Filler

[Jim Fortnam]

I don't want to sound picky, but I regard using filler as a failure on my part somewhere along the production line. Epoxy is the filling material of choice these days for 1:1 work - and uses inert materials in the liquid 'glue' to produce something like a putty that is both adhesive and gap filling. It is an age old cabinetmakers recipe to mix the sawdust of the groundwork with glue to produce an 'invisible' repair, and a technique I have used many times on restoration work. I even keep a tin of fine ebony dust and another of a general purpose mahogany dust for the purpose.
The point is that on new work, you should aim for accuracy in the fit and run of planks - there are plenty of treatises on how to fit planks, and how to check that the frames (bulkheads) are aligned to avoid bumps and hollows. If you follow full size practice, it becomes easier, with correctly spaced frames, to ensure a good line, and if an undersized frame has to be discarded, why, it just makes you a bit more careful on the next, and adds to your store of 'experience'. Ditto if you dry fit a plank and make it undersize in width, or bodge the joint at stem or stern. Bear in mind that full size work was intended to be self correcting as you fit each plank, so even an unexpected stealer can be justified.

If you want to create a real 'model' then I always suggest a read of Harold Underhill's books. All the way from making built up frames as per original, to applying planks, and then fittings and rigging. Never been beaten in my humble opinion.

But back to the question, now I've done with some preaching.

I would avoid using any filler which is harder than the timber I am applying it to. It will be near impossible to abrade it back to a fair surface aligned with the run of the model. Then consider what appearance you need. If you intend to leave naked timber exposed then your only choice really would be to take a scalpel, cut out the mistake, and insert new timber in the fashion of a 'repair'. Ships were repaired all the time, sometimes whilst in remote places, beached and new timbers fashioned from whatever was to hand, or even, in extremis, patched up at sea - what a job that must have been.
A new plank, or two, even inserted to a weathered, painted hull, makes a conversation piece and could draw the eye away from some area you would rather the viewer didn't spend too much time on.
If the repair is going under paint, or in so many of these kits, into the false skin of dummy planks, then old fashioned linseed oil putty can be useful. Malleable, takes a good surface, dries slowly, retains a small measure of elasticity to move with the wood. Or you can produce your own filler from sawdust - use shellac if you want something quick drying, yet controllable, and reversible. Others have already gone into PVA glues as binders for sawdust. You can also use paint and plaster. Same colour paint as you are using of course, mix way more plaster than you think it can hold, and you get a filler which is inert, and tightly bound to the paint you are using. (useful round the house too)
And finally - the restorer's friend - pumice powder. Used for grain filling under French polish (shellac) it starts life as a grey dust, but becomes almost invisible when rubbed into a crack or split or badly made joint as a part of the polishing process. Use a shellac fad reserved for the task, and rub the pumice into the split. The polish on the fad will keep it there, and after the area has dried, you can remove any surplus left around the repair with French polish in the usual manner. Good for varnished hulls.

Jim

 

[Ted Robinson]

The use of fillers becomes a far less frequent necessity when one builds a solid hull model as I'm sure Roger can attest. Kits used to provide a solid hull blank, roughly shaped, which could be painted or, if one wanted to "show the planking" veneered with thin planking wood. However, the machinery automatically to carve hulls from solid wood is expensive and it's a lot less expensive and saves a lot of shipping and warehousing space if a kit can be packaged in a flat box with the "hull" reduced to some bulkheads and a bunch of wood strips. I suppose it was marketing hype, but some kit manufacturers promote their models as somehow "better" because the hull shape is defined by bending the planks on frames or bulkheads instead of by shaping a solid block of wood. They also suggest that POB or POF construction is "easier" than "carving a hull," which however counterintuitive it may seem to the uninitiated, is quite simply untrue if standard "tricks of the trade," such as the "bread and butter" or "lift method" are followed. In this respect, I find the old machine-carved solid model hull kits were far easier to build than the present-day POB and POF kits.

If a hull is to be painted, what is used to fair the surface doesn't much matter. There's lots of options on the market. I use standard fairing putty primarily due to its extremely fine grain, rapid hardening, and ease of sanding. My go-to is Interlux Surfacing Putty. It's solvent is acetone, so care is required to keep a good air-tight seal on the can, but it is easily reconstituted in the can by adding a small amount of acetone and letting it sit overnight and reach "equilibrium." It's a marine product and can be found at chandleries or online. It dries white.

This product is a bit pricy compared to drywall spackle which appears much the same, but it isn't. The chalk it's made of is very finely ground and so permits sanding with fine grit abrasives, e.g., 600 grit. A good finish on a miniature has to be a "miniature" finish. A thick coating build-up destroys the sharp scale definition that good models require. Therefore, the surface has to be perfectly smooth before the finish coating is applied in order to achieve a perfectly fair finish with a minimum of built-up coating material, be it opaque or clear. One shouldn't rely of multiple coats of thick finish coating sanded repeatedly to fair the surface. It also bears mentioning that sanding wood that has been sealed with thin, clear shellac down to 300 grit and finer is a lot easier if what is being sanded is the lightly shellacked wood and a proper fairing compound that is designed to be easily sanded.

https://www.jamestowndistributors.com/product/product-detail/4154

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For filling cracks and minor imperfections in wood that is to be finished bright, I use furniture finisher's wax filling crayons which are made by several manufacturers and widely available. I use Mohawk brand, for no reason other than their availability to me. They are wax crayons which are made in a variety of wood finish colors. These crayons can be purchased one at a time and in sets for a wider range of colors. The wax softens easily from the warmth of the user's fingers or, if preferred, another heat source can be used. Application is accomplished either by simply rubbing the softened wax into the crack and buffing off the excess or by actually melting the wax from the crayon with a flame (really messy, but good for larger cracks) or other heat source. Generally, I shave off a bit and roll it in a ball between my fingers until it is soft enough to suit the application. Any clear finish can be applied over this product.

I found a YouTube video that addressing filling cracks in furniture and covers the use of finisher's wax sticks in detail. A picture is worth a thousand words and a video twice that:

I have also used the well-known "sawdust in something sticky" method to good effect, although it can get messy and the last thing I need in my shop is more sawdust! I've mixed sawdust in clear shellac to good effect. When the shellac dries (quickly because it's solvent is denatured alcohol) it sands easily. Also, besides its quick evaporation time, using shellac as a binder for the sawdust avoids the risk of sanding before the inner core of the putty applied has completely cured. The temptation to feel the surface and decide it's cured enough to start sanding is always there, for myself at least. I've found sanding adhesives such as Titebond PVA to be problematic because they tend to get gummy when the friction from sanding warms them up. They then gum up the sandpaper, rendering it useless. This can be a real pain when using expensive abrasives on detail sanders and drums! When shellac is used as a binder, it's easily dissolved with denatured alcohol and wiped off if one wants to have another go at it for whatever reason.

As always, "your mileage m

ay vary." This is what works for me. If something else works for you, by all means, go for it!

I am intrigued by the filler putty but your tip of using Shellac mixed with sawdust seems genius. I will never use PVA again.
Thank you