Hi Bruce,
When sending a surfboard, they bill you by "Cubing" which is volume as opposed to weight. Most freight companies work on an industry standard of Length x Width x Depth all in cm x 250. So for a surfboard I sent recently it was 200 x 55 x 8cm , therefore 2.0 x .55 x .08 = .088 x 250 = 22kg.
This gives you the weight charge they apply, even though the box was only about 6kg. It cost me around $30 to send the board 800km to a regional country town. I later was quoted $65 to send another surfboard to Sydney, same cubing in place.
It pays to shop around. Some companies wont even quote you unless you have an account. Because my freight requirements are small, I use a prepaid account which works out really cheap and I have no minimum spend or min freight per month, so long as my account stays in credit.
Good winds,