New Bi-Rig Performance Cruiser

[cat man do]

Originally Posted by 44'cruisingcat

Where from Dave?

I actualy bought direct from
::: SAM ALLEN WHOLESALE

You're a professional boatbuilder right

Dave

[freetime]

Alan, do you have any new drawings and any cad with the interior?

It´s even more interesting now when you probably will build atleast one.

[fastcat435]

Hallo Alan. Make sure that the company that you are signing on to build the boat is registered with the Sabbex and have them allow you to bring in external surveyors whenever you want.
It will help you getting the best possible boat

Good luck with the building process and I hope you get a fantastic boat build

Greetings
Gideon

[Eleven]

Sound advice from Gideon.
It's a beautiful boat and I hope does all you want of it. You have certainly given a lot of though t to each aspect of it and I hope you'll excuse me asking you to consider a couple of items.
Below water hulls. On Page two you were considering keels for the boat to stand on. Have a look at the old Prout Hulls. Excellent to ground on (bottom cleaning from the beach or slip) and each contained a water tank. Low cg, leaks in the keel only contaminated the water, not the carpets.
Water Tanks. Consider rain water collection to some tanks with segregation.
Hull shape. A key factor in not capsizing, in theory, is that as the ww hull lifts the lw hull slides sideways. Biasing the keel line inwards from datum would help this, and making the front third sharper would help a sliding hull pull the bows into wind.
Tank Testing. I'm sure you know that models can be cut by cnc from cad drawings. This will help in finding the cp of the hulls in normal and extreme conditions.
And if it's a cruiser a hand held remote is the helm postion. If thats on a bow or part way up the mast so be it. Nice to have a nav station for channel into marina work though.
Rotating masts need only swing maybe 30 degrees to get the convex shape smooth for upwind work. You'll outperform nearly all mono's then.
Beautifull lines. It's bound to sell to Maserati and Lambo owners. Perhaps the real market will be to the ultra rich who've tired of the running costs of power boats.
Will it scale up to seventy feet. WOW. Good luck.

[Maren]

Originally Posted by Nordic cat

Hi Maren,Looking forward to your comments and ideas.

Another thing comes to mind: anchor retrieval. Right now it looks like you are planning to drag the majority of the chain across the net, however, I'm sure that isn't the case.

May I suggest a trough, in case you haven't already?

[Nordic cat]

Originally Posted by Eleven

All comments are valuable,positive ones like yours are just great, keep the questions and ideas coming please.

I have decided to go with both the LAR keels and daggerboards. The keels primarily for standing on the hard or beaching. These are low volume so will not be used for water tankage.

I have 2 x 150 liters freshwater tankage on each side, so I can pump water both fore/aft as well as across the boat to help balancing.
I have also got one 180 liter "greywater" tank each side. As there as yet aren't laws requiring grey water tanks, my idea is to use these for rainwater. Rainwater collection wil be from the forward part of the booms, where a hose can be attached. The soft bimini over the aft cockpit is also designed with a hose attachment for rainwater collection.

The "tripping over the keels" theory seems to have been disproved by the fact that a wave of the size capable of flipping a boat like this will be travelling so fast that it will pass the hull in less than a second and be supporting the boat by the bridgedeck.

To my knowledge there have been no recorded "sideways flips" by large cruising cats. Pitchpoles are the way that accidents seem to happen, when a bow digs in.

That is the reason for the enormous amount of extra bouyancy I've added to the bows, ending in a so called "tulip bow". The large chines are also carried far forward for extra bouyancy.

I have had a model made using CNC - I'll post a picture later.

I did consider just a remote for the inside helm station, but I love steering for an hour or so on each watch. It gets me synchronised with how the boat is trimmed, and keeps me awake.

This is true on the traditional rigs, but here the booms can be left to feather the main on any point of sail. This is a major safety factor, as you can reef at any angle to the wind, also dead downwind, which can be a major problem with the traditional catamaran rigs. I know, as I've been there....

The mast needs to be able to rotate relative to the boom, this will be done by lines led from the sides of the boom to small protrusions on the sides of the mast. These will also be steps for shorter people to be able to cover the sails.

Thanks for the kind words. Yes it will scale up quite easily, scaling down is the problem.

I started the design as a 43/44 footer, but after choosing to go with a forward cockpit, extended it first to 47 then to 49 feet, without changing the beam.

Regards

Alan

[freetime]

Hi Alan, did you sign anything this week? In SA?

What weight do you calculate after all changes?

[Nordic cat]

Hi Joakim,

Yes I signed the building contract this week!

We haven't finalised the design of the rig, so we don't have final weights for the rigs.

Our estimate for the 2 rigs excluding sails is around 740 kgs. This seems a bit on the high side, but until it is finalised I prefer to err on the high side for weights. I think we can lose quite a bit of weight on the boom and vang setup, so we are looking at ways to lighten it as well as enhance the looks.

The lightship displacement is at 6800 kgs for the base boat ready to sail.

Load can be up to 5 tons, but "normal" full load is around 10 tons.

Lightship : 6800 kgs
Fuel : 400
Water fresh : 660
Water black/grey : 300
6 crew incl.lugg. : 700
Provisions : 400
"Toys" +dinghy : 500

Total 9760 kgs.


