Minimum Passagemaker/Cruiser

The rolling moment of the boat is dependent on the wave slope and the righting lever of the boat design. The righting lever is created when the boat heels either port or starboard; as the boat heels the center of buoyancy shifts away from the center of gravity creating a rotational force that rolls the boat. The strength of this righting arm and its ability to roll the boat is dependent on the center of gravity and the beam of the boat. The wider boat has a greater lever acting to roll the boat and therefore absorbs more kinetic energy from each passing wave. This should not be confused with roll moment of inertia which is dependent upon the mass of the boat and the placement of that mass port and starboard. In short, disbursing weight away from the center of the boat to port and starboard will increase the dampening effect of rolling due to the larger amount of torque needed to produce rotational velocity.

in short, a wider boat will roll more, whether or not it is more or less comfortable depends on the velocity of the rolling, which means that the roll moment of inertia as well as the beam of the boat have to be considered together.

This, of course, is the simple explanation.

 

Yes, I agree with this in general. The PDF posted by Tad is not what I would classify as passage makers. (They are light weight semi-displacement yachts.) I think ballast tanks to take on seawater to alter the rolling and pitching moments is a good idea, but that would fall outside of the minimum passage-maker/cruiser constraints suggested in this thread.

 

Tad, you dimensions are almost exactly what I would come up with for a poor man's passagemaker but what are those stick thingy's you have in your rendering?

 

Just because a boat is very narrow does not mean that pitch and roll accelerations will be necessarily greater than a beamier boat. Its actually easier to get a more comfortable motion in a light boat if its narrow.

 

Yes, agreed.

 

Apex,
Most of my experience is in boats in the 40' range and smaller. Mostly sailboats but some powerboats as well. I personally am quite comfortable in 40' boats at sea. I currently live very comfortably on a 37' sailboat. IMHO the interior layout of my boat is as good as it gets. I can't think of anything that I would change in the layout of my boat. I've attached a drawing of the interior layout of my boat.
I think that comfort or lack thereof is a combination design and what you are used to. I know lot's of couples that live very comfortably on boats in this size range. I haven't heard complaints about comfort except in really bad weather. And then it doesn't seem to matter if the boat is 40' or 50' or 60'. Heavy weather is just not fun in the size of boats that we are talking about.
I can understand how you would be uncomfortable after 36 hours on your powerboat. Again this is just my opinion and is based upon my limited experience. I could be way out in left field. I personally find most powerboats to have their living areas too high above the water. Especially flybridges. The higher you get, the greater the roll. So you have the hang on more to keep from getting tossed around. To me this is uncomfortable and tiring. The living areas on Tad's Passagemaker Lite series are much lower and you live down in the hull. Not up on top of it. The motion will be less and more comfortable. Could his 39 have a slightly different layout to be more comfortable at sea? I guess that depends on the client's SOR. If I was having one built, I would want an interior as similar to my current boat as I could get.
As far as having a designated engine room. You just don't have the space to have one on a 40' boat. I also don't think that it is necessary. Good engine access is necessary. On Tad's 39 it looks like the cabinet over the engine is on hinges at the aft end and would lift out of the way for engine maintenance. This is a compromise that I believe is reasonable. I could live with it. It's better than the engine access on my boat.
All things considered, yes I could be very comfortable on a 40' powerboat. Even crossing oceans. As long as it was properly designed for the task at hand.
Chuck

 

And even easier if two of those light narrow hulls are joined together to become one.

I will call this vessel "The Catamaran":idea:

A powered version of I which I shall use for my passages with an approx range of 2400nm @ 8 knots
And facilities on deck for additional bladders to extend range if ever required

 

To my eyes the Idlewind seems like a good attempt for an affordable passagemaker, although not perfect. It's long and narrow. Accomodations are mostly below deck. If I could change something I would like to make the topsides higher (if needed) to allow standing height below deck all over the boat, and reduce the size of the deck house. Maybe the boat should be longer to allow the topsides to be higher.

OK, there was a rolling problem with Idlewind. Couldn't that be fixed with a long but not so deep keel plus steadying "limp-home" sails?

