Benjamin MendlowitzBAGATELLE, a 1914 Herreshoff Buzzards Bay 25, was rebuilt by the author’s shop (see WoodenBoat No. 148). The hull received a treatment similar to the one described in this article.
The use of epoxy on a carvel-planked hull is a contentious issue. Well-meaning owners often slather their hulls and/or interiors with epoxy, believing that such treatment — often called “encapsulation” — will extend the life of their boat when, in fact, in some cases it may actually hasten its demise. However, our shop has developed a method of fairing hulls that relies heavily on the use of thickened epoxy, and we believe this method, used on single-planked cedar hulls, yields both a superior finish and the incidental benefit of stabilizing the planking.
The subject of fairing is itself a contentious issue. Not only do techniques vary, but so do philosophies. Although it is conjecture on our part, we believe that the degree of finish and paint quality expected and produced today are significantly higher than when many classic (generally, pre-World War II) yachts were first built. Spectacularly finished yachts are not a modern invention, but the best were typically built with stable planking such as teak or mahogany, or were double planked. Moorings and docks today are filled with the smooth shine of modern boats, and the owners of restoration projects, understandably, sometimes desire the same level of finish. Achieving and retaining a smooth and stable surface on a single-planked cedar hull, however, is a challenge and a commitment.
The first step in fairing new planking is to break out the planes. In the illustration, a new plank is being faired into the old, using the old as a guide.
Fairing the Rough Hull
The ultimate goal of fairing is to reach a point where a boat-length batten placed against the hull will touch everywhere, without showing any unfairness. In reality, the project’s budget and schedule, and the worker’s sanity, will limit the result to one that is pleasing to a critical eye.
We start the process conventionally with planes of varying shape and length. Backing-out planes are used in the hollow areas of the garboards, broadstrakes, and the bow near the waterline. Bench planes and block planes are used on the rest of the hull.
In a restoration job, we are often fairing new planking into old, using old as our guide. This stage of the process requires great care to not fair off surrounding planking to an original neighboring plank that’s too thin. It is not uncommon for planks to lose thickness due to the annual sanding of apparent hard spots — especially in the topsides. These chronic hard spots are usually due to failed fastenings and/or cracked or broken frames, and result in a lifted plank edge.
When several frames in a row are broken, a hard spot often results (A). Several years of sanding and smoothing this “corner” will reduce the thickness along the edges of the planks that adjoin here; when the boat’s frames are sistered or replaced, a hollow spot will result (B). This hollow may be either filled in with thickened epoxy or, if it is greater than 1/8″, be built up with a laminate of wood (C).
The surface of the proud portion of the plank then gets sanded fair with its neighbor, and when such a plank is eventually pulled in tight to a new frame, the result is a plank that is too thin. Rather than using the too-thin plank as a reference, and overplaning and over-sanding the surrounding area, we are careful to build up the thin plank. We do this either with fairing compound or, if the lost plank thickness exceeds ¼″, with a thin piece of plank stock glued to the offending plank to increase its thickness.
Initial Longboarding
When the planing is complete (determined by a check with a short-say, 24″-batten), it’s time for a longboard session. With the exception of sanding bottom paint, there is probably not a more dreaded boatbuilding task than longboarding. The hardest part is not the physical exertion — which is significant, especially with the big boards — but rather is in paying attention. As with any tool, you can move the job backwards unless your head is there.
As with any sanding, it is important that the surface of the hull planking is homogeneous, or surface irregularities will develop. Density varies among different wood species, such as between hardwood sheerstrakes and softwood planking, but it can also vary within the same species. It can even vary between the spring wood and late wood in the same piece of wood. This is obvious to anyone who has tried to sand flat-sawn cedar or cypress. To overcome these density issues, we apply an epoxy-based fairing putty.
Epoxy “Trowel Cement”
What follows may seem distasteful to some, but the approach has worked well for us, and has produced the desired results (oohs and ahhs). It is not “traditional,” but it accomplishes what yesteryear’s trowel cement and thick, oil-based primers don’t do very well. The traditional fillers and fairing compounds are weak, brittle, and not very adhesive — and they absorb moisture and are oh-so-painfully slow to dry. Modern or old, epoxy or turpentine, it’s all just cosmetic anyway.
