Stupid new persons question about boat shapes

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SimonMW
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Stupid new persons question about boat shapes

Post by SimonMW » Fri Feb 18, 2011 3:10 pm

I'm still getting bewildered by the sheer number of different boat types and shapes available for different purposes. But one question keeps popping up in my mind with regard to river runners. Why are more boats not designed similar to slalom boats? Reason why I ask is that the slalom boat appears to be designed not only for manoeuvrability, but also to handle pretty big water. Is it just a case of storage space? Sorry if it sounds like a dumb question!

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Re: Stupid new persons question about boat shapes

Post by Ken » Fri Feb 18, 2011 3:17 pm

A slalom boat is designed to fit under slalom gates, hence the low volume and flat decks, as well as being fast and maneuverable.

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Re: Stupid new persons question about boat shapes

Post by Simon Westgarth » Fri Feb 18, 2011 3:28 pm

Ken wrote:A slalom boat is designed to fit under slalom gates, hence the low volume and flat decks, as well as being fast and maneuverable.
on Class II/III with few rocks.

Plus the modern sitting position for a white water kayak, has progressed some what from slalom boats, that have very specific rules that shape their design.

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Re: Stupid new persons question about boat shapes

Post by davebrads » Fri Feb 18, 2011 6:40 pm

Hard as I find it to contradict Simon (ha ha), in this case he is talking rubbish

The rules for the design of slalom boats isn't terrifically restrictive, not much more than minimum length and width.I don't believe that if the rules were scrapped there would be a great difference in boat design. They might produce some boats that will be a bit shorter, but even now some of the boats are longer than the minimum width.

At the top level some of the races are held on grade 4. Bourg St Maurice is not grade 3 in anyone's book.

There are some serious questions about the seating position in creek boats, the slalom boat position definitely allows more body rotation and better connection with the boat.

The slalom boat is the shape it is because it is the fastest shape, most of the time the bow goes round the poles, and the stern is cut low to give good edges to work off, and to allow the paddler to shorten the waterline at will in order to speed up turns. Too much bow volume and the boat is at the mercy of the water, being bounced around by the waves, lower volume allows the boat to cut through the waves. Finally the performance of a boat is measurable, because it is a competition boat built to do a specific job, the proof of the boat shape is in the race result, not left to personal opinion.

However, although they can be paddled on some quite pushy water, they aren't ideal. They require the paddler to be on top of the boat all the time. The shape makes them easy to pin, and once pinned the shape won't resist the force of the water for long, and you wouldn't want to be pinned in a boat while it folded round you. If you don't boof stoppers well you are going to be looking at the sky a lot - rather like the RPM and other boats that are similar in general outline to a slalom boat.

Finally, paddling a slalom boat on some tasty water is very fulfilling. They outperform anything else, being faster and smoother across the river and eddy lines, with snappier turns through which the speed can be carried - just don't hit the rocks too hard! Unfortunately, all the plastic slalom boats I have tried have been huge dissapointments, although I haven't tried the latest boats.
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Re: Stupid new persons question about boat shapes

Post by DaveBland » Fri Feb 18, 2011 7:19 pm

Slalom boats are, to a degree, great for river running. Modern creeking down steep rock ditches, no, but something like the upper dart would be fine. Put on edge, they 'cut' though holes, rather than getting held up and the additional control and speed make getting the line easier if paddled aggressively. I paddled an old Premier II for years on all sorts of stuff and it is still my fave boat I had. It had 'modified' shorter ends and used to fold behind the cockpit in big holes, but weighed so little you could spin it with one stroke.
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Re: Stupid new persons question about boat shapes

Post by Randy Fandango » Fri Feb 18, 2011 8:28 pm

davebrads wrote: There are some serious questions about the seating position in creek boats, the slalom boat position definitely allows more body rotation and better connection with the boat.
Interesting view.
My personal experience is that the wider apart, higher knee position I achieve in each of my creekboats (and for that matter in my playboat and my river running boat) allows me a much more comfortable seating position than I achieve in my slalom boat where my legs are necessarily positioned closer together with lower knees.
Additionally this position enables me to sit upright or indeed lean forward a little much more easily than I can in my slalom boat. This is easily tested by the simple process of sitting on the floor with your legs flat and together. Then try slightly parting your knees and lifting them somewhat (to replicate the seating position in a modern ww boat) and if you're anything like me you'll find it vastly easier and more "natural" to bring your body upright or forwards, as one would want to be in a boat running ww.
As for body rotation -- I personally find that my ability to rotate is essentially the same in all my boats, including my slalom boat. The biggest restriction for me is my own abysmal lack of flexibility :-)
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Re: Stupid new persons question about boat shapes

Post by davebrads » Fri Feb 18, 2011 8:44 pm

It might depend upon how long ago you paddled a slalom boat. In the days when the cockpit was in the middle of the boat, the bow deck was very low and this meant your legs were very straight, and it took quite a while to get comfortable with this position. When the cockpits were moved forward (around 1987?) this allowed more volume in the bow, and a more comfortable sitting position, and now with the shorter boats the bow deck is considerably higher, and the position is quite comfortable for most people.

