Divinycell foam construction from mid 1980s?

[andypag]

Can anyone give me the pros and cons of divinycell foam core? Especially in an older boat from the mid 1980s. I'm looking at potentially buying a boat that's built this way. What should I look for when inspecting it?

[GordMay]

Look at any penetrations of the cored areas. They must be perfectly sealed against water intrusion.

[Copacabana]

Is the hull cored? Below the waterline? Or is it just the decks?

As Gord mentioned, check around fittings. Perhaps a little tapping to check for delamination (which is unlikely).

My decks are cored with divinycell (now 20 years old) and I haven't had any problem with them at all. In fact, the boat is cooler inside as the foam provides good insulation, in addition to being lighter than most materials used for decks. I'd view divinycell as a plus if I were shopping for a boat.

[coopec43]

Like Copacabana I view divinycell as a plus.

My hull is Airex foam which is good as it can deform under extreme load and will return to its'original shape as it has a "memory" BUT normal airex should not be used on deck as at softens with heat. I have used Divinycell on deck and as Copacabana says makes the yacht cooler.

The builder was obviously looking for a quality yacht as it would be more expensive than solid glass. I'd be more interested in the builder and how the yacht was constructed than the qualities of divinycell. (Using a female mold with divinycell would take special expertise)

Divinycell Foam - ATL Composites
atlcomposites.com.au/category/9/Divinycell-Foam
For more than 30 years Divinycell has been the first choice of leading producers of sandwich composite structures around the world. During this time, the ..

divinycell - Fiberglass Supply
http://www.fiberglasssupply.com/pdf/...moformDiab.pdf
THERMOFORMING. Scope. Thermoforming is done by heating Divinycell to it's softening point and forcing it against the contour of a female or male mold.


Clive

[TomNH]

My 1989 Swan 43 has Divinicel cored decks (and longitudinal hull stringers). I’ve seen no problems with them at all, and I have been assured that water penetration at hull penetrations shouldn’t be an issue either, as the core will not allow the water to spread - unlike balsa. The insulative properties help manage condensation internally too.

A club boat I used to manage, a 2001 X-412, was divinicel cored both hull and deck. It had a tough life, both racing offshore (fastnets etc) and being bounced off marina docks, and navigation marks, by skippers whose enthusiasm exceeded their competence at times. The foam core was never a problem, and did allow the hull to deform and flex back from some impacts (typically we saw the evidence of impacts at frame/bulkhead areas where it couldn’t flex, such as the transom). The hull was repaired in places without much trouble over the years. When it was purchased from the club by a member the survey identified an area of delamination forward of the keel that was attributed to slamming rather than construction, and again fixed easily. There were no other construction issues, despite a tough life.

[Mike Banks]

Divinycell is available in different grades--I think from memory the orange coloured stuff is the best. It is closed-cell polyvinyl chloride, was and still is one of the best of all foam cores.

Test for water ingress using an ultrasonic probe--most marine surveyors use them.

Scrape off a little of the cladding and hold a flame to it. If it flares readily it is probably polyester. If it burns less readily and smells awful--that indicates epoxy resin.

If it is polyester, check even more carefully for osmosis and water ingress, delamination etc,

If it is made from epoxy--with adequate layers of glass, the chances are you have an excellent hull. Epoxy sticks well to PVC foam.

Some later hulls were made using vinylester resins. They are great too.

[Fore and Aft]

Delamination would be my worry. Check to see if any of the hull and deck surface flex's when you give it a tap with a hammer or the back of a plastic handle screwdriver.
I surveyed a cat built in 2005 and the cabin top had the cabin edges painted black so it looked like the windows wrapped around the cabin. Everywhere that was painted black had delaminated and the surface could be easily flexed with just your thumb.
Cheers

[chowdan]

I live aboard my 42ft sailboat built in 1980 out of taiwan. My boat is damn near identical to a swan 42.

The cabin top are divyncell from what I can tell and my cabin sides also are divyncell. I am unsure if the hull or side decks are cored as well, but it wouldnt surprise me.

I would say it is a benefit after living aboard for nearly a year. Foam adds immense sound dampening, and excellent insulation.

I am upgrading port lights as they are leaking and non opening. The manufacturer literally cut the holes and did not seal it. No rot or delam and they have likely leaked for 5+ years at minimum. Other areas indicate leaks over longer term with no rot or delam in 5he structure.

Sure I would prefer it to have been properly sealed, but I am happy to see the core has held well!

I have teak decks mechanically fastened. At some point I will remove them, but as far as I can tell I have zero 8ssues but that wont be confirmed until they are pulled.