Subject: [harryproa] Re: masts
From: "proabuilder" <arttuheinonen@heinoset.net>
Date: 11/8/2006, 12:32 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

Hi,

What makes nanotubes more interesting for us is that
nanoepoxy is not that expensive. You can buy it at less than 20e/kg
if you buy a barrel. Explanation:
only few percents of nanotubes are needed to give good properties.
I think that price is too bad for making a mast where all properties
are critical.
Tour de France winner 2006 bicycle was made of nanoepoxy-carbon
composite. At the moment a finnish boatyard is making a luxury yacht
hull in nanoepoxy-carbon composite, they use resin infusion method so
it might work for us too.


regards,

proabuilder



--- In harryproa@yahoogroups.com.au, "Myriam & Youri" <wangka@s...>
wrote:
>
> Dear Mike, Peter, and maybe others ...

> Could you please have a look at the attached excerpt from
www.matweb.com where you can find material properties for most
materials among others carbon fiber, these are for Hexcel fibres an
important manufacturer of carbon fibres. Zoltech and others will show
up data that are strongly in the neighbourhood ...
> As you can see elongation @ break is little less than 2% ... for
high-strength carbon fibers not the high-modulus fibres that go down
to 0.6% to 0.8 %.

> Youngs modulus is a ratio of ratios  namely (tensional) stress
and strain :

>             E = σ/"
> With σ being  F/A force (Newton) divided by area (mm2) and  ε
being ΛL/Lo length difference/original length.

> Algebra gives me ΛL = F*Lo/E*A

> If you take A to be 1 mm then MPa eguals N/mm
>                 Lo to be 100 p.e mm to get the solution in %
>                 And F to be ultimate tensile strength
> Then F*100/E = ΛL  ΛL being the elongation @ break.
> Maybe try it out on the matweb data...

> At the moment we are finishing research on epoxy laminating systems
and reinforcements and pre-pregs available for marine purposes.
> Not only tensile also compressive, but also important shear and
ILSS (inter laminar shear strength).
> We will be make FE-studies on the relevant possibilities during the
weeks to come ...

> If you want we can keep you informed on our investigations ...

> Carbon nanotubes look very promising, but prices over here are
around 25 to 40 EUR/gram.

> Best regards,

> Myriam & Youri
> Wangka bvba
> Belgium

> e-mail. info@w...
> web. www.wangkaboats.eu

> -----Oorspronkelijk bericht-----
> Van: harryproa@yahoogroups.com.au
[mailto:harryproa@yahoogroups.com.au] Namens Peter Southwood
> Verzonden: dinsdag 7 november 2006 13:07
> Aan: harryproa@yahoogroups.com.au
> Onderwerp: Re: [harryproa] Re: masts

> Mike,
> You give me more credit than I deserve, but I think it is beacause
you misunderstood my point.
> I did not know that epoxy has different modulus in tension and
compression, and it is very interesting that it does.
> What I said is that the strain to failure and ultimate stress will
differ in tension and compression, and most importantly, what you
mention now about the different elongation (strain) at failure
between the matrix (around 2%) and the carbon fibre (around 10%,
which is an astonishingly high figure!)
> A matrix with elongation nearer the fibre value would improve the
material immensely. So much of the fibre strength is basically wasted
when the matrix fails so soon
> I agree with your summation on scenario A, which is basically what
I was saying.
> I will look at the others more closely before commenting.
> Cheers,
> Peter
> ----- Original Message -----
> From: Mike Crawford <mailto:jmichael@g...> 
> To: harryproa@yahoogroups.com.au
> Sent: Monday, November 06, 2006 11:44 PM
> Subject: [harryproa] Re: masts

