Foam Core or Composite Stringers?

jj225

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Is it worth the extra money to go with a foam core hull etc? Raises the price by about 10k if you go with everything foam. Current boat is alum. so I didn't have that decision to make. Last glass boat had no wood except maybe the transom but not sure. Frankly, I didn't think builders used much wood these days but that aint so. Biggest concern of course would be rot but is that an over blown concern? Zero experience so would appreciate any and all input.
 

Eslang

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So why does every builder push a cored hull??Every builder I've ever talked to says a cored hull
Is better for weight, strength, and hull flexing. I have often debated this.
 

F/V First Team

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Raises the price by about 10k

Wouldn't you push it too?

And I don't push a cored hull, please don't toss me in with the rest of them.

The argument has always been that it makes for a "light" hull. I have yet to have found a scale with "light" somewhere on the dial. You are replacing layers of fiberglass for either foam or balsa core, or in some instances a honeycomb (either resin impregnated kraft paper or the material from recycled milk bottles to which resin doesn't stick) so you're saving the weight from the layers of fiberglass themselves and also the resin it takes to wet those layers of fiberglass out. However, you're shoving in blue/green/pink/white goo to bed the core into, you're adding resin to the product to seal up the kerfs and eliminate voids, and then you're adding the product itself. Go pick up a box of core, I don't care what it's made of, and tell me it's "light". In some instances, say a pilot house for example, using a core gives you a thicker product quickly and for how it is constructed it is a stiffer laminate than if one just used the total number of layers of glass. For example if one used the simple layup of gelcoat, 2 layers of 1.5 oz mat, 3 layers of 1808, 1.5 oz mat, and made a panel - let it cure and then propped it up on some blocking and stood on it, it would probably have a real swell curve to it and result in cracked gelcoat. Now if we tossed in some 12 mm foam core bedded into a super wet layer of 1.5 oz mat right after that first layer of 1808 and kept the rest of the layup schedule the same, let that cure, propped it up and stood on it... It wouldn't flex nearly as much. However, that panel will be noticeably heavier than the solid glass one. And a pain in the ass to repair if punctured - due to the reason that instead of penetrating in a localized spot, the core has a tendency to morph and carry the force along a longer area. Kind of like the fat kid doing a cannon ball in the pool. Effects a much larger area than if they did a pencil dive.

However, if one is making a solid laminate 3/4" thick from just glass alone, it would be tremendously overweight in comparison to the one with 12mm core. But a lot stronger too. If you have enough internal support one doesn't have to worry about hull flexing at all. You really think some plastic foam the thickness of the diameter of a dime will stop the force of the sea when you crest a 15' wave as you're heading into the wind and you fall though that open space and land into the next wave? It's your stringer system that distributes that load of pressure.

Boils down to how much you get caught up when being sold product, core is not snake oil by any means, and one should consider how they are going to use their vessel. If it is going to be sitting at the slip 99% of the time for mai tais and act like a floating porch, sure go with a core, it's not like you're going to be using a down east boat for the way it was intended to be run. But if you want to be able to go out, regardless of the weather, and come back home - go solid glass. You're wife will be glad you did.

And I know some of you reading this are going to pipe up by saying "but you just said to use it on the topsides, what gives?" Well chances are you won't be hitting any rocks or pilings from days gone by with your super structure. But if you are, you're upside down, and you have a whole other list of troubles. The super structure is there to keep the water off you - not to keep the water out. Consider that.
 

CaptDave

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Soild Glass Hulls

I know Stew of SW Boatworks is a huge fan of solid glass hulls and will do everything possible to get you to go that route. Hopefully we can pull the trigger within two years (need to get the new house first) and I will go with nothing but a solid hull with cored sides on the house and of course Strongwell deck supports and Coosa Board for the deck. As I told Stew the only wood I want to see on my next boat is a pencil.

Dave
 

jawz

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Wouldn't you push it too?

And I don't push a cored hull, please don't toss me in with the rest of them.

