Tent's up!

A rough sketch of the tent structure. Needs additional crossbracing to resist winds, but it is good enough to illustrate the concept. Zipper openings on the sides to get to the hulls. The tent has enough height towards the rearbeam to accomodate short standing persons or sitting people. Helming benches with mesh seats will be attached to the rearbeam. The central pod will have storage compartments and cooking/washing facility. Collapsable table is easy to build attached to the pod.

HullEvolution

Hulls have grown to 10.2 meters. More lenght for less total hull surface compared to the initial high cabin design. Cockpit a bit too exposed without sprayhood, but that is easy to add. At least the cockpit is a bit more functional, easier to route sheets there and have cleats and winches at hand.

Hold the phone !

Ok, so there's nut much outside input into my project so I tend to have a narrow vision on things and go on a not so good direction, going astray from my first priorities, which are : fast build, low budget, good performance, minimum acommodations. I have realized that I'm currently designing a double monohull instead of a proper cat. Meaning : too much freeboard and height, high CG, high CoE, too comfy acommodations and too much standing height, lots of work to do on the interior etc.

Next I will try to put the money to good use - which is more lenght, less standing headroom, less fancy, less interior fitout, going proper gipsy. Since the core material is allready bought design will have to take into account that and maximise lenght based on a total SA. Keep close.

Fresh from the lofting table

Bigcat has gotten bigger. New hulls are sleeker, finer, allow for more payload, better tacking due to a bit more rocker, substantial volume in the bows and a bit less at the stern so it keeps the nose up with ease.

Back to the drawing board

After receiving all the core materials I decided to elongate hulls to 9.2 meters, add some rocker too, just a few cm, lower the cabin height and edit some other cosmetic aspects. New hulls will be ready soon. The longer platform is just a safety measure without enlarged rig. The rig choice is still blurred. What do you want from your driving engine when you're in the middle of nowhere ? Reliability, easy to repair, low consumption. I guess that describes a basic diesel engine, how to translate that into a boat rig ?

Given the size of the cat and the type of sailing intended I assume a low CoE would be highly desired, this boat's trim will be highly influenced by waves as it is short, unless a cat rig is way underpowered I think it will be unsafe surfing down waves with it.

The hull design is intended to be a true monocoque no edges or kinks, the intention is to have almost every surface with double curvature for added stiffness.

Rig candidate, maybe...

http://www.stay-rig.org/

To foam or not to foam...

Not much done these days, but at least I got something out of the way. Looks like the boat will be foam composite afterall. I'm very happy about that, it should be a faster build compared to strip plank, relatively lightweight and pretty stiff without much interior structure. It is also possible that the hulls will be stretched to 9.2m, cat rig is still under debate, but my favourite at the moment. Since the building materials are settled the latest hull design will take foam into account.

RudderSetup 2308

First rudder setup, currently a cassette type. The nice thing about transom hung rudders is that you can easily modify the setup from cassette to kick-up. Hulls went on a diet, too much standing height and too fat.

Rudder setup and KISS

I wanted a transom hung kick-up rudder setup, for easy servicing and replacement, if needed, also much better if high aspect compared to an underbottom post mounted rudder that would normally be low aspect. If a high aspect post rudder hits something (and it will) something will brake eventually, so a post mounted rudder would desirably be low aspect to minimise that risk. But, I don't want to minimise that risk, I want to eliminate it. Transom hung is not exactly up to the KISS principle, it has some moving parts, pins, slop, and it is more difficult to make. Is it worth it ? Another issue is that my transoms are pretty high, and cockpit not exactly very close to the transom, that means the tillers will be pretty long and awkward, that is good for helming though, as there will be less force required to swing the tiller. The foils will have to be pretty long too. It is a challenge.

TransomSteps

Added transom steps, not exactly pretty but functional. Will accommodate transom hung rudders soon.

