Build time 40ft catamaran

Although they are now over 20 years old, these are still useful articles for those thinking of building/finishing off a boat

http://sailingcatamarans.com/index.php/articles/8-building-articles/15-finishing-off-a-shell

http://sailingcatamarans.com/index.php/articles/8-building-articles/14-flat-panel-construction

Richard Woods

 

One thing I've found useful are full size mock ups of various interior components to make sure things will work out as planned if you are coming up with your own layout. Even cardboard cut from boxes and taped into location will give you a good idea of the space. If everything passes I make and fit low grade 3 or 4 mm ply patterns and test for function. These are then used as the patterns for the expensive marine ply, being fitted I can cut to the line knowing it will take little extra work to fit the real thing. It sounds like a lot of work but is more economical than wasting good material or building in something that doesn't really work as well as you'd like.

I second the concept of function in the various areas, good sea berths and safe galleys etc....Many boat show layouts are pretty silly at sea, no seaberths, bunks in the pointy end and no provisions for staying in place. It is easier to sell a interior for entertaining when tied to a sheltered dock but a real boat is a vehicle on a medium that is rarely still. Huge cabin widths and no hand holds are pretty dangerous in rough weather. Getting tossed 5 feet can hurt but flying 10 or 15 is much worse. At sea when it kicks up you are safer sitting down so headroom is less important for sure.

 

Agreed! and you don't need to do it on the boat. You can do it in your front room - or - on small boats, under the kitchen table

Richard Woods

 

For drawers, cabinet hardware and doors IKEA is the place to go. All plastic, stainless, steel or solid wood. Wonder if they have any usable furniture there for a boat as well?

How much does high build primer help on the interior finish?

 

Good joke! We all know drawers, cabinet hardware and doors add lots of weight.....next thing you know someone will want a tile floor....

 

Cav - Agreed (again)!

Avoid drawers, I haven't ever had one on any of my boats. On a multihull open fronted lockers work well. They are the lightest, cheapest, quickest to make

Ikea probably doesn't use real wood. And almost certainly uses interior plywood, not marine grade or even WBP

Richard Woods

 

The open bins also allow good air circulation, help prevent the contents mildewing and are good for rot prevention on a wood boat. I've seen a few Searunners done in by closed storage.

I think textiles have a place for interior storage. I'm looking at making some sort of easily attached close weave netting for the bin fronts to semi conceal the contents for a more uniform appearance and retain the contents in super rough seas or a capsize situation.

Some areas will get the equivalent of cloth shelves or hanging storage. Ikea may even have something here but it has to be outdoor fabric for a boat. It really makes sense for a multihull as cloth is lighter than the thinnest ply, can be padded, has lots of colors and textures available and such storage solution can be easily removed for maintenance, painting, cleaning or other things like lightening ship for racing.

When contemplating any multihull it is important to get involved in the weight consciousness from the beginning and treat it like an airplane instead of a house. For paneled doors and heavy hardware you need a monohull. This is one area the home built multihull movement has always needed help because many of the people with the drive and skills to tackle a big project have done things like build their own houses, workshops etc...where weight didn't matter. So remember to drop those drawers and let the breeze in for better sailing which is what a multihull is about.

 

Psychological factor of size

In general I agree with the idea of not building larger than one "needs". And one should a boat for oneself that fits need, scope and budget. However there seems to be a psychological factor when it comes to size and value. for example there seems to be a huge difference in value of a boat difference from 39 ft to 41 feet breaking through the 40 foot yard line. This when the extra two feet can easily be added to stern without altering any other dimension.

 

So Richard, on a 40' trimaran, what thickness plywood would you use for say a galley cabinet/counter? Glass in 6mm side bulkheads, and face with 4 or 6? I read your article where you say to use 9mm for a counter top, but wasn't sure what you would recommend for non-structural bulkheads/cabinets.

The plan before I read you article was to glass in 1/2" sides, face with 1" x 2" lumber for more of a stick built design, and have full length "euro" style cabinet doors with a vinyl Phifertex mesh fabric as the insert for light weight, ventilation and coverage. I'm guessing you think the 1/2" sides are overkill, but does the rest sound light enough, or would plain ply face be better?

