Foam cores !! fore and against !! time to share info again !!

Thank you for all that ! just what we need !!Lots of things to make people think about the problems and what caused them !
Most times there is no cure so do it right and properly and these things wont happen !!.
Where are the fibreglass boat builders ? Im talking about people that build with glass and understand all the associated problems that can and will happen if the job is not done the right way .

 

One other thing: Many times the workers are blamed for bad workmanship. If I ask the management what they do in terms of education, they usually fall quiet.

Boatbuilding does not need professionals, it needs TRAINED professionals. They need to know what is being expected from the build. Only if all goes well and good quality boats are produces, one can start cutting some corners, to increase profit. Theys cuts can only be made in tight cooperation with both material suppliers, management and workers. (and that is usually where I jump in, as a supplier, as the company I work for has a very broad range of materials.)

 

One issue for us cold weather/fresh water boaters is freezing. As yachtsurvey.com says:

"this does not mean that the cored area cannot take up water for the small gaps between the blocks of foam contains plenty of air spaces which, unless vacuumed bagged, do not get filled with resin."

Now what happens when this water freezes, thaws, refills and refreezes for 10 years? Bigger every year?

I have a small boat with deck delamination that I'm pretty sure is caused by condensation on the underside (because the deck cools via radiation at night) getting into the deck and freezing. Air pressure changes in the sealed hulls might also contribute to pushing the condensation up into the deck.

 

My family built a 53 ft foam sandwich yacht in the the late 1970's. Airex and polyester were the materials. It is still afloat and in fine condition today, over 30 years later.

I think one point that it is important is to differentiate between is the two main methods of foam construction: moulded and mouldless.

We used mouldless construction, i.e. we built a shaped wooden framework (sacrificial) and then clad the shape in sheets of Airex foam. We had constructed separately, a solid glass keel and skeg (Keel big enough to hold 8 ton of encapsulated lead)and put that on top of the frame work. Lead added afterwards!
All external laminates followed, going right over the keel, using uni-directional woven rovings, both athwartships and longitudinally.
It was very easy to see if complete bonding had not taken place as tiny air bubbles were visible in the first layer, while curing. If bad, they could be cleaned out and then relaminated with the second layer layer of chopped strand mat (csm), or uni. The problem was styrene absorbtion by the Airex, just as the resin was going off. It was not hard to get round this problem and I doubt whether the occasional 2/3mm diameter air pockets would have been structurally significant. Of course, when it is your own boat you get rid of every single one. The final stage was fairing and painting which took quite a while but provided us with a "near" mould finish.
The boat was turned the right way up and then small sections of the frame work were cut out and a single csm laminated. The hull then became completely rigid in those areas. It was rather similar, in principle, to underpinning a house i.e alternating areas and then waiting a few days and then doing more.

The point I would make is that with some of the other moulded methods, you cannot see if the foam bond is good. Some of the mould methods must be more difficult to assess, perhaps ultrasound etc can tell, but this is always after the event and you will have to remove the foam to repair the area, rather than a little local work. I am probably way out of date on the other methods but I can speak with complete confidence about the method we used. We had Derek Kelsall as our consultant. The same method was used by a Round the World yacht GB II now called Whitbread Heritage. (Built 1973 and still going strong, she used denser foam than us) She was built by Chay Blyth and Derek Kelsall. Very long and thin with a lot of flexing going on, in a seaway, I was told. Also as she was slim and without deep sections so when the rigging was tightened up the bow and stern came up a few inches and a ripple appeared across her deck! I believe thay put some logitudinal deck beams in to reinforce this area, as a precaution.
So, even with "panting" in a seaway, hard use over near 40 years for GBII and in our case over 30 years, no delamination. No water absorbtion found. I still have hatch and hull core sample somewhere and they were in excellent condition when I last looked. We had a little osmosis in the solid glass keel area but that was easily fixed. Our biggest problem was slight delamination of areas of filler underwater (3-5mm in diameter). This was scraped back and re-filled with epoxy fill, rather than the original polyester and microsphere based fill. this seems to have solved that, (Twenty years ago)

I don't want to bore everyone with this info, but I can supply much more, if wanted.

One small plea......
I am occasionally astonished by how rude, unpleasant and personal a few of the replies are. No-one would do this face to face, even if the question was idiotic. I wonder if the web gives some people feel a sense of separation from the rest humanity and behave in a way they never would dream of, under normal circumstances of conversation. Perhaps if the geographic origin of the unpleasant ones is established, then it may be possible to identify a reason.... something in the water perhaps?
Sorry to have inflicted so much reading on you.... and typing on me.

 

I told you! Fill the kerfs!

Decks are less likely to have been made with scrimmed foam (blocks on a glass fabric). Water might also have entered through one of the many fittings installed on the deck.

