Spirit of Acorn . com
Creating a small keel yacht designed for the soul, not the ego
Skyline of Melbourne, Victoria, Australia from Spirit of Acorn
Building
From the Gallery page you'll find links to photos taken during construction. The processes will be self evident, but I've included an outline below:
LOFTING
Although I managed to obtain a set of plans from Luke, there was no Table of Offsets. Accordingly Ray Cole's initial calculations were based on measurements from the original drawings, and then subject to modification to reach the new form. From these drawings Ray produced a Table of Offsets. With 3 large 2.4m x 1.2m sheets of particle board bolted to the factory floor, a grid was drawn, then the lines drawn full size to check for errors, and to allow building the building stations (moulds).
BUILDING MOULDS
These were designed from the full size loftings, and fabricated in pine.
STRONGBACK
A "strongback" frame was bolted to the factory floor, and the moulds very carefully set up on braced legs at their stations, so the the hull could be built upside down.
STEM
The Stem is the structural member inside the bow. This was laminated from strips of Tasmanian Oak and glued with epoxy. Lamination was done against the shape of the bow drawn on the lofting boards. Lamination could only be done 3 strips at a time, due to their strength. After the first 3, I got substantial springback. So I over compensated on the next 3, but they held their (wrong) shape. The rest of the laminations recovered the situation. When finished the Stem was cut into the Building Moulds and the front end also bolted to the floor.
TRANSOM
The Transom is both raked and curved, and it was laminated from 2 layers of mahogany faced marine ply on a jig built for the purpose.
HOG
The Hog is the structural lengthwise backbone, and was built of up to 3 layers of Tasmanian Oak, and directly laminated into cutouts in the Building Moulds. Plastic sheet ensured no epoxy glue would bond the Hog to the Moulds, and the Hog was screwed to the Moulds from inside. The Hog and Stem were notched and glued to each other, and the Transom attached to the Hog at the rear.
SHEER CLAMP
The Sheer Clamp, again of Tasmanian Oak, runs at the edge of the deck from Bow to Transom. It was notched into the Moulds and attached at the Stem and the Transom.
FAIRING
All Moulds and the Stem, Hog and Transom, were Faired ready for planking.
HULL SKIN
The Hull skin was constructed of strips of Western Red Cedar, in unscarfed 6 metre lengths. Each was 35mm wide and 13mm thick, and they were machined to a tongue and groove profile. Strips were quarter sawn, and beautifully finished, thanks to Oregon Sales in Queensland who prepared them. All strips were colour matched and numbered so that colour variations seen in the cabin would be gradual.
FIRST PLANK
A Master Plank was located at around the centre point of the Moulds. Temporarily screwed, I then worked upwards towards the Hog, using Purbond waterproof expanding polyurathane glue between planks, and epoxy glue at all stress points where planks met Hog, Stem, Transom or Sheer Clamp. The Purbond greatly speeded the process, and has the additional benefit that hardened excess is easily removed without plank damage. Planking up was a one person operation, but planking down was more difficult, and my wife Gina helped with this part.
KEEL and SKEG STUBS
Once planking was finished, planks were routed out along the Hog to allow lamination of additional Tasmanian Oak to the same level as the hull skin. These laminations were continued where they would form the Stubs for keel and rudder skeg.
KEEL
The Keel (of lead with 5% antimony), and weighing over 600kg, was subcontracted along with its production tooling. Stainless steel bolts are cast into it.
The RUDDER SKEG was laminated from 54 pieces of marine ply, with embedded bolts. It is shown temporarily fitted early on, later it was heavily laminated with fibreglass in epoxy before fitting.
PLANK NAMING
Before fibreglassing the outside of the hull, I invented a new tradition. A Plank was named on the port side bow for the key people involved with the Project. Jim DeWitt Snr. for the original design; Bob Andrews for The Story; Luke Lukavich for the plans and and letting me come sailing on his 50 year old Acorn in Monterey; Ray Cole for the new design; the "family" plank for me, wife Gina (fellow planker), grown up kids Anuschka, Tobi and Amber, and Juno the dog, who sometimes hangs around while I work; and finally Rob and Jan Cook. Rob gave me the Wooden Boats containing the original article, and both are regular supporters and helpers as needed. The names will be right way up when Spirit of Acorn is sailing, but never seen as the hull is painted. Ray Cole visited to inspect The Names.
