Building a Bread-and-Butter Model Boat Hull from Laminated Layers

A bread-and-butter hull is built from a stack of boards, called lifts, each cut to the outline of the hull at one level. The boards are the “bread” and the glue between them is the “butter”. Once the glue has set, the stepped stack is carved and sanded into a smooth hull. It is one of the oldest ways to make a model hull. Shipwrights used lift models to work out hull shapes long before models were a hobby, and it is still a good choice for scratch builders today.

This guide covers the whole process, from choosing wood to carving the finished shape. For how it compares with other methods, see our overview of making a model boat hull.

Why build a hull this way

The main alternative for a carved hull is a solid block. Bread-and-butter has some clear advantages over it:

Less waste and lower cost. A large solid block of good carving wood is hard to find and expensive. Ordinary boards are not.
Less carving. Each lift is already cut close to the hull’s shape at its level, so you only remove the steps between layers.
Built-in reference lines. The glue lines follow waterlines (or buttock lines), which helps you see whether the hull is symmetrical as you carve.
Hollowing before assembly. You can cut out the middle of each lift before glue-up, which is much easier than gouging out a solid hull. This makes the method practical for working models.
Strength. Builders on the Model Boat Mayhem forum note that a well-made laminated hull is usually watertight, doesn’t twist the way a lightly framed planked hull sometimes can, and stands up well to knocks at the pond.

There are downsides too:

Weight. An unhollowed hull is heavy. Even a hollowed one is usually heavier than a planked or fibreglass hull of the same size.
Thick lifts on older plans. Some published plans draw lifts 25 mm (1 in) thick or more. That suits a static model but leaves little room inside a working one unless you hollow carefully.
Symmetry takes care. You have to carve both sides to match. A lopsided hull is easy to spot.
Some waste. Cutting curved shapes from rectangular boards still leaves offcuts.

Waterline lifts or buttock lifts

Most bread-and-butter hulls use waterline lifts: horizontal layers stacked from keel to deck, each cut to the shape of a waterline from the half-breadth plan. This is the traditional approach and the easiest to understand from a plan.

The other option is buttock lifts: vertical layers running fore and aft, parallel to the centreline, cut to the buttock lines on the sheer (profile) plan. The builder of a 1:16 motor launch on building-model-boats.com used ten buttock lifts of 19 mm pine and said they were “sold” on the approach. Because each lift on one side has a mirror-image twin on the other, you can cut matching pairs together, which helps symmetry. The profile of the hull, including the sheer, is also built into every lift.

As a rough guide:

Choose waterline lifts for most ship hulls, flat-bottomed boats and anything with a strong flare or tumblehome, where the plan view shape changes a lot with height.
Consider buttock lifts for narrow, deep hulls such as launches and some powerboats, where the profile matters most and you want matched pairs.

Choosing wood for the lifts

You want wood that carves cleanly, holds its shape and glues well. Common choices include:

Basswood and lime: fine, even grain and easy to carve. A good all-round choice.
Jelutong and obeche: soft, light and easy to carve, popular for pattern making and working models.
Pine: cheap and easy to find. Yellow pine was the traditional timber for bread-and-butter hulls, but good-quality stock is now expensive. Ordinary construction pine works if you choose boards carefully.
Balsa: very light, which helps a working model, but soft and easily dented, so it normally needs sheathing.

When buying or picking boards:

Avoid knots where the outside of the hull will be. Knots are much harder than the wood around them, so they make it difficult to sand a fair curve, and resin in pine knots can spoil the finish. A knot in the waste or in the part you will hollow out is fine.
Look for straight grain. It carves more predictably.
Use the flattest boards in the middle of the stack. Mild cupping can be managed by orienting boards so their tendency to curl works against the next layer. Twisted boards are best left out.
Mix grades if it helps. The Model Shipwright tutorial used select pine for the lower lifts, where most of the shaping happens, and cheaper boards for the top lifts, much of which is cut away.
Keep the grain running the same way. Mark each piece so its bow end matches the same end of the original board. Consistent grain direction makes carving easier.

Let the wood settle in your workshop for a while before you start, so it is close to the humidity it will live in. For more on species and suppliers, see our guide to model boat timber and planking supplies.

