Rob:
There is no question that the shear strength is not on the level of higher density foams. Your proposed test seems not particularly useful without some sort of quantitative comparison with a control.
The wrapped foam plank system not only should provide longitudinal stiffening in lieu of stringers, but should also reduce the issue of shear strength. I've come to the conclusion tentatively that wrapping planks with fabric on the bias or 45 degree biaxial glass is probably viable. Obviously it will not pull tightly around the corners, and that should not be a problem if there is a way to slit the corners such as a rotary cutter. Optimally we want a good bond between the wrap and the next ply. This would create a very functional structural shear web, just like a truss beam such as I have built from steel to hold roofs up, but on a much smaller scale. A bit of "frizz" projecting up at the intersections should be an asset so long as they do not make an actual lump. How to slit the corners may be the issue here. The other obvious solution is to stack plank as I suggested before and lightly glue biax to the edges of the whole stack at once, then cut them apart. This could also involve thin spacers to give the "frizz" which would then bond to the surface plies. The spacers could be nothing more than think sheets of linerboard (shoebox material). The challenge of course being to make a consistent cut exactly where it is needed. Tilting each plank up away from the stack close to 90 deg, would create a V that should make this easy...... Obviously only one side at a time would be glassed. Once the system was worked out, it should go pretty fast........
H.W.
On 07/08/2018 09:44 PM, Rob Denney harryproa@gmail.com [harryproa] wrote:
There is no question that the shear strength is not on the level of higher density foams. Your proposed test seems not particularly useful without some sort of quantitative comparison with a control.
The wrapped foam plank system not only should provide longitudinal stiffening in lieu of stringers, but should also reduce the issue of shear strength. I've come to the conclusion tentatively that wrapping planks with fabric on the bias or 45 degree biaxial glass is probably viable. Obviously it will not pull tightly around the corners, and that should not be a problem if there is a way to slit the corners such as a rotary cutter. Optimally we want a good bond between the wrap and the next ply. This would create a very functional structural shear web, just like a truss beam such as I have built from steel to hold roofs up, but on a much smaller scale. A bit of "frizz" projecting up at the intersections should be an asset so long as they do not make an actual lump. How to slit the corners may be the issue here. The other obvious solution is to stack plank as I suggested before and lightly glue biax to the edges of the whole stack at once, then cut them apart. This could also involve thin spacers to give the "frizz" which would then bond to the surface plies. The spacers could be nothing more than think sheets of linerboard (shoebox material). The challenge of course being to make a consistent cut exactly where it is needed. Tilting each plank up away from the stack close to 90 deg, would create a V that should make this easy...... Obviously only one side at a time would be glassed. Once the system was worked out, it should go pretty fast........
H.W.
On 07/08/2018 09:44 PM, Rob Denney harryproa@gmail.com [harryproa] wrote:
That is precisely what I am asking. And also suggesting some ways the lack of compression and shear properties can be enhanced to make the cheaper cores usable. Getting the engineering numbers is the first part. The second part is testing, both bench and full size. Then we can include it in the plans.
We have not done this previously as there was too much going on getting Intelligent Infusion and the resulting boats happening.. Now that this is coming under control, we can focus on further improvements, of which optimising the core is one.
Re your cooked polystyrene:Interesting results. I would be interested to know if there is any difference in shear properties. ie Glue a piece of squashed/heated to a piece of normal then glue a piece of ply (great for stuff like this) on each side with an inch or so sticking out at opposite ends. Put it in the vice and apply pressure to the bits sticking out so the material is loaded in sheer. See what happens.
On Sun, Jul 8, 2018 at 11:02 AM, eruttan@yahoo.com [harryproa] <harryproa@yahoogroups.com.au> wrote:
Rob, would a resonable question be for said engineer, "Is 400kpa XPS a resonable core for a harry?", or the corresponding 700kpa material? Or where they can be used safely?
Which is more like asking (where ) will h60 do? Or h45?
Perhaps more interestingly, can some parts of some of the harrys be made out of these as a cost optomization question? And what can't?
I mean, your asking the questions and paying the bills, so you do you. Untill I pony up the cost of a call to Scaled Composites, I got no reson to expect an answer.
__._,_.___
Posted by: StoneTool <owly@ttc-cmc.net>
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a new topic | • | Messages in this topic (24) |
SPONSORED LINKS
.