Modular Cruising Catamaran

This is starting to remind me of that thread from a few months ago with a few of the same players...

remember, we were going to rename it "When Engineers Get Into Knife Fights"?

Now, let's all grab a beverage of our choice, sit back for a moment, and realize that we probably all agree on several key points:
- We love boats
- We're here because we like discussing boat stuff
- If we all approached problems the same way and came up with identical solutions, none of us would ever learn anything or make any progress

Now, we can probably also agree on the following:
- There are some speeds where skin friction drag is a bigger factor than wavemaking drag
- There are also some speeds where waves are more important than skin friction
- These speed ranges will not be the same for any two different boats, or even for the same boat with a different load

And, I think we'll also agree, if we go through and take a look at what the thread starter wanted, that:
- There is little point in worrying about the details of exactly how a hull will be proportioned until we have a clear idea of what the owner/builder wants to do with it
- What the original poster wanted was advice and discussion on the feasibility of building a boat in segments, inland, for later assembly at the shore, and whether a full-bridgedeck configuration would lend itself to this

 

So you can't defend your remarks.

Good to know.

 

Just as you are doing now,... but without all that silly irrelevant stuff, like actual data. Maybe there's something wrong with me, but I like actual data. Don't you?

Why don't you take a stab at defending Ad Hoc's statement, since he has declined to do so? All you have to do is find something in the literature that supports his contention. Here it is again:

For anyone who's wondering why I continue to poke at these silly folk... it's because I would hate to see the original poster take any bad advice from someone like Ad Hoc, who appears to be trolling. His statement above contradicts the stuff naval architects learn in their first classes. Therefore he is no naval architect (or if he is, he's deliberately spreading misinformation) and should not be relied upon for any advice.

I well remember the moment of disillusionment I suffered when as a design newbie infatuated with fast multihulls, I put forward the same notion-- the finer the hull, the less the drag, at all speeds. I actually believed this. It was Tom Speer who corrected me, and helped me to understand the very small role wavemaking resistance plays at low speeds.

It turns out that this is not rocket science.

 

Mr Aldridge we have no real data! Not even the questioner knows where his task will end (in terms of data).
And Mr Aldridge, I do not play with my electronic devices, I use them as tools when sensible! Whereas you make adventureous predictions of a completely unknown design. Unprofessional............

And Mr. Aldridge:

stop telling me what I have to do! You´re not qualified to do so.
John (Ad Hoc) can defend his position himself (and just to peeve you, on a professional level opposed to yours)

Can we find back now (all compliments are spread around I guess) to the topic, as Matt tried, unfortunately unsuccessfull?

Requirements?

 

You're trying to move the goalposts again. Ad Hoc made a general statement pertaining to all hulls. I cited a specific example in which this general statement proved to be incorrect. Now it's up to you or him to cite an example in which his general statement is correct, or even the published statement of some well-regarded designer or naval architect which supports Ad Hoc's opinion. He was unable to do this, and now we see that you can't do it either.

This is actually a significant matter in terms of the original poster's purposes. As I understood the thinking, he wanted a boat with all accommodations in a modular center deck. This entailed the idea that he could make the hulls as fine as he wanted to, since they did not have any purpose that required ergonomic consideration. Those here who actually know what they're talking about pointed out that for a cruising cat, excessively fine hulls have disadvantages, and one of them is low speed drag. For some reason I can't understand, Ad Hoc decided to commit an act of pointless trollery and say that they were wrong. Deliberately misinforming someone who asks for advice is an ugly thing to do.

 

Are you completely nuts? What have I to do with others statements ?

Prove my statements wrong coward or keep your mouth shut!

And who granted you permission to claim a answer within a few hours? Some are working to make their living! (do´nt try that, it´s for adults only)

 

Modular Catamaran Specifications

Here is a tentative list of requirements for a modular catamaran. Probably many of the items on it could be debated ad infinitum. I’m open to suggestions. But the main point of posting this list is to aid those who might be willing to help address two questions:

Can a full-width bridgedeck catamaran be built in sections, then assembled at the launch site?

