Project: Canting keel for cruising yachts

And the price is…well…


Thank you rwatson, Joseph T and trip the light fandango for your answers! Also, thanks to Doug Lord for your earlier fantastic feedback.


For the time being, we did not find out an accurate price for a canting-keel cruising yacht, but a definite maybe!


Here are my next set of comments. Read, enjoy and comment freely. We enjoy reading your feedback! For the purposes of our conversation, EUR 1= USD 1.17.


In a nutshell, here are the best advantages of a canting keel for cruising purposes – and for which we still would like to find out the price for.


· Keel torque in the best racing-boat class

· Deckhouse solves the flat-stability-curve problem, among other issues

· Reasonable docking draft of 2 m (6’ 7 “ft)

· Less diesel fumes to inhale while sailing


Even though we only received one actual reply (thank you Joseph T!!!), this was an interesting exercise. Thank you also to everyone who bothered to read our posting.


Since I am the author of my own post, I now exercise the right to enter my own opinion on the matter:


For question 1, I believe the price could be EUR 315 000 and here’s why. The Elan E5 price is maybe EUR 265 000, with the most popular options included. But, there are guys and gals who would pay an extra EUR 50 000 for a sailboat that performs significantly better, in a more upright position and with more room to live in. Considering that a better performance pack to the Elan E5 costs EUR 8 660, a high-performance fixed keel costs an additional EUR 8 200 and a teak pack costs EUR 12 990, I believe that an extra EUR 50 000 is not excessive for a top-of-the-line canting keel.


For question 2, my answer is EUR 330 000 and here’s why. If you don’t have to worry about running down your batteries while sailing or must fire up the diesel engine and be breathing in and smelling like diesel fumes, the sailing experience is simply more pleasurable and involves more actual sailing than fooling with auxiliary equipment.


I conclude that sailors do exist that are ready to pay an extra EUR 50 000 + 15 000 for a sailboat equipped with a cutting-edge canting keel and not have to be inhaling diesel fumes while sailing.


So, if the extra price that a canting-keel cruising-yacht is EUR 65 000 that some people would be willing to pay for, the next question is, is it possible to build them profitably?


Building a fixed keel is not free either. Let’s assume that the keel portion of the overall price of A 40-ft sailboat would be EUR 20 000. In that case the amount of funds available to invest in a canting keel and the necessary gear and fins, while designing and building it is EUR 65 000 + 20 000 = 85 000.


In any case, the obstacle for installing canting keel to cruising boats economically has been overcome in the last 15 years. When I built the first canting-keel prototype, a boat with a sandwich-structure deck and hull were rare and much too expensive for the common sailor. The basic structures were also way too heavy to sail them into a semi-planing speed ranges, so to accommodate a canting keel, a new hull would have been necessary to design and build and the building costs would have skyrocketed. Fast forward to today and almost all new sailboats have a sandwich structure, at least in the performance-grade boats. The sandwich-structure building technology is the order of today, as even motor-sailors such as the Hallberg-Rassy have it.


EUR 85 000 extra for just the keel? That is a lot of money indeed. Whether it is enough to cover the building costs and make a profit too depends on one thing only: the boat building volume. If a boatyard builds 500 boats with canting keels, it is for sure profitable. If the number is 5, one cannot really consider it a viable business activity. But, 100 boats would generate a turnover (or revenues for you Americans) of EUR 8,5 million. With that kind of money, one has the resources to design and build a bit more sophisticated gear.


An important factor to consider in boat building are the design costs. Car manufactures spend hundreds, if not billions of euros in the design only, of just one car model! It is profitable, as the manufacturer will be selling millions of cars. Such volume is not anywhere near possible in the sailboat industry. Simplicity is the key. No sailboat builder has a staff of 50-100 design engineers solving problems for months on end, for which a solution may not exist after all.


There is still time to answer the questions, if you are interested. You will find them earlier in the thread.


Enjoy the sunshine!


Best regards,


SubForce Keel

 

Sub Force, you claim "a canting -keel boat is intended to sail at semi-planing or even at full-planing speeds and that being the case, entirely different hydrodynamic laws are in operation affecting the hydrodynamic drag."

