Modular Cruising Catamaran

John,
I am designing also a modular catamaran. I have to agree that if you build a cat or any boat or anything that is strange in the present world, you have to look at it as R & D and it's most likely that if it becomes a beginning of a new area design, chances are it will end up in museums or used as beach flower pot.
In architecture, with a white page in front of us (not copying any renaissance BS ...) , we are confronted with the famous form follows function or vise versa .(could be vice versa ...) .
The key here is what do you really want to do with your life at this stage of it.
Your program is similar to mine, in early 50's and retirering soon. Who wants to put his money into a fish hole (being in Canada on ice ... ) and then go to the super market and stare at the whooping 20% discount on toothpaste. Another fact , is who are you sharing the idea with ? If a boat cost you 50000 $ and 500000 $ divorce , you will not sell it with profit ...
Make sure your design will reflect your true minimal confort, safety (sped being safety up to a point) , flexibility, budget (unless you want to call it MS Virgin...) , etc.
If this can help, i list some major design criterias that i am working with.
1 - most injuries in a boat occur from falling, falling, falling. Either an object is falling on you or your falling on it. Especially with osteoporous ... should i say old (yes we are) age fragilities. This will greatly affect your finish and insulation decisions (floors, ceilings, walls)
2 - modularity : transportation, marina slip costs, repair ease, build ease, unsinkability, building costs (likely), to name these.
3 - materials : easy to find (plys, epoxies, etc) you may find motivating to go to Kurt Hughes multihulls web site. Most of his thoughts reach mine.
4 - nature's laws: vapor barriers, air-heads (for example) ... , fire (for example: would a sprinkler system be used as an AC and heating (with water storage))
5 - Center Of Gravity (COG) : This subject is complex. At the end of a sailing day , the COG of a cat is different from a Tri, Mono, Proa. It is also different in some ways (stability) between a motor cat and a saling cat. I know sometimes one likes to be on the wrong side ... but on a cat, the weight should be in the pontoons (amas) and as low as feasable possible in them.
An extreme cat is the "hydraplaneur mediatis" mr. Parlier's design criterias were extreme but it shows the "other side of the moon" . Motivation for innovation.
6 - Living : canadians have basements and the first thing my wife (i agree) told me was the she doesn't want to live in a basement, so the typical monos, and the live in tne pontoon is simply out of the question.
I have some more but i got to run.
"if it looks right it probably is "
Later
Mike

 

I agree Mas. And I think that, although this is a free forum, the moderator should work a little bit more than he/she actually does.
I'm not talking about banning persons but simply about deleting messages which are not pertinent to the topic, being created simply to offend.

Freedom of speech should stop where insults begin, imho. Or otherwise we will end up with persons just chasing and punishing each other's mistakes on various topics, spreading their poisons through the whole forum.

We have a person here (ImaginaryNumber) who has asked for help about his idea to construct a modular cruising cat. He has also given us a pretty complete list of specifications, which can be read here:
http://www.boatdesign.net/forums/multihulls/modular-cruising-catamaran-28446-5.html#post288929

Couldn't we all (means - you guys ), from this point on, just go on with the technical discussion pertinent to his requests?
I think it is a pretty challenging list, and would love to see how will all the competent persons present here undertake this design challenge.

Cheers!

 

Imaginary Number
If that can be helpfull, i would order the dvd from Kurt Hughes Multihulls .com , he is in Seattle.
i did order it in vhs and in dvd ... it will give you an insight of work details with ply epoxy. I met a fella in Marina Gosselin on the Richelieu river in Quebec, his name was Michel (i misplaced his card) , this gentleman built a Kurt Hughes design cat, he could perhaps help you ou direct you.
So far, the closest best (i dont really know) place to buy boat DIY things is at Noah's boat supply in Ontario. The canadian dollar going up may change buying strategies.

