Friday, June 9, 2017

RS Aero - No Speed Hum

Have you noticed that there is no speed hum with an Aero?





This is Peter Barton's reply to one of my recent questions about the RS Aero.  Peter looks after the RS Aero out of the UK, and usually manages to get back to me over night. There is a 10 hour time difference between Australia and the UK.  

This time I was following up an question posted in this blog from the Tijuana Taxi.

Great Blog Nick, well done on 2nd at the Nat's as well. One thing you didn't mention about the foils was the trailing edge, the designers have made this a mitre. When I first test sailed one I thought this had been filed to remove some dings, but on receiving my own boat the mitred edges were still present. I am pretty sure RS have not made mention of this in previous literature but my thoughts are by creating a laminar flow away from the rudder, cavitation is avoided and the boat steers even more effectively downwind than the Laser. I would be interested in your or anyone else's thoughts on this.

Hi Nick, Yes, that looked wrong to me initially too! I checked with Alex at RS who confirmed that the main reason is to stop/reduce the humming of the foils, it allows a cleaner re-attachment of flow, otherwise you get cavitation down the trailing edge which can cause the humming sound.
Peter Barton
Peter
Have you noticed that there is no speed hum with an Aero?











I tried to take a photo of the edge of my Aero centre boat, but my iPhone camera could not get it the edge in  focus, so here a shot of an Aero board next to an ageing Laser board.  Apart from having a clever trailing edge, they simply look so much nicer.  And there is no rattle or hum.




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Friday, May 26, 2017

Steve Cockerill joins the RS Aero class


RS Aero Class Facebook posted last week news that Steve and Sarah Cockerel have joined the RS Aero Class.

Steve has notched up some 50 odd singe handed championship titles over a variety of classes. 

Follow Aero news from around the world   facebook.com/groups/rsaeroclass/



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Friday, May 19, 2017

Laser vs Aero Roll Tack

The Laser block to block rig makes the boom very low and you really have to find a way to duck under the boom when tacking.  For many of us masters roll taking is out of the question, we just can't get under the boom in the correct way.  Here are two video with instructions on roll taking.  The RS Aero has much more room, so no excuses now.

Both videos slow the action down.





Sunday, May 14, 2017

The Laser's five basic design flaws

When you compare the 2013 designed RS Aero with the 1969 designed Laser it is easy now to see the Laser's five basic design flaws.

Three are due to the technology and materials limitations of the day, namely the Laser hull weight, the Laser hull shape and foils.

But why did designers, Bruce Kirby and Ian Bruce, chose a sail plan that required block to block sheeting at the transom?

Setting a low boom  also required a cockpit inset into the boat so low it cannot self drain. Centre sheeting and self draining cockpits were common in Moth designs in the 1960's and its hard to explain why the Laser ended up with such a poor configuration.


The Laser was unlucky to end up with a hull weight of 59kg as just 5 years later Ian Bruce and Frank Bethwaite produced the 68kg (fully rigged) Taser using Fiberglass sandwich foam. This substantially larger boat two person boat carries 11.5m2 sail and planes upwind.

In 2013 RS produced the Aero with a hull weight of 30kg

The Kirby's foresight was the was the unstayed mast that simply slotted into a hole in the deck. Comprised of two pieces aluminium tubing it made easy work of rigging, storage and transport. The approach now perfected further by the Aero and the WASZP.

Images:

1.  Bruce Kirby's doodle on a yellow legal pad. The tear sheet from this pad later became what we called the “million dollar doodle.”

2. 1960's Australian Moth with centre sheeting and self draining cockpit

3.  The WASZP with no stays, good when crashing at 20 knots


Read more about the history of the Laser design in Kirby's own words.
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Thursday, April 20, 2017

Laser vs Aero Rig

The RS Aero is easier to sail, faster upwind and more stable downwind than the Laser. It is not just the Aero's hull shape and light weight, the modern rig is simply superior.

The RS Aero has a distinctive squatter sail shape compared to Laser's tall pin head rig, or roached sail.

Read more about it in the tab above 'Square Top Rig' and the Tillerman's 'Fatheads and Pinheads' post.

