Subject: Re: [harryproa] Schooner rig and VHF/AIS
From: "Rob Denney harryproa@gmail.com [harryproa]" <harryproa@yahoogroups.com.au>
Date: 4/29/2020, 12:52 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 



On Sun, Apr 26, 2020 at 2:09 AM a8b7k57g@protonmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:
 


PICS!
Will do.   Attached is a screen shot of what i am thinking of.  The blue and grey corrugations are glued together, probably during the cure of the grey sheet, then if required, the red flat sheets are laminated on each side.  Lots of variations with fibre direction and type, and on long skinny hulls whether corrugations in both directions are required.  Big problem for hulls is how to infuse it all in one shot.   However, as I am not paying for labour, it may be worth doing it in multiple shots to reduce costs.  

Rob, what are the economics of this? Even with zeroing labour...

You have 4 sheets of glass and resin, but 2 are corrugated, so add 10% to that surface area. = 4.2 m^2 of whatever GSM glass, plus whatever times 50% fiber ratio at 12$ a kg.
you are at almost 11$ 


perhaps stacked foam? thin h100 on the top and bottom, and h45 or structural XPS for core?

I imagine you have thought all through this, but I am curious.
Me too!  
I laid up the corrugations. One of 200 gsm cloth, fibres running along and across the corrugations and one of 400 double bias, fibres running at +/-45 to the corrugations,  then realised there was a much better way, allowing the whole panel to be built in one shot, though not easily infused.   Infusion is probably not ideal for the corrugations as the thicker they are, the stiffer they will be.  

Great!

Glass costs near enough $AUS5 per kg, regardless of areal weight, plus $12 per kg of resin.  So each 100 gsm cloth and resin will cost 50c +$1.20 per sq m.   Plus 20% (for the corrugations and doubled for the two corrugations required,   a sq m of 100 gsm double corrugated glass will cost ~$4.10 and weigh 480 gsm.      

um,
0.5+1.2 =1.7$ is m^2
1.7*1.1=1.87$ is m^2 Corrugated
1.87*2=3.74$ is two m^2 Corrugated
mass
.1+.1=.2 is kg/m^2
.2*1.1=.22 is kg/m^2 Corrugated
.22*2=.44 is two kg/m^2  Corrugated

If i didn't embarrass myself, it's even cheaper and lighter than you thought?
Yeah, I included the corrugations twice. 

12mm H80 pvc foam is ~$AUS25 per sqm and requires an additional 200 gsm ($2.40) of resin each side so it weighs 1.4 kgs per sq m and costs $27.40.  
To match the foam weight, the corrugations are 300 gsm (1.4/0.48).  To match the cost, 650 gsm (27.4/4.1)

wow < 1/10 the price, and 1/3 the weight.
Plus the glue and the edges.  And we have not got any properties yet.  But worth a look.


 If the corrugations are stiff enough not to need faces, they will be lighter and cheaper, albeit ugly (not a problem for hidden bulkheads and things like floors where either one side or neither side is visible), harder to build and challenging to fillet and tab.  

If you can source a vacable cheap foam (even EPS), and do a square corrugated, that you can infuse, you could have a whole system.

I think H or VH would work.
assuming VH you add ~0.35 KG/m^2
These guys, and many others in Aus, blow the polystyrene.  Assuming VH is the same from all suppliers, it squashes under vacuum.  
Not that big a deal for the foam, but the cloth wrinkles.  The only foam to use is the extruded polystyrene. I will look into this, but from memory, Foamular Aus do not stock the higher densities.

Square corrugated add 20.7% to the length, as supposed to the curved 10.5%
How do you calculate this?  Assuming the corrugations are one piece, I get a sine wave uses 1.4 * the width,  semi circles is pi/2= 1.5ish and square corrugations are 2.

Your current corrugations are 1.5" which seem course, and leave a 3" thick core. Foam would allow a configurable option.
Agreed..

If damaged, would not fill with water. And repair would probably be easier? cut out a square and put a custom layed up fix in?
Yes, yes and yes.  There are a lot of problems with the corrugations, some of which would be overcome.  
Whether this was enough to justify it, time and testing will tell.  But for the prototype cargo ferry, where labour is free and low cost is more important than almost everything, it may be a good solution.

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Posted by: Rob Denney <harryproa@gmail.com>
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