The Offshore Voyaging Reference Site

How Weight Affects Boat Performance and Motion Comfort

One of my first transits of the Cape Cod Canal in Massachusetts ended in an eye-opening experience when our small cruising boat was almost stopped by 2- to 4-foot wind-over-tide chop while exiting the west end into Buzzards Bay.

It wasn’t until years later that I realized why we had pitched so uncontrollably in such otherwise tame conditions:

Although the boat design wasn’t known for pitching, several adults in the cockpit made her very stern heavy, plus several modifications by the owner had greatly increased the pitch moment of inertia. Together, the improperly-distributed mass resulted in the boat pitching horribly.

Mass (weight¹), how much, and its location, affects the performance of all boats.  

The goal of this article is to help you think about where and how you add or remove mass from your boat so you can improve performance without resorting to racer extremes.  

¹Us lay people can for our purposes here, think of weight and mass as the same, although actually they are not. Eds.

We will examine mass, the moment due to the position of the mass, and finally the moment of inertia, which can all be additive to each other.

Mass (Weight) Alone

Let’s start by pretending that we add mass to the boat and can ignore where for now. This results in three important effects:

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Colin Speedie

Great article, Eric.

This puts a lot of numbers to what I have mentioned in my posts so far, regarding reducing weight and taking care with its distribution. Our She 36 is of the same era and style as your CS36 and I’m sure yours is as sensitive as ours to weight and its distribution.

Two things. The first is that while a larger boat (with the same number of crew) will swallow the same amount of cruising gear with less performance penalty, that advantage can soon be lost with scaling everything up and adding complexity.

The second being the addition of kit like wind vane self steering gears and heavy duty anchors, left in place all the time. It helps to be able to remove a vane gear (they’re heavy!) when coastal cruising and removing an anchor when facing a long passage. An anchor (e.g. Spade) that can be disassembled and stowed low in the boat is a big plus here.

The current tendency to add endless amount of gear on the transom can’t help performance – thanks for pointing that out.

Arne Mogstad

Maybe this have been discussed elsewhere, but I wonder about the safety of removing the anchor. Of course it will be of little use in the middle of the Atlantic, but you’ll reach shore again, and if you’re faced with having to reassemble it on the bow in heavy conditions….? Is this a normal practice? Do people put the lighter secondary anchor up in the meanwhile?

John Harries

Hi Arne,

I think that depends a lot on the size of the gear. On a small boat I can perhaps see removing the anchor, but, for example, on our McCurdy and Rhodes 56 I went to a lot of trouble to have a safe set up to leave the anchor on the bow at all times. Bottom line, I don’t like making a landfall without an anchor ready to go on the bow. I learned this the hard way on my Fastnet 45 when we made landfall in a Force 7 and had to get the anchor back on the bow in very stressful conditions.

Botton line, if trying to move weight off the bow I would look at lighter chain or moving it aft.

Arne Mogstad

This seems to align perfectly with my “fear” too. I think I’ll just not do that. All the potential disasters (carrying a heavy anchor on a moving foredeck, losing the anchor, losing the shackle/pin, damaging the hull with a heavy and pointy anchor….). Too much risk for somewhat limited reward as a non-racer.

Ola Svensson

Hi Eric .
we have done a version of this. To be able to have 350 ft of chain on our 35 feet Linjett without gettin to much of a penalty from exessive piching ,We have a pipe going from the anchor locker to the bilge in top of the keel.
There we can store all the chain during crossings.
In the achor locker there is a 2 part nylon fitting that fits around the chain where it enters the pipe to make it watertight. The chain feeds out of the bilge compartment by itself but need to bee put in by one person inside while one feeds the chain from the anchor locker. That takes a littel effort but make it possible for us to store all the chain in top of the keel while doing crossings. and ready to deploy at landfall.


Arne Mogstad

Maybe not very relevant for most, but a major part of why I bought a yacht in the first place, is to go scuba diving in harder to reach places. Doing technical diving (rebreather and lots of extra bottles), the total gear easily weighs 100 kg per person. It is hard to find good places to store the majority of this gear, apart from on the transom/sugar-scoop. I can absolutely tell the difference the ~150 kilos back there makes on my ~40 foot OVNI. Reading this makes me realize I should make a bigger effort in finding more suitable locations for the heaviest items during passages at least. It may also be yet another reason to try to fit the dinghy under the boom instead of in front of the mast, and maybe even trying to lay the chain towards the aft part of the anchor locker. I’m unsure how much the chain will impact, but I’m sure I can move the center of mass at least half a meter aft by taking a bit of care when I lift the anchor if comparing a worst case with a best case chain storage.