Your requirements are similar to mine only in the modular aspect. I am pretty sure the two 9,9 hps will not be enough. Especially with windy conditions or currents conditions. I would consider minimum 2 x 40 hp (4 strk) with the most powerfull pitch you can get. If you plan to run aground at times, consider an aluminum prop or the carbon fiber sold at West Marine. I would avoid stainless, it gives little chance to the shaft on small hits, my neighbor learned it the hard way. I have seen and tried twin jet propulsion on a 45ft cruiser , he was also running aground at times in low tides (we all did) and he says he saved $$$ using jets turbines instead of props. . I don't know and i don't want to start discussions with my other neighbor who is a Seadoo engineer ... not yet anyway.

 

One thing not covered yet? but which in the end influenced my "individualistic plans" was RE-SALE-ABILITY... What happens if need is changed because of a stroke or whatever and one needs to sell your much loved ex-toy / pride-n-joy? If it looks "normal" it will find a buyer who may also appreciate some additional features - so long as they do not encumber the product with lots of caveats....

 

Just yesterday, I posted this bit over at Sailing Anarchy, dealing with homebuilt boats and the business of resale value.

"If it's sweat equity that drives the equation, then forget about building your own and also buying new. Getting your hands on a fairly clean used boat where a good deal of all that has gone into it is amortized away as depreciation, is the way to go.

In this economy, especially, this is the single most cost effective method for getting out on the water as quickly as possible. This is about getting out on the water, is it not?

Building your own has to be mostly about the joy of doing it yourself and the inherent pride of ownership. Otherwise, after you pencil-out all the labor, as you mention, as well as the rent for the space to do the build and all the various costs for materials, etc., you're not doing yourself any favors. And yes... your personal garage has a square foot value as it is incurred in your house payment, overhead, etc. Whatever it was formerly used for before you start to build, you will not be using it that way until that multi-piece boat project gets out of the way.

All said in the interest of fairness, even though I provide plan sets for home builders. There's just no way around it. You simply gotta want to make your own boat more than the numbers say otherwise.

If your hobby build time is carefree and totally devoid of time/value consciousness, as a really good hobby should be... (In fact, a really good job should be that way, as well, but not many of us can make that claim) then you are off and running and can focus carefully on doing really good work, rather than really fast work. At that point, the whole vision of making your own boat for exciting, waterborne adventures comes fully into view and the calculated value of your time is a moot point. It's your boat, who's rushing you? OK, OK, don't answer that one, as someone is sure to tell you at some point to get the lead out and give back the garage... but you get the point. The looming question of needing to get your sweat back out should you sell the boat is also much further down the list, as it was already fulfilled during the joy of the build.

There's a larger question in all this that has to do with our societal "rules" regarding getting your value back on resale. For me... if I have to get all wound-up about how that coinage is coming back to me, if and when, I sell the boat... then I feel that I've done, or will be doing, the project for all the wrong reasons. We're talking personal, hobbiest, homebuilt stuff here and not a product that we produce for a profit that supports our style of life. Do any of you have the same concerns about the possible resale value of a tablesaw when you want to get a new one? Didn't think so... and the relative costs involved are virtually irrelevant to me, as I plan to keep whatever boat I do build for a long time.

Maybe it's just me, but this whole thing about the resale importance of a self-built boat is entirely overblown. You guys, of course, can make your own decisions on the issue as it presents itself in your lives."

Working in still photography for over 35 years, with a specialty in architectural imagery, I see a load of custom-built homes every year that have been modified by the owners after they move in. Some of these alterations run well into the hundreds of thousands of dollars and cover things like spiffy garage/shop mods, outrageous landscaping, etc. This stuff is done for the pleasure and purpose of the owner and quite often, they get nothing of value in return for the changes when and if they sell the house in the future. The dynamic variability of this process is too complex to get into right now, but suffice to say, there are many forces at work, globally, that can change your financial plans in a very short period of time.

