Trade Offs in Yacht Design

Arrangement plan, kindness of Ian McCurdy, McCurdy and Rhodes Naval Architects. Click on Plan to see larger.
Arrangement plan, kindness of Ian McCurdy, McCurdy and Rhodes Naval Architects. Click on Plan to see larger.

Eric Klem, engineer, frequent and erudite commenter, and sailor, came up with some great thoughts on my Adventure 40 interior post. I started to address each of his concerns in the comments, but then it struck me that we had the basis of a good discussion on the inevitable compromises that must be made in designing or living aboard any voyaging boat. (Also, thanks to Richard (RDE) Elder for his comments to the same post that influenced several of my thoughts below.)

Please understand that this post is really not about the specific details that Eric and I discuss, but rather demonstrates that you simply can’t have it all, and that every decision you make will have side effects, some of them undesirable. Whether or not you end up with a good boat is about how you handle those compromises.

So imagine, if you will, Eric and I sitting in the pub over a couple of beers.

Engine Access:

Eric: One question I have is about engine placement. I assume that you have the engine in the traditional place under the companionway steps instead of doing something like the Passport 40 [further forward under the galley].

If this is the case, the interior arrangement will have a huge effect on how easy the engine is to work on. I like the general arrangement that you outlined but I am a little concerned that putting the shower and head where the chart table is on Selkie might make it very difficult to get access to the starboard side of the engine.

Unfortunately, it seems like the only things that provide decent access while doing double duty are berths and stowage. Since the port side is already compromised by the galley, maybe making the engine room wider than necessary so that someone can crawl along the side of it would be a reasonable compromise.

John: Eric, that’s a very good point, good engine access is vital. If necessary I would sacrifice galley and shower space to preserve it, as you say. However I really don’t like the idea of crawling in next to the engine.

How about this? We make the shower stall, in effect, an extension of the equipment bay—more of a passage closed by curtains, with a drain in the floor, rather than an enclosed stall? Then what we can do is put a big hatch in the inboard side of the shower (gasketed of course) that will give good access to the engine.

That coupled with steps that are hinged at the top and lift up will give great access to the front and starboard side of the engine and all the way back to the drive train and rudder post. Of course, we will need to make sure that we don’t crowd the port side of the engine too closely with the galley, just as you say and we must be willing to sacrifice galley space to do that.

Eric: Eliminating the nav station would eliminate room for the electrical panel. I like this to be close to the companionway so that I can easily pop down and switch on the nav lights or something like that but I also think that it needs to be far enough from the companionway that it doesn’t get soaked all the time.

John:  Hum, I hear you, but let’s look at the trade offs. If we site the panel in the equipment bay we will reap big time cost and simplicity benefits by having it close to the batteries and main buss bars. This is also where all the conduits for the wiring for owner installed electrical and electronic gear will be terminated too. Yes, I know, this is a bit inconvenient for turning stuff off and on but really, how bad is it to duck through the shower for a switch, compared to the benefits of centralizing everything?

Also, with this approach, all the electrical stuff will be safe in the equipment bay from the splashes of salt water, that you so rightly identify as a risk.

Cabin Sides and Room Under The Side Decks

Eric: Looking at the outline of the housetop on Selkie, much of the working area of the galley and the settees are outside of it. I suspect that a 40′ boat is large enough that there will be plenty of room at the settees for this but it might be tight in the galley.

I have been in many galleys where I have to bend down to work over the stove or end up looking straight into a wall and can’t see the stove when I stand up. I hate to admit it but I have come to accept the gently sloped house sides that some of the modern production boats have. Structurally, I suspect that they are easier to design. They provide more room down below and a good surface to walk on while on deck and heeling over. Obviously this can be overdone and side decks can become much too small.

John: Yes, this is a problem on any boat up to about 50′. However, the problem is not as bad as you might think on deeper hulled boats like Selkie because the sole is lower (see plan). I think we can also raise the freeboard a bit without making the boat look boxy. Good idea on angling the cabin side a bit too. With all that we should have most of that problem solved. Of course, good wide side decks that are easy to move around on are sacred to both of us and won’t be compromised for the interior.

V Berth

Eric: The way that the V-berth is done on Selkie would likely not be very good for me, though I do think that this type of berth is the only way to get all of the features desired into this size boat.

At 6’4″, I have found that the only way to get into these when the end of the bunk is obstructed is to crawl in head first on my hands and knees then spin around and lie down. This isn’t too bad when I am alone but my wife definitely does not appreciate it.

Also, I find that I am trapped unless I wake her up and have her move out of the way. The simplest solution for me would be to have the entire aft end of the berth unobstructed so that I could crawl off the end. This space could double as a place to change, put on shoes, etc.

John: There are a lot of trade-offs to deal with here. Yes, you could leave the head of the bunk open to facilitate entry and exit, but that means you lose two lockers so you have nowhere to put your clothes, your pillows drop off the bunk all night—something that drives me crazy—and you have nowhere to prop yourself up to read. We will have to arm wrestle to decide that one.

Hull Form

Eric: It would be interesting to see how a hull form like Selkie would be updated for use today. I wonder whether extra interior space would emerge or whether it would remain similar. Looking at the drawing, several feet of boat in each end are unused both on deck and down below. They are obviously there for good reason but I wonder whether new understanding of hull forms means that we can better use the ends of the boat or whether boats that use the ends now are designed around an interior.

