That's a problem that's been kind of nagging at me.... I'm aware of the issue. The fact that these would be used in an infusion means that the pressure of the vacuum might mitigate the problem. Without doing a test piece, it's hard to tell what would happen, I suspect that if you used spray glue on the edges only, and simply pulled the flat as tight as you could get it on the uncut side, and likewise on the cut side, the pressure of the vacuum would lay it out nicely. The other alternative would be to lay narrow tapes down the interface, but then one wouldn't get the bias effect. Probably the best approach I've come up with would be to clamp a big stack of strips together, and put a think layer of epoxy resin on the ends of the strips just enough to stick the fabric and apply fabric on a bias, then once the epoxy has set, use a very sharp blade to separate the strips.... One might go through a few blades ;-) If there's one thing I've learned, it's that just because someone hasn't done something doesn't mean that it won't work. If one does only one side at a time, then the foam can be unclamped and each plank tilted away along the glass line, creating a nice angle to follow with a blade.
I was unable to make the time over the fourth to build my test rig for compressing XPS, but I've rounded up the iron I'm going to use, and hope to knock it together tomorrow. Previously I tested by heating the foam and clamping it between a couple of pieces of wood, or heating the whole works and squeezing it. This will allow me to compress to various thicknesses, and to heat one or both surfaces. A flat iron rim will contain the foam from expanding outward when pressing. I got some very impressive samples using crude methods.... and some not so impressive ;-( ............. That's the nature of experimentation. Process control and repeatability is where it's at. It would not be inaccurate to say that I've learned as much or more from my failures than my successes in many ways. For me, they are the foundation of a continuing process, not a cause for giving up or getting discouraged.
H.W.
On 07/06/2018 05:56 PM, Chris Purkiss chrispurkiss@bigpond.com [harryproa] wrote:
If you are wrapping the foam strips 360 degrees in glass then a problem might be getting the glass to go around the corners and leave you with square surfaces to but together.Might be hard to keep to fair.
Try a couple of curved strips to test your method.
Chris PurkissM. 0428755749
On 7 Jul 2018, at 2:05 am, Björn bjornmail@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:
I think it's a good idea. I've been thinking about it as well. But it's a lot of manual work, and maybe this stiffness isn't needed. Well, at least not with a normal skin thickness or core material. I guess that with this method you could have a super thin skin, and maybe also the lowest grade XPS core. The "webbing" will have twice the skin thickness or more, depending on how the glass is wrapped around the "planks", so will be strong enough for the shear load even without a core, probably.
A similar method would be to make cuts in the foam at regular intervals, and push glass through these cuts. Lets say cuts of 5-10cm/2-4" at 5-10cm intervals, or so.But I'm not sure if the shear load in the core is so high that these cuts needs to be reinforced with glass. Maybe the epoxy is enough? And if you make more cuts in different directions across the foam, lets say a 60° angle, then we are back to "my" idea of a honeycomb pattern in the foam. =)
On Fri, Jul 6, 2018 at 5:10 PM, StoneTool owly@ttc-cmc.net [harryproa] <harryproa@yahoogroups.com.au> wrote:
In looking at construction possibilities, I keep coming to a rather
unique method..... or at least it looks unique to me. That is to slice
the foam into planks say 15 - 20 cm wide. Wrap the individual planks
with fabric on the bias or with triax, sticking it to the planks using
spray adhesive. Then do the infusion layup, laying fabric down, then
the planks, all pushed tightly together, then the interior fabric.
Then infuse.
This of course is more work, but has multiple advantages,
especially where foams like XPS are being used. The interface between
the planks will be a solid glass rib of two plies, and this will make a
stiffener / stringer. The ribs will also facilitate infusion, creating
a flow path between the surfaces. But most important, they produce a
solid glass longitudinal shear web at each joint, reducing concerns
about core separation from the surface plies. The challenge for me at
least is the fact that the edge where the hull side meets the bottom is
going to be curved, as is the top edge.... but it's all doable, just
challenging.
H.W.
Posted by: StoneTool <owly@ttc-cmc.net>
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