The argument has always been that it makes for a "light" hull. I have yet to have found a scale with "light" somewhere on the dial. You are replacing layers of fiberglass for either foam or balsa core, or in some instances a honeycomb (either resin impregnated kraft paper or the material from recycled milk bottles to which resin doesn't stick) so you're saving the weight from the layers of fiberglass themselves and also the resin it takes to wet those layers of fiberglass out. However, you're shoving in blue/green/pink/white goo to bed the core into, you're adding resin to the product to seal up the kerfs and eliminate voids, and then you're adding the product itself. Go pick up a box of core, I don't care what it's made of, and tell me it's "light". In some instances, say a pilot house for example, using a core gives you a thicker product quickly and for how it is constructed it is a stiffer laminate than if one just used the total number of layers of glass. For example if one used the simple layup of gelcoat, 2 layers of 1.5 oz mat, 3 layers of 1808, 1.5 oz mat, and made a panel - let it cure and then propped it up on some blocking and stood on it, it would probably have a real swell curve to it and result in cracked gelcoat. Now if we tossed in some 12 mm foam core bedded into a super wet layer of 1.5 oz mat right after that first layer of 1808 and kept the rest of the layup schedule the same, let that cure, propped it up and stood on it... It wouldn't flex nearly as much. However, that panel will be noticeably heavier than the solid glass one. And a pain in the ass to repair if punctured - due to the reason that instead of penetrating in a localized spot, the core has a tendency to morph and carry the force along a longer area. Kind of like the fat kid doing a cannon ball in the pool. Effects a much larger area than if they did a pencil dive.

However, if one is making a solid laminate 3/4" thick from just glass alone, it would be tremendously overweight in comparison to the one with 12mm core. But a lot stronger too. If you have enough internal support one doesn't have to worry about hull flexing at all. You really think some plastic foam the thickness of the diameter of a dime will stop the force of the sea when you crest a 15' wave as you're heading into the wind and you fall though that open space and land into the next wave? It's your stringer system that distributes that load of pressure.

Boils down to how much you get caught up when being sold product, core is not snake oil by any means, and one should consider how they are going to use their vessel. If it is going to be sitting at the slip 99% of the time for mai tais and act like a floating porch, sure go with a core, it's not like you're going to be using a down east boat for the way it was intended to be run. But if you want to be able to go out, regardless of the weather, and come back home - go solid glass. You're wife will be glad you did.

And I know some of you reading this are going to pipe up by saying "but you just said to use it on the topsides, what gives?" Well chances are you won't be hitting any rocks or pilings from days gone by with your super structure. But if you are, you're upside down, and you have a whole other list of troubles. The super structure is there to keep the water off you - not to keep the water out. Consider that.


NICE !!!

did i ever tell ya how much i dislike nida core ? ;)


i can't agree more with you - never agrue with common sense !
 

BillD

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Wouldn't you push it too?

And I don't push a cored hull, please don't toss me in with the rest of them.

The argument has always been that it makes for a "light" hull. I have yet to have found a scale with "light" somewhere on the dial. You are replacing layers of fiberglass for either foam or balsa core, or in some instances a honeycomb (either resin impregnated kraft paper or the material from recycled milk bottles to which resin doesn't stick) so you're saving the weight from the layers of fiberglass themselves and also the resin it takes to wet those layers of fiberglass out. However, you're shoving in blue/green/pink/white goo to bed the core into, you're adding resin to the product to seal up the kerfs and eliminate voids, and then you're adding the product itself. Go pick up a box of core, I don't care what it's made of, and tell me it's "light". In some instances, say a pilot house for example, using a core gives you a thicker product quickly and for how it is constructed it is a stiffer laminate than if one just used the total number of layers of glass. For example if one used the simple layup of gelcoat, 2 layers of 1.5 oz mat, 3 layers of 1808, 1.5 oz mat, and made a panel - let it cure and then propped it up on some blocking and stood on it, it would probably have a real swell curve to it and result in cracked gelcoat. Now if we tossed in some 12 mm foam core bedded into a super wet layer of 1.5 oz mat right after that first layer of 1808 and kept the rest of the layup schedule the same, let that cure, propped it up and stood on it... It wouldn't flex nearly as much. However, that panel will be noticeably heavier than the solid glass one. And a pain in the ass to repair if punctured - due to the reason that instead of penetrating in a localized spot, the core has a tendency to morph and carry the force along a longer area. Kind of like the fat kid doing a cannon ball in the pool. Effects a much larger area than if they did a pencil dive.

However, if one is making a solid laminate 3/4" thick from just glass alone, it would be tremendously overweight in comparison to the one with 12mm core. But a lot stronger too. If you have enough internal support one doesn't have to worry about hull flexing at all. You really think some plastic foam the thickness of the diameter of a dime will stop the force of the sea when you crest a 15' wave as you're heading into the wind and you fall though that open space and land into the next wave? It's your stringer system that distributes that load of pressure.