What evidence do you have for that? In terms of all-round speed, ORCi indicates a speed/length ratio of 1.19 for an Open 60 and 1.14 for a TP52. To claim that such a small difference in S/L ratio means that "entirely different hydrodynamic laws are in operation" appears to be a great stretch. Showing a pic of an Open 60 reaching isn't evidence - for one, Open 60s sailed very fast on a reach even before they had canting keels. Secondly, TP52s etc can sail very fast on a reach too, although not as fast. Yes, Open 60s are different to the C50 type - but they always have been and that is because they are intended for a different race under different rules, not simply because they are canters. A TP52 regularly sails at planing speed, and yet they do not have not beamy flat Open 60 style hulls.

Yes, the optimum shape of a hull is affected by its intended speed - but no small production cruising boat is going anything like the speed of an Open 60. The Open style hull is effective when built extremely light and driven hard along reaching or downwind courses under huge rigs by pro sailors. Those factors do not apply to cruisers.

The Schock 40, the only "production" canter of the size you're looking at, has a S/L ratio of about 1.08, and that's in a boat that weighed just 3175kg and had a low-drag outboard engine. How are you going to get anything like that S/L ratio from a boat two and a half times the displacement, let alone a S/L ratio that would get in the region of an Open 60? There has already been a 60 foot "cruising canter" afloat for 21 years. Despite having a spartan interior, a flush deck, carbon fibre hull and a wing mast, on ORC it is actually rated slower than a TP52 and much slower than an Open 60; in fact it's only 1.0043% faster than the fixed keel Cookson 50s you said could not be compared to a 60 ft canter!

The Open style hull comes with its own problems. They are famously tough to sail upwind, and apparently slam very badly in chop at all angles. While you discount the light-air issue, their comparatively high wetted surface will demand that their owners motor more in a comparable passage, all else being equal.

May I also say that you make a lot about the fact that cruising sailors will often motor in light winds, yet you appear to ignore the fact that high speed when reaching comes with its own set of compromises. It would seem likely that very few cruisers actually really want to plane across the ocean, with all the extra wave impact, motion and spray it involves.

Finally, to look at the cost simply of the canting keel ignores the fact that higher righting moment will increase the loads on the rigging, on the sails, on the winches, on the halyards, etc. The higher reaching speeds are also likely to increase hull stress and strains. To upsize all of those components costs a great deal.

By the way, I've been lucky enough to interview most of the world's best designers of racing skiffs, who have confirmed that moving the LCG aft comes with its own large set of handling and hydrodynamics problems - so large that modern skiffs have their LCG considerably further forward than Australian skiffs of a couple of decades ago.

PS - why did you say "we only received one actual reply"? You've had a couple of pages of replies.

 

JP54-canting keel cruising boat by Guillaume Verdier and team:

 

• Dibley 40 canting keel cruising yacht: Dibley 40 Canting Keel Cruising Yacht, Dibley Marine Design http://www.dibleymarine.com/sail/sail/dibley38.html

 

Speed/Length ratio-definition from Eric Sponberg:
Definition: Speed-length ratio is the speed of the vessel in knots divided by the square root of the vessel’s waterline length in feet = V/Lwl^0.5. At speed-length ratios less than 1.34, the vessel is in displacement-mode motion—that is, the hull is simply moving the water out of the way as it moves forward. When speed-length ratio is between 1.34 and 2.5, the vessel is in the semi-displacement or semi-planing mode—that is, it is trying to rise up over its own bow wave to get onto plane. Some boats are designed to operate at these speeds. Above speed-length ratio of 2.0 to 2.5, the vessel is planing and relies on dynamic lift to raise and hold it out of the water so that it can skim along the surface of the sea.

 

The JP54 looks like a nice boat (EDIT - it had better be, given the amazingly high price). It was beaten across the line in the 2012 ARC by a Pogo 50 (not a canter), by a canting Cookson 50 in the Fastnet, and in events like the Belle Ile by a TP52. That's a great performance for cruiser, but the JP54 is a carbon boat in which "each kilo on board has been analysed to ensure only critical weight is added". It has just one head, no interior liner, only three winches, etc. It does have a swivelling pod that moves the 700kg of batteries to windward.

This is the JP54 interior;





It's vastly more spartan than a normal cruiser, although perhaps roomier than many. To me it doesn't even look like standing headroom ahead of the mast. If you add a normal cruising interior (heavier, with inferior fore-and-aft weight distribution and without the canting interior pod) the boat will be significantly slower. And Sub is talking about a boat with a lot of interior volume, so the fitout would weigh more than an Elan unless one wants to throw huge amounts of money at it.