GLASSING
The keel and rudder stubs were Glassed first, then the sheathing of the hull started from the transom. The transom itself is not glassed, the mahogany laminate will be finished many coats deep in two pot clear.
HULL FAIRING
Starting on the port side, the hull was Faired. Not much filler was required, but the process is laborious. Traditionally this is done with "long boards", also known as "torture boards" by those who have used them. I found that the edges of long boards did more damage than good, presumably because the hull is small and very "curvy". My solution was suggested by Mike Akers, my panel beater friend. To get the excellent results he achieves, he sands using flexible pieces of high density foam that conform to the local curve This worked very well. Once the hull was faired (the photo on the left), three coats of epoxy resin were rolled on to seal the filler, then high build water based epoxy sealer/undercoat, followed by a copper/epoxy antifoul.
ROLLING THE HULL
The hull was rolled over, with lots of help, onto a couple of mattresses ready for internal finishing. First the supporting legs on the temporary building frames had to be undone (me underneath, Amber in foreground). Next the rolling crew with chain block over, and safety line to the edge of the factory ceiling. A few anxious moments, especially on my part, and she was over. Once over the crew of family, friends and neighbours toasted the milestone. Ray Cole turned up later to check her out (he was all smiles like me).
REMOVING THE FRAMES AND GLUE RUNS
The hull is very pretty, with just the right amount of sheer (the rising deck curve towards the bow). The building frames were progressively removed as I scraped off the internal glue runs, before sheathing the inside, then starting on the fitout. Great care was taken removing the glue runs as the cabin is to be finished clear with timber exposed (under fibreglass epoxy). Although the expanding glue is much softer than epoxy, I used a scrapping tool made from a hacksaw blade to cut under the glue runs. As it turned out, 40 grit on a third sheet obital sander had to be used to finish the job (then working up in grades to 80) and may have been a better and faster approach from the start. Building frames were progressively removed with spreaders inserted at the shear. The hull proved quite stable, and soon I will glass the inside. Then there are laminated frames to make and bulkheads.
INTERNAL GLASSING
Just as the hull was glassed outside, it was glassed inside. Ray Cole's layup schedule specified a heavily glassed oval section over a large area of the hull to spread the stresses of the keel. The beautiful cedar is still clearly visible through the glass/epoxy throughout the yacht.
KEEL FRAMES AND BULKHEADS
Keel frames were laminated and installed. Bulkheads were cut and installed. All were additionally glassed to the hull to Ray's specification.
CABIN BUNKS, COCKPIT AND DECK FRAMING
Plywood was used to fabricate the bunks, and later the cockpit. The cockpit sole and sides were glassed. Deck framing was installed. Chain Plates, heavily glassed themselves and bonded to the inside of the hull, were added to support the mast rigging,
RUBBING RAILS
These were added largely without screws before the deck so that clamps could be used onto the inside of the sheer clamp (Tasmanian oak).
DECK
The deck of 5mm ply was installed. It was epoxy saturated with joints glassed. Later the laid deck would be glued on, taking thickness to around 12mm.
CABIN SIDES
These are fabricated from 6mm mahogany veneered marine ply. Additional framing in Tasmanian oak was added.
CABIN ROOF
This is curved, and was laminated on a specially constructed jig from three layers of 5mm marine ply, glassed inside and out, and fitted over the cabin side, centre bulkhead, and a front panel.
COCKPIT COMBINGS
These are laminated from two layers of solid Fijian mahogany glued with epoxy.
LAID DECK
The laid deck is of Queensland White Beech. The strips were machined to 20mm x 7mm, and epoxy glued to the ply deck. The gaps in between, typically filled with Sikaflex, were instead filled with epoxy glue containing 10% graphite powder. The graphite acts as a "sun screen" to protect the epoxy. Joints against the rubbing strip, cabin side, and combings, are filled with flexible sealant. The finished deck was sealed with a water based sealer.