 

This is one of the reasons i started this particular thread !
What happens in one part of the world like freezing tempratures you have problems that others never ever experiance or know anything about .Sure in nz we get frosts but not he huge minus -15 c like other places in the world get for prolonged periods of time .
While spending a winter in South Korea with regular minus -12c to -15c for a few weeks i encountered problems i had never seem before , epoxys that crystilized and never hardened and when they did warm went like chewing gum and stayed like it for days .
On the other end of the scale working in Tahiti with Lows of +28c in there winter and highs of +36c later in the year ,again problems that i had to find out about first hand . Resin drainage like i had never exsperianced so having to solve that one with quick gelling catalyst but slow curing and mixing two kinds together to get the magic formular .
Learning should never stop !!
What one person does on a dayly basis and takes for granted others are trying to lean first time , its the passing on of knowledge and exsperiances thats important !!.

 

I feel there is a place throughout the whole industry for Skilled , trained , and proffessional Fibreglass boat builders . The days of low wages and treating laminaters as second class individuals is fast approaching a show down .Boat building in Fibreglass is a very skilled job and like all other parts of the industry one has to have a wide range of specialized skills to perform there job properly .It covers knowledge of a wide and varied range of chemicals and the procise mixing of to match the ever changing enviroment they are working in , A high degree of composite engineering and understanding of the materials that has been specified for a particular job . A complete understanding of the processes involved to work with and fit in place of the big range of fibre products that are being specified and used these days .Some products specified buy a button pushing computerwise clever Composite engineer are not practical for some jobs and it takes a clever and work wise laminater to recognise this and do something about it before it is to late .
The mistakes at this early stage of construction may not show up for months down the track even once a boat has been used for a time .
A freak wave , a nidge into a wharf or a pile and the unseen damage that sits waiting for the next trip into a rough sea , then the relentless working of the waves on the weakened part and progessively distruction takes place and ends in disaster .

Some one will look at what i have written an poo poo just about everything here BUT its true .

I started off in the fibreglass industry 30 years back and knew nothing at all . The fibreglass industry has splintered off into all kinds of areas and it would take a whole life time to even get a small understanding of what is out there now in all parts of the industries not just the marine part of it .
But it is the basic understanding of everyday simple things that are not being drummed into the young workers from day one so they have a good grounding to carry with then throughout there career in the glassing industries .
Recent years this has been so evident as i have gone and worked in differant companies in differant parts of the world because they were having problems and needed to be shown how to work with the newer and more up to date materials and processes .

 

well, the laminating itself is easy, everyone can do that.
laminating neatly is a bit harder, but still doable with very little practice.
then comes the core. I see it going wrong almost weekly.( ductape and wooden sticks to hold in place, you should have seen it..at least it hadn't kerfs)
Last week I had to bevel the edges on a blocked core with scrim. scrim side up, blocks got everywhere, and the core looked like a mashed up puzzle. I asked 3 times if they where sure, they where... but next time, I'm doing it my way .
fibre orientation is also hard for some people.
And then there is the assembly....

laminating is easy, but there are a lot of things you can screw up besides that.

 

There is 2 approaches:

A management which instruct their (hopefully) skilled workers "build a boat!"

Lets hope the skilled workers have enough info and skill to produce a boat, control the laminates, gelcoat thickness, core installation, etc.
When something is wrong, people get yelled at.

Although I take it a bit over the edge, this is what happens in many places. Builders like that are vulnerable. It is easy for workers to leave, and then the knowledge is gone as well.

There is the second type, which is more "airplane manufacturer style". Boats are divided in several sections or subassemblies, books are available on the exact process, and every step in the process, including things to look at, illustrated with pictures, has to be signed off. Workers might be less knowledgable, but well trained on the specific job they do. If they run away, someone else can jump in with only a short learning time.

This usually is more suitable for larger volume boat builders, although an educated guess it that even a series of 5 would justify the extra effort in putting documents together. (depends on many variables, though)

I do not have an opinion on either way of working, but what is true in both types, is that workers need to be instructed clearly and they need to know exactly what is being expected from them. I miss that at times.

Above is true for laminating (really, I have seen guys with more resin in their hair then in the laminate), core installation (remember builder "X" which I mentioned before) and in all other building steps.

 

As for core installation: toothpicks are used regularly, and are not that bad. There is also a product from Airtech which is called "tackstrip" which can hold things together, and can be laminated over.

Bevel edges: do that after the foam is glued in..... Saves a puzzle.

Fiber orientation: a good sketch of the boat, and all its layers is helpful. (management "type 2")

 

Laminating looks easy !!!

