FRA sails-4-south-fra  ESP sails-4-south-esp

UPDATED 2021 08 08

Sailboat for the Austral Seas

2013 - 2021

Construction news

2021 07 29 S4S becomes SONABIA 2, She was launched today in Socoa, Iparralde,  France.

From now on, see posts at

2020 12 31 Thank you, COVID. Stuck in the Basque Country since July 2020 we could work full time. The work has been going fast.
Keel hauling system,
Rudders (final)

2019 09 07 End of work for 2019.
The work started in february, and the weather was exceptionally warm. Later, not so good: unstable weather, then extreme heat periods... anyway. Work done:
portlights and hatches installed,
deck gear built and installed: organizers, blockers, cleats, lifelines stanchions, etc.
deck and cabin painted (coating = pigmented epoxy resin)
hull painted (pigmented epoxy resin, dark grey to capture heat)
rudders installed (2 lateral rudders, 1 central only for engine)
In july we removed the tent under which the boat was built since may 2015. 4 years under a f. tent, leaking from everywhere,  with a swamp at the entry, and absolutely no space.
Finally in the open air!


2018 11 12 End of work for 2018.
The work period was shortened because of weather (March and April too cold, heat waves in July and August), and the work was slowed down by material shortages (from factory).

Anyway, decent progress (portlights, rudders, deck accessories, coating...). One more year, o so we hope.
Here are a few photos, this site will be completed later.

2018 10 14 - Rudder boxes     ... blades (2 lateral+central)
2018 11 10 - roof, pilot house .. and dog house

2018 11 01 Doors closed         .. open

2018 11 10 Interior

2018 03 12 Start of work for 2018. Work estimate:
5800 hours done,
1500 hours to 2250 hours to do.
1 1/2 to 2 years work if the budget is OK.

GREAT NEWS! The shipyard will fix the "swamp problem", dirty waters gathering in front of the tent because of a clogged drain. After 3 years...

2017 11 30  End of work for this year.

Visible progress (deck, cabins, pilot house, cockpit..) but slowed down by budget limitations

Estimated end of work: 1 1/2 year from now.

2017 03 07. Starting again after a sailing season near and around Cape Horn.

Planning for this year: finishing interior work, roof, pilot house and cockpit.

2016 11 20 End of work for this year. Uneasy conditions, but some progress, see above.

Too cold in March and April (bad for resin), too hot from July to September (bad for resin).

No space. Under a 15m tent, no space to move around the boat, no space to stratify large panels. Muddy and wet. Leaks and a swamp when it rains.

Lousy tent (cheap) and lousy drainage (none). The Socoa Shipyard has a clear policy: zero money for infrastructures and equipment.

2016 03 17. Work resumes, after returning from the travel Mares del Sur.  This time, the boat is outside the building, under a tent.  Narrow and short, bow and aft touch the tent.


2015 07 01. Work is suspended until next year: currently preparing our RM 1050 Sonabia to return to Tierra de Fuego. Leaving in October.

Status: hull and internal structure ready, keel in place (lifting mechanism not installed), engine in place (accessories not installed), tanks in progress, deck in progress.

2015 05 05.The keel and the engine are in place. The boat was pulled out of the building and left under a tent for the rest of the work.

February 2015:
 The last 2 months, the work has been slowed down by chilly temperatures ( 3 days to harden vs. 1 day in normal conditions). Nonetheless the work went on, thanks to the tolerance of Resoltech resin (1020-1026): we could made epoxy joints and bonding in temperatures of 4.5oC, and glass epoxy laminates in temperatures of 7.5oC.
2014 05 06: turning up the hull. In a travelift, loops of rope passing through holes in the hull. The hull was lighter than calculated (2160kg vs. 2350kg expected). Explanation: good ratio resin-glass: less than 45% resin instead of  50%- 50%.

The idea

The idea came during Matxitxako Horn (2012 2013). Our sailboat Sonabia is not  fit for heavy weather in  the screaming fifties, nor for sailing in ice: Plywood does not stand impacts.

In Puerto Williams and Ushuaia, discussions with sailors about the perfect boat that does not exist.  The most informative part: explaining to others the defaults of one's own boat.

