Dad, what's 'tumble home' for?

[Tanbark Spanker]

Sometimes it makes a boat look hogged.

[Paul Pless]

Lots and lots of reasons, anything from avoiding taxes, to shifting deckweights toward the centerline (think cannons on an upper gundeck).

Use the search thingy, there's been many threads on tumblehome through the years.

[Hwyl]

ory is that it's a measurement beater, where either for racing or cargo rules, the beam is measured at the deck.

Another theory is that it's better for going alongside.

Another theory is that its better looking.

I think it's fast

[Tanbark Spanker]

Makes perfect sense to me.

[Christopher Locke]

Can also roll further to leeward without burying the decks. Also helps ultimate stability (degree to which you can heel and still ultimately recover) ("a weeble wobbles but doesn't fall over").

Chris

[johngsandusky]

If it's on a fishing boat it doesn't snag lines or nets like angled edges.

[Tanbark Spanker]

Ultimate stability is indeed important.

[P.I. Stazzer-Newt]

Its a finger saver in a canoe.

[Spokaloo]

Stiffening qualities of a curved panel and reducing scantlings to save weight?

E

[seedtick]

http://www.imagestation.com/picture/sraid217/pe05f6e51a30d730ff7f62671dd8affe2/ec5d77d8.jpg

[JimConlin]

If you have to ask, you have no soul.

http://www.westsystem.com/ewmag/22/images/Babyface-Nelson.jpg

[Paul Pless]

Jim, that's not playing fair!:eek:

[johnw]

Seems to have started with the Dutch Flute, a cargo vessel that saved a lot on habor fees by reducing the measured beam for purposes of calculating tonnage. On some boats it was combined with an eliptical transom so that the mainsheet wouldn't catch on the corners of the transom. There were some very ugly IOR boats built with high freeboard and lots of tumble home for rating reasons but they didn't win, so people stopped designing them, and eventually the IOR blessedly died. Some powerboats had rolled topsides for aerodymanmic purposes. I'm not convinced it's for seakeeping, because it narrows the beam when the boat is heeled. I can see where moving the guns inboard would help with stability until the vessel heeled enough to move their center of gravity farther to leaward then the center of bouancy, but then, you've got guns on both sides, so wouldn't they counterbalance?

[Lucky Luke]

Also helps ultimate stability
Chris
Wrong!:p

[Lucky Luke]

Its a finger saver in a canoe.
Right!;)

[Lucky Luke]

but then, you've got guns on both sides, so wouldn't they counterbalance?
They do counterbalalnce....statically, but not dynamically...and that counts!

[Gary Bergman]

Well, lessseee...I've got plenty 'o tumble home, kinda sweet, and plenty 'o cannon', 'tho I miss the connection. When things are dicey to the beam, and we are making a long run (a day or two),we sometimes move the leeward battery to windard, kinda the 'high side of the boat' mentality, but if we're planning on a long, rough run, we'll sometimes put all tubes below deck, as with early privateers. Toss into the mix that sometimes, I'll just run two to the centerline, and secure them...But what's alla this have to do with tumblehome???? I kinda like how it keeps my scuppers just that much farther from being 'under'....

[Donn]

There are two connections between gunnery and tumblehome.

One, the nature of the hull cuts through waves, rather than riding over them. This provides a more stable platform for guns.

Two, the weight of the guns is always closer to centerline.

http://www.paintedships.com/images/hms-victory-closeup3.jpg

This photo of HMS Victory shows clearly how much further inboard the guns are as they rise above the waterline on the higher gun decks.

[outofthenorm]

According to Fincham in "History of Naval Architecture, 1851" the idea that moving the guns inboard improved stability was right, but not for the reasons commonly cited. The truth was that the narrowing structure was lighter overall than the wider structure (lighter beams, planking, decking) and lighter guns were mounted there (carronades rather than long guns, 6-12 pounders rather than 24 or heavier.) Net result - improved stability through reduction of weight in the superstructure.

