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Old 08-12-2017, 03:10 AM   #1
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Default Is there a reason not to fill my hull with foam

I just finished a transom job on my boat. The boat is a 20' cc with a liner. There is approximately 25 cubic feet of air space between the liner and the hull above the deck.

I am strongly considering filling this area with 2 part foam. I have sealed it up well and have run all the wiring through the space in blue smurf tube.

What are the reasons not to do this?
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Old 08-12-2017, 04:06 AM   #2
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Why would you want to do that? What advantage do you get by filling that space with foam? My experience with foam is not good. I had a 25' with foam under the deck - completely waterlogged, and I have a 32' that used to have a foamed in fuel tank - also completely waterlogged. So what's the advantage of the foam?
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Old 08-12-2017, 04:16 AM   #3
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Advantage is it wont sink.

There are advantages to not putting it in a boat but for me the bottom line is its a huge safety factor.

You may find this thread interesting.
Fish Tank Aluminum Catamaran Loss - The Whole Truth
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Old 08-12-2017, 04:35 AM   #4
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Quote:
Originally Posted by surv View Post
Advantage is it wont sink.

There are advantages to not putting it in a boat but for me the bottom line is its a huge safety factor.

You may find this thread interesting.
Fish Tank Aluminum Catamaran Loss - The Whole Truth
Of course it will sink, if the foam was to get waterlogged. Better to fill it with pool noodles from the dollar store.
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Old 08-12-2017, 04:38 AM   #5
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Foam can always absorb water over time. But it will deaden and hollow sound.
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Old 08-12-2017, 04:41 AM   #6
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Advantages of foam are added stiffness and structure, plus flotation. Disadvantages include the weight of the foam and the tendency of foam to absorb water if left in contact with standing water. If you can plan a way to completly isolate foam from water, then I think the benefits outweigh the downside.

I compare the sound of the Mckee Craft(foam filled) that I owned with other liner boats that were not completly foam filled, Aquasport, Proline, Hydrasports. The Mckee landed with a solid thud. The others allways had a but of a rattle where bits of unsupported fiberglass could vibrate. All of these boats served their purpose. It's just that the foam filled Mckee was effectively a one piece boat.

Now, here's the challenge: Mckee and Whaler use molds and high pressure injection to assure that there are no voids. It's near impossible for the one off builder to do this, so there are likely to be voids, and voids collect water.
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Old 08-12-2017, 04:55 AM   #7
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Those 2 part foams are now closed cell and absorb water much less than the old stuff waterlogged under the deck . Its used by all boat builders to this day , dont think there all wrong .Buoyancy , sound deadning and structural strength all improve . It says on the package that long term exposure to water can cause absorbsion so there is no concrete correct answer . I put it under my deck and now is the time to use it , it works much better in the heat than cold of winter where you need to buy twice as much . The cheapest I found was from Jamestown Distributors . Hope this is some help
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Old 08-12-2017, 04:56 AM   #8
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Lol did u just compare a McKee to a proline? Ay no
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Old 08-12-2017, 05:03 AM   #9
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If you do choose the foam route, be very mindful of expansion.
It can bulge things a little or worse rip joints apart if the cavity is large enough.
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Old 08-12-2017, 05:19 AM   #10
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Pros. Flotation

Cons, possibility to absorb water.
Access to that area next time you need to fix, add, repair something.
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Old 08-12-2017, 02:47 PM   #11
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I got the foam from us composites. It is sitting in my garage.
I have been chicken to start pouring yet.

I still want to seal the liner to hull joint better before I start foaming. I plan to take the rub rail loose and go to town on the seam with 5200 and then reattach the rub rail. Is there a better way?
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Old 08-12-2017, 03:07 PM   #12
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Pro's
Strength
Flotation

Con's
Can hold water after a long time.
Usually gets blamed for water retention problems, but is just another innocent victim.
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Old 08-12-2017, 03:17 PM   #13
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Default foam

This is what bounces around in my head when the foam subject comes up. I would rather not, but it is nice to have if you need it....

Overturned boat on the Bahama Bank

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Boat Sinks at Moxy Rig


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I have also cored a piece of each section in my project boat and NONE of them are wet. I have gone all the way down to the glass in each compartment and found no moisture at all.

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Note the "dirt" in the boat that is a result of massive termite damage. EVERY piece of wood in the boat is gone.....
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Old 08-12-2017, 03:47 PM   #14
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Quote:
Originally Posted by wangotango321 View Post
Lol did u just compare a McKee to a proline? Ay no
Not really, unless the comparison was boats that I've owned. I said that my Mckee had a solid ride and solid sound when it landed off a wave which I atribute to the foam. The others did not.

