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Old 05-28-2020, 11:00 AM
 
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I think this is "science"? What could be added - stem and stern - to a kayak that is riding low in the water due to the user's weight nearly exceeding the boat's capacity? The possibilities include spray can foam, pool noodles, extra personal flotation devices (life jackets), Styrofoam, and various inflatable bladders (beach balls, etc.)? The goal isn't merely to displace any water that might be taken on as a result of riding low, but to actually add buoyancy and let the user ride higher in the water (reducing the risk of swamping the boat). I'm honestly not sure, not being "science-y," what substance does what, exactly, or would really work. Thanks!
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Old 05-28-2020, 11:11 AM
 
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The weight of water displaced is based on the weight of the container(kayak in this case) and everything in it. Bladders or anything else inside kayak/boat add weight and would make it ride lower, they are there to keep it afloat if it gets flipped. Adding something on bottom would increase it's ride height but only because you increased the height of the container. Overall the added weight would still make bottom lower.


I wouldn't bother, you'll make it harder to control and harder to paddle through the water. Buy a bigger kayak.

Last edited by thecoalman; 05-28-2020 at 11:29 AM..
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Old 05-28-2020, 11:53 AM
 
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So NOTHING can be done to add buoyancy? That's surprising!
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Old 05-28-2020, 12:15 PM
 
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Well, if we assume the weight of the shell is unchanged and the weight of what's in it is essentially unchanged, we're looking at the dimensions of the shell and the weight of the rider.

If, for example, you weigh 180 lbs and the shell weighs 40 lb, your kayak will displace a volume of water that weighs 220 lb. If for example the shell were just a big rectangular prism, the volume of water would be the surface area at the water line X the depth of the shell into the water. Considering the shape of an actual boat, basically to raise the gunwale height above the water, you need a greater surface area at the water line, or a lighter weight.

There is nothing you can add to your current boat to make it ride higher in the water, unless it is outside the current envelope of the boat. (or it's lighter than air)

You need to either reduce your weight, or you need to increase the total volume of the boat - so, for example, a longer boat.
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Old 05-28-2020, 12:18 PM
 
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By "outside the envelope," do you mean pool noodles strapped to the sides or made into outriggings raise the boater higher out of the water? I am extremely science-challenged.
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Old 05-28-2020, 12:18 PM
 
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When you see boats with "added flotation" such as styrofoam added to the nose and stern, that is so that if the boat gets completely swamped, it won't just sink. The ordinary kayak, which has none of that and is made of blow molded plastic that's more dense than water, if you completely swamp it, will sink. If you were to add closed cell foamed plastic in various places, you could make the total density of the boat less than water, so if it's totally swamped it won't sink to the bottom, and you can hang on to it.
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Old 05-28-2020, 12:20 PM
 
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Where would one find closed cell foam plastic? Is that the spray can foam insulation? And would simply adding either spare PFDs, inflatable bladders, or - again - pool noodles aft and fore achieve the same end (keeping it afloat if swamped, if not raising the boater higher)?
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Old 05-28-2020, 12:25 PM
 
Location: San Diego
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Quote:
Originally Posted by otterhere View Post
Where would one find closed cell foam plastic? Is that the spray can foam insulation? And would simply adding either spare PFDs, inflatable bladders, or - again - pool noodles aft and fore achieve the same end (keeping it afloat if swamped, if not raising the boater higher)?
Foam doesn't make a boat lighter only keeps it from sinking. You need a tandem kayak set up for 1 person. They do make some for heavier people.

https://kayakguru.com/kayaks-big-tall/
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Old 05-28-2020, 12:50 PM
 
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Quote:
Originally Posted by otterhere View Post
By "outside the envelope," do you mean pool noodles strapped to the sides or made into outriggings raise the boater higher out of the water? I am extremely science-challenged.

Yeah, you could do that, but it would destroy the performance and handling of your kayak.


What you need if you want to ride higher in the water is a bigger boat or a lighter self.
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Old 05-28-2020, 05:11 PM
 
41,691 posts, read 43,536,932 times
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Quote:
Originally Posted by otterhere View Post
By "outside the envelope," do you mean pool noodles strapped to the sides or made into outriggings raise the boater higher out of the water? I am extremely science-challenged.

If you did this add them to the sides expanding the width. Adding them to the bottom will significantly change the center of gravity.





This is going to potentially cause problems with tracking and it will be more difficult to paddle through the water.
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