If accommodations are confined to a standing-room bridgedeck, can the resulting structure be designed to have an acceptable level of weight and windage as regarding boat control and stability?

Unfortunately, my drafting skills are negligible. I am trying to learn how to use Google Sketchup or Delftship, but could imagine that it will be awhile before I am able to produce something worth posting. So I’m hoping that my written description will provide enough of a description to address the above questions. Please ask more questions if my descriptions are inadequate. Thanks

Modular Catamaran Requirements

Where To Be Used:
Cruising SE Alaska and British Columbia (including winter), with capability of cruising to Mexico and Hawaii.
Water and air seasonally mild to cold. Winds light to very strong. Strong currents. Both sheltered bays and open coast.
High tides. Will often dry out.

How To Be Used:
Full-time liveaboard cruising for an older couple. When not sailing usually anchored; seldom at moorings or docks.
Infrequent access to major cities. Will regularly carry 6+ months provisions.

Accommodations:
Two double berths
Saloon: seating at least 6, convertible to bunk
Head: composting toilet, shower, sink
Galley: double sink, stove and oven, counters, food and cookware storage, refrigeration optional
Heater: diesel or kerosene (and maybe also a wood-burning heater)
Plenty of bookshelves
Chart table: full-sized with plenty of chart storage
Open space for working (sail repair, engine repair, hobbies, etc)
Cabin with 2”-4" foam insulation (or equivalent)
Helm in pilot house, or at least very sheltered (standing room)
Standing room in central portion of cabin, shower, galley, and helm

Catamaran Design and Construction:
Owner buildable, owner maintainable
(plywood, fiberglass, epoxy – have some experience with)
(foam composite – have no experience with)
(would prefer Strongall aluminum, but seems too heavy for this size boat – I can weld, but am not an expert)
Hulls and three-segment bridgedeck cabin 95% completed at building site, final assembly at launch site. All components less than 10’ wide
Hull length, ~36’
Hull waterline width, ~3’ to 3-1/2’ (12:1 – 10:1)
Overall Width, ~20’
Deck clearance ~3’
Net displacement 3000 lbs minimum (Net = Max – Racing)
Flat-bottom aft 2/3, then vee-bottom forward 1/3
Tough bottom to tolerate stress of drying out
LAR keels good for drying out?? Daggerboards better for performance
Rudders: skeg-supported transom-mounted
Self-Steering Windvane
Crossbeam between bows supporting anchor

Bridgedeck:
All accommodations in bridgedeck; hulls used only for storage
Bridgedeck assembled from three sections each ~20’ wide by 6’ to 10’ fore and aft
Forward Section: narrow foredeck, two berths in corners, passageway to foredeck hatch, access to hulls
Center Section: head, galley, saloon, workspace, access to hulls
Aft Section: helm station/pilot house, aftdeck, engine pod

Bridgedeck construction ideas (for each of three sections):
1) 6”(?) thick plywood stress-skin panel deck, 20’ wide by 8’long, spanning from outer hull to outer hull; main load-carrying structure.
Light weight, 2”-3” thick, composite panels for walls and roof of cabin; carries little load.
Very lightweight bulkheads supporting roof edges.

2) Deck, bulkheads, walls and roof of each section designed as a large composite box beam.
This might be preferred if typical Bermuda rig used

Hulls contain:
Batteries
Fuel
Water and wastewater
Food
Clothing
Extra sails, lines
Tools
Bicycles
Motorcycle(s)??
Folding dinghy and kayaks

Sails:
Biplane-rig: freestanding mast in each hull
Either split- or cambered-panel junk rig, or swing-wing sail
Each sail ~300 sq ft – total 600 sq ft
All lines leading to helm station

Engines:
Deck-mounted diesel with genset
OR
Two 9.9 outboards, and generator

Tenders:
Rigid dinghy on rear-deck davits
Folding kayak and/or folding dinghy stowed

Anchoring:
Two full-sized, plus at least two smaller secondary anchors
200’ chain, if weight can be tolerated
Nylon rode for all other anchors

Electrical - Electronics:
GPS
Computer
VHS radio
EPIRB
Depth sounder
Log
Cabin and running lights, LED or fluorescent where possible
Storage batteries
Solar Panels
Wind generator

 

Well done! Now we have something to start with.

