Bows in ancient India

[George Hart]

In translating Akananuru 175 (this is one of the Tamil anthologies), I  
have the following excerpt:

My lover crossed the hot wilderness where cruel men

never miss as they draw their strong, swift bows

with their heavy strings, and, every time they shoot,

their sharp-tipped, whistling arrows fly, taking the lives

of strangers walking on the paths there and vultures

summoning their flocks feast on their flesh.

I am wondering about "heavy strings," which in Tamil is viinku  
viLimpu.  The first word means "enlarged," "swollen," and the second  
means "edge," "border," "eyelid" (which leads the commentators to  
interpret it as "edge of the upper arm").  Other occurrences, however,  
make it clear that viLimpu refers to the string or a part of the  
string.  I am wondering whether anyone on this list has dealt with  
bows in Sanskrit sources and whether the strings of bows are mentioned  
as having some special feature.  I think viLimpu might possibly refer  
to the part of the string that comes in contact with the arrow and  
that might have been thicker than the rest of the string.  I recall  
that when I would shoot a bow as a child, that part was often thicker,  
as it could get worn down more easily than the rest of the string.   
George Hart