Do I need foam in my hull??

[bird391]

I am rebuilding the floor, and stringers in my 1978 17ft. Lund fiberglass bow-rider. This boat will only be used on local lakes and rivers. It will never be in salt water and never be miles and miles off shore. When I started taking out the old the foam was soaked to the core and I'm sure it helped the wood rot much faster than it would have without the foam. The total weight of the soaked foam must have been a few hundred pounds. My questions are this. Is the foam necessary? Does it provide for a smoother ride across the water or make things a little more quite in the boat? Does it do anything structurally? Is there an alternative to foam? If the foam is a must what is the most cost efficient way to add foam. Any foam ideas anyone has would be greatly appreciated.

Thank you,

Jason

 

[rockyrude]

Re: Do I need foam in my hull??

The foam is strictly there to keep 'er from going down should she get swamped. Some guys go back with the expanding foam that the original used, some cut up sheets of the foam to the desired thickness found at the "box" stores.

 

[rov_aaaa]

Re: Do I need foam in my hull??

I restored a 16ft trihull, and I used the foam insulation sheets from lowe's.

They usually come in either pink or blue, they're 4ft by 8ft, by 2inches thick. I bought a few of those, cut them to shape to fit inbetween the stringers, then stacked them up to right below the level of where the new floor was going to be.

I did the math and each styrofoam sheet, at 4ft by 8ft, by 2 inches thick, has a potential buoyancy displacement of 335 pounds. So if you can get a total of 2 of those sheets in the hull of the boat, cut to fit inbetween the stingers and stacked up to the floor, you have almost 700# of emergency foam bouyancy, and they weigh almost nothing.

 

[lowkee]

Re: Do I need foam in my hull??

The question of the ages. Your boat can sink in 4 feet of water or 300 feet, either way it requires some major work to get it back afloat. It is really a matter of risk assessment. How likely is your boat to get swamped and will you want the recover the boat if it does? Answer those two questions and you have your answer. I opted for leaving it out, but my reasons are my own and yours should only be decided by you.

 

[BobsGlasstream]

Re: Do I need foam in my hull??

I would ( will ) put it back in mine.
As for which foam to use, the pour in type foam or the pink stuff from the lumber yard, They have about the same amount of floatation displacement per cubic foot. Based on the numbers from the previous post.
The pour in type is about 62 pounds per cubic foot buoyancy for the 2# density foam.
The good thing about the pink stuff from the lumber yard, is you don't have the mess of mixing the material and you don't have to worry about the ambient temperature when you use it.
Just food for thought
Bob

 

[Bondo]

Re: Do I need foam in my hull??

My questions are this. Is the foam necessary? Does it provide for a smoother ride across the water or make things a little more quite in the boat? Does it do anything structurally? Is there an alternative to foam? If the foam is a must what is the most cost efficient way to add foam.

Ayuh,.... This topic has been debated to death,....
Do a Search in this forum on "Foam",...
It shouldn't take you much more than a week or 2 to read the results....

Btw,.... No foam in My barges...

 

[Paul Ryan]

Re: Do I need foam in my hull??

My USCG Cert (on the dash) says boat meets requirments in Electrical, Ventaltion and couple of things and last say's "Basic Floation". Would that mean my boat will float under a not so normal event??? Almost requiring my boat to have foam???

 

[Paul Ryan]

Re: Do I need foam in my hull??

Just found this link and it answer my question. I think would answer the question for this thread as well.

http://forums.iboats.com/showthread.php?t=191283

 

[NSBCraig]

Re: Do I need foam in my hull??

It's nice insurance but you don't need it.

I don't know anybody who swamped a boat so bad that the bilge pump and giving it some gas didn't keep it afloat.

I chose to go without.

 

[Marcq]

Re: Do I need foam in my hull??