Cockpit 2008

Yes, modified again. Having the entry hatch centered on the hull is definitely a NO. Makes the space behind that bulkhead very hard to access. Having the hatch placed longitudinally but offset from CL is messy, needs and asymmetric modelling of the deck superstructure, ugly. I returned to the original setup I was previously considering, however adding a recess to make the inside dryer from flushing waves. I think this setup will remain, maybe improved, but having the hatch longitudinally placed does not fit well with everything. The part of the trampoline close the the hulls will be non open type, some kind of vinyl or similar, this will make the ride dryer, both for the cockpit and for the inside of the hull. The more transparent trampoline will be mesh type. Also eliminated the hard cockpit seat replacing it with a mesh seat - this will flush the water rapidly adding comfort during the ride, it is also much more ergonomical and less sensitive to heeling, as opposed to a hard seat. I like the winch placement but working the winch will interfere with the tiller unless I come up with a solution. Also only one winch might not be enough.

Cockpit 1908

More work on the cockpit area as I'm still not happy with it. I'm a bit more content with this type of setup. Towards the entry hatch the cockpit seat has a sill and a protected area, usefull for a dryer inside while the waves are flushing the cockpit from the transom, also usefull for storing stuff during nigthwatch so it doesn't bounce around, stuff like peanuts, snickers, waterbottle, portable radio etc...At the moment the entry hatch setup is centered on the hull, I like it, but it makes the aft berth hard to access, will probably offset the setup so there will be easier access to the aft berth, making it assymetrical, again. Added gennaker boom. In order for the mainsail fairing sock to work I will have to move the attachment points of the shrouds near the mast crane, currently drawn about 1.3 meters below mast crane. Will also add transom steps and will need to draw up rudders and rudder castings. Cockpit seats 2 people on the 120cm seat.

It is good for me

I'm still in the process of comforting myself with choosing this rig setup:

"Any rig her owner likes to work is the best rig. John G Hanna"

Sailrite on cat rigs

This is quoted from the sailrite webpage ( www.sailrite.com )

"Cat Rig and Battens

Finally, consider the rig appropriate for these high-speed boats. You will have noticed that most high performance catamarans have a cat rig. This follows from our discussion of aspect ratios. The sloop rig tends to spread sail area out, in effect, decreasing aspect ratio. That sloop rig will make possible more power, but it will cut down the potential speed of the boat. If the boat is so easily driven that this power is not required in order to get it moving, it is best to place all sail area in a single, tall sail.

One more thing: high-speed sails should have full-length battens. These battens are tied into the sail with enough compressive force to bend them into the desired shape. As a result, the sail becomes so rigid that the sail must be "popped" from one side to the other when the boat is tacked. This rigidity holds the sail in shape in spite of rapid acceleration and deceleration and in spite of the abrupt apparent wind shifts, which accompany those changes in speed.

The rigidity imparted by the battens also lets the sail operate at higher angles of incidence than would otherwise be possible (see Marchaj's Sailing Theory and Practice, page 70). Once again, this can be very useful on a boat that moves the apparent wind well forward just because its own speed is so high. The power developed by such a sail will be relatively low, but its potential speed will be very high.

There are, in conclusion, no secrets in the building of high-speed sails. They are simply the result of extending the same lessons we have learned with "normal" sail design."

CE, CLP, SA

Currently having 33sqm of upwind SA. Mast is 12m long, needs to fit inside a container, it is also possible that it will be a collapsable 2 piece mast, however wouldn't want it longer. CE is aft of CLP by aproximately 6-7% of WL. Theoretically it should currently have a slight weather helm. I want a trackless mast, mainsail luff will be on a wire and will have a fairing sock around the mast, that is why the boom is not attached on the mast, don't want it to interfere with the wire. I think the main will be easier to reef if the luff is on a wire, less stuff to break or jam, less efficiency though, but hopefully the sock setup will work and draft from the mast will be reduced. I'm not looking for a maximum efficiency rig, just a simple one with less stuff to break or jam, easy to sail single handed, less hardware, cheaper. There will be some flying sails for downwind work.

Also modified mainbeam, simpler, still sufficient clearance under the beam, checked local suppliers and largest round Alu extrusion available is 100x4, so beams will have to be made from wood/carbon, probably won't need bow foil, will add gennaker setup soon.