Why not get mad?

Let's start from scratch. 
- A service boat, simple to repair and maintain. 
- Capable of sailing lightweight and under heavy load.  
- Composite hull (zero maintenance) on plywood layer (easy to repair at sea). 
- Deep V-shape at the bow (to sail against waves without slamming). 
- Lifting wing keel (performance under sails and getting close to the shore). 
- Powerful engine (to go against wind in the channels) and big fuel tanks.
- Internal steering and protected cockpit, good thermal insulation and ventilation,.  
- Hull 100% accessible from inside (repairs at sea). 
- Almost anything aboard can be dismounted and repaired aground.
- Construction: simple techniques (basic infrastructure)
- Common materials (easier to find in case of repair). 
- KISS. Keep it Strong and Simple.

Find an architect, a shipyard where to build it and spend your last cent in the project.


Code name: S4S 46.
Architect: David Reard
Dimensions: ~14m x 4.50m (46 fts), 
Draft ~2.80m-1.50m, 
Displacement ~ 9.5 to 10.5 tons empty, 15.5 tons full load.
Hull  composite sandwich, fiberglass epoxy-PVC foam-plywood. Thickness 45mm up to 55mm.
Typical: 2mm glass-epoxy, 10mm plywood, 2mm glass epoxy, 30mm PVC foam +2-8mm glass epoxy 
stratification strengthened underwater and at the waterline.
Deck composite sandwich, fiberglass epoxy - PVC foam. Thickness 33.5 up to 36mm
omegas and strengtheners when needed
Keel: liftable wing keel (dagger) 3.4 tons,
Rudders: 3 external swinging rudders.
Engine: 85 HP. Nanni.

2013 09 04                                 2013 10 30
first draft                                     shipyard

Hull frame

2013 10 31                               2013 11 22                                 
frame - not assembled             frame - assembled                     


Experiments - hull material

2013 12 20 - hull material proposed by the architect. Improved after crash tests

2014 01 10 - crash tests (impact bending tests): repeated impacts with increasing energy). 

3-points bench, length 80cm, 20cm above ground. Free extremities. Weight 5 to 20kg falling from 1m, 2m, 3m.   
impact sequence, hull material. here: 20kg falling from 3m. 
impact sequence, external layer alone (fiberglass epoxy). Here: 20kg falling from 3m, repeatedly.

Results.  new hull sampling lighter and ~ 2 times more resistant than 12mm thick aluminium 5083. Safe in case of crash: damage is limited to the interface between the foam and the external skin. The hull remains watertight and damage is easy to repair.

Note.The sampling proposed by the architect had the same weight/m2, was less rigid and presented a poor behavior in case of crash, like any foam sandwich.


2013 11 27 hull - plywood 

2013 12 20 - hull - fiberglass epoxy (2 layers)    

2014 02 25 hull- foam 30mm, 68kg/m3 (divinycell matrix 11-9). Foam blocks walled with fiberglass epoxy.

2014 04 11 -hull - external shell. fiberglass-epoxy, thickness:  3mm to 6mm (below waterline). reinforced bow.

2014 05 06 -building frame (chipboard) removed - below waterline: primer + antifouling - internal structure.

2014 05 06 - turning up the hull. weight: 2260kg

2014 09 07 - 2014 10 24: internal laminates of glass epoxy.
hull: 1mm thick above waterline, 2mm below
bulkheads: 0.6 to 1mm laminate below waterline, joints: epoxy putty + 2 to 4 layers of glass fabric. 

2015 02 19 o 2015 04 05: crash boxes, foam covered with fiberglass epoxy

2015 02 19 lateral fender (30mm)    2015 02 19 bow crash box (90mm)

2015 03 15 platform (rudder protection)


They  transform the hull into a beam that stands the weight and the buoyancy. Huge safety factor in order to handle the worst case: in a wave, bow and stern below water and central section out of the water, the load becomes dynamical (fall and impact).

Main girders: multi-layers plywood + fiberglass epoxy, external cover and internal sheets half way from the neutral plane, to stand impact bending without breaking the plywood.

