Foam Core Hull

[Polux]

Originally Posted by leftbrainstuff

This so called piece of expert advice requires a firm response by an engineer.

The general statement that cored is better is typical of a comment not based on any evidence.

Lets list some pros and cons

Cored layup
1) cheaper especially for carbon laminate
2) lighter
3) cheaper to manufacture and this has been the big driver since the 70s oil crisis up to today where only high volume manufacturers survive
4) poor penetration resistance
5) subject to delamination of foam to composite interface leading to substantial loss of bending, shear and compression stiffness
6) poor delamination detectability
7) more challenging to repair and meet the original design strength
8) core to laminate interface integrity testing requires destructive testing to validate load derating

Solid layup
1) more expensive
2) heavier
3) can be manufactured and repaired with good quality by relatively low skilled labor
4) much better penetration resistance
5) no loss of shear, bending or compression strength over time
6) issues due blistering readily detectable and can be repaired piecemeal
7) no complicated jigs or fixtures needed to carry out repairs. Self supporting
8) load testing by simple non destructive deflection testing.

In summary cored hulls are cheap and quicker to build and ideal where lightweight for performance is the primary design driver. Or to minimize build cost.

Solid layup for longevity and field repairability.

30 years of building and repairing motorsport and aerospace composites calls bs on the surveyors wisdom.

By your answer I can deduce:

1- you are not a composite engineer.
2- Your boat is an old boat without a cored hull

Regarding price of a cored hull regarding a single skin hull it seems evident that if cored hulls were cheaper to built the boats that are built as cheap as they can be, mass market production boats, they would have cored hulls. But no they haven't, contrary to more expensive sailboats that use cored hulls.

The fact that a cored hull is a way better solution regarding on yacht boat building, due to low weight and much superior stiffness, is the reason why today expensive brands use cored hulls and cheaper boats use single skin.

This was probably written by a composite engineer or designer like they like to be called these days:

"Although the largest market for core is still aerospace — where high-performance aluminum and aramid honeycomb cores are used in aircraft primary structure, as well as in interior panels and floors — honeycombs, foam and balsa wood play a significant role in structural parts for the marine, wind energy and transportation markets. Lightweight, low in density and available at relatively low cost, core materials provide the foundation for incredibly strong and stiff sandwich structures, when placed between skins made with reinforcing fibers and resin. Given the right combination of core, composite skins and adhesive, composite manufacturers can deliver cost-effective sandwich structures to customers in virtually any non-aerospace market where high stiffness and low weight are design priorities."
http://www.compositesworld.com/artic...site-laminates

[Polux]

Since we are talking about it I would like to call the attention for something that can only be called as the composite revolution.

Initially GRP boats were already made of composite materials, fiberglass and resin. Them they started to use more composite materials like a balsa, foam or aluminium core, started to use different kinds of fibers, including carbon and technologically more evolved cores, cores that can provide bigger structural resistance and cores with closed cells that don't absorb water.

Vacuum assisted infusion come from the race building world and now is used on many cruising boats and structural computer efforts analyses made the uses of fibers and thickness to vary according to the needs on the different parts of the sailboat, even structural parts.

All this comes first from the top racing world were boats needed to be very light and very strong and as been coming slowly from that world to the cruising world, being this one a much more conservative one, including builders.

The revolution I talk about regards the speed of that transfer that on the last years had increased exponentially probably due to brands like Pogo, Django or JPK to start making besides race boats, cruising boats using the same building techniques and also top designers designing top maxi cruising yachts to be built with the same techniques and materials used on maxi racing boats.

On the last decade those maxi yachts abandoned aluminium as the choice material and passed to be built overwhelmingly in carbon.

For a long time already, shipyards that built top big racing boats, were working on the building process not only with the designers and their engineers but also with composite engineers that tailored specific composite fibers accordingly with the needs of different parts of the boat. That part of the building process become so important that soon we saw several specialized engineering cabinets appearing on the market.

Last year on Dusseldorf while visiting a ICE 52, a new brand on the market, I was agreeably surprised to find that I was not having a dealer showing me the boat but and engineer (from the shipyard) that new everything about the boat, that can be built using in the hull different fibers, e glass reinforced with carbon fibers to fully carbon and that is built like a top offshore racing boat, with tailored fibers and using different thickness according with structural needs.

I did not understood how a recent shipyards could have the grip and the mastery of all those techniques but he explained that it was not a new shipyard but a very experienced one that had made many big carbon racers and maxi yachts, that used to make on offs to top NAs that is now making their own boats.