Boils down to how much you get caught up when being sold product, core is not snake oil by any means, and one should consider how they are going to use their vessel. If it is going to be sitting at the slip 99% of the time for mai tais and act like a floating porch, sure go with a core, it's not like you're going to be using a down east boat for the way it was intended to be run. But if you want to be able to go out, regardless of the weather, and come back home - go solid glass. You're wife will be glad you did.

And I know some of you reading this are going to pipe up by saying "but you just said to use it on the topsides, what gives?" Well chances are you won't be hitting any rocks or pilings from days gone by with your super structure. But if you are, you're upside down, and you have a whole other list of troubles. The super structure is there to keep the water off you - not to keep the water out. Consider that.

My wife dislikes boating &
she wouldn't mind if I never "made it back"!
I guess a cored boat is OK by me !

If/when the time comes to buy/build, solid glass hull for me.
 

jj225

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F/V thanks for the info. Very useful to say the least. You don't build a 22'-24' boat by chance? :D
 

Blitzen

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Is it worth the extra money to go with a foam core hull etc? Raises the price by about 10k if you go with everything foam. Current boat is alum. so I didn't have that decision to make. Last glass boat had no wood except maybe the transom but not sure. Frankly, I didn't think builders used much wood these days but that aint so. Biggest concern of course would be rot but is that an over blown concern? Zero experience so would appreciate any and all input.


Best answer here is to go do some research and figure out for yourself if it is right for your intended purpose and budget. There are pros and cons to all construction methods and it is important to weigh them all for your vessel's purpose. There is no blanket answer to say yes or no and if the 10 grand is important, than you should make the educated decision with all the facts in your hand for your boat.

Here is some opinion on cored hulls believed by many:

Fully Cored Hulls and Decks
Over the years we have had a good deal of experience with the different construction approaches. Back in Ted's Bayfield Boat Yard days the high volume requirements were a natural match for the hulls constructed using a solid laminate (single skin). Although these hulls were quite robust (very thick), the single skin process allowed a hull to be completed in just 2 1/2 days which is good for production levels. A current production Gozzard 37 hull takes just under 3 weeks to complete - so, despite what you might be led to believe, the main reason you would use a solid laminate is to increase production not to build a better quality boat.
What about durability and toughness of cored verses solid laminates?
Today most manufacturers take advantage of a cored laminate in their decks. It offers stiffness at a lighter weight but there are still some people who claim that a solid laminate hull is tougher and more robust against impact than a cored hull... unfortunately, this is not a true statement. In actual fact, independent labs studies have unequivocally proven that cored laminates of equal weight to their solid laminate counterparts outperform a solid laminate in impact (puncture) tests.
Advantages of Cored Construction using Core-Cell SAN coring materials
Cored hulls (and decks) offer a degree of safety that is analogous to the "double hull" or "double bottom" construction found in all new super tankers. If the outer skin is punctured, the core isolates the inner skin from further damage and maintains the water tight integrity of the hull better than a single skin laminate. Core-Cell performs this function better than other cores because of its linear nature and high elongation. Core-Cell can absorb the energy of any impact and dissipate it into the laminate without either skin damage or core damage. Cored construction alone provides a higher safety factor, and the use of Core-Cell increases this safety factor substantially.
Other advantages to a cored laminate include:
  • Noise and Vibration Isolation - Cored laminates are quieter than single skin laminates because they absorb rather than transmit noise and vibration.
  • Thermal Insulation - Cored laminates insulate the interior of the hull from both excessive cold or heat and will have less interior condensation.
  • Increased Panel Strength and Stiffness - Cored laminates provide a substantial increase in panel stiffness over single skin laminates.
  • Increased Safety Factor - The advantages of Core-Cell tend to deal with the higher safety factors resulting from higher impact strength properties of this type of core even over other coring materials such as balsa, other foams and syntactic cores on the market. For this reason, ABS (American Bureau of Shipping) requires a 3.33 safety factor on balsa, 2.5 SF on cross linked PVC cores but only 1.8 SF on Core-Cell. We couldn't find the SF for syntactic core but is considerably higher than balsa (read not as good).
  • Better Damage Tolerance - Core-Cell's linear properties will absorb, not transmit, impact loads and then will recover to original shape. It will not rot or absorb water.
  • Better Resale Value - Core-Cell is a premium core. Better boats are built with better cores
 

