How to Design a modern Yacht

So if I have understood it correctly, Carlos, your light surf board is a MiniTransat ...

A MiniTransat with very good passive safety and not the delirious madness of 70 cm of freeboard and 3 meters of beam, a comfortable interior for a grumpy old man, a comfortable and versatile rig, a seat with great backrest worthy of this convertible sports car for an old fogey, without having to leave the cockpit at all, and nothing is nothing and not like in the advertising brochures, and you can take the rudders out of the water to hove-to like a Falmouth Quay Punt ... or lower the reefed mainsail and hold head to the waves with a sea anchor like an ocean rowing boat ... and also perch on the sand like a catamaran

E x a c t l y

 

I am confused. Are you calling that mid-displacement boat a surfboard?

 

The idea of having a fine/low drag entry at low/medium S/L ratios while still having high buoyancy in the bow when being driven hard in higher sea-states was appreciated by clipper ship designers, (and many of the designs by Alden and Garden,) the result being the hollow sectioned "clipper" bow, as it picks-up buoyancy at a greater rate as it goes down in the water.
As the speed reaches high S/L ratios the hollow of the wave formation moves aft, and the boat actually starts losing buoyancy in its stern sections, so it starts to settle.
Thru the speed range the position of the CB changes, designers accommodate that by giving the hull more fullness aft.
They tried the old "Cods head, Mackerel tail", (like a low-speed airfoil where maximum chord is only about 1/3 the way aft in the wing section,) but quickly learned that wasn't the way to go.
In all fairness though, the original idea was to place the point of maximum buoyancy where the cargo hold was.
I'm still wondering what your summation might be of what's now three pages of what seems to be mixed-up comparisons between a displacement hull and one that, (given enough wind,) can surf.
To surf, a boat must have the ability to leave its quarter-wave astern.

 

Why do you claim that the Satanita/Valkyrie collision had anything to do with pitch and yaw control? Jay, the professional skipper, and the helmsman at the time of the collision both gave evidence in court that Satanita was NOT out of control and was NOT failing to answer her helm.

At the time of the collision there was only one man on the helm of the 131ft (93'6 waterline!) 126 ton yacht that was reaching at high speed, and yet he was able to alter her course without calling for assistance from the two men standing by ready to help.

The Satanita case went to the UK's highest court, so the evidence from the people on board that the boat was NOT suffering from a yaw problem was clear and accepted at the highest level.

It must also be said that Satinita was not only the longest racing cutter ever built, but for her era she had an unusually long keel. The behaviour of a 131'ft 126 ton gaff cutter of that style is not relevant to modern boats.

Finally, you are being utterly inconsistent when you insult others for relying on "bar talk and superstition" when you bring up an 1893 collision and yet reject first-hand personal evidence with the sort of hull shape you are promoting.

 

That pic shows one of the great problems with a dead flat bow section. When a boat heels like the Mini 6.50 is doing in the photo, the effective deadrise in the bow section changes dramatically and the dynamic lift drops, allowing the boat to sink. The Minis have more circular sections forward to prevent this happening.

The funny thing is that Carlos has apparently never owned or sailed a wedge-shaped boat with very flat bow sections or a windsurfer so he is theorising from ignorance, and yet he insults people who have owned and sailed such boats as relying on "bar talk and superstition".

I don't think Carlos is actually going to find out the problems with this sort of design because he is like quite a few other people who have come on this forum, blinded by ego and abusing other designers and sailors with actual experience, made big claims about what they are going to do, and then never ended up with anything more concrete than doodles.

 

Its clear you do not like his, shall we say, his market hypothesis; but do you dispute the math?

Can you show where his numbers fail, that leads his conclusions to be nothing more than speculation?

 

And by you too.
Since you have no idea what the Munk moment is, since it only applies to fully submerged shapes.
A yacht is not a fully submerged shape!

 

1- I know my limitations, and one of them is that I'm not great at maths. My mathematical limitations are offset to some extent by extensive actual research into design history - not "superstition and bar talk" that Carlos falsely claimed, but actual sailing and actual correspondence and interviews with many leading NAs and small craft designers - the sort of people that Carlos dishonestly and arrogantly abuses.

The dishonesty of Carlos' insults is highlighted by the fact that he refers to Frank Bethwaite's SCP. I knew Frank for about 35 years, interviewed him on the record and informally, and he was a person who was aware of the issues of the extreme wedge shape that Carlos proposes. He also admitted that the SCP was a very rough comparison that could, for obvious reasons, be extremely misleading.

2- I often start from a different proposition - is someone reliably truthful and reasonable? If we apply that test to Carlos, we find that his claims are so often wildly inaccurate that scepticism is the logically correct approach to his statements.