HullShape 1108

Modified hull shape, symmetrical hull, asymmetrical deck, clearance between rear beam and designed WL is around 90cm, more than the Radical Bay 8000, but still a bit low. Hulls are fatter but WL beam is just 1cm more, WL to BWL is almost the same, almost 13. Next thing that came to my mind will be to further move the cockpit seat towards the trampoline, amplifying the aft berth space. Under sail the cockpits and entry hatch will be protected with a slick (hopefully) spray/sun hood.

ReadingDuty

As you can imagine I'm trying to get as much info and knowledge on designing cats, while reading stuff on the net the words of Ted Clements just brought a smile on my face.

"By design, a monohull sailboat almost invariably has to carry ballast well in excess of its ability to float it in the worse case. Ballast in itself is a useless lumpen cargo that strives to sink the boat from the moment it is launched. The decision to purchase it and float it around has to be counter-productive, if you have a choice. The nice thing about sailing catamarans is that they manage to stay upright by cheating, (all form stability, no ballast) so; you do have a choice."

Clearly the world is split into smokers and non smokers, cyclists and drivers, catsailors and monosailors etc...

EvolutionProcess

I'm currently thinking of a redesign. I've been pondering a lot these days on the actual build process. This cat must be practical within my budget, not just nice. Currently I'm debating wether it is efficient having asymmetrical hulls, especially when I'm considering building the hulls in female moulds. That would mean 2 female moulds, which is not good. I would go with a redesign - new symmetrical hulls, keeping the B/WL ratio, but with asymmetrical decks. Why female moulds ? Sanding the outside of a 9m cat is not an easy and fast process, quite the oposite. Female mould will save considerable time from the build process, also that will imply foam. This is probably one of the many turning points of the project, untill a satisfactory solution will come up. Foam will be 3 times more expensive than a wood core, most probably.

HomeDelivery

Did I mention I want it to fit in a standard 40' container ?
Just in case...

Beams

Working on the beams. Blending the mountings into the hulls is not easy, rear beam proves to be difficult. Will get it sorted eventually.

InteriorPartitioning 0408

Getting an ideea of how is the interior going to look like and how much space will there be inside. Next major design issues will be beam mounting points/connection system.

HullShape 0308

Hull flairing is relatively subtle, entry hatch and cockpit added. Current model will serve as a guideline for a final model once the building technique will be chosen.

HullShape 1407

New deck&cabin is much smoother and about where I want it regarding shape, hull blending and surface generation type, it is as fair as you could get it in nurbs. Next step is to get working on the hull flair towards the tunnel and shaping the cabin towards the tunnel, hatches etc etc. There will be some styling elements added later on, bow shape as well. And look at ALL that deck space !!! Cats are great !

HullShape 0907

This hull looks a bit better, longer waterline, same displacement with lower draft actually, thanks to the blunt "V" bilge. At 10deg heel the WP looks pretty nice, almost symmetrical. I'm currently struggling with the cabin/deck styling, want it done in a particular way, this is just a rough modelling, will be refined later on.

HullChanges 1

Modified rocker curvature for more waterline, more displacement fore and aft while less draft, tiny adjustments though. The curvature graph of the new rocker is far nicer than the old one, much smoother with less control points of course. The rocker mod came together with a new hull section profile, a blunt V shape, but again smoother and much fair. Learned that it is best to have the transoms wet and powered rig than having reserve buoyancy aft, thus supposed dry transom without drag. More hull evolution to come probably. While foam is still out of the question because of price, I'm considering stressed plywood vs strip plank or partial strip plank with ply. New hull will have smoother and better defined curvature, probably easier to control for stressed ply.

Plywood/Foam

Plywood styling vs foam. Plywood will probably be cheaper and faster, looks butt ugly...but hey - you won't notice that when you're anchored in a very nice lagoon, roasting in the hot sun on the trampoline...
At the moment my guess is that I will be able to build this out of ply and partially strip planked.

PreliminaryStyling

Just to have an ideea on the looks. The hulls will be slightly flaired towards to tunnel, but not too much, just enough to provide a bit more interior space. Hulls will thus be asymetrical.

HullProfile

Rocker curve doesn't look very nice further aft, too tight curvature ?

