Subject: Re: [harryproa] Re: masts
From: "Rob Denney" <proa@iinet.net.au>
Date: 11/1/2006, 9:18 AM
To:
Reply-to:
harryproa@yahoogroups.com.au

G'day,
 
You are right (and I am wrong) about 2 masts vs one.  The stiffness and the strength are different, and it is the strength which needs to be enough to tip the boat over on either mast of a schooner.  I will redo some of my calculations for the bigger boats.
 
Not so sure about the load attachments to test the mast, but no doubt if there are 5 attachments to the top half and it tips the boat over, the mast will not break in normal use.    
 
Re carbon tow at $30/kg.  The actual mast is made up of about 60% carbon and 40% resin.  The resin costs about $13 per kg so the actual mast cost is considerably less.  There is also a lot less wastage than with a wooden mast, which also needs glassing for protection, but this adds nothing to the stiffness.
 
regards,
 
Rob
----- Original Message -----
From: Robert
To: harryproa@yahoogroups.com.au
Sent: Wednesday, November 01, 2006 11:41 AM
Subject: [harryproa] Re: masts

-I would have thought that with the safety factor needed for gusts
and wave actions it wouldn't need quite that level of load spreading.
The mast has to be able to handle gusts while in a wave trough at the
same time as being jerked around by chop. I would have thought that
just a spread load for the top half would be enough., especially as
that is where the moments are. By the way, working on the figures for
loadings on masts makes me more impressed by the Visionarry mast.

My calculations though, don't come out as two una rigs weighing that
much more than a single rig of the same area when the extra stiffness
required for  working sail area of the taller rig are considered. Add
30% to the top of the mast with the same taper and there is nothing
left to attach a halliard to.  The short masts need to have enough
strength each to be able to lift the ww hull and therefore the bottom
2m need to be about the same, but only need to have enough stiffness
to carry half that load of working sail. I am not sure how much extra
weight is needed to give that stiffness for the taller mast or
whether it is a natural consequence of the materials stiffness to
strength ratio. If the latter I can see the extra 30-40% weight of
the two mast set up. I see the main advantage of a single rig is
catching cleaner air in light conditons, rather than weight.
regards,
robert
-- In harryproa@yahoogroups.com.au, "Rob Denney" <proa@i...> wrote:
>
> G'day,
>
> Not that easy as the pulling load has to be evenly distributed
along the mast.  Needs a lot of pulleys so that the single load can
be dissipated to minimum 10 points along the mast. 
>
> regards,
>
> Rob----- Original Message -----
>   From: Robert
>   To: harryproa@yahoogroups.com.au
>   Sent: Tuesday, October 31, 2006 4:38 PM
>   Subject: [harryproa] Re: masts
>
>
>   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" <cateran1949@y...>
wrote:
>   >
>   > --- In harryproa@yahoogroups.com.au, Doug Haines <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 <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 <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 
>   > >
>   > > 
>   > >
>   > >  Send instant messages to your online friends
>   > http://uk.messenger.yahoo.com
>   > >
>   >
>
>
>
>   
>
>
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