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proto-4 was to be, as near as possible, a full pre-production prototype. Most of the boat and transport issues had been sorted with proto-3 and most of proto-4’s development work related to ‘production’ – to be able to make each boat with the minimum of hassle and the maximum of reliability. I decided that, mostly down to the small size of the workshop, we would make the ROCAT in batches of 3.

The first major job was to install electric programmable heating in the main moulds in order to post-cure the parts. This improves the part’s strength and increases its tolerance of high temperature – a dark hull sitting in the sun gets very hot and, without such treatment, it can melt!

Then there were jigs and foam moulds and more hull frames to be made.

The hull mould had developed some faults, so we took time out to refurbish it, and then take reference plugs from the refurbished mould to simplify the production of further moulds later.

The ROCAT’s finish was the subject of much debate. Conventionally, a coloured gelcoat would be applied to the mould before the glass, and no post-finishing would be required. But there were disadvantages in the ROCAT’s case concerning resin compatibility, moulding flaws repair and limited colours. Also, committing to particular colours at the moulding stage made the production workflow less flexible. So we sprayed epoxy primer into the mould and then used very tough two-pack automotive paints for the finish – and it looked gorgeous!

Once completed, proto-4 was a real joy to use because everything worked just as it should, from loading it on to the car, to assembling it on the harbour slipway, to rowing out across the bay whatever the conditions.