And the real surprise was the price. Of course it is not a cheap boat but a 52ft Yacht that costs about the same as a Solaris of the same size, with a much more evolved building and about as as much as for instance a Catana 42.

I was convinced. If I had the money I would have one.

https://www.youtube.com/watch?v=c6z9nIpAa54

[Dockhead]

Originally Posted by rourkeh

"To defy the authority of empirical evidence is to disqualify oneself as someone worthy of critical engagement in a dialogue."

Dalai Lama

Indeed. But the opinions of one blow-hard surveyor cannot be called "empirical evidence".

What empirical evidence actually shows is that cored hulls are far lighter and far stronger than solid ones, which is why, as Polux pointed out, you can't buy any racing boat or any performance boat without one.

The downside is much greater cost (which is why cheap mass produced sailboats have solid hulls) and a more complex structure, which brings greater risk of problems. The risk is great with badly made boats ('70's and '80's power boats like the ones Pascoe was writing about), but is slight when well built using modern techniques.

With the exception of Oyster, all high end European boats have fully cored hulls. Problems are exceptionally rare. For example, the entire last generation of English Moody yachts, built from the mid '90's through about 2006, had fully cored hulls, using fully encapsulated balsa blocks. Although these boats are about 20 years old now, not a single problem has been reported so far. Even hull breaches don't affect the encapsulated balsa. Likewise with Swan and Discovery. Every Discovery ever made has a fully cored hull, and all Swans since the early '90's. Not a single known problem with the hull cores (Swan has had some rudders fall off, though).


Considering the rarity of problems with hull cores on modern boats, that leaves cost as the only important disadvantage of cored hulls. But here, you get what you pay for. As Polux pointed out, cheap substitutes for cored hulls, used by the mass production yards, are not very good so far. As to me -- since I care a lot about performance, and good sailing performance requires a light, strong hull, I wouldn't consider buying any GRP boat WITHOUT a fully cored hull.

[Dockhead]

Originally Posted by leftbrainstuff

This so called piece of expert advice requires a firm response by an engineer.

The general statement that cored is better is typical of a comment not based on any evidence.

Lets list some pros and cons

Cored layup
1) cheaper especially for carbon laminate
2) lighter
3) cheaper to manufacture and this has been the big driver since the 70s oil crisis up to today where only high volume manufacturers survive
4) poor penetration resistance
5) subject to delamination of foam to composite interface leading to substantial loss of bending, shear and compression stiffness
6) poor delamination detectability
7) more challenging to repair and meet the original design strength
8) core to laminate interface integrity testing requires destructive testing to validate load derating

Solid layup
1) more expensive
2) heavier
3) can be manufactured and repaired with good quality by relatively low skilled labor
4) much better penetration resistance
5) no loss of shear, bending or compression strength over time
6) issues due blistering readily detectable and can be repaired piecemeal
7) no complicated jigs or fixtures needed to carry out repairs. Self supporting
8) load testing by simple non destructive deflection testing.

In summary cored hulls are cheap and quicker to build and ideal where lightweight for performance is the primary design driver. Or to minimize build cost.

Solid layup for longevity and field repairability.

30 years of building and repairing motorsport and aerospace composites calls bs on the surveyors wisdom.

You are wrong about cost -- cored boat hulls are quite a bit more expensive to build than solid ones. That is why EXPENSIVE boats all have cored hulls, and cheap boats have solid hulls.

You say "especially with carbon laminate" -- huh? Did you ever see a composite carbon structure which was NOT cored? Trying to build a structural element out of solid carbon laminate would defeat the entire purpose of using the expensive material in the first place. I would bet that there has never been a carbon boat hull ever built, which was not fully cored.


You are right of course about penetration resistance. That's why many boats with fully cored hulls have an outer skin of Kevlar (like my boat does). This increases the cost even more, but it is -- well, better. Certainly it is far lighter and stronger.

And you are right about ease of repair in case of a hull breach.

But if you care anything at all about sailing performance, about stiffness of the structure, quiet of the structure, and also about thermal properties of the hull, then the cored hull is the only way to go, and you will pay the extra price and put up with more complex repairs in case you have a hull breach.

Certainly that's the choice which has been made by buyers of all European high end boats, except Oyster, and even Oyster is starting to move slowly to fully cored hulls for their larger and more expensive models.

