economical coastal cruiser

To review these 6 pages of posts: there are five specific existing boats mentioned in this and previous posts that at least approximate the design target:

Blue Jacket 24 or 28 (bluejacketboats.com, by Tom Lathrop). Tom sees 6.5 to 8.5 nmpg using an outboard.

Shearwater by Bieker. They see 6+nmpg over a 690 mile trip, using an outboard.
http://www.biekerboats.com/Bieker_Boats/25_Footer.html

WHIO by Peter Sewell (http://www.woodenboat-digital.com/woodenboat/20060506/) that gets 10 nmpg at 10 knot cruise.

Graphite by Will Allison that sees 4+nmpg using a diesel.
http://www.imaginocean.net/index1.html

MJM 29 that sees 3nmpg using a diesel.


Each of the above vessels meet performance predictions of the Crouch method
http://www.go-fast.com/boat_speed_predictions.htm
using "Constant" values about 150.

The diesel boats get about twice the HP per gallon of fuel as the outboards.

The Graphite boat is lighter than the MJM, and that difference in displacement matches the higher efficiency of Graphite over MJM.

Similarly, the Blue Jacket and Bieker's Shearwater are smaller and about a third the displacement, but use half as efficient engines, so get 1.5 times the mileage of the smaller boats over the larger ones.

So I still think that a planing boat weighing about 2500 lbs lightship, 3500 lbs cruising, powered by diesel instead of outboard, should get about 12 nmpg at 12 knots using about 24 HP. Or about 6 nmpg using 24 HP of an outboard.

Of course, one would want some power in reserve, so 50 HP should probably be the actual engine, just like with Shearwater and Liz (the BJ24).

Still, I think that longer is better, and no harder to tow, and so I'd try and design it to be 40 feet long or so, but still carrying the same interior as, say, the BJ28.

In other words, pretty much what that Wooden Boats design contest is all about!

http://www.woodenboat.com/wbmag/designchallenge2.php

 

The diesel boats get about twice the HP per gallon of fuel as the outboards.


The gaggle of car builders with tiny diesels is expanding.

Soon enough we may get efficient diesel outboards , that don't need a derrick to mount.

Will solve the problem of fuel poisoned with PC alcohol that wont even store for a month.

FF

 

I am planning on outboards, personally. That way, as new technology comes along, its just a few bolts to swap the obsolete for the new. The savings on an outboard over an inboard pays for that fuel cost difference.

6 nmpg would make a $300 weekend only $50. That's pretty dramatic! Getting the fuel cost down to only $25 by going diesel... not so compelling. A really good thing!! But just not so compelling.

That $25 per weekend savings would need to repay the costs of the diesel installation, the costs of the elaborate fuel polishing and filtration system, the sound deadening technologies (soft engine mounts, soft shaft coupling, super high precision shaft installation, sound insulation materials, air pathways with sound suppression, ...), the pain of broken running gear when an outboard would just kick up, ...

So while I'd like that ultimate fuel efficiency, I'd be willing to wait a few years for it to be provided in a well engineered package by, say, a Mercury Marine outboard.

 

This thread has turned into a perpetual Christmas Morning, full of wonderful presents. Thanks for the link to WHIO, U4ea32, it's helping me shed some weight from 'dreamboat'. I've never heard of ANYBODY building their own propeller!

I'm going to explore car engines a little more thoroughly now, but I was disappointed to see that Volkswagen's smallest marine engine weights 500 pounds!

Tom Lathrop tells me that someone building his 28' is using an ETEC 90. Interesting.

 

Sandy, I really think your desires are possible (12 nmpg at 12 knots), but as with Whio, the resultant boat will be quite far from ordinary. I think this can be a very good thing, but clearly, the mass market disagrees. That's OK with me.

Rick is very clear on the concept that custom designed props can make a large difference in efficiency, and are probably essential to achieve your goals. They are not all that difficult to create or to source. Many boats use conventional looking props that were in fact specifically made for that boat. I did so on my last boat. Cost was hardly more than stock off-the-shelf props.