I don’t think the motion is very bad as it is, but that may be due to the fact that the mast on my boat is fairly low. I suspect this lets me get away with more than a racer/cruiser would, if it was loaded up the same way.

Interesting article, and very good to get some numbers on it, even though they are not directly transferable.


Colin Speedie

In 2009 we overwintered our Ovni 435 in France. On the pontoon right behind us was another 435, just returned from the Caribbean.

Our Ovni floated to her waterline exactly – I had worked hard to keep the weight out of the bows and stern and ensure she was trimmed as best we could. The French Ovni was down at the stern and six inches up at the bow. Which was hardly surprising as he had a big alloy bottomed RIB with a 15hp outboard in davits off the arch, wind generator, dive bottles in the aft lockers etc.

One day, the charming French owner of the other Ovni came down and we got chatting. He complained of handling issues upwind, and I (politely) suggested that all the kit on the stern might be having an effect, as ours didn’t have such problems. ‘But they’re not the same models’ he protested. It took quite some persuading to convince him they were the same boat……

Robert Gramcko

Hi recently saw a podcast about a boat with a feature i wondered why do it.
You’ve explained perfectly.

The chain locker was rather far inboard, fairly close to the mast. A hawser pipe led forward to the bow.
Now this makes sense. Moved half or so of anchor-rode-chain mass aft.

I wonder if it is practical to move windlass back or perhaps even inside chain locker? Weight aft and shorter heavy cable runs.

Colin Speedie

Hi Robert

yes – every Boreal has the windlass just ahead of the mast and the chain locker below it in the bilges.

Dick Stevenson

Hi Eric and all,
A variation on having the chain below the forepeak berth:
It is not possible for every boat, but Alchemy, a Valiant, has nice sized limber holes and a deep bilge. I was able to lay PVC pipe/conduit, just large enough to accommodate 5/16 g4, along the crotch of the hull from the anchor well to a mid-ships bilge. The conduit is to provide a protected channel for the chain to travel while still allowing “stuff” to be stored around and on top of the conduit.
Coastal cruising, 100 feet or so of chain stays in the locker: usually enough for most anchoring, at the bow while 200 feet stay in the mid-ships bilge. The extra chain is able to be pulled out easily if needed from the bow along the conduit.
Passage making, I can pull all but about 40 feet back to the bilge and the 77-pound Spade stays on the bow well secured, but easily available at passage end as is the chain.
My best, Dick Stevenson, s/v Alchemy

Dick Stevenson

Hi Eric and all,
Reading all of this reminds me of running into a friend many decades ago in Martha’s Vineyard who had just brought his mast-less boat (longer story, but John, a Fastnet 45) down from Boston. He thought it would be no big deal to motor down, but found the motion of the boat without a mast and rigging at best very uncomfortable and, when in open water, quite scary. He had bruises in quite a few places where, as he put it, the boat snuck up and hit him unexpecatably and with force.
I have never forgotten that story.           
My best, Dick Stevenson, s/v Alchemy

John Harries

Hi Robert,

The Adventure 40 is designed that way too:

Michael Jack

Thanks, Eric. I have a question about the starting point for calculating additional impact of stuff we add. Are we to assume that any well designed boat is designed to be perfectly balanced when it it is built and that any additions must be equally balanced? If not, how do we know if a boat (without stuff added) is currently balanced? A related question, in my deams, I will one day commission a Bestevaer 53 which doesn’t have a place for lots of solar panels. If I ask Mr Dykstra (or any designer) to add a big rig at the back to take solar panels and other gear, do I assume he will design the boat differently to adjust for the additional weight and therefore keep the boat in balance out of the gate?

Douwe Gorter

Hi Michael, I happen to own a Bestevaer 53, building no 2. There is actually a lot of space for solar panels when you put them on the Bimini frame that covers the entire cockpit. This is what I plan to do. It should be fairly easy to put some 900 Watts. The original,owner had a stainless steel frame build for solar panels, a radar scanner and a heavy windgenerator. This was a really sturdy frame adding more than 250 kgs at the far back end. It was the first thing to leave the boat when I bought her, for all the reasons mentioned in the above article. On my first Dijkstra 56 we had removable stainless Davids carrying a heavy dinghy and outboard, weight more than 200 kgs, even on a 56 foot 20 tons yacht we could clearly notice the difference when these were removed for a long crossing. Dijkstra does carefully design their yachts, all the heavy items are placed as central and low as possible, fuel and water are carried in integrated bottom tanks around the keel and mast. The anchor is in a chain box some 3 meters behind the bow. The accommodation ends at the back of the pilot house. The ends of these yachts are “empty” if we don’t put loads of toys and “non- essential” gear in these empty spaces. You should realise that this design was intended to be a “retirement cruiser” so two plus two occasional guests. Sort of the interior volume of a 40 ft fitted into a 53ft hull, doing so it is possible to have a well balanced boat that is isn’t prone to pitching when you respect the initial intentions of the designer.Gerard Dijkstra is an expert in this discipline. If you really want an ugly big rig at the end of a Bestevaer, you might want to consider a different design or go for a heavy steel boat where the impact of stuff in the “wrong” place has less impact on the movement.

