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Does foam contribute to structural integrity on catamaran hull?

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Does foam contribute to structural integrity on catamaran hull?

Old 02-12-2019, 06:06 AM
  #81  
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Originally Posted by commuter boats View Post
Are you aware that "oil canning", what you referred to as" flexibility within the fiberglass" is destructive to the fiberglass? If you fill a cardboard box full of pour foam does the box become more rigid? Well that works for a stringer grid or a large void in a hull also.
Chemically, the foam used to by Boston Whaler is referred to as a urethane foam, coosa it's also a urethane foam with some poorly wet out fiberglass fibers Incorporated. The coosa is considerably higher density but it's still a foam that is not very resilient, it's not ductile, it doesn't tolerate much abuse before the cells start breaking down. In the real world and particularly after fiberglass skins are applied, those fibers don't add much, it's as much a sales pitch is anything, Bills a custom yacht builder here on the forum prefers a similar product without the roving.
Gerald
Gerald, Personally I would use wood and more glass, but I understand that's another story and today's boat builders sell boats by the LBS and not by the glass. And they claim lighter is better. So they use all these forms of new composite, whatever. What I have found in my experience working with what we have. Is that Coosa or Gator board or Airex PWW, "fiber-reinforced structural Foam", or "coosa". Has a more structural body than just pored foam in to a glass body. I have seen transom composite foams that are so dense that I can't dent them with a hammer. And that's without the glass installed yet. Problem is its very expensive and most builders will not use it. My point to this is that low density or pored foams on their own, if the glass surrounding them de-laminate or are compromised. The foam itself cannot sustain structure on its own. If only a filler. I had a boat in 97 that had a T-top connected to the deck. The deck was a closed cell low density foam. Manufacturer did not threw boat with a backing plate. Over 2-years of use the tension de-laminated the glass. What was left nothing for the screws to hold on to in the core. The Foam has no solid structure. SO it fell apart.

Here is my deck. 3/4 inch Coosa, before its glassed on both sides. Can you compare that to just a 1/8" or less of glass skin and nothing more than pored foam.



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Old 02-12-2019, 06:07 AM
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Here is mine.............................................. .................................................. ........................................
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Old 02-12-2019, 08:22 AM
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I would suggest that you read the tech data sheet on any product you plan to use. Light foams do not have a lot of structural stength compared to heavier denser ones, but the Op asked if he needed something besides air and I hope that someone will agree that foam surrounded with bonded finerglass is a little stronger than nothing.
I personally agree with Gerald about Coosa as I believe there are more cost effective products and am glad to now know that his experience backs up what I suspected.
The brochere about Baltec’s Airex compares a lot of foam based products pretty well and I learned a lot from it if this is something that intetests you, with hard data.

https://www.3accorematerials.com/en/markets/marine
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Last edited by Bullshipper; 02-12-2019 at 08:29 AM.
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Old 02-12-2019, 09:20 AM
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Originally Posted by Bullshipper View Post
I would suggest that you read the tech data sheet on any product you plan to use. Light foams do not have a lot of structural stength compared to heavier denser ones, but the Op asked if he needed something besides air and I hope that someone will agree that foam surrounded with bonded finerglass is a little stronger than nothing.
I personally agree with Gerald about Coosa as I believe there are more cost effective products and am glad to now know that his experience backs up what I suspected.
The brochere about Baltec’s Airex compares a lot of foam based products pretty well and I learned a lot from it if this is something that intetests you, with hard data.

https://www.3accorematerials.com/en/markets/marine
Bullshipper, and As you mentioned with Airex. The Core Baltic. is one of the best ever for resign and strength bonding known. But like a wood product it can Rot if compromised. They Also make a product very similar to Coosa. Coosa is only the name the process is used by there companies.
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Old 02-12-2019, 09:54 AM
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Originally Posted by THE BARRACUDA View Post
Bullshipper, and As you mentioned with Airex. The Core Baltic. is one of the best ever for resign and strength bonding known. But like a wood product it can Rot if compromised. They Also make a product very similar to Coosa. Coosa is only the name the process is used by there companies.
Rot, with what? Can you show me your source on this as its contrary to what I have researched.

https://www.gulfstreamcomposites.com...2_4x8_each.htm

Last edited by Bullshipper; 02-12-2019 at 10:10 AM.
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Old 02-12-2019, 10:29 AM
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Originally Posted by Bullshipper View Post

Rot, with what? Can you show me your source on this as its contrary to what I have researched.

https://www.gulfstreamcomposites.com...2_4x8_each.htm
Using Balsa Core. Baltek.- balsa. ?? Its wood it will rot. if water compromises the core. It its probably the best material for bonding glass and resin.
https://www.3accorematerials.com/en/...s/baltek-balsa

AIREX® T92 is a thermoplastic structural rigid foam this which comes up on the article, will not rot.

