Flotation under floorboards----why there..??

[RichBKK]

Big Question:

Why does everyone keep saying to install flotation (closed cell foam or noodles) under the floorboards of their aluminum boats when rebuilding..?? I don't get it..

With flotation under the floorboard / decking of an aluminum boat, heaven forbid if a "breaker" (or 4) comes over the bow and one is swamped, (read: high seas, offshore, huge winds, etc.),----wouldn't that vessel have the tendency to capsize due to the flotation in the bottom of the boat..??

The good: Hey, shes capsized and still floating.. Something there to hang onto, or better yet, something to climb upon..

The bad: Hey, my vessel has flipped upside down, I'm in the drink and hopefully I can hang onto her and God willing, I can climb onto her---till help arrives..

Why not install the flotation along the interior gunwales..?? If ones vessel was to be swamped and "go down", wouldn't your boat still be "right-side up", bobbing at the surface, only full of water..??

I'd rather be "inside my boat swimming" than outside of my capsized hull, "in the food chain", trying to hang on or climb on..

I would think one would have much better odds of survival, rescue and possibly getting your vessel bailed out and floating again if the boat is still "right-side up" (due to gunwales, bow to stern, filled with flotation), versus hanging on / climbing on to a flipped but floating boat..

 

[matt167]

Re: Flotation under floorboards----why there..??

That has been done and is acceptable. Many people just want the gunwhales for storage.

 

[jigngrub]

Re: Flotation under floorboards----why there..??

Big Question:

Why does everyone keep saying to install flotation (closed cell foam or noodles) under the floorboards of their aluminum boats when rebuilding..?? I don't get it..

With flotation under the floorboard / decking of an aluminum boat, heaven forbid if a "breaker" (or 4) comes over the bow and one is swamped, (read: high seas, offshore, huge winds, etc.),----wouldn't that vessel have the tendency to capsize due to the flotation in the bottom of the boat..??

The good: Hey, shes capsized and still floating.. Something there to hang onto, or better yet, something to climb upon..

The bad: Hey, my vessel has flipped upside down, I'm in the drink and hopefully I can hang onto her and God willing, I can climb onto her---till help arrives..

Why not install the flotation along the interior gunwales..?? If ones vessel was to be swamped and "go down", wouldn't your boat still be "right-side up", bobbing at the surface, only full of water..??

I'd rather be "inside my boat swimming" than outside of my capsized hull, "in the food chain", trying to hang on or climb on..

I would think one would have much better odds of survival, rescue and possibly getting your vessel bailed out and floating again if the boat is still "right-side up" (due to gunwales, bow to stern, filled with flotation), versus hanging on / climbing on to a flipped but floating boat..

There's a thing about that:

There's a lot of boats that have floatation in the gunwales and above deck as well as below deck.

Magnumdeke installed foan in his gunwales:

This is a good design and also helps strengthen the sidewalls and makes the boat quieter.

Instead of swimming inside your boat, how about no getting wet at all like in this vid:
Lund Boat Floatation Video - YouTube
My boat actually floats better than that Lund when filled with water.

There are a few considerations that most folks on this site either ignore when installing floatation because they either don't want to spend the money and take the time or they just don't know/understand.

1. More foam is better, having an over abundunce of floatation is much better than not having quite enough. Can't say how many times I've seen folks skimp on floatation because they "don't have the money" and they're "on a budget"... but they'll have plenty of money to fill the boat up with gas and run it around on the water when it's finished.

2. Using the best type of foam:
The best floatation is the 2 part urethane expanding foam, it's USCG approved while sheet foam and noodles are not. The urethane foam bonds itself to the hull and doesn't rely on decking fasteners to keep it in place like the sheet and noodle foam.

3. Positive bilge and deck drainage:
Some people may ask "what does this have to do with floatation?", and the answer is quite a bit.

I've seen quite a few on here go through meticulous pains to seal their deck off from the bilge, ignoring to install a deck to bilge drain and caulking all the way around where the decking meets the hull... and packing their bilge so full of foam that theres no room for any water or drainage.