>
>   After much research, I agree with both Peter and Rob.
>
>   In summary:  epoxy cracking likely occurs in first tension on the
leading edge, while structural failure of the mast likely occurs in
compression on the trailing edge.  The cracking sound will probably
be more of an issue for carbon and less of an issue for kiri/glass.  
Also, it appears that  Rob's cold vacuum process for creating spars
is superior to the heated autoclave process, and carbon and kevlar
laminates are better than aluminum in terms of long-term fatigue.
>
>   The rest of this long post contains some of the links and
explanation.  It's not definitive, but at least it has some real data.
>
> ---
>
> EPOXY PROPERTIES
>
>   I originally made two faulty assumptions:  a) epoxy stretches
more than it actually does, and b) epoxy is isotropic, i.e., it has
the same modulus in both compression and tension.  The first
assumption stemmed from the fact that the flexible epoxies used in
some repair work are different from the stiff epoxies used to create
masts.  The second assumption came from some research refers to
epoxies as being quasi-isotropic, which I misinterpreted.
>
>   Thanks to Peter for pointing out that epoxy has different modulii
for tension and compression.  Unfortunately it took me over half a
day to get actual numbers to verify this.
>
>   As far as stretch goes:
>
>     http://www.tech.plym.ac.uk/sme/MATS324/MATS324A5%20CFI.htm
>
>     Epoxy only elongates to 2% before cracking, while carbon fiber
can elongate up to 10% before failure, and E-glass to 3.37%.  As the
leading edge of a mast stretches, the epoxy will crack before carbon
fibers or E-glass fibers will break.
>
>   As far as modulus goes:
>
>     http://www.rpi.edu/locker/38/001238/pdfs/load.pdf
>     http://www.google.com/search?
q=cache::www.rpi.edu/locker/38/001238/pdfs/load.pdf
>     (same as above, but html version)
>
>   Epoxy alone has a modulus that is 17% greater in compression than
in tension, and an epoxy/carbon composite has a modulus that is 21%
greater in compression than in tension.  Both epoxy and epoxy/carbon
composite will stretch more under a given force in tension than they
will shrink under the same force in compression.
>
> ---
>
> MAST CRACKING
>
> Scenario A: flexible unstayed carbon mast
>
>   If the mast is designed to be flexible, the smaller tension
modulus means that the windward side of the mast will stretch more in
tension than the leeward side will shrink in compression, and epoxy's
earlier failure due to strain means that the stretching is going to
crack the epoxy while leaving the carbon fibers intact.  These cracks
will weaken the mast, but won't themselves represent a structural
failure because the undamaged carbon is still very strong.
>
> Scenario B: stiff unstayed carbon mast
>
>   If the mast is stiff enough to keep the epoxy from elongating
past its strain limit, cracks won't occur in tension on that windward
edge.  Instead, cracks will develop from compression in the leeward
edge as the matrix starts to buckle.  This is not necessarily better
than the flexible mast, just different.
>
> Scenario C: kiri/glass mast
>
>   Because of wood's inherent flexibility, and the lower modulus of
fiberglass when compared to carbon, the cracking is likely in the
epoxy on the windward edge.  I don't have a modulus or strain data
for kiri to test this.
>
> ---
>
> MAST FAILURE
>
>    When a failure does occur, it will likely happen on the leeward
edge under compression.  This is because the fibers under tension
require no support, and therefore don't put buckling stress on the
matrix, while the fibers under compression will eventually buckle
once the epoxy fails to keep them in column.  Worded differently, the
compressed side is stiffer than the stretched side, but ultimately
more susceptible to failure.
>
> Scenario A: flexible unstayed carbon mast
>
>   This mast will provide warning before failure, with the leading
edge cracking before the trailing edge buckles. That's definitely a
plus.  However, the cracks will weaken the mast over time  The more
cracks there are in the epoxy matrix, the less it will be able to
keep the fibers from buckling, and the more likely it will fail in
compression.  Moral of the story: avoid stresses that cause the
cracking sound.
>
> Scenario B: stiff unstayed carbon mast
>
>   For a stiff carbon mast, this means that there won't be the
benefit of hearing the micro-cracks in the leading edge as the mast
gets stressed.  That's a bummer if the mast has not been designed to
be strong enough to handle the dynamic loads involved in a huge gust
capsizing the boat.  If the mast is strong enough, the issue then
becomes making the boat strong enough to handle the stress, while
also surviving the knockdown.  Many folks would rather have the mast
fail.
>
> Scenario C: kiri/glass mast
>
>   Failure will likely be in compression because wood does better in
tension than compression, and a hollow mast will eventually buckle in
compression when subjected to too much force.  Fortunately, the
cracking should be less of an issue with the kiri/glass mast.  First,
the kiri itself is going to provide more resistance to compression
than the glass/epoxy skin.  Second, even if the epoxy is cracked, the
glass will still hold tension, and will still help prevent the kiri
from buckling.
>
> ---
>
> VACUUM-BAGGING VERSUS AUTOCLAVE
>
>     http://www.gmtcomposites.com/the_autoclave_myth.htm
>
>   Autoclaved prepreg masts are stronger and stiffer in tension and
compression, while vacuum bagged masts are better in shear.  Six on
one side, a half-dozen on the other.  However, vacuum-bagged masts
can be made in one long piece, regardless of length.  Autoclaved
masts, on the other hand, must be spliced together from sections that
fit in the autoclave.  For a small mast, this doesn't matter.  For a
large mast, this means joints between sections, and that's less
desirable than a single piece.
>
> ---
>
> FATIGUE
>
>     http://www.tech.plym.ac.uk/sme/MATS324/MATS324A5%20CFI.htm
>
>   "Under a static load of 50% ultimate stress, the probability of
survival for carbon/epoxy, Kevlar/epoxy and glass/epoxy over a 30
year period are 99.99%, 99.8% and 22% respectively.  Under a load of
40% ultimate stress, the survival probability for glass/epoxy is 97%"
>
>     http://www.cstcomposites.com/505_carbon_spar.htm
>
>   "Fatigue resistance orders of magnitude better than
Aluminium  .Life Span - pretty well indefinite with normal sailing
loads apart from normal wear and tear."
>
>   Not that anyone needed a reason to like carbon.  I've just seen
fans of aluminum insulting carbon's ability to resist fatigue.  I
suppose early designs could have had problems, but that would seem to
be a design or manufacturing issue, not a materials issue.
>
>        - Mike
>
>
>
>
> Peter Southwood wrote:
> Hi Rob,
> I dont see why the resin should crack because the carbon is
stiffer. If the resin cracks it is because it is stressed beyond its
maximum strength. The stiffer the fibres, the less likely the resin
is to reach failure strain before the fibres. More likely the resin
cracks because it is too stiff for the fibres and does not have a
matching strain at failure.
> Cheers,
> Peter
> ----- Original Message -----
> From: Rob Denney <mailto:proa@i...> 
> To: harryproa@yahoogroups.com.au
> Sent: Friday, November 03, 2006 7:23 AM
> Subject: Re: [harryproa] Re: masts