The Aero's skinny and light carbon composite top section
 



























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Tuesday, April 4, 2017

Comparing Downwind Stability - Laser and RS Aero

The fear of capsizing in fresh winds and high seas takes the fun out of dinghy sailing and for club sailors limits the range of winds that we prepared to sail in. Even if we are not that competitive it is better to be going around the course in one piece than watching from the shore.

The Laser dinghy is notoriously unstable downwind in more than 15 knots and terrifying in 25. The death roll is the most common way to wipe out caused by gusts pushing too much sail in front of the mast.  It also happens when sailors loose their balance on an unstable hull.

Last week I competed in the RS Aero Australian Nationals at the Black Rock Yacht Club. The venue is renown for creating some of the best sailors in Australia due to the tough conditions on Port Philip Bay.  And it stayed in character all weekend with winds up to 20 knots kicking up big seas.

In a Laser I would have come back to the club after the first race and a number of out of control death rolls. But on my new RS Aero I managed to finish all six races and win two, made possible because I could choose to sail conservatively down wind, stay upright and finish.

Sitting back, flat and stable in 20 knots
It proved to me that he Aero is simply a far more stable platform in strong wind which I put down to these factors.

1. The Aero hull shape adds stability being wide and flat at the back of the boat.

2. The Aero rig can take more vang downwind than a Laser,  keeping the sail behind the mast.

3. The Aero rudder is deeper in the water and actually works to steer the boat, allowing more control to keep the boat under the rig.

4. Being light weight, the Aero gets up on a plane in the gusts, goes faster, reducing the apparent wind pressure on the rig. The extra speed also gives more stability.

With a second place in the Aero 7 Aus Nationals, the take away for me is I can sail now in 'fresh to frightening' conditions and I can work on being less conservative down wind with confidence in the stability of the boat.

Brian Close Australian National Champion pushing the limits, me ultra conservative

Aero v Laser - wide and flat, the Aero has stability down wind and a fast planning hull on reaches.

Saturday, March 25, 2017

Laser Dinghy And The One Design Dilemma

The dilemma for all sailing classes is how to stay relevant with new modern materials and design. One design classes are particularly caught in a bind.

This is ILCA Executive Secretary, Eric Faust explaining the International Laser Class Association policy.

“ILCA’s policy regarding the introduction of new equipment is that it should always have the same characteristics as the existing equipment and that the new equipment should not give a performance advantage when raced alongside existing equipment,”

In reality this is impossible to achieve. It is a pretence and indeed an absurd idea that one can use new materials and design and make them perform the same (as badly) as the old materials and design. One can only imagine the internal politics at the ILCA and the process to resolve this impossible situation and this is reflected in the time taken, around 10 years, for the ILCA to introduce a better full rig sail.


The old full rig sail was made from a 1970's cloth that distorted out of shape after one regatta and a dozen or so practice sessions. The sails short life span was made worse by contemporary super vang/cunningham techniques. So in the real world we have had a classic arms race. The one design principle gone with cashed up sailors gaining the advantage as only they could afford the necessary supply of new sails. 

With new sail cloth and new design, the new sail was always going to be better than the old sail. Straight out of the bag better, and as a more durable sail it was going to stay better for longer. So it was impossible for it to "have the same characteristics as the existing equipment and ..... not give a performance advantage when raced alongside existing equipment,”

Nonetheless the ILCA stuck to its policy. Clive Humphris, the ILCA Technical Officer.
"The main objective of the design project for the Mark II was to create a sail with equal performance to the existing sail, but with better durability. We worked very hard to ensure that the Mark II was not a faster sail and wouldn't make all the existing sails obsolete overnight.'

Notwithstanding their efforts to make a slower sail, the new MK II sail turned out to be noticeable better than the old sail, upwind faster and higher. Boats with the old sail were simply pinched off in the first 100 metres. At my Laser club, we all converted to the new sail within three months of its introduction. There was no point even using the old sail as a training sail, it felt and performed differently.

Single handed dinghy sailing is a close competition, loosing just a half a dozen boat lengths on the first beat can be the difference to being in to the leading group or the last group for the rest of the race. It would have been better for the ILCA to design the best MK II sail it could, because we were all going to buy it anyway.