Michael Jack

Thank you, Douwe. This is very useful and I certainly don’t want that heavy steel thing on the back of any boat. I just sent you a LinkedIn invite (well I hope it was you) to catch up offline. Would like to pick your brains on the Bestevaer.

John Cobb

Great article!

Paul Browning

Thanks for the bits in blue. Not much of the rest made much sense.

P D Squire

Great article thanks!

So think twice before installing a 2.2lb masthead camera?

Is there anything we can do to reduce roll at anchor? And if so, is it to the detriment of sailing?

I wondered how the pitch moments might compare between a ketch-cutter & a sloop with the same sail areas. Looks pretty close.

Ketch Cutter vs Sloop.jpg
P D Squire

Thanks Eric,

I agree, single mast cutter is the rational choice.

It took me a while to understand that mass near the fore-aft centre (like a mast) increases the moment as it gets higher. Eventually a metronome came to mind and it made sense. Move the weight up the pendulum, and the metronome slows down. So, with a musician’s eye the sloop’s extra mast height looks just as detrimental as the ketch’s bowsprit.

The A40 gets it right. Minimal pitching moment for a given sail area. Nice.


Maxime Gérardin

Hi Paul,

thank you!

Brian Russell

Roll at anchor can ruin your evening for sure. We have successfully used a hinged stainless steel roll-stopper from Magma. We hang it from the whisker pole at right angle to the hull so it’s about 8-10′ outboard , and 10-20′ deep. It immediately suppresses roll. I don’t think there’s enough force on it to stress the rigging, at least on our stoutly rigged cutter. Also, a stern anchor can be used to pull the boat into a more wave perpendicular position, but this is usually much more involved, especially when you are ready to depart the anchorage.

Colin Palmer

Being a bit of a nerd, I could not resist doing some sums on this, but I will spare you the formulae. I have the hydrostatics for my Ovni 345 and the weight:WSA ratio works out a bit less – about a 5% increase for a 10% increase in weight, so at moderate speeds about a 2.5% increase in resistance, which results in a speed loss of about 0.05kts at 6kts. Not so much.
The effect of weight distribution was more interesting. There are a number of technical papers around that enable you to estimate the added resistance in waves. Note that this takes no account of the loss of driving force in waves due to the pitch motion, so is an underestimate of what we actually experience, since high added resistance in waves is directly correlated with large pitch amplitudes and thus loss of sail drive.
These papers use a number called the gyradius as the basis for the results, which is directly reated to the pitch axis moment of inertia. In one paper, increasing the gyradius from 0.2 to 0.24 increased the added resistance in waves by 50%, in another going from 0.23 to 0.31 increased it by 70%. OK, so what do these numbers mean?
First off, the added resistance in waves (not especially big ones) was around half or more of the calm water resistance – a lot!
In the case of my Ovni, 200kg of anchor and chain at the bow increases the gyradius by around 15%, from 0.23 to 0.26, so increases the added resistance by about 25%.
These calculations put numbers to what we know from experience – wherever possible keep weight out of the ends in order to reduce pitch amplitude and added resistance.
This is a very, very broad brush extract from the research results, which go into a lot of detail about how the motions (and associated addded resistance) vary with heading relative to the waves, wave height and wave period as well as hull form characteristics such as displacement:length ratio (high is bad!). The results say nothing about motion comfort.
One last observation, the data also says that slender hulls expereince a lot less added resistanc in waves.

Iain Dell

Thought-provoking article – many thanks. I appreciate the clear explanation of the mathematics which deepened my understanding of Colin’s articles on the choices he made in fitting out his new boat and those about the A40.

Everything is a compromise but it’s really useful to understand the science behind the options of we’re to properly determine the costs & benefits of any changes on our own boats. I needed to add extra solar and a radar, plus my wife felt insecure at the helm so we thought an arch was best for our quite light 40’ Hanse that we cruise together for 6 months/year from France-Norway and everything in-between. It’s achieved the effects we wanted but the added 40+kg right at the back made me wonder if I should have balanced that with a similar amount forward or if that would just compound the penalty. From this article I understand now that, provided overall trim is still ok, seeking to balance that weight would simply encourage the boat to hobby-horse in waves. Have I missed something, please?!?