For topsides, our fairing material of choice, reverently referred to as “smoodge” (can be used as either a noun or a verb), is West System 410 Microlight mixed into West System 105 epoxy resin and 206 slow hardener. We use the slow hardener due to the large volumes that must be mixed (overheated or “smoked” smoodge is not a pretty sight). Before applying the smoodge, we treat the hull with a priming coat of clear, unthickened epoxy, which is rolled on and then squeegeed off — but is still tacky when the smoodge is applied. This coat of epoxy prevents the wood from soaking up the resin in the smoodge and potentially leaving it too dry and therefore brittle. Once mixed, the smoodge is spread out on pallets to slow the rate of cure, and applied over the entire topsides with notched trowels.
Photo by Mcclave, Philbrick, and Giblin BoatbuildingThe first layer of thickened epoxy – “smoodge” in the author’s lexicon – is applied with a notched trowel. The resulting surface is shown in the photo at the right. Only the visible lows on the bottom are smoodged.
We apply the smoodge vertically, starting at the sheer and pulling down smoothly in a continuous motion toward the waterline. Timing this first batch helps later in the fairing process. Our trowels have been ground to leave a ribbon of material that’s wider than it is deep. This allows more surface area for bonding, and prevents shearing off the ribbons while fairing. A notch that’s ⅛″ deep and ¼″ wide seems to leave plenty of material (we could probably get away with even less depth). The theory is to have enough depth to fill the lowest low on the boat while having just a trace of smoodge over the highest high.
The smoodge should apply smoothly without “balling” or rolling up on itself — both occurrences indicating too thick a mix. On the other hand, if the mix is too thin, it sags and is also harder to sand.
We do not coat the entire bottom of the hull, buL only smoodge the visible lows after planing and longboarding. Our filler mix here is either West System 407 microballoon/silica blend or MAS two-parl epoxy fairing compound. Both of these products seem less prone to moisture absorption than the 410 Microlight underwater. As we tend to fill only low areas underwater, we dispense with the notched trowel technique and apply compound with a large (4″-6″ wide) smooth knife. We also tend to cease fairing the bottom at this stage, and sand the surface smooth with 220-grit paper on a 6″ random-orbit sander. This is followed by a coat of primer. We like to use red lead for this, but are exploring alternatives such as iron oxide primer due to the recently limited choices in red-lead availability — as well as health concerns.
Fairing the Epoxied Surface
After the topsides are smoodged, we shut the doors and discourage visitors because what happens next is ugly, very ugly. Any big ridges or projections are first blockplaned off. Then the longboards are manned, accompanied by blue chalk and battens. We have a quiver of longboards utilizing 3M Hookit sanding sheets on 3M’s 4 ½″ x 30″ boards; we also use sticky-back sheets on Norton’s 2 ¾″ x 16 ½″ boards. We have a variety of longboard “bendabilities”; the board selected depends on the shape of the hull that’s being faired, and the area being worked. The 3M boards come either stiff or flexible, and we simply cut a chunk out of the Norton ones to make them more bendy.
During the planing process, a batten will reveal high spots in the planking. This batten may be used throughout the fairing job. Chalk is applied to it here to mark the high spots.
Before making dust, we apply blue chalk to a flexible wooden batten and rub the area to be worked diagonally to the plank seams, switching the diagonals 90 degrees to achieve a series of blue chalk “X” marks on the hull; the hope is that these will highlight high spots. It is important to note that longer battens make for a more precise job, but they are also more difficult to use.
For the session when we are really “working it,” we use battens that are 36″ to 48″ long. We then don face-shield style respirators, which we always use when working with epoxy, as well as for painting and heavy wood-milling operations. We start with 60-grit paper on the big boards. This cuts the Microlight well, but allows us to stay in control. We concentrate on sanding off the highs and tread lightly on the lows, proceeding until the ribbons of Microlight begin to wear away at the highs but before “burning through” to bare wood-which would create a density discrepancy between the wood and the smoodge.
Photo by Mcclave, Philbrick, and Giblin BoatbuildingAfter the first coat of smoodge is applied, the obvious high spots are sanded or planed. The chalked batten is employed once again at this stage. This sanding stops when the smoodge begins to wear away at the high spots. Then, a second coat of smoodge fills in the “ribbons” and, when this is completely cured, it is longboarded and sanded to a fine finish. The resulting surface should be of uniform density, and ready for paint; another round of thickened epoxy and sanding may be required to get the hull to this stage.
