Minimum Passagemaker/Cruiser

Pierre,
I don't think that you are comparing apples to apples. I agree with you that if you increase the displacement by 75% on the same LWL and run at a higher speed, 1.2 S/L verses 1 S/L, you are going to burn double the amount of fuel. Maybe more. And carrying that amount of fuel on a 40' boat might be tough. But maybe not. Your example increased the displacement by 15,000 pounds. This would be a significant increase in volume. The additional 300 gallons of fuel that you are proposing over the capacity of Tad's 39 would only weight about 2,200 lbs. With your proposed increased displacement of 15,000 lbs you would still have 13,000 lbs. to play with. The increased structural requirements would take up part of 13,000 lbs but not all of it. So by your own example one should be able to carry the amount of fuel that you feel is necessary. In your example, you might even be able to triple the amount fuel. But that would take a detailed study of a preliminary design to see if you could fit it in. If you limit the displacement to the 20,000 pounds of Tad's 39. I would agree with you that it would tough to fit in the extra fuel and probably not possible. I can't answer that question.
As to the layout of my current boat being used in a powerboat, I apologize if I was not clear with my thoughts. I did not wish to convey that I would use the exact same layout. Just something close. I would want a pilothouse like in Tad's 39. I would place the pilot house between the head and the salon if possible and like Tad's 39, the tankage would go under the pilothouse. If this wouldn't work, then I would place the pilothouse between the head and the forward cabin. This would be the same as Tad's 39 and the only changes would be in the salon area. The location of the engine would also effect all of this. It might not be possible. I just don't know. But it would be a starting point.
I would like to say that I respect everybody's opinions here and enjoy reading your posts when they stay on topic.
Chuck

 

Chuck I do not understand where you get an extra 15,000 lbs from in my example. I chose 35,000 lbs for both boats for a reason. To show the difference between selecting a short boat and a long boat for passagemaking.

 

Greetings,

Post 98 & 101:

Freeboard makes a very huge difference on a narrow boat. Being narrow it is naturally prone to rolling so reducing top heaviness will reduce rolling. Of course you can use other ideas to reduce rolling (waterplane, ballast, COG, etc....) but those are auxilliaries unrelated overall dimenstions which can be applied to a fat boat or skinny boat. People want large wide areas and big headroom which when accounted against seaworthiness are always detrimental to the latters disadvantage when design boats unders 70'.

You have to have an optimum design to start with. The Creator of the seas when giving dimensions for boat able to go through the worst conditions the seas could stir up gave a height to beam ratio at 60%. This makes the ultimate design and is proven when taking 6-1 length into consideration. Others try to give rationale for thier ideas, but those are just arbitrary, when you need a solid foundation to build upon the Scriptures give the answer.

 

Goodwilltoall, that is where I thought you got your ratios from but I wanted you to repeat it here. Just because the minimal suggested passagemaker by Tad and agreed by me is a 6:1 length to beam ratio was not chosen because its in scriptures.

If I am not mistaken your 60% of beam for freeboard is also from Noah's Arc but tell me, since that hight was given as the height from rail to the bottom of the boat and no draft and displacement were listed, How did you arrive at a freeboard figure? Surely you pulled that one out the pie hole.

 

Pierre,

Freeboard is relative to draft, and draft is relative to loading, hull shape, and materials used in building. Do find the TAD 60 interesting.

Everything you see and touch is in 3D, those are porportions you're limited to work with. You can argue all you want and will never come to a better ratio for seaworthiness. As you discovered yourself the 6-1 ratio is excellent for length and width, its just harder for you to comprehend the other one.

 

Let me reply on the statements I highlighted Chuck.

There is a extreme difference in motion between a 40 and a 60ft boat in bad weather. And bad is the weather much sooner in a 40ft than in a 60ft, by subjective perception! So, that IS a issue, because even subjective conditions lead to fatigue.

