Boat design with regard to number of people on board.

[fredrussell]

My 31 foot boat has room for six people in the cockpit, and, technically at least, six berths. So am I right to assume that the boat was designed to sail in its most ‘balanced’ form with the best part of half a ton in the cockpit? I mostly single-hand the boat. I weigh 80kg or so. With just me in the cockpit will the boat be down at the bows? I’m not concerned as obviously there’s not much one can do about this, but I was just wondering today how boat designers approach this problem.
My boat’s displacement is listed as 3 tons, though nearer 4 tons I should think with all my clobber - so half a ton often ‘missing’ from the aft end seems, well, quite a lot really.

 

[Wansworth]

Lots of light displacement boats where designed so they were stearn up whilst at rest,I imagine in a 30foot cruiser it will be negligible

 

[boomerangben]

I guess it depends on the details of the hull shape and specifically the transom/water interface. I remember marvelling at how little wake a traditional lug sailed Hebridean Sgoth generated (canoe sterned) and how much wake a dinghy generates when the bottom edge of the transom is submerged. So it might be that your boat performs better single handed. Try looking at the wake in smooth water for different loads

 

[Daydream believer]

A lot of boats have a lot of stowage in the stern to start with. Spare fuel, spare gas bottles, life raft, life jackets, fenders, sails & other gear. I have a wind steering as well. All adds to load aft. I do carry a lot of spare fuel.
However, a lot of boats sail better upwind, with the bow down a bit. My last 2 boats did & this one does as well. So when sailing SH I move all my sailing clothes, bags etc to the forward cabin
My boat is 31 ft, 6 berth, tiller steered & there is only room for 3 in the cockpit, because 1 space is taken by the autopilot.
Comfort wise it suits 2. No one wants to be stuck down to leaward when going upwind. Especially if a bit seasick & it is a bit bumpy. Neither do many want to go below.
So I would recommend a max crew for any distance of 3 -or 4 if only a long day sail & one is able to go below for long periods. My wife refuses to come on deck as she hates looking at the sea, so she is the one to go below.
We have had 6 aboard for 14 days but that was in the canals. When it came to the ocean part the ladies went by ferry. They also stayed in hotels for a some nights.
It gets beyond a joke laying in the saloon berth having someones rear rubbed in one's face 10 times every morning when the girls decide they need to make 10 visits to the heads for various reasons & push past the table.

 

[Daydream believer]

Regarding 6 on a boat
We were in Middleburg & going for a meal. Wife, daughter, daughter in law, Son, my mate Edd & myself.
Now it has to be realised that 6 people for a fortnight accumulate loads of gear. Not to mention girls with a dozen pairs of shoes each, kicking about all over the place. Therefore, everything has to be carefully stowed in the lockers & in spaces under the bunks. That means moving bedding up for''d & rolling up bedding in the main saloon & storing in the for'd cabin.This operation has to be done with clinical efficiency several times a day.
So, We have all the faff of 3 ladies getting dressed for dinner & Edd is just as bad. We are running late & I am getting fed up. So I get off the boat & stand on pontoon pacing up & down. Son gets off, Edd finally gets off, Wife gets off & tells me to keep my mouth shut & wait. (Doohha) Daughter in law finally gets off after last of gear stowed.
Daughter "nips to heads" ( cannot wait until we get to restaurant just by the marina) whilst we listen for sound of pumping, then she gets off
Finally, I can get back on boat & start to lock boat. Just as I am about to snap lock shut daughter says " I feel a bit cold, I think I need my coat". Wife jumps on boat, tells me to calm down. I open up again & go onto pontoon out of the way as instructed by wife, to calm down. Daughter gets on, goes below, Moves bedding, lifts berth cushions, gets bag, gets coat, puts bag back, puts cushion back, puts bedding back, finally exits. I get back on boat, slide hatch shut, just as daughter in law says " You know what? I think I had better take my coat as well"
I throw boat keys at wife & walk away.
Take my advice. 6 people on a 31 ft boat for more than a couple of days is a no no, especially if 3 of them are b..y women
I normally sail SH, it is lovely

 

[mjcoon]

Regarding 6 on a boat
We were in Middleburg & going for a meal. Wife, daughter, daughter in law, Son, my mate Edd & myself.
Now it has to be realised that 6 people for a fortnight accumulate loads of gear. Not to mention girls with a dozen pairs of shoes each, kicking about all over the place. Therefore, everything has to be carefully stowed in the lockers & in spaces under the bunks. That means moving bedding up for''d & rolling up bedding in the main saloon & storing in the for'd cabin.This operation has to be done with clinical efficiency several times a day.
So, We have all the faff of 3 ladies getting dressed for dinner & Edd is just as bad. We are running late & I am getting fed up. So I get off the boat & stand on pontoon pacing up & down. Son gets off, Edd finally gets off, Wife gets off & tells me to keep my mouth shut & wait. (Doohha) Daughter in law finally gets off after last of gear stowed.
Daughter "nips to heads" ( cannot wait until we get to restaurant just by the marina) whilst we listen for sound of pumping, then she gets off
Finally, I can get back on boat & start to lock boat. Just as I am about to snap lock shut daughter says " I feel a bit cold, I think I need my coat". Wife jumps on boat, tells me to calm down. I open up again & go onto pontoon out of the way as instructed by wife, to calm down. Daughter gets on, goes below, Moves bedding, lifts berth cushions, gets bag, gets coat, puts bag back, puts cushion back, puts bedding back, finally exits. I get back on boat, slide hatch shut, just as daughter in law says " You know what? I think I had better take my coat as well"
I throw boat keys at wife & walk away.
Take my advice. 6 people on a 31 ft boat for more than a couple of days is a no no, especially if 3 of them are b..y women
I normally sail SH, it is lovely