Last edited by THE BARRACUDA; 02-12-2019 at 10:35 AM.
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Old 02-12-2019, 11:11 AM
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Baltik makes core materials other then balsa core but I'm one of the few advocates on this forum for balsa, I have about 50 ft.² in the highest loaded portion of the bottom of my personal boat... New construction.
We're really getting away from OP's original question (which I couldn't give a definitive answer partially due to the lack of information .
We've seen a lot of catamarans with cracks within the tunnel, the loads on a catamaran aren't necessarily intuitive or easy-to-understand and I really doubt that many of them are overbuilt, I would consider everything that was there to be necessary and if I was to take anything out I would be fortifying what was left .
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Last edited by commuter boats; 02-12-2019 at 11:43 AM.
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Old 02-12-2019, 11:47 AM
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Originally Posted by Jumpsummo View Post
The bulkheads are there to hold the deck up. The foam has zero structural value. Maybe a little sound deadening. Zero value and huge downside on resale if you put it back in Some KVs get waterlogged.
WAY WRONG!!!!! Two pound closed cell foam is used all the time in building for structural purposes....Called SIPS, structural insulated panels. Ikea's walls are made with them. two sheets of sheet metal with foam in between them..........Carolina skiff without foam in the hull would be as floppy as two sheets of thin plastic.
To answer the OP, yes, it will provide extra rigidity to your hull....that is if you want it.
Get a 1 foot square block of simple Styrofoam and try to twist it....and that is nowhere near the strength of two pound density closed cell
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Last edited by bluevein; 02-12-2019 at 11:53 AM.
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Old 02-12-2019, 11:50 AM
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Originally Posted by tunnles View Post
If YOU HAVE TO RELY ON FOAM FOR STRUCTUAL INTEGRITY THEN YOUR IN TROUBLE AND DONT UNDERSTAND BOATS AND BOATING !
Obviously you have never seen a Carolina skiff. But what do they know, they have only been selling tens of thousands of them a year for many years.
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Old 02-12-2019, 12:17 PM
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You eggspurts can do as you want. That thin foam does not add much at all. It breaks down. It waterlogs. It was never meant to be in OP's hull. That mistake among others helped kill the US brand.

The Aussie hulls don't have foam. The newer hulls of similar heritage don't have the junk poured foam either.

Perhaps you guys should read a book on boat building, read a topic with pictures of a modern cat build or perhaps go buy a boat so you can make intelligent comments.
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Old 02-12-2019, 01:55 PM
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Originally Posted by Jumpsummo View Post
You eggspurts can do as you want. That thin foam does not add much at all. It breaks down. It waterlogs. It was never meant to be in OP's hull. That mistake among others helped kill the US brand.

The Aussie hulls don't have foam. The newer hulls of similar heritage don't have the junk poured foam either.

Perhaps you guys should read a book on boat building, read a topic with pictures of a modern cat build or perhaps go buy a boat so you can make intelligent comments.
If you fill an empty space between 2 walls with foam to tie them together. 2 walls are stronger than one. When that foam is 18” thick, its fairly stiff, and fair to say stiffer than air.
Because the foam is faced with fiberglass it is also harder for a fuel tank to penetrate. If the tensile strength is even as low as 30 psi, the fg spread the fprce on it and a face measuring 30 x 16” x 30 psi requires about 14000 lbs pf static weight to crush it + the strength pf the 2 walls fiberglass that are also bomded to the hull.
I didnt recommend foam, but to deny its place in frp fabrication is unfounded.
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Old 02-12-2019, 02:01 PM
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The foam in my cat just prevented water from draining and sped up the bilge rot. I'm keeping the bulkheads and losing the foam
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Old 02-12-2019, 02:19 PM
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Originally Posted by Jumpsummo View Post
You eggspurts can do as you want. That thin foam does not add much at all. It breaks down. It waterlogs. It was never meant to be in OP's hull. That mistake among others helped kill the US brand.

The Aussie hulls don't have foam. The newer hulls of similar heritage don't have the junk poured foam either.

Perhaps you guys should read a book on boat building, read a topic with pictures of a modern cat build or perhaps go buy a boat so you can make intelligent comments.
Since you apparently consider yourself an "eggspurt", or at least type like you are, I'm curious, just how many boats have you built? How many have you repaired? How many have you designed? Engineered?

