Recently there has been discussion about the suitability of different
materials in the construction of organ pipes, including cardboard.
In the book, "The Fairground Organ", by Eric V. Cockayne, there is
an appendix which details the construction of pipes from Bristol board,
or poster board as we know it.  Unfortunately this book is out of
print, but you might be able to locate a copy in the local library.

Another book which discusses making paper pipes is "Organ Building
for Amateurs", which was originally published in 1887, but is still
interesting reading.  That book is available from The Organ Literature
Foundation, 45 Norfold Rd., Braintree MA 02184-5918.  I checked
amazon.com and they also have that book.

Howard Wyman