Foiler Design

[Cloudsipper]

Re:Sailrocket

Thanks for the site pointer...Gosh has it been 40 years? Yes, that's the basic idea, end up with no overturning moments. He (Smith) based his designs on bouyant hydrofoils, (TSpeer.. any thoughts? )but at running speeds, there was little more than a skeg-sized piece in the water. He even suggested curving the foils to deal with the different operating regimes.
I tried models BTW, and couldn't get them stable AND pointed into the wind until I hit on a dual 'wing' design: one above each of the leeward foils. It had a natural stability, rather like a cone. In addition, each airfoil could be pivoted 180 degrees to 'fly' in the other direction. Hmm.. the rounding of the bouy would mean driving past it, stopping, and taking off on a new tack.. I guess if you were fast enough to begin with ....
..It's interesting, but Smith forsaw the sail kite, I seem to remember his dismissal "but alas the thought of a soggy kite..in the water..".

 

[Cloudsipper]

Dual medium flow tank and wind tunnel?

Has this been done? The goal would be to balance the forces for a specific design of sailboat perhaps by making the water run downhill at some particular angle, blowing air on the sail at a speed to neutralize motion. Sounds really complex, but could illuminate a whole raft of issues. Of course you can always simulate the behavior with computers.. but you don't get to build as many models

 

[National3434]

Re Sailrocket

Sailrocket has just been launched (but not sailing yet) See their website www.whbs.demon.co.uk/sr2/content_fr.htm
Cheers
Tom E

 

[National3434]

A discussion Q. from another thread

Wardy wrote this as part of a contribution to the 'Lightest Rig' thread:

{"My experience is that the tall rig is definitely more efficient and actually works well and feels good, but it really requires a stiffer mast. That is why I use spreaders. The only downside is that it contributes a greater pitching moment than a standard rig, which makes it even more difficult to maintain height & pitch control while foiling. It is the height and pitch control which is the greatest technical problem for Moth foiling.

I have had many ideas on how to solve this pitch and height control problem and am still working to achieve a really good, simple solution...
Any ideas on this are most welcome!!"}

And this is my rather rambling response:

With respect to the height and pitch problem, my first prototype will be a miller foil configuration but with an oversize front foil to give pitch stiffness (same area as the main foil). This should mean that there is always a reasonable lift margin ...but of course I have not tried it yet! Boat still in build and deadlines are coming up fast (Europeans in July).

If I try to rethink it all I often come back to the old Russian hydrofoil ferry configuration of foils near the bow and stern, both surface piercing. It seems so secure and stable. Only trouble is you need a few thousand horsepower to get it to rise and waves on the great Russian rivers are, I guess, not a big issue. But something on those lines would nearly double our 'wheelbase' and make the whole thing less pitch sensitive.

I remember reading something about the Mayfly and Icarus foiler cats that they found a partial foiling mode to be faster on average. Not that full foiling was slower, just less reliable.

You mentioned in a previous posting, or hinted at, a fully surface running foil system (like miller foils at all lifting points). I reckon that is a hydroplane and has the potential to be seriously fast if the control problems and the problem of getting it to lift in the first place could be sorted. Yellow Pages / McQuarie Innovation is a hydroplane but uses bouyancy rather than foil lift to get fro zero to 'planing. Then there is the wave problem; but would wave slicing foils be better than hulls for this? Does the Miller foil work in slicing through waves?

Looking at hydroplanes a different way, Yves Parlier ( www.parlier.org and www.sailcity.com/news/viewImageCat.asp?catID=3 )and sailrocket ( see previous post ) are taking a serious look at bouyant hydroplaning solutions. One for speed with seaworthiness and the other for pure speed with some seaworthiness. Their hull forms would not be difficult to incorporate in a Moth. Perhaps a hybrid foil assisted hydroplane has potential as a better way to do that semi-foiling mode?

By the way, is there a definitive distinction between planing and hydroplaning? Any offers?

Cheers

 

[Wardi]

Tom,
Firstly a long wheelbase is definitely a possible solution. I already tried a rudder foil and sensor operated bow foil with no centreboard foils at all. This worked very well and could be an excellent solution. The foils were too small and I broke the forward strut, so I will now build another version.

The Miller canard will work, but I suspect you will be faced with the problem I am right now trying to solve. It gets up and goes OK, but if it is a fixed canard, when the bow is pressed down while foiling, the bow down attitude of the boat results in lowering of the canard angle of attach significantly. The boat slowly comes back to the water. If you try to put on too much angle of attack to overcome this, it stalls on the way up. I have tried very many solutions, the latest is an independently pivoting canard, which finds its own positive angle of attack when both submerged and planing...not easy to do I might add! Still testing this today!!

I don't see any difference between planing and hydroplaning.

Perhaps it would be possible to use the foils submerged up to say 20 kts and then allow all of them to pop free and surface run as planing foils. This could be done using the surface running canard foil I have just developed...but lets see how well it works as a canard first!

 

[Wardi]

L'hydraplaneur

Do you think this L'HYDRAPLANEUR will really work!
Looks like tremendous drag in most conditions!
My own experience says foiling is far more efficient than planing. It is the control problems and perhaps cavitation which cause the ultimate limitation for foilers.

 

[Andy P]

there are some pics in Seahorse of the Parlier cat.... the hulls are quite narrow .

and apparently 25 knots in 15 knots of wind.

but light wind performance must be poor

 

[Wardi]

With such a huge sail with low heeling moment and immense righting moment its no wonder that it can go fast...but is it really that efficient?

 

[National3434]

Parlier

With such a huge sail with low heeling moment and immense righting moment its no wonder that it can go fast...but is it really that efficient?

I don't know that it is meant to be a light airs flyer, it was built for transocean racing. I don't follow the french stars that much but Parlier has got a reputation for trying new ideas and making them work. This one has been in the oven for several years, including a 20ft development version. He will be racing the beast across the atlantic single handed in the next few moths so I guess the race course will be the proving or otherwise, of the concept. To me the hulls look just like seaplane floats and I cant help feeling that she will slam and jump in waves.

Parlier is the guy who got dismasted in the Vendee globe race, pulled into a cove in NZ, repaired and restepped his carbon mast without outside asistance or going ashore, lived off shelfish in the meantime and proceeded to sail home to France to complete the race. I don't know much about the others but this guy is outstanding. Definetly worth watching.

But the application to dinghys is not so clear!

But back to foils. Wardi, could you tell us what sections have you tried for the Miller style front foils?

Cheers

 

[National3434]

Moth foiling has now broken out in Europe! www.moth.nl/foiling.html

 

[Wardi]

Canard design

Wardi, could you tell us what sections have you tried for the Miller style front foils? Cheers

In the beginning I copied the Miller meat cleaver canard, 450 x 100mm. This had lots of drag when submerged, which is not a problem for Miller as he does not sail in under 12kts of wind. It was also too small when foiling.

I altered this to make it bigger. It is now 450 x 300mm and faired in the back of it to make a simple assymetric foil with flat underside, but retained the sharp leading edge for shedding air when it goes through waves.

It is pivoted freely on its centre plane about 20% from the front. A simple control wire sets a fixed angle of attack. If the boat noesedives or crashes, the foil pivots up freely and will not drive it down..a big safety feature.

The main problem is that when the boat is foiling and gets a gust or you sheet on, the bow is driven down and the angle of attack of the foil is reduced, it simply comes back down into the water. This is primarily a problem due to the short wheelbase of the Moth and may not occur on larger craft. Even the Miller sailboard has about twice the wheelbase of the Moth, because he stands at the back.

I have tried very many configurations of surface running canard, most with little success.
The best compromise which I am testing at the moment is a "Reflex" :idea: canard, which has a reflex or lift up at the back of the foil. This generates lift on the foil while submerged. If set up properly, it will lift the bow up at the correct speed for foiling!.

The main benefit of this design however is that when it gets to the surface, the angle of attack of the front underside surface of the foil is highly positive and it is far more resistant to diving once foiling. This is not fully proven yet, but if it can be refined to work properly, this offers the very best solution as it is simple, cheap, safe, easily fitted and offers the very best surface tracking. If sailed properly, it only touches the water surface some of the time, and so has minimal resistance.

I am also still working on a design which senses when it gets to the surface and automatically alters the centre of lift of the foil, so that it works equally well planing and submerged. This has not be achieved to date as far I am aware.

 

[boogie]

hey wardi,

have you ever thought about a more radical change in the foil to sail to centre of gravity configuration?

to increase the wheelbase you could for example make the rudder the main lifting foil and get rid of the centre board completly or have it retractable with no foil for sub-foiling conditions.
the rudder could be like a centreboard lifting foil with a huge vertical trim tab. mount the foil rudder under the back of the hull [where usually the fin on a windsurfer is. bring the mast [or rather COE of the sail] back to match the centre of lateral resistance when sailed heeling over to windward.
so that when you go faster and start lifting out of the water [reduction in lateral area] the lifting foil takes over some of that lateral duty by tilting over to windward, which would reduce the lift for level flight as you go faster due to the split of the force from the foil into vertical and lateral.

the surface tracking foil at the front would have a good lever against the pitching of the sail but might need a portion of the vertical foil/strut submerged to help having a pivot point for steering.

i think the biggest holdback in the development of foiling dinghies is trying to convert existing designs. more thinking outside the box might be required...

cheers
boogie

 

[Wardi]

What you are describing is essentially to set up a Dinghy like a Sailboard, ending up with the rig and crew at the back of the boat.
This is also where the 14'skiffs are heading due to their rule restrictions, although they will need a surface running shoe at the bow instead of a canard as they are only allowed one foil.

I do agree your proposal is feasible, and could foil OK, but it would be a disaster in displacement conditions under say 7 kts of wind, or require mechanisms to pull the rig forward in light air etc. The way I see it, by using a central lifting foil, you are in effect moving the rig aft, by moving the back of the boat forward when you start to foil, instead of physically moving the rig aft!...if you get my drift!

While I agree to thinking outside the box, I do not also want to compromise an all-round excellent performance that is offered by an existing dinghy. That is why I would prefer to find a simple way to make a dinghy foil, rather than make a sailboard work in displacement conditions. Unless of course a radical solution solves all of these issues at once.

One idea I have recently proposed is to have lifting foils at both ends of the boat and not on the cenreboard. I have tested this and it works well.
In this case I am not moving the rig and crew aft, but it can achieve what you have proposed, except that the forward foil is load carrying and must therefore be submerged rather than surface running.

 

[alans]

This machine was inspired by the work of Bernard Smithand is going after th World Sailing Speed record.Most boats of this type can sail only one direction; apparently this thing and sail two directions.
While manouverability and round the buoys racing is out of the question the most important aspect of this boat is worthy of study: it develops no heeling moment! Therefore stability is not a factor in how fast it will go..more:
http://www.yachting-world.com/auto/newsdesk/20030028110712ywnews.html

If you are looking for a machine that can race around the buoys at something approaching WWSSR time have a look at the concept at http://home.kooee.com.au/zach/hydrofoil.htm
the site is still being edited and may change over the coming weeks.

 

[Berth]

One idea I have recently proposed is to have lifting foils at both ends of the boat and not on the cenreboard. I have tested this and it works well.

Hi Ian,

What is your experience with such a geometry concerning tacking and jibing?
That´s why Andy I remember didn´t follow this way. He wasn´t able to turn the boat round the corner with that large wheelbase.

berth