a lot of partial truths in these threads
race hulls DO have rocker. Take a close look at a surf ski. Ultra fine ends are NOT faster. Look at a surf ski of race boat. Plumb bows that blend to cross section quite quickly, creating longer water line and higher Cp thus higher potential speed. Pygmy guy is right about cross sectional shape. If building method is with flat panels using more at a narrower width creates a more round overall profile,(Baidarka) and it is the “overall” shape that matters to efficiency and handling, NOT a few hard edges. Hard edges cause turbulence (not enough to matter on a sea kayak) and you will NOT see them on race hulls. ON sea touring kayaks most are there for marketing reasons around traditional concepts. Neckar initially put them on poly boats as a stiffening strategy,same with BS diamond hull. But the believers came forth and the concept spread to composite boats for sales reasons, not because of function. Not suggesting one’s multi-edged hull is bad in any way. The overall shape may be great and that’s what makes it work and have what folk refer to as secondary stability, handling, etc. Same shape with sanded away edges would feel the SAME. Edges tend to focus wear and in poly boats can actually create a hinge effect.
Agree with Sitka here that it’s a mute point on any of these kayaks discussed. Race hulls are science driven. Most sea touring hulls are designed to be comfortable and efficient with huge emphasis on traditional appearance, etc. A Mariner Coaster is to many a funny looking little 13 ft. kayak but it is far more efficient and capable than most of the famous Brit designs folk are so fond of.
It’s all sort of like the songwriter who’s work gets interpreted very differently from their intent. In the end it doesn’t matter so long as the listener gets something cool from the piece. At times I think the science and truth about some of this stuff just takes the fun out of it.
Hard chines improve speed
Hard chines or rails as they are often called significantly improve speed while surfing. In other condition when they are below the surface of the water instead of on top of it they increase drag and reduce the speed of the boat.
The nice thing about hard chines I have notice on sea kayaks that rarely surf is that a bit of edging really will break the stern loose on a hard chine boat so they seem to turn more easily for me.
fathom also fast vs. rec boat
So, you are reacting mostly to the BIG difference from your rec boat – I could almost guarantee that you would experience the same BIG difference with the Fathom (and most other real sea kayaks for that matter).
FWIW, I love my Fathom (previous was a Necky Manitou 14), and my wife loves her Fathom LV (previous was a Tsunami 140). Yes, faster, sweet glide, you bet!
Showing what I meant in ways…
you are a boat designer, can balance this stuff off quite well. The casual paddler is not seeing what you do in a hull.
As to racing hulls having rocker - are you talking about true racing boats? Anything I said was about touring boats that are reputed to be faster, or not. I don’t think anyone talked about that category of boat, but it would be interesting to take a look at one of those hulls if I tripped over one in person and on land. So far the only ones I’ve seen were on the water paddling away from us.
“copious rocker” might be too strong
a modifier. “A surprising amount of rocker for a long, fast boat” would fit.
What canoes or kayaks, other than whitewater designs, can be said to have “copious rocker”?
On a related topic, watching the 4 man kayak sprint finals, I was impressed by the almost complete lack of hobby-horsing, compared to the sprint canoes and the rowing shells. That steadiness must have consequences for design.
You’re working up to a sharp
distinction between “planing” and “displacement” hulls? Because they’re ALL displacement hulls, though some of them plane better than others.
hard chines
My understanding is in line with some of the posters above, that hard chines don’t make your boat any faster…and probably slower due to increasing wetted surface area.
However…it does seems that there are a few relatively fast Brit/Brit Style touring boats that have hard chines: the Greenlander Pro, the Foster Legend, the P&H Bahiya, and the Azul Sultan.
do the hard chines make these boats faster…probably not. But they are relatively fast touring boats that happen to have hard chines. Of course they are not nearly as fast or efficient as true racing boats.
Hard chines can be fun on a boat though. They make it have an interesting and fun stability profile and they can carve turns nicely in many cases. Fun boats, but generally not the optimal design for optimal rough water handling and general use in my opinion.
Matt