Someone who states as a fact ("an iron law") that boats like this;


are "imitating" boats like this;


is clearly someone who cannot be assumed to have a good and truthful grasp of the reality of boat design.

2 - The maths Carlos shows appear to be very simplistic and incomplete and are therefore unable to prove the claims, especially when the claims have so often been proven to be wrong in real life. NAs I've interviewed who deal with CFD programmes that use super-computers (not laptops) for America's Cup designs tell me that modelling motion in planing hulls is extraordinarily difficult, so I don't believe that extremely basic mathematics can be used to "prove" something that reality shows to be untrue.

Ship motion in following waves is extremely complex, as we all know and as is shown by one of many pages of formulae in this old paper on the subject;



Carlos shows no evidence that he has gone to the lengths in that one page of that paper, so his claims are unproven. As an example, I cannot find the mathematics showing the amount of the claimed dynamic lift on Carlos' bow sections, nor what happens to that claimed dynamic lift when the boat heels 25-30 degrees as often occurs (as shown in his own pic of a Mini). Nor does Carlos shown the mathematics behind the yaw moment created by the extreme wedge shape and very hard chines when the topsides are immersed when the boat rolls at high speed. What we are being shown is simplistic and incomplete mathematical models of a few parts of an extremely complex pair of objects in an extremely dynamic situation.

 

Not only that, he claims that it reached speeds higher than the world's fastest maxis of almost the same design era seem to have!

The Baroudeur is in French rating class 2 or 4 of the OSIRIS empirical handicap system, depending on the version. The rating confirms that it is a very slow boat which is apparent from the fact that it's 2.3 tons and only 22ft overall. The claim that this proven slow 22 footer could surf at 20 knots is an extraordinary one and yet Carlos has provided zero real evidence. His "evidence" seems to be that the owner is supposedly respected - but Carlos abuses and insults many other respected sailors so it's utterly hypocritical and dishonest of him to claim that we must accept alleged evidence provided by someone merely because he is allegedly respected.

 

Well, im here to learn and most of those equations i see are a different language to me, so i am in no place to dispute them.

With regards to production boats taking after racing boats, im assuming the mass produced yachts of the 70s early 80s of IOR influence and the marine trades observation after the 79 Fastnet, i cant go back to the 1800s.

Some big fat wide sterned boats with twin aft cabins handle better than some, but many skippers i spoke to do mention the problem you refer too in extremes about the wedge issue; but again, Pogo and others still build them like that. Not all boats that "look" the same handle the same.

I think there was a video of that Barouder with a GPS overlay. I have done in excess of 20 knots in a displacement boat of 21ft WL, but only down very large steep waves, I cant say i enjoyed finding myself going 5 times as fast as normal. Driving at 50kmph seems slow, how would most people react to suddenly find themselves doing 200kmph!

Anyhoo, everyone can have an opinion, personally i would like to see his old fogey surfboard boat come to life, it may, or not, perform as he expects. I am not in a position to vigorously defend others work that i know nothing about.

 

Like you I'm here to learn, often by checking on claims made by others that don't ring true.

Yep, as you say boats that look generally the same can behave very differently, and a shape that works well on a fast boat like a Pogo can lead to nosediving and control issues on a slower boat which is proportionately heavier and lacks the same amount of dynamic lift forward.

Speed claims are very hard to confirm unless one is using well calibrated instruments. GPS speed readings are well known to have huge errors, which is why GPS speed windsurfing competition rules only permit certain units and require the traces to be available for analysis.

Much of the same applies to logs, which can also be very inaccurate at surfing speed when the flow gets turbulent. Reports of extremely high speeds gained by very slow boats are arguably just as reliable as the report of 0.00m depth my depth sounder gives when surfing. When we're doing Sydney-Hobarts etc on 30 footers that are dramatically faster than the Baroudeur we are not exactly hanging around or sailing flat water and yet we don't get 20 knots (although perhaps the Mumm 30 etc did).

The French Baroudeur handicap gives it an average speed of 3.88 knots compared to say a J/24 with 4.78kt. As noted, this makes the Baroudeur a slow boat by just about any standards. The Farr 40 has an average speed of 6.69 knots, and cross reference shows that these average speeds conform to ORC ratings. ORC says Class 40s average about 7.2 knots. They allegedly hit 28 knots and their fully crewed 24 hr record is at just over 18 knots.

So the Baroudeur is about half as fast as a Class 40 or Farr 40. Why, then, would a Baroudeur sailed singlehanded and under small sails have a top speed more tha 2/3 as quick as that of a Farr 40 or Class 40 driven hard under spinnaker by pro crews trying to win major ocean races? Why would the 22ft Baroudeur running singlehanded be dramatically faster than a 39ft boat that has been British Offshore Yacht of the Year multiple times, won its class 11 times in the Fastnet, once in the Hobart and taken out NZ's biggest race overall? Why would a particularly slow 22 footer from 1970 be able to go about as fast when cruising as the top foiling Mini 6.50s go when driven to their utmost when racing?