I'm currently cruising on a fairly light weight 34' monohull with all the furniture built in 1/2" ply, but looking to buy a 40' trimaran (7800 pound) that needed a new interior, and trying to keep weight down.

 

I have used 3mm ply fastened with small epoxy fillets for non-structural furniture in a small boat and found it strong enough. You need a bit thicker, e.g. 4 to 6mm for items that will be sat on, and 6mm to 9mm for items that will be stood on (depending on the span between supports). I dont think that the scantlings for something like a kitchen cubboard need to vary all that much with the overall size of the vessel, its more a matter of how much weight (and hence performance) matters to you, relative to how much a solid look and feel and general resistance to misuse matters to you.

I am still trying to get my head round this idea that foam sandwich construction is quicker than plywood!

 

I agree with John

The only time a glass interior is quicker than wood is if you use temporary moulds. You avoid all the joints and all the painting, potentially it can be lighter than wood

Years ago I made a 4 sided box mould (no back no bottom) about 600 x 500 x 500mm. Later I used it for the interior furniture on my 32ft Eclipse catamaran. It made the chart table, battery box, wet locker, galley shelf, heads extension, cockpit seats and probably other bits I don't recall. A very useful, time saving, multi purpose mould

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

I believe the Fusion comes in at 4.1 Tonnes and full displacement of 5.75 Tonnes.
I thought that seemed pretty reasonable for 12m?

Jason Guard has a clip delivering one down East Coast of Aus doing 18-22 kn.
I would be pretty happy with that myself...not sure if that one had much fit-out at that stage though.

http://www.youtube.com/watch?v=id8l6ORmDpQ

I imagine the kit is expensive because it is all vac moulded and designed to go together quick.

 

The video shows 15kts surfing down a wave with a stiff breeze up the bum... Hardly impressive by modern multi standards... They are not celebrated for their performance traits... But not a terrible boat either... Most of the boat is infused in solid glass, foam core is only used sparingly in a few key areas, hence the heavy weight compared to a full sandwich construction.

 

Plus they have the EAC pushing them along, which would add 3 to 7 knots on a GPS speed depending on where/what time of year they are sailing.

 

Well frankly the fastest way is a fully kitted boat with prefab parts, followed by a partially kitted boat with prefab parts.

And it turns out there are lots of these out there... HUH? you say?

Buy a used boat that is close to what you want. then cut away the bits you don't want and build new.

guaranteed this will be less work. And if that sounds daunting - then building from scratch is worse.

Look building from scratch will not save you any money. Because

• If you Hire out Labor to help it will
  1. Cost top premium dollar if you want top skilled workers who have the experience to do it right the first time
  2. Cost you twice as long and twice the materials costs if you go less expensive because of rework impact
  If you do NOT hire out labor
  1. There are a lot of things that a 2man or 4 man team can do 4x and 10x as fast as a one man team So your build time goes up. much much faster than imagined
  2. there are going to be rework costs as YOU make mistakes out of inexperience

And the idea of buying interior fitout at Ikea is silly. IKEA relies on cheap MDF wood that is not designed to live in high humidity environments, held together with twist-lock gadgets that are neither rustproof, nor designed to hold over time in an environment that is constantly twisting and working and vibrating.

I see Ikea furniture set out for the dump truck every month. And it takes only 2 days of moisture for it to start to turn to sawdust

Here's another way to think of the issue of doing surgery to an existing boat.

For a new boat you have to build the hulls, and the deck and the house.
For a surgery boat you cut away the old deck (1 day's work - I've cut up boats before), build a deck an a house. 33% build savings right there.

Also, you basically get to keep the rig - if you do the deck redesign carefully, you don't have to redesign the rig or even redo where the standing rigging attaches. And fitting out the load bearing bits for the rig is a non-trivial part of building.


But bottom line, it sounds like you do not have a wife and kids that are willing to tolerate you doing nothing but building the boat. Which means that if you are going to build it then
a) Plan to lose the assets you will lose in a divorce - because you will get divorced (80% of all homebuilders I've met have been divorced)

b) Plan to have a 2 year interruption in your build schedule for the divorce.


Now the Divorce aspect does make one thing easier: You don't need to build a boat for a retirement COUPLE... just yourself