Honeycomb vs corecell noise damping

[sigurd]

Anyone have an opinion of which transmits least water noise? Plascore/Nidacore polypropylene core is advertized as damping noise but I am considering aramid/nomex honeycomb.
Also looking for tips wrt wet layup vacuum bagging the aramid cores.

[DGreenwood]

Here is a tip on wet layup vacuum bagging aramid cores...don't even try it. I have done it with cured skins and aircraft ply bonded to it but even that is pretty shaky. Controlling the glue line between the fiber of your choice and the honey comb is critical. It is possible to assure a good interface there, with enough epoxy, but then you begin to get heavy and waste all the money you spent on the aramid.
Nomex honeycomb is best when teamed with prepreg, an engineer, a skilled composites tech, and a well controlled oven. And then, if you want to be really sure an autoclave is much better insurance for this type of construction.

[Petros]

For sound damping the more dense the material, the less sound transmission. A concrete hull for example with block most of the noise, while a fabric skin from a skin-on-frame will block almost none of it.

Building a hull heavy just to dampen noise is not advisable, but that is way sound is transmitted, through the air, and the less dence the material means more entrained air, that allows noise transmission. Other tips that might help a little to make the panels well braced so there is no "oil canning" of large panels. Make the whole hull stiff to lessen transmitted noise though out the hull.

Good luck.

[Ad Hoc]

Originally Posted by sigurd

Anyone have an opinion of which transmits least water noise? Plascore/Nidacore polypropylene core is advertized as damping noise but I am considering aramid/nomex honeycomb.
Also looking for tips wrt wet layup vacuum bagging the aramid cores.

Like everything related to noise, it is frequency dependent. You need to establish what are your dominant frequencies first, to see if the selected material can even address the range you're investigating. Otherwise you could waste a lot of time and money buying a product that is great in one application, but of no use in yours.

[Herman]

From experience: noise in the living area of the boat: Nomex will not damp anything, Nidacore a lot. However, I do not recommend Nida for long term boat hulls.

Core-Cell would be a viable option, or Airex R63

[sigurd]

Ok, so corecell is better than Nomex in that regard - thanks for letting me know.

[PAR]

It also depends on the noise, vibrational or airborne.

[Herman]

water noise he asked for.

Nomex boats make that nasty "bang" each time it hits a wave. More flexible boats are much less noisy in that respect.

[sigurd]

Originally Posted by Petros

Other tips that might help a little to make the panels well braced so there is no "oil canning" of large panels. Make the whole hull stiff to lessen transmitted noise though out the hull.

Originally Posted by Herman

Nomex boats make that nasty "bang" each time it hits a wave. More flexible boats are much less noisy in that respect.

Hm, do these statements contradict each other? Perhaps it has something to do with the difference between noise generation and noise transmission?

Anyway, great help.