Block Planes
As you apply finer and finer grits of sandpaper and screens to the finish of your board, you’ll notice that your stringer ends up higher than the foam. I’m sure most of you are aware of this, but for those who aren’t this happens because the foam (being softer than wood) shapes away more quickly. This leaves behind a raised stringer. Neglecting to plane the stringer flush to the foam will leave a high spot that the sander could clip and sand through later, which could potentially split your boards lamination, weakening the board.
I have a couple of tips to help you regarding both Polyurethane and EPS shaping, but I think the most obvious answer (just to get it out of the way early) is to keep your knives sharpened and to always have a wet stone and a bit of water in your shaping room in case you notice your blade dulling.
Furthermore, you don’t want to handle a block plane too heavily, and you shouldn’t have to if you set you depth correctly. It is important to have a variable depth block. You should reset your plane depth after every sandpaper or screen pass. The stringer heights will decline as you move on to lighter grits.
It is proper to hold the plane at an angle to the cutting surface (as you would, for example, when taking planer passes off the blank). This decreases the chance that the knife’s corners will score the foam.
Heavily scored foam around the stringer should be avoided at all costs. This scoring is colloquially referred to as “railroad tracks”. These scratches and divots can be on the same level or worse than say those from a 36 grit piece of sandpaper. They can lead to an endless loop of sanding and block planning if you don’t get them under control, so keep your passes light and do small tests of your cutting depth before moving on to the entire stringer.
If you’re shaping EPS, I wouldn’t recommend using a block plane. EPS is easy to score or divot and railroad tracks on EPS blanks can be difficult to remedy. I prefer using a spoke shave with a curved blade along the entire length of the stringer on an EPS blank. A light hand is still important here! There was a time when I was finishing a lot of EPS boards for my dad and his spoke shave allowed me to hit the stringer in just the right way that I was able to cut it a hair deeper than the foam without touching the foam at all. A quick pass with a fine screen was just enough then to bring the foam back down flush to the wood.
I have one more little secret: I mentioned above that my spoke shave blade is curved. Well, so is my block plane blade. They are curved because my wet stone has a concave surface, the result of decades of use by my dad. This curve is useful as it allows me to focus more on just the stringer as I touched upon above.
Even the best of us score the foam occasionally, but we should always be aiming for a result that can be tinted in lamination. So, keep sharpening and keep practicing and feel free to DM me on Instagram or via email if you have any questions!
Happy Shaping!
Bruce Jones, shaping a surfboard with a Stanley block plane.
A railroad track free stringer should be possible for all of you with a sharp tool and the correct approach.