Stein Varjord

Hi Eric,
An interesting article that reminded me of some things I knew, made me understand some things clearer and thought me things that wasn’t clear to me. Thanks!

One small detail in your comment here, which you’re definitely aware of, but others might misunderstand from the wording: When moving mass lengthwise, we can’t refer to midship or the centre of flotation, but rather the rotational centre of the pitching motion, which perhaps isn’t super easy to define, but usually it’s well aft of midship. Somewhere around one third of LOA (total boat length) from the stern could be an approximation?

That means moving a heavy item forwards to the rotational centre will minimise its detrimental effect on pitching, but it will still contribute to a heavy stern, just a bit less than if it was further aft. Also it means that adding weight forwards of the flotation centre to compensate for a heavy stern, means that compensation weight will be about twice as bad for pitching as the same weight on the stern side of the balance. It’ll move about twice as far.

I’ve always been a weight saving fanatic, but this reminds me why.

Iain Dell

Hi Eric- really grateful for your comments; they made me have a good, hard look at all the weight aft and gave me the motivation to do some serious shifting around which has made a surprising difference. Its been useful to read your technical appraisals in conjunction with Colin’s on the practical reasoning he’s employing in fitting out his new boat. Our cruising style is similar to his and we’re now questioning if we really do need that super-heavy liferaft and not the single-chamber alternative when in permanent range of some of the best SAR networks in the world.

Brian Russell

Thanks for the excellent and clear article, Eric. I would point out that holding tanks often seem placed in the bows under the forward berth, and the weight of the grey or black water could be significant. I now need to sell my spare Rocna 33 which is sitting in the anchor locker, and move that stainless steel flopper stopper device (which we use frequently) to a more central location. And maybe I don’t really need 1000′ of 3/4″ rope rode up there…

Michael Jack

Hi, Eric. After reading your article again and also the relevant chapters in Desirable and Undesirable Characteristics of Offshore Yachts there are still some questions in my head. They came up this week after having to motor 250 miles from near Oslo to the South of Sweden against the winds generated by ex-hurricane Nigel. During that voyage, with the many and varied wave conditions that are to be found in the Skagerrak and the Kattegat (no point in even speaking of wave duration in those seas and those conditions because you usually have 3 waves all from different directions under the boat at once), I had lots of time to contemplate the pitching behaviour of my Sweden Yachts 41. So here are the questions:

  • Are pitch, roll, and yaw moments of inertia all at the same place in the boat?
  • How do you identify on any particular boat where they are? Especially relevant to pitch I think to know where to put extra weight if needed.
  • How do you know if pitch is out of whack especially in the seas described above (or any sea really)?

I studied the pitch of the boat for hours and could not come to a conclusion as to whether the pitch was good or bad or in between.



John Harries

Hi Eric,

Thanks for the fill on that.

I would add one thing for others, which you already allude to:

Sure weight in the stern is not terrible as long as the boat floats to her mark (trim) but what I see so often out there is boats trimmed down by the stern which is SLOW as any race boat sailer will tell us—dragging the stern adds a lot of wetted surface and wave drag too.

So, what many will say is “no problem, I will just move weight forward to compensate”. But the problem here is that said weight must be moved the same distance ahead of the centre of flotation, not the pitch axis, and the result is a it’s a long way forward of the pitch axis and that effect is squared, so horrible.

I have always kinda known this from observation, but it was a huge light bulb moment for me when reading your article above.

Michael Jack

Thank you both and very helpful. And you answered what was going to be my next question, Eric which was, if you are designing a boat, isn’t knowing the moments of roll and pitch inertia a good thing for deciding where to put the sea bunk/s.

John Harries

Hi Michael,

Sure, the closer you can get the sea buncks to the pitch axis the better. More thoughts here:

Jim Schulz

Thanks for the great article Eric. It’s provided quite a bit of clarity for me on the “why” behind practical guidelines. I have a question on the effect of height in the equation. You mention it briefly in the description of roll but not in pitch. Why is that?

Specific to our boat, we have an Ericson 38-200 which has a shallow chain locker “pan” sealed above an empty locker below it in the bow. I’ve been thinking of removing it and moving the chain lower in the bow for a few reasons but one is that I’ve thought it would help to have the weight lower in the bow. Is this correct or is it irrelevant? The way the spaces are configured the change wouldn’t move the weight aft at all, just lower.