In ships like the Victory, tumblehome had another benefit - which is likely why it was kept until the advent of steam - when two ships came aboard one another in a fight, the hulls could collide but channels, rigging, gunport lids and guns had a better chance of surviving. You can see that from Donn's post. French and Spanish doctrine at the time of Trafalgar was to aim high, disable the opponent's ability to manoever, then "boarding party away! They wanted to turn the sea fight into a land fight. British doctrine was to stand at arm's length and pound 'em. Extreme tumblehome like the Victory's helped them do that.

David MacGregor in "Merchant Sailing Ships" talks about tumblehome in Merchant ships likely being just "design by tradition". In most ships it reduced internal capacity - not good in a cargo vessel. As time went by, merchant ships had less and less. The clippers for example were all wall-sided.

- Norm

[johnw]

A Yankee kettlebottom could carry twice the tonnage of cargo it paid port dues on, partly because of the tumble home in the topsides. Of course, they crossed the oceans at a stately three knots, but it had not yet been discovered that time was money.

[Jay Greer]

If you are not mounting cannon on your gun deck or in a madding attempt to save slippage breadth or weight above the water line, the two factors that tumble home affords in a modern sailing craft is that as the boat heels, there is less distortion on the lee side of the hull. This imparts a better balance to the hull when beating to weather or on a close reach and creates less weather helm. One small factor is that tumble home on the weather side of a sailing hull creates less windage.
Jay Greer

[Andrew]

I thought tumble home was what we did late Saturday night?

[johnw]

I thought tumble home was what we did late Saturday night?

I have no memory of that.

[John B]

and there, we see the genesis of the name at least.

[Lucky Luke]

Andrew :D :D :D

[Lewisboats]

I thought tumble home was what we did late Saturday night?

You forgot the "S" as in "S" tumble home.:D :D

Steve

[Gulfcoastbreeze]

Ultimately it comes down to looks for so many builders and designers, certainly in recreational craft.

[john welsford]

In that respect it is often used by a designer to reduce the apparent height of topsides, or the width of the transom where the clients desire to have two ensuite bathrooms, a stand up shower and 9 berths in a 25 footer leads to something that might otherwise look like a cheap apartment block.

John Welsford


Ultimately it comes down to looks for so many builders and designers, certainly in recreational craft.

[peter radclyffe]

it affords more protection to the topsides, bulwark, chainplates, channels etc when alongside, & its aesthetically a better way to finish a lot of sterns

[Raka025]

Concordia yawl's have it . . .

[Big Woody]

http://www.imagestation.com/picture/sraid217/pe05f6e51a30d730ff7f62671dd8affe2/ec5d77d8.jpg

I think that bears repeating. :D

[John B]

We have about an inch and a half or two inches of tumblehome in the middle third of Riada. You can see it here in the general area around the name.
http://i227.photobucket.com/albums/dd48/Waione_photos/Riada/240_4050_1.jpg
She was built 1975 but as you can probably see , she was built without regard to rule ( no weird hull distortions below the w/l and a fairly firm transom ) as a fast cruiser/, ocean cruiser/racer.
So the tumblehome was put there for the reasons that Hwyl and Jay state, to ease the flow on the leeward side, ie speed giving reasons.

Its a total pain in the arse and requires all sorts of fender arrangements to protect the topsides, especially when coming into an unfamiliar dock.( And no , I wont be putting a rubrail where its needed ( about a foot or so down the hull);)

[seedtick]

Big Woody

Here's a better repeat.

Originally my pics were on imagestation and when they closed up, so did the links to the pics

Here's what the original pic looked like. It's a style of pirogue we call a lake pirogue. The tumblehome gives you a bit more freeboard without greatly affecting the lines of the boat, makes paddling a bit easier than with taller sides and also allows you to pull fish in over the sides without taking on water. Probably other benefits that I haven't listed

http://i294.photobucket.com/albums/mm117/seedtick/IMG_0139.jpg

[tprice]

Hasn't been mentioned yet but tumblehome kept the shrouds from bearing on the structurally vulnerable bulwarks. From the channels, the shrouds angle to the mast is clear of the bulwarks because of the tumblehome.

[Big Woody]

Here's a better repeat.

And here I thought you were just the strong silent type, and a man of few words. :D