> G'day,
> Yes, but the stiffer it is, the more cracking there will be.  My
understanding of this is that the noise is the resin cracking as the
carbon is so much stiffer.  With glass and kiri, there may be less
cracking, or it may just happen at a higher load.  Regardless, I
think you will get plenty of warning.  Maybe test a piece of kiri and
glass by bending it until it starts to crack, then see how much more
it will take before it is visibly damaged.  This may give you some
idea of how far you can go past the cracking stage.

> regards,
>
> Rob
> ----- Original Message -----
> From: Doug Haines <mailto:doha720@y...> 
> To: harryproa@yahoogroups.com.au
> Sent: Friday, November 03, 2006 1:13 PM
> Subject: Re: [harryproa] Re: masts

> Rob,

> Is composite glass/kiri?

> Doug

>
>
> Rob Denney <proa@i...> wrote:
> If it is composite, you will hear a lot of creaking and cracking
before it breaks.  I would work on one of them doing the lifting as
in a capsize you will probably have dumped one of them.

> regards,
>
> Rob
> ----- Original Message -----
> From: Doug Haines <mailto:doha720@y...> 
> To: harryproa@yahoogroups.com.au
> Sent: Thursday, November 02, 2006 12:13 PM
> Subject: Re: [harryproa] Re: masts

> Robert,

> I'd like to sense a failure ahead of the crack, split whatever, so
as to salvage the mast and simply add more glass around the outside.
But that would be a fairly satisfactory level of strength if they -
cause there are two of them - raise the hull.

> Doug
>
> Robert <cateran1949@y...> wrote:
> Easy enough to check if the masts are strong enough. Load them up
by
> trying to lift the ww hull with a 100kg weight sitting on it.
> I was looking at the characteristics of quality bamboo section and
it
> looks considerable better than glass weight for weight with 4GPa
> youngs modulus and a breaking strain of 30kg/mm 2. It may be worth
> considering for cheap masts. I am considering it myself for
skinning
> cores in areas where exra stiffness is wanted without the expense
of
> carbon. Hope carbon becomes more easily available and cheaper as it
> is by far the best material.
> Robert
> -- In harryproa@yahoogroups.com.au, "Robert" 
<mailto:cateran1949@y...> <cateran1949@y...> wrote:
> >
> > --- In harryproa@yahoogroups.com.au, Doug Haines 
<mailto:doha720@y...> <doha720@y...>
> wrote:
> > >
> > > Hi,
> > >   
> > >   Just meant swinging around on the water, like anchored in the
> sea
> > breeze comes in 20knots.
> > >   
> > >   I was wondering about general ideas about swinging around
> coming
> > from experienced multihullers out there. Like when you anchor a
> > bigger boat out further where the wind is. What about two anchors
> 30
> > degrees apart?
> > >   
> > >   Mast is same as boat - kiri strip and glass.
> > >   I've tapered the tops to half dimensions. There is a round
pole
> > up a metre and a half into the mast that slots in the hull. I
hope
> it
> > is all not going to break.
> > >   Obviously it is heavy but is cheaper.
> > >   
> > >   Doug
> > >   
> > >   
> > >  
> > > Myriam & Youri  <mailto:wangka@s...> <wangka@s...> wrote:
> > >        
> > >
> > >     v\:* {behavior:url(#default#VML);}  o\:* {behavior:url
> > (#default#VML);}  w\:* {behavior:url(#default#VML);}  .shape
> > {behavior:url(#default#VML);}        st1\:*{behavior:url
> > (#default#ieooui) }                Dear Doug,
> > >   
> > >   
> > >     Dear Wangkas,
> > >
> > >     
> > >
> > >     Nice pictures and all, but where is a finished sailing boat?
> > >               We know it takes a long time, but sometimes we
have
> > other worries on our minds ... like carbon spars for classical
yachts
> > where we have to sort out two boats, masts, booms, sprits, poles
> > etc,  we have to make molds and plugs for rudders, keels and
bulbs,
> ...
> > for the carbon parts we are achieving and testing  a construction
> > method VAPM (vacuum assisted pressure molding that gives us
> autoclave
> > quality laminates (not only on the voids ratio but also on the
> > compression side) in our pressure molds( compression +-5 Bars)
> which
> > can produce one piece parts, which is not possible by standard
> > autoclave procedures. We are also currently testing a method for
> > direct CNC mold cutting for parts construction ...
> > >
> > >     Also, what do you hope to acheive with around beam?
> > >
> > >      They are not only rounded in length but also elliptical in
> > section and will be constructed VAPM... less windage, better
stress
> > distribution, less wave interference ...
> > >
> > >     Thanks again for your mast section, it is coming together.
> > >               We are glad, how are you going to construct
it ? ...
> > >
> > >     The boat really swings around at the moment without masts
up
> > and I wonder if it can be helped? More a question for the
cruising
> > boaters - do you plan doing cruising Elementarries?
> > >               What do you mean with swinging around ? I suspect
> we
> > will but that depends on the interest shown ... for the moment we
> have
> > some asks for quotes from France, Switzerland and Germany ...
> > >   
> > >   
> > >   Best regards,
> > >   
> > >   
> > >   Myriam & Youri
> > >   Wangka bvba
> > >   Belgium
> > >   
> > >   e-mail. info@w...
> > >   web. www.wangkaboats.eu
> > >   
> > >   
> > >   
> > >
> > >     
> > >
> > >     yaendenboom  <mailto:wangka@s...> <wangka@s...> wrote:
> > >
> > >     Dear people,
> > >
> > > Our site has been updated.
> > > We kindly invite you to have a look at:
> > >     www.wangkaboats.eu
> > >
> > > Suggestions and criticism is welcome at:
> > >     info@w...
> > >
> > > Thank you very much,
> > >
> > > Myriam & Youri
> > > Wangka bvba
> > > Belgium
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >   
> > >    Send instant messages to your online friends
> > http://uk.messenger.yahoo.com <http://uk.messenger.yahoo.com/>  
> > >
> > > 
> > >
> > >  Send instant messages to your online friends
> > http://uk.messenger.yahoo.com <http://uk.messenger.yahoo.com/>
> > >
> >
>
>
>

> Send instant messages to your online friends
http://uk.messenger.yahoo.com
>
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