In the past I have explored a number of different Hearthboard Variations and was pondering the prospect of experimenting with a new approach using a saw instead of a knife to make a hearthboard.
Inspired by the Swedish Log Candle I decided to make a similar cross cut approach thinking that the char produced by the spindle combined with open saw cuts for air might be sufficient to create an ember.
I began using a Western cedar board and made a perpendicular cut across the width followed by two adjacent cuts at 45 degrees to the right and left. Each cut was halfway deep into the wood. I made a burn-in with the spindle at the center of the adjoining cuts and continued the bowing process.
This first configuration was unsuccessful so I decided that I needed to break out one of the triangular spaces between the cuts to allow for more air access while providing a place to catch some char. Evidently that wasn’t quite enough but was headed in the right direction, so I decided to cut that triangular space all the way through the side of the board thus creating a conventional notch that enabled a successful creation of a coal.
It is helpful to slant the spindle tip slightly away from the notch to counter any slippage out. I made sure to have a sufficient amount of char accumulated in the notch with smoke emerging from it before stopping the bow.
The Western cedar that I used is fast to heat but also fast to cool so when I stopped drilling I lifted the spindle only slightly upward within the hearthoard and held it close by while letting the char sit quite awhile to build heat before fanning the coal.
This project was a successful proof-of-concept that shows the possible advantage to using the cross cut method when your only prep tool is a saw that allows you to construct a working hearthboard. Give it a try and see how it works for you.