I do recognize that there might be a cut-off point where the total cost of a boat is such that some inherent value, after the fact, could be substantial. For that kind of project, as it looks to apply to your current build, Masa, I do see the argument you present. For the types of projects that most of the rest of the guys here will engage, there has to be something quite different going on in the decision making process of spending say, $20-$50,000, for instance on a personal boat for pleasure.

If one of us were to spend that much on landscaping at our homes, there's no real expectation that it will come back in the form of a house sold at a higher value as reflected in the "improvements" we have made. It may help to sell the home as a perceived bit of curb appeal, but the new owners could just as likely tear it all out and put in a drought tolerant environment the day after you move out. So much for the $50K of expected returned value.

Value is a tricky thing, as most of us know. If nobody buys the thing in question, then it has no value. I don't care if it's made from aerospace modulus fibers, alien foam and satellite grade epoxy, no sale means no value... period. Just as the quick sale of a nicely built wooden boat indicates that it has all kinds of value, it is much more about who trundles along in the mood for what you've got and not about what that boat is made from.

My opinion is that it's much better to build it based on desire, use it in the same fashion and forget about how much might come back out of it, should it be sold for whatever reason. If the possible hit of a near zero sale is too much for the owner in question, then perhaps this person ought to not get strung-out in the process from the beginning. Boats and boat owners are fickle characters.

One look about in the real estate markets right now will teach one to never assume that the thing that you bought will be worth anything like your expectations when it comes time to sell.

 

daiquiri, No No No definitely not yes, Jeff has enough on his plate and leaving it run its course is the best.... Look at the stuff up governments make by interfering and "equalising"... Just don't read the ******** posts - I don't even use the ignore option as sometimes there may be a very useful point that one could have otherwise read...

Chris, you are throwing a lot of new considerations into the light, and in the broader context very valid - I know some folk who consider "the build" their interest and some where the quality of the build is marginal to be polite, but only want to get out on the water as soon as possible and stay there... and millions of other flavours as well...

Most are content with the expected resale value of a cared for tool (here it is about 50%), but a boat that cost in excess of AU$350,000 is altogether different, and I would hope for at least materials and costs for a product built to a respected designers satisfaction/approval. and my boat is 39ft plus a bit...

In the decision making process all factors should be carefully assessed and do not let the dream be the controlling factor, just the gently directional guidance...

 

So, now where are all our Cat specialists? All the guys which have been so quickly responding to posts not convenient for them.

Where is your experience? Your advice, offered with a full mouth (too full I assume)?

This was from 26th of the past month:

There has one being argueing here when a reply did´nt come within 24 hrs. Where are YOU now?

So, get your legs up guys............

 

Don,t be so impatient, and I am no "expert", some things are achievable without too much difficulty...

My build could be done in halves and joined elsewhere then final painting and rigging,,, but I would not recommend it as some serious engineering and how to join effectively to distribute loads would have to be worked out... Got lots of spare money could be done I guess, but the cheaper option would be to buy / rent a shed and build nearer launch point... Building in epoxy (and probably other glues) has difficulties in cold climates so a heated shed may be appropriate - (It is a right **** when the epoxy does not go off - just a very difficult and painful task to remove all evidence)

So my suggestion, seeing how the project is being done by "older people" may be to build further south where there is no need to heat the shed, and sail up the coast (in the fair weather season) to get to your cruising ground...

If you must have a collapsible boat get a proven design as the engineering loads are significant and complex... some of your boat specifications are too complex for older people cruising... The bi-rigged schoinning came in a burst of publicity but seemed to fade - leads one to speculate on some handling issues? for the older to handle.... Your cruising range alone will present some problems - heating and cooling (read money and weight of unused part and fuel) - 6inch thick plywood - are you nuts or is that a typo? as a box girder - go find a competent marine (CATAMARAN) engineer... Aluminium comes into its own around 40 ft and overlaps with DuFLEX which is good even for the dingy - have a look here http://www.duflex.com.au/duflex/amateur