Very similar circumstances, probably similar number of crew. But rest of crew leave for the marina restaurant smoothly, except that my prostate insists that I ensure I empty my bladder before leaving, so they had not noticed I was incarcerated and locked up on leaving. I cannot open the companionway, and the dinghy is securely tied down over the forehatch. Fortunately I am skinny and wriggle under the dinghy. Halfway to the meal I meet the key-holder who eventually noticed that I was missing and was coming back...

 

[Concerto]

Fred, most boats are slightly nose down. With Concerto it is difficult to notice as I raised the waterline at the bow by 1½ inches and she now looks as if she floats level.

Having a lot of chain and a large heavy stainless steel holding tank under the forward berth does not help. The engine has been changed from a Bukh to a lighter Beta. Sails used to be stored in the sail locker, but with a furling genoa there are less sails aboard stored aft. The large sail locker is not empty as it has the inflatable, warps, etc. The outboard is on the aft rail. Shortly I will be fitting a wind turbine on the stern. The 40 gallon fuel tank and 60 gallon water tank are under the cockpit, and when both are nearly empty that is a lot of missing weight. Sailing singlehanded also reduces the weight aft. Being slightly bow down is more noticable when sailing, but does not affect performance.

 

[Chiara’s slave]

.
It gets beyond a joke laying in the saloon berth having someones rear rubbed in one's face 10 times every morning when the girls decide they need to make 10 visits to the heads for various reasons & push past the table.

Some people pay good money for that, though I guess it depends on the rear.

 

[davidmh]

Would be interesting to have a reply from a boat designer

David MH

 

[johnalison]

Cockpit parties in our Mystere were always interesting because with a complement of more than about five people the stern would sink sufficiently to cause a minor flood, resulting in the need for me to pop inside from where I could get at the seacocks for the drains.

 

[Resolution]

On a rainy night in Yarmouth we managed to fit 29 people inside a pal's Bavaria 49. He had a fine stock of malt whiskies, which made for an excellent party notwithstanding the storm outside.

 

[michael_w]

Most boats would suit the number of people vis a vis the number of berths provided that they are all nudists with no gear.

 

[Chiara’s slave]

Cockpit parties in our Mystere were always interesting because with a complement of more than about five people the stern would sink sufficiently to cause a minor flood, resulting in the need for me to pop inside from where I could get at the seacocks for the drains.

I’m always amazed when this happens, and I’ve seen it several times, even on a 45 footer. We’ve had 12 people on board, at the back end of the boat, ie cockpit and conversation range of it but on the tramps, and she goes down maybe 3 inches, nowhere near flooding back through the drains.

 

[colind3782]

I was told years ago that the size of a boat shrinks by a foot per day times the number of people on board.

 

[graham]

The ends of the boat are the worst place to store heavy items from a performance and seakeeping point of view but on a cruising boat you more or less have to live with it unless you want a big pile of anchors chains and spare fuel cans in the saloon.

 

[mjcoon]

I was told years ago that the size of a boat shrinks by a foot per day times the number of people on board.

Sounds like it will disappear up its own seacocks in no time...

 

[V1701]

I sold a 1969 Bowman 26 to a Portuguese guy who had trouble regisitering it because there was nothing official about the max number of persons it was designed to carry...

 

[srm]

I’m always amazed when this happens, and I’ve seen it several times, even on a 45 footer. We’ve had 12 people on board, at the back end of the boat, ie cockpit and conversation range of it but on the tramps, and she goes down maybe 3 inches, nowhere near flooding back through the drains.

I used to have an older boat, narrow beam, LWL 30ft LOD 42ft. When nearing hull speed on a broad reach the stern wave would support the counter and there would be a flow of water in through the stern cockpit drains and out of the forward ones. A bit disconcerting for new crew until they understood what was happening.

 

[LittleSister]

I very much doubt that boats (or at least very many of them) are designed to trim correctly with the number of berths times crew in the cockpit.

Nobody in their right mind voluntarily cruises with the same number of adult crew as berths squeezed into most boats (or at least does so and allows all of them to be out of their berths at the same time!), and as few boats do we'd all be sailing around bows down and hence struggling to steer if they were designed for a cockpit full.

For racing, it's traditional to banish part of the crew to the foredeck, and part to the windward rail. (I've not done enough racing to find out whether that's for boat balancing or to avoid BO problems. )

I suspect your boat, Fred, would be OK with six adults in the cockpit (if a bit tight space-wise), but a little down at the stern.

I am advised that an LM27 (which has between 4 and 8 berths, depending on how you count them) will start backfilling via the cockpit drains if you have 11 adults in the cockpit! Fortunately, for partying purposes (though not for surviving the ultimate storm), mines an earlier non-self-draining cockpit model.

 

[Wansworth]

I sold a 1969 Bowman 26 to a Portuguese guy who had trouble regisitering it because there was nothing official about the max number of persons it was designed to carry...

Iberians do so like the detail and have forgotten their seafaring history