How much foam?

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acwd

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I got 2 sheet 4ft x 8 ft 2 inches thick in the boat. Its a 16 ft vee. Got no more places to put foam in. Is that enough? some is better than none.

Steve
 
You did good! That's 11 cubic feet of foam. and if there isn't anymore room... that's all your boat will hold.

The 11 cubic feet of foam is about 700 lbs. of floatation.
 
The purpose of foam is not to provide buoyancy, as that comes from displacement. Its main purpose is to fill voids in the boat, so that if it takes on water, these spaces are occupied with foam, which prevents them from filling with water, causing the boat to take on more weight and becoming unstable to the point that it goes turn-turtle.

But again, some foam is better than none, so, anywhere you are able to put it, do so.
 
PSG-1 said:
The purpose of foam is not to provide buoyancy, as that comes from displacement. Its main purpose is to fill voids in the boat, so that if it takes on water, these spaces are occupied with foam, which prevents them from filling with water, causing the boat to take on more weight and becoming unstable to the point that it goes turn-turtle.

But again, some foam is better than none, so, anywhere you are able to put it, do so.

So when I fall in the water with a PFD on I just float because it's displacing water around me that could fill my voids and make me heavier?
 
LOL, of course not. People do not displace water. Now, depending on the body's fat content, a person with more body fat will have more natural buoyancy than a person with no body fat. But still not like a PFD.

Yes, foam is buoyant. But, adding or removing foam will not make a boat sit any higher or lower in the water, again, because the buoyancy of the vessel is because of its displacement.

With something like a floating dock, adding or removing foam will most definitely affect the buoyancy, because the floating dock is an open structure, it's not a hull creating displacement.
 
PSG-1 said:
LOL, of course not. People do not displace water. Now, depending on the body's fat content, a person with more body fat will have more natural buoyancy than a person with no body fat. But still not like a PFD.

Yes, foam is buoyant. But, adding or removing foam will not make a boat sit any higher or lower in the water, again, because the buoyancy of the vessel is because of its displacement.

With something like a floating dock, adding or removing foam will most definitely affect the buoyancy, because the floating dock is an open structure, it's not a hull creating displacement.

Fill your bath tub up to the very top and then climb in and see how much water you don't displace spill out on the floor.

Foam in a boat is called floatation foam for a very good reason, if all it was used for was to fill voids they'd call it void foam and not floatation foam.

No, foam doesn't make a boat float higher in the water when there's no water in the boat... but boy it sure does a good job when water enters the boat. Foam doesn't make a boat filled with water float because there are less voids in the boat to be filled with water, it makes a boat float because it has air entrapped in it and it's lighter than water... thus the term floatation foam.
 
I would not necessarily say that "some foam is better than nothing"
Either you have enough foam to keep your boat from sinking or you don't. I believe the placement of the foam in a boat greatly influences if the boat will float level too. You may very well have enough foam if the previous poster is correct in the 700 lbs of flotation statement. Just my 2 cents, may not be worth that though.
Tim
 
You should be good with 2 sheets of foam. I calculated that I would need about 1.5 sheets of the 2inch stuff to keep my 14ft boat with a 35hp motor from sinking... and I calculated that with I think 30% over what I needed. (I like overkill)

Flotation foam is a bit of a misleading term. If your boat becomes 100% filled with water, (such as capsizing)--the foam is designed to give your boat enough buoyancy to keep it from sinking--not necessarily keeping it floating. It does this because it displaces more water then combined specific weight of the materials which comprise the boat (IE wood; aluminum; steel; etc.).

Since foam displaces a lot of water, and weighs considerably less then the same volume of water--it floats--and is a good candidate for added flotation since it does not absorb water or decompose quickly. Other materials which could serve this purpose are scrap pool toys (such as fun noodles) or even empty plastic soda bottles.
 
I think you're good to go. The foam won't keep you afloat as such, but will prevent you from sinking entirely. I believe the rule of thumb is that 1 cu. ft. of foam will float 60lbs. and a pool noodle will float 100 lbs.
 
kfa4303 said:
I think you're good to go. The foam won't keep you afloat as such, but will prevent you from sinking entirely. I believe the rule of thumb is that 1 cu. ft. of foam will float 60lbs. and a pool noodle will float 100 lbs.

It's al relative...

Pool Noodle's very in length, width, and some have holes through the center... and when they talk about floating 100lbs--it is probably in reverence to 100lbs of human. While a 100lbs chunk of lead might still sink like a stone.

