Mat placement.

if using 1708 or 1808 in a non-gelcoat foam build with epoxy; is there ever a situation where mat would be placed onto the core versus out?

Would mat potentially improve or weaken the structure?

Say
1708-core-1708 (mat out)
Vs
1700-core-1700
Vs
1708-core-1708 (mat in)

I am only familiar with mat out for print through w/ gelcoat, but someone told me mat to core is also used. I didn't want to argue.

Thanks for any

 

The distribution of the stresses on a panel, in its thickness, ranges from a null value on the neutral axis to maximum values, tension or compression, on the outside. From this point of view (although there may be other considerations, as you point out) weaker materials should be placed close to the neutral axis.

 

Okay, so I will run some tests mat in.

Thanks!

 

I'm covering a solid foam blank on a skinny race boat
by piling 1708 on 1708 on 1708, etc with differing lay-angles for more multidirectional strength
and at varying thicknesses depending on point loading.

I'm interested in your tests.
TANSL is correct in theory of course but I bet you won't measure the difference.

Standing-by

 

The only thing I don't like about mat is the snakiness of biax can be an advantage at times, other than the obvious weight issue.

For the mat; I expect the mat to be 3oz heavier per sqft. when two sides, or for say a 400sqft area; 75 pounds more.

It would need to be stronger to justify that amount.

It'll be a few weeks before we get any numbers, but I will report them here.

 

The thickness is not as important, although it is, as to check that none of the layers supports a tension / compression higher than the admissible. It is interesting to note that a laminate of a certain thickness can be more resistant, more suitable, than another of greater thickness.

That is almost correct but over time, and depending on the circumstances of use, the difference could be dramatic. And, in this case, it is not more expensive to do things well.

 

Just wondering if there’s any updates on the testing.

Also, am I correct in understanding that the mat is only bulking material, and so a layup of biaxial with 1708 only at the surface would be stronger than an equal number of layers of all 1708?

 

Yes on the question. Never bothered to test; always keeping stitching out unless I make a mistake in tabbing, then don't care much..