Viking tumblehome sterns

It is in a museum after all!

 

In fairness to Human 1, His question wasn't really related to the model being accurate just in relation to it's tumblehome stern feature. It actually was the first Viking ship I've seen of this style and i was kind of surprised I had not seen it before. History and historical craft and armament are sort of a hobby of mine. Being from Newfoundland i'm sort of drawn toward Viking history. My home town on the west coast was only about 100 miles from their site in L'Anse La Meadows which allowed me several visits. The model is intriguing, would be very interesting to confirm it's authenticity and measurments. If they are what they look like it would further show that these anchient builders had a few more pratical designs up their sleeves.
As a side note i'm kind of intrigued with Australia right now in that My mothers family are Gillards a rare family name in North America. My other connection with your fine country is I did alot of communication system design for the RAAF on their Caribou while employed at DE Havilland in Toronto, who(De Havilland) stole me(money) in route from my RCAF term to join the RAAF. In the early days of settlement alot of Newfoundlanders actually migrated(kind word) under British policy to Australia. And of course everyone is aware of the Royal Newfoundlanders fighting alongside the Australians and the New Zealands in the Dardanelle campain of Walsing Matilda Fame.

 

Human 1 just read you post, did you personally view the model ? If so is my take on it's shape as viewed from the photo close to being correct ?

 

Here is an updated version of what I am talking about:

 

Similar Hull Shapes

The blue Halman/Nordica is a Norwegian Design having tumblehome in the stern but little to none in the rest of the hull.
The white damaged Barkhouse Motorsailer ( little to no tumblehome) is similar in shape to your post. It was built in Nova Scotia, I bought it for salvage, removed what i wanted for my new build and re sold it.
The white one at anchor (little to no tumblehome)is very close to what my build will look like but again it has that similar shape to your photo.
The other similarity your photo reminded me of was the Old New England Herring seiners of which i have some good photos somewhere in my collection.I seem to recall they might have had some tumblehome in their stern section.

 

It's quite a well known ship these days and I know of at least three functioning replicas which have been built. Ottar is berthed at the Roskilde Museum and is the closest to the original. Saga Siglar circumnavigated the globe a couple of decades ago (IIRC), but was fitted with an engine and full decking w/cabins. I don't know where she is now. Snorri sailed from Brattahlid in Greenland to L'Anse La Meadows in 1997/1998.

Personally I'm still of the opinion that the reason for the stern shape was primarily aesthetic. Looking at the ship as a whole, it seems like one of those things that is too trivial to make any practical difference. It would have been just as functional with a bit more tumblehome or a bit less. I think the shipwright just thought it was a nice way to finish off a knarr, in accordance with the old adage of "If it looks right, it is right".

For anyone who thinks that this is not possible, on the way back from town today I recalled a story I had read as a child. This was getting on for forty years ago, so I had to do a bit of searching to track down the source. It turns out to be from a chapter of Óláfs saga Tryggvasonar, about the building of the Ormr inn langi (the Long Serpent). This is about a known, historical ship built for an actual, real king.

From this it should be clear that, regardless of modern speculation, the ancient Norse themselves saw nothing particularly odd about a master shipwright hacking up a royal flagship just because he thought it might look a bit nicer if he made a few changes here and there.

 

VN #63

The image that started this thread was from Wikipedia.

http://en.wikipedia.org/wiki/Knarr

Way back at #11, I posted "Examining the model below the waterline, there is a keel that rises towards the stern and it seems to fade into the construction aft. There might be a small stern post or it could be camera flash. Knarrs also had a deeper draught than longships. However the model could be wrong?"

NED #60 reaches the same conclusion.

"Well that model is supposed to be of a knarr, and the only actual knarr we have for a reference point is Skuldelev 1. So, either that model was made to the Skuldelev 1 lines or the model's lines were invented by whoever made it. I don't know which is the case.

ETA: Looking at the image, my guess would be that it is modelled on Skuldelev 1 and the apparent broader stern may be an optical illusion caused by the angle of the shot. This is only my guess though."

Regards,

P

 

A Fisher motorsailer. The tumblehome stern gives added volume and a longer waterline.. Added volume aft on a double ender helps control hobbyhorsing .

 

Michael, that tumblehome stern shape has been driving me nuts as i knew i had seen it before on a larger vessel than the Halman/Nordica(I had a dealership for these) and you are exactly right"The Fisher". Of all the hulls out there the fisher is possibly the best example of stern tumblehome.Many sailers snub their noses at the Fisher and call her a sailing pig but i've always loved that hull. I put a bid on a 37 that (St John's NFLD)had 75% topsides fire damage with the intent of in stalling a deeper keel and a new lower superstructure but never won the bid. Still want to do this but age and energy is creeping in.---Geo

 

Fisher is a very nice motorsailer....the best in my eye. With good sails, a folding prop and a sharp wit they sail fine.