If you really want to know for sure-- google the term 'Specific Gravity' and 'Relative Density'. There are several formula's and charts which tell you the information you need to know in order to determine exactly how much of given materials you need to get to neutral buoyancy. If you know the relative density of all the materials which comprise your boat, you can figure out how much negative buoyancy you need to float. I got a rough idea, and added 30-40% to make sure I covered my butt--and I know I'm good to go. And if you are going to do this--don't you want to be 100% you used enough?
 
Enough and not enough foam goes like this:

You attach an unweighted bobber to your line and cast it out, the bobber will lay sideways on the water.

Reel in and add a splitshot to your line below the bobber and cast out, now your bobber sits upright in the water.

Reel in and add another splitshot and cast out, now your bobber is sitting lower in the water.

Reel in and add another splitshot and cast out, now your bobber just barely floats with just the top tip above water.

Reel in and add another splitshot and cast out, now your bobber sinks.

This same scenario is true with floatation foam in a boat. If you just have minimal foam your boat will sink until the tops of your gunwales are just a couple inches above water.

If you have an abundance of floatation foam your boat may only sink until your feet get wet... maybe not even that much.
 
jigngrub, I think you're off a little bit here and potentially misleading others.

The foam only works if it is displacing water. In your scenario above, this would only be true if the "abundance of foam" were able to displace enough water relative to the weight of the rest of the boat above one's feet. Meaning if the rest of your abundance were above the waterline, then that's just more weight on the foam that's displacing the water below the boater's ankles or whatever.

PSG-1 knows his stuff. I've been following him for about a decade now on this site and others, and plus, this should just be common sense.

Your life preserver scenario makes absolutely no sense. If you've ever totally relaxed in a pool you know that it only takes your lung capacity to keep you afloat. Even the least expensive CG approved orange ones are designed to keep your head above water, in a position so that you can breathe air, as most of the rest of your body is nearly neutrally buoyant. In other words, your body is displacing the rest of the water necessary for flotation.

I've mentioned in the past that my recent discovery of inflatable wine bladders is probably the best solution going, unless in the case that foam is there for structural rigidity and is encapsulated in epoxy. I have poured my share of two part foam in boats. I don't care what anybody says about any of this, I know that foam is compressible. If it is compressed (if you step on it under the floor), your little air bubbles are busted and water will get in and waterlog over time. PERIOD.

I can jump up and down on a wine bladder and it will not pop. It can also be stuffed into areas and epoxied in place without much trouble, and a hell of a lot cheaper and more effective than any non-structural foam product. You can also easily deflate them to gain access to these areas for wiring and accessories and just reinflate them. Plus if you want to remove them, it's just popping a balloon and pulling them out. No stinky mushy waterlogged business. They weigh next to nothing. I can't remember the exact figures, but at one point, calculated that a single fully inflated Bota Box wine bladder would support somewhere near 80lbs of buoyancy. Keep in mind that there's probably a lot of positive buoyancy materials already in your boat and it won't take that many of these bags to float your boat.

***Fill only to about 2/3rds to allow for heat expansion or fill them to 3/4ths on the hottest day.
 
jladdsmith said:
jigngrub, I think you're off a little bit here and potentially misleading others.

The foam only works if it is displacing water. In your scenario above, this would only be true if the "abundance of foam" were able to displace enough water relative to the weight of the rest of the boat above one's feet. Meaning if the rest of your abundance were above the waterline, then that's just more weight on the foam that's displacing the water below the boater's ankles or whatever.

PSG-1 knows his stuff. I've been following him for about a decade now on this site and others, and plus, this should just be common sense.

Your life preserver scenario makes absolutely no sense.

I've mentioned in the past that my recent discovery of inflatable wine bladders is probably the best solution going, unless in the case that foam is there for structural rigidity and is encapsulated in epoxy. I have poured my share of two part foam in boats. I don't care what anybody says about any of this, I know that foam is compressible. If it is compressed (if you step on it under the floor), your little air bubbles are busted and water will get in and waterlog over time. PERIOD.

I can jump up and down on a wine bladder and it will not pop. It can also be stuffed into areas and epoxied in place without much trouble, and a hell of a lot cheaper and more effective than any non-structural foam product. You can also easily deflate them to gain access to these areas for wiring and accessories and just reinflate them. Plus if you want to remove them, it's just popping a balloon and pulling them out. No stinky mushy waterlogged business. They weigh next to nothing.

***Fill only to about 2/3rds to allow for heat expansion or fill them to 3/4ths on the hottest day.

Consider the following:

The waterline of a boat rises as the boat sinks.

Floatation foam is a PFD for your boat.

Your floatation foam will only become waterlogged, stinky, and mushy if you neglect your boat.

