Interesting read about the various issues of core
. As someone who has just spent the last 9 years being on the building crew and then building the interior
of my 40' Pescot catamaran
out of composite materials I think we are confusing a few of the issues. Firstly my boat
is not high tech--the shell was built by a damn good builder
but there was no vacuum bagging etc, just wet lay up. I learnt to laminate pretty quickly--its not hard, just very repetitive... and there are many great examples of boats built using these materials by amateurs like me.
I do think there is a difference with production boats, clearly they are built to a budget
, from the materials they use through to the type of fittings they put on--I'm appalled at the type of through hull
fittings some of the supposedly high end manufacturers use on their boats for example.
To start with there are a range of different cores, Western Red Cedar, balsa, foam and some form of honeycomb. Foam is great as long as it is something like airex (as someone mentioned as it is totally inert to water). However it 'dents' and so if you are beaching your boat
, WRC is a better core
to use on the very bottom of the boat where it sits on the sand--(that bit is for the multi people mad enough to beach their boats like I do). The other cores are all prone to rot
Then of course you have the resin type, epoxy
, polyester and vinylester. Epoxy
is amazing stuff, and for WRC and Balsa I think it is the only way to go to keep water
out and eliminate any risk of blisters
. Derek Kelsal has over 50 years of experience with foam and polyester and swears by it and has boats still going to prove it.
The ability to vary the thickness of the core with different lay ups provides a huge range of ways to build a strong long lasting boat--from memory, increase the thickness of the core and you increase the strength by a factor of 3. The strength is amazing (especially with selected use of carbon--2mm of carbon layup
has the same strength as 40mm wood
For furniture I used a cheaper foam and lay it up with 200gsm cloth and epoxy--it is wonderful stuff, cut it up like plywood
and make any shape you like--all up, my furniture added maybe 80kg of weight to the boat and it has lasted years of tough offshore
use (we are regularly going to windward offshore
in 30--40 knot
winds (with the boat doing 9-12 knots) so the boat gets a workout--it's much easier to break ply of the same thickness than my foam panels
Not sure I trust balsa without epoxy under the water, the idea of water getting in and rotting the balsa, and there are many examples is terrifying--My boat is WRC and epoxy in the hulls and decks and foam/epoxy on the bridgedeck areas and flat areas. Effectively it is a wood
boat so ANY hole (screw or bolt) has a six step method to seal it with three coats of epoxy and sealant
. As someone said there is a hell of lot of holes in a deck
and fresh water on wood is a real killer.
So in summary, cored built stuff is amazing, strong light and ridiculously tough if it is properly built.....--I just saw a 14 year old 60' cat (made of balsa duflex panels) slammed beam on into the point of a metal jetty (caught in cross winds) and there was nothing but a small graze... (the owner damn near had a heart attack)....and if there had been a hole, it's easy to fix with the right epoxy and glass.
I have seen the photos of a Pescot Firefly cat having been T boned by another cat doing 12-15 knots (racing in Thailand), the prodder speared through the hull
but the hull retained it's integrity where the bow impacted it and was able to sail back --it was a big repair job though. In contrast my brother had his beautiful 34' Logon sloop
(made out of NZ Kauri planking) T boned by a boat in a race
in NZ and it sank within 3 minutes--he and his partner only just got out in time.
As mentioned above, it is horses for courses, for me, cored hulls, especially for the type of boats I like to sail are the only way to go. It is also pretty easy to repair as long as you have epoxy and fibreglass there is not much you can't fix. But the there are distinct down sides (installing fittings into a foam or balsa deck
is a long process to do it properly) it is more expensive--especially if you are using epoxy and it has to be done well by people who know what they are doing when being built. This is probably the key thing, even production boats have issues, was just reading on another thread about a number of French production cats having issues with blisters