View Full Version : Tumblehome - ship design pearls

12-14-2011, 22:48
Tumblehome was common on wooden warships for centuries.

In the era of oared combat ships it was quite common, placing the oar ports as far abeam as possible. This also made it more difficult to board by force, as the ships would come to contact at their widest points, with the decks some distance apart. The narrowing of the deck above this point made the boat more stable by lowering the weight above the waterline, which is one of the reasons it remained common during the age of cannon-armed ships. In addition, the sloping sides of a tumblehome ship increased the effective thickness of the hull versus flat horizontal trajectory gunfire (a straight line through faced more material to penetrate) and also increased the likelihood of a shell striking the hull being deflected- much the same reasons that later tank armor was sloped. (From W)


David Manley
12-14-2011, 23:45
Tumblehome was something of a necessity in ships of the line and (to a slightly lesser degree) in frigates. As a design feature for naval architects it has some "unhelpful" features as well, in particular regarding resistance to underwater damage and flooding. This was not really an issue during the age of sail, but where its use was carried forward or, perhaps more accurately, revised in some pre-dreadnought designs of the late 1800s it produced ships whose ability to resist flooding and to retain stability when damaged was significantly compromised over their more wall-sided contemporaries. The issue being that the waterplane area (a key component in ship stability) reduces as the ship settles deeper in the water. The Russian Borodino class being a particular case in point. Its most recent reincarnation is in the US DDG-1000 class of "destroyers" (although these ships are as much "destroyers" as the RN's "Invincible" class were "through deck cruisers" - and the reason for the choice of name was no doubt similar between the two :) )

07-12-2012, 00:07
Just reading the first issue of "Modern War" by Decision Games and an article on future US naval design mentions a class of ship that incorporate tumblehome to reduce the radar signature significantly and to aide stability. Interesting how some things come full circle. I cant help but wonder that in reducing radar signature they may increase detectability of a vessel by submarine or sea bed detectors. I'm sure someone (David) will know more on this!

David Manley
07-12-2012, 06:56
I do, but I can't say anything on this (other than "an aid to stability"? - actually quite the reverse!!)

07-12-2012, 07:12
Ah well you cant believe everything you read!