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Test on stability of asymetrical hull

tx river rat

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Feb 23, 2007
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Jack and I have been kicking this around for a while and couldn't agree. Now I am a lot better with my hands than talking so I built a model about 1/4 scale of the bottom of the T-V asymetrical.



I just glue a couple strips down the center to stiffen it



I then marked a line 5 inches in front and rear of center this is pretty close to where my rear sits behind the center of the T-V and also a line parallel with the center line






I commandeered Magoos swimming pool for the test. My black lab
Break here
 

tx river rat

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Feb 23, 2007
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The line to the rear will simulate me sitting in an asymetrical boat,the line to the front will do the same but in a symetrical boat ,ok here goes.

I did some playing with some weights


I used half a brick 2 7/8 nuts and a 7/8 socket, the water is just below the top of the foam
now this is asymetrical

next pick I put the brick on the line in front,simulating symmetrical seating arrangement.

Put the brick on the line the same distance from the center



now this is what happened






Just the brick turned it over didnt have the 7/8 nutts are socket on it.
 

tx river rat

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Feb 23, 2007
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Summary
Testing done by the Smith redneck institute
An asymetrical Swede form boat is more stable than a symetrical boat with the same length and width measurements.
Ron
 

Kayak Jack

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Aug 26, 2003
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Nice test, Ron. I understand what you did.

When you sit in a boat, symmetrical, Swede, or fish forms, do you sit at the wide or narrow part? Now, take a look at where tandem paddlers sit. Your experiment would suggest that two paddlers can't sit in the narrow ends of a boat and get it to work.

In your experiment, with the weights towards one end, the boat doesn't roll like a real canoe/kayak would. It both pitched and rolled. Roll the boat over at 90 degrees instead of dipping one end down, and I think you'll observe different results.
 

tx river rat

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Feb 23, 2007
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Jack
That want fly,the marks the weights were set on were scaled out to the seat placement in my T-V so the mark in the wide part of the boat is my normal seating position,this has nothing to do with a tandem ,it has to do with asymetrical being more stable than symetrical. two paddlers in a canoe is a whole different game.
Oh just to let you know I went back and cut the foam symetrical and still had the same results ,the same weight ,the light one would roll this boat.
Normal seating in a solo boat is 14 to 19 inches behind the center line,thats what I set the test on.using symetrical and asymetrical placements.cant get any more real than this unless you use a real boat.Oh I specified swede form.
and in a asymetrical boat you will never get a 90% roll one end is narrower,the other end is widder so it is going to be a uneven roll never 90%.
Ron :mrgreen:
I did this test as close to scale as I could because I wanted to make sure I wasnt wrong,got to say it passed 100%
Now lets go get a scotch and I will get a salty dog.
 

seedtick

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Jul 22, 2006
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Denham Springs, LA
interesting test but i don't think you've simulated a symetrical seating

When your weight is at the wide spot, it's closer to the center line than when the weight is at the narrow spot. At the narrow spot the weight is at the edge. Now I have a couple of Boston Whalers that let me stand on the edge, but i've never been on a paddleable boat - perogue, bateau or canoe - that let me stand on the edge and not turn over
 

tx river rat

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Feb 23, 2007
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Seed tick
The weights were all set the same distance from the center line .center of boat length and center of a line running down the hull. I didnt show it but I cut the hull symetrical with the same seating arrangement and the light weight rolled it.
Standing on the edge wasnt a option but weight had to be applied to get the roll over.
Ron
 

oldsparkey

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Aug 25, 2003
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seedtick said:
Now I have a couple of Boston Whalers that let me stand on the edge, but i've never been on a paddleable boat - perogue, bateau or canoe - that let me stand on the edge and not turn over
Not sure about the new ones but the older ones when they 1st came out , the Gheenoe made over in Titusville , Fl will let you stand on the edge without flipping. I had one of the 1st models and a friend and I would go frogging in it , we stood up and if needed would put one foot on the edge and lean out to gig a frog. You could paddle it like a canoe or start up the 9.9 Mercury and really cover some distance.
Mine was the narrower one with the narrow transom , not like these wider new ones they are making today.

Chuck.
 

Paddlin'Gator

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Feb 2, 2008
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Tequesta, FL
Long presents the stability issue quite clearly, even if with a bit of an arrogant tone by suggesting that the designers of some very successful boats and ships don't really know what they are doing and don't understand the concepts.
Joe
 

beekeeper

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Mar 4, 2009
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tx river rat said:
The line to the rear will simulate me sitting in an asymetrical boat,the line to the front will do the same but in a symetrical boat ,ok here goes.

I did some playing with some weights


I used half a brick 2 7/8 nuts and a 7/8 socket, the water is just below the top of the foam
now this is asymetrical

next pick I put the brick on the line in front,simulating symmetrical seating arrangement.

Put the brick on the line the same distance from the center




now this is what happened






Just the brick turned it over didnt have the 7/8 nutts are socket on it.
Too hot to fish, so I have been studying. Found this and I have a question. How did moving the weight forward change the hull design from asymmetrical to symmetrical? Didn't you actually only show what happens if the seating position was changed from the wide area to the narrow part of an asymmetrical hull? Did you mean to compare swede form (asymmetrical) to fish form (also asymmetrical), or am I totally confused?

beekeeper
 

tx river rat

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Feb 23, 2007
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The little test was to prove a asymetrical swede form was stabler than an symetrical design
because of width where the most weight was.
Ron
 

a Bald Cypress

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May 7, 2007
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Ron, I agree that sitting at the wider part of a boat will be more stable than if you were sitting in the narowier section. What I am a bit mystified about is why you were putting the weight at the edge of the boat.

Would it not be a better comparison to put the weight in the middle of the boat , as we mostly sit there.

Then with the weight [of the paddler] in the correct position, you could add weight to the edges to check stability.

A boat with no weight sits higher in the water and will be less stable as a result of that. Once the paddler is sitting , or kneeling, in the boat there is an increase in the stability no matter how wide the boat is.

I think that we all agree that the wider the boat = more stability. So sitting in the widest part will be a more stable position if there are no other load factors.

Just how much is gained is still up for questioning.

Which form is easier on the paddler ?.

Will one form carry more weight?.

Will Carol tell Fred the truth about who is the father of the baby?.

How many beers does it take to get Chuck into a boat with a motor on it ?.
 

tx river rat

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Feb 23, 2007
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When you roll a boat you move the weight to the outside by leaning are whatever you have goofe up doing, I cut two of these out one symmetrical and one asymmetrical, from the same point off the center line of the boat placed the weight ,the asymmetrical took a lot more weight before it would roll.
Ron