Foiling week 2018 Part 1 – composites and foils – Sydney

I wasn’t expecting to go to Foiling Week 2018 at Woolahra Sailing Club on Sydney Harbour but ended up there last week.

I’m more than a bit jaded by foiling – I think it is almost totally irrelevant for attracting people into sailing – despite what headlines say and the hope being placed on it.

So why was I there … ?

Wood for foiling and doing it simple

I’ve had a long correspondence over the years with Ian Ward who was one of the main people who made Moth foiling possible – back when everyone home built their foiling equipment and shared information to speed up the rate of performance improvement and control for everyone.

He is currently developing and marketing the Glidefree foiling system which is a plug in for Lasers, the RS Aero and other conventional dinghies. I’ve thought it was overpriced, but Ian had a brilliant explanation for why it is the way it is that has implications for foiling for the rest of us. That is “normal people”.

Ian invited me along because it was a chance to meet Michael Aeppli of the Quant 23 (and other projects) who was visiting from Switzerland.

When I first saw photos of the Quant 23 I thought it was yet another case of selective photos and videos.

See my article on Foiling Fakes where I explain more about this.

but Ian, who had already been sailing on the Quant in Switzerland put my mind to rights. I was wrong and Aeppli was doing something interesting and different. Boats that anyone can sail

Both Michael and Ian along with Melbourne lightweight boat builders Jim French and his son David (also moth people) have very different thinking about foiling from the mainstream.

Jim and David are working on easy to sail variants of the scow moth in conjunction with Ian Ward. This is their trifoiler moth that has just been reconfigured as a bicycle configuration.

I want to explain this difference between what the “foiling for everyone” group in depth as I had a really good chance to talk to Ian, Michael, Jim and David about foiling for the rest of us. But first, lets  join the Hoopla of mainstream thinking in this Part 1.

It demonstrates how the proponents of performance foiling are thinking now.

I’ll use Ian Ward’s lecture and my conversation with Michael Aeppli to put forward their alternative approach, which I consider much more realistic and much more important to “normal” people and real use in Part 2 of my Foiling week report.

Mainstream position about Foiling Sailboats

The mainstream position seems to be that speed and expense will save sailing; And very solidly view foiling as “The Future of Sailing”.

This was the theme repeated many, many times in the couple of hours of talking. But as I will show it is not the full story by far in part 2 of this article.

Here is a quick summary of my notes

Lecture 1 – Foil structure, engineering and testing – Brett Ellis most recently of the Artemis America’s Cup Design Team

Brett was working as an engineer on the campaign foil design.

Current software development has moved away from separate modules and processes for hydrodynamic design then trying to design structures to handle the expected loads

The current software is based around FSI (Fluid structure interaction) where both structure and hydrodynamic optimisation occur simultaneously. This way the operator knows if the hydrodynamic model is also designed to handle the loads expected as it is modelled.

In the old method the hydrodynamic design would be done and there would be no idea if it was practicable until the structures team was able to work it through. So a lot of hydrodynamic work could be done only to find it was not structurally possible, or would differ significantly in configuration when sailing loads were applied.

It also allows the “flying shapes” of the foils – the actual shape they take up under load – to be used for the lift and drag calculations. Much closer to the real world.

So a big streamlining in work process. It can also do full FEA (Finite Element Analysis – an accurate mapping of stress and strain) of the structure at the same time, but this means that the computer run becomes an overnight one rather than something that happens in a few minutes.

So clearly the modelling process is up against the limits of affordable  hardware (even for America’s Cup Syndicates).

Most problematic loading situation for foils is delamination when the load on the foil goes negative – the foil is pulled downward. This can be planned – for a gybe negative pressures are used to drag the foil into full down mode or accidental – nosedives, clipping wavetops on the windward foil.

Most foils at this  are “L” shaped.

Negative rake makes the foil suck down into the water, whether intended or  not.  This makes the curve of the board “open out” putting large tension stresses on the inside of the curve. This tension, in turn, makes the laminate layers want to pull straight, pulling them up and away from the surface with the only thing resisting them pulling apart is the tensile strength of the resin between the carbon laminations.

Foils are tested to a large proportion of working strain before use and are ultrasound checked each night after sailing – looking for voids or other increasing defects which are mapped to keep track. Team New Zealand had a situation like this in the last race before their win – they were uncertain whether one of the their main foils would survive.