My interpretation of "minimum" in the thread name is minimum cost or minimum size, not minimum length. For some of us there is no automatic increase in cost coupled to length, so restricting length has no value by itself.

Erik

 

Ya Chuck...youre thinking correct. And you are also doing it with your own boat. The whole reason behind the survey was to identify an effective " Minimum" ...Motor or Sail design, that real people can purchase, build and use. Im sure that if you had a spare million you would move up in size class to gain additional function. This is not the question.
30 to 40 ft is the sweet spot. . Be difficult to go under 30 ft unless you were a young guy and didnt mind a long camping trip. As far as a 35 footer being unseaworthy...makes me laugh. One year on a oceanic crossing we tangled with some severe weather north of Bermuda on the 5 million dollar, all weather, sailing yacht that I was captain of. Very bad weather. At dawn my VHF comes alive with a British voice. This calm, matter of fact, Good Morning, British voice was from a little 35 footer operated by a retired husband and wife crew asking me if I had any weather updates. The conditions outside were so bad that I never established visual contact, he could see me fine, but his little boat was hidden in the 5 meter waves.

 

Try your layout with enough fuel to motor clear across the ocean and you will see a problem with boats in your size length range.

Length is the most important feature in a passagemaker to carry enough fuel for a poor man's passagemaker.

A 35,000 lb boat with a 38' waterline length will take 960 gallons of fuel at 7.3 knots to make 2,400 NM in 328 hours (S/L 1.2) You will have trouble finding the room for 960 gallons plus reserve in a 40' hull

A 35,000 lb boat with a 55' waterline length will take 790 gallons of fuel at 8.9 knots to make the 2,400 miles in 270 hours (S/L 1.2) You will have no trouble finding enough room for 790 gallons plus reserve in a 60'X10' boat and keep her weight down. The shorter boat will cost about the same to build but will be no where near as comfortable at sea. I agree that 60' X 10' is a very good size for a poor man's passagemaker.

Slow the long boat down to 7.3 knots and you only need 500 gallons. Half that of the shorter boat.

Tell me where the ecomony is in the short boat as a passagemaker. A short boat as coastal boat, sure but not as a poor man's passagemaker.

I would make the boat in either unpainted aluminum or epoxy ply.

 

This thread came right out of Apex's threads on powered perfect passagemakers and I take that to mean this thread is about powered passagemakers for a skinny wallet. A Flicka will satisfy the minimum requirements under sail, no need for a 35' boat if you are talking sail.

 

Gee Pierre...the questionnaire indicates that 57 percent of respondents checked SAIL as a feature of a minimum cruising boat ? I have nothing to sell nor any agenda to push and had no idea that this thread was to compliment Apex's business with motoryachts. I would never commit any of my thoughts or decades of experience and observations as a yacht captain to anything which benefits this Apex guy. The reason you must stay near the 35ft loa number minimum on any yacht are ergonomics, load storage capacity and speed.. Be my guest to go bigger !

 

since this thread com from the passagemaker thread

as long as some still talking sailboat, we are going no where.
we are talking motor boat.
please raise your hand: how many of you crossed the atlantic north in winter with a motor boat in the 40' range? and i mean crossing non stop?
your experience can be a good start for the smallest size.
for me it is 50' if very heavy.

 

57% probably do consider sail as a feature of a minimum ocean crosser but that does not change this thread. You will find many more threads on the minimum sail subject than the minimum passagemaker subject and with far more passion in the responses.

The OP started this thread as an alternative to what Apex was saying in the perfect passagemaker thread, not a compliment to his thoughts, more the opposite.

I do agree with what you are saying here in sail. Personally in sail I would stay under 50'. Above that I would go power.

 

And you are correct. Power needs length. long and thin . 35ft wont get you far. But any power driven craft with transatlantic range will be twin screw, machinery intensive and expensive. It could be possble to consider this a minimum, everymans, concept. Steve Dashew pursues the minimum power oceanic line of thinking very successfully . Nigel Irens is also a pioneer in modern motor vessels.
http://www.nigelirens.com/ldl/index.php