VolumeDistribution

HullProgress

OAL=8.8m CL-CL=5.0m

Volume Displacement = 0.882169
Center of Buoyancy = 30.4869, 28.5481, -0.118422
Wetted Surface Area = 6.6576
Waterline Length = 8.44902
Maximum Waterline Beam = 0.712711
Water Plane Area = 4.70762
Center of Floatation = 30.5544, 28.5481,0

Unfortunatelly I want the hulls to look in a particular way, so there might be some compromises regarding the hull's performance, will get into that later on.
Currently the WPL/WPB is under 12, I will try to get it closer to 13 so I will put the hulls on a diet, should look ok. There is a lot of volume in the fore area, happy about that. One of the main features of the styling is the integration of the uperstructure/deck to the hull, instead of a classical aproach with a powerfull gunwale and flat deck with a box standing on it as the cabin.
The aim is to blend the freeboard into the cabin/foredeck. Should be better structural-wise, allowing efforts to dissipate across the whole surface of the hull, instead of creating localized efforts at the gunwale/deck/freeboard. Stay close.

TheRig

It is not settled yet, while many elements of the design are clear to me -the rig is something I don't know too much about and don't have experience with many rigs, also needs to be pointed out now - I'm not an experienced sailor nor boat designer. I do know what I would want- that is a Cat rig with a gennaker, but the rig choice will be settled after more study and more advice from friends. My thoughs are: catrig is simple, few harware, easy to handle singlehanded except in strong winds, should be cheap as there is little hardware, just one sail. The cat rig should be more efficient upwind, but hard to reef downwind if the wind picks up fast. It is the most important part of the design and needs to be planned with extra care.

TheSize

Hmmm, aaahh... big ? Well it should be big enough, small enough, wide enough but most importantly it should suit the budget. The bigger the better, but I'm not quite swimming in nicely coloured bank issued notes, so I have to be realistic, which is allready very hard. I have settled on a 8.8m catamaran so far, maybe this will change, but at the moment I consider it to be a bit too much for the (future) budget and a bit too small to be really safe, 8.8m should do ok. What type? Well, it is going to be an open deck (hopefully) fast cruiser with some minimum accomodations. Considering most of time will be spent on the deck the accomodations can be minimum, I can do well without too much comfort, however others don't. Any boat is a compromise between comfort, performance, cost and styling. I'm planning for a way to be able to close up the deck space with a soft canopy like shell, in order to be protected from sun/rain/moderate wind and spray. I want the boat to be as ligth as possible within the budget, strong, practical and to be possible to have it disassembled on rare occasions.

TheBoat

Now we are getting into the interesting stuff. How should a dreamboat be ? Well, it should suit your needs, it must work as a sailing machine, it should be safe and it must be possible to make it real. After sailing cats and monos I don't want to be sailing a leadmine on oceans again, they just suck. So MY dreamboat will be a catamaran, a nice one. Most of the designs out there look like paper wrapped shopping carts on floats, they look like bad designed sofas floating around, like ugly floating caravans or bad looking stereo systems. Ok, not all of them, but most of them, we all perceive design differently so I am sorry if my view on this offended any designer. Probably my biggest mistake on this matter is giving design to much credit as this should be a working sailing machine and not a piece of artwork. Well, lets see if I can make it nice and working, a good challenge, a great challenge for a crazy person, yes that's me.

TheIdeea

Ok, so what is this all about ?
Without making a novel out of it here it is : this blog will follow the design and build process of a dream boat and the mandatory adventures. For a long time I've been dreaming about building a boat and sailing around, discovering nature and enjoying life aboard, the "usual stuff". However this remained a distant dream untill recently, as I realized this IS the masterplan I need/want to follow.
My latest sailing adventure through Europe and up to Norway taught me some basics about living aboard and how sailing is on a not so perfect sailboat.
So , I need to design a boat and build it. Why design ? Well, there's nothing out there I like very much, plus it is not that hard to design one with some help from experienced sailors and designers. Not easy though, it is a lenghty process that might have a surprising outcome, but seeing some crappy boats that sailed around the world I am confident I can do a pretty good job. I am probably in the "crazy" category so I won't change my views about this. The decision to design/build is not exactly overnight, so enjoy the blog, it should be interesting - both the process and the outcome, comments are most wellcome, as well as ideeas.