Subject: Re: [harryproa] RE: Unstayed masts
From: Rob Denney
Date: 3/3/2014, 5:10 AM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

G'day,

I did not mean to be negative.  If the costs and weights are acceptable, go for it.  I forgot you were thinking wings.    Another option may be to build a square section box, with the biggest sides that will fit in the wing section, and add the front and back sections.  Build it up to round at the deck bearing.  This gives max I with min material.   This would work better than a mould for the pultrusions.

If you go with the split mould, you could maybe save some weight by adding ribs.  Could also add core to the trailing edge if the section is big enough.  

I doubt there will be much cost saving replacing the carbon with 3-4 times as much glass by the time you have included the resin.  

The join is easy, in theory, but is often stuffed up.  I would still apply the outer layer, or at least add some glass across the join.  

Infusing thick layers of carbon is hard, but not impossible.  Do some small pieces and see what works.  If you build a spar in a mould, maybe make it from  perspex or glass so you can see what is happening.  

I have sent you some drawings to peruse.

rob




On Mon, Mar 3, 2014 at 6:43 PM, <gravitygroper@yahoo.com> wrote:
 

Well my reasoning was primarily relating to wing masts as opposed to round masts... I think this would be a worthwhile improvement from the tapered round masts.

i think building a 2 peice split mold would be quite easy all things considered - a plug from CNC hot wire cut foam, glassed over and faired for the plug. Take the 2 peice split mold off it - in glass. Do a good one, and it could be shipped all over the place for other builders to use.

I dont see why the join has to be difficult. A recess can be setup for matching halves and they just bond together flush... they do this on giant wind turbine blades, so im sure the bonding is upto the task...

The pultruded rods i was referring to an earlier, can be round or rectangular bars. If rectangular, its a simple matter of stacking them together for a large cross sectional area of solid high density carbon. The high modulus variety has a compressive stress of almost 3000Mpa - almost 3 times the standard UD carbon laminate! They can also be interleaved with glass or cabon fabrics to get the off axis fibers in 1 continuous wet layup. Simply layer the pultrusions with dbias extending around the edge and down the sides for the shear webs. Doesnt have to be a C-section either, can be whatever you like... although the C-section is easy to make and bond into the the wing rear half. The front and aft parts of the wing section can also incorporate extra carbon so there is reinforcement fore/aft from the molded skins, and side/side in the separate internal spar.

So the larger diameter base in solid glass, transitions up the sides of the internal spar and tapers off over several meters... Its going to be heavier, but the weight is down low so it wont affect pitching of the vessel bugger all. The idea is simply more glass to reduce the carbon consumption. The second part of the idea is to make the entire skins of the masts, including the heavy laminates at the base, all in 1 shot via infusion in the molds rather than wet layup or the difficulties infusing heavy UD carbon laminates.


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