You want a deck to bilge drain or deck to through hull (transom) drain in your boat to get rid of any water that gets on the deck. A deck to bilge drain with enough room for water to accumulate along the keel for ballast is best when you take water over the bow/transom or take on large amounts of storm water quickly.

Room in the bilge for water to ballast along the keel will reduce chances of capsize with a deck to bilge drain. With no drain and a sealed deck the interior of your boat becomes a huge bath tub and the first time it rocks from side to side over she'll go and capsize.

 

[Yacht Dr.]

Re: Flotation under floorboards----why there..??

Big Question:

Why does everyone keep saying to install flotation (closed cell foam or noodles) under the floorboards of their aluminum boats when rebuilding..?? I don't get it..

With flotation under the floorboard / decking of an aluminum boat, heaven forbid if a "breaker" (or 4) comes over the bow and one is swamped, (read: high seas, offshore, huge winds, etc.),----wouldn't that vessel have the tendency to capsize due to the flotation in the bottom of the boat..??

The good: Hey, shes capsized and still floating.. Something there to hang onto, or better yet, something to climb upon..

The bad: Hey, my vessel has flipped upside down, I'm in the drink and hopefully I can hang onto her and God willing, I can climb onto her---till help arrives..

Why not install the flotation along the interior gunwales..?? If ones vessel was to be swamped and "go down", wouldn't your boat still be "right-side up", bobbing at the surface, only full of water..??

I'd rather be "inside my boat swimming" than outside of my capsized hull, "in the food chain", trying to hang on or climb on..

I would think one would have much better odds of survival, rescue and possibly getting your vessel bailed out and floating again if the boat is still "right-side up" (due to gunwales, bow to stern, filled with flotation), versus hanging on / climbing on to a flipped but floating boat..

You just have to be sure that you have enough foam or noodles in there to Float the boat with all the gear onboard.

Some builds need the foam in bilge for structural integrity.

YD.

 

[jasoutside]

Re: Flotation under floorboards----why there..??

You make good points for sure, but here's the thing:

Big Question:

Why does everyone keep saying to install flotation (closed cell foam or noodles) under the floorboards of their aluminum boats when rebuilding..?? I don't get it..

Many of these boats simply don't have the available space under the gunwales to fit enough foam to float the boat. So, sub deck is a great spot to jam displacement.

I know once I run all the plumbing, electrical, controls, steering cable, yadayada under that starboard side gunwale, the available space is pretty small.

 

[Watermann]

Re: Flotation under floorboards----why there..??

Not sure this is a legit post or just a forum flame but just in case... I have an aluminum boat with no enclosed gunwales the only place for foam is under the deck. It won't sink but not because of the foam, but because I don't have much fun fighting monster waves in bad weather and am long gone from the water before it gets so bad that could happen. Yeah I know "what if your caught out", no that won't happen either because I look at the weather forecast and plan accordingly.

What good does it do relying on foam just in the gunwales if it's not enough to keep the boat up? So your in a kiddie pool of water, no it doesn't work like that. The water will go to the stern because that's where most the weight is and the boat is going to sink as those monster waves that just swamped you aren't going to stop just because they got you.

 

[Bob_VT]

Re: Flotation under floorboards----why there..??

Not sure this is a legit post or just a forum flame but just in case...

Well, the original poster is talking about a 14' aluminum boat that he has done transom modifications and applied gluvit...... yup "If it looks like a duck, walks like a duck, and quacks like a duck, it's probably a duck." I suspect you are right.

 

[RichBKK]

Re: Flotation under floorboards----why there..??

Just to fill in some of the gaps.. I think it's agreed by all that any flotation, regardless of where it's inserted, wedged, packed in, is a very good thing.. One can never have enough aboard, especially during "times of crisis"..

With that said, my original post was questioning whether flotation, only underdeck, would still put you in the drink if swamped.. Why not load up the gunwales, would the boat not have much less chance of flipping..?? Jigngrub's post was most informative and photo posted really was appreciated.. Question concerning his recommendation.. Using the USCG approved, 2 part Urethane foam, I'm under the impression from posts all over the internet and here on iboats that foam such as that, when in direct contact with aluminum, the urethane will ultimately "eat aluminum".. If so, does it not have to be entirely enclosed and if so, enclosed in what..??