As far as the wide legged position is concerned regarding connectivity. When you make a stroke you want the force transferred as directly as possible to the boat, and most of this is done via the footplate. If your legs are very bent, then a lot of the force goes into pushing your knees into the deck rather into driving the boat forwards. The body rotation thing is easily proved by sitting on the floor, first with your legs slightly bent out in front of you, then with them bent out to the side.
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Re: Stupid new persons question about boat shapes

Post by Randy Fandango » Fri Feb 18, 2011 8:58 pm

Interesting. Not my experience at all Dave :-)
I tried the body rotation thing before my first post and my results were as I said.
If my footrest is properly adjusted, no matter how bent or straight my legs are I apply much the same force to it. But then just because my knees are higher in my creekboat it doesn't mean my legs are "looser" than in my slalom boat.
Actually I've been paddling contemporary slalom boats from the early 70s until very recently and while I agree they have changed over the years, for me their seating position lags waaaay behind any of my plastic boats both in terms of comfort and boat control.
Interesting that your personal observations are quite different. Goes to show how subjective personal taste is :-)
Giles

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Re: Stupid new persons question about boat shapes

Post by davebrads » Fri Feb 18, 2011 10:13 pm

Randy Fandango wrote:If my footrest is properly adjusted, no matter how bent or straight my legs are I apply much the same force to it. But then just because my knees are higher in my creekboat it doesn't mean my legs are "looser" than in my slalom boat.
To be honest I was repeating something that another coach told me when I was on a course, and it made sense to me then. But what you are saying makes sense too, I think I might have to experiment a little.
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Re: Stupid new persons question about boat shapes

Post by Randy Fandango » Fri Feb 18, 2011 10:19 pm

davebrads wrote:
Randy Fandango wrote:If my footrest is properly adjusted, no matter how bent or straight my legs are I apply much the same force to it. But then just because my knees are higher in my creekboat it doesn't mean my legs are "looser" than in my slalom boat.
To be honest I was repeating something that another coach told me when I was on a course, and it made sense to me then. But what you are saying makes sense too, I think I might have to experiment a little.
See -- our debating here is an excellent thing Dave. It seems to always end with one or the other of us deciding that we need to go paddling to test out a theory.... :-)
Giles

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Re: Stupid new persons question about boat shapes

Post by jmmoxon » Fri Feb 18, 2011 10:25 pm

Slalom boats have a minimum length, width & weight requirement - the fact that none of the designs exceed these suggests that faster designs could be smaller.

The thin ends reduce the waterline of the boats, allowing them to turn faster, so they could be shorter. The Italians produced single race 7kg kayaks, which is why the minimum weight requirement was introduced, so richer competitors didn't have that advantage. Not sure whether reducing the width would improve things.

The wider knee position makes modern boats more comfortable & more stable than slalom boats, whether it reduces power transfer would need some research...

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Re: Stupid new persons question about boat shapes

Post by davebrads » Fri Feb 18, 2011 10:56 pm

There are several current boats that are longer than the 3.5 metre minimum, so the jury's out on whether the ideal length for a slalom boat is shorter or longer than 3.5m. It probably depends upon the course. The minimum width restriction is probably only to stop things getting too silly. The weight restriction as Mike says was brought in to stop manufacturers producing one race boats, but I remember UK manufacturers making boats like that. I was at a race at the Serpents Tail where the deck of a brand new Krakatoa, made to about 6 Kg, was crazed after a single run. The boats Pyranha made for the Bala 81 worlds weren't much better, by the end of the race they were getting rather floppy, being all kevlar boats. Technology has advanced quite a bit since then, it is commonplace for manufacturers to be making carbon boats around the 6-7Kg mark, and they are quite capable of lasting a race season. All they do is add a couple of kilos of lead under the seat, which barely changes the performance at all. As I have to buy my own boats mine is made from a Carbon/Kevlar weave, and came out at about 9Kg, including the seat. It's over three years old now, and I have just replaced some sections of the seam tape. And that is using it two or three times a week, every week, and racing in Premier and division 1 events. The biggest advantage of the carbon boats is that they are super rigid, which has a much greater effect upon performance than the weight reduction. The disadvantage is that they are a bit like eggshells, they don't take big knocks too well.
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Re: Stupid new persons question about boat shapes

Post by jmmoxon » Fri Feb 18, 2011 11:01 pm

The boats may be longer than 3.5m, but what is their waterline length?

