross sytle wings, chasing lower drag for the same lift.

- Foils sections will now also come under more scrutiny and move beyond the NACA 63-412 and McDougall "bladerider" sections, chasing lower drag and the same or higher lift.

- We will start to see multiple foil sets. It will take a while for someone to win convincingly with them, but once they do, everyone at the pointy end of the field (not me) will start to follow.

Thoughts ?

[wind_apparent]

I see the main foil moving forward to add stability, and the ratio between the main foil and rudder foil shrinking so that the two share more of the lift load.

[bistros]

wind_apparent, on Jan 1 2009, 10:16 AM, said:

I see the main foil moving forward to add stability, and the ratio between the main foil and rudder foil shrinking so that the two share more of the lift load.

This is however increasing resistance to "yaw" maneuvering as well. Turns will be slower, and the crew's ability to instantly adjust trim in the "pitch" plane will be dampened as well. It will be interesting to see if these "long wheelbase" designs accomplish the goal of stability at the price of tactical maneuvering.

The other handling issue I wonder about with this design is the overall effect on the CLR/COE balance. In a steady state you can balance both effectively. When the rudder is turned, the lateral resistance of that end of the equation drops, and this may cause weather helm, as the CLR balance is now skewed towards the forward foil.

All my comments are from a non-foiling, peanut gallery perspective - those who foil will have much better ideas.

[wind_apparent]

bistros, on Jan 1 2009, 03:57 PM, said:

wind_apparent, on Jan 1 2009, 10:16 AM, said:

I see the main foil moving forward to add stability, and the ratio between the main foil and rudder foil shrinking so that the two share more of the lift load.

This is however increasing resistance to "yaw" maneuvering as well. Turns will be slower, and the crew's ability to instantly adjust trim in the "pitch" plane will be dampened as well. It will be interesting to see if these "long wheelbase" designs accomplish the goal of stability at the price of tactical maneuvering.

The other handling issue I wonder about with this design is the overall effect on the CLR/COE balance. In a steady state you can balance both effectively. When the rudder is turned, the lateral resistance of that end of the equation drops, and this may cause weather helm, as the CLR balance is now skewed towards the forward foil.

All my comments are from a non-foiling, peanut gallery perspective - those who foil will have much better ideas.

I'm thinking minor movement forward, maybe 100-150mm forward, and not in front of the mast like Mirabaud. and maybe 5% -10% more load on the rudder.

[BalticBandit]

wind_apparent, on Jan 1 2009, 03:16 PM, said:

I see the main foil moving forward to add stability, and the ratio between the main foil and rudder foil shrinking so that the two share more of the lift load.

I think there will be experiments in heavily swept main foils - both forwards and backwards that increase pitch stabiliity so that the rudder is not necessary to have lift. This will reduce drag and sensitivity to fore/aft body weight. Along the lines of the modern "flying wing" fighters and bombers

[Amati]

Have you guys see this?

http://www.foilkayak.com/videos/

I know its a canard setup, but it could be a future Moth idea? One thing I found interesting was how much side to side (swivelling?) and even up and down movement the foils could handle- because of the different directions of torques created by the paddling- rudder's in front, too....

Paul (Happy New Years!)

[Amati]

A quick question- I'm wondering why Moths use such short horizontal (lifting) chords- so short that they must be operating in the sub 500,000 re regime more than some of the time. That regime is notorious for non reattaching flow separation, flow hysterisis in extremus, etc.. It seems the main argument for this might be wetted surface(?), but drag from stressed flow must be an issue for sub 500,000 re chords.

For example, the chord re of a 3" chord at 10K in fresh water is (based on the formula: (Speed (knots)) times (Chord (feet)) times (137,250)= chord re). You have to be close to 15K before you get above 500,000 chord re. Which is probably why 0012 was jettisoned pretty early on, as it is horrible in the sub 500,000 chord re regime.

