Where does the Hurricane have its center of bouyancy compared to its center of gravity ?
I am making some repairs and would like to know.
Can anybody share paddling experience in the Hurricane with the rudder moved forward from its original position;
I have heard that it has been done, but I have not heard much feed back how it worked out.
Thank you.
Submitted by eckhart on Fri, 10/19/2007 - 12:45pm
This should answer your question
Hurricane Hydrostatics attached
Cheers Rambo</br/></br/></br/>
#1 Fri, 10/19/2007 - 5:06pm
yes..but how many beers fit inside it?
#2 Fri, 10/19/2007 - 5:50pm
Easy .... 314 litres of beer if you're Aussie or 10617 ozs of beer if you're American or 663 pints if you're British.
Internal volume of Hurricane is . 314m3 (cubic metres)
It's actually less in Australia because we have .03cm of foam buoyancy inserted in the hull to meet AOCRA specifications.
and we have bigger Goolies .. ha-ha-haaa
Cheers Rambo
#3 Fri, 10/19/2007 - 6:26pm
Thank you Rambo. Great video - the rambocam. You didn't huli, did you ?
Did you measure and compile that yourself ? With the % center of bouyancy less than 50 % it is a 'fish' instead of a 'swede' shape; racing kayaks are all swede shape aren't they. Do you know the reason why the Hurricane is fish shaped ?
Where should the center of gravity of the paddler be ?
On top of center of flotation, on top of center of bouyancy ?
FYI
http://oneoceankayaks.com/smhydro/hydro.htm
and
http://clydewinter.wordpress.com/2006/08/06/ivbuoyancy-and-uprightness/
#4 Fri, 10/19/2007 - 6:58pm
No not a Huli as such, just got whacked by a wall of white water, knocked me into the Ama space. We need foot straps on the OC1 like surfskis have to aid anchorage in these situations.
It was profiled in a pool with 70kg (my weight) in the cockpit and then laser profiled on dry land. All data entered in Hydro program and what you see is the result of this, so it's very accurate. It was done for personal evaluation reasons. That's only a portion of it.
It's fish shaped because the bloody Hurricane is under water more than above, at least it is where i ride it. ha-haaa.
Peggie arrives next Wed at last. What a long wait.
Thanks for links, already got all that stuff.
Cheers Rambo
#5 Fri, 10/19/2007 - 7:18pm
Very nice, Rambo. I was wondering about your new boat while watching the video.
In what sense did it help your paddling/set up in the 'real world' to know the hydrodynamic data ?
LONGITUDINAL WEIGHT SHIFTS
When a weight is shifted longitudinally (fore 'n' aft) the net effect on a ship is similar to a see-saw, one end goes up and the other goes down. The pivot of the "see-saw" is located at the Longitudinal Center of Flotation (LCF).
That answers one question: when you add load ( a paddler ) with its center of gravity located at LCF you have parallel sinkage, that is the draft added aft is equal to the draft added front.
Rambo, do you have more detail data on sinkage ? It is not linear. So what is the sinkage at diiferent weights less/more than 30 kg ?
#6 Fri, 10/19/2007 - 8:08pm
Rambo...or anyone else who has delved deeply into this stuff,
I weigh 190lbs (86.4 kgs) and paddle a hurricane. Since I have never paddled another OC1, I have nothing to compare to. I never thought of it until reading this string, but am I overwhelming the boat?
If yes, then the next question is what boat would handle my weight and perform well in small to flat water?
Raphael
#7 Tue, 10/23/2007 - 10:47am
Good question ... it depends.
With 86 kg and the rigged boat your overall weight is just above 100 kg;
It's designed for an overall weight closer to 90 kg. At 90 kg the boat sits on/in the water as intended by design, intended length of waterline etc.
From the perspective of the boat, the hull is meant to displace about 90 kg of water.
As you are heavier, the boat will sink deeper into the water; in your case it has to displace 100 kg. This is called sinkage.
The sinkage tells you how much a boat will sink for a specific weight.
See my question above, the sinkage depends also on hull shape.
Lets assume that the sinkage for 10 kg extra weight may be 1/2 inch; your boat will be 1/2 inch deeper in the water.
That increases the surface area under water, the wet surface area.
This wet area accounts for the resistance, and you will end up with a few percent higher resistance, that is, you have to paddle harder than a lighter person.
Other factors come into play. If you are sitting behind the center of flotation, your boat sinks more aft and the bow sticks up - think position on a surf board.