I was not uncomfortable on that 57ft boat after 300 something miles, I was just "feeling" them in my old bones. (it is not my boat btw.)
What I wanted to express with this example, was the fatigue factor. A 36 hrs watch is not extremely rare on passages in every other than calm or nice conditions. When the boats motion, acceleration is worse than that of the boat in my example, one gets tired too fast. The bridge on that "my" boat is a bit high, but not too high to be a issue. I have stable sealegs.
If that would have been a 40ft vessel, I would not have thought about doing the trip single handed. It would of course not have been impossible or technically unsafe, but it would have been too much stress, fatigue to be a safe passage. I had waves just up to 3 meters, nothing a rugged 40ft boat could not easily deal with, but not really safe for the crew, one crew in this case. I am not talking about trips and conditions one can survive, I am talking about enjoyable boating in safe and stress free conditions, regardless of the weather (to some extend).
Last December I made a transfer trip on a 30ft something sailing boat, a Forum member bought. We have been three, the daytrips have been short, and the wave heights have been below 3m. Every evening, both of my crew, the owner, a young NA, the other a pro Skipper living from yacht transfers, showed noticeable signs of difficulties making decisions, thats fatigue, a killer.
Sure most forum members would like to focus on plain technical aspects. That is easier to grasp and everyone has a opinion. On top of that, not even 1 per thousand plans to purchase such boat, let alone sailing it around the world. But fact is, that the human factor is the dangerous factor in sailing. And a uncomfortable boat is a unsafe boat, no matter which low level of comfort one would personally call sufficient. It is not the nice wood veneer on a bunk vs. a plain matress on the floor, it is the boats motion in bad weather and the possibilty to find sleep on passages. Ease of operation, comfortable service access, safe transition through the accommodation etc. As Tad himself agreed on, his 40ft design does NOT fit the bill, and was not thought to do!!!

The engine room is not a nice gimmick, it is a MUST on a blue water boat. The "diesel cage" may provide access to all systems, but it never is fast and/or easy and safe enough to fix a problem immediately. And problems occur only at 03:00 in the night, in force ten conditions and above, and half way between Pitcairn and Ushuaia. Of course with one crew already injured and in the bunk.

After all it boils down to the size I always mentioned, and to much more, than one would need to just "survive" a trip.

Regards
Richard

Goodwilly stop yur dumb drivel please, it is enough!

 

Goodwill your hubis is amusing if nothing else.

 

You should stop your premature drivel amateur, because there is no way that you understand what we are talking here. The term "Passagemaker" is a clear one, and that was pointed out quite often by now. You anecdotal (and often just lied) stories are as inappropriate as your repeatedly mentioned sailing boats.
Your claimed expertise was proven false on every other post you made here by so far. You are at best, a vague value when it comes to sailing experience. I am not.

And do not make the mistake to attack my business! I can get uncomfortable on that, there are several hundred people feeding their Families out of that!
I have no intention to build any vessel described here, on top of that.

Richard

And that is bs again. There is no need for twin propulsion, and no need for the entire megayacht inventory. Nonsense as all your coments.
Dashew btw came after Tad, and is by no means the minimum, it is quite the opposite, just for the records.. Layman!!

 

Pierre,
I thought that you were making a comparison to Tad's 39 at 20,000 lbs displacement. That's where the extra 15,000 lbs comes from. I totally agree with you that if you keep the displacement the same and go to a longer hull your efficiency is going to go way up and you would use less fuel at the same boat speed because your S/L will be lower. Your 38 LWL at 35,000 lbs would have a Disp/L ratio of 284. The 55 LWL boat would be 94. That's a huge difference. The Disp/L for Tad's 39 is 164. So it would fall between your 38 LWL and 55 LWL. We all know that boats with lower Disp/L ratios are easier to push through the water especially if they are narrow for their length. Your 38 will max out at about 8.2 knots and your fuel usage will increase dramatically as you approach that speed. You know that. The 55 will max out in displacement mode at 10 knots and traveling at 7.4 knots will have a S/L of 1. This is equivalent to Tad's 39 traveling at 6 knots. As you stated your 55 will need 500 gals to travel 2400 miles whereas Tad's 39 will only need 400 gallons to travel the same distance because it is lighter. Tad's 39 with a 650 gallon fuel capacity has a 50% safety margin. The passage will take about 2 days longer in the smaller boat. No big deal.
There's no dispute that 50' plus boats if designed properly and manned by crew that know what they are doing can safely cross oceans. My understanding of this thread is to explore the possibility that a smaller vessel can make similar passages. Again assuming proper design and knowledgeable crew. I personally think that you reach the limit around 40' because of the amount of fuel that has to be carried. That's just my opinion. And I am equally confident that someone will do it in smaller and smaller boats until it becomes nothing more that a publicity stunt. I don't think that's what this thread is about.
I use Tad's 39 as an example in my posts because IMHO it is the best example of a minimal passagemaker that I have found. It's not perfect but there is no such thing as a perfect boat. They are all compromises. I am sure that there are others out there.
Chuck

 

Tad's PL 39 footer is a very logical, easily driven hull with decent interior volume. I would question its ability in the ocean. The secret of sailing yachts working at sea safely, is their nimbleness...steering. A sailing yacht is like an olympic boxer ducking and weaving to reduce the effects of his opponent blows. A motoryacht has no maneuverability...its a World Wide Wrestling champ climbing up on the ropes, body slamming the deck. Different approaches to seakeeping. Small yachts must be nimble. Tads 39 footer has a small surface area ,skeg hung, prop wash effected rudder. It will be difficult for the rudder to get a bite and bring the bow of the vesssel back on track in a seaway . If I were the client, I would request more rudder power to give both the helmsman and autopilt better steering control. I forsee blisters on my hands as I struggle to keep that PL39 on track when downwind, and reaching in a seaway.