The fuel efficiency of gas outboards is pretty darn good. Besides ETEC, the orbital combustion Mercury Optimax, and the Mercury Verado (when at cruise settings) are very fuel efficient at all speeds and loadings, unlike diesels that really have to be at special RPMs and loads to achieve their potential.

 

Like all things in yacht design, props are a compromise. With an outboard, they are more so, because the diameter is strictly limited. For the same reason, you may find it difficult (or at least not worth the effort) to try to custom build a more efficient one. Though, of course, few off-the-shelf ob props are designed for travel at such low speeds

 

Wrong attitude but not uncommon. Designs should aim to optimise not compromise. Consider all the important factors and arrive at an optimal solution. Not just keep compromising on the requirements.

Compromise is a sloppy approach to design. I detest the concept.

The requirements for boats are changing and the the designs need to be redirected. Twenty years ago very few people got too concerned about fuel economy. Now it is a more significant requirement for a raft of good reasons. Would seem a shame to reduce the weight of a boat by 30% by using expensive materials to improve fuel economy then use a prop with 60% efficiency when it could be replaced with one 85% efficient. Surely the optimum result for money would be to save on the materials, build the boat a bit heavier and then spend money on a custom prop.

Unless more people are uncompromising and push the design envelope, as is the case with WHIO, the recreational boat world will be left in the current state where compromise is the accepted wisdom. Just the lazy way out.

Rick W

 

I shall follow the lead of your tone and follow in kind.

Spoken like a true 'expert' with absolutely no yacht design qualification whatsoever. I've tried to be respectful Rick, but the absurdity of those comments ought to give anyone with even the slightest hint of boating experience, some inkling of how seriously they should take your remarks. I suggest to re-read your post and than go away and have a little think about what you've written.

 

You are right about my yacht design "qualification:. I have not been trained in the same school as you where compromise seems pervasive. Although I certainly know at least one NA who is not apt to compromise. I dare say those designing AC yachts are not quick to compromise either.

My education and engineering expertise has been aimed at maximising value through a no-compromise approach to finding optimum solutions. In project engineering that means best return on investment. So decisions are reduced to the determination of life costs against return over lifetime. I can give you many examples how optimum solutions are determined.

Some things that were designed for boats 20 years ago are no longer applicable to the world today. Even large bulk carriers are finding that there is more value in going a bit slower.

Generally the people involved in this thread are contemplating going a little slower than in the past but saving a large amount of fuel. It may not even be an overall economic decision - it could be more conscience. Irrespective of the reasons they should put as much effort into the prop design they choose as anything else and not accept the common wisdom of compromise. The props designed for planing a boat when fuel was plentiful is no longer the optimum choice for the boat contemplated on this thread.

You are suggesting that they accept your compromise of 6.5nmpg at 7kts. They have asked for 12nmpg at 12kts. If they accept your compromise they are going to be a long way off their objective. The WHIO gets 10nmpg at 10kts. Still a compromise on the important requirement but much better than you are offering.

I have no doubt I could engineer a boat that would exceed their requirements for speed, economy and accommodation but it would involve some clever thinking and considering many aspects. One key aspect is the prop design and manufacture.

Rick W

 

No - I'm not... Right from the outset I stated that Graphite was not the best solution for this application:

This is a typical example of the way that you only absorb the information that fits your own (very) biased view on the world and on boats and the people who use and design them in particular. It's true that you and I differ in our opinions on a number of fronts, but if you had taken the time to actually consider what I wrote regarding the compromise of props, you would see that I was responding to the remarks about outboards and custom made props. I was simply pointing out that by their very nature, outboards dictate a compromise in prop design because one of the main design considerations - diameter - is severely restricted.

Regarding your other comments:
1. I don't believe you when you say you know an NA who doesn't accept compromise. If that's what he say.. then I don't believe him either.