But a 6" chord gets you above 500,000 chord re at 10K, which means you might not have to develop proprietary foils, and use more public domain shapes. Maybe a 8" chord section with a shorter span with endplates might do the trick and keep ws down? (which is kind of what the foil kayak seems to be doing, at least up front.) Given the circulation of waves, a section of high aspect ratio that develops lift at low aoa might not be as important as a section that develops usable lift through broader aoa range? And if the longer chord section pops out of the h20, might it not crash as bad since it might plane a bit instead of stalling? Might work better at sub flying speeds too, since chord re would be more out of the sub 100,000 chord re (aka the strange) range. Like just under 3K. Might be less induced drag at low speeds too? Mav's are going to lower aspect ration at low re's. <_<

Paul

[Phil S]

Some wide chord foils have been tried but the problem appears to be wetted surface from standing, basically the hull plus 50% extra surface on the foils is enough to make it hard to achieve take off speed. Once up and flying things are more equal.

Moving foils forward has a couple of issues too. With the main foil too far forward there is too little hull up front to save the boat when the foil vents or otherwise loses lift. Its safer to touch down than to nose over.

The other issue is that when healed to windward the verticals begin to take weight, just as the horizontals take up lateral resistance. If trimmed so that the aft foil carries too much weight (ie crew aft) then when healed this results in heavy lee helm on the tiller as the weight is transferred to the vertical rudder and hence the tiller.

I think there is a lot of development left in moths. Foils will certainly get better, better sections and higher aspect ratios as structures get better, I agree that multi foils and multi rigs are inevitable. The little guys are now being out paced by big guys once the wind id up so I see them switching to shorter #2 rigs very soon, smaller foils will follow when its windy, so we can get downwind safely and faster.

I think there will always be two foils because the pitching moments variations from high level thrust and low level drag, is too much for tailess reflexed foil sections to handle. So deltas and swept wings do not appear to have any advantage, especially at low speeds and take off.

What we are asking these foils to do is really a lot more than is asked of most aircraft. We want high lift drag ratios all the time because we do not have very much power available. When we do have plenty of power we need to resuce lift to prevent break out. We want max lift when we have minimum power (light wind take off)

Hull and rig windage need attention and since the crew is such a big component clothing will need attention. We may end up lying on the wings to reduce windage.

C Class type wing rigs will happen one day. Durability and weight issues have to be worked out, but its not impossible.

[Amati]

[quote name='Phil S' date='Jan 1 2009, 10:23 PM' post='2067132']

The other issue is that when healed to windward the verticals begin to take weight, just as the horizontals take up lateral resistance. If trimmed so that the aft foil carries too much weight (ie crew aft) then when healed this results in heavy lee helm on the tiller as the weight is transferred to the vertical rudder and hence the tiller.

That's assuming steering at the stern?

(What can I say, I've been running across a lot of articles about the benefits bow steering.) :P

Paul :lol:

Tom Speer had a point about sailing with heel being a disvadvantage, advocating keeping things upright. Does Moth practice prove otherwise?

[teknologika]

Amati, on Jan 1 2009, 09:52 PM, said:

The other issue is that when healed to windward the verticals begin to take weight, just as the horizontals take up lateral resistance. If trimmed so that the aft foil carries too much weight (ie crew aft) then when healed this results in heavy lee helm on the tiller as the weight is transferred to the vertical rudder and hence the tiller.

That's assuming steering at the stern?

(What can I say, I've been running across a lot of articles about the benefits bow steering.) :P

Paul :lol:

Tom Speer had a point about sailing with heel being a disvadvantage, advocating keeping things upright. Does Moth practice prove otherwise?

If you haven't already you might want to have a listed to Phil's episode of mothcast. In that episode he talks about his bow rudder experiences, and there are some pics on the site.

We have found that healing to windward when going upwind is an advantage from both a righting moment and being pushed to windward by the hydrofoil point of view on a moth.

[Amati]

teknologika, on Jan 1 2009, 11:50 PM, said:

Amati, on Jan 1 2009, 09:52 PM, said:

The other issue is that when healed to windward the verticals begin to take weight, just as the horizontals take up lateral resistance. If trimmed so that the aft foil carries too much weight (ie crew aft) then when healed this results in heavy lee helm on the tiller as the weight is transferred to the vertical rudder and hence the tiller.

That's assuming steering at the stern?

(What can I say, I've been running across a lot of articles about the benefits bow steering.) :P

Paul :lol:

Tom Speer had a point about sailing with heel being a disvadvantage, advocating keeping things upright. Does Moth practice prove otherwise?

If you haven't already you might want to have a listed to Phil's episode of mothcast. In that episode he talks about his bow rudder experiences, and there are some pics on the site.

We have found that healing to windward when going upwind is an advantage from both a righting moment and being pushed to windward by the hydrofoil point of view on a moth.