Matching lift thickness to the plan

Ideally, each lift is exactly as thick as the spacing between waterlines on the plan, so every glue line falls on a drawn waterline. In practice, the plan’s spacing and the thickness of the boards you can buy rarely match. There are two ways around it:

Plane the boards to the plan’s spacing. Accurate, but it needs a thicknesser or a lot of hand planing, and each lift may need a different thickness.
Redraw the waterlines to suit your boards. Draw new horizontal lines on the body plan at your board thickness (scaled to your model), then take new half-breadths from the body plan sections to plot fresh waterline shapes. It’s more drawing, but it lets you use standard stock.

A compromise many builders use is to keep standard boards and let a lift sit slightly above or below its nominal waterline, cutting that lift a little oversize so there is enough wood to carve. The Model Shipwright tutorial does this with standard 1x8 boards (about 19 mm, or 3/4 in, thick). Thinner lifts give a smoother stepped shape and less carving but mean more glue lines and more cutting. Thicker lifts are quicker to stack but leave bigger steps to remove.

Making the lift templates

Print or trace the plan at your model’s scale. Check the scale by measuring a known dimension in both length and width, since copiers and printers can stretch an image slightly. Our guide to scaling model boat plans up or down covers resizing and checking prints. Make one template per lift. For waterline lifts, flip the half-breadth plan to draw the full width of each waterline, or cut each lift from a doubled board.

On every template, mark:

the centreline
the station lines from the plan
the lift number and which way is forward

Fix the templates to the wood with a repositionable spray adhesive (see transferring model boat plans to wood for other methods), lining up the template’s centreline with a centreline drawn on the board.

Which line to cut each lift to

This is the step that confuses most first-time builders. Each lift has two outlines: the waterline at its top face and the waterline at its bottom face. Cut each lift to whichever of the two is larger, so there is wood to carve down to the smaller one.

Below the widest part of the hull, the upper waterline is usually larger, so that is the cutting line.
If the hull has tumblehome (narrowing above the widest point), the lower waterline of those upper lifts is larger, so cut to that.
Near the bow and stern, check both lines along their whole length. The larger one can swap partway along.

Draw the other (smaller) line on the template too. It shows how far to carve later.

Inner lines for hollowing

If you plan to hollow the hull, draw an inner cutting line on each lift. Offset it inside the smaller of the lift’s two outlines by your intended wall thickness, plus enough overlap for a sound glue joint with the lift above and below. The building-model-boats.com builder left at least 8 mm (5/16 in) of overlap. Leave the bottom lift (or the keel lifts) solid or only lightly hollowed. Keep extra wood where you will need it later, such as at the stem, the sternpost, shaft and rudder tube positions, and anywhere a mast steps.

Cutting the lifts

Cut the outside shape with a bandsaw, scroll saw, coping saw or jigsaw. Stay outside the line. You can always remove more wood, but you can’t put it back. A margin of about 1-6 mm is typical. One trick from the Model Shipwright tutorial is to go over the outside of the line with a broad felt-tip marker and keep the saw blade within the inked band.

For buttock lifts or doubled waterline lifts, pin the matching pair together (bamboo skewers or short dowels work well) and cut both at once so they match.

Before you peel off the templates, transfer the centreline and every station line to the edges of each lift with a square. On the bottom lift, carry the station lines and centreline across the underside as well. These lines are what you use to line up the stack, and later to check the shape as you carve.

Lining up the stack

With the templates removed, redraw the station lines and centreline on the faces of each lift and number them. Then dry-fit the stack, matching the station lines on the edges and the centrelines on each face.

Lifts slide around when glue goes on, so pin them in place first:

Line up two neighbouring lifts and clamp them.
Drill one hole through both in an area that will be hollowed out or that stays inside the hull, and fit a short dowel or piece of bamboo skewer.
Check the alignment again, then drill and pin a second hole.
Repeat up the stack. Make sure each dowel is shorter than the combined thickness of the two lifts it joins.

Dry-fit the whole stack and fix any problems before you open the glue.

Hollowing before glue-up

If the model is a working model, or you just want a lighter hull that is less likely to crack, cut out the inner shapes now. Drill a starter hole inside each inner line and cut it out with a scroll saw, coping saw or jigsaw. A Forstner bit in a drill press makes a neat starter hole.