When I grow up Im going to buy one. I see a nice one for sale now...good shape.

I just need to grow up a bit more.

 

Pericles thank you for that wikipedia reference which in my mind is based on a museum model as mentioned by Human 1. Thus I bet my bottom dollar it's an accurate model and based on the wikipedia writeup which they would have gotten from the museum. I stand by my post #7. That and PAR'S post re design function covers the subject of why pretty well. Now NoEyes regarding the for look's theory I will go half way with you on that, Say they built it for looks and it functioned poorley or weak structurally it would have been discontinued. Thus function and strength was the top priority.

 

In the latest examples of tumblehome (in this thread), all appear to be purely aesthetics. There's not enough to offer significant crew safety and attempting to carry displacement aft with bulging buttocks, is about as foolish an idea as having sharp deadrise amidship for the same purpose.

If you want to ruin a double ender's steering, particularly in a rough slosh, just fatten up her buttocks and she'll quickly become the most cranky boat you've ever sailed. This is a long known and well understood issue with double enders and why they aren't so common. To get bearing area aft, for what ever reason you have to have overhang, usually a lot more then is desirable. This is because if you attempt to fatten up the hind quarters, you distort the buttocks so bad that the boat can't steer without also drawing out their "exit".

This "quick" set of curves in the last 1/4 of the LWL, will make a big "hole" in her quarter and/or stern wave train, which of course she must drag along with her, exponentially increasing wave making resistance, which in displacement mode craft, is a real speed killer (and why it's not done).

The examples above show slight amounts of it, not the tumblehome seen on downeasters, tugs or other working craft (as examples) where the crew requires this safety feature to be effective, rather then just a stylish fashion statement.

I have several double ended designs and work hard to keep the buttocks a straight as possible as they exit the water. This is the only way to get reasonable steering qualities out of this shape. This is also why the Fisher has such a bad reputation, her buttocks come out of the water steeply and heavily curved. Yes, this does offer some bearing area and volume aft, but it also causes the boat to want to bear away, in a rough bash to windward and makes steering difficult, especially when pressed. Does it look good, well to some people, but those that have had to wrestle with the helm on one, wouldn't consider another look.

As for it offering strength, well this is likely a moot point. None of my double ended designs would need additional structure or scantling changes if the tunmblehome was removed. This suggests I either over design or the shape isn't as important for strength as one might guess. Naturally, these shapes would impart some additional stiffness, but I question if this was an intentional desire and would suggest this is just an added benefit. Again, until frivolous and discretionary fund expenditures could be economically acceptable, shapes were purely functional or driven by some belief system. Life back then was governed by many "outer worldly" things and damn near every aspect of one's life, was preordained by some high priest, holly bonehead or other mystical reality from hell. Master boat builders where among the most higher revered of society, so they could impose their will on nautical design elements, but after that, they were under the same ridiculous thumb of social oppression as everyone else, which tended to stifle (literally) creativity.

 

Tumblehome aft at the sheer of a flat transom boat was done to protect the transom edge sheer plane.

Most of the local wooded boats "roll" the top of the last two or three stations inboard.

In maine this roll... tucked sheer ,tumblehome, at the transome , is also understood.

 

Please, 1.0

 

Well PAR as one who has experienced exactly what you are talking about in your first two paragraphs but not fully understanding why other than my own thoughts of too much boyancy aft and not having enought design knowledge to also equate it with creating a hole and a dragging wave i now know the full cause and effects. What I am talking about is my sailing experience on a CORBIN 39 over one summer. In a following sea with wave heights as low as 8 to 10 feet she would lift about 1/3 of her rudder out of the water. The other design feature i was shy on was she has a fairley fine entry. Like the Fisher I was in love with this hull (purely astetics) but after sailing one i sort of lost my desire to own one. Now before the Corbin owners out there jump on me this was a kit boat configuration assembled by a friend and possibly ballast and interior layout (weights) played a role here. I do think the Fisher has less volume in her hind quarters than the Corbin so it might be less cranky. I don't know i've never sailed one in a following sea which by the way is a test that will make or break a design for me. I can always power to windward but no engine in the world will correct the design flaw of a cranky boat in a following sea. I hate to mention BRANDS here as it upsets owners but we all have different needs and uses from our non perfect vessels and like all Designs the Corbin has alot of good points, no boat is perfect and this is just one mans personal opinion ( not a designer, not an architect, just an old self taught builder with alot of rough sea time) which really counts for nothing in the overall sceme of things.

A yacht is not defined by the vessel but by the care and love of her owner