If I would go to the trouble of replacing deck and stingers I would certainly add some kind of flotation, plastic pop bottle comes to mind, light, all kinds of size to fit anywhere, cheap and a good way to recycle. I'm not to crazy about foam
Even Ping Pong ball for tight spot would do good a job and they are cheap also
Now start drinking pop while playing Ping Pong

Marc..

 

[Panther2006]

Re: Do I need foam in my hull??

Does it do anything structurally?



I think this depend on your hull. I have a Crestliner and I think that the foam is for Floatation and Structure. I read on these forum that this was the case so please read has much as you can. Upon replacing my floor I accidently cut through my hull and to my surprise it was only 1/16 to 1/8th thick fibreglass. Therfore it was proof positive that I will need form for strenght.

Just my opinion, BTW you can't hurt to put lots of foam.

 

[F14CRAZY]

Re: Do I need foam in my hull??

Does it do anything structurally?



I think this depend on your hull. I have a Crestliner and I think that the foam is for Floatation and Structure. I read on these forum that this was the case so please read has much as you can. Upon replacing my floor I accidently cut through my hull and to my surprise it was only 1/16 to 1/8th thick fibreglass. Therfore it was proof positive that I will need form for strenght.

Just my opinion, BTW you can't hurt to put lots of foam.

Indeed, the need for "structural" foam varies. I did not replace the foam in my Capri and its been pounded by small craft advisories...no hull damage, no gelcoat cracks...

 

[Beeched]

Re: Do I need foam in my hull??

I used the pour in type of foam. It did take a lot more work than cutting up sheets of foam. It took me over a year to get information on my boat. I did finally talk to someone that helped design and build the boat. Definately glad I talked to him. The foam in mine is used for structure as well as floation. Once I had the old foam out and was walking directly on the inside of the hull, I could see why it is needed for structure. Also like the noise reduction and the idea that it would not sink to the bottom.

Whatever you decide best of luck on your project.

 

[Mark42]

Re: Do I need foam in my hull??

- In some boats, foam is structural.

- Foam does deaden noise.

- If you are rebuilding your boat and seal the stringers well or use pressure treated lumber in the rebuild, then adding foam will not contribute to rot.

- Its nice to know the boat will not sink, taking the expensive motor with it.

- Its a lot cheaper to have a swamped boat towed back to port than recover a boat sitting on the bottom, be it 6 feet or 100 feet down, its still expensive.

 

[bass or bass ?]

Re: Do I need foam in my hull??

Foam will provide a quieter ride due to sound absorbing qualities.
I had to rebuild the stringers and floor deck in my 1977 Glastron Sportster last winter. I did add new foam. The reason your old foam was waterlogged and weighed a ton is because at the time our boats were built, only open cell foam was available,and it absorbed water, oil, etc.Make sure you use closed cell foam on your rebuild.The foam from the "big box stores" is open cell foam and will waterlog just like your old foam .Stay far away from it.If you're going to refoam, spend a little more money and do the job right and use the right material. I got mine from McMaster-Carr Company. They were exceptionally helpful in making sure I got just what I needed for my job, and I can pass this information on to you.Below is the description of my order and their information.

McMaster-Carr
9630 Norwalk Blvd.
Santa Fe Springs, CA. 90670-2932


Here is the product information;

#9334K27 polyethyene foam sheet, 2" thick, 24"X54" (I ordered 4 sheets and used all but a piece 24"X10")

unit price-$52.23
extended price-$208.92
shipping-$7.50
total-$216.42

This foam is blue in color. It cuts easily with a serrated kitchen knife. I really packed my below deck area with it, cutting even wedge shaped pieces to fill the space. I now have @ 4 times the foam the boat came with originally.
I hope this helps you with your boat rebuild, and I will be happy to help you with any other rebuild questions you may have.
Oh yes, as to your new wood. Treat it this way to waterproof it. Mix fiberglass resin and dilute it to a watery consistancy using acetone. Paint this on all surfaces of your new wood, 3 coats. It will soak into the wood, the acetone will evaporate, leaving the wood impregnated with fiberglass resin. Then apply full strength coat of resin and apply fiberglass mat, then a final coat of resin. Rough up the cured final coat of resin with an orbital sanded before applying carpet adhesive. Apply carpet and use a roller to smooth out and eliminate bubbles. I used a heavy wooden bakers rolling pin.
My project turned out beautifully, yours will too.
Good luck and have fun.
Allen

 

[BobsGlasstream]

Re: Do I need foam in my hull??