If the post was asking me to rank my boats based on overall quality, ride, fit, etc, the proline would be at the bottom, but that was not the intent of my post.
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Old 08-12-2017, 04:14 PM   #15
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If you take precautions to keep the foam dry I would do it. In a swamping I would prefer to have the hull bobbing nearby rather than just me and a pfd floating in a big ocean.

Shame so many boats were made with poor designs and the foam would eventually waterlog. Owners are the cause often also, floor acess plates need to be checked for seal at the lid and under the rim as well.
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Old 08-12-2017, 04:46 PM   #16
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Default read the coast guard recomendatios for floatation

foam is always going to soak water end of story !!,
Pool noodles are good !!
The placement of any kind of flotation INSIDE A BOAT is critical !!
In the bottom of the hull is the worst place of all because it make the boat float upside down the hull sides YES !!

HAVE YOU EVER TRIED TO HOLDING ONTO A UPSIDE DOWN SLIPPERY HULL IN THE SEA WHILE ITS BOUNCING ABOUT WITH THE WAVES ??? its impossible so if it floats the right way up you can get inside !
Boats are much easier to see than people floating in the water ! boats are seen from the air but a person iTs close to impossible
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Old 08-12-2017, 05:17 PM   #17
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Foam adds unnecessary weight, expansion can also cause issues, it will hold water over time. A 20ft cc aint sinking where you will need to hold on to if for days to survive. Skip the foam. Look at the responses, none are good justification for this boat. I say again-- skip the foam.
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Old 08-12-2017, 05:23 PM   #18
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I refoamed my boat when I did the decks last year. I've mentioned this boat quite a few times here, but she's had a hard life: commercial transport for a marine construction company before I got her. Brutal use in rough seas up north here. Built in '81, decks were raw plywood on the bottom and polyester fibreglass on top. The construction guys plumbed in a bus heater just by punching a hole in the deck where it was necessary and on that side I took out around 12 cu ft of foam that weighed maybe 250lbs.

On the other side, where no holes were specifically drilled, the foam was dry. The boat is nearly 40 years old, most of which were daily commercial use in rough seas in one of the rainiest places on earth, and the foam, where not specifically, stupidly exposed to lots of water, was almost perfectly dry. I dug out lots of it to be sure; it was fine. Build the boat well and it's pretty watertight, which makes sense, if you think about it.

Why refoam instead of just leave it full of air? Because where I am, it's totally normal to see tidal swings of 12-15 feet, and logging is a major industry. I know plenty of guys who've run into logs here. One lost the entire lower off his merc outboard hitting a submerged log, for example.

If you think foam is stupid, you've probably never seen a hull with a big hole punched in it miles offshore with help hours away. That happened to a guy I know. He idled back in under his own power.

Tough to climb on a slippery hull? Absolutely, although people do it in severe conditions. There have been a few sailors rescued in the southern ocean off Antartica clinging to inverted hulls, so it's doable, even if it's hard. Most people end up clinging to rudders or engines. But I'm sure it's tough.

But is it tougher to survive in 40 degree water for a couple of hours waiting for help? Yeah, probably. There's always life rafts, of course. But every redundancy I can add is preferable to me.
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Old 08-12-2017, 05:30 PM   #19
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Quote:
Originally Posted by barrell View Post
Fill it with pool noodles from the dollar store. Of course it will sink if the foam was to get waterlogged.
Quote:
Originally Posted by tunnles View Post
foam is always going to soak water end of story !!,
Pool noodles are good !!
The placement of any kind of flotation INSIDE A BOAT is critical !!
In the bottom of the hull is the worst place of all because it make the boat float upside down the hull sides YES !!

HAVE YOU EVER TRIED TO HOLDING ONTO A UPSIDE DOWN SLIPPERY HULL IN THE SEA WHILE ITS BOUNCING ABOUT WITH THE WAVES ??? its impossible so if it floats the right way up you can get inside !
Boats are much easier to see than people floating in the water ! boats are seen from the air but a person iTs close to impossible

How could pool noodles possibly be better foam than marine grade two part polyurethane foam? Have you ever poured gasoline on a pool noodle?
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Old 08-12-2017, 05:39 PM   #20
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Quote:
Originally Posted by surv View Post
How could pool noodles possibly be better foam than marine grade two part polyurethane foam? Have you ever poured gasoline on a pool noodle?
Because Tunnles knows everything, just ask him
Or ask the guys over at Scream and fly .com.
Most members over there have him on ignore.
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