Honeycomb fatigue

[Alik]

Originally Posted by HakimKlunker

The boat in question HERE is 13.70 m with Lcwl 10.6 m and Bmax 2.9 m. In 1972 there were two Cummings 350 HP in it with a weight of 7.6 t. The idea for 2010 is to have it lighter and faster. Previous company hobby-designers are excluded from the project!

We can check structure for You if You need, but I am 99% sure HexaCor will not comply on bottom. Actually I have structural files for few boats of similar size/weight/speed, nowhere we can use HexaCor...

[HakimKlunker]

Thanks Alik-bert. I'll come back to you with that on a later stage. I thought of h/c for cockpit floor, engine hatch etc. Keel area solid of course. The main lengthwise structure (at present) are two parallel liners with frames of ca. 2m distance and the major three b/heads. Bottom and topsides with foam sandwich.
And I am sure that we get over 12 kts this time

[Alik]

We are building (with AusThai) new boat for our company now, it is a 8.1m planning powercat. We use H130 foam for bottom and rest is HexaCor, but on cat area of bottom is small...

[mongo75]

Honeycomb is fine for flat panels, and some smaller curved panels not subject to much abuse, but I personally not use it to core a hull- not enough surface contact with the fiberglass to offer sufficient strength. Like others said, use foam, or keep it solid glass (below the waterline). And again the biggest problem you'll have in hot climates is the air trapped in the honeycomb constantly expanding and contracting due to the extreme heat, which in time will cause delamination. THis can be mitigated by filling the honeycomb with a lightweight filler such as microballoons and epoxy, but that kills the reason for coring in the first place- to lessen weight.

[HakimKlunker]

Thanks all, for your contribution. Background: We have a design clown in our company, who believes that h/comb is the ultimate building material. Alik, you know ... He also has strange ideas about hydrodynamics and this leads to 50ft boats with 740 HP not exceeding 14 knots in speed.
I have the feeling that my future will lead me mostly away from h/comb...

[Alik]

Do You mean this one?

[HakimKlunker]

Only ONE thing went wrong and it was a spelling mistake:

We made a FAIRY boat instead of a FERRY