We now mix up more smoodge, this time untinted, and apply it with 6″ to 8″ knives, filling the gaps between ribbons but only barely covering them. We then switch to 80-grit paper and get more serious with the battens. In theory, if the batten leaves chalk over the entire sanded surface, you are done. But this doesn’t ever really happen in practice; you have to decide for yourself when the gaps under the batten are sufficiently imperceptible — or, when enough is enough. If you are close to burning through a high spot and the batten and the feel of your hand reveals an unacceptable nearby low, the low area is circled with red chalk for additional smoodge to be applied, and the process is repeated for this area or the hull.
On a 32′ moderate-displacement hull, one person might put in two full days (or four hair days, depending on stamina) on this phase, with an additional day to refill and fair off any unacceptable lows.
Applying Barrier Coat Paint
Theoretically, the boat is nearly fair at this point, but the surface is rough, scratchy, and full of pockmarks. We now switch to an epoxy-based high-build moisture-barrier paint. This acts to seal the Microlight and also to slow clown the wetting/drying cycles of the planking. These paints adhere well, and arc nexible enough to move with the planking and allow the soft seam compound to push out from between them when the planks swell. Multiple coats can be applied without sanding, and the stuff cures in a reasonable amount of time. Generally, we can sand on Monday after applying the coats on a Friday.
Please note that we do not allow any of this hard material to get into the seams, in order to avoid compressive set of the planks during the first swelling/drying cycle. We avoid this by making sure all of the seams have soft seam compound in them before any smoodge is applied. We use lnterlux Barrier Coat #404/414; we call it “stink paint” because its thinner/reducer truly makes a powerful stink. We roll it on, then tip it with a foam brush, one coat over the other, before the previous one has fully cured (read the label). We might roll on as many as five or six coats, after which we longboard yet again!
Some might find it surprising that our seam compounds of choice are of the “old-timey” sort. We use Interlux No. 31 white seam compound for the topsides and, believe it or not, plastic roofing cement in the bottom seams if the boat is to be stored ashore in winter. We intend that only enough compound will remain in the seams after the first swelling to fiII them, and we hope that no more will be added in subsequent years. We assign no structural value to seam compound, and at best hope that it will slow down the leaking while the boat swells up. For boats that will stay in the water or be kept damp, we use Boatlife polysulfide in the bottom seams.
The barrier-coat paint is hard to sand, so we use 80-grit paper with the chalk batten. Because the hull is already quite fair, this operation typically goes faster than the earlier smoodge fairing; we spend perhaps one day on the topsides. We follow this session with two to three more coats of stink paint to fill the scratches, then use the D.A. (dual action) sander-equipped with vacuum dust extraction-with 220-grit paper prior to the first coat of finish paint. Phew!
For the finish coats, most any topside paint should work well over the epoxy primer, but to benefit from the flexibility of Lhc “underlayment,” we use a single-part brushable polyurethane. This is applied on a cool day so it levels, and is rolled on and tipped out vertically. Vertical brushing leaves a minimum-length wet edge, and really cuts back on sagging.
After launching, the planking will swell and tend to push out the seam compound, which will show along the topside seams. We try to minimize this by having the smallest seams possible, and, therefore, a minimal amount of putty. We also try to raise the moisture content of the planking before all of this effort. (To do this, we might place the boat on a sheet of plastic, and drape additional plastic sheets from the toerails to the floor. The resulting tent can then be periodically sprayed with water. Or, we might simply launch the boat for a period of time, and then haul it to commence the finish work.)
Some additional longboarding the following season, after the planking has “settled down,” is not uncommon, but rarely does smoodge have to be added again. Instead, a high-build surface primer will be used prior to the second season, to fill the scratches left by the additional longboarding. Both Brightside Primer and Interlux Multithane primer seem to work well.
So there it is. I fully expect to raise the ire of those who think this modern stuff has no place in a classic boat. Our techniques and the use of these products came from a desire to achieve a showboat finish in a reasonable amount of time — and a finish that would last long enough to justify the effort. These materials seem to do this, and we are seeing paint jobs in much better condition in springtime after a winter haulout. Some lucky owners have even squeaked out two or more seasons with only minor touchups.
Andy Giblin is a partner at Mcclave, Philbrick, and Giblin Boatbuilding in Mystic, Connecticut. The company is now known as MP&G. He lives in Noank, Connecticut, with his wife and daughter.