To carry 6 months stores look at nearer 40 ft and (5500kg = 12125pounds) 5000 to 6000kg minimum displacement ready to cruise, so long as you can live sparsely and frugally... decide galley up or down... Forward or aft cockpit (for sail handling, including reefing and battening down in the event of some failure) - I am using a hitch-hiker rig of 2 genoas only on roller reefing/furling - NO MAIN...
List all the stuff and WEIGH it can you live happily with that?... Electric anchor winch?... Paper charts... Mag compass... Genset location will be a problem... Jibeing is a **** of an idea for oldies... What do you want 2 sinks for?... You have too many different fuels!... how much will you carry? A full size chart table???... mini-keels are OK if you are not racing and will "protect" rudders & screws... Windvane steering NO - reliable electric/hydraulic autopilot... I will carry 2 x 30M2 sails (about 645 sq ft) and weigh 4500kg... Bookshelves (books are too heavy) a stacked shopping trolly gets close to 2000 pounds.... Go and look on the web at as many layouts you can find and realise your limitations... You need a freezer... your stove can be 2 burner but that means carrying gas bottles as well, (fire-extinguishers) - do lots of homework, count and record the food you use over the next 12 months, what stuff you need to have and weigh it... Start another post in 6 months time or buy a well found boat - - - GET A RELIABLE SURVEYOR TO CHECK IT THOROUGHLY... money well spent...

 

I just got back from sailing my catamaran here in hot and sunny BC, so missed a few pages of this thread.

I see Imaginarynumber wants to use his boat in the PNW.

I was talking yesterday to someone who lived on board his 38ft Horstman trimaran in BC for 8 years. He was telling me about the time he was iced in up Tod Inlet.

He is a member of the BCMS. Maybe joining that association would help you contact cruisers with the experience of multihull sailing that you are seeking.

You may also like to contact Garret Hennigan (time for a catamaran adventure . com) who, with his wife, home built his modular 28ft Gypsy and cruised the same area as you plan to. He did overload his boat though with lots of "goodies" and later agreed he would have been better starting with a 34ft Romany.

As I wrote before, you CAN build a bridgedeck catamaran in sections. What I think would be a mistake is not using the hulls for accommodation but only for storage.

Using your graph paper sketch a boat 35ft long with 4ft freeboard. (The hull sole will be about 12in below the WL, so that would give you 5ft headroom in the hulls. Clearly if you have any more than 5ft you will definitely be using the hulls for accommodation.

Then draw a line for the bridgedeck clearance at say 18in about the WL (2ft would be better though)

Then draw a line 6ft 6in above that to give you standing headroom in the central cabin. Then try and make it not look like a box. I think you'll find it will look much better if you raise the freeboard, or add a step in the cabin side or have a raised topside.

And thus you'll probably see why people don't actually draw the boat that you would like.

Hope this helps

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Hello All:
That was a bit of a blow we just had. Thanks to all who weathered the storm and still wish to continue sailing towards the original destination. Thanks for all the helpful posts. I’ll comment on some of them below, but I hope that there will be more discussion on my two basic questions – a modular catamaran with bridgedeck-only accommodations.

Richard Apex and Ad Hoc:
I’ll save learning Delftship for when I have a year or two to spare. It appears that Sketchup is more tractable.

Yellow Cat:
You’ve mentioned a number of interesting points.
Falling: One reason for a flatter-sailing catamaran. However, a large, open bridgedeck can also be a problem in rough seas. I’d like a large open work area, yet also recognize that narrow, confining passageways can reduce injuries.
COG: Yes, having as much weight as possible in the hulls is best, so putting all the accommodations in the bridgedeck is working against stability.
Divorce: Not in the list of requirements, and, hopefully, not one of the inevitable compromises.
Noah boat supply: I’ve purchased plywood from them. IIRC, they have both US and Canadian distribution addresses.
Outboards: After I posted “9.9 outboards” I realized that they would likely be too small. Good ideas regarding aluminum or carbon props, or a jets. Please feel free to share more of your modular catamaran design ideas.