Concerning bilge drainage, I'm good there.. 2 teak floorboards running the length of the boat, stopping at the last rib, 2 feet from the transom.. All water runs thru entire boat easily.. My 8 foot casting and sleeping deck is divided into 3 "lids".. It isn't "sealed" to the gunwales nor are the lids watertight.. Beneath all 3 lids is storage area.. Anything needing to be kept waterproof (i.e.: sleeping bag and sleeping pad, food, handheld spotlight, handheld GPS and VHF radio, batterys, etc.), is stored in drybags, kept beneath deck, easily accessable..

Like Waterman, I also don't have gunwales to insert foam into.. I'm customizing and designing ways to get foam into this little boat, along the gunwales beneath the casting / sleeping deck, as well as in both quarters of the stern..

Unlike Waterman, numerous times thru out the year, I'm on the boat for 6 to 19 days at a stretch.. Traveling long distances.. Not always inland following the ICW, but offshore in the Gulf.. That's where the big fish are, that's where the adventure starts..That's where one is able to "cover some territory" as quickly as possible.. There's no "No Wake Manatee Zone, Idle Speed Only" signs in the Gulf.. Our weather forecasts here are for 7 to 10 days at a stretch but--- are only "somewhat accurate" for 2 to 3 days.. The daily NOAA reports may say 2 to 4 foot seas, westerly winds, with 4 seconds between swells up to 50 miles offshore.. But, try running off the Gulf into a pass or in thru jetties on that 2 to 4 foot sea that's slamming into a strong outgoing tide with stong offshore winds (the wind has switched, out of the east at sunset).. Those 2 to 4 foot offshores will jump to 5 to 8 feet.. Weather patterns off the northern coast of Africa highly influence the weather patterns in the Carribean very fast thru out the summer.. And spring and fall weather forecasts of fronts coming out of the northeast, Great Lakes, mid-west and Canada can be ridiculously off.. The weather man may say the cold front hits "this coming weekend here in S.W. Florida" but, one gets slammed Weds. afternoon..

My little boat has a bit more modification to it than just transom work and Glu-Vit.. 8 foot casting / sleeping deck with under-deck storage, enough space for 3, 6 gallon gas tanks and 1, 3 gallon gas tank.. 3 gallons of water.. Anchor bag with 2 anchors, chain and rode for both.. Dry bags filled with sleeping bag, sleeping pads, food, rain suit, foulies, 2 sets of fleece layers.. 1 full wet suit and 1 spring suit.. Mask, snorkel and 1 fin.. Rod holders for 4 rods, 2 tackle bags live strapped on the deck when underway..

1 self designed custom 8 foot silnylon emergency / sleeping tent and custom mosquitoe net with gunwale tent poles for sleeping aboard.. Custom fit bimini top and boot.. Custom transom and bow welded reinforcements and decking support.. Boat seat with custom slider for shifting one's weight for ballast, port to starboard.. And removable "mini transom" for 2hp. kicker (only taken aboard during trips to, thru or around the 10,000 Island / Everglade National Park / Cape Sable region)..

I always sleep aboard during these adventures and sleep surprisingly well.. I don't see the point of running the risk of having the boat stolen or anchor(s) pulling in the middle of the night while I'm camping onshore.. And sleeping aboard, I can sleep anywhere for free.. One needs a camping permit in the Everglades and you can only camp on selected islands anywhere on either coast of Florida..Tent and netting work flawlessly and I've been caught in some very heavy downpours with high winds..

Ah, so back to the original post concerning gunwale flotation.. I was back at the welders yesterday afternoon.. Found a couple of more areas in the bow, along the gunwales to fit foam into.. I'll be losing some storage space naturally, but "in the event of"--- I think it's best to leave some gear and food behind at the dock, for the piece of mind of knowing I've done everything possible to stay afloat.. Right-side up.. "Where there's a will, there's a way"..

