economical coastal cruiser

[Brian@BNE]

Will, i understood Pierre's posts. I used his name and took a few cheap shots (several sins there) in an attempt to inject levity as the thread seemed to be forming ever-diminishing concentric circles and heading for the plug-hole fast.

I generally enjoy both Rick and your posts and don't want either you to end up so teed off that you leave the forum. I think this 'debate' has got down to splitting hairs and a bit off thread. I want to acquire an economical coastal cruiser soon, and comfort will be a consideration. I'd like to see the thread advance.

[Guest625101138]

Originally Posted by Brian@BNE

... I'd like to see the thread advance.

As the next step how about nominating the displacement and speed you would like to do the first iteration with.

Rick W

[Willallison]

Brian - I take your point... I've typed a suggestion that we move back on track a number of times, but I've deleted it each time because I'm so deeply concerned that there will be people reading this who will believe the nonsense that Rick is putting forth.
Just consider the mythical vessel that is put forward every now and again... the one where the customer comes along and says something along the lines of, "I'd like a boat that I can tow behind my small family sedan, that is capable of crossing oceans, with its crew of 6 (in 3 cabins), gets the same mileage as my car, has a jacuzzi on the aft deck, does 35 knots and only costs 25K, etc"
It's often put forward as a fairly extreme tongue-in-cheek example of the kind of conflicting requirements that designers are expected to solve. In Rick's utopian fantasy world, he can deliver it. And all without compromise.
It's such a fundamental and inescapable aspect of design - often a very frustrating one - that I feel an obligation to point out the absurdity of Rick's position to any and all who accept his words as anything resembling the truth.

[Guest625101138]

Originally Posted by Willallison

Brian,
I think you are missing the point of Pierre's posts. It would be a rare vessel indeed where there were not a set of design objectives, of which at least two were not in conflict with each other. The competent designer is one can find the best solution to satisfy the conflicting requirements. Invariably, that involves compromise.
Comfort is a fine example - and I can assure you that the motion provided by many a multihull would score pretty poorly on that front.

The "best" is the best. It is an uncompromised outcome. It is finding the optimum solution within the design space.

You are beginning to understand the difference between compromise, where you have no idea of the interaction, and the optimum or "best" of all possible solutions. This requires knowing and defining to some precision not wishy-washy words like "might" and "may".


Rick W

[Willallison]

Originally Posted by Rick Willoughby

The "best" is the best. It is an uncompromised outcome. It is finding the optimum solution within the design space.

You are beginning to understand the difference between compromise, where you have no idea of the interaction, and the optimum or "best" of all possible solutions. This requires knowing and defining to some precision not wishy-washy words like "might" and "may".


Rick W

That's it.... I give up... your inability to grasp any sort of reality seems to know no bounds. I've been trying to explain to you - in the MOST BASIC TERMS - the difference between optimisation and compromise and you come back with a ridiculous statement like that.
You choose not to answer any of the questions that I, or others have put forth. You are hypocritical in your condemnation of the use of words like "may". That you cannot - and will not attempt to - see that compromise is necessarily evident in every design - including your own - defies belief. You are the worst kind of forum contributor - so single-minded in self-belief that you are prepared to mislead others. You are a FOOL

[Willallison]

Did I make myself clear?

[Brian@BNE]

Before joining the forum i trawled over a lot of it, picking up tid-bits along the way. I joined because I figured there was a lot of pragmatic knowledge on tap and that if I wanted help later I should try and participate sooner rather than later. I can mostly tolerate grumpy old men with short fuses – I am one.

I’ll share an overview of the thought-journey, as this thread I think at its heart is going in a similar direction.

Budget is finite, so low running costs are important. Obviously sail… but

one day I might want to leave Australia’s coast for another coast. Need a bit of size. Probably want closer to 50 ft than 40 ft. That’ll help for av. speed also– I’ll come back to that later.

Ouch, large sail rigs are expensive! Not so obvious ‘sail’ then..

Displacement cruisers. Slow old tubs with deep draft. Lots of thinking about motor sailers. I’ve been in love with the Nauticat 44 etc for a long while but that deep fin keel is not going to cut the mustard in the tropics.

Ok, a cat then. Many points about motion on multihulls including Will’s reminder above. Not to be overlooked!