MAKING THE SKEG FOOT
A manganese bronze skeg foot was specified. The rudder shaft would fit into this as its bottom bearing. A pattern replica of the final foot was prepared, slightly oversize to allow for shrinkage, and sub-contracted for casting. It was then machined with mounting screw holes and shaft socket.
MAKING THE SKEG
The basic skeg, with imbedded attachment bolts has previously been fabricated. Completion required heavy glassing including a recess for mounting the skeg foot.
FITTING THE KEEL
The keel was planed back to proper dimensions (it had been cast around 30 kg overweight), then coated with epoxy resin and epoxy undercoat. Spirit was hoisted towards the factory roof on slings, and the keel manhandled underneath. All bolts lined up properly, and the yacht, with epoxy glue on the keel, was lowered onto the keel and bolts secured. Resin was also injected into the bolt holes.
FITTING THE SKEG
The skeg was similarly glued and bolted to the hull, and the joint glassed.
FABRICATING AND GLASSING THE RUDDER
The rubber was fabricated of plywood, shaped to a foil (including the skeg) and heavily glassed. Considerable effort went into ensuring that the skeg curved around the rudder stock with only 3mm clearance.
BUILDING THE PUSHPIT AND PULPIT
These had been subcontracted earlier, and were custom made to fit. Staunchions were fitted along the side between, and safety lines added.
RIGGING THE MAST
South East Yacht services fabricated and rigged the mast. Initial fitting was done in the carpark beside my factory.
PAINTING
I painted the inside in clear varnish (including all inaccessible areas during construction), the cabin roof, bunk tops and storm boards in an white acrylic, and cockpit and cabin top in oil based paving paint (non slip and easily repainted). Cabin sides, combings, and rubbing strips were varnished over epoxy. The transom was varnished with water based epoxy clear over epoxy. Decks were sealed with a water based finish. Underwater areas had been previously finished in copper epoxy over water based high build epoxy undercoat. The keel, skeg and rudder were now similarly finished. The hull was sprayed in two pot white by Bob Peckham (who painted Australia II and came up with the winged keel disguise pattern I'm told).
And all that took around 10 years of part time work!
From the Gallery page you'll find links to photos taken during construction. The processes will be self evident, but I've included an outline below:
LOFTING
Although I managed to obtain a set of plans from Luke, there was no Table of Offsets. Accordingly Ray Cole's initial calculations were based on measurements from the original drawings, and then subject to modification to reach the new form. From these drawings Ray produced a Table of Offsets. With 3 large 2.4m x 1.2m sheets of particle board bolted to the factory floor, a grid was drawn, then the lines drawn full size to check for errors, and to allow building the building stations (moulds).
BUILDING MOULDS
These were designed from the full size loftings, and fabricated in pine.
STRONGBACK
A "strongback" frame was bolted to the factory floor, and the moulds very carefully set up on braced legs at their stations, so the the hull could be built upside down.
STEM
The Stem is the structural member inside the bow. This was laminated from strips of Tasmanian Oak and glued with epoxy. Lamination was done against the shape of the bow drawn on the lofting boards. Lamination could only be done 3 strips at a time, due to their strength. After the first 3, I got substantial springback. So I over compensated on the next 3, but they held their (wrong) shape. The rest of the laminations recovered the situation. When finished the Stem was cut into the Building Moulds and the front end also bolted to the floor.
TRANSOM
The Transom is both raked and curved, and it was laminated from 2 layers of mahogany faced marine ply on a jig built for the purpose.
HOG
The Hog is the structural lengthwise backbone, and was built of up to 3 layers of Tasmanian Oak, and directly laminated into cutouts in the Building Moulds. Plastic sheet ensured no epoxy glue would bond the Hog to the Moulds, and the Hog was screwed to the Moulds from inside. The Hog and Stem were notched and glued to each other, and the Transom attached to the Hog at the rear.
SHEER CLAMP
The Sheer Clamp, again of Tasmanian Oak, runs at the edge of the deck from Bow to Transom. It was notched into the Moulds and attached at the Stem and the Transom.
FAIRING
All Moulds and the Stem, Hog and Transom, were Faired ready for planking.