Installing electric heating on the hull mould
Installing electric heating on the hull mould
Modified hull mould with enclosed insulation
Modified hull mould with enclosed insulation
Mounted on strong wheeled frames
Mounted on strong wheeled frames
Opened flat to provide better access
Opened flat to provide better access
Hull materials - special biaxial non-woven glass fibre sandwiches Soric resin infusion medium
Hull materials - special biaxial non-woven glass fibre sandwiches Soric resin infusion medium
Foam ends were produced to concentrate the pressure right in to the ends and add strength
Foam ends were produced to concentrate the pressure right in to the ends and add strength
The hull mould with glass and bag in place
The hull mould with glass and bag in place
Creating reference plugs from the refurbished hull mould
Creating reference plugs from the refurbished hull mould
Reference plugs either side of the refurbished hull mould
Reference plugs either side of the refurbished hull mould
Closeup of the refurbished hull mould
Closeup of the refurbished hull mould
Skeg prototypes produced using polyurethane casting resin
Skeg prototypes produced using polyurethane casting resin
Skeg prototypes investigating weight and strength difference if made hollow
Skeg prototypes investigating weight and strength difference if made hollow
More improvisation - this is a resin degasser based on a Lidl's pressure  cooker costing 1/10th the commercial product
More improvisation - this is a resin degasser based on a Lidl's pressure cooker costing 1/10th the commercial product
Spray-painting a hull with two-pack automotive paint
Spray-painting a hull with two-pack automotive paint
The frames were an important part of the production infrastructure -
The frames were an important part of the production infrastructure -
they were used to align the crossbeam sockets accurately; to spray the whole hulls in one go, and to store the hulls up out of the way pending shipping
The CAD for the modified crossbeam plug
The CAD for the modified crossbeam plug
CNC machined plug for the replacement crossbeam mould - it is machined out of an extremely dense, fine-grained plastic material
CNC machined plug for the replacement crossbeam mould - it is machined out of an extremely dense, fine-grained plastic material
A crossbeam foam blank with half its mould
A crossbeam foam blank with half its mould
This warm cupboard was used to cure the foam blanks and small epoxy parts
This warm cupboard was used to cure the foam blanks and small epoxy parts
A foam blank for the rear crossbeam - tubular carbon fibre braid is fed over the blank before it goes into the mould
A foam blank for the rear crossbeam - tubular carbon fibre braid is fed over the blank before it goes into the mould
Moulding a crossbeam using tubular carbon fibre braid  formed on a foam blank
Moulding a crossbeam using tubular carbon fibre braid formed on a foam blank
Moulding crossbeams using vacuum resin infusion - once the infusion is complete the ports are opened with a head of resin
Moulding crossbeams using vacuum resin infusion - once the infusion is complete the ports are opened with a head of resin
Epoxy-primed crossbeams waiting for paint
Epoxy-primed crossbeams waiting for paint
Crossbeams finished in metallic 2-pack automotive paint
Crossbeams finished in metallic 2-pack automotive paint
The system used to produce the sockets which was ultra simple and effective
The system used to produce the sockets which was ultra simple and effective
A socket ready to be fixed in the hull
A socket ready to be fixed in the hull
The jig to rout the hole in hull for a socket
The jig to rout the hole in hull for a socket
Hole in hull for a socket - the vacuum bag is removed through these holes
Hole in hull for a socket - the vacuum bag is removed through these holes
The hull is stuffed with built-in buoyancy
The hull is stuffed with built-in buoyancy
The crossbeams drop into tapered sockets and spring-loaded pins hold them in
The crossbeams drop into tapered sockets and spring-loaded pins hold them in
The frame to support the seatdeck while it is being spray painted
The frame to support the seatdeck while it is being spray painted
The CNC machined plug for the yoke mould
The CNC machined plug for the yoke mould
The yoke mould and finished carbon fibre part - the yoke is the very stiff component which goes across the seatdeck  to take ...
The yoke mould and finished carbon fibre part - the yoke is the very stiff component which goes across the seatdeck to take the swingarm cantilever loads
This hefty steel jig is used bond the yoke and bottom bracket precisely
This hefty steel jig is used bond the yoke and bottom bracket precisely
Making swingarm mould from 2 handmade plugs
Making swingarm mould from 2 handmade plugs
Crossbeams, seatdeck, yoke and track
Crossbeams, seatdeck, yoke and track
This is a fixed pin on the side of the front crossbeam -  it locates, and securely attaches, the seatdeck to the crossbeam
This is a fixed pin on the side of the front crossbeam - it locates, and securely attaches, the seatdeck to the crossbeam
The pin on the side of the rear crossbeam is spring-loaded - it just takes seconds to attach, or detach, the seatdeck
The pin on the side of the rear crossbeam is spring-loaded - it just takes seconds to attach, or detach, the seatdeck
Schematic of the ROCAT rowlock with swingarm, link and footbar
Schematic of the ROCAT rowlock with swingarm, link and footbar
The minimalist rowlock on ROCAT prototype #4 - this robust solution was changed to eliminate anything that might be dropped a...
The minimalist rowlock on ROCAT prototype #4 - this robust solution was changed to eliminate anything that might be dropped and lost
Rear of ROCAT proto-4 rowlock showing link attachment
Rear of ROCAT proto-4 rowlock showing link attachment
The rowlock bears on an extremely tough Vesconite sleeve and the pin is spring-loaded
The rowlock bears on an extremely tough Vesconite sleeve and the pin is spring-loaded
Front of ROCAT proto-4 rowlock showing spring-loaded oar pin engaged in the rotation limiter
Front of ROCAT proto-4 rowlock showing spring-loaded oar pin engaged in the rotation limiter
Jig to weld an eye onto a rowlock for the production boat
Jig to weld an eye onto a rowlock for the production boat
Improvising a footbar strength and flexure test rig
Improvising a footbar strength and flexure test rig
The crossbeams and footbar nest in the car roof tray and the inverted seatdeck forms the lid
The crossbeams and footbar nest in the car roof tray and the inverted seatdeck forms the lid
Ease of transportation was important - the whole boat sits on the roof of a standard family car
Ease of transportation was important - the whole boat sits on the roof of a standard family car
The ROCAT's parts
The ROCAT's parts
The ROCAT's assembly sequence - the crossbeams are put out first
The ROCAT's assembly sequence - the crossbeams are put out first
- the front crossbeam fits in to the front socket on the first hull
- the front crossbeam fits in to the front socket on the first hull
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