Jim Schulz

Thanks Eric, measuring the radius from the axis clarifies it for me and the vertical COG concern makes more sense as to a “why” for potentially lowering the chain. Drainage to the outside and closing off the current access from the v-berth to the space are my big concerns. I’m leaning toward leaving things as is while I’m still comfortable hauling the chain with our manual windless. We don’t have a ton of weight – 20kg anchor, 100’ of 5/16 G40, and 200’ of 5/8” nylon rode and it’s pretty easy to keep the chain at the aft end of the locker.

Jon Moss

Hi we have a Malo 42 1997. We are thinking of fitting an Arch for solar and a D400 and possibly the radar. However we are also wanting davits. How would all this work ?

John Harries

Hi Jon,

I 100% concur with Eric’s advice and I used to be an arch fan—I had one in the original A40 specification—but after learning more from the engineers (Eric, Matt and Maxime) here at AAC I would look for pretty much any way to avoid adding that much weight and windage to the stern of a nice sailboat like the Malo 42.

Keep in mind that when you add all that weight aft, you will need to move a lot or weight forward to get her back in trim, and that weight, because the pitch axis is aft of the axis of flotation, will have an even worse effect on pitching. And that effect is squared by the distance from the pitch axis. The physics conspire against us on this one!

And finally, many Malos have in mast furling which is already a huge hit to pitching because of the increased weight up high. If that’s the case on your boat I can see adding an arch and davits may create a situation where your boat simply won’t sail properly with the wind forward of the beam and any sea at all and will be uncomfortable and inefficient when motoring.

Ken Austin

Very interesting to learn some of the facts/math behind the concepts. I am especially interested in the weight of the anchor chain in the bow. I may look to follow the ideas presented by two about setting up a conduit to have extra storage of chain under the v berth which seems quite helpful. Question for you- if one can’t set up the conduit from under v berth to chain locker, what is your view on having the first 75′ in the bow and then having the next 75-100′ under the v berth and ready to be attached in the same manner one attaches the anchor chain to the actual anchor ie screw in shackle wired down? Thank you, Ken

Dick Stevenson

Hi Ken,
It does not happen often, but, in a middle of the night “fire drill” of some sort, I would want to have all my rode available without the time necessary to link chain together, especially with fumble-fingers when hurrying. Where weight was a concern, I believe I would consider (in most cruising grounds) to have the 75 feet of chain you mentioned to be then attached to a length of nylon rode.
Moving beyond what you have written, perhaps you have one of those enclosed anchor wells/chain lockers with a little drain overboard. I have always been suspicious of these in blue water sailing. Most seemed to allow random water into the well with little restraint and it would not take too much mud or seaweed to clog that little drain hole and allow the well to fill.
I know of one windlass failure (installed inside the well where it was “protected”) that was attributed to this happening.
I was fortunate as there is an ample limber hole at the bottom of my chain locker (no outside drain) which allowed me to pull the chain aft and into PCV conduit and bring the extra chain amidships, but still easily available from the bow. (BTW, if a limber hole into the bilge of the boat, it is a good idea for the chain to be retrieved clean making a deck wash for spraying the chain important).
I suspect a limber hole like that could be added to most of the bulkheads separating an enclosed anchor well from the boat interior: perhaps a little added reinforcing around the hole might be considered.
My best, Dick Stevenson, s/v Alchemy

Ken Austin

Thank you Dick for the insights, good points for sure and will see if I can arrange as you suggest. Tks Ken

Ken Austin

Thank you , that makes sense and as I will be in the S Pacific another article on this site strongly suggested all chain given coral so I think I need to figure out the pipe configuration with heavy anchor. I had planned on 3/8 G40 so would be interested if you have further thoughts on strength vs weight that you mention. Tk you, Ken

Dick Stevenson

Hi Ken,
I would suggest choosing chain by strength and not for weight.
The argument for weight is that it produces a useful load-absorbing catenary. However, I believe that, in gale conditions, when you want it most, that catenary is no longer available as the chain becomes fully stretched out (no longer able to absorb load) in gusts and sea state.
I would look to load absorption from a snubber, choose chain by strength, and put ground tackle weight into the anchor where, pound for pound, weight is most effective at keeping the boat attached to the seabed.
For example, I have been using g40 5/16” inch chain for decades with (last 8 years or so) a 77-pound Spade on a 40-foot heavy displacement sailboat.
Lighter chain also allows for greater length as the weight difference between 3/8ths and 5/16ths is substantial and greater length allows for more options when anchoring deep as some cruising grounds necessitate.
My best, Dick Stevenson, s/v Alchemy

John Harries

Hi Ken,

We have a chapter on chain grades and the strength to weight trade off: