Vinylester question

I thought this thread was on vinyl ester.....

Airex has more ductility than Core Cell if that's what you're after. I don't know of too many military marine vessels that are built with either of those though.

I know a lot of race boats built with balsa, which has virtually no ductility. Somehow, it seems to work. Must be magic.

I've also seen a lot of race boats with honeycomb cores, both Nomex and Aluminum. Hmmm, how does that work?

Carbon fiber is extremely brittle. Better not build a boat with it.

Maybe these 'brittle' materials work because they have a lot of history and the boats are properly designed and constructed. Or maybe they are strong and can resist higher loads than ductile materials.

All structural core materials will work fine if the structures are properly designed and built. They all have limitations that must be considered, even Core Cell.

 

Guest
Again I ask the question in the most humble way (ErikG I think would know)....what foam would be the one of choice in highly dynamic conditions such as in Offshore Powerboat racing...

First Off :anyone who would use Honey Comb for the above Be it Aluminum Nomex would be a fool! I have seen it tried!! (In the hull or deck structure) Hell By the time you get enough Filament across it to keep it protected (oop's the bad ole Moment of inertia their mortal enemy) Gees …you could almost have used solid glass!!

Now read c a r e f u l l y…. I said Offshore….. Not a Racing Hydroplane in an 8” chop or an Experimental Airplane…Or an Indy Car..

Name One Boat builder currently using Aluminum Honeycomb in the Hull for the above!! In seawater no less!!! WHO?? This would be good if Seawater some how got in between the Laminations thru a screw hole or the like your boat would fizz and like a small Battery!! Wow Cool.

BTW I saw that Too..

Now as for Balsa and its Pluses: it does in fact handle heat well ….and also is like FREE on the cost side Then again you get what you pay for …BUT it is one the carbon fibers of the core world(and there are many).

Also requiring an inordinate amount of Laminate….. Without it Failure would be instantaneous. BUT You see I said a LIGHT Offshore Powerboat THAT Meaning things Engineered out ….. Not in...

Now do you yourself have any Practical Experience working with Core-cell or Airex?? You sound like a real expert …. Myself I have Some Experience ....and with the various other Core Materials... With a little Racing and High performance and even Military Craft;

So as not to Parrot anything but being able to speak from the real world out there.

In short I know what works and what does not... And there all the while I thought there was a super Core hiding here I Bad !!

I know very well the title of this thread but the discussion has turned to this.

And the Styrene Issue is something Always said by the Purveyors of the Inferior Marine Coreing Materials, They seem to attract the ones who cannot follow even the simplest of instructions.



ab absurdo

 

Heheh

Well I guess your finger pointing at me saying that I would know is... hmm kind a funny. Also I giggle a bit when it was mentioned that the thread actually was about vinylester, as I was the one that originally asked the question two and a hlaf years ago.

I'm still a learner i this vast field of yacht design, what materials to use and how and where to use them.

The Styrene issue is an issue if you use a resin with styrene. I'd prefer to use an epoxi, and preferably a prepreg at that, for oneoff and serious racing craft.
As my personal craft of choice is powered mainly by the wind and not the engine I have yet the jump into the high-profile powerboat pond. But I'll get there eventually...

And FINALLY to my answer of WarWhoops question... Tadaa... I would use CoreCell, the drawbacks that Trevor mentions are all true, but it has the properties that I want. When the time comes and I'll actually will start building (still haven't found the right lottery number yet) I'll use SP systems Sprint prepregs for the hull and deck, and buying directly from SP in England together with the Core. I've been quoted a nice enough price. If that price is still valid when I have enough dogh that's another issue

My 2 swedish krona

 

Erik I have built many one-off’s (Plus winning American and UIM.World titles with them) and NEVER EVER had a STYRENE PROBLEM with Airex or Core-Cell (only a complete FRIGGIN Idiot would do that and plus these are the only core systems to use) BTW I use Dow Vinyl esters Period! (Do not be so quickly oversold on resin systems)

You guys need to join the real world is all! As for the other systems
caveat emptor

 

More about cores

As for offshore racing boats built with honeycomb, how about Playstation or virtually every America's Cup boats? They don't seem to have too much problem fabricating their laminates.. As for telling all the engineers you know about corecell notch sensitivity (which means when you cut your core, be it DC or TC, you loose up to 18% of your shear elongation/strain) go ahead. And while your at it, ask them why ATC uses an ISO test for their shear numbers instead of ASTM C 273..

As for offshore powerboat racers, if the laminate is designed correctly, virtually any core will work (within reason). A majority of the minehunters and coastal patrol vessels built in Scandinavia over the past 20 years use rigid PVC foam in their hulls...probably a bit more demanding than an offshore powerboat hull.

 

As for offshore powerboat racers, if the laminate is designed correctly, virtually any core will work (within reason). A majority of the minehunters and coastal patrol vessels built in Scandinavia over the past 20 years use rigid PVC foam in their hulls...probably a bit more demanding than an offshore powerboat hull.
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Gees I know and they run 150+ MPH hunting mines also. But Actually: You are really really reaching!!
That should be about right you guys 20 years behind in technology Hell there was cross linked PVC believed somewhere on the German Bismarck Battleship...AND WOW Ill bet a US Dollar it took more punishment than an offshore powerboat and a resin bucket Swedish mine hunter, Combined; Also = So what!!

After all it was the very first of the Foams invented what in the late 30's? But really Much better things came along since... Keep up with the times JUST a little! The world has changed dramatically!! Jet Aircraft and all..

And yes you could develop a laminate for JUST about anything (but what kind of an Idiot would do that) if you did not care about the ultimate mass of the project …. these Brittle core’s require a much higher degree of lamination …

and that my friend equals a lot of extra Weight and that would Guarantee a Very non completive Boat! Even if you made the weight break there is always the wacko balance to worry about.

The question remains why anyone in their right MIND would do such a thing when there is much much better modern product’s readily available .I for one cannot fathom that.


I suggest you spend a little time on the subject. Or actually really learn what you are talking about..Before you sit there and prattle off Like in a earler post Doing it and just talking are two different worlds.

Hey I got an real world idea! take the trash you use and hit it with a Drop hammer and watch the instant delamination..

the dc and tc thingy do not belive it because the drop hammer must not know as it just bounces off and since I usally use an A-600 Foam They can not even cut it anyway it just tears out the machines Knives..But it is tough!!

I know what works in reality For the simple reason apperantly unlike you I have Done a lot of light properly cored Boats both Vee Hulls and Cats and Did well ; very well of course experance helps.
so in recap of the core's



abusus non tollit usum

 

Yeah x-linked PVC foam was in the Bismarck, but you don't have to have been around since then to know there's been alot of advances in its technology since then (buy the way the Airex formulation was invented around the same time as the Bismarck foam by the same person).

As far as skin thickness goes, the "more ductile" foam laminates I've seen (but I guess that doesn't mean anything to you anyway) are always waaay too thick (1/4" skins over a 1" core in some cases). Oh yeah, it's because the foam will actually fail in local compression if they aren't. Another problem would be stiffness. Corecell and Airex need thicker skins to attain adequate the stiffness...but then again I haven't seen any of YOUR laminate designs.

I also like how your encourage "testing" of the material in your earlier posts, and I'm sure a boat hull will run into a drop hammer 50 miles offshore. Why not run it over with a forklift, I'm sure you'll see that one in the Atlantic also. By the way, I have done impact tests on the "new" foam, and I've seen in fail also.

I would like to keep the discussion going, but it's obvious to me that you would rather attack my knowledge on the subject than discuss factual details. I'll just put it down as "proffessional differences"..

 

Then you can educate me if you want to

Comparing data is always fun. If youv'e done it already post it here, otherwise I'll attck that mission with full force, after I get home from work

 

Yeah x-linked PVC foam was in the Bismarck, but you don't have to have been around since then to know there's been alot of advances in its technology since then (buy the way the Airex formulation was invented around the same time as the Bismarck foam by the same person).
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Right and the good Doc was was smart enough to find a Sucker to buy the crosslinked system while keeping the Linear…IE Airex

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As far as skin thickness goes, the "more ductile" foam laminates I've seen (but I guess that doesn't mean anything to you anyway) are always waaay too thick (1/4" skins over a 1" core in some cases). Oh yeah, it's because the foam will actually fail in local compression if they aren't. Another problem would be stiffness. Corecell and Airex need thicker skins to attain adequate the stiffness...but then again I haven't seen any of YOUR laminate designs
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Not true!! And you know it!!
You in the real World are the ONE Having to hide from the Moment of Inertia.If you bend that crap it breaks!!

While on the Core educated side we are free to go more with the apparent Moment.

Would not prudent Logic tell you to simply use something that JUST does not break so readily? Like GET this and is buried in the Laminate

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I also like how your encourage "testing" of the material in your earlier posts, and I'm sure a boat hull will run into a drop hammer 50 miles offshore. Why not run it over with a forklift, I'm sure you'll see that one in the Atlantic also. By the way, I have done impact tests on the "new" foam, and I've seen in fail also

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Ok Just why would anyone want a fragile material when there is something better around??

Also once Damage occurs (in the brittle guys) it can continue to migrate thru the Hull. Well at least until the Foams panel edge I would venture to guess.

You did impact tests?? Did you also laminate it yourself?



“I'm sure a boat hull will run into a drop hammer 50 miles offshore”--> This one I just love and had to respond too…
But it would be very nice to have

 

THE SURVIVABILTY if you did strike something Offshore ….would it not ? But I guess someone who would want a Crosslinked Hull would know to Carry with them a very large Pump or even a spare Boat..

What are the factual details ?? Aside from the market share steadily going to the “New Core”


nulli secundus

 

Sandwich Construction

Okay, looks like mr. War Whoop needs a little course in sandwich construction.

First, lets look at strength. If something is strong enough to take a certain load, it doesn't break...right? In sandwich construction, the preferred mode of failure for core materials is shear when in flexure. A crosslinked PVC foam (Divinycell H100) has a shear strength at yield of 193 psi. A similar density SAN foam (Corecell A550) has a shear strength of 164 psi. This means that the PVC foam can take more load (stress, psi) than the SAN before it fails, also known as being stronger in shear. The only difference is failure mode. X-linked PVC fails in a brittle manner, SAN in a ductile (or plastic) manner.

Next is stiffness. In sandwich construction stiffness is measured by the flexural rigidity of the cross section, not just the moment of inertia. Flexural rigidity, D = EI with I = Moment of inertia and E = Elastic (or Young's) moduli of the materials. The moment of interia is created by the geometry of the cross section, or basically how thick the section is. In sandwich construction, this I component is produced from the distance between the skin layers' neutral axis. If this is comprimised, the stiffness of the geometry is also.

The E component is based on the elastic moduli or basic stiffness of the materials in the sandwich. For the core materials, this component is shear modulus. A PVC foam (H100) has a shear modulus of 5800 psi. A comparable SAN foam (A550) has a 5130 psi shear modulus.

When the sandwich as a whole bends, two types of deflections occur, bending and shear. The bending component is due to the skins actually bending with their neutral axis distance being kept constant. The shear deflection is due to the core material shear stiffness. Basically, the lower the shear stiffness of the core, the more it will deflect in shear. When it deflects this way, the distance between the skins neutral axis shortens and the stiffness again decreases.

Again, the PVC foam is able to take more load and deflect less than the SAN foam before failure. Please refer to "The Handbook of Sandwich Construction" by Dan Zenkert if you don't believe me.

As for slamming loads (the main reason for impact tests), these can be designed for with suitable dynamic data (such as Heller and Jasper's work on boat hull wave slamming). Hitting 3" wide sample laminates with a hammer does not replicate waves pounding on a boat hull. In hulls you have large panels which take up the energy of the impact so if one does run into something pointy, the result is a local puncture and not a total delamination. I seem to recall a Divinycell cored boat have another boat run into it in open sea, and it was the competitors boat which suffered the most damage (by the way, that boat, the Illbruck won last years Volvo sailing race AND was completely made with prepreg).

After all this, SAN or PVC, an offshore powerboat hull can be and has been built with either core and perform well, personal preferences aside. Just because someone's been drinking Johannsen's kool aid for so many years doesn't mean PVC foam is crap.

 

One more thing...

Keep the latin sayings for trouty..

 

See what Mr. Brittle is not saying here is the fact that the plotting of Loading and Bending on a simple graph would be a very much different matter entirely ...where we would have equal loading on Mr. Brittles sample and the one that was properly engineered:

It would go Thus the graph on the left side would be the applied load and horizontally from the left to right across the bottom would be deflection.

The results would be as follows as loading begins on the two samples the two lines would go up and to the right correspondingly then oops the loading on Mr. Brittles sample becomes A Net of “0” so we Place a big X the graph at this value. It broke!! But he would say the sea has no graphs or this kind of testing is no good!! Bunk!!

But wait the graph on the Proper sample is still there only from its high value its plot is going horizontal not breaking but bending LIKE WHAT??? A piece of Steel of course it assumed peak load and started deflection!!or bending..

To be blunt I will trust materials that follow Hook’s Law like steel for the above instance. Than Say something from the Mr. Brittles China shop

Now thanks for the dissertation on core values !! But like I said real life : Here was a challenge Like 14 years ago the Project is A Powered (not Blow)Race Boat 11 Meters with nearly a 3 meter Beam a Catamaran offshore Race Boat Projected Speed 122 MPH and 144 with triples Now with almost a Meter of freeboard at say station 5 The Boat fuel tanks everything ready for power had to weigh no more than 488 KG This was an old project but I can do much much better nowadays..

In those days instead of pulling some bogus numbers from Mr Brittles book I did a lot of Material testing I will give you the results the H100 would of made a nice Sanding Block is about all

Now as for Slamming Loads at over 120 tell you what!! you and Jasper hang off the end and feel the slamming of Seawater (64 # Cu’ ) at say 176 FPS Like I said I Personally tested everything (no one knew anyway) and in those days the Airex won Hands down. that and a simple Dow Vinyl ester
Tom was serving Orange that year at the old Torin and BTW I will send you a copy of My Book when it is finished read it as a diversion between gluing your core back together.


As for the racing ;veni vidi vici

 

The only difference is failure mode. X-linked PVC fails in a brittle manner, SAN in a

OK, I think I need to step in here - not for your sakes, but for my own, as I have an axe to grind. ;-)

Whoop - the world does not revolve around stinkpots, so please just live with it. They are fun, true, but so are rag-boats, and they both have failure modes.

tgunderberg is right with his numbers, but he is failing to see what Whoop is failing to point out understandably, which is that the ASTM testing method does not allow the Airex/CoreCell foams to be given credit for what they do, which is to give (deform) and then COME BACK to the same strength and shape they had originally. This is the reason that these foams are so neat, and the reason that WarWhoop likes them so much.
I have to admit that I like them, too. ASTM methods simply regards a movement in the material as a "failure", which shows Airex to be bad, bad, bad. However, if you allow permanent deformation to be the criterion, Airex and Corecell will be ahead.

One of the best-known and best-respected custom builders in RI (and we have a few) will not build a boat using anything but balsa. The guy is a perfectionist, and I cannot persuade him to use anything else. Go figure.....

Steve

 

Sail
Just maybe one day I will Start building something without internal combustion engines as primary propulsion but in the mean time the Flash of the High Performance wins.
And I learned and used some Sailboat building Tricks from Tom (I do respect you guys) which I have used Like tapering the Mass.