[robert sailor]

The same surveyor suggests that you should avoid sailboats built with liners. We'll that includes every boat built by the high production yards, Beneteau, Bavaria,Hunter, Catalina and dozens of others. There may be better built boats available but if everyone took his advise 3/4 of the sailors here wouldn't have a boat. Cored hulls when done properly are the best of the best and can not be compared to older thick,high resin construction of the past.
Polux I looked at that ICE 52 and it's a cool boat, it would be a fun boat to sail, a bit weak on the cruising side but more like the racer cruisers of the past. I can see the attraction.

[double u]

the gentlemen might want to read up:
https://www.amazon.co.uk/Surveying-Y...breglass+boats

https://www.amazon.co.uk/Fibreglass-...breglass+boats

https://www.amazon.co.uk/Surveying-F...breglass+boats

https://www.amazon.co.uk/Inspecting-...on+casey+boats

https://www.amazon.co.uk/Your-Own-Bo...dag+pike+boats

[a64pilot]

You guys may not like what Leftbrain said, as I know its like having to listen to the fact that your child is ugly, but he is correct in what he said, cost maybe being what is different, but construction technique, methods and rate of production is what will change that, in fact in high production numbers, cored is cheaper. It may not be in low production rates as labor rate may be the primary driver in cost, but from a materials cost standpoint, he is correct.
And yes, I have seen numerous non cored carbon fiber layups, maybe the most common would be bicycles for example, but I have some carbon fiber aircraft control tubes in my office, which are solid carbon fiber and hollow tubes, no core.
When cored is used in aerospace its never something like foam or balsa or I have never seen it anyway, its usually a honeycomb of some type like Nomex or something, more costly, but even stronger and lighter.

If I really want to go banging around things and want my boat to survive, I want a steel boat, possibly aluminum, but if glass, I want a solid layup, yes it is heavier.
What racing boats are made of and how they are made is about as relevant to me as how a Formula 1 car is built compared to my daily driver.

This is like arguing number of hulls, the Cat guys will never believe anything is superior to a Cat and the mono guys thinks anyone who would sail a Cat is crazy, your not changing either of their minds.

[leftbrainstuff]

Originally Posted by smj

Thank you for your firm response. Now why should I trust your opinion above actual marine professionals that deal with this daily?

I have 3 trades mechanic, toolmaker and aircraft welder. I spent a decade in motorsport in the 80s and 90s as a mechanic / fabricator.

In the 90s I completed a Mech Eng degree followed by a Master of Engineering Science in Materials Welding and Joining then a grad dip in Military Systems Integration in the 2000s.

Throughout my study I worked as a consultant on defence, automotive and motorsport contracts tackling screwups and cant be done jobs.

I've been hands on since I was 13. Thanks to my dad who was Army Transport corp and a diesel mechanic.

All in all I have about 70k hours hands on and I'm still learning. I have a solid grounding in the fundamentals and I design, build and repair anything in metal, composites, plastics, wood, etc. My bs detector is probably my strongest asset.

Just yesterday I TIg welded an articulating joint for my windvane rudder, added directional carbon stiffeners to our hard windscreen project, diagnosed an nmea2k issue and updated some python code for pulling trend data from our electronic ships log.

I currently work for a major cloud company as a managing consultant. Boat work is currently my therapy.

Thanks for asking.

[leftbrainstuff]

Originally Posted by Polux

By your answer I can deduce:

1- you are not a composite engineer.
2- Your boat is an old boat without a cored hull

Regarding price of a cored hull regarding a single skin hull it seems evident that if cored hulls were cheaper to built the boats that are built as cheap as they can be, mass market production boats, they would have cored hulls. But no they haven't, contrary to more expensive sailboats that use cored hulls.

The fact that a cored hull is a way better solution regarding on yacht boat building, due to low weight and much superior stiffness, is the reason why today expensive brands use cored hulls and cheaper boats use single skin.

This was probably written by a composite engineer or designer like they like to be called these days:

"Although the largest market for core is still aerospace — where high-performance aluminum and aramid honeycomb cores are used in aircraft primary structure, as well as in interior panels and floors — honeycombs, foam and balsa wood play a significant role in structural parts for the marine, wind energy and transportation markets. Lightweight, low in density and available at relatively low cost, core materials provide the foundation for incredibly strong and stiff sandwich structures, when placed between skins made with reinforcing fibers and resin. Given the right combination of core, composite skins and adhesive, composite manufacturers can deliver cost-effective sandwich structures to customers in virtually any non-aerospace market where high stiffness and low weight are design priorities."
http://www.compositesworld.com/artic...site-laminates

I have designed, built, tested and certified composite structures for defence, aerospace, automotive and motorsport systems since the mid 80s.