The introduction of the composite carbon top section is a similar story. Years in development, delayed by internal ILCA politics and legal cases, the new top section has just become available. The old aluminium top section was ok in 1970 but it bent easily and broke after a few seasons. The new top section has again been designed to have the same characteristics as the old aluminium sections, but hopefully it won't break or bend. So for just for safety reasons alone everyone should buy one. Of course they are not really comparable because if they don't have permanent bends like the old one, if they are as stiff as the good aluminium sections, they are not, for most sailors, the same.

For me there was inevitable conclusion, observing the introduction of the new MK II sail and carbon top section, the process, the delays and design compromises. It simply demonstrated that the Laser would always be stuck in the past, there were too many issues to fix and even the simple ones would not be fixed properly. It was time to take the big leap solve all the design and materials issues in one hit and go to a new modern class. Laser dinghy farewell.

Monday, March 20, 2017

Death Roll Capsize, Moored Boats and a Broken Mast

Irony "a state of affairs or an event that seems deliberately contrary to what one expects and is often wryly amusing as a result."

Irony indeed. Two weeks ago I blogged some less than flattering comments about aluminium Laser spars being unreliable.  How the outdated design,  bimetallic corrosion and metal fatigue cause them to break after just a few years of use. 

You have to try harder to break an Aero mast and yesterday I achieved it. Had a great practice session in 15 to 20 knots, lots of tacks and jibes, working the waves, planing downwind in the gusts, even had a chance to pace the Australian Laser Sailing Squad who were training in the Sound for the 2020 Olympics.

Coming in back to club through the moorings I capsized backwards.  Traveling well on a broad reach, on semi plane and hit by an abnormal gust. In a flash the classic death roll capsize. Unfortunately over the shoulder there was a moored boat just a mast length away. Cue cracking sound of breaking composite carbon.

A sad and confusing moment swimming around after that capsize, finding the sail floating on the surface and the hull turtled.  

Fortunately Simon from The Life Aquatic has a spare (and an invoice) so back on the water the next day.  Just three more sails before the boat gets shipped to Melbourne for the Aero Nationals.

Wednesday, March 15, 2017

Laser and RS Aero decks

Aero self draining cockpit
The Aero and the Laser deck and cockpit are completely different experiences.  On the Laser you put your feet into a narrow cockpit and sit, knees up, as on a stool.

The Aero is flatter and more like a dish making the Aero  comfortable in light to moderate breeze. There is more room to move, its feels like lounging in a bean bag or sliding around the floor.

In light conditions the Laser is cramped, knees tucked, butt perched on the hard edge of the cockpit.

Hiking in strong winds the boats are similar, and while the Aero deck is nicely shaped, I still need hiking pads to make it comfortable.

Downwind, it has taken some time to get used to having to kneel on the Aero and I initially missed the seated position of the Laser.  As I gain experience the Aero kneeling position is becoming more familiar and allows a more active approach to downwind carving. Knee pads have made a difference.

Self draining cockpits like the Aero were a common feature of Moths in the 1960's when the Laser was invented and Moths also had centre sheeting.  This is a superior setup.

When the Laser designer chose the block to block sail plan, with a low boom it also required the lowest and smallest possible cockpit and venturi system to drain it.

The Aero's self draining cockpit simply does not fill up in waves.  In a Laser you have to shift back and heel the boat to stop water coming over the bow and filling the cockpit.  Ten litres of water in a Laser cockpit is very slow and slow to clear. 

The Aero in a strong breeze and waves can sail  flatter, have better fore and aft trim and use its fine bow to cut through waves. The occasional green wave over the bow passes out the back in a few seconds.


Laser cockpit needs a venturi to drain

Monday, March 13, 2017

Comparing Laser and Aero Foils

Aero Rudder
The first thing you notice when going from a Laser to an Aero is how responsive the boat is to the rudder and how light the rudder feels.

Upwind there is hardly any pressure on the tiller. Holding the tiller on a Laser upwind in a breeze puts real tension in the steering arm, there is significant weather helm, a big contributor to fore arm muscle strain.

Both boats need a lot of sheeting and this is hard on the sheeting arm. The Aero having a light helm gives one arm a break on each tack.

The Aero foils certainly look more efficient, the modern materials help and it is interesting to compare them.

The Laser rudder has a defined rake which is the cause the strong weather helm feel upwind. The Aero rudder is almost vertical.