So stalling the bow foils out and not being able to tack was a problem? :blink:
(Kind of like a sticking #14 damper on a 9'6" Bosendorfer!)

So much for the advantages of the canard system. Seems like the canard was a canard! :lol:

But seriously, trying it was very cool. And trying counts, a lot, in my book-

Paul

[The Black Pearl]

I would think we are going to go the direction of windsurfing fins. Once foiling, the issue has to be drag not lift. Therefore in windier conditions, wont we see people trying smaller, lower drag foils with the potential to boost top end speed......

[atypicalguy]

The Black Pearl, on Jan 1 2009, 09:34 PM, said:

I would think we are going to go the direction of windsurfing fins. Once foiling, the issue has to be drag not lift. Therefore in windier conditions, wont we see people trying smaller, lower drag foils with the potential to boost top end speed......

You first.

[Major Tom]

What about being able to change the AOA of the front horizontal on the fly? I know it has been discussed here before, but having sailed a BL with too much AOA I can say that once the boat is foiling it reaches higher speeds than the same boat with a lower AOA. The problems with a higher AOA are at take off in light air, as the bow lifts out of the water the AOA increases and the foil is prone to stalling, during gybe and tacks the foil can stall in light air and when the boatspeed exceeds a certain amount, in my case 16 knots upwind and 18 to 20 knots down wind it is impossible to keep the foils in the water. However, at slightly lower speeds the boat is ridiculously fast although sailing with the wand hardly ever touching the water is a bit disconcerting.

[MHBryce]

just out of curiosity.. are there restrictions on the amount of foils a moth sailor can use in any given regatta? last i heard the only thing they needed to keep the same was the hull?

[bgulari]

MHBryce, on Jan 2 2009, 01:37 AM, said:

just out of curiosity.. are there restrictions on the amount of foils a moth sailor can use in any given regatta? last i heard the only thing they needed to keep the same was the hull?

That is correct. I am under the impression if someone does pull off multiple foils and does really well the rule might be examined again.

[BalticBandit]

Major Tom, on Jan 2 2009, 08:45 AM, said:

What about being able to change the AOA of the front horizontal on the fly? I know it has been discussed here before, but having sailed a BL with too much AOA I can say that once the boat is foiling it reaches higher speeds than the same boat with a lower AOA. The problems with a higher AOA are at take off in light air, as the bow lifts out of the water the AOA increases and the foil is prone to stalling, during gybe and tacks the foil can stall in light air and when the boatspeed exceeds a certain amount, in my case 16 knots upwind and 18 to 20 knots down wind it is impossible to keep the foils in the water. However, at slightly lower speeds the boat is ridiculously fast although sailing with the wand hardly ever touching the water is a bit disconcerting.

I'll bet we will see some experimentation with deformable foils - ones that have a higher lift shape at low speed and a lower drag shape once foiling. That leaves the TE free to just deal with keeping altitude, which in turn reduces drag and increases speed

[FishAintBiting]

bgulari, on Jan 2 2009, 11:21 AM, said:

That is correct. I am under the impression if someone does pull off multiple foils and does really well the rule might be examined again.

Altering the rule may not be a bad call. How much extra would a second, or third, set of foils set a sailor back?

Having the sailing a war of weapons, read- biggest pockets, isn't always the best solution.

Fish

[Doug Culnane]

FishAintBiting, on Jan 2 2009, 11:32 AM, said:

Having the sailing a war of weapons, read- biggest pockets, isn't always the best solution.

Sailing is a war of weapons where big pockets win races. This is a fact, it always has been and always will be.

No one has yet been able to write a rule that:

Allows people to repair gear during the event.
Allows people to get tips and help on their set up and make improvements during the event.
Allows people to bring spare gear so they can complete the regatta if there are gear failures during it.
Allows people to use storm sails if it is a bit too windy for them.
...and...
Stops people from modifying their boat set up.
Stops people from swapping gear because they broke stuff (by accident after a bad race by driving over it in a car).
Stops people from bringing multiple rigs, and foils.
Stops people from traveling to international events to get experience, which gives them an unfair advantage over local sailors.
Stops people sailing for more than 10 weekends a gear and getting unfair practice in.

