|
|
|
|
Fiberglass vs plastic
On 30-May-2004, (William R. Watt) wrote:
Skin friction does not increase monotonically with length. It does
increase monotonically with the product of surface smoothness and wetted
surface area
If surface smoothness is constant, then skin friction increases monotonically
with wetted surface area. Why would you assume that surface smoothness is
variable among kayaks? For a constant displacement, wetted surface area
changes directly with length. Why complicate things?
Winters' website
His website has been gone for quite a while. I have no way to verify your
interpretations of what he wrote there.
I would like to see data specific to sea
kayaks. the wind and wave resistance data is from a book on sea kayak
cruising. it also appears to me to be pretty general.
In his book, he specifically states that there is no significant difference
in the behavior of canoe and kayak hulls. They come in the same range of
lengths and vary only in width. Most of the other parameters, such as block
and prismatic coefficients are in the same ballpark as well.
Most data is from smooth water conditions. There isn't much data on kayaks
in cruising conditions - that gets really complicated from the standpoint of
analysis, since kayaks operate in rough conditions where simple analysis
breaks down. However, it seems like most decent smooth water designs will
perform adequately in rough conditions, while a poor design in smooth
water is poor in rough. Most kayaks that perform well in smooth water but not
in rough suffer from other problems, such as weathercocking and tracking, not
so much from resistance to forward motion.
Mike
|