HULL SKIN
The Hull skin was constructed of strips of Western Red Cedar, in unscarfed 6 metre lengths. Each was 35mm wide and 13mm thick, and they were machined to a tongue and groove profile. Strips were quarter sawn, and beautifully finished, thanks to Oregon Sales in Queensland who prepared them. All strips were colour matched and numbered so that colour variations seen in the cabin would be gradual.
FIRST PLANK
A Master Plank was located at around the centre point of the Moulds. Temporarily screwed, I then worked upwards towards the Hog, using Purbond waterproof expanding polyurathane glue between planks, and epoxy glue at all stress points where planks met Hog, Stem, Transom or Sheer Clamp. The Purbond greatly speeded the process, and has the additional benefit that hardened excess is easily removed without plank damage. Planking up was a one person operation, but planking down was more difficult, and my wife Gina helped with this part.
KEEL and SKEG STUBS
Once planking was finished, planks were routed out along the Hog to allow lamination of additional Tasmanian Oak to the same level as the hull skin. These laminations were continued where they would form the Stubs for keel and rudder skeg.
KEEL
The Keel (of lead with 5% antimony), and weighing over 600kg, was subcontracted along with its production tooling. Stainless steel bolts are cast into it.
The RUDDER SKEG was laminated from 54 pieces of marine ply, with embedded bolts. It is shown temporarily fitted early on, later it was heavily laminated with fibreglass in epoxy before fitting.
PLANK NAMING
Before fibreglassing the outside of the hull, I invented a new tradition. A Plank was named on the port side bow for the key people involved with the Project. Jim DeWitt Snr. for the original design; Bob Andrews for The Story; Luke Lukavich for the plans and and letting me come sailing on his 50 year old Acorn in Monterey; Ray Cole for the new design; the "family" plank for me, wife Gina (fellow planker), grown up kids Anuschka, Tobi and Amber, and Juno the dog, who sometimes hangs around while I work; and finally Rob and Jan Cook. Rob gave me the Wooden Boats containing the original article, and both are regular supporters and helpers as needed. The names will be right way up when Spirit of Acorn is sailing, but never seen as the hull is painted. Ray Cole visited to inspect The Names.
GLASSING
The keel and rudder stubs were Glassed first, then the sheathing of the hull started from the transom. The transom itself is not glassed, the mahogany laminate will be finished many coats deep in two pot clear.
HULL FAIRING
Starting on the port side, the hull was Faired. Not much filler was required, but the process is laborious. Traditionally this is done with "long boards", also known as "torture boards" by those who have used them. I found that the edges of long boards did more damage than good, presumably because the hull is small and very "curvy". My solution was suggested by Mike Akers, my panel beater friend. To get the excellent results he achieves, he sands using flexible pieces of high density foam that conform to the local curve This worked very well. Once the hull was faired (the photo on the left), three coats of epoxy resin were rolled on to seal the filler, then high build water based epoxy sealer/undercoat, followed by a copper/epoxy antifoul.
ROLLING THE HULL
The hull was rolled over, with lots of help, onto a couple of mattresses ready for internal finishing. First the supporting legs on the temporary building frames had to be undone (me underneath, Amber in foreground). Next the rolling crew with chain block over, and safety line to the edge of the factory ceiling. A few anxious moments, especially on my part, and she was over. Once over the crew of family, friends and neighbours toasted the milestone. Ray Cole turned up later to check her out (he was all smiles like me).
REMOVING THE FRAMES AND GLUE RUNS
The hull is very pretty, with just the right amount of sheer (the rising deck curve towards the bow). The building frames were progressively removed as I scraped off the internal glue runs, before sheathing the inside, then starting on the fitout. Great care was taken removing the glue runs as the cabin is to be finished clear with timber exposed (under fibreglass epoxy). Although the expanding glue is much softer than epoxy, I used a scrapping tool made from a hacksaw blade to cut under the glue runs. As it turned out, 40 grit on a third sheet obital sander had to be used to finish the job (then working up in grades to 80) and may have been a better and faster approach from the start. Building frames were progressively removed with spreaders inserted at the shear. The hull proved quite stable, and soon I will glass the inside. Then there are laminated frames to make and bulkheads.
