catamarans manufacturing process(es) info

[BigBeakie]

Great topic and some really good contributions. And, IMO, a very important topic.

Start with asking "What will the boat be used for?" If it is poking around typical chartering locations from anchorage to anchorage in relatively benign conditions, then the cats commonly called condomarans that are designed and built for those conditions, and more importantly, for that market, are pretty good value. They are built to a price and with production techniques that favour rapid construction. They don't try to be light, they don't try to be fast, they are first and foremost "comfortable". The build time on a 45' Lagoon is about 2,600 manhours.

Then there are other designs that make more of an effort to have some semblance of sailing performance. They are built to withstand tough bluewater conditions for an extended lifetime and not "fatigue out". They should be built of better materials, as Factor has pointed out, and have better engineering, use better building techniques, be equipped with better, more robust, more reliable equipment. They are more expensive because they have much more labour put into them. The build time for an Outremer 45 is about 9,000 manhours ( and that is very good).

There are essentially two ways to build a boat "strong". One is what I call the "monocoque" thick heavy laminate technique. This suits rapid production techniques and gives a thick heavy skin that confers some strength and stiffness, but it is HEAVY. It has to be. The outside skin is the strong frame, the bulkheads are glued in with Plexus and are more room dividers than real structural bulkheads. The furniture components play no role in providing stiffness or strength, so they don't need to be glassed in either. But, it is expected to have an easier life. Yes, I know many Lagoons have sailed around the world. But I also know that many have been in ship yards being repaired, too. I try and visit shipyards wherever I go when I can, and it's interesting what you learn from those guys....


The other way to make a strong and stiff boat that resists the enormous wracking forces put on catamarans by big confused seas, and the forces of wave impacts, is to use real structural bulkheads that are properly filleted with high density bog and glassed in, in order to distribute the loads. It unquestionably produces a stiffer boat. And, if you like the craft of sailing, it will be a MUCH lighter boat.

Are you keeping the boat for more than 5 years? Do you enjoy sailing instead of motoring? Do you want to minimise the time you are exposed to heavy weather when doing passages?

[Redreuben]

It's not just materials, more importantly it's the engineering.
Briefly, fewer bulkheads requires the core and skins to be engineered accordingly (thicker) complex interior liners and furniture may reduce panel sizes and therefore the opposite of above.
There is no rule to apply other than the engineering must be done to cater for the plethora of materials and scantlings. Most production boats are overbuilt.
A minimum of a vinyl ester skin must be used to prevent osmosis, all vinyl ester even better. Epoxy is usually special order or custom boats.

[noelex 77]

It is nice to see a thread concentrating on construction techniques .

I think if more new boat buyers were interested in how their sailboat was constructed, the manufacturers would make a bit more effort to use quality materials. I think a relatively small amount of money spent here could make a huge difference.

Structural problems are the worst type of issue to deal with. With long distance cruising boats these issues are far more common than is often assumed.

[Catmandu]

Engineering IS critical and it is also critical that the builders implement the boats as engineered. This does not always happen. Even in high-end custom builds.

[Factor]

Originally Posted by valhalla360

Balsa and chopped strand can produce a very strong very long lived boat ?

Could you point me toward one? CSM is a crap material for any boat. I owned one balsa boat, and that was one too many.

[44'cruisingcat]

Originally Posted by Catmandu

For core: high density foam core is better than balsa core,

Better in one way. Not as good in others.

[44'cruisingcat]

Originally Posted by Factor

Could you point me toward one? CSM is a crap material for any boat. I owned one balsa boat, and that was one too many.

You wouldn't want to own Kato?

[Catmandu]

Originally Posted by 44'cruisingcat

Better in one way. Not as good in others.

Indeed. So many tradeoffs, so little money, so little time ...

... that said, its still fun to learn ... What I love about sailing is that you can spend a lifetime and not learn it all ...

[valhalla360]

Originally Posted by 44'cruisingcat

Chopped strand glass doesn't belong on a cat. Or any boat really. JMHO.

Depends where and how it's being used. In certain non-structural areas, it's just fine. Of course, I was just making a point. I'm not sure if there are any builders using it for the main hull and structural parts.

By the same token, carbon fiber doesn't belong on 99% of cruising boats either but if people are willing to pay for it, builders will carbon fiber anything you like.

Saying a material is good or bad is silly until you define it's use and what properties it needs.

[Catmandu]

For cat construction methods that produce "light and stiff" structures they rank as follows -
from lightest and stiffest (most expensive) on down:

Cored Carbon Fiber/Epoxy

Cold molded Wood/Epoxy (WEST) Systems

Cored FRP/Epoxy w/ Carbon Fiber stiffeners (e.g. bulkheads/stringers)

Cored FRP with Epoxy then Vynlester, Poly Ester

Monocoque Aluminum - Appropriate for bigger boats

Solid FRP - not light if you need it to be stiff over a large structure

Other build methods can give you a strong stiff structure but are not very light ...

And I read an article about some that are considering 3D printing of sailboats - I'm not sure if they can be made light/stiff enough but it is an interesting idea.

The main cost drivers are

Materials
Labor
Tooling
Systems

Not necessarily in that order as labor costs for example will vary from place to place and the amount of labor needed will vary depending on the build methods and materials.

IMHO the current state of the art for catamaran building methodologies can be studied at HH Catamarans. There is some interesting information about their manufacturing processes and how they go about building their boats. But in the end it is all about execution and how all the pieces come together and you will only learn the result from the owners themselves.

[Catmandu]

Oh I forgot currency fluctuations as another potentially significant cost driver/savings depending on where the boat is constructed and the world market for the local currency.

[Factor]

Originally Posted by 44'cruisingcat

You wouldn't want to own Kato?

Absolutely, but I thought it was Duflex - quite different to just "raw" balsa and epxoy as well and built by good builders.

I was more in a head space of production builders with balsa core CSM Polyester resin and crap attention to detail (e.g. one of the so called big three)

[44'cruisingcat]

Originally Posted by valhalla360

Depends where and how it's being used. In certain non-structural areas, it's just fine.

I wouldn't even use it for waterproofing.

[tuskie]

Originally Posted by Factor

Could you point me toward one? CSM is a crap material for any boat. I owned one balsa boat, and that was one too many.

Please enlighten. Which of the "big three" manufacture using purely CSM?

Chopped strand mat is used by the majority of fibreglass boat manufacturers, usually to prevent "print through" of the directional cloth layers into the gelcoat. As such, it serves a legitimate purpose.

An added bonus is that such layups are easily repaired as minor dings don't penetrate and compromise the underlying "high strength" cloth layers.

A point worth noting is that the total epoxy/glass skin thickness of Duflex is a mere 0.53mm or 0.021 inch.

[44'cruisingcat]

Actually it varies. There is a huge range of laminates available.

But anyway, I'd always prefer a thin laminate of very strong multiaxial glass with extremely good resin to glass ratios over a half inch of rubbish.