If you think I am being ridicules then write the rule, that allows me to turn up like I did in Garda 2007. I had 1 hours practice in converted lowrider. I broke a main foil and had terrible set up. Throughout the event I bought a new foil fitted it and totaly changed and evolved my set up with great advice and help from fellow sailors and ending up having a great enjoyable event. A one equipment rule would have totally stuffed up my regatta. If you can write the rule that allows me to compare fairly with rohan and amac who turned up with a coach loads of spare gear, and 3 weeks pre-worlds training then I will also support a one equipment rule.

[sailingkid]

Its amazing how good foiler threads are when Dougs not around... :D Suprised someone hasent started an online petition to stop him from ever coming back.

[sailingkid]

Acctually maybe he's still here: I have photographic eveidence of a reported sighting.

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[TeamFugu]

Equipment rules are tough but I think competitors should be allowed to bring spares for parts that often break. For Stars, that is usually a quiver of spars. Not because they have different characteristics but hey are so under built for the purpose, they frequently break.

As for foils, I've often wondered if either the albatros wing shape or more like a tuna fin might not be a good option. Maybe the ends could be made slightly flexible to auto fair like we expect out of our carbon masts. It can't be too soft or the fin will wobble and just cause more drag.

As for the cost of a quiver of blades, it could run anywhere from $1,500 ot $3,000 per set. Not a trivial expense and I too think this will be soon in coming. Big changes in shapes and configurations will have to come with new construction techniques and materials. What that is I don't have a clew right now. The hard part is that you have two opposing requirements. More dynamic control over AOA and other aspects of the foils and simplicity so that you can pay more attention to what is going on off the boat than on it. If a Moth were a two or three up boat, it would not be such a huge problem but on a singlehander, you have to remember that there is only one person with two hands and one mind.

[bgulari]

TeamFugu, on Jan 2 2009, 06:50 AM, said:

Equipment rules are tough but I think competitors should be allowed to bring spares for parts that often break. For Stars, that is usually a quiver of spars. Not because they have different characteristics but hey are so under built for the purpose, they frequently break.

As for foils, I've often wondered if either the albatros wing shape or more like a tuna fin might not be a good option. Maybe the ends could be made slightly flexible to auto fair like we expect out of our carbon masts. It can't be too soft or the fin will wobble and just cause more drag.

As for the cost of a quiver of blades, it could run anywhere from $1,500 ot $3,000 per set. Not a trivial expense and I too think this will be soon in coming. Big changes in shapes and configurations will have to come with new construction techniques and materials. What that is I don't have a clew right now. The hard part is that you have two opposing requirements. More dynamic control over AOA and other aspects of the foils and simplicity so that you can pay more attention to what is going on off the boat than on it. If a Moth were a two or three up boat, it would not be such a huge problem but on a singlehander, you have to remember that there is only one person with two hands and one mind.

The more i think about it the less i believe that having different size foils will make that big of a difference.(funny i was not going to explain but doug is not around)If we are doing W/L races if we did reaching where sometimes when the breeze is up we have to sail the death angle i would agree with smaller foils would be worth exploring actively

you still need lots of lift a lot of times downwind(trying to get the bow out of the water when it has come down off a wave) when the breeze is up and you also need lots of lift at certain downspeed moments going upwind. Even when the breeze is up.

[Doug Culnane]

I agree that if you are doing W/L courses the boat speed is always around 14 to 18 knots and so the foil size is about right. This factor and the fact that in the past a well set up boat has been much faster than a badly set up boat so people have concentrated on getting their set up right. Getting one set of foils working well is hard enough without having to do this for a quiver of foils.

I think the day of multiple sets of foils and rigs will come but I just can not see how you can write a rule to make this fair. There is the danger that a one equipment rule will hurt the back of the fleet more than the front. It will also hurt development ideas because people will be reluctant to take risks on equipment. The back of the fleet also profit for the discarded gear that the front produce.

So a rule needs to really be clear about what it is trying to stop. This is why the IMCA have not tried to ban stuff that has not yet happened. I am not saying it will not be a problem but this is why at the current time the IMCA have not gone for a one equipment rule. I also have not seen anything close to a workable rule being written.

[Doug Culnane]

TeamFugu, on Jan 2 2009, 02:50 PM, said:

As for foils, I've often wondered if either the albatros wing shape or more like a tuna fin might not be a good option.

This is pretty much what the rudders are. The main foil plan shape has the compromise of the flap hinge to consider.