Did someone mention weather cocking?
I would think the upswept stern out of the water would catch the wind more.
Paul S.
wish I got one
I was there in the last few months before they closed,I should put money down on one
Have both - like both
Also helps sort the handling from the hype. Either style stern can behave any number of ways. Depends on all the other factors. Volume (distribution) and rocker being key.
Of the 10 kayaks that have passed into my hands 3 were relatively plumb ended (QCC and 3 skis - all designed to handle waves well and grab energy to surf). One other had a chopped transom (Tsunami X-1 - made for surf/rock garden play). 3 were more “Greenland” in inspiration (a Pintail, a Sparrow Hawk, and a self made SOF). The remainder a mix but more angled than not (A Heritage Shearwater, a WS Tarpon160, and a Stearns inflatable that really has no business in any discussion even casually discussion anything related to naval engineering L).
Weird mix maybe, but definitely not following any dogma. I’ve demoed a couple dozen more - also a good mix. One thing I am quite sure of at this point is that bow and stern slope alone tell you almost nothing about handing and performance.
Many pointy ended kayaks in profile behave like more plumb kayaks with thin wedges grafted on above the waterline for desired appearance (Fosters, KajakSports, etc that still manage to distribute volume over a more gradual arc). Others act like more plumb ended hulls with the volume sucked out of the ends and a wedge below water cut off - behaving much shorter than they are and having more volume concentrated in the middle (Pintail, Romany, etc).
The difference in volume distribution - fuller ends vs. fatter middles - is where I notice a divide between the “feel” people prefer. Each has their reasons for what the they like, and a few even have something to do with what the kayaks were designed for!
The majority of designs are somewhere in between - for good reason - and this further muddies perceptions. People with kayaks that are not really strongly designed either way will still see their kayak as being more one or the other depending on what aesthetic they prefer or what camp they’re most influenced by.
Something I’ve noticed is: The newer the design - the less clear the line (Aquanaut, Force series, and notably the good looking Scandinavian offerings from Point 65, Skim, etc.).
Or maybe I’m the only one seeing this evolution away from fine ended potbellied fishform designs? I AM crazy enough to build a swedeform “Greenland” SOF with no gunwale pinch and only minimally pointy ends… 
Take a look at the attached image showing an Impex Force 4, and two chopped versions with progressively more plumb ends (this kayak is not being singled out for any reason - I just happened to be looking at it while typing this):
http://www.appliedeccentrics.com/kayak/forces.jpg
The changes result in a huge difference to the human eye, yet there’s the same amount and shape of hull in the water. At this point nay sayers will say: “That’s only true on flat water” - but is it? The small amounts removed from the ends cannot significantly add to buoyancy when submerged, so all three bows and sterns will cut into or ride over waves to the same degree. The ends on the original are not shaped in a way to provide mechanical lift either. Result? Same handling. In waves the ends are out more than in anyway. When they are in, the extra is just more to grab sideways and contribute (slightly) to broaching forces. More in the wind too. It’s also extra weight and more boat to store. All three variations should still shed weeds well enough - and in waves the vertical action clears them or puts them on deck anyway.
So why keep the ends? Well, they look nice and Impex went to a lot of trouble to add those nifty finger grips underneath. Both good enough reasons for me - just don’t try to sell me on any hydrodynamic theories.
… and an even scarier image…
– Last Updated: Oct-07-06 1:35 AM EST –
http://www.appliedeccentrics.com/kayak/dark_side.jpg
What? Does that QCC have more rocker?! More myths to bust!
And just for kicks, a top view showing QCC differences in volume distribution:
http://www.appliedeccentrics.com/kayak/dark_side2.jpg
More at hips, less at catch - slightly fuller ends. Not a huge variance but the Force looks and feels noticeably fatter from the cockpit. For LWL comparison I'd have to chop the ends on the Force here too - the Force then becoming more comparable in functional length to a QCC 600 than the 700 shown.
just musing
Hmmm
Weatherhelm can be reduced by changing the ratio of windage ahead of the pivot point. Height is one example, rake another.
Doesnt explain stern rake now, does it?
How about DH’s claim of increasing waterline in texture water?
Hmmm, seems that if longer water line was the goal, just increase the water line length overall. More importantly, I would suggest a profound ignorance of the effect of a plumb bow; if water line was optimal for the design, is rake above a disadvantage? Yes, becuase the effect of a plumb bow is less the desired water line length, but more the effect of wave generation below the water line. Initiation of the wake should start at contact. If the contact progressively reduces after contact, the wave generation has to be initiated all over again, farther back. More simply, inefficient.