There is more that one way to skin a cat, or in this case, build one. To dismiss urethane foam out of hand is not all that complementary to your expressed knowledge.
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Old 02-12-2019, 02:21 PM
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To get back to the boat that this thread is actually about, his boat does not need foam for structural strength, it probably does /did contribute some, but, that's not his problem, he wants to remove a bulkhead, let's forget about how strong foam is or isn't, the bulkheads are there for a reason in that boat, and it's not to hold the floor up, I think it could be removed if the storage "box" that was built into the space was properly constructed and glassed in, but it's an educated risk that only the owner can say whether he is willing to take.
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Old 02-12-2019, 04:06 PM
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Here is a spec sheet for a closed cell (2lb) spray foam that I use in my construction projects. It has 35psi compressive strength and 101psi tensile strength. Does not absorb water (0.87%), all foams are not equal even when talking about one 2lb closed vs another. This particular one has a lot of blowing agents to allow it to be sprayed in 6.5" passes. But in boat construction you can use pourable foams as some have mentioned much higher than 2lb density and most likely even stronger than this one. Would I rely on it in building a boat, no, but will it help? Definitely.

When we get overspray on studs and other hard surfaces I use a chipping hammer with a chisel blade to remove it, it is tough stuff.

Heatlok-HFO-High-Lift.pdf
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Old 02-12-2019, 06:40 PM
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All that info is very nice, but completely unnecessary, all the foam has been removed, and it was never needed for structural strength in the first place, it was simply added to comply to a standard, there is literally thousands on those boats still in service here, none with foam in them unless it was asked for by the original purchaser maybe, so, let's just move on from which foam is best.
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Old 02-12-2019, 06:57 PM
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Originally Posted by noelm View Post
All that info is very nice, but completely unnecessary, all the foam has been removed, and it was never needed for structural strength in the first place, it was simply added to comply to a standard, there is literally thousands on those boats still in service here, none with foam in them unless it was asked for by the original purchaser maybe, so, let's just move on from which foam is best.
Are you sure that those built in the US were otherwise similar to the ones built in Australia? I find it easy to imagine a builder who for whatever reason decides to put 150 pounds of foam (75 ft.³ at 2 pounds per cubic foot ) might take a laminate out of the hull stack because the foam will prevent oil canning and a desire to maintain a target weight.
I don't find production boats to typically being overbuilt.
You can say whatever you want about Bayliner as a builder but they probably employ more engineering staff than average. In one year I saw six transom failures on the same model of one of their boats, the next model year had about 6 ft.² of half inch plywood added as gussets to the transom and just a little bit more chop, probably not much more than 10 pounds added and the transoms quit failing.
Gerald

Last edited by commuter boats; 02-12-2019 at 07:21 PM.
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Old 02-12-2019, 07:34 PM
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The owner states this was made by the Australian owners, and those ones were built the same as the ones here.
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Old 02-13-2019, 02:04 AM
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Oh yeah lots of blah blah blah and same crap usually from many non thinkers !
There are many types of foams in varying degrees flexibility and something that manufactures don't tell anyone ! some is completely suitable for mattresses and used quite satisfactory for children's beds ! And for bodies with deformities can be made to any shape ! Been there used to make formers for special need people for wheel chairs and car seats and modular special beds ! when the children grow the basic seat had there shaped foam block removed and a new shape was blown to suit there new and more comfortable body shape that was needed !!
Some foams could be made as hard as Pine timber and drive nails into it !' all the way though to soft and flexible ! and for the boat thing water absorbsion is the greatest and biggest problem . Personally I wouldn't touch any boat that rely on foam for any part of its structural integrity !
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Old 02-13-2019, 03:17 AM
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Originally Posted by commuter boats View Post
Are you sure that those built in the US were otherwise similar to the ones built in Australia? ....
They would have been built the same up to a point where US regulations started to impede, such as "flotation" and bilge pumps and drain plugs all of which were not part of the original design. The only spin off hatches were in the most rear compartment and only there to access the pod bolts. The only time a KC ever required a bilge pump was when there was a bilge, such as stern drives or shaft drives otherwise what's the point? Same with drain plugs, total waste of space, what were they going to drain. It appeared building boats in the US were all tarred with the same brush even if the requirements were an absolute waste of space.

Even in Oz the requirements are dumb, try explaining to a boating patrol officer why you don't have a bilge pump in a KC, don't have a bilge sir, but the boating requirements states you have to have a bilge pump, well I don't have a bloody bilge to put one in do I? Oh, So then where are your paddles, every boat this length requires 4 foot paddles, yes sir I have 4 foot paddles but as you can see I can't even touch the water sir, ever tried paddling 3 tonne of KC with 4 foot paddles, even more useless than the bilge pump. As for foam well that's not on their radar, under the floor out of sight out of mind and if anybody ever wants to play slippery dip then try sitting on the bottom of an upturned Cat with a belly full of foam, not that it makes any difference you are still up the wrong way, so why bother with it in the first place, serves no purpose
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