Real time Data from multiple sensors.

The foils are also fitted with a moulded in fibre optic system that gives a continuous data stream at 50Hz – 50,000 measurements a minute. It is possible to correlate any manoeuvre with the strain/displacement of the foil (and many other parts of the boat) with the built in strain data from fibre optics real time on the boat (warning when the loads are getting too high and to back off a bit) and also as an analysis after the event.

There is almost “too much data”.

For more background see this series put out by Altair, the software developer for composite foil design. This is a playlist, so don’t just watch the first one.

Lecture 4 – Tony Stanton, Composite Structural Engineer with Gurit Composites.

Tony’s talk was mostly on the Composite side with information of where composites are at  now and where they are going. Also the next  step for foils.

Here he is discussion core arrangements for large boat hydrofoils. The weak point is again the loading at the bend of the foil. Most failures are because the internal web structure that transfers the load between the compression and tension sides collapses. Another main cause is delamination at the bend (as per above).

Nanoparticle prepreg.

A prepreg is a cloth that has already been impregnated with resin under pressure. The roll or panel of cloth is generally stored cold. When placed over a mould, pushed into conformity with vacuum bag or autoclave pressure and the mould or compartment is heated the prepreg will harden to full strength.

The prepreg process allows pressure to be used to force the resin into the cloth to get much higher cloth to resin ratios.

One of the problems for composites is that the fibres have very high material properties and the resin has quite low properties – resin is relatively flexible. The resin in the gaps between the fibres, flexes which means the fibres move because the resin doesn’t restrain the fibres sufficiently.

For Nanoprepreg the resin is mixed with nanoparticles of a material with higher modulus (stiffness and/or strength). The nanoparticles take up a large proportion of the space between the fibres so there is less resin. (Law of admixtures for engineering types).

This can only be implemented in a prepreg (I suspect) as the nanoparticles making up a high proportion of resin content will make the resin very thick, requiring high pressures to wet out the cloth adequately and distribute the resin through the fabric.

The end result is that the resin in the matrix can’t move as much. The improvement for the stiffness of the component can be up to 25%.

Measurement of deformation and displacement of tested components

This is a method for comparing computer model flex with the actual real life component.

Manufactured components are loaded up in a test jig. Dots on test piece show strain and displacement. Strain is when the dots get further apart or  closer together. Displacement is when dots move the same amount – the whole piece moves in that area.

A lot of this work is working towards calculating of flying shapes. The old way, parts were designed in the shape wanted and there was the hope that the shape would be OK when loaded up and flexed to a new shape in real use.

Now the computer model takes this into account and the shape is designed in its ideal shape with stresses applied and then relaxed to find the shape for manufacture.

Rethinking hulls actually needed for foiling yachts. Design for Crash and Burn.

Foiling has vastly reduced the impacts a boat may be expected to meet in normal sailing mode. Impact from waves has been significantly reduced. Foiling boats also suffer considerably less impact from pitching as it is damped by the foils.

A conventional trimaran enters and leaves the water upwind

A foiling trimaran in rough water has a much smoother movement.

But the landings hurt more when something goes wrong. It can be as simple as the lifting part of a foil coming too near the surface of the water. Remember too that the Moths are by far the most successful sailing foilers. Let alone what happens with much bigger boats – but they crash regularly. It is even more dramatic when 15 tons of big mono or multi falls off its foils.

This much more serious worst case of the boat falling off the foils has meant the development of hull structures  will hit so design for worst case maximum energy absorption.

Dynamic test drop rig results show that flexible cores are the solution. If the core is rigid in a critical structure and overloaded it will fail and then be unable to transmit loads between the compression and tension faces of the structure – so the panel doesn’t survive and may no longer be watertight as the skins won’t be contrained and are likely to be overstrained and break. But more flexible cores mean the whole structure is more robust (survivability) and able to retain its watertightness and quite possibly its full function.

How foils will look in the near future

The upcoming era we will see more flaps built into the foils.

This means the end of the curved foils to a large extent as the foils are harder to articulate – ie design for the flaps to move.

So likely the next era of big boat foils will be back to T foils to allow flaps that will allow the foil to operate for high lift or switch to low drag.

The boats at Foiling week #1 – the Moth

The Moth is one of the few true foiling machines. They hit the water all day and are instantly up foiling and sailing nicely. They were the only boats on the water on Friday which were impressive.

