Recommendation for study books or other material requested

Hello all,

I would like to acquire some more insight into the drag that is to be expected at various speeds with rowed (Cornish) Pilot Gigs and whaleboats.
When I studied mechanical engineering (some 25 years ago) I was taught the absolute basics of hydrodynamic drag in a introductory course of maritime engineering, but that obviously falls short in enabling me to get to the answers I'm seeking.

Just recently the question of the influence of the type of paint used and the smoothness of the finish was added.

Anybody any suggestions? I would appreciate it.

Jaap vd Heide

 

Well,

I went by the library today and took out copies of "Principles of Yacht Design" by L. Larsson and "Resistance and propulsion of ships" by Sv.Aa. Harvald. Those should get me somewhat further. I'ld still value advise though. Especially when it comes to the influence of lapstrake / clinker construction on frictional resistance.

Regards

 

There is no method of accurately predicting drag of complex shapes. The most accurate methods modifies the analysis with adjustments based on similar shaped objects. There are text books on the theory of drag prediction, mostly geared toward aircraft (the same principles apply to hulls) but the NA text books will give you comparisons of actual boat hulls.

It always struck me that lapstrake/clinker construction would be very draggy compared to a similar shape smooth hull, but people say there is not much difference. As far as surface finish, that is entire dependent on the Reynold's number (a kind of turbulence score). You are typically way beyond transition in even a small boat for a rough surface to be helpful, so a smooth surface is usually best. There are some theories on a mat finish being better to reduce surface tension, but I do not see how this can make much of a difference. At the air/water interface there would be a very small difference, but this is such a small part of the whole I do not see how this would be measurable.

Good luck in your search.