You probably want to have your own center of gravity over the center of flotation to avoid that.
Having said all that, it still depends;
what are the conditions, where do you paddle, how do you paddle etc.,etc. In summary it should be ideal if you load the boat to the intended weight only.
The heavier the worse anyway. I read that 1 % in extra weight can cost you 0.2 % in speed, with the same effort.
There are many good 200 - 210 lbs paddlers on the Hurricane.
Rambo is standard weight, he just got a Pegasus, because he feels that it might do better for him in certain conditions.
I do not think that they overwhelm the boat. It is more like racing on a race bike that does not fit your dimensions all that well.
Foot wells and seat should be movable in boats, or custom made, so that you can balance the trim according to your specs, conditions etc,
I think in the future we will see more of that.
#8 Tue, 10/23/2007 - 3:03pm
Eckhart- this is by far one of the more intelligent responses we have had on this forum ! Thanks you ! I have enjoyed your analysis of the Hurricane . It give paddlers very clear parameters. Can you do these spec sheets for other canoes ?
#9 Tue, 10/23/2007 - 6:37pm
Hi pullingwater
The measurements are actually from Rambo. So cudos to him.
If you change all the things that you do not like about a Hurricane you would end up with a Pegasus ..
more rocker, a little more comfort, different ama, different seat,
position more forward, a little better in the larger surf ...
I assume that if you change everything aboput the Pegasus that you do not like, you may end up close to the Hurricane ? I do not own a Pegasus, so I do not know.
Ideal may be:
hull of the Hurricane, yet a little more rocker
seat/footwell moved forward and adjustable- you need to be able to adjust the trim of the boat
cockpit of the Pegasus/Fusion - Fusion most comfortable
ama design from Brad Cole, custom for Hurricane - a little wider, flatter bottom
bow like the Zephyr/Epic v10 - volume up front more vertical
rudder moved forward - like Pegasus/Fusion
a little more overall volume than Hurricane/Pegasus, up to ~ 220 lbs
displacement boat + paddler
It can be done, get an older model, take a saw and start fulffiling your dream. < I mean it.
The Zephyr is moving into this direction, I assume the Scorpius is too.
Maui Kjeldsen's boat looks like that too.
Regarding other models, I do not know them well.
#10 Wed, 10/24/2007 - 10:36pm
Eckhart, that's exactly why i profiled the Hurricane, ... to understand why it was such a fast canoe. I also had a project where i was going to use what i learnt from the Hurricane to design an OC2 for 2 small paddlers (70kg 155Ib each) built in the timber stripper method. Actually got as far a building the strong back and some hull samples and they were really strong and the finished weight of the canoe calculated out (based on the weight of the samples ) to 18 - 20 kg or 38 - 40 Ib. which is equivalent to double carbon OC2 canoes.
The advantage was not the weight factor but the fact that the hull parameters were based on 305 lb displacement + the weight of the OC2 40lb. What this means is that the Oc2 could be smaller, narrower, and shorter depth and therefore less drag, making theoretically for a faster canoe with that paddler weight.
As we know most commercial OC1/2 are designed too a broad range of weights, therefore they are a compromise.
I ditched the design when our Governing body AOCRA made it compulsory for manufacturers here to be licensed and approved and charged for the privilege. Not so in Tahiti, where design is encouraged.
Here are the sample tests . very technical ha-ha
I may one day finish the project, I'm confident it would be a very fast canoe and super strong. Cedar is stronger than foam for a core. The sample is 3/16 thick including "S" glass both sides. I have full plans, hydrostatics, drag figures and charts.
Cheers Rambo
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#11 Thu, 10/25/2007 - 3:02am
Here is another thought regarding boat design:
The pressure distribution on the hull changes when parts of the hull are out of the water.
That makes sense.
But what do you do with such 'knowledge' ? What does it mean in the ocean ?
Should you try to keep the boat as much as possible in the water when you try to catch a bump, that is, square it ? Or is it better to have the stern in the air and more pressure on the midship ? Or maybe the bow ?
Who knows. I think such are the reasons why boat builders go a lot by trial and error. It also suggests to me that local as well as day to day conditions have a considerable impact on performance.
#12 Fri, 10/26/2007 - 8:40am
Thanks to all for their thoughful responses and willingness to share information.
A great way to help this sport keep growing!
Raphael
#13 Sat, 10/27/2007 - 1:28am