 

[bob johnson]

Re: Flotation under floorboards----why there..??

well if it were just under the floor, it MIGHT flip the boat when capsized....but at least the boat wont sink to the bottom leaving you treading water.....at least the boat would remain at the surface for the occupants to cling to and maybe even climb out of the water to sit on!!!..........it is not a planned approach, getting swamped...it is a disaster.....and at the least it helps some having foam to float the rig...wether right side up or not. bob

 

[RichBKK]

Re: Flotation under floorboards----why there..??

Agreed.. No one plans on getting swamped and having to cling, climb or tread water.. I just think it's best to "be prepared'.. Better safe than sorry..

A large percentage of the 10,000 Islands, pretty much all of the Everglades and a good stretch of the Cape Sable region there's no cell phone connection.. They don't work down there.. I've heard that even VHF can be somewhat sketchy depending on location, "line of sight", atmospheric conditions, etc. down in that so called aquatic "no mans land".. DSC is your best bet if (and that's a big if, especially in the off season) there's other boats, ships within "ear-shot" and their DSC equipt radio is on..

One thing I have found thru pretty much every facet of life----"take care of your gear (read: boat, outboard, car, job, lawnmower, etc., etc.) and your gear takes care of you.."

 

[Watermann]

Re: Flotation under floorboards----why there..??

Good Lord you take a 14' aluminum out in the gulf and for up to 19 days? Biggest problem here where I boat is the Columbia River when the wind blows against the current it turns dangerous and I have a fairly deep V 16 footer. Although surviving in the cold water for any length of time if overboard is marginal even during the summer months. All of the dams blow the water from the bottom of the reservoir above them through the turbines.

You should post up some pics of your boat.

 

[RichBKK]

Re: Flotation under floorboards----why there..??

Yes sir.. Considering I was born, raised and live in Sarasota, Fl., the Gulf is the only place to be, as far as I'm concerned.. It's right "in my back yard", so to speak.. A lifetime since childhood, spent fishing inshore on the flats, off the Intercoastal Waterway.. Catching trout, redfish, snook, mangrove snapper, small tarpon.. Fun and I'm not taking anything away from it but----.. Small fish, boat traffic, boat wakes, "Slow--Manatee Zones".. "No Wake" zones, jets, small plane and helicopters overhead----ahhh jeez----forget it.. Besides no peace and quiet, no adventure, no "new, uncharted territory"---the water inshore looks like septic tank water.. Polluted, you know..??

But get 3 to 12 miles offshore----now we're talking..!! Water "blues up".. Turquoise, azure, indigo.. Really clears up, too.. You can see Bonita, Kings, Mackeral, Cobia, Amber Jack rippin' up bait pods 10 to 20 feet below the surface.. And when they push'em to the surface--- "Yeah man, that's what I'm talkin' about..!!".. They explode---"Game on..!!"

There's nothing like it..!! Your witnessing the "Big Blue Marble" as it was meant to be seen.. Your witnessing God's creation.. And I find for me personally, he "talks" to me when I'm "out there".. It's me, it's him and all the marvels of nature that hes created.. Like I said----nothing like it..

I'm sure it's not much different than what Waterman feels when he's on the Columbia River.. Moose, Elk, Deer on the banks.. Bear swattin' salmon as they're runnin' upstream.. Nature in all it's glory.. Feeling like you've left the world behind.. And for the short time "we" spend out there----nothing can touch us----all is "right with our world"....

But back to the post--- I can't imagine being "dropped off into the food chain" due to my vessel going down here in south Florida in the winter (or any other season for that matter).. Columbia River..?? That's like glacier run off water compaired to where I am.. I'd last all of 16 seconds in my surf baggies.. 3 minutes, maybe, in my full wet suit..!!

I don't even want to think about that.. But do want to think about keeping my little boat afloat and what I can do to keep her "up" if she was ever swamped.. I do have 2 floor boards but not a floor deck as everyone else.. I've been trying to keep this little boat as light, minimal, simplistic and easily repairable on the fly, as possible.. Now, I'm focusing on keeping her as "floatable" as possible.. My little boat is a 1980 14 foot, semi-V, MirroCraft, "Deep Fisherman" (I think..??).. 64 inch beam..Current floatation is under her bow seat and stern seat.. Middle seat has been removed and custom "frame" installed..