Stiffer and lighter than the solution of the architect (multilayered "I" beams vs. homogeneous rectangular beams).

2014 11 01 - central section girders
 2015 04 05

Internal structure

In addition to the girders, this structure contributes to the stiffness of the boat and strengthens the hull against  crushing.

2014 11 25 - bow and aft bulkheads, secondary girders and brackets (side strengtheners). plywood+ glass-epoxy.   

Aft girders and brackets + deck lockers
2014 11 25                                   2015 03  07


Low girders in rear bunker.
- Stands the efforts of the propeller bracket (enclosed in a box)
- Strengthens the hull to stand heavy payload (the rear hull is almost flat, i.e., the shines add no stiffness).

2015 04 30                                   2015 05 24

Dagger keel

3.4 tons. draft 2.85m to 1.40m. To use in 2 situations: 
- shallow ports & moorings
- maintenance, to ground the boat along a dock or a pier

2014 06 25                              2014 07 22                              2014 09 06                      
steel core, 3.3 t. steel planks + PVC foam+ glass epoxy (2mm to 10mm).
2015 03 22  keel edges     ...                                     2015 04 14 bottom                  

Keel slot

The critical issue for a dagger keel

glass epoxy, 25mm to 100mm thick, embedded in girders

3014 09 06.                       2015 09 08                                     2014 09 15
2014 11 25                                   ...                                                2014 12 12 keel supports

2015 04 05 integrated to girders      2015 03 22 below hull

Standalone wooden structure to lift the keel
2015 04 13                                   2015 05 05

... completed by a wooden frame (stratified plywood) to support the roof
2017_04_25                     2017_11_26 ... lids, table   ... mast base                  ... from deck.               

Keel in place

2015 05 05


Nanni 85 HP, shaft AISI316 40mm, fixed propeller 3 blades, 20", step 17".

Propeller close to the aft and relatively shallow (25 to 35 cm below waterline) for better protection and access from the rear platform.

2015 04 05                                   2015 05 02                                   2015 05 05                        


2015 05 24                                   2015 05 24                                  2015 06 04


2015 06 22  - skeg                        2015 06 29 fin-fiberglass epoxy     2017 03 29 - foam sandwich
                                                                                                                       mechanical fuse

- support 1:bronze bracket, enlarged by a composite sleeve 15mm thick, in a composite box (epoxy filling)+girders.
- support 2: composite tube, wall 12mm thick, supported by a U (foam+10mm thick glass epoxy)
- protection skeg below the tube  completed with a foam sandwich shape (mechanical fuse)

Engine compartment

Below cockpit, removable floor to remove engine.

Front compartment: under pilot house. Separation bulkhead 1m high between engine compartment and technical compartment to prevent flooding.

Access to engine:
Top: from cockpit, top hatch
Lateral: 4 hatches in rear cabins, sitting on elevated floors (see floors)
Front: sitting in front compartment
Rear: from inside (access through rear lateral hatches)

2016 11 19 lateral                         2016 11 19 from cockpit                2017 11 26

2016 10 05 - front access


Integrated to the structure, with large access lids for repairs (bonded and screwed) and inspection hatches


2 main tanks (center of cabin, 4 compartments each, capacity 2 x 700L.).
Moldered directly in the bottom of the hull between girders. Lighter than separate tanks, low center of mass.

1 buffer tank (80L) to feed the engine and the stove by gravity.

Fresh water

2 tanks (side of cabin + toilets, 5 compartments each, capacity 2 x 380L).

Moldered directly in the bottom of the hull between girders. Food compatible epoxy coating.
Lighter than separate tanks, low center of mass.

2016 05 10 compartments 1-4...      compartment 5.

Tank lids (freshwater and fuel)

20mm sandwich (plywood-foam), contain inspection hatch (16cm diameter)
The tank internal wall is part of the lid (easier maintenance).

2016 09 03

Black water

2 tanks, one for each toilet, capacity 70L each

Made of a 10mm sandwich (glass epoxy, PVC foam), integrated to the structure. Lighter than separate tanks

2016 05 03

Grey water

2 tanks, one for each toilet for washbasin and shower. Capacity 30L each.
1 tank in the kitchen, below the sinks. Capacity 70L
Made of a 10mm sandwich (glass epoxy, PVC foam), integrated to the structure. Lighter than separate tanks.