Another major difference is the price. The JP54 cost $2 million Euros, without sails - four times the price of a Pogo 50 and twice the price of a ClubSwan 50! (EDIT - that means it's in the same price range as a Pac52 or TP52). SubForce reckons he can build his canter for 330,000 Euros so it's not going to anything like as light and exotic as a JP54. (EDIT - it appears to be more evidence that canters are normally more expensive than fixed keelers in terms of knot per dollar).

If a 54ft ultralight ultra-expensive carbon canting cruiser is beaten by TP52s, Pogos and Cooksons then a smaller, heavier and dramatically cheaper boat is not going to get anywhere close to the claimed performance. It's not going to blaze around like an Open 60.

 

Interesting debate on that option…. As I have developed recently a numerical boat, the DB32 inspired by a Melges 32 , and a dedicated VPP for the Dynamic Ballast study (details in Dynamic ballast https://www.boatdesign.net/threads/dynamic-ballast.59729/ ), I used it to investigate the canting keel issue to try highlighting some orders of magnitudes and understandings, the resulting curves are given here attached.

Main facts and figures :

1. Determination of the RM when canting the keel at 45° windward, that gives a new RM curve introduce in the VPP . For RM30°, that gives + 24% , so do the extra strengths on the rig and the hull concerned structures.

2. Comparison upwind and downwind with same sail surface
For the VPP, in addition to the new RM curve, we just add the wetted surface of an extra daggerboard needed to provide the leeway resistance that the keel at 45° no longer can provide efficiently : a daggerboard surface estimated at 80% of the keel wing for upwind sailing, 1/3 of this daggerboard for downwind conditions.
VPP upwind conditions includes waves and a Raw estimated to 8% of the cam water drag (a low-medium figure a priori).
No added waves resistance taken into account for the downwind conditions.
>>> Upwind, the speed advantage really starts for a wind of 8 Knots, of about 10% to 15% + the ability to sustain the top speed for 2 more wind knots before the first reefing (i.e. before reaching 30° heel). Below 8 Knots of wind, it is better to keep the keel at 0°, and even a bit negative (leeward side) in very light winds to reduce the overall wetted surface and help sails to keep a good shape. The gain in heel is mostly in the 20° to 30° heel range, for wind > 11 Knots. Below 8 Knots of wind, it is better to keep the keel at 0° anyway.
>>> Downwind, the speed advantage really starts for a wind of 12 Knots, up to +18% for wind 18 Knots + the ability to sustain the top speed for 4 more wind knots (up to 22) before the first reefing. Below 12 Knots of wind, it is better to keep the keel at 0°.

3. Comparison upwind and downwind, with a 118% sail surface for the canting keel configuration

In the VPP, the heeling arm is also increased accordingly (Zsail is increased by 1,18^0,5).

>>> Upwind, the speed advantage is noticeable only in light winds, about +8% for wind speed < 8 knots. For stronger winds, the extra sail surface does not give more top speed, due to the extra heeling arm and drag due to more heel. Actually, the speed curve shifts to the left, demonstrating that for light winds the propulsion key parameter is the sail surface while for strong winds the propulsion key parameter is the RM.
>>> Downwind, same comment as for upwind : more sail surface has the effect to schift the speed curve towards the light winds without giving more top speed for strong winds.

By hoping these orders of magnitude can be helpful ......, keeping in mind that DB32 is more a sport boat than a cruising boat, and that the VPP cannot take into account some potential dynamic surf capacities when downwind with strong winds.

 

Interesting information, thanks.

The very light Melges-style hull would surely benefit much more than a heavy medium cost cruiser/racer like the one the OP was discussing, wouldn't it?

On ORC the canting Cookson 50 is less than one knot faster than the non-canters, apart from one wind angle and speed; I think the canter is 11% quicker at most.

 

More on speed differentials…and rig stresses

Dolfiman, thank you very much for your trouble and thoughtful answers. It looks like to me that your results are very much in line with ours. The graphic display of the reefing effect was great! Special thanks to you for that.

According to our VPP-analysis, the speed of the ILC 30-type boat does not increase much with a canting keel. On the other hand, Dolfiman’s calculations show that a canting keel has a noticeable effect on a boat similar to the Melges 30. The differential between our results and Dolfiman’s makes sense, knowing that the Melges 30 was designed for a significantly higher speed range than the ILC 30-type boats. If one wishes to achieve significantly higher speeds a canting keel, the boat hull shape must be designed for a higher speed range to begin with.

