Penny et al wrote:
Thanks, folks, for your info.
I am fascinated at the comment that the changing shape of the hull has little or no effect on overall drag, though, whereas scratches do. I assume it has to do with the disruption in the linear flow caused by the scratches? Yuri_k, do you know how great an impact on the drag the scratches made? i.e., would it be a noticeable difference? We have a very beat up old Scott Tripper Kevlar (used to be a rental, it's filling a gap until we figure out exactly what type of canoeing we'll be concentrating on). SHould I seriously look at the outside hull smoothness?
I wouldn't freak out too much about scratches on your boat. In principle scratches add turbulence so increase drag. In practice the effect isn't huge and as the article on the link says turbulence is hard to avoid. The effect may be 5%...I'm guessing... but it's not a night and day difference. Probably worthwhile if you race long distance. Another tech article points out that the first three feet of the boat is most important since that's the only part where you might avoid turbulence. Oil canning occurs mid-boat. Fish change their hull shape and there is research around flexible skins for submarines. I just spent a lot of time polishing up my oldest scratched up boat and I really can't tell if it helped but it made me feel better for giving it some love.
https://www.fsc.com.au/wp-content/uploa ... bottom.pdf