Behavior in rough seas? Don’t be so narrowly focussed on our dear sport. Ever seen international racing yachts, or fast naval ships? Talk about designs for rough water,they are plumb bows all.
So what is it about rake/overhang? Well, for speeds most paddle, is it any disadvantage? How about aesthetics? Perhaps it simply looks nice, and, 10-20 years from now, if most kayaks go to a plumb bow, it will have the cachet of antiquity. Come on, didn’t many of us think that a proper canoe should have recurved stems at one time (OK I’m odd, I don’t like them, preferring the looks of a plumb bow canoe).
Some other things- for those that say plumb bows would not work for landing on surf beach- something I have heard- my snotty response is, you gotta get out more. Rocker- the change in draft (that is under the water line, not above) will make a difference in landing, but not rake. Anyone argue with this, I just gotta say, you obviously havent’t tried it.
But- something contrary to all this. I have heard that one reason for the rake is to deal with landing on ice floes. Hmmm, plausible, to me.
But again- landing in nasty placse such as rock shelves, surf blasted islets- it is all about the hand hold, and overhang rules.
One last thing- kelp. While rocker deals with most of this, in breaking seas in kelp, what a difference! And even highly rockered boats with plumb stems (example, the otherwise superlative Coaster)have a nasty habit of collecting salad on them, or even coming to a sudden shocking halt.
Minor for most, but it does exist.
Karl (who thinks touring kayaks 10 years from now should have plumb ends, cutaways in front of the cockpit , higher front cockpit coamings to be able to keep the knees together, drop down skeg/rudders with tiller/push bars and/or twin adustable fins just aft of the cockpit, and a beer can holder in front of the seat that is currently only seen in some rec boats)
Ok, Now back to genetics…
I’ve been hoping some of the SoF builders would elaborate on the original designs of sea kayaks. Not having built one but imagine that it was easier and stronger to build pointy ends than try to build plum ends, not to mention sewing on the skins.
From what I read I get the impression that the Brit style evolved from one original kayak brought back to England. Seems they are slow to change some of the original style, thank God as I think they are the prettiest boats. With modern construction techniques they are becoming lighter and even more desireable.
IMHO waterline length is overrated unless the boat is built to a racing formula, I would rather have a pretty boat with pointy ends.
In context of Greenland…
… designs (in which overhangs and other elements can vary considerably), some possible advantages:
Easier to skin with less seams (my nylon skin has no stitches below the gunwales).
Easier to carry and lift onto racks (where dogs can’t eat them) with heavy mittens on.
Angles optimized so skim (thin black) ice can’t cut through skin.
Easier to run up on thicker ice.
Can help when wiggling (hip action) the qajaq up between flows that are being forced together rather than getting crushed (finer ends giving less to hang up and allowing slightly more wiggling/twisting)
Gradual entries can reduce hull slap - and quieter is better for hunting craft.
Finer ends are more provide better camouflage by blending in with the surrounding environment (wave ripples, sky, ice, and shorelines better). Spooks seals less.
I’m sure there are more. The thing to remember is these are hunting/work craft - not recreational toys. Different needs and tradeoffs. Nothing on native work craft is arbitrary or driven by marketing (those a sense of style is clearly present).
Nice post
I for one have no issue with someone choosing a kayak based on emotional values such as aesthetics. Designers spend a lot of time on seam lines, flowing lines etc., to make a craft appealing to the eye from all angles. I believe few sea touring kayakers have any real interest in design, or the science behind it. They buy what looks and feels good to them. The fun starts when they apply crazy logic to reinforce that choice. If ya like it, paddle it…ocean doesn’t care.
My slant is just to encourage people to play around with all this.
My most recent boat purchases
have been old school river runners (white water) for my wife and self - A Piedra and an Animas.
Different boats for different strokes
Why fix overall length?
I don’t really understand the idea that getting the longest waterline length for a given overall length is “good”. Sure, if you are trying to meet some artifical rules set for racing, but what’s wrong with adjusting the overall length to match your desired water line and overhang?
My question is how the overhang changes the hull shape when edging or leaning vs. a more plumb shape. I can’t quite visualize it, but it seems to me that this is where there could be a difference in handling. Of course there is interaction with all the other factors like rocker, chine shape, etc.
Personally, I don’t give a rip what shape anyone else’s boat is, as long as they are being safe and having fun.
