Fairing is the step between assembling a hull frame and planking it. It’s not exciting work, but it does more than anything else to decide whether your planking goes on smoothly. A well-faired frame lets planks lie flat with even contact at every bulkhead. A poorly faired one causes lumps, gaps, and planks that won’t sit down.
What fairing means and why it matters
When bulkheads are cut from the plan, their edges are square to their faces. But the hull surface passes each bulkhead at an angle, especially toward the bow and stern, where the hull narrows. A plank laid on a square edge touches only one corner of it.
Fairing means bevelling each bulkhead edge to match the angle the hull surface makes as it passes. Done well, a flexible batten or plank laid across the frame touches every bulkhead along its full edge thickness, and runs in a smooth curve without bumps or flat spots.
Before you fair: check the frame
Fairing can’t fix a frame that’s out of alignment. Before sanding anything, check:
- The keel is straight. Sight along it from both ends. A bowed false keel makes a bent hull.
- The bulkheads are square to the keel in both directions, viewed from above and from the side.
- The bulkheads are centred. Measure from the keel to each side at the sheer or the deck edge; the two sides should match.
- The bulkheads are fully seated in their slots and at the right height. Check the tops against the deck line on the plan.
- The glue has fully cured.
Our overview of making a model boat hull covers setting up a frame square and on the centreline.
Tools for fairing
- Sanding blocks of several lengths. Long blocks bridge several bulkheads and find the average line; short ones reach into tight areas.
- Abrasive paper in a medium grade for removing material and a finer grade for finishing.
- A flexible batten: a strip of planking wood, ideally the same thickness as your planks.
- A soft pencil or marker.
- Strip wood and glue for shimming.
- A hobby knife, small plane or file for removing larger amounts of material, especially on filler blocks.
Step-by-step fairing
1. Stiffen the frame
Bulkheads and the false keel can flex or snap during sanding, especially near the ends. Before fairing:
- Fit the false deck if your kit provides one.
- Glue short pieces of strip or balsa between bulkheads, near the sheer and where they meet the keel, to brace them.
- Support the hull in a cradle or a padded vice so you aren’t pressing against unsupported bulkheads.
2. Fit filler blocks at bow and stern
Many kits, and most builders, add filler blocks between the first two or three bulkheads at the bow and the last few at the stern. These give planks continuous support where the curves are tightest. Glue them in oversize, then carve and sand them down with the bulkheads, blending them into the curve.
3. Mark the bevels
Lay a batten across the frame at several heights along the hull. Where it touches a bulkhead edge only at one corner, there’s a bevel to cut. Some builders run a pencil line along each bulkhead edge first. As you sand, you remove the line, and any pencil left on the edge shows where the batten isn’t yet in contact.
Around midships, the hull runs nearly parallel to the keel, so little or no bevel may be needed. The bevel increases toward the bow and stern.
4. Sand with a long block and check with a batten
- Sand diagonally across several bulkheads at once with a long block, following the line planks will take.
- Work a little at a time on each side, alternating port and starboard so the hull stays symmetrical.
- Lay the batten across the frame after every few strokes. It should touch each bulkhead along the full edge thickness and run without kinks.
- Check from several directions: along the hull, diagonally, and near the keel and sheer.
Be careful not to remove too much at the widest point of each bulkhead. Sanding below the line changes the shape of the hull.
5. Shim low bulkheads
If a bulkhead sits below its neighbours, so the batten bridges it without touching, don’t sand the others down to match. Glue a strip of wood or card to its edge, let it dry, then sand the shim fair with the rest.
6. Fair the rabbet and the stern
- Near the keel, the bevels must lead into the rabbet so the garboard plank seats properly.
- At the stern, check the transom, counter or sternpost area carefully. It often has a complex shape and is easy to over-sand.
- At the bow, make sure the planks will meet the stem cleanly with no step.
How to know you’re finished
Your frame is faired when:
- A batten touches every bulkhead along its full edge thickness, wherever you lay it.
- The batten follows a smooth curve with no kinks or flats, viewed from the side, from above and along the hull.
- Port and starboard sides look the same when you sight along the hull from the bow and from the stern.
- The bow and stern filler blocks blend into the bulkheads without a step.
Then move on to planking with our guide to planking a wooden model ship or yacht hull. If you’re building a framed model rather than a bulkhead model, the same method applies to the frames. See plank-on-bulkhead vs plank-on-frame for how the two differ.
Common mistakes
- Sanding with a short block. It follows the bulkhead and doesn’t reveal high and low spots.
- Over-sanding midships. Little bevel is usually needed there.
- Fairing one side completely before the other. This often makes the hull asymmetrical.
- Ignoring a low bulkhead. Shim it; don’t sand everything else down.
- Not supporting the frame. Bulkheads break, and the false keel can be bent.
- Skipping the batten check. Eyeballing alone misses small errors that show up as uneven planking.
The same fairing approach also applies to the moulds or shadows used for clinker-built model boats and strip-planked hulls.