Just found this link and it answer my question. I think would answer the question for this thread as well.

http://forums.iboats.com/showthread.php?t=191283

Paul Ryan
I think that does answer the question of what is required.
I had already planed to put the foam back into my boat. My plan is a little different then most. I plan to use a 2 part PUR foam, it's a EA foam.
Have a great day.
Bob

 

[sparticus]

Re: Do I need foam in my hull??

Does anyone know how much boyancy an empty drinking water bottle might have? It would appear to me to have a lot. I have seen it mentioned a few times in the foam threads but no real numbers have been shown.

 

[Robert D]

Re: Do I need foam in my hull??

I went with no foam under the floor. However, I did put foam under the gunwales....,much more than the factory put under the floor in 1972! I want nothing under my deck except pressure treated wood, all glassed in, with clear drains to the bilge....and 2 inspection ports where I can still see and feel, after several hours of boating....it is still dusty! No more rot for this boat. If it gets swamped, it'll float. If you go the way I did and put cardboard forms under the gunwales while the foam cures, just make sure you get all your hardware mounted first. (cleats, lighting, etc.) Otherwise you'll be cutting some foam out to get the nuts on. I will admit it was quieter with 500 pounds + of waterlogged foam under the deck.....but I feel much safer now, even if it is noisier! I made this boat so waterproof, I left out the bilge drain in the back. (It'll spend it's time in the heated garage....) 30 hours + on the completed project so far, and not even a drop of condensation for the bilge pump to get rid of. I only did the foam under the gunwales in case the Coast Guard ever starts inspecting here in Oregon....(They do not)....but I am never far from shore. Just fresh water rivers and lakes. We get the Sheriffs boats in the summer, inspecting for lifejackets, an oar, whistle, basic safety stuff then gives you a sticker. After my total rebuild, I would never, ever, ever, ever put anything under the deck but air space. You want flotation? A nautical engineer I consulted explained to me the gunwales were the safest bet in a swamping situation. Put in under the deck and it will float allright....possibly upside down! In the gunwales, it'll stay upright. He felt the reason for under the deck by manufacturers was an ease of installation issue satisfactory to the Coast Guard....note the Coast Guard recommends a handle on the outside of the hull at the bow, as 'most boats will capsize with the bow up." They don't care which way the boat floats.....just that it'll float. As for me, I care which side stays up!

 

[SS Flasher]

Re: Do I need foam in my hull??

You didn?t mention the type of foam that came out but I believe you should replace with the type of flotation that was there. Many manufacturers use the expandable foam because it helps make the hull more rigid thereby improving the performance of the boat. It can also help slow down a leak if you put a hole in the hull by running into a rock, log or whatever (never happen) and it is an effective sound barrier.

 

[PiratePast40]

Re: Do I need foam in my hull??

I've heard stories of people hitting partially sumberged RR ties, stumps, logs, and other debris. My thinking was that if something punched a hole in the hull, closed cell foam would prevent total flooding and allow me to motor back to shore. The flip side is that with ping pong balls or empty pop bottles, they would at least be able to tell where the boat went down.

Pour foam definately adds some time to a restoration project and it makes you want to cry to be putting those holes in your brand new deck. But for me, the safety aspect was more important. I spent a tremendous amount of time on boats that were designed to go underwater and come back up. My 18' runabout isn't one of those .

Of course, everyone is certainly entitled to their own opinion.