 

You've never been on a motoryacht have you? Motoryachts don't reach, that's why they are called motoryachts not sailboats.

 

Chuck the 60', 55 foot lwl boat will max out in displacement speeds at closer to 15 knots not 10 while Tads 39 will max out around 10.6 knots. Theoretical hull speed being 8.26/(D/L)^0.311

According to my caclulations Tad's 39 at an S/L ratio of 1.2 will burn 570 gallons on a 2,400 mile trip at 7.2 knots and take 2 days longer. She would be out of fuel before arrival as she only hold 600 gallons or about 570 useable. That is 70 gallons more no matter how you cut it. She would need to slow down to 6.5 knots in order to make that range safely. At that speed she would need 370 hours and would wallow even with flopper stoppers.


Conversely you could speed up the 60' boat to 10 knots with the same engine as the 39 has. She would need 800 gallons and do the trip in 240 hours. With 1000 gallons of fuel she would have plenty of range. She would also wallow much less than at 8.9 knots and may not need the use of flopper stoppers.

Where the longer boat would really shine though is in skipping that 2400 mile leg to Hawaii to reach the south Pacific in the first place. The 60 footer would easily do the leg from the Galapagos to the Marquesas, a distance of 3100 NM. Because she would have current and wind to favor you could do the trip at 9.25 knots. She would do that trip in 335 hours burning 780 gallons of fuel. Once more she could come back along the route around 4 degrees north a 7.5 knots. With that fuel burn you could air condition the pilot house during the hottest part of the day and cool the sea births to get some sleep.

You can't do that trip in a 40' boat so you will have to travel thousands of extra miles in rougher conditions all without A/C in the tropics. All that means higher costs and far more miserable conditions not to mention the increased safety as a bargin.

The whole idea of a poor man's passagemaker is the lowest overall costs. Lot's of range also means buying fuel in cheaper places and taking longer direct routes.

 

Thank you for that!

Not that we need any further proof of your "expertise", you provided quite much in the past few weeks.
"Motorsailors are for inshore waters only" was by so far the best.
But "A motoryacht has no maneuverability." is by some magnitudes better.

Obviously, CDK, Gonzo, PAR me, and several other senior members are dead right about you. Layman.....

he has never sailed on any boat, that is quite clear, but has a mouth a big as it can get.

Obviously you have some miles under your belt.
The speed I mention soo often as a requirement for such boat is ever so often called unnecessary. "I am not on schedule" was one of the premature replies.
But fact is, that speed, hullspeed, can save fuel (as your little example has pointed out), makes passages possible which otherwise would be not. And makes a ride much more comfortable, hence safer. The often used SL 1,2 figure I would not use when calculating any distance or consumption. That is not realistic, and on top of that, is consuming too much. A SL of 1 is the figure for passages, then a everyday average mileage becomes more in line with real world data.
The stabilizing point is another issue well noted! As faster as I can move, the better for stabilizing the ride. On a 9 year trip, going almost three times around, I switched off the hydr. stabilizers for most of the time, it was not worth the extra power and drag, due to sufficient speed.
In general the speed achievable is much, much overestimated. see:
boat speeds

Regards
Richard

 

Someone else beat me to the punch. You may have lots of experience at sea but your experience is in sailboats. I can tell its not in displacement power boats. Maybe some experience in semi displacement or planing hulls but not displacement power hulls.

Although you seem to have some experience sailing you have trouble relating that experience to boat design sail or power. Your experience seem right but your conclusions relating to boat design are often off the mark. None the less your input is welcome in my opinion.

I am probably off the mark too more than I care to be.

 

Well Pierre Ive brought shallow draft motorsailors, with skeg hung rudders, across the ocean, And I can state as a fact that they are so difficult to keep on track that no human on the helm could maintain the energy and attention needed to hand steer. . We autopiloted the last vessel all the way across. As you know Pierre an autopilot is a dumb helmsman , unable to get in syc with the wave trains. It was a rolly, rolly and more rolly..hard to sleep, .milk turning to cream before you could add it to your coffee, type trip. Effective human driven steering is a very good attribute for ocean crossing small craft and greatly increases the comfort level of those off watch . Look at any modern oceanic small craft and you can plainly see improved steering detailing. Remember Pierre, one of the prime reasons why a sailing vessel has a better, less rolly ride and requires no flopper stoppers at sea is because the helmsman can keep the boat in the wave cycle with superior steering gear.