Here's another way to look at it - if a Baroudeur could hit 20 knots it would be going at 3.3 times hull speed. If heavy displacement hulls could do that then clippers and the schooner Atlantic would have done about 60 knots when driven to their limit fully crewed, and in a later era 12 Metres and the heavyweight maxis of the '60s would have hit over 30 knots and therefore have been able to come close to a foiling Open 60. Psshaw!

As is said, everyone has the right to an opinion but no one has the right to change facts. I'd also add that if people insult others as Carlos does so widely then it's hypocritical to object to getting insults in return. I don't know much about him but that he's an old apparently single guy with no cash. There's nothing wrong with that but it does show that he's essentially not very successful and maybe he should be more respectful of those designers and sailors who have achieved and succeeded far more than he has.

 

I took it for granted that the speeds he is quoting are in "bursts" and not consistent. You have the boat going into a surf, on a wave that itself is travelling at speed. It will be higher on a GPS across the ground speed, than the boats impellor log. Much the same as a plane doing 500 knots in a 200knot jetstream will be doing 700nm across the ground, even if the airspeed indicator is less.

Wave energy has a higher (literally) impact on smaller tonnage boats than the larger ones you mention, what literally will pick up a small boat will not have the same energy to do so on bigger vessels.

At least, that is the impression i believe he is pointing at, of which I can agree, having experienced it myself, which might account for a distance 5 nm of white knuckle ride, in 10,000nm sailed.

 

But the air particles in a jetstream move whereas the water particles within waves themselves move slowly and not at the speed of the wave, so logs that measure speed by acting against those particles aren't always inaccurate. My point is that they can be very inaccurate and calibration at extreme speeds is very difficult, so claims about speeds on logs can be taken with a lot of salt. As the saying goes, extraordinary claims need extraordinary proof, and claiming 20 knots in a slow 22 footer is certainly extraordinary.

The video with GPS speeds shown is a Dragon, not a Baroudeur. The Dragon is a much faster boat but it's getting much lower speeds than 20kt, and the GPS track has not been downloaded to check for spikes. As noted, there is a very strong world GPS speedsailing community in windsurfers who are extremely aware of the GPS spike speed issue and they only permit certain GPS units to be used (I think it's a measure of sampling rate or something) and then they require speed traces to be tracked for spikes that show misleading speed. This is standard practise in speedsailing because everyone knows how misleading GPSs can be.

Yes I also assume he's talking bursts, but when this subject came up I went to my bookshelf and to on-line sources and read accounts of boats like Stormvogel and Kialoa II (ie the same design style as the Baroudeur) to back up the reading (and sailing) I've done on older racing yachts. They talk of surfing speed, not just speed over long distances - but it's surfing speeds of low 20s at most even when driving hard under spinnaker in major races. And yet these older big boats were still far quicker than small yachts downwind in a breeze, as proven by the results of downwind races.

When a world-girdling top-class racing 73 footer of the late '60s can only do about 20 knots driven hard under spinnaker by a full crew, there is no way that a tubby 22 footer of the same era is going to go the same speed singlehanded under small sails.

I prefer small boats and have done three Hobarts in 30 footers (once on a heavy boat, once on a light IOR boat, and once on a lighter IMS boat) and won two national titles in the under-30 foot offshore racing class as well as sailing overnight offshore races on boats as small as a 20' baby version of the J/24. And that experience indicates that Carlos' claims that heavy boats surf faster is just silly - their hydrodynamic drag increases so much at high speed that they surf less often and more slowly. This is pretty much universally known to anyone who has raced light boats against heavy ones. I've also raced aboard and against one of the world's most successful heavyweights of recent decades - multiple UK Yacht of the Year winner, class winner in the Fastnet and Hobart, overall winner of NZ's biggest race, etc - and discussed her performance against lightweights with the owners on the record. This outstanding 38 footer had no chance downwind in surfing conditions against much smaller lightweights; we were against her in the 30ft IMS boat and just surfed away from her.

 

I completely agree about inaccurate log recordings. But if you are surfing on a wave that itself is doing 25-30 kts, then SOG by gps will be high.

For sure im not suggesting a Baroudeur will beat a fully crewed 73ft maxi of the same era, but then how can such boats be beaten by a smaller RCOD or Black Soo type, if not for the ability to take advantage of wave action that the larger boat can not use/effected by, in the same way?

 

I have sailed boats of the Black Soo type. They do not beat a 73 ft maxi, regardless of waves. Do you have evidence of any race they have one in real time? Otherwise, check the PHRF ratings. They are based on average of boat finishing times.