The mast design is currently undergoing FEA or Finite Element Analysis to ensure that we have the dimensions and layup right. We are also getting FEA done for the hulls to ensure the required strength, especially where the masts are. For the masts we are using a Safety Factor of 2.0. We want the mast to flex in the strong gusts, and have designed the top part so that a 30 knot gust will flex the top about a meter. This is an important safety factor as well, actually works like a first reef in the mainsail.

Regards

Alan

[freetime]

Woow... Fun!
I must say that after looking thrue the market after multis in 40-50f i like your most of them all...
And the possibility to custombuild it to your own specs. And the bi-rig...

Are you planning to build more than one for you?

www.nordic-cat.com is free.....

[ireaney]

Congratulations Alan, Looking forward to hearing and of course see the progress, as you know what you are doing really interests me.
I am sure that you are really excited now that things are on the move.
Please keep us informed of the build.
Cheers
Ian

[Nordic cat]

Originally Posted by Maren

Another thing comes to mind: anchor retrieval. Right now it looks like you are planning to drag the majority of the chain across the net, however, I'm sure that isn't the case.

May I suggest a trough, in case you haven't already?

Hi Maren,

The anchors are deployed directly in front of the anchor locker, under the trampoline. There is a seat area aft of the tramp, in the middle there is a hatch. See attached sketch. This hatch will give acess to the anchor rode, to attach the permanently rigged bridle. The bridle is attached on the inboard side of the bows, and will be attached next to the anchor well, but under the tramp when not in use. (Hope this makes sense)

So, no chain across the net....

I plan on using an Hydrobubble anchor, any comments to that?

Regards

Alan

[Nordic cat]

Here is the initial render with the 2 masts, but several things are being changed, like mast rake and the bomm and vang design.

The boom will be lower down on the mast, and not be horisontal, the vang will be smaller and lighter.


Alan

[Nordic cat]

I have looked at a number of different ways to attempt to predict the performance of the boat, and have had slightly differering results, but there is a certain consistency as they all come up with around 100 to 110% of windspeed on a reach for a lightly loaded boat. (7500 kgs = 700 kgs load) This is just with the bi-rig, no foresails.

I asked a guy who calculates handicaps on the west coat of the US, where they use a PHRF rating, which is defined in seconds per nautical mile for the length of the course, not distance sailed.

He ran the numbers for me and the result was:

For the boat without foresail/Gennaker: PHRF = 0.

To get an idea of what that means, a Lagoon 47 has PHRF 127. So for each mile, I would have to sail 127 seconds faster than the Lagoon 47 to sail to the handicap!!

If the boat is rated with a jib and gennaker (~120m2 2D area) then the rating would go to around -60. So would need to be over 3 minutes faster than the Lagoon per mile on average.

This is the same kind of rating that the ultra fast racing Farrier tris can achieve.

This is all very heady stuff, but it's good to know that even if the boat ends up a few hundred kgs heavier than designed, she will still be at the high end of the performance bracket.

I have decided to make moulds for the hulls to save even more weight, as we will be able to make do with even less fairing.

With moulds, the option to build more boats is more viable.

Freetime, do you want to order one, it would be nice to have more Nordic cats in the Nordic countries

Regards

Alan

[freetime]

Not yet Alan, but i will follow this multi and i am very interested. To be honest, i don´t have enough money yet. I working on it...

What´s your schedule for the buildingprocess?

Is it a secret who should build the boat?

When you have any idea what the price on the boat is you can pm me...

[Nordic cat]

Hi Joakim,

The boat is going to be built by 2 Oceans Marine in Capetown. See:
Two Oceans Marine Manufacturing | catamaran


Take a look at the photos of some of the custom cats.

They have an outstanding reputation going back about 20 years. Their website doesn't fully show the diversity of cats they build. They will launch at least 3 large custom sailing cats this year between 45 and 60 feet, as well as a large number of motor cats, including 3 Powershuttle 44 footers.

It's a family owned business.

I have spoken to owners who have had boats built, designers who work with them etc. All are very positive.

I spent more than half a day alone, going through the Shuttleworth 47 they launched in December 2006. Looked into all the closed areas as well, saw the documentation. Even had a sail on the boat.

There were things that I would have done differently on that boat, but the quality of the work was amongst the best I have seen, and I have looked at many boats....

The things I would have done differently were not decisions made by the yard, but by the owner and designer, so it all comes down to personal preferences.

I have around 100 pages of specifications, weight sheets, hardware lists, photos etc.
I am a marine engineer, and run a company doing projects on a regular basis, (in a completely different field). The one thing I have learnt, is that if you want something, specify it.

I have visited the yard 4 or 5 times, and seen how they work, and the attention to detail, and the good project management they do, so I am confident we will have a good project, where they make money and I get what I want.

Of the 5 yards I visited originally in SA, 2 Oceans Marine and Custom Marine i Knysna were the best 2 IMO.

2 Oceans were more experienced with the build methods (infusion), materials, as well as handling CE approval and the project type we are doing. There is also a better pool of specialists and suppliers available in Cape Town.

(If I wanted to build a Duflex boat like a Schionning, the Custom Marine would be my choice.)

Regards

Alan