Laser rudder



Both rudders probably have the same braking effect. When the two rudders are placed over each other they appear to have a similar surface area. The Aero rudder is longer and deeper in the water and has minimal rake which accounts for light weather helm feel.

The Aero rudder is very effective at steering while the Laser rudder lacks bite off the wind and down wind.

Downwind the Aero rudder actually works and the boat can be steered under rig adding to stability in 20+ knot runs.  The Aeros flat wide hull at the back also adds considerable stability.







Laser and Aero centre boards
Comparing the two centre boards, the Laser board seems to be a little larger, but not as deep in the water because it is raked back. The Aero centre board is deployed vertically and is skinnier and deeper.

On the water the Aero centre board is significantly better. There no vibration or humming when on plane, the board is properly fitted in its slot and does not ride up like the Laser board.


Aero rudder over Laser rudder
There is a trap to the Aero's more effective rudder and its light feel. Dinghy's are slowed by using the rudder, it acts as a brake.

Greater care has to be taken when using the rudder on the Aero,  it works so well to turn the boat it is tempting to over use it.  It is worth remembering Steve Cockerill's advice about using weight and sheeting to help steer.

Upwind on the in light/moderate breeze I hold the tiller extension as lightly as possible. This gives feedback to keep the boat flat just near the point where it is past flat and the balance changes to a lee helm.

The light hull weight means you have to scoot in and out a lot in puffy conditions. Fortunately the shape of the deck facilitates this, but more on this feature in future posts.


















Saturday, March 11, 2017

Mast Design and Materials

In the previous post we looked at how aluminium masts break and corrode.  This post examines how new carbon composite materials have allowed better approaches to the design of two piece masts.

Here is a Laser mast and an Aero mast. The 1970 aluminium technology has the top section sliding inside the bottom section with plastic sleeves to control the fit.  The plastic sleeves are attached with rivets. Top sections eventually break at the rivet and need to be replaced or "end to ended" each year.  The masts become bent in strong winds and when super vanged, especially radial masts.

The plastic sleeves have to be individually fitted, that is with sand paper, as new the extruded aluminium sections are all slightly different sizes and often do not fit at all. The weight and stiffness of the Laser top sections vary.  The heavier and stiffer sections bend less and are favoured by top sailors.  The lighter bendier masts are sold to inexperienced Laser sailors.

The Aero's composite carbon mast fits together perfectly and automatically aligns the sail track.  There is no variation in weight and stiffness, it is lighter and stronger and truely one design.

The stainless steel Laser fitting is riveted to the front of the mast with six rivets.  The Aero carbon composite goose neck is larger and  robust wrapping around the mast with no possibility of bimetallic corrosion.

Aero's robust carbon composite goose neck

















Tuesday, March 7, 2017

Outdated Aluminum Spars Break


broken spars pile up in Laser clubs
Sydney recently experienced one of its frequent weather events an east coast low pressure system, throwing 20 gusting 30 knots at the harbour.  Of the 20 Lasers that ventured out that day on Middle Harbour, two were towed home with broken bottom sections.

This is typical for club sailors. Spars become unreliable after about three years depending on use.  The elite sailors replace their spars, indeed their boats every year which club sailors cannot afford to.

The problem has been exacerbated by the modern approach to Laser racing in strong winds.  The story goes that on his way to the top, Tom Slingsby obtained funding for a stack of sails and decided to test their limits by super tensioning the cunningham and vang in strong winds. It worked well, the boat became more manageable and the technique became standard practice.




typical corrosion at a stress point



Unfortunately the 1970's designed aluminium sections are not up to the task and with the increased stresses they break.  Only recently has a carbon top section been introduced but the class is still stuck with outdated aluminium bottom sections and booms.

Metal fatigue is not the only problem.  Laser spars corrode, especially in salt water.  There are two kinds of metal are in contact with the aluminium in the form of the rivets and the fittings.  New bottom sections and booms start to show signs of bimetallic corrosion within months of purchase with tell tale corrosion grooves fanning out from stress points.

The super vang approach is also tough on other fittings which are now not reliable either.  Vang tangs break as does the bolt holding the goose neck.

The Laser class seems unable to adapt to these problems. It is not only a cost issue, it puts extra responsibility on club race management and makes the boat unsafe in strong winds.