OK, Dashew has the answer, perhaps, but even the FPB 64 is well beyond my budget. But Dashew might be onto something - a power boat that isn’t power hungry, has shallow enough draft for the tropics.

Can it be done around 40-45 ft so I just might be able to afford it?

Back to the speed. Initially I’ll hop along the cost from port-to-port. Might have to be single-handed some of the time. But I’m not going to go and sleep and have a large working-boat run over me so I need enough speed to get from port to port in one long sleepless stint. I’ve yet to do the calcs. on distances and fine tune required speed, but 12 k might just do it.

My ‘mini-Dashew’ would have a single diesel. I like the straight 6 out of the BMW X5 as its often acclaimed as the best of breed. Yanmar use it in one of their models, so I don’t have to ‘marinise’ it.

I’d like to swing a 4 ft (well, abnoramlly large at least) prop with the diesel sitting at relatively low revs – I guess its 1800-2000 rpm when the X5 is in its economical highway cruise mode – for max. efficiency. My big prop would be for blue-water operation, and lift up when I need shallow draft. Perhaps power could be switched over to a small prop or jet (no drag when not in use) for shallow water travel. But I’m sure that having a big prop that can be lowered ‘on demand’ and take the full 5000 rpm of power if required is going to have a few structural engineering issues to manage.

Now, are there any existing sailboats that could be converted to a 'mini-Dashew' or will it be better to start with a blank canvass and take a long time to even get a hull that I can fit-out?

[Pierre R]

Let's see, if I am taking Rick's approach and optimizing then I certainly would not start with boat design parameters like length, weight or mileage. I would start with what you want in it, the level of comfort you expect from the boat in ride and creature comforts and the real intended use for the boat.

I think these things start to optimize a boat much more so than picking the boat design parameters and then trying to fit what you want into those numbers. I think the later approach is a recipe for playing in fantasy land, not optimizing design.

Its easy to pick number out of thin air and make a boat around them but the end results are ususally not satisfactory to a customer. The reason being is that the customer almost never realizes what is truely practical and that is why they went to an NA in the first place. A good NA needs to educate the customer throughout the process. Having the basics of purpose and expectation of comfort nailed down can help the customer wade through the many decisions they must make.

To me its easy to throw out speeds, displacements, mileage, beam, cubes and a whole host of other numbers but its far more difficult to quantify something like comfort. How do you put a number on it so you can add it to the numbers being pulled out of nowhere?

[Guest625101138]

Originally Posted by Brian@BNE

...
one day I might want to leave Australia’s coast for another coast. Need a bit of size. Probably want closer to 50 ft than 40 ft. That’ll help for av. speed also– I’ll come back to that later.

Ouch, large sail rigs are expensive! Not so obvious ‘sail’ then..

Displacement cruisers. Slow old tubs with deep draft. Lots of thinking about motor sailers. I’ve been in love with the Nauticat 44 etc for a long while but that deep fin keel is not going to cut the mustard in the tropics.

...
Can it be done around 40-45 ft so I just might be able to afford it?

Back to the speed. Initially I’ll hop along the cost from port-to-port. Might have to be single-handed some of the time. But I’m not going to go and sleep and have a large working-boat run over me so I need enough speed to get from port to port in one long sleepless stint. I’ve yet to do the calcs. on distances and fine tune required speed, but 12 k might just do it.

My ‘mini-Dashew’ would have a single diesel. I like the straight 6 out of the BMW X5 as its often acclaimed as the best of breed. Yanmar use it in one of their models, so I don’t have to ‘marinise’ it.

....?

Sounds like you are at the top end of the weight and want 12kts. I have attached the curve showing the lowest drag hull for the indicated length. This shows the cost in terms of power for restricting the length.

If you choose the length you would like to go forward with we can start to talk about stability requirements.

You may want to revisit the length depending on the stability requirements. The doors are far from closed on length yet.

Rick W

[Willallison]

Brian, one solution to the two different props for different tasks, is to use a controllable pitch prop.
On the engine front, the Yanmar 6BY, which is the one that you refer to is the unit that I have fitted to Graphite. It is a lightweight high-speed diesel and is not really likely to be the best solution for a large, heavy displacement boat. John-deere', Luggers etc are more likely to be suitable.
I also agree with Pierre - you are looking at the solutions before you've considered the problems- or at least you appear to be. Size (in this instance) ought to be the result of considering what needs to be contained

[Brian@BNE]

Pierre, i think comfort is a bit elastic. As an analogy you might like the comfort of an S-class but when you realsie the capital and operating cost be quite happy with less comfort.