Regards
Richard

 

Wow, woke up to a good laugh, since that is all one can do at such a narrow minded response.

It is very clear that RayD has the attention span and intelligence of a gnat. He feels that owning a program is all that there is to naval architecture. Since his one line replies reinforce the notion that he cannot comprehend anything other than a one liner. In response to the, ‘what are the limitations of the program’, he clearly doesn’t know and probably doesn’t care and/or doesn’t understand. He probably needs to buy a dictionary to see what “limitations” means, because ”it does not compute”!

He has no notion of simple things like the relationship between L/B, B/T, the length displacement ratio, the effect of Froude number and Reynolds number. Or simple sensitivity analysis like what happens if I make a mono but keeping the same volume and make it a multihull, or if I make the same volume in a long hull and another in a short hull…. not to mention laminar flow, separation and viscous/friction drag just to barely scratch the surface.

But this requires significant patience, reading, learning understanding and having an open enquiring mind. A button pusher has none of these attributes, again the above posts of evidence of this. Button pusher like RayD who have no training nor education in the fundamentals and principals of boat/naval architecture do not want to take the time to learn such things, “these” one liners are simply that. One line one button to press, it is simple. Don't waste my time explaining or trying to tell me otherwise, everything is so simple. So, can’t explain in one line, see…hopeless.

The next time I see my friend/colleague who is a Professor of Hydrodynamics at one of the universities that I occasionally lecture at, I’ll tell him his job is redundant. He no longer needs to teach hydrodynamics, of course he’ll ask why and I’ll tell him, that RayD knows it all. He has discovered the “holy grail” and it is a program by John Winters call KAPER. He can retire as can all the other Professors around the world doing valuable research…

Clearly I have wasted 7 years at university (and continuing) and a further 20 years designing boats. I consider myself to still be learning and shall until I die/retire. But no more!!. All I need is the KAPER program, simple. I shall now throw away all my books and research papers, including ones I’ve authored, and go and buy KAPER. I’ll tell my old Uni in the UK that they do not need to spend years learning/teaching too, just reduce the course to learn how to press buttons on a PC to drive KAPER...it is so simple, it is child’s play anyone can do it….oh, they already have! It has all the answers for all the hulls for all applications…wonderful.

That is the problem with button pushers and those with no patience and a mind tighter than a camel’s *** in a sand storm; they give professional yacht designers/naval architects a bad name. They perpetuate the notion that boats and all fields in it from design to building, are filled with amateurs that do not address small boat design seriously and with education and professionalism and so are just a waste of time and money. They go around proclaiming they know everything that there is no need to listen and learn and understand complex issue, because it is so simple, KAPER!

I was going to spend some time to copy and reference endless papers so you can read at your leisure and further your knowledge, but after the last posts, it is clear that it is a total waste of time. KAPER…the word is KAPER…no need for anything else.

Yes you read it here first. Today the world is in a new order…that order is KAPER! Don’t question it, don’t investigate the limitations, don’t think anything else matters, and don’t do anything other than trust it. KAPER!

Thanks for the comedy RayD. I’ll send you pictures of my Fahrenheit 451 moment in my garden.

Sorry ImaginaryNumber/Apex….lets get back to the thread and ignore those time wasting button pushers.

 

I.N.

"..Unfortunately, my drafting skills are negligible. I am trying to learn how to use Google Sketchup or Delftship,.."

As noted above, don't bother. As a first hit, just use a pen and paper and the paper to be lined graph paper. This way it is simple to scale. Don't worry if things look "boxy" to start with. This is the first step and nothing is exact nor accurate. But using simple graph paper helps you to get an appreciation of size and its limitations.