INTERNAL GLASSING
Just as the hull was glassed outside, it was glassed inside. Ray Cole's layup schedule specified a heavily glassed oval section over a large area of the hull to spread the stresses of the keel. The beautiful cedar is still clearly visible through the glass/epoxy throughout the yacht.
KEEL FRAMES AND BULKHEADS
Keel frames were laminated and installed. Bulkheads were cut and installed. All were additionally glassed to the hull to Ray's specification.
CABIN BUNKS, COCKPIT AND DECK FRAMING
Plywood was used to fabricate the bunks, and later the cockpit. The cockpit sole and sides were glassed. Deck framing was installed. Chain Plates, heavily glassed themselves and bonded to the inside of the hull, were added to support the mast rigging,
RUBBING RAILS
These were added largely without screws before the deck so that clamps could be used onto the inside of the sheer clamp (Tasmanian oak).
DECK
The deck of 5mm ply was installed. It was epoxy saturated with joints glassed. Later the laid deck would be glued on, taking thickness to around 12mm.
CABIN SIDES
These are fabricated from 6mm mahogany veneered marine ply. Additional framing in Tasmanian oak was added.
CABIN ROOF
This is curved, and was laminated on a specially constructed jig from three layers of 5mm marine ply, glassed inside and out, and fitted over the cabin side, centre bulkhead, and a front panel.
COCKPIT COMBINGS
These are laminated from two layers of solid Fijian mahogany glued with epoxy.
LAID DECK
The laid deck is of Queensland White Beech. The strips were machined to 20mm x 7mm, and epoxy glued to the ply deck. The gaps in between, typically filled with Sikaflex, were instead filled with epoxy glue containing 10% graphite powder. The graphite acts as a "sun screen" to protect the epoxy. Joints against the rubbing strip, cabin side, and combings, are filled with flexible sealant. The finished deck was sealed with a water based sealer.
MAKING THE SKEG FOOT
A manganese bronze skeg foot was specified. The rudder shaft would fit into this as its bottom bearing. A pattern replica of the final foot was prepared, slightly oversize to allow for shrinkage, and sub-contracted for casting. It was then machined with mounting screw holes and shaft socket.
MAKING THE SKEG
The basic skeg, with imbedded attachment bolts has previously been fabricated. Completion required heavy glassing including a recess for mounting the skeg foot.
FITTING THE KEEL
The keel was planed back to proper dimensions (it had been cast around 30 kg overweight), then coated with epoxy resin and epoxy undercoat. Spirit was hoisted towards the factory roof on slings, and the keel manhandled underneath. All bolts lined up properly, and the yacht, with epoxy glue on the keel, was lowered onto the keel and bolts secured. Resin was also injected into the bolt holes.
FITTING THE SKEG
The skeg was similarly glued and bolted to the hull, and the joint glassed.
FABRICATING AND GLASSING THE RUDDER
The rubber was fabricated of plywood, shaped to a foil (including the skeg) and heavily glassed. Considerable effort went into ensuring that the skeg curved around the rudder stock with only 3mm clearance.
BUILDING THE PUSHPIT AND PULPIT
These had been subcontracted earlier, and were custom made to fit. Staunchions were fitted along the side between, and safety lines added.
RIGGING THE MAST
South East Yacht services fabricated and rigged the mast. Initial fitting was done in the carpark beside my factory.
PAINTING
I painted the inside in clear varnish (including all inaccessible areas during construction), the cabin roof, bunk tops and storm boards in an white acrylic, and cockpit and cabin top in oil based paving paint (non slip and easily repainted). Cabin sides, combings, and rubbing strips were varnished over epoxy. The transom was varnished with water based epoxy clear over epoxy. Decks were sealed with a water based finish. Underwater areas had been previously finished in copper epoxy over water based high build epoxy undercoat. The keel, skeg and rudder were now similarly finished. The hull was sprayed in two pot white by Bob Peckham (who painted Australia II and came up with the winged keel disguise pattern I'm told).
And all that took around 10 years of part time work!