[John starts waving his arms and bouncing up and down in his chair…then upsets beer all over himself. After mess cleaned up, John, now sitting in rather strange position due to soggy jeans and puddle of beer in his chair, answers.]

John: Pushing the accommodation out to the ends? No, no, no, no. Oops, sorry was I shouting? [People start leaving pub for quieter venue, manager comes to complain.] Seriously, as soon as you go down that road you invariably start messing with the correct hull form for a good offshore boat, just as you mentioned, and break a fundamental tenet of the Adventure 40 ethos, or in fact any good design: No criteria will be allowed to intrude into the design that will have any negative effect on the hull form.

Don’t get me wrong, I’m sure we can improve on Selkie, particularly since her design was, I think, influenced by the IOR rule of the time—look at her stern. We can also, I think, make the Adventure 40 longer on the water than Selkie, since we don’t care about ratings. But even there, we can only go so far, because if we make her longer on the water that will make her displace more—bigger and more expensive—since it will result in putting more boat in the water by definition, unless we make the hull shallower.

The basics of water plane, beam to length, displacement to length, reserve buoyancy, and correct prismatic coefficient can not be messed with without substantial negative consequences for seakindliness and speed.

This is why Carina, Selkie, and the new (and old) Navy 44s, still kick ass and take names every time they race offshore, and the tougher the race, the better they do. And not only do they go fast, their crews get where they are going in much better shape that those on light, wide boats that pound.

Can we distribute the hull volume in a better way than Selkie for our purposes in the Adventure 40? Probably, but we can’t create more volume without making the boat either less ultimately stable (lower ballast displacement ratio) or heavier and more expensive.

Yes, we could make her wider and shallower with a higher prismatic coefficient (fatter ends). But what happens to the boat then?

And what have we gained in terms of real usable volume? Well, a little if we make the keel lighter, but we have paid a big safety price and pushed the fuel tankage into the accommodation. Is it worth it? I say no.

Finally, the empty ends of the Adventure 40 can and will be used for storage, at least of lighter items, since one of the great things about Selkie’s kind of hull form is that, due to clever use of reserve buoyancy, it is surprisingly tolerant (within reason) of weight, even in the ends.

Having said that, I think that we might end up with a bit more space aft than in Selkie. But no way should the stern be a lot fuller than the bow since that leads to rounding up and bow burying.

We may also be able to get a bit more volume in the hull by flaring the topsides out a bit like Boreal do. Not sure of the trade-offs here—need to do more research.

Dinghy Storage

Eric: The other thing that I think needs to be considered when thinking about ventilation is dinghy stowage on deck. Since a dinghy is not included, this is a little bit hard but there should be an area where a dinghy can be placed without compromising ventilation.

Taking Selkie’s layout for example, there are multiple Dorades up forward as well as a big opening hatch so you probably would not want a dinghy up forward and you may even be prevented from having one with the dorade boxes. Between the mast and the aft end of the spray cover, there is about 6.5′ so that isn’t long enough for anything other than a nesting dinghy.

John: Good point. We are only planning for one Dorade forward so it should be possible to arrange the foredeck so that a smallish inflatable can be stowed over the hatch and forward of the single Dorade when coastal cruising.

We do this on Morgan’s Cloud and find that a surprising amount of air comes in if we just crack the hatch under the dinghy. Of course if you want to rig a wind scoop, then you need to dump the dinghy over the side.

When offshore, a dinghy should never be stowed forward of the mast. It should either be a nesting or folding dinghy stowed aft of the mast, or an inflatable stowed below. The current practice of stowing huge RIBs forward that cover the entire foredeck is just plain dangerous at sea and should be discouraged.

John Summarises

It is important to note that each time Eric mused about something he would like to see changed, he also identified the potential problems and trade-offs. This is the kind of thinking that is all too rare but leads to good boats. (You can read the full text of Eric’s comment, which I edited down a bit, here.)

For me, one of the big problems with modern yacht design, perhaps the biggest, is that too much emphasis is being placed on trying to ameliorate every little inconvenience of living on a boat without thinking about the consequences.

For example, if we end up with a V-berth, which is generally the only way to get a proper sized double in a boat this size, at least without making the bow too fat, the crew will experience all of the inconvenience and awkwardness that Eric identified or those that I identified, or a whole different set that come with an offset double.  But does that matter? Not much, maybe not at all. Not if the owners get to live their dreams in a safe seaworthy boat they can afford.

Bottom line. You can’t take all the comforts of home with you in any reasonably sized boat. And if you try, you will end up with a lousy, and very likely dangerous, boat—it’s your call.

“Compromises, Compromises.”

The wording that I imprinted on the plan of Selkie for this post is what my good friend Michael Haferkamp, owner of the beautiful custom Hutting 54 Polaris, always says, with a rueful shake of his head, when he and I discuss boat design.


If you want to comment on the specific compromises that Eric and I “discussed”, by all means do so as long as you keep the fundamental practicalities of a boat that must not get bigger than say 19,000 pounds in mind. But I would be most interested in your thoughts on the compromises you have made to make your boat work.

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John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

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