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Re: Stupid new persons question about boat shapes

Post by davebrads » Fri Feb 18, 2011 11:02 pm

jmmoxon wrote: The wider knee position makes modern boats more comfortable & more stable than slalom boats
I would question why does a wider knee position make the boat more stable? At first it seems obvious, and it might feel more stable, but in a similar vein to what Giles said, if you are locked into the boat, the knee position is irrelevant. Your control of the boat comes from your hips.

Can't you see how much I love these technical discussions, I can't help but get involved
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Re: Stupid new persons question about boat shapes

Post by davebrads » Fri Feb 18, 2011 11:09 pm

jmmoxon wrote:The boats may be longer than 3.5m, but what is their waterline length?

Mike
That is a question that I don't think can be answered very easily at all. At rest, the waterline length is usually quite long - maybe 3m? But get the boat running, and the stern goes down and the bow rises up, so that the waterline is a lot shorter. This has a detrimental effect upon the speed of the boat, so they can't overdo it. However, when the boat is in this position, it is very responsive to steering strokes, so it's not all bad. So a boat that is 10cm longer than another could easily have a shorter waterline when it is running due to its shape. But this is getting too technical even for me, but I know a couple of people that could bore you about this stuff for hours.
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Re: Stupid new persons question about boat shapes

Post by jmmoxon » Fri Feb 18, 2011 11:17 pm

From wikipedia:
Development of Slalom Boats
In the 1960s and early 1970s, boats were made of heavy fiberglass and nylon. The boats were high volume and weighed over 65 pounds (30 kilos). In the early 1970s Kevlar was used and the boats became lighter as well as the volume of the boats was being reduced almost every year as new designs were made. A minimum boat weight was introduced to equalize competition when super light materials began to effect race results. The I.C.F also reduced the width of the boats in the early 1970s. The gates were hung about 10 cm above the water. When racers began making lower volume boats to sneak underneath gates, the gates were raised in response to fears that new boats would be of such low volume as to create a hazard to the paddler. Their low volume sterns allow the boat to slice through the water in a quick turn, or 'pivot'.

Typically, new racing boats cost between $1,200 and $2,500 (or £650 onwards for the cheapest constructions in fiberglass). Usually boats are made with carbon fiber, Kevlar, and fiberglass cloth, using epoxy or polyester resin to hold the layers together. Foam sandwich construction in between layers of carbon, Kevlar, or Aramid is another technique in use to increase the stiffness of slalom boats.

Recently, the minimum length of these boats were reduced from 4 meters down to 3.5 meters, causing a flurry of new, faster boat designs which are able to navigate courses with more speed and precision. The shorter length also allows for easier navigation and less boat damage in the smaller man made river beds that are prevalent in current elite competitions.

Boat design progression is rather limited year to year. Designs tend to focus on providing optimal performance for upcoming critical race venues. Olympic years tend to generate boat designs with specific performance characteristics tuned for the upcoming Olympic course.

Slalom boats used in competition must meet the ICF specifications for the class. Directly from the 2005 ICF Slalom rules:

7.1.1 Measurements
All types of K1 Minimum length 3.50 m minimum width 0.60 m
All types of C1 Minimum length 3.50 m minimum width 0.65 m
All types of C2 Minimum length 4.10 m minimum width 0.75 m

7.1.2 Minimum Weight of Boats (The minimum weight of the boat is determined when the boat is dry)
All types of K1 9 kg.
All types of C1 10 kg.
All types of C2 15 kg.

7.1.3 All boats must have a minimum radius at each end of 2 cm horizontally and 1 cm vertically.
7.1.4 Rudders are prohibited on all boats
7.1.5 Boats must be designed to, and remain within, the required dimensions.
7.1.6 Kayaks are decked boats, which must be propelled by double bladed paddles and inside which the competitors sit. Canadian canoes are decked boats that must be propelled by single-bladed paddles and inside which the competitors kneel.
There are rules governing almost every aspect of slalom equipment used in major competition, including sponsor advertisement. Some of these rules vary from country to country, consult your national canoe and kayak governing body for direct rules.

It is common for boat manufacturers to build elite competition quality boats lighter than the required ICF weight, thus competitors affix weight to the inside of the boat at the center point. This practice allows the boat to be more responsive to directional adjustments.
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Re: Stupid new persons question about boat shapes

Post by andya » Fri Feb 18, 2011 11:38 pm

davebrads wrote:paddling a slalom boat on some tasty water is very fulfilling. They outperform anything else, being faster and smoother across the river and eddy lines, with snappier turns through which the speed can be carried - just don't hit the rocks too hard!.
I'm with you on that Dave, I hate paddling the modern "Tupperware". So slow and "dead" feeling.

A "good" plastic slalom boat would be a dream come true ... SL350 maybe?? Donsa??

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Re: Stupid new persons question about boat shapes

Post by jmmoxon » Fri Feb 18, 2011 11:47 pm

Plastic boats can be almost as light as slalom boats, but then they lose rigidity & break just as easily - but plastic has opened paddling up to a far wider public...

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