Don’t hollow right to the line yet. You will need some extra wall thickness to carve the outside safely, and you can always remove more from the inside after the hull is shaped. Some builders leave pillars or a solid deck panel across the middle to make the hull stiffer to clamp and hold while carving, then cut them away later.

For a static model, hollowing is optional, but a hollow hull is lighter and moves less with seasonal changes in humidity.

Gluing and clamping

Glue choices:

PVA wood glue. Easy to use and easy to carve through. Standard interior PVA is fine for a static model. For a working model, a water-resistant PVA is a sensible choice, together with a good sealed finish.
Epoxy. Strong and waterproof, and good at filling small gaps. It is, however, much harder than the wood. The building-model-boats.com builder used marine epoxy and later said it was overkill, because the cured glue lines blunted their spokeshave, planes and chisels.
Avoid cyanoacrylate (CA) for laminating. It sets too fast to let you adjust the stack.

Spread a thin, even coat on each joint face, assemble the stack on its dowels, and clamp evenly from one end to the other. Use plenty of clamps. Gaps in the glue lines show up as cracks once the hull is shaped. Wipe away squeeze-out from the inside before it sets, where you won’t be able to reach it later. Leave the stack to cure fully before carving.

Carving and shaping the hull

Work from the outside in, in stages:

Rough off the steps. Use a spokeshave, block plane, chisels, rasps or a Surform to remove the corners of each step. Some builders use a sanding disc or flap disc on a power tool, but it removes wood very fast. Work in short bursts and check often.
Watch the glue lines. On a waterline hull, each glue line is a waterline. If you carve both sides evenly, those lines should stay level and matching side to side. A line that wanders or sits lower on one side shows where you are taking too much off.
Redraw the stations as you go. Pencil the station lines back on whenever sanding removes them.
Shape to the smaller waterline. When you reach the inner waterline of each step, stop and check with templates.

Section templates

Make a set of templates from the body plan, one for each station. Cut them from card or thin plywood as an outline of the hull section at each station, with the centreline and a reference height marked. Hold each template square to the hull at its station line, with its centreline on the hull’s centreline, and look for light showing between them. Light means a low spot, and contact in one place means a high spot. Take wood off only where the template touches early.

Finish with sanding blocks and progressively finer paper. A long, flexible sanding block helps keep the curves fair between stations. Sight along the hull under low, raking light to find any remaining bumps or hollows.

If you are hollowing, finish the inside once the outside is shaped. Gouges, a rotary tool with a sanding drum and curved scrapers all help. Check the wall thickness often with calipers or by holding the hull up to a bright light. Thinner walls show light more easily.

Sealing and finishing

How you finish the hull depends on how it will be used:

Static models. Seal the wood with a sanding sealer or thinned varnish, sand lightly, then prime and paint. Our guide to model ship finishes covers each stage. If you used contrasting woods for the lifts, a clear finish shows off the stripes, which makes an attractive display or half model.
Working models. Seal the inside as well as the outside, since water gets into any bare wood. Many builders sheath the outside in light glass cloth and epoxy for extra protection. Our guide to waterproofing a wooden model boat hull with epoxy and glass cloth covers that step.

If the deck will be planked, see using wooden decks on model ships. A carefully faired bread-and-butter hull also makes a good plug for taking a mould. See our article on model boat moulds for fibreglass and plastic hulls.

Common problems and how to avoid them

Lifts out of line. Usually caused by missing or faint station lines, or no locating pins. Square the lines down every edge and pin each pair before gluing.
Not enough wood to carve. The lift was cut to the smaller outline, or too close to the line. Always cut to the larger of the two waterlines and leave a margin.
Breaking through a hollowed wall. The inner line was too close to the outer shape. Allow extra wall thickness and do the final hollowing after the outside is carved. If you do break through, glue in a patch of the same wood and reshape.
Visible glue lines or gaps. From uneven clamping or too little glue. Clamp evenly, and fill small gaps before sealing.
A lopsided hull. Check symmetry with section templates on both sides of every station, and watch that the glue lines stay level.
Cracking later. Solid, thick hulls are more prone to it. Hollowing and sealing the whole hull, inside and out, reduces wood movement.