Building a sailing catamaran

Catamaran Hulls Unite

If we wanted to be sailing within five years, we were going to need assistance during the building process and we needed to move fast and we needed to talk to someone about it. My father passed on some kind words of wisdom during this time suggesting that we locate or get someone to complete the hulls at least, which would give a huge kick-start to the whole process.

These words of wisdom come from someone who has been there and done that. Armed with this, we tracked down a pair of 10.5m hulls on the Sunshine Coast, but for one reason or another chose to go with a larger vessel.

We put this to the Snell's and low and behold, an offer was made to build the hull shells and lower bridgedeck floor for us, at a cost of course and these three components would be ready within two months.

"Two months" we muttered quietly, "No shed, no money, no tools...no idea". We did part with a cheque that day by the way.

Its not until you see Peter (some 6 foot tall - give or take a few hairs) that you realise just how large these hulls are. What you see here is only half of the final boat height. Quite awesome. Catamaran hulls are very cumbersome to maneuver. Just food for thought for those intending to go this route, transportation of these items can be very expensive and that's a story in itself for another day.

Things were moving well, so we went out and had another chat to Peter and Anne. Read the full story and more...

Frames to lower bridgedeck

The main frames form the structural growth of the yacht. If you have chosen to go with an Easy, this next batch of slides will make sense when you compare them to the plans.

If you do not have the plans yet, there are key frames that join the hulls together.

These 'Frames' form a big role in the overall strength of the boat and three of them are 'Structural'. They are all cambered and will later form the base for the bridgedeck roof.

frames

"retrieval process of the anchor,

a no nonsense approach is almost mandatory"

Plinths

 

Plinths are 9mm pieces of ply, cut to size with a 10-20mm overlap and routed around the external edge. They are used to place under deck fittings normally on the horizontal, and their primary function is to reduce the possibility of water ingress around the screwed areas.

This meant that the plinths had to be beefed-up to take the stresses and moments we would be placing on areas such as the forebeam. We had been told that one should always winch from a horizontal surface as the sideways stress moments would eventually cause unnecessary wear on the beam/winch bolt points.

This did unravel its own set of new questions and became challenge 'number one'.

  1. Where will the boom-traveller tracks to be laid?
  2. How many stanchions were required per side?
  3. Where will the water inlet be laid?
  4. Above the external lockers, which side do we lay the hinges (fore or aft) and why?
  5. Where will the winches go?

The latter being very tricky, as the turret hatch we had installed will directly affect the number of winches on that side. You needed this information for deciding on plinth sizes and positions.

Having made the Plinth-decision, it was not until we got started making these bits that we realised how many there were.

  1. Under the deck locker hinges (two per hinge),
  2. Under the cleats (three per side),
  3. Under the mast electrical connection, water filler neck, stanchions, winches, tracks, turning blocks etc

The list just kept growing.

anchor

Anchor Roller System

We have chosen to expand in this area given our inexperience (or lack of..) in the anchoring of such large vessels. We needed everything to be on our side when 'Murphy comes knocking'.

Unless one is aware of all the anchor limitations during the retrieval process, a no-nonsense approach is almost mandatory.

This meant that the anchor system had to be beefed-up to take the stresses and moments we would be placing on the beam area.

Anchors should always be winched from straight ahead as the sideways stress moments would eventually cause unnecessary wear on the winch motor and the system itself.

While this may appear a little eccentric, for those who are not in a real hurry, these can prove very useful and remove possible repairs at a later stage, additional insurance as we saw it.

anchor_rollerOthers had told of wearing bushes on the winch rollers thenselves and even rollers coming away during retrieval mechanism - this becme challenge number two.

The roller system also needed to pull the anchor into the full-up position and not damage the timber fore beam in any way.

The latter forced us to make a decision on the primary anchor type that we needed and this ended up being a Sarca. We say primary as two other anchors will also be carried.

This type of anchor, while expensive, is designed to withstand a variety of bottom types including mud, sand, gravel and rock, offering superb holding power in all conditions - so they say.

It also happens to have a self-righting arc over the top of the anchor making initial anchoring easier.

The Sarca Anchor top arc also went into the build equation, as it does stand out a little and could easily damage the fore beam if not managed correctly. The Sarca also happened to be one of the physically larger anchor types making the fitting of any other anchor type within the Anchor-winch-assembly, easy. 

 

We also wanted the unit to be one with the:
> Fore-beam A-frame,
> Cat walk brackets, and
> Fore-stay Tang.

Using Stainless Steel would have prove too heavy, so Aluminium 5083 plate was used. Even with this alloy, weight would still be an issue, but one we were very happy to live with.

We have chosen to weld this to the ‘A-frame’ and make a single solid unit, reducing the number of screws required through the main forward beam and in turn reducing weight further.

The components were cut at home using a jigsaw (and about 8 aluminium cutting blades) and an Angle Grinder. Also cut at the same time were the desalinator and radar frames.

The winch-roller holes have been drilled to take standard fittings from the local chandler. Given that the shop items are galvanised steel, this would definitely not be compatible with straight 5083 Aluminium. To remedy this, we have made bushes that slot into the holes and are easily replaced when and if needed.

Additional holes have been drilled to provide for 'tweaking' once in the water and also in the event that one hole-pair wear to much, they can be moved to the next most suitable.

We have seen this anchor system copied on many other catamarans now, which is fantastic. Please remember that this content is provided under copyright, feel free to use the measurement and dimensions from our Books, but within the Terms of Use.

anchor_roller