Smooth curve hulls

I was looking around for a project comparing different hull types and was wondering if there was any specific advantage of having a smooth curve hull vs a chine one?

 

Simple, perhaps too simple, answer is round bottom hulls generally have lower resistance at slow speed compared to similar size and proportion V-bottom hulls but are not good at planing speeds.

 

It's becoming a bit convoluted in recent design efforts, with round bilge hulls and a chine to help promote flow separation - the best of both worlds.

 

Best of both worlds - assuming the designer knows where separation is desirable and where it should be avoided for the intended speeds, heel, displacement, etc. Or just add a chine because the fast boats have them.

 

Well David, we do need to assume some testing and experience comes to play when selecting the shapes that might be employed. I do think some production craft have had their normally round bilge hulls cut, to accommodate a chine revision, just to make them seem "up with the trends", but I do think for the most part, those looking for the last little bit of an edge in racing, are performing the studies and testing necessary to make educated decisions.

 

Frequently faster rounded chine hulls tend to over bank in turns. I almost got pitched out of such a boat that was a tiller steered OB. Some boats don't bank at all. Boats faster than hull speed will be effected (turning and banking wise) by the chine design. The beam-wise outboard flow of water coming out from under the bottom aft will tend to pull the inbd chine down. The higher the bow and angle of attack the more pronounced the "pull down". And not in a turn both chines will pull the whole boat down to some extent. For this reason longer and narrower boats favor soft chines. ....... IMO

 

Is it a powerboat, sailboat, rowboat, high speed, displacement speed, etc?

 

I know from sea kayak construction, and small dingy sailors, with careful design there is not a lot of performance difference between a multi-chine hull and a smooth rounded bilge hull. a muti-chine hull has slightly more wet area, so it should be slightly slower. but practical experiance shows almost identical perforce for otherwise same hull shape.

both cost about the same in materials, and can also be similar in weight, the big advantage is that multi-chine hull is faster (less labor intensive) to build.