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.