jerseysportfisher

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Fully Cored Hulls and Decks
Over the years we have had a good deal of experience with the different construction approaches. Back in Ted's Bayfield Boat Yard days the high volume requirements were a natural match for the hulls constructed using a solid laminate (single skin). Although these hulls were quite robust (very thick), the single skin process allowed a hull to be completed in just 2 1/2 days which is good for production levels. A current production Gozzard 37 hull takes just under 3 weeks to complete - so, despite what you might be led to believe, the main reason you would use a solid laminate is to increase production not to build a better quality boat.
What about durability and toughness of cored verses solid laminates?
Today most manufacturers take advantage of a cored laminate in their decks. It offers stiffness at a lighter weight but there are still some people who claim that a solid laminate hull is tougher and more robust against impact than a cored hull... unfortunately, this is not a true statement. In actual fact, independent labs studies have unequivocally proven that cored laminates of equal weight to their solid laminate counterparts outperform a solid laminate in impact (puncture) tests.
Advantages of Cored Construction using Core-Cell SAN coring materials
Cored hulls (and decks) offer a degree of safety that is analogous to the "double hull" or "double bottom" construction found in all new super tankers. If the outer skin is punctured, the core isolates the inner skin from further damage and maintains the water tight integrity of the hull better than a single skin laminate. Core-Cell performs this function better than other cores because of its linear nature and high elongation. Core-Cell can absorb the energy of any impact and dissipate it into the laminate without either skin damage or core damage. Cored construction alone provides a higher safety factor, and the use of Core-Cell increases this safety factor substantially.
Other advantages to a cored laminate include:
  • Noise and Vibration Isolation - Cored laminates are quieter than single skin laminates because they absorb rather than transmit noise and vibration.
  • Thermal Insulation - Cored laminates insulate the interior of the hull from both excessive cold or heat and will have less interior condensation.
  • Increased Panel Strength and Stiffness - Cored laminates provide a substantial increase in panel stiffness over single skin laminates.
  • Increased Safety Factor - The advantages of Core-Cell tend to deal with the higher safety factors resulting from higher impact strength properties of this type of core even over other coring materials such as balsa, other foams and syntactic cores on the market. For this reason, ABS (American Bureau of Shipping) requires a 3.33 safety factor on balsa, 2.5 SF on cross linked PVC cores but only 1.8 SF on Core-Cell. We couldn't find the SF for syntactic core but is considerably higher than balsa (read not as good).
  • Better Damage Tolerance - Core-Cell's linear properties will absorb, not transmit, impact loads and then will recover to original shape. It will not rot or absorb water.
  • Better Resale Value - Core-Cell is a premium core. Better boats are built with better cores


The pretty pictures in this article disagree

Are They Fiberglass Boats Anymore? by David Pascoe, Marine Surveyor
 

hntrss

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I dont think its fair to compare anyone's DE boat to some production model SeaRay. There is nothing wrong with a properly cored hull. They would not ever fall apart like those POS.
 

Powderpro

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I think any of the top-tier builders like Flowers or Wesmac would be fine getting a cored hull from. Comparing a top-tier downeast to a production boat like a Searay isn't a fair comparison. If the core isn't properly installed during the layup of the hull, you will have SERIOUS problems down the road. I personally prefer a solid glass hull and even if a cored hull were the same price (which they are not), I would still opt for the solid glass. All the Calvin Beals that I'm aware of are solid glass hulls. I can understand the "benefits" of a cored hull, and I understand why guys opt for them, but I still prefer solid.
 

pjitty

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Blitzen: I agree with you 100%. Jersey Sport: Cruisers Yachts are cored hulls, never hear anything about them delaminating. David Pascoe ripped into Sea Ray because to some they are concidered high end boats, now we know better, also the boats in question were from the 1990's,I think technology [ don't have spell check] has advanced a little from 20 years ago. Just my opinion, and was never afraid of any new technology. Thats how we got to Fiberglass boats from wood...

Joe D
 

Blitzen

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The article you quote is about as old as the first LED light bulb. Things have changed so much on the construction side that any good builder with good building practices does not have to worry. And as for the future get used to it because it is all about weight and strength as fuel goes through the roof. If you want a solid hull that is your choice and it is fine but if someone else wants a stiff, strong, lightweight cored hull that is fine too if it is done properly.
As with a solid hull if not done properly it will expand like an accordion if hit hard enough. Just a wee bit too much resin in the keel isn't so strong, or how about we just finish laying up this hull after deer hunting season. Core or no core it is about attention to detail and doing the job properly.
 
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