2. I would guarantee that every AC boat designed &/or built involved a multitude of compromises.

3. I never suggested that optimum solutions shouldn't be sought. Indeed that's the very reason I pointed out the diameter compromise in regards to ob's. I'm simply stating that along the way, compromises will have to be made.

Reason has failed in the past to convince you, so let me give you a little example. Attached is a pic of a boat that I'm sure you will recognise. Now, we know that the best solution for a slippery little boat like this is for it to be long and skinny. Problem is, if you just built it long and skinny, it'd 'fall over'. So... what did you do Rick.... you compromised and put outriggers on it. Probably would have been less drag without the hard chine construction too... and maybe a little more length would have been advantageous too
Detestable....

Like I said before... have a think about what you are saying.....

 

Will

This is the problem with those that are not naval architects nor trained yacht designers. They know of nothing other than their own little world. They have no concept of what design is, so rather than take my word for it, attached are just 2, yes just 2, (I could use hundreds of quotes, but restricted to just 2 for simplicity). See attached two most often quotes comments about compromise.

It seem the ex chief designer of the UK’s MoD Navy is sloppy…..but hey Rick knows better, why:

I supposed being completely untrained and having never designed a real boat for a client for a fee in the real world before, just gives one a feeling of superiority.

Just like all those armchair amateurs who watch sport and shout at the TV, “I can do better than that…”…yeah must be so easy sat from the comfort of ones own little myopic world. Self-delusion is a wonderful thing.

So, when one cannot demonstrate any form of track record, let alone formal qualifications, one resorts to changing tack in the hope one does not recognise the incredibly weak position one is debating from.

So, lets ignore the difficulties and compromises made all the name of design…lets now call it project engineering, because you don’t want to highlight your own inadequacies. Since to call a design “project engineering” means what…..well you choose, since there is no formal guidance from the armchair amateur, again, from the mouth of a self-deluded person who thinks any form of compromise in design is sloppy.

So ”… but it would involve some clever thinking…" hahahaha

See, only an untrained and severely lacking in any form of technical naval architecture/engineering/yacht design would say such nonsense.


It doesn’t require some clever thinking…I just requires sound logic based upon the known laws of engineering and science along with an enquiring mind. But one who is not educated in such ways would say as such… Just like asking my surgeon how is he going to repair my ACL…ooohh..some clever thinking….!!! Just because I can’t repair it doesn’t mean someone else can’t.

The only thing sloppy here the nonsense that is posted by Rick. People like Rick give boating, especially small boating a very bad reputation with their unprofessional attitude and extreme lack of knowledge. Anyone who read the post above and agrees with Rick is clearly not a professional in the marine/design field in any shape or form and is unwilling to admit as such for fear of ridicule.

 

Wow,

I took a short recess and things got blown up a bit. I'm sure Rick has lots of value to say about a lot of things as I've followed some of his posts with interest if not always with agreement.

However, to say that Whio or any other boat was built without compromise shows a lack of understanding of the boat design process. All boats, without a single exception are products of compromise of one kind or another. The compromise could be speed, comfort, accommodation, seakeeping, safety, economy, beauty, money or a number of other factors that may be important, or not, to the client or designer. In Whio, the compromises are accommodations which are spartan to say the least, a pretty technical build that is out of the expertise of many backyard builders and more expensive than most of its competition. The designer met his goals very well, but not without compromise.

Raceboats compromise safety for speed.
Other boats compromise rough water capability, accomodation, amenities, first cost or operating cost to gain economy.

You want to go 12kts at 12nmpg, no problem. Why not 20kts at the same fuel burn, no problem. Oh, you want to carry along your lunch and another passenger or two and a top to keep the rain off and take a few big waves and you want to store it in your apartment, well, that might be a problem.

Name any boat you like and there those who can show that there are compromises in its design. Compromise is not a dirty word but just dealing with limitations of physics or other real world and human factors.