There's a reason behind the law that requires all new boats to have built in floatation... and it's a very good reason! There's also a reason that boat manufacturers use the more expensive expanding foam instead of wine bladders... btw? Are your wine bladders USCG approved??? Expanding urethane foam is... and for a good reason.

It sounds like you've been drinking too much wine.
 
The wine bladders were collected from "the ex" over time.

My points are presented. I would never buy a new boat with wine bladders epoxied under the decks. I would, however, replace neglected hulls having saturated foam with them without hesitation as it is a better solution for non structural applications.

It seems that your main charge here is to say that the OP neglected his boat and that he made the bed he is laying in, while you are the perfect boat owner. If so, bravo! =D>
 
jladdsmith said:
It seems that your main charge here is to say that the OP neglected his boat and that he made the bed he is laying in, while you are the perfect boat owner. If so, bravo! =D>

The OP said nothing about removing saturated foam to replace it with the 2 EPS sheets, for all we know he could've bought the boat without foam in it and he's trying to do the right thing by installing as much as he can.

I am not the perfect boat owner... but I'm working on it. :wink:
 
You're absolutely right.

My opinion on your responses regarding foam was combined from this thread and https://www.tinboats.net/forum/viewtopic.php?f=3&t=25102

Another useful tip to the OP's of these threads would be that:

Instead of using two part urethane foam (which is a huge mess and must be done in batches), you can also use sheets with 3m Super 77 adhesive in between layers. A hot wire knife can be made for next to nothing to form the new 'billets' as needed with little mess (like from rasping or sanding) to deal with in the shop. Youtube that for a better explanation.

Good luck guys, just get something in there.
 
Keeping a person afloat and keeping a boat from sinking are two totally different scenario's. A person is comprised of something like 70% water, while fat weighs less then water and muscle weighs slightly more. This is why when I try and float in a pool, my legs sink and my torso floats--as my legs have a much lower percentage of fat then my torso does--also, lugs filled with air help.

A boat on the other hand is comprised of various materials, almost all of them are heavier then water in the same given volume. I'm a big fella, currently tipping the scales around $330lbs. My boat and motor combined weigh about the same weight--outside of the water. I am about neutrally buoyant when completely submerged in water (i.e. completely under water, not floating on top of the surface). On the other hand, the boat would sink like a rock without any flotation.

The denser and heavier an object is vs. its given volume relative to water is what determines whether it floats or not. Styrofoam by comparison, is extremely light given a relative volume. So by adding Styrofoam to a boat, what you are essentially doing is increasing the volume of the boat considerably without increasing the weight. Now when completely submerged, this added volume in your boat will displace more water. The goal is to simply add enough volume of foam to your boat to displace enough water to keep the total mass of your boat lighter then the same volume of water. This will keep your boat buoyant, the more buoyant, the more of your boat will stick out of the water when completely submerged. Without the foam, the compartments will just fill with water, and the boat will sink--since water does not weigh less then water. (but foam does!)

Got it? No? Its ok... once you get it, you'll go 'ohhh yeaaaah, that makes sense'. Again... reference 'specific gravity'.

Or, click below: Fresh Water is 1.0 Anything less then 1.0 will float, anything over 1.0 will sink. The bigger the number, the more it weighs in water.
https://www.reade.com/Particle_Briefings/spec_gra2.html
 
Bigkat650 said:
I'm a big fella, currently tipping the scales around $330lbs.

Dollars and Pounds? Does that mean you are 'worth your weight in gold?' :shock:

















I know, bad joke. #-o
 
Bigkat650 said:
Keeping a person afloat and keeping a boat from sinking are two totally different scenario's. A person is comprised of something like 70% water, while fat weighs less then water and muscle weighs slightly more. This is why when I try and float in a pool, my legs sink and my torso floats--as my legs have a much lower percentage of fat then my torso does--also, lugs filled with air help.

There are many different variables and scenarios.

Sure, anyone can float in a bathing suit. But put some heavy winter boots on, layered clothing, and a pair of coveralls and see how well you can float... probably about as well as a boat without any floatation foam.

Got it? No? Its ok... once you get it, you'll go 'ohhh yeaaaah, that makes sense'. Again... reference 'specific gravity'.

Floatation is floatation whether it's a PFD or foam in your boat, and I'm pretty sure that's why they call them Personal Floatation Devices and floatation foam.

PFDs and floatation foam are a necessity for safe boating, and safe boating is not overrated.

I'll bet this guy was wishing he could float, and I'll be he was wishing he wore his PFD like the law requires.
https://articles.chicagotribune.com/2012-04-17/news/ct-met-kayak-swan-death-20120417_1_swans-raymond-hensley-complex-retention-pond
 

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