A quick question just to satisfy my curiosity. I have seen many boats that claim to have a “Swede Form Hull.” Can anyone explain this further?
thanks
Matt
swede, fish and etc.
If the widest part of the kayak is at or near the midpoint of the boat’s length, the boat is said to have a symmetrical form. If the maximum beam is forward of the midpoint it has a fish-form hull. If it is aft of center the boat has a swede-form hull.
Put another way, LCB or longitudinal center of buoyancy is the distance from the start of the waterline to the center of the volume the kayak displaces. The percent LCB is the longitudinal location of the LCB with respect to the waterline. Percent LCB is what often distinguishes whether a kayak is ‘Fish’ or ‘Swede’ form.
Fish form kayaks have LCB less than 50% of LWL while Swede hull forms are more than 50%.
Makes sense…
Thanks for the reply. That is a great response.
This makes sense to me, but it brings up another question…why? What are the advantages/disadvantages or characteristics of each design. I would guess that this would affect how the boat would weathercock.
Are certain design boats associated with one type vs. another-----are “British style boats” and “Greenland Style” boats normally swede style hulls? Are U.S. hulls more generally fish form?
thanks
Matt
I have noticed that racing shells tend
to use the Swede-form shape while those who use the fish-form tout it as being more stable. I guess the Swede-form allows for a higher angle, more aggressive stroke (as the boat is more narrow forward of the cockpit). The Swede-form would also allow for maximum stroke efficiency when using a wing paddle.
swede vs. fish - - -
Mariner Kayaks is one of the few american manufacturers producing swedeform boats. http://www.marinerkayaks.com/
mariner will tell you that a Swede-form hull has many other advantages over fish-form. They include:
- Less pounding in head seas because they are narrower in the area where pounding occurs (but, bottom shape is a bigger factor in pounding so some V-bottomed fish-form kayaks will be softer riding than some flat bottomed Swedeform ones).
- Easier and quicker turning (turns are enhanced by the greater curve at the side of the stern quarter–and leaning makes this effect even more pronounced).
- Less weatherhelm (more windage and a longer lever arm in front of the paddler and less behind)
- Greater gear capacity (more of its volume is in usable storage space behind the paddler and less of the total volume is in the wasted space around ones legs).
- A narrower beam where the paddle enters the water means easier more efficient paddling (less boat to reach over) and less turning moment produced with each (less off-center) stroke.
- Less energy robbing pitching motions in head seas and less wave pressure on the bow than fish-form mean a faster smoother ride into waves.
is all that true? well, given that the vast majority of kayaks on the market are in fact symetrical or fish form, you might pause to reflect. Fishform advocates correctly point out that Swedeform is less directionally stable - all other things being equal and that fish-form and symmetrical-hulls are more efficient than swede-form designs.
i think it’s a matter of personal likes and dislikes. i’ve paddled mariner boats. i didn’t care for them. all my boats are British. i love they way they handle, the way they “feel” and the way they look.
One thing to add…
to the excellent responses to your great question is that the best designs of either type tend not to be too radical. In other words, both Fish and Swede designs seem to work best when they are so subtle that you really have to look hard to tell which type any given boat is. I have paddled both types and both work well.
Bill
unless
you are talking to a Mariner owner. 
With this shape (radical swede) the asymetric shape when placed on edge creates a pull to one side and allows the boat to carve turn like no other. a good trait in many eyes, unbalanced in others.
steve
swede… fish… swedish fish?
yum. ok i have nothing of value to add but i couldn’t read this thread without visions of those red gummy fish floating in my head. 
Finally!
A subject worth a heated discussion!
How about fish vs swede vs rusdder vs skeg?
Jim
(now to sit back and watch…)
Been Fascinated By Mariner Kayaks
and the fascination continues. Just going to have to build a Swedeform and see what I think. Right now, I think it would be a good boat to play the waves with but we shall see… Of course, chines placements, rocker and all that come into play as well.
sing
Too general
Most of the comment apply to specific boats - more than hull form types.
Best not to generalize like this - particularly if shopping. To many other design variable affect the same aspects of performance.
I have a slightly swedeform that handles rough water fine, it turns well - but I have a fishform that can turn circles inside it. It has plenty of foot/leg room. Proves nothing.
Designers select the form that will do what they want the kayak do do. Good ones come in all shapes. Pick based on use/features/fit.
goofy
to have the very widest part of the curve of the hull on edge soooo far behind you. IMO.
personally i want this bulge at my knee where i can push it and sit over it not /it/ behind me.
just a thought
steve
Yup. A Thought…
though Mariner owners seem to like 'em alot and regardless of the “goofiness.” I wish someone would get rid of an Elan cheaply around here. I’d honestly would snap it right up if the price is right, and gladly get rid of one or more of my other boats to do that.
sing
Swede round hull-rudder-wing paddle 
Not convinced in theory
that either shape has an advantage over symmetrical on a lightweight surface boat. I suppose a swede form would get off the line better from an at rest position but we tend to rock our hulls back and forth a bit altering the shape that contacts the water anyways.
I served in submarines and they utilize the albacore hull design intially developed with the Barbell (a diesel boat given this hull to see how the later nukes would perform) and this is fish form in essence. Fish form means a true foil for the most advantageous hydrodynamic shape. Catch a crappy and look at it from overhead. A foil of the most natural shape.
Rudders, daggerboards, leeboards, centerboards hydrafoils… All incorporate a foil if max speed and low drag coefficience are the desired result.
On a lightweight “skimmer” like a kayak? I just cannot see any distinct advantage. Just another opinion…
Great topic that comes up now and then. You should also search the archives.
Submarine vs. Surface craft
Very differnt things. Subsurface designs should not be looked to for comparison.
What… Are you not reading my post?
That is exactly my point of ponder. Something as light as a kayak on the surface of the water. I am not convinced that swede form or fish form for such a light craft under human propulsion can really be advantageous over symetrical. Get UNDERWATER like a rudder or a submarine and shape makes a HUGE difference. Get in a DISPLACEMENT hull on the surface and hull shape makes a huge difference again.
Still makes a difference…
…for small craft on the surface - just debatable what difference, as other design factors cannot be separated making it hard to know what’s going on.
Fully immersed bodies have different hydrodynamic environment than displacement surface craft and should don’t really belong in the same discussion. Maybe old subs that were faster on the surface (basically small surface ships that could blow ballast and sink) can be compared to kayaks, but not modern subs that are much faster submerged than on the surface. Their fishform shape is faster - but only submerged - not at the surface - so if anything they would indicate fishform is bad for surface craft speed. My Pintail agrees Fast Naval surface vessels tend to be more swedeform.
Enough.
If I want to think out loud in my posts I will Greyak. It’s not your place to say part of my text does not fit into the discussion.
I was illustrating where a given hull shape was advantageous as opposed to my own doubts about it or swedeform being advantageous to a lightweight small boat on the surface. I look forward to learning more.
Move on.
Sorry for the science L
– Last Updated: Mar-03-05 11:49 AM EST –
Intent was certainly not to limit discussion, but facts is facts.
Funny how you feel censored - while at the same time telling me what's "enough" *L*