I just tried uploading photos of my little boat from this past May 2013, Sarasota to Everglade City adventure (6 days, 5 nights aboard)..They wouldn't upload.. (due to too large of photo pixels..??).. Any advice on how to get the photos up is appreciated.. And if I'm not able to get them up on iboats, please send me a personnal email address and I'll be more than happy to send them.. My email is: EDIT

 

[jigngrub]

Re: Flotation under floorboards----why there..??

Current floatation is under her bow seat and stern seat.. Middle seat has been removed and custom "frame" installed..

... and now there isn't enough floatation in your boat to keep it afloat. Should you take a wave over the bow your boat, your boat will dive like a submarine. At a minimum you need to put back the amount of foam that was removed from the middle bench to keep your boat afloat.


You can get a photobucket account for free to post pics with or resize your pics with the Microsoft Paint program.

 

[RichBKK]

Re: Flotation under floorboards----why there..??

That's the way the boat came when I bought her.. Middle seat had been removed and an aluminum square tube frame had been made to house a very large igloo cooler.. The previous owner was a professional mullet fisherman, cast netting off the bow and tossing the mullet he caught into the cooler.. Pretty good idea actually.. Safe enough for him as he never left the bay and was always "working" on the flats..

The frame itself has actually worked great for me as well.. It houses 1 of the 6 gallon gas tanks and 1 drybag with food, 1 small drybag with electronics and 1 gallon of water..

Because the frame is wider than the seat was, I was able to get a full 8 feet from the tip of the bow to the back of the frame.. So, my casting / sleeping deck and emergency tent / mosquitoe net are a full 8 feet long as well.. Plenty of room for fighting fish and plenty of room for a good nights sleep..


So, I'm looking for ways to get some flotation back into her without giving up too much underdeck storage.. And along the gunwales are the only way possible that I can figure out..

 

[jigngrub]

Re: Flotation under floorboards----why there..??

I'm guessing you lost a minimum of 5 cubic feet of floatation when that bench was removed, that's 300 lbs worth of floatation. What are the dimensions of your rear bench? That'll get you real close to how much foam was lost with the middle bench.

One 4' x 8' x 2" thick sheet of rigid foam insulation is 5.33 cubic feet... the problem is attaching it to your sidewalls so it doesn't rip itself out if the boat sinks instead of floating the boat, this is where the expanding urethane foam really shines because it'll bond itself to the hull.

I'd suggest a 16 lb./8 cu.ft kit of expanding urethane foam to get your boat back to where it'll float if you have an emergency.

 

[RichBKK]

Re: Flotation under floorboards----why there..??

My stern seat is:

58 1/2" long (gunwale to gunwale)
11 3/4" wide (bow to stern)
10" high (bottom of "foam container" to top of seat)

How I was thinking I'd attach the 2" thick pink or blue foam from Lowes was to glue the "form-fitted and shaped" (read: cut with razor knife) pieces together with epoxy glue, then glue that in the underneath, outside edges of the frame of the decking.. This area is screwed down with stainless steel screws and self-locking nuts to the 1 1/2 x 1 1/2" aluminum angle that makes up the support frame for the decking.. I would then enclose the foamed areas with thin aluminum siding cut to cover the foamed area (much like the foam is enclosed on the underside of the boat seats)..

With the foam "glued / attached" and held in place by the aluminum siding, under the sections of the screwed down decking I don't believe it could rip out or get out from under the deck.. But..

Thanks for the math and recommendation on how much foam I'd need, JignGrub.. But, doesn't the urethane foam (once mixed and in place against aluminum) ultimately cause problems down the road..?? I've heard it "eat / corrodes" aluminum..

 

[Watermann]

Re: Flotation under floorboards----why there..??

Rich, that post a great description of your area, boating and the fishing experience! An awesome read and one of the reasons I got hooked on the iboats forums.