I'd like 2 cabins that can give enough privacy if someone needs to 'chill' for a bit. Personal space is what some people don't realise is often an important missing element of a boat. Extra people? Convert the dining table for occasional use, its comfortable enough for casual visitors. The other crucial 'boat comfort' elements of enough shade and weather protection won't necessarily drive 'speed, displacement etc' numbers being tossed about. Condominium comfort I think is going to be at odds with 'economical coastal cruiser' and be in the marina most of the time, and on a different thread.

Skinny and >40 ft will give 'reasonable' speed. But no, I don't want to have to hold onto my drinks all the time so I'll take a bit of extra beam. And probably some displacement/draft hits as well. And i don't think i need an NA to educate me and tell me what i need. If I'm paying the bills, I'll find someone who can listen and think. Tell me I'm dreamin'. OK, but isn't a design forum where we can test what might be possible?

[Pierre R]

Originally Posted by Brian@BNE

Now, are there any existing sailboats that could be converted to a 'mini-Dashew' or will it be better to start with a blank canvass and take a long time to even get a hull that I can fit-out?

Now you have the discussion back on track. In a short answer, there might be a sailboat hull out there that might do the trick but I have come to the conclusion that you might just be better off building from scratch. Scary but true.

I have been toying around with long slender monohulls and kind of speced one out around 52' LOA with a 49' LWL, a 10' beam, 4' draft, 11' air draft with a D/L of 135. The boat would be comfortable for a couple but rather simple in systems. With a single John Deere 135hp 4 cylinder engine the boat will top out just under 12 knots and cruise around 10 knots. At 10 knots the fuel burn would be about 4 gph with a range of 2200 NM.

The design I had in mind was optimized to take full advantage of canals, rivers, coastal, island hopping in the tropics and shallow crusing areas throughout the world while still retaining the ability to make an ocean crossing. The boat is also ideal for deck shippment on a RO-RO boat if ocean crossing is not in the game plan.

I think something like this could be built in a few years time using all new materials for just over $300k Aussie dollars if my converter is correct.

The Dashew FPB 64 is not a cheap boat to build at all. When you want that kind of fuel and systems aboard the building time and precision is a real headache.

[Brian@BNE]

Posts too fast for me!

Rick, no attachment?

Will - i dont want displacement to be any larger/heavier than necessary hence the lightweight diesel. I like the concept of CPP, and have wondered if it can be mated to a continuously variable gearbox. Recently on my brothers' farm he demonstrated his John Deere at constant speed (final drive rpm for CPP in my case) with onboard computer increasing rpm and changing gearing to suit higher loads (cultivator going deeper). So the same system could be adpated to a CPP?

I haven't meant to put solutions first, and nothng is fixed yet! I just wanted to provide some bounds - I don't want a 20 ft dayboat or a 100 ft expedition yacht (well, just can't afford to buy or run the latter)

[Brian@BNE]

"I have been toying around with long slender monohulls and kind of speced one out around 52' LOA with a 49' LWL, a 10' beam, 4' draft, 11' air draft with a D/L of 135. The boat would be comfortable for a couple but rather simple in systems. With a single John Deere 135hp 4 cylinder engine the boat will top out just under 12 knots and cruise around 10 knots. At 10 knots the fuel burn would be about 4 gph with a range of 2200 NM."

Pierre those a very impressive specs. I'm not quite ready to move yet, but I'd love someone to run with what you've described so it can get to the next stage. I don't think there is anything quite like it floating around anywhere, is there?

[Guest625101138]

Originally Posted by Brian@BNE

Posts too fast for me!

Rick, no attachment?

...)

It is there. It has already been opened by someone.

This gives the basis for testing what it will cost, in terms of performance, to apply a length constraint.

I expect that your upper limit of 45ft (say 14m) will be close to the optimum for moving along if you agree with that. This is a judgement call at this stage and needs to be narrowed down once there is more design detail on the boat structure.

Is 14m within your acceptable range to consider the stability aspect?

Rick