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.
With the thickness we are talking, cheap 1/2" foam gives a 1" core, Which has to have hella shear, no?
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^2These 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.
BAH! I assumed VH with it's 165kpa could hold 100kpa vac ok. I thought it might be perfect as it still might warp to a gentle hull curve under vac. If cheap enough vs XPS, hit it with a thin coat of resin/sealer?
Foamular Aus has under concrete slab foam, so they must have something thats 170+KPA
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.
Here are my thoughts. I assume errors. Pointing them out earns a cookie.
The arc length of a sine wave
2pi =~6.28, arc length to 2pi is 7.640395578
~7.64/~6.28 = ~21.7% longer
but that is for a proper sin arc, the corrugated sheets are, typically 3" pitch and 1.5" depth, so the sin wave has been stretched, lengthwise, 50%, so only ~10.7% longer, which agrees with your assumptions, my assumptions, and the given rule of thumb for corrugated iron, right?
As an aside;
Standing in the building supply I hear two guys discuss why everybody says 10% and not 10.7%. One of them suggests it's because contractors and roofers do not care about math. The old guy behind the counter speaks up and suggests it is because builders are considering significant figures, and since one buys a 4x8 sheet, 10% has only one significant digit. I don't know how that effects one in a SI state, with mm measures.
I will be here, inside, all week.
Semi Circles is pi/2, as you said.
Calculating square corrugations.
I guessed a flat and a slat ratio of one to one. so, ( \_ ). This is, of course configurable.
But the slant portion of the square corrugated would be the hypotenuse of a square, which is sqrt(2) = ~1.4, which is also how long it is vs mold length. so just slants, and only glue at just points ( \/\/ ), would be 40% longer. any flats would make it proportionally less.
If you have a way of determining how big the core interface, and the face interface, should be vs slants, I would love to hear your thoughts.
Perhaps at this point it would be neat to take it to a composite engineer and see what shapes would give optimal outcomes? Could someone on boatdesign help?
My questions:
I had heard you suggest infusion will generally travel 8" along glass? If you had to guess, would you think you could infuse a stack of outside skin, outer corrugated foam and glass, inner corrugated foam and glass and upper skin?
Would the slants give a natural infusion path? Or would you still need to groove the foam?
Is there some ratio of slant to flat that would eliminate the need for a second core?
Is a single core more infusable?
What properties would you look for/test for? Layup a length of h100 and the corrugated core and look at yield? yield to failure? Hit it with a hammer?
When can I build my E25 with this?
Even more excited.
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