You’re looking at it backwards
You design waterline length for the performance envelope you want - and loads you want to carry at a given beam - and trim off anything that’s not needed.
On the other hand…
Once you decide on waterline and wetted surface area then extending the ends will give you more volume/storage area.
think about
versitility from overhang…as the boat is weighted more…it gains waterline length…so it retains length/weight…not just optimized for a single weight window. In racing there is a single weight window…not always true outside racing.
Best Wishes
Roy
Not useful space
Look at the addition from a top view. You’d be extending a fine entry of a plumb bow forward. A small wedge at best.
Gains drag x 2
You already add drag as displacement increases (increasing both skin friction and wave making drag). If the kayak also get longer as it sinks you only add to this drag. This addition is NOT in your favor.
Doing this in waves is even worse - as you give up more energy to the waves the more you have to bury in them. Cutting deeper costs forward progress. Some designs use this for stability reasons - dampening the ride (Explorer) so it’s easier to manage. Can make them more forgiving, but being slower - they need to be. Just more trade-offs.
Note the common preferences for short kayaks to play/hang out in the rough - and more plumb designs with longer waterlines for powering through upwind and grabbing rides down.
As already noted -typical paddling uses are so middle of the specs that all this stuff hardly matters - paddle what you like - just don’t mistake preference for advantage.
While LWL are selected for performance, customer expectations play a large role in driving overall lengths -with most “sea kayaks” being from 17’ - 19’ long, and the majority now between 17’ 8" and 18’ For designers to get a range of handling/feel in such a narrow length range they need to adjust waterlines from there. Want more playful? Shorten the LWL (leaving more overhang. What better speed and/or loaded efficiency? Keep more LWL.
Rocker can take either end of this range and make it behave more like the other (ex: QCCs have more rocker than it might appear - and more than several of the pointier ended designs). Tradeoffs…
Performance of more plumb designs like the EPIC 18, QCC 700 and CD Stratus should be compared to longer kayaks like the Seda Glider and CD Extreme that have similar waterlines - and not to other +/-18’ kayaks with overhangs and much shorter waterlines. Few of the “faster” British sea kayak even have the waterline of a QCC 600/500, and some less than a 400.
The interesting thing about the more plumb 18 footers is how good they are all around. The speed potential’s a bonus - not the only point of these designs.
this
would have some aplication if the boat or boats in question didn’t flare or become wider, the further into the water they settle. in otherwords this is only truly apliciable to a pointy ended box with flat sides. If a given boat increases in width the farther into the water, then it would be more desireable to arest the depth by adding to the length. As a plumb bow equipt boat settles deeper into the water, if it has a hull that gets wider by the gunwales then in effect it will become wider because it is not held higher in the water by the length change adding to the floatation of the hull.
Best Wishes
Roy
I might::
http://www.playthesea.com/
Never paddled it, but I hear Malcolm from Mega had a hand in designing it, so it may truly be a wunderkind in surfing sea kayaks. Agreed, the Coaster is a rippin’ little boat.
Dogmaticus
Superb post Grekay!
kindasorta
– Last Updated: Oct-08-06 11:43 PM EST –
You simplify a premise by saying length at waterline increases drag. If so, a boat with plumb bow and stern would have more drag than a traditional brit boat of the same length at waterline. There's a proportion component there. That's why you see race drivers draft, and why you see "long tail" versions of race cars at Le Mans and other fast tracks.
Having said that I don't find anything wrong with the notion that upswept ends are a historical projection and for aesthetics. There are claims that the upswept stern was engineered by the original designers to keep the boat facing upwind during hunting.
Helps climb over waves
Whenever in doubt about an engineering theorm, exagerate the example and you wil have your answer.
Imagine a kayak with a 90 degree angle at the bow and one with a long overhang. If you run a line from the under water bend of the 90 degree boat up to the deck, it will have no gain in boat width. On the one with overhang, the area under water up to the deck gets wider or fatter allowing it to climb up overwaves whereas the 90 degree entry has to plow through them. Same with a following sea. The overhang stern rises over the following sea and the 90 degree one gets shoved by the sea or is forced to slice through it.
All things being equal (rocker etc.) that’s it.
The overhung bow basically has it’s entry in to waves on an angle helping it climb and slice with less resistance. Some race kayaks with a more vertical entry get by because of the long length and extremely gradual taper of the boat and generally are meant for smoother waters. (no rocker to gain speed)