Their  main difference is that they have the water sensing “wand” at the bow which operates the flap on the centreboard foil. This sets average ride height automatically.

The rudder lifting foil angle is controlled by jacking one of the rudder fitting in and out and is controlled by a linkage from a twist grip on the tiller extension controlled by the sailor. This controls the attitude of the boat – with bow up for maximum lift or bow down for minimum drag.

Controlled by the human brain.

The Moths also have no minimum weight so are very light.

They can take off in 4 or 5 knots of breeze and interestingly if already up can coast through light patches of 2 to 3 knots of wind.

Interesting on Day 1 of Foiling Week 2018 the moths were the only ones to get much foil sailing time

Photo gallery of Moth Foilers

In a way there is nothing to see here. The boats just work and have done so for quite some time

Waszp One Design

Essentially a simplified Moth produced around the $10K mark – about half the price of the Moth. It is one design, which may or may not be a good idea for a field in its early days.

Some neat bits – like 6061 aluminium (we can’t get aluminum – was eaten by the drop bears) alloy extrusions for foils help keep the cost way down.

From an industrial design angle it really has done well to get the weight down to reasonably near the all carbon structure of the real moths.

A-Class Catamaran

The A-class group can’t decide whether to go full on with foils or whether to preserve the traditional low riding version of the boat.

At this point the foiling boats are fast enough to win the top 10 or so places in a regatta, but not the utter domination we saw the moth develop.

The Moth is pretty much as fast as the A-Class – which has been something Moths achieved over a couple of decades by backyard builders.

The A-class on the other hand has been a pretty expensive boat for a couple of decades so it is down to only a few developers. The chap who owns this boat dropped one of the foils over the side coming into shore – thats $3500 worth of kit, so he spent some  time  looking for it.

Because the A-class can’t commit to foiling they have prevented  the adjustment of foil angle or the fitting of adjustable flaps like the Moth.

The sailor uses body weight to sink the stern to get enough lift from the main foils to fly. And forward to reduce the lift when the boat is stonking along. Thus the rudder foils are relatively small as they need to be overpowered by the sailor’s weight to get the nose up and the main foils to a positive angle.

This implies a fair degree of clumsiness as opposed to the Moth systems. We didn’t see the A-class fly despite it being the boat with the second most water time.

Despite wading around he never found his missing foil.

New Kids on the Block – the Superfoilers

These are purpose built foiling boats made for racing during television breaks.

They promise to be very spectacular and hard to sail. So lots of drama for TV.

Designed by Morelli Melvin their scale is pretty interesting but to the people I was with they seemed very retro with symmetrical foils, no flaps, electronic controls for foil angle (when we see the instant feedback of the Moth systems work so well) – in effect an adaptation of the electronics of the America’s cup thinking of controlling centreboard angle, rather than the Moth way of actuating a flap on the rudder with a flick of the wrist. Battery failure will make the boats unsailable … but it is being sold as “technological advancement”.

In a way the Superfoilers reminded me of the Hobie trifoiler – updated and powered up more – a concept that is 30 years old.

Hobie Trifoiler as a point of comparison

Superfoiler – the longer outer hulls are purely to allow the feet of the three guys on trapeze somewhere to contact.

We didn’t see much foiling from the superfoilers, Moths were zipping around in the 10 to 17 knots on the harbour but despite two superfoilers on the water for quite a lot of time we didn’t  see any flying.

One of the problems the boat seems up against is sheer size, lack of manoeuvrability and potential speed. To get out through the moorings meant each boat had to be pushed out by a rubber ducky which stayed tied alongside until sails were set and crew felt comfortable.

Quite a long time – for events getting six boats on the water at one time – it will be a challenge, but the group seems well organised.

Foiling – another way of thinking

Ok … so that is what the mainstream is calling “the future of sailing”.

It is incredibly money intensive with the cheapest boat, the Waszp, being over $10,000. The engineering is worth it, in some ways it is an incredible price, but I end up wondering who is really going to go that way.

Moth 20K, A-Class catamaran 40K, Waszp 10+K

Ian Ward has a really interesting analysis that the heads on the speed crowd are actually looking in the wrong direction.

And that there might be a way of looking at foils that is relevant to the rest of us and for the real future of sailing.

There are foilers that are fun and easy to sail and don’t  need to cost so much, but you will have to wait for the second part :)

Part 2 next week!