Fast Racer

[tx river rat]

Matt
What would be the best hull shape for a fast boat in the 18 ft class from 20 to 22 wide at the bottom.
Ron

[jem]

Generally, a rounded hull cross section offers the least resistance because of the least possible wetted surface area.

A hull that offers the least amount of turbulence will be fast too. That's why your Cuda is fast on flat water. It might not be rounded in cross section and has a little more hull surface area.

But the hull surface as a whole is very "clean" running in the water and causes little turbulence.

[tx river rat]

Do you think an added 2 ft would be noticeable in the cuda as far as speed goes.
They have a race later this year that is pretty much open water,6 miles up a river and six miles back down. Handling want be as big a factor as straight line speed is.
Ron

[jem]

There's the diminishing returns factor: After too much length it starts to slow you down.

But 18' should be pretty fast. The fastest situation will be if you can get it to draft 3"-4" while on the water.

[tx river rat]

would you have to go narrower to accomplish that?
Ron

[jem]

payload?

[Jimmy W]

Matt
What would be the best hull shape for a fast boat in the 18 ft class from 20 to 22 wide at the bottom.
Ron

Matt, How would you think that the 18' Cuda would compare to the long South Wind narrowed down to this width?

[jem]

NOTE: THIS IS ANSWER IS REGARDING THE STITCH AND GLUE, (BUILT WITH PLYWOOD DESIGNS) IN QUESTION. ANSWERS WOULD CHANGE IF WE WERE DISCUSSING WOODSTRIP SHAPES.

ok got that out of the way.

The only way I could compare it would be to say they had the same waterline and displacement at a given depth.

So let's say that.

The South Wind has a 90-degree twist on it's bottom panel that allows for the sharp entry/exit, real nice rounded stems and the control that offers. Looks a lot better too.

Cuda does not. Just straight panels except a little rounded off at the very tip which we can get away with by bullying thin plywood to make that shape.

Flatwater:

From a turbulence perspective, South Wind has a bit more because of the twist... takes a little more energy to push the water past that.

In race of equal paddlers in these size boats, Cuda would likely win. There's lot of ratios and coefficients that could be studied to try and predict by how much. But that's much more in depth studying.

Choppy Water

If you go any distance in water where you need to brace to maintain balance, then South Wind would win that race. An experience paddler would find it much easier to control in these conditions and use more energy stroking than balancing.

That's lot of generalities but that's the best way I can explain it.

[Jimmy W]

Thanks Matt

[hairymick]

G'day Ron and Matt,

Mind if I chime in here?

GENERALLY speaking the people I talk to all reckon around 17 feet is the ideal length for a solo paddling kayak - boat speed to effort required. Once that length is exceeded, the drag of the boat through the water increases to the point where the advantages of waterline length are overcome and paddling speed diminishes.

A very fast racing kayak sits low in the water and parts it like a spear. It has very fine entry each end as Matt has said and this in the front, reduces effort to drive it forward through the water. In the rear, the fine exit reduces the boats dragging water along behind it. The boat actually releases this water more easily.

To a degree, rocker in a wider boat can also achieve this but to a lesser extent. I believe this is why so many pirogues have such pronounced rocker.

I think a Cuda at around 17 to 18 feet would take a lot of beating in flat water mate.


Southwind 17-9 is a whole other ballgame My purpose in this boat was a very fast load carrier in open-ish water for extended, unsupported trips (which I have yet to find time to do) I think she would excell in the Everglades Challenge (watertribe?) and break the hearts and spirits of many of the big brand racers (including the Krugers) As a sprinter, I think Cuda is a better option.