2016 11 19


20mm sandwich, with stiffeners.
5mm plywood outside, 10mm PVC foam inside,
Reinforced with 22mm x 50mm plywood profiles.
Epoxy coating.
Lighter and more rigid than the 15mm plywood proposed by the architect.

Cabins: elevated floors above storage compartments (also support the bed frames)

Main room: floors = tank lids + intermediate plywood planks (also used to anchor the furniture)

Pilot house: removable floors

201 11 19  floors in front cabins      pilot house +                   rear cabins
                                                   main cabin (rear view)                                                  

Technical compartment

Below pilot house.
Contains batteries and electric equipment

normal: under stairs (removable)
full access: from above, removing the floor

2017 11 26 - normal access

2016 11 19 full access from above

Front bunker

For sails, anchor and chain (during oceanic navigation), etc.

Access: deck hatch + door in front cabin (opening above waterline)

2016 11 19                                                                                      2016 06 16

Rear bunker

For jerrycans, deck gear, payload...

Access: roof hatch + door in rear cabin (opening above waterline)
2 lateral trunks accessible from outside.

2015 05 04 30                                2015 04 30

2015 05 24. Propeller bracket         2016 05 03. Lateral storage


Foam sandwich 34mm thick
Core: 30mm pvc foam, skins: fiberglass epoxy, 1000g+600g standard, 1000+1000 on pathways (for abrasion).

panel by panel, stratified junctions (no space to build the complete deck)

roof - walls junction:roof panels laying on horizontal plates (10cm wide; epoxy glass + thin plywood),
bonding inside, stratification outside.

2016 05 03 pathways

2016 11 19 roof - side walls

2016 11 19 front deck

Roof :panels laying on horizontal plates (10cm wide; epoxy glass + thin plywood), bonded inside, stratified outside

2017 07 22 Roof - panels                 bonding                                       roof -closed


Main: Rocna anchor 33kg, 100m grade 40 chain 10mm, Lofrans Tigres windlass
Double bunker:

Upper bunker (below deck): to keep dirty chain and anchor.
Lower bunker (bottom of front bunker): for clean chain, for a lower center of mass (anchor remains in upper bunker)
Chain transfer: through a tube between bunkers, using windlass or manually.

2016 11 19 chain bunkers.  both bunkers together                      2017 11 26 - transfer tube
  right: upper bunker,           before closing the bulkhead
  left lower bunker


Rotating bow support
On elevated plane
Easier anchor handling (no need to bend)
Nothing protrudes when folded

Composite anchor roller
110mmPEHD tube 10mm thick, glass epoxy core

2016 11 19 rotating bow support     2017 11 26 - folding...        blocked

Pilot house

Steering from inside,2 sea berths for the crew

Construction: light foam panels, inverted front shields, divided into small windows (for robustness)

2017 08 31 construction                2017 11 26 outside   

2017 11 26 inside
  watch table
  seat above buffer tank

Cabins and berths

2 front cabins (can be separated or joined) and 2 rear cabins.

Individual berths,
can be joined to form 3 double beds
each berth can be folded (or removed) to free the access to the front and rear bunkers.

Capacity: 10 persons
2 persons in each cabin = 8 passengers
2 crew members in the pilot house.

Transformable cabins: can be used as sleeping rooms or load bunkers.

Front cabins

2017 11 26 - front cabins              

2017 11 26 empty            gangways above load        4 berths                          double bed

Rear cabins

2017 11 26  port                starboard
  door to rear bunker          hatch to rear bunker

2017 11 26 empty            gangways above load        berths - folded                   berths in position    


2 toilets
accessible from saloon and rear cabins
WC + wash basin + shower
independent air circuit (2 air vents )

2017 11 26 view from rear cabin


3 functions: kitchen + dining room + living room

dining room: central bar (high table) + individual stools

living room: 3 beanbags XXL

kitchen: sinks + stove + long work table

2017 11 26

                                                              FRA sails-4-south-fra  ESP