I'm not a flotation guru with all the answers, all I did was foam in the under deck of my 16' SN. Since your space is limited for adding any additional flotation I think the cooler itself would have added a good deal of flotation to the boat if it was secured inside the boat with some sort of latch. The air void inside and foam in the walls all create buoyancy. Depending on the cooler size probably more flotation than the bench seat gave.

 

[ondarvr]

Re: Flotation under floorboards----why there..??

But, doesn't the urethane foam (once mixed and in place against aluminum) ultimately cause problems down the road..?? I've heard it "eat / corrodes" aluminum..

Sometimes, this is normally in saltwater, water will get into and around the foam and then be trapped there, and this leads to the corrosion. In fresh water it isn't much of an issue.

 

[jigngrub]

Re: Flotation under floorboards----why there..??

JignGrub.. But, doesn't the urethane foam (once mixed and in place against aluminum) ultimately cause problems down the road..?? I've heard it "eat / corrodes" aluminum..

No, it's not the foam.

The reaction you speak of is known as Galvanic Corrosion, and it doesn't only happen with the expanding foam. It'll happen when any material traps water (fresh or salt) against the aluminum hull. It could happen with the rigid sheet foam, especially if it's bonded (glued) to the hull.

Galvanic corrosion happens a lot with aluminum boats in fresh water, mainly at the transom wood. Water becomes trapped between the wood and the transom metal and can cause some god awful pitting... we see this a lot on this forum.

Galvanic corrosion occurs when water is trapped against aluminum, when the oxygen in the water depletes... the water becomes acidic and corrosive.

The best way to prevent this corrosion is to keep your boat dry, and if it becomes wet be sure to dry it out thoroughly.

Painting the inside of your aluminum hull before installing a new transom or foam is another good way to prevent this corrosion.

 

[RichBKK]

Re: Flotation under floorboards----why there..??

Thank you JignGrub, Ondarvr for the knowledge, input and suggestions.. Thanks Waterman for your kind words and "Cooler suggestions" also..

Here goes: Waterman, the "keep the cooler, it's flotation" thought did cross my mind and I thought seriously about keeping it.. But, the dang igloo is one of the really large ones, like 155 quarts.. It's massive and when sitting in the frame, the lid was a good 6 or 8 inches higher than the frame itself..And if I'd kept it, my 8 foot casting / sleeping deck would have been 20 inches shorter, 76 inches (or 6' 4" long).. I'm like 6'3" and to have my head wedged in the very "V" of the bow for sleeping just seemed nuts---"Hey man, I gotta get a good nights sleep with these long distant trips.."

Yes, it would have provided the flotation that I'm trying to put back in now but, it just didn't "work into the equation" when it came down to installing the casting deck and definately didn't as far as the "good nightsleep with tent and mosquitoe net" were concerned.. So, I opted to ditch the cooler

Jigngrub and Ondarvr, thanks so much for setting me straight on the urethane foam.. Last late Oct / early November (after buying the boat) I pulled the transom out and did find "pox" on the aluminum.. I sanded to remove the corrosion and took it down to bare aluminum.. I then filled in all the "pox pits" and covered most of all the aluminum where the old transom wood had been with "Marine-Tex" epoxy.. Then, covered that with 3 coats of "Glu-Vit" flexible epoxy.. Followed by 3 coats of Rustoleum self etching primer..Followed by 2 coats of Behr oil-based paint..

After the transom and sanding the entire interior of the boat, I gave all rivets and seams 3 coats of "Glu-Vit".. Then 2 coats of the self etching primer and 2 coats of the Behr oil base paint.. Everything has held up fantastic.. Paint is sticking well as is everything else that came before it (from what I can see and tell)..

Question JignGrub and Ondarvr: If the entire interior of the boat has been primed and painted (and it's holding on excellently), even if water was trapped between the hull and foam, am I still "in the clear" as far as the aluminum pitting and "pox" go..?? And if so, for how long would you guess..??

Personally, I love "do overs" and the thought of having something "adhere" to the hull that will take an electric Thanksgiving turkey carving knife to remove it somewhere down the road-----damn.. Sounds a heck of alot easier to just get a 2 man offshore life raft and watch my boat sink..!! (kidding, only kidding..!!)