I think a lot of people have the notion that an Erhu bow has to be tighten till the hairs are taut, close to that of a violin bow. Even my father who's been selling Erhus for the longest time used to setup Erhus with taut bows.
I personally feel that the tension in Erhu bows should be loose to the extent that the bow hairs form an angle with the strings when it is resting against them. The bamboo should be resting on the sloping side of the resonator. It should look something like this:
A bow that is too taut will look something like this when the bow rests on the resonator:
A Erhu bow that is slack will give a smoother and more full bodied tone as compared to the tone produced by a taut bow, which I would describe as 'constipated'.
Try it and you should find your tone improved, albeit its not as easy to handle as before for some.
