Practical Boat Owner — November 2017

practical

Masking tape stuck over the chines

showed up any hollows or flats

It’s the same idea, but easier than drawing

a grid on the hull skin.

Another technique we found useful was

a laser level. These project a long, straight

line which when shone onto an irregular

surface shows any lumps and bumps

quite well. We found it works best when

the laser is angled obliquely to the

surface. A lower tech method is to use

strips of tape, which just like the camber

stripe on a sail help to show if a curve is

fair or not.

A set of templates had got us close to

the shape we needed, but there were

still some areas which needed

attention. Approximately half way

along the chine were some large flat

spots owing to there being insufficient

timber to completely build the curve,

and a few other errors were apparent

in other areas where we had been too

enthusiastic with the plane.

Rather than adding more timber, we

decided that the shape was close

enough to allow us to make up the

difference with fairing filler. We used

WEST SYSTEM low density

microballoon blend in a stiff mix of

epoxy to build up a layer of filler on

the areas in question. After letting it

cure for 24 hours we sanded it back,

first using a random orbital sander to

remove obvious high points, followed

by longboards and sandpaper pulled

like a strap across the chine.

This was mostly successful, but we

needed a further two applications of

filler on the largest flat area. Building

up smooth layers of epoxy is not easy

• if you make the mix stiff enough to
  support thick layers of 10mm or more
  then you risk a rough surface and
  voids in the filler. A less stiff mix gives
  a better finish, but you then need to
  build up layers and ensure the
  previous layer is clean and keyed to
  ensure good adhesion.

A laser level shone obliquely showed up
any lumps or depressions on the hull skin

Shaping

the chines

A random-orbit sander sped up the

fairing of the chines

Beyond general fairing, there were three

main areas on the boat which needed

special attention. The first is the transition

from the midships bottom panels, which

are 6mm ply, to the 4mm ply bow panels.

This results in a 2mm step.

We removed the majority of the difference

by using a long plane to taper the 6mm

ply over a distance of around 40cm,

before filling any hollows with fairing filler.

The 4mm ply tends to scallop slightly

around the fixings, so filler is inevitable.

Further aft, we had used two small 6mm

panels to fill the gap between the

midships panels and the aft bottom panel.

Smoothing the panels

As they were small it had proved

impossible to make them continue the

gentle bend of the bottom panels, so we

glued them in place and used a plane to

remove any high spots. As they were

mostly too high at the edges, we didn’t

need much filler.

The third and final area was at the bow,

where the bow panels meet the stem. The

ply had scalloped quite badly here where

we had used screws to pull it into shape,

so we cautiously planed the top of the

bumps, taking care not to go through

more than one laminate of plywood, and

filled the hollows.

A longboard

(sometimes known as

a torture board!) was

painful but effective

A longboard showed

up areas that needed

extra filling