 

You can't come up with even a single reference to prove your point? Really? That's a little sad.

Here's what you wrote, again, in case you've forgotten:

Are you sure you don't want to back this statement up? No? Personally, I'd advise you to try. Otherwise, folks might start to wonder why a guy with your vast education, training, and experience can't do such a simple thing.

Here, let me show you how it's done, since you seem to be having so much trouble with the concept.

From:

You do see how that exactly and precisely contradicts what you said?

Now it's your turn. Of course, you could just continue with your clever strategy of calling me an idiot. In fact, I'm guessing that's exactly what you'll do, because that seems to be all you and your sock puppets have going for you. Don't disappoint me.

It seems odd to me that a guy who claims to be a naval architect didn't know this about resistance. It's really low-level stuff. Froude wrote about it over a hundred years ago. I'm starting to think you might just be a fraud.

 

Ah, see that's good you can copy and paste now too, you're evolving from just pushing a button. But as always with the button pushers, you look for one liners to satisfy your myopic world.
KAPER....
So are you now going to tell E.C.Tupper that his book is now redundant because of KAPER...it has it all....you have proved that, no one needs to know anything else...KAPER.

KAPER has no flaws, it tell you all need to know Don't question it...sounds like you're almost trying hard not to now though...

Oh for those that can read more than one line from his book:

"Form Parameters and Resistance:

There can be no absolutes in terms of optimum form. The designer must make many compromises. Even in terms of resistance one form may be better than another at one speed but inferior at another speed. Another complication is the interdependence of many form factors, including those chosen for discussion below. In that discussion only generalized comments are possible.

Frictional resistance is directly related to the wetted surface area and any reduction in this will reduce skin friction resistance. This is not, however, a parameter that can be changed in isolation from others. Other form changes are likely to have most affect on wave-making resistance but may also affect frictional resistance because of consequential changes in surface area and flow velocities around the hull."

But using parameters is a function of what a naval architect does....but that requires more than KAPER or pressing a button. So i doubt this is in a one-liner enough for you, too many words for you. Since hydrodynamics is a simple as KAPER and a one liner...great stuff, keep it up. This is much better than any comedy on TV right now. I look forward to seeing all you new theories on the bookshelves now...can i ahve a signed copy from the person that reinvented hydrodynamics overnight

I wonder what KAPER says about changing forms etc...oppss..can't don't ask, it is beyond it limitations and understanding that it is just a generic algorithm....suussshhhh. It is the answer to all our problems, don't upset the gate keeper to everything


PS..forgot to add..that line from Tupper was written during the time of the big conflict in the UK MoD of Short fat ships versus Long thin ships. The short fatt ship lost.

PPS...if you believe this so much why is the only boat you have on your website long and thin..not short and stubby?..it is going very slowly..surely you practice what you preach?

 

I.N.

Sorry i'll keep to the post....button pushers are clogging up your thread.

 

You're the one who disagrees with Tupper and Rawson. Didn't you understand that?

The stuff you quoted did not support your contention in the slightest. Where did it say anything that resembled what you said? It didn't. It was just a plate of copypasta, chosen to obfuscate the point under discussion, not to shed light on it.

What I quoted directly contradicted what you said, and what was so funny about it was that Tupper and Rawson used almost the same locution you attempted in your original assertion... except that they said the exact opposite of what you said.

I think you should immediately send a stern letter to Tupper and Rawson. Be sure to tell them what a prominent naval architect you are. I'm sure they'll take your word for it.

By the way, don't be afraid to use KAPER to prove me wrong. Even if you can't find anything in the literature to back you up, a guy of your stature ought to be able to draw a hull with a few magic bumps on it that will prove your assertion.

Here it is again, in case you've forgotten:

Come on. Tell the truth. It's starting to sound a little dumb even to you, isn't it? The first sentence is redundant, and the last one is wrong. And you still haven't come up with a single reference to support it.

I guess I'll just have to assume you can't.