We claim a speed increase of 10-25 %, with sufficient and conducive wind conditions, whereas Dolfiman’s results show a 10-18 % increase. One explanation for the difference is that we compared a fixed-keel boat with keel-fin draft of 1.7 m to a canting-keel boat with keel fin draft of 2.6 m. Our comparison basis is justified, because we wanted to specifically compare a fixed-keel boat performance to a canting-keel boat, with design specs similar to our canting keel. Both boats have, however, a similar docking draft despite the draft differential under sail.

Another factor that can explain the speed differential is that in Dolfiman’s calculations the comparison boats have a same size keel. In our case, we decreased the keel weight by 200 kg or 20 % (the net decrease is 200 kg, with the weight increase from the hydraulic cylinders considered). Canting-keel boats seem to normally have a significantly lighter keel when compared to a fixed-keel boat of the same size. Possibly the starting point in determining the weight of a canting-keel is to maintain a sufficient righting moment to prevent capsizing and not so much the righting moment to increase performance. There’s plenty of righting moment in a canting-keel boat and so it can also be lighter. Weight kills speed; the lighter the boat the faster it is, in general. These are my assumptions for determining the keel weight.

One more thing we must consider: The rig specifications. On Dolfiman’s calculations, during a 30-degree heel the rig is under 25 % higher stress if the boat has a canting keel. Also, CT249 brought up the fact that a canting-keel boat must have a stronger rig.

Stress-increasing factors on the rig of a canting-keel boat:

· Canting angle

· Wider and more stable hull

Stress-decreasing factors on the rig of a canting-keel boat:

· If we succeed in building a boat according to our plans, I assume that the sailing weight will be minimally 10-20 % less than on a similar-size fixed-keel boat. The keel will be lighter, non-essential equipment will be less and the hull and deck structures will be lighter. The boat will not have a teak deck, elaborate teak interior, two heads and so on. Instead, the skipper will have to settle for eating his dinner off plastic plates and not nautical-themed porcelain and rinse his mouth from a plastic cup and not Czech lead-crystal goblet.

· When designing the deck structure, the requirement for 5-10 crew members to hang off the side of the boat is no longer needed. Neither is the 5-10 men crew and the accompanying weight.

· With a lighter boat and keel, the stability curve of a canter is lower and flatter than that of a fixed-keel boat. RM30 is the starting point for determining the rig specifications, just as Dolfiman has done. With higher heeling angles and higher accompanying stresses, the rig stress differential between a canting-keel and a fixed keel boat decreases and at some point, it does a reverse. It may be, that ultimately the rig on a fixed-keel boat is under higher stress in extreme situations than that of a canting-keel boat.


Your thoughts?

Happy sailing!

SubForce Keel

 

Have you also think about the pin axis inclination ? , it is important to put some degrees to avoid negative leeway resistance but it is a delicate trade off depending of the performance you privilege, as it is well described in this document, "Farr Yacht Design’s Alon Finkelstein looks in detail at VO65 appendage design", found out by Doug Lord :
Leading edge - Seahorse Magazine https://www.seahorsemagazine.com/24-content/august-2013/134-leading-edge

 

Hello Dolfiman,

Thank you very much for taking the time to bring attention to the pin-axis-inclination issue. It really is a significant factor in the keel design and will improve our keel more than you will ever believe. Since June of 2018, this has been a central factor in our design and product-development process.

If we succeed at getting a sailboat built with our keel, we would be honored to have you come and test-sail it with us.

Thanks again.

The SubForce Keel crew

 

Thanks for your kind message and invitation, have you now some kind of public brochure that can give us an insight of your concept ?

 

Unfortunately we do not have anything published yet. I will let you know immediately when we do.

 

Well since I am looking for info in another thread I will give you some feedback.
Boat will cost at least double to build compared to a standard off the shelf cruising boat.
Canting keel will be more comfortable and the boat will sail flatter up wind. (However who wants to cruise upwind)
Hydro power system costs a lot and still does not work.
Canting keel will be faster in cruising mode. The reason the cookson comparison is not that valid is it is a racing yacht and sailed at 20 degees heel upwind, with everyone on the rail which creates the righting moment required to go fast.
You would be way better to spend the money on a bigger heavier cruiser with plenty of form stability like a pogo 50.
Mono hulls like weight when going upwind, and it makes them way more comfortable in a seaway.