I hear exactly what you are saying and have been and seen just what you are talking about . In my experiances Management wants shooting . Even most of the factory management including the forman are as useless as **** on a bull and thats where all athe problems stem from .
All the places i have worked as a laminating shop manager i always spent at least one day every week working on the floor , overalls on hanging on a grinder , hanging on a chopper gun , spraying gel coat , waxing moulds and or general cleaning etc etc I would never exspect any of the guys i work with to do any job i had not done or would not do myself . Sitting in a office chatting on the phone , yapping to the office girls and hob nobbing is not my thing !.
We also introduced Glide time and tea breaks and lunch was anytime during the day with not at set or fixed times , this worked really well and never got abused ever . Before anything like that was introduced i sat a talked to everyone and we discused it and it was there choice if every one want it or not .
Laminating and laying cores i was always there walking around watching and seeing first hand what everyone was doing and how the job was being done .
Its also a good way to see first hand what everyones capabilities are right from the leading hand to the newest recruits . When you see a weakness in some area then you are able to do something about upskilling and looking for a better way .
The maintinance and care of equipment being used was a hot issue as well , well used but well cared for gear always works and keeps on working so nothing breaks down partway through any job .The last half hour of each day was devoted to collecting all tools and gear cleaning , oiling , changing discs , wiping and cleaning everything ready for the next day , also talking about the work schedual for the next days work . Also chatting amongst ourselves to see if there was any one that was likely to have a day off work for any reason .We all had families and there are times when guys wanted a day to do what ever , being honest and up front was never a issue and the loyalty shown was really great .
Companies get what they give ! if nothing is given then what else can you exspect . It carries all the way down the chain of comand to the shop floor .I came from the floor and seen and listen to the rude and abusive comments from other trades within the company many times. When i finally got to management level i was able to do something about it and i did !.

Simply put you get what you give !

 

Great resume! Is this a job interview or a discussion about foam cores?

 

sorry am a little passionate about what i do !! You got any jobs going ??

Over the years i have simply walked out of a few companies leaving them to there bad work ethics , attitudes and antiquanted work habits and ways of working !!

 

Was sitting with a main instructor of Westland Helicopters and Agusta Helicopters carbon fiber layup branches yesterday (in fact we sailed the past week together).

The books are more often than not written by armchair engineers. Impressive. Sometimes the output is 80% landfill... That is Aircraft industry!
The test panels of cored bottom have been 1 out of 18 coming out to sufficient properties. In a case happening quite recently.

I am by no means fighting against sandwich construction, but may I ask, where my Peers have you seen a similar (to Helicopter canopy or rotor producing) manufacturing setup in our industry? Not even I go that length.

Foam cores in cruising boats and yachts hulls are a crime! A violence of all proven seamanship and boatbuilding skills.

Foam cores in cruisers hulls have to be treated like childs abuse, lifelong in prison.

How can one (well aware of the weakness of his workforce, conditions, materials, and not knowing the max. stresses of useage) promote cores for a cruiser?
That is insane.
Again, have a nice read:
http://www.yachtsurvey.com/sinking_of_Bertram_630_Absolutely.htm
and don´t forget all the related articles!

I produce up to 46 meter boats at present (mixed matrix, VE resin), cores are (except for some parts on the super) not allowed.
The next generation will not even be done in VE anymore, we use EP in a massive layup, postcuring the entire hull / deck. Cored structures are not allowed in any of the parts, not even the sundeck awning.

According to our (five times crosswise calculated by indepentant NA´s) books, we will come out with a weight penalty of about 3 -5 % --------

I dare to laugh............

The average client has a hard day to decide between the 3600kW and the 5000kW installations. And we have a problem with 5% additional weight?
Then these senseless monsters sit at the moorings and look impressive. And none of the owners has ever takin them on a shake down run. Let alone a real cruise.

Ships have to stand sea conditions, for years and decades, and then some time.

WE,
the designers and builders have the non disputable responsibility of the lives on our craft. No cert. or class body takes away that duty. It is insane to risk a single life in case one would take the ads for true and go to sea with our vessels. Get it, we have it in our hands.

Leave the core crap on cruisers!



Racers, yes, they need to save every gram.

Äh, we processed 1800 metric tonnes of Epoxy and Ve resins in 2009, and (I did not know that) 0,8 tonnes of PVC foam as well. (thats a lot, I have to reduce that).

Richard

 

Why do windmill blades stay intact? (except for lightning strikes, which can kill them, even with the protection that is built in)

These are all cored construction, in a sensible and controlled way.

Construction books should not be 80% crap. A boat manufacturer I worked at had a quite complicated layup of his laminate. He was the only one that knew where he wanted which fabric, and how it should be cut in place.
I did a couple of laminations with him, and I cut the process in 8 easy to follow steps. I made sketches of those 8 steps, printed them on A3 paper, numbered them, and pinned them on the wall. This was 1997. These sketches are still hanging there, and are being used. The shop owner does not need to be present anymore at the laminating. It can be that simple.

Oh, and one next deviation from cores, but related to the text by tunnels:

If you ever run into a management position of a higher output composite manufacturer, let the guys that do the demoulding, also do the waxing. In management type 1 (scream and shout) companies, this is to let the waxers also clean up the **** they create.
In management type 2 (instruct and organise) this is to keep the moulds in good shape. The demoulders know exactly which part of the mould might need extra attention. It saves a (costly) communication step.

-----

Back to cores:
@ Richard, can you tell me by example what you are against with cores? Can you suggest an easy to do construction method for DIY builders that for some reason do not like to work with wood?

@ tunnels (what is your name anyway?). Which cored boats have you built, and what problems did you encounter, both technical and perhaps problems like finding skilled people, etc.