Masalai and Chris Ostlind:
Resale value, and build vs. buy, are good questions. In my case, building is intrinsically pleasant. In addition, I’ve not seen a boat with the particular specifications I desire.

Masalai:
Deck NOT 6” thick plywood. I meant to suggest the possibility of making a 6”-thick stress-skin panel for the main load-carrying member. I’m open to suggestions for other options. Also, after I posted my requirements list, I realized that the NET displacement needs to be significantly higher than what I specified, as you correctly pointed out.

Richard Woods:
Thanks for the BCMS and the time-for-a-catamaran-adventure.com suggestions. I also appreciate your designs suggestions. If I could work out a reasonable way to transport a non-modular catamaran from my building site to launch site I would certainly consider your designs.

Thanks all,
John

 

Here’s a crude Sketchup rendition of an idea for a modular catamaran. The following dimensions are for reference only – everything is subject to change. I don’t present this as a ready-to-build blueprint, but because some thought I should get down on paper at least a crude concept – both to make things clearer to me, as well as to better explain my concept to others. It’s the implementation of the engineering details that I’m hoping you folks will help me with.

LOA 36’
Catamaran Width 20’
Hull Width 3’+ at waterline
Hull height 5-1/2’
Draft 1-1/2’, keels not included (I don’t really know what the draft will be)
Masts 32’ above deck
Deck clearance 2-1/2’
Cabin height 7’ (outside dims)
Cabin bury in hulls 1-1/2’
Length of Fore-module 8’ (including foredeck)
Length of Center-module 8’
Length of Aft-module/aft deck 5’

My two primary questions are:

If all the accommodations are in the full-width bridgedeck can the superstructure be designed to have not too high a COG, and can it be aerodynamically designed to not have problematic windage?

Can the bridgedeck be designed to be built in three transverse modules, with most of the work of building the modules and the hulls being done away from the launch site? I think this last feature (not necessarily considering the bridgedeck-only accommodations) might be of interest to catamaran designers whose clientele might appreciate being able to mostly build away from the launch site.

 

I should also have said (as I think others have also done) that I would not recommend the bi plane rig, nor the lack of headsails.

You should think about how easy it will be to get forward, maybe at night and in a big sea??

Also getting on board from a dinghy, from the side when docked, and from bow or stern when "Med moored" (which you will do in the PNW)

Also you want to be able to see both bows and both sterns from the helm station(s)

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Long, long, learning curve - a bathtub toy, as buoyancy is not there (reminds me a little of my first drawing effort... I used dozens of sheets of A3 graph paper... hehehe)... GIVE UP on the "idea" of joining, far too risky... The structural box girders on my build are everywhere and all different sizes... Spend LOTS OF TIME looking at existing boats and plans, and talking to builders and owners - asking all the dumb questions you thought you should not ask, it is accepted by all, (but the arrogant arseholes you can ignore as they would like of you), as part of the learning process and most will be delighted to introduce you to their view... - - - You are not ready yet... look around, go on daysails, make friends, supply a slab (carton) or 6pack of beer as a "sociable lubricant during a sail and enjoy the gathering of knowledge"...

 

I.N.

As I noted before, if you use simple graph paper, then the lines become a simple scale. Measure items from your own house or better still go into a friends boat, measure the size of "typical" room and items, the head, bedrooms etc. Assuming you're happy with the size of the "typical" rooms, then draw these up on your graph paper. Once you have drawn up the "room's" you think you require, or would like, you'll see how small or how large the boat shall be, just as a first hit. Then you can ascertain the deck layout and from that select the hull best suited. Once you ahve have gone through that and you're satisfied all "looks" ok, get nice detailed weights for everything. Do a simple CoG check, to see where the CoG is, and then you can see, from your selected hull, is she floats, floats up right and at a waterline/trim you hope/expect.

Until you've done this simple procedure, you'll constantly be going around in circles and doing "what if's". Once drawn up, many things become obvious...

 

Na also, geht doch!