But you are correct I have never held the title composites engineer and yes I have a solid hull with a cored deck and a cored hard dodger. The hull and deck are original. The dodger is my own fibreglass, kevlar and carbon design.

[leftbrainstuff]

Originally Posted by Dockhead

You are wrong about cost -- cored boat hulls are quite a bit more expensive to build than solid ones. That is why EXPENSIVE boats all have cored hulls, and cheap boats have solid hulls.

You say "especially with carbon laminate" -- huh? Did you ever see a composite carbon structure which was NOT cored? Trying to build a structural element out of solid carbon laminate would defeat the entire purpose of using the expensive material in the first place. I would bet that there has never been a carbon boat hull ever built, which was not fully cored.


You are right of course about penetration resistance. That's why many boats with fully cored hulls have an outer skin of Kevlar (like my boat does). This increases the cost even more, but it is -- well, better. Certainly it is far lighter and stronger.

And you are right about ease of repair in case of a hull breach.

But if you care anything at all about sailing performance, about stiffness of the structure, quiet of the structure, and also about thermal properties of the hull, then the cored hull is the only way to go, and you will pay the extra price and put up with more complex repairs in case you have a hull breach.

Certainly that's the choice which has been made by buyers of all European high end boats, except Oyster, and even Oyster is starting to move slowly to fully cored hulls for their larger and more expensive models.

I don't dispute any of your comments. I provided generic comments with no preference for one or the other.

As we move from concepts to specific then often a good case can be made either way.

Each builder will adopt a particular approach and build expertise in that area. It might not be the best academic solution but the real world is where profitability or compliance tend to dominate.

What is clear to me is that the survivability of fiberglass boats since the 60s has been excellent considering this 'new plastic' technology was only expected to survive 5 years.

The older overbuilt boats would send a builder broke in weeks today. Many newer vessels clearly are less tough in terms of their fatigue toughness.

[Polux]

Originally Posted by robert sailor

....
Polux I looked at that ICE 52 and it's a cool boat, it would be a fun boat to sail, a bit weak on the cruising side but more like the racer cruisers of the past. I can see the attraction.

That is quite unfair. I mean "weak in the cruising side."

Fact is that you, even without knowing, tend to judge all boats by the criteria that makes a suitable cruising boat to you. That does not happen with me.

You live aboard full time and that excludes already 95% or more of all cruisers and want also a boat appropriated to sail on cold climates.

That boat is perfectly adequate to sail on high latitudes but in the same way a VOR boat (but much more easy controllable) an adequate boat to do that racing or with a vert sportive crew, just for the fun of it, but certainly not adequate to to that in a leisure way while cruising. Not comfortable due to the
cold exposure.

But in what regards to sail on warm climates, that is what 90% of the cruisers do, including you most of the time, the boat is not only adequate as it is particularly good. Note that sailing in warm climates include not only the med but caribbean as well as sailing between equador and a bit above the tropics, that is where 90% of the circumnavigations are made, not to mention Atlantic crossings.

Note that boat has not only a fully mounted dodger, that you have only to pull back and quickly hold on two points (you can see it on the video), as it can also mount a small bimini while sailing and a lot of options for shade when at anchor.

Note also that it is one of the few 52ft boats that has a garage with enough space to carry a tender fully inflated and that if offers a huge storage space including a sail locker.


Note also that this is a semi custom boats and that they will adapt each boat to any sailors needs and that includes hand holds outside and inside. I talked about that with the engineer and the answer was: "We offer the basic, regarding the rest we found out that demands are very diversified and we prefer to adapt each boat to the costumers needs". It makes sense to me.

This is a two cabin boats with an extra one for storage or in coastal sailing to carry some kids and as so, as a cruisingboat will satisfy the needs of 90% of the cruisers, being in many cases the boat most would want.

You are probably asking yourself how I know that Simply because the ones that manage shipyards are not fool and if they don't offer products that many cruisers want they will go bankrupt and the fact is that there are many cruising boats with similar characteristics as this one, boats that are used for cruising and by cruisers that see in them their ideal cruising boat. Some examples:

https://www.youtube.com/watch?v=Rj5CyhqZ2AY

https://www.youtube.com/watch?v=cKZ0OgRwy18

https://www.youtube.com/watch?v=yXqVsv8D3Dg

https://www.youtube.com/watch?v=1YpjtLGaeYs

https://www.youtube.com/watch?v=kAtmVZm0258

https://www.youtube.com/watch?v=WUibZ5YFCHA

https://www.youtube.com/watch?v=-eHKi868cv4

https://www.youtube.com/watch?v=stK2ePEGmpE

https://www.youtube.com/watch?v=sQDbSCHSWrk

https://www.youtube.com/watch?v=iZWWPn1sJIY

https://www.youtube.com/watch?v=cfIV_jfM0IU

https://www.youtube.com/watch?v=BPKI0Gmb1C0

https://www.youtube.com/watch?v=fL6FXmoVDnY

https://www.youtube.com/watch?v=zs-4xx-gCYM

The fact that there are so much cruising boat offer regarding this type of sailboats means that there are a lot of cruisers that see them as their preferred type of sailboat.

Some of them are Italian, some are french, some are German, some are Danish some are Sweedish, even if some without any reason keep call them med boats, fact is that these boats sail everywhere, from the Baltic (there is even one brand called Baltic) to the Caribbean to around the world, some boats of this type have even been sailed on very high latitude even if not obviously designed to do that comfortably while cruising.

What they are is main market performance boats and the ones that constituted their market are many (including me) but obviously not you. There is a big diference however to say that these boats are a"bit weak on cruising" since all the sailors that constitute their market would not like to cruise any other way.

Sailing while all other sailboats are dead on the water, taking advantage of their excellent performance upwind or to their superior stability dynamic behavior and the pleasure to be at the wheel, not to mention overtaking almost all the boats on the water are characteristics that the sailors that prefer these type of boats trade for a bit more interior space and some more comfort, specially on cold climates.

Not saying at all that these boats are the ideal cruising boats for all, far from that, but I am a bit tired to hear some saying that they are not the perfect cruising boats or that these are med boast. It is obvious that these are the perfect cruising boats for some, me included, but also the perfect boats for many even if obviously not for all.

It should be very boring if all were the same and liked the same type of boats

And yes, of course, all these boats, except the More 55 are on the expensive side and obviously all of them have fully cored hulls.

[Cheechako]

In these discussions there is no "best" really. I think what is often missed is tempering your choice with hierarchy of risk..... and what your personal comfort with risk is. Both trouble, $, and personal risk should be considered.
-When you choose a hull, if you choose an old boat with a bolt on keel, you have higher risk than a boat with a molded keel. Your risk is primarily $, that the keel will subsequently need to be removed and rebedded /rebolted....but brand new boats with bolt on keels have lost them also.
-Cored hulls have the risk that they will have delamination and or wet core issues. It's a real risk, many have had the problem. But sure, you may not.
-Spade rudders are more at risk than supported rudders. They bend, break off, break off leaving a big hole when they take part of the hull with them. A well built one may have lower odds of this problem and you may never experience the problem, but there is risk.


As a sailor I often used the risk factor to make decisions and lessen risks whenever I can; weather predictors lessen risk so I use them. Short cuts thru coral infested shallows, even with good charts and gps, are riskier, so I avoid them. Spade rudders, cored hulls, propane in normal lockers are risks, I avoid them. Etc etc.


Your decisions about risk are different than mine. Act accordingly.

[Polux]

Originally Posted by leftbrainstuff

I don't dispute any of your comments. I provided generic comments with no preference for one or the other.
...

My only beef with you is your comment that a one skin laminate can be better regarding sail yacht boat building and also that in what regards cruising boats it is cheaper to make cored boats than single skin ones.

Evidence shows that the cheapest boats, that are made as cheap as possible, mass production boats have almost all single skin laminated hulls. if it was cheaper to built them cored, they would be cored.

I agree with some of the comments you make regarding advantages of both systems simply the fact that it is possible to make a cored boat much stiffer and much lighter for an equal strength just override them all. Besides there are solutions for most of the weaknesses you point in what regards cored boats.

[double u]

lets not degenerate this thread to a pissing contest please!
1. @interior liners/gridpans: there a many different kinds, some grids (a grid of carlings/stringers & floors) tabbed to the hull - the tabbing can, if difficult, in general be inspected, & the much more difficult to inspect completely closed type that is glued (bogged?) to the hull (gluelines inaccessible)
2.@cored structures: lets not lump a quick-&-dirty balsa/csm-sandwich together with a hightech sandwich made up from unidirectional carbonfibres & very expensive cores.
3.it would be conducive if the owners of cored boats here on the forum would NOT view any negative comments about cored boats as personal insults

[double u]

"...because the ones that manage shipyards are not fool..."
did I miss something in the past 40 years? plenty of fools (& crooks, btw) among them!