 

You are INCORRECT here. I considered and tested a whole range of options. The main hull might be unstable but that is not the boat. I have managed to achieve a very stable platform with no compromise in performance for the conditions it is designed to operate in. The twin stabilisers offer little to no hydrodynamic drag, add a little extra weight and a little extra windage. They are the optimum solution. You may view them as training wheels or add-ons but they are a key component of the boat.

The things I evaluated and tested were:
Catamaran - wetted surface up by 26% power up by 40%
Single outrigger - added drag about 10% over the optimum
Inherently stable single hull - added drag about 7% over optimum and very twitchy - almost impossible to board
Deep ballasted keel on slender hull - added drag about 10%
Many combinations of form stability and ballast with keel ranging in depth
Submerged buoyancy with stabilisers - much higher drag - too much to bother with data
Foils on small outboard pods - weed collectors
Wing with flaps
Dynamic stability with relatively large control surfaces - drag of control surfaces always present

The actual V14 boat you have pictured included additional key requirements for weight, length constraint and ease of build as well, over the previous V11 design. I expected this would reduce overall efficiency but was pleasantly surprised. You may yet see flat bottomed olympic rowing shells. More common wisdom about round bottoms down the gurgler.

This video shows hows it gets up goes when pushed:
http://www.boatdesign.net/gallery/data/500/V14_Rick_16kph.wmv
The V11 hull squated but had no noticeable lift.

The previous V11 design was nominally a no-compromise shape constrained only by power level and displacement. It too used the twin stabiliers - the optimum solution on the long slender hull. The version that was built from carbon fbire holds the current world record under human power over a 24 hour period. The V14 boat you have pictured would do even better:
http://www.adventuresofgreg.com/HPB/2008_09_15_archive.html

You do not look at a racing trimaran these days and consider the outriggers a compromise. They become the key hull at speed. When tris first arrived in the modern world the amas were viewed as training wheels. Many people are fashion conscious, which impairs their ability to weigh the merits of various features without preconception.

There is no reason why outboards could not be designed to take much larger diameter props to get them in the 80+% efficiency range for moderate speeds proposed on this thread. The bottom end would be somewhat different to what you see now - bigger gearbox, bigger ratios, more thrust capability, no anti-ventilation plate, power head relatively smaller to the leg, etc They would have the bollard pull to get out of trouble in very heavy conditions with relatively small power.

So while not given all the preconceptions and compromise seeking that seem to come with training as a naval architect, I do have an enquiring mind, am able to work from first principles, am able to test and evaluate data and I have a no-compromise approach to engineering solutions. The V14 boat is the current no-comprise solution for the design objectives. Principally it can be carried in one hand; can be easily car-topped; averages 6kts with my modest 0.13kW output; can be operated in shallow, log and weed infested water with little loss of speed; is very stable and comfortable; is relaxing peaceful exercise I look forward to using each week. It has taken me 8 years to get to its current state and V15 is on the board but that is the nature of learning and seeking the optimum solution - that solution is always constrained by the available knowledge.

Point is if you take current outboard prop as the best there is on offer for the proposed application of this thread then you are indeed compromising.

Rick W

 

AARRGHH !!!!!
Were it not for the fact that I've been up for 36hrs, so feeling a little testy, I'd probably throw my arms in the air and give up....

So, by your own words, the stabilisers are a COMPROMISE. The vessel has insufficient inherent stability in its optimum form, so you were forced to compromise a little in terms of drag, weight and windage.
It may (or may not) be the optimum solution to a set of problems, but to suggest that there are no compromises involved when you've listed at least 3 yourself is a demonstration of the complete absence of logic in what you are saying.

And that your display of arrogance in the matter has coerced Ad Hoc out of 'retirement' ought to make you reconsider my suggestion once again. Go away and have a think about what you've said....

 

Still not enough?

Now... who do you think said that...?