Foam Question

[LgMouthGambler]

I know foam is good for keeping the boat afloat if it turns over, but does it really help to have foam in the boat otherwise? I ask because I see all the people adding foam to their boats and think that as long as there are no leaks in the boat, you really don't need it. As long as water is not physically touching the foam the outside of the boat keeps it floating, doesn't it? My Jon has pretty much next to nothing for foam in it and it seems to float just fine.

 

[earl60446]

"I know foam is good for keeping the boat afloat if it turns over, but does it really help to have foam in the boat otherwise?"
Yes

" I ask because I see all the people adding foam to their boats and think that as long as there are no leaks in the boat, you really don't need it."
Wrong, You need it when water is in the boat.

"As long as water is not physically touching the foam the outside of the boat keeps it floating, doesn't it? My Jon has pretty much next to nothing for foam in it and it seems to float just fine."
What if you get swamped, many ways for this to happen.

Flotation foam can do two things for a boat when installed properly.
1. It can add rigidity to the hull and deck
2. It keeps the boat from sinking when swamped with water

Tim

 

[onthewater102]

earl60446 » 30 Jun 2014, 13:47[/url]"]...Flotation foam can do two things for a boat when installed properly.
1. It can add rigidity to the hull and deck
2. It keeps the boat from sinking when swamped with water
...

That's it.

Flotation foam is closed-cell so that it doesn't absorb water quickly and will retain its flotation for an extended period of time - however, left submerged it will eventually take on water and become heavy.

 

[KMixson]

What keeps your boat floating is water displacement. As your boat sits in the water it is displacing water. When the amount of water displaced equals the weight of the boat it will float at that level. Foam in the boat adds weight which means it will sit lower in the water but not by much as foam is pretty light. It actually hurts (although not much) while the inside of the boat is dry due to extra weight. Now if you capsize the boat the foam will displace more water than a boat with no foam which will help keep the foamed boat afloat. If you took a bare aluminum boat and filled it with water it will go to the bottom because the water that it is displacing is less than the weight of the boat. I hope I didn't confuse you too much with my scenario. I think I got it right. lol

 

[LgMouthGambler]

OK, I got it now. Was just making sure of what some were using it for. Its a good thing I have a powerful bilge pump that displaces water fast. I have had boats pass me on plane, and fortunately I can say that my boat is very stable in big waves. Thanks for every ones part in the explanation.

 

[acabtp]

LgMouthGambler » Yesterday, 16:17[/url]"]Its a good thing I have a powerful bilge pump that displaces water fast.

just so long as you realize that bilge pump is in no way a substitution or replacement for flotation foam.

 

[earl60446]

acabtp » Today, 07:42[/url]"]

LgMouthGambler » Yesterday, 16:17[/url]"]Its a good thing I have a powerful bilge pump that displaces water fast.

just so long as you realize that bilge pump is in no way a substitution or replacement for flotation foam.

Exactly, if your boat gets enough water in it, it is going to the bottom (no matter how big your bilge pump is). I am assuming (from your comments) there is not enough foam in it to keep it afloat.
Tim

 

[onthewater102]

Water weighs approximately 62.5 lbs/ cu.ft. Marine urethane foam (hard closed cell foam typically used by boat manufacturers) weighs ~2 lbs/ cu.ft. so if totally submerged 1 cu.ft. of foam will support approximately 60 lbs of weight.

The volume of your boat below the water line is the amount of water it displaces. The total volume of your boat is the maximum displacement of your boat. Typically the rated capacity is limited to 20% of this maximum value. This is done so that there is enough of the boat's gunwales above the water line to allow the boat some instability without taking on water.

But none of this nerdy math is meant to imply that a good pump negates the need for foam...I've got way more foam in my boat than I need and that's OK by me - should some @$$ hat yuppie buzz and swamp me my motor's powerhead should remain out of the water.