I have a question about the sweet spot: that length of optimum weaving area on the loom. How does one discover where that sweet spot is without, say, ruining an entire project? Is it different with different fibers? Different weave structures? My rough guess is that it has something to do with the angle of the reed and fell; does that mean that overhead and underslung beaters provide different sweet spots? Longer? Shorter?
–Kate Foreman Suko
Your email was forwarded to me as a good question for Ask Madelyn, since you probably are not the only person to wonder about it.
Ideally, the beater should hit the fell at a right angle to the warp, or pretty close. The overhead beater will give a slightly upward motion if the fell is too close to you; beaters hinged at the bottom will press downward on the cloth in that case. Conversely, the beater can't achieve acceleration without a little distance between the fell and the shafts.
The arc the beater swings through is shallow or sharp depending on the length of the side supports the beater is attached to. The longer the supports, the greater the area of arc in which the beater is near perpendicular. So for most overhead beaters, the sweet spot is a little larger. (Scandinavian looms even have positions through which you can move the beater as you weave, increasing the distance you can weave before advancing the warp. I'm happier just advancing the dang warp—how bad can that be!)
After I wrote the above, I went from loom to loom in my school to formulate some words about exactly where the sweet spot is and got a surprise. What I discovered is that the sweet spot is more forward of perpendicular than I would have guessed. That is, if you wove where the beater is perpendicular to the cloth on both types of looms, you would be weaving so close to the shafts that the shed would be constrained and there wouldn't be room to position the weft at a proper angle for most structures.
So, for me, on looms with beaters hinged at the bottom, I weave for about two inches in an area starting about two inches from the front beam. On my large Scandinavian looms, I weave for about three inches in an area that starts about three inches from the front beam.
The key is this: How you place the weft and move the beater should be comfortable for you. Most important of all is to advance the warp often so you are always hitting the warp with the beater at the same angle. That way, when you remove the cloth from the loom, you won't see streaks in the weft where you advanced the warp and changed the angle.