Opinions about Cored Hulls ...

[Pete the Cat]

I have worked around boatyards for 30 years and would say that we rarely ever saw a problem with cored hulls from the major builders that had not been fooled with by a second rate boatyard or dufus owner improperly installing a thru hull fitting. I can't actually recall any. However, decks are a different matter. Tons of problems with decks almost always the result of boat owner installed deck hardware that was not properly sealed. I bought a blistered boat with a cored hull-that even had spot or two of delamination, yet the core was solid and dry when we peeled it to the balsa core. The bugaboo about cored hulls is grossly over hyped IMHO. And if you believe the surveyors with their "moisture Meters" I have some real estate to sell you.

[boatpoker]

Originally Posted by Pete the Cat

I have worked around boatyards for 30 years and would say that we rarely ever saw a problem with cored hulls from the major builders that had not been fooled with by a second rate boatyard or dufus owner improperly installing a thru hull fitting. I can't actually recall any. However, decks are a different matter. Tons of problems with decks almost always the result of boat owner installed deck hardware that was not properly sealed. I bought a blistered boat with a cored hull-that even had spot or two of delamination, yet the core was solid and dry when we peeled it to the balsa core. The bugaboo about cored hulls is grossly over hyped IMHO. And if you believe the surveyors with their "moisture Meters" I have some real estate to sell you.

I respectfully disagree, I think ? I'm not sure what you mean by "major" builders but I have seen dozens of boats with wet or rotten core including, Niagaras, Nonsuch's, C&C's, J-boats, Farr, Regal, Sea Ray, Doral, Cruisers and I'm sure I could list more if I took the time to dig out my files.

I have a little article on my website titled Balsa Core = Compost. I must admit that I wrote it after doing a re-core job so it may be a little biased

PS : None the surveyors I know put total faith in moisture meters. That line seems to come from other people on this forum who believe they are easy to use and infallible..

[downunder]

Cored construction is not a problem if built using quality techniques generally using vacume bagging thesedawy. (SCRIMP, resin infusion) and a through holes above and underwater are decorred and epoxy plugged.

A well build cored hull topsides is not an issue. Designed correctly it means nessary insulation/strengths can be built into the design by varying core thickness.

All depends on quality of the construction. eg. Jedi's 20yr hull - no issue.

[boatpoker]

infusion is not a guarantee either, witness the two 63' Bertrams that came apart on their delivery trips from the factory one of which is shown below.

[downunder]

Originally Posted by boatpoker

infusion is not a guarantee either, witness the two 63' Bertrams that came apart on their delivery trips from the factory one of which is shown below.

Agreed needs to be a quality job by someone who knows what they are doing.

[Curmudgeon]

Originally Posted by rognvald

Is that something like: And my daddy's better than your daddy? I seem to remember that line floating around the playground many, many, many years ago.

No, if there's no core, then water can't get into it.

[downunder]

Can't get into core but water can get into the fibreglass especially if polyester resin used as someone suggested earlier.

[DerekKelsall]

Beware balsa core. It rots quickly and there is no sure way to keep moisture out. Balsa Decks are notoriously prone to rot. It will get you eventually - the problem being it is a time bomb. It could be 3 y.o or 30 y.o. before it shows. This includes all parts of the boat and below the WL is not more prone than above. I first saw this 45 years ago, when I made a rule to never include anything within a boat spec which could rot. There is simply no need/no advantage. The PVC foam core i have been sailing, designing and building for all the years since has been 100% reliable, with 1960's foam,glass,poly boats passing structural survey today, with lots of life left in them. If well built and well buried balsa will last a good while but who knows how many owners will have drilled thro the skin for a fixing.

Happy boating,

Derek Kelsall. FRINA.

[Tortuga's Lie]

Originally Posted by DerekKelsall

Beware balsa core. It rots quickly and there is no sure way to keep moisture out. Balsa Decks are notoriously prone to rot. It will get you eventually - the problem being it is a time bomb. It could be 3 y.o or 30 y.o. before it shows. This includes all parts of the boat and below the WL is not more prone than above. I first saw this 45 years ago, when I made a rule to never include anything within a boat spec which could rot. There is simply no need/no advantage. The PVC foam core i have been sailing, designing and building for all the years since has been 100% reliable, with 1960's foam,glass,poly boats passing structural survey today, with lots of life left in them. If well built and well buried balsa will last a good while but who knows how many owners will have drilled thro the skin for a fixing.
Happy boating,
Derek Kelsall. FRINA.

While I agree that balsa coring has a potential for water issues, especially on decks, I think that there are many more cored hulls that have no issues than those that do. I would not hesitate buying one as long as it passes both a moisture test and a sounding test. I really think that you cannot issue a blanket statement one way or another and have to evaluate each boat individually. Coring does have the advantage of a hull that is stronger and stiffer (per weight), lighter overall (ie..faster boat) and gives added insulation (little condensation).
As I said earlier, I have a 35 year old cored hull that shows absolutely no indication of water ingress and likely will be sound for the foreseeable future.

Cheers,
Tom

[Dockhead]

Originally Posted by noelex 77

If you want number of hulls produced look at manufacturers like Beneteau.
If you want top quality, which only happens with smaller numbers look for manufacturers like Amel ( if you don't want an Oyster or a Rustler )

Touche -- forgot about Amel! :sheepishgrin:

[Dockhead]

Originally Posted by s/v Jedi

My boat was built using the SCRIMP technique in 1993, launched in 1994. It is now 2013 so that is 19 years which isn't "lately" nor "the past 10 years".

When people drill holes into the core and it gets wet then they get what they deserve. There is no cure for stupidity. It also isn't that much more work to do it right when a fast curing filler, like the 3M vinylester, is used.

Much depends on the design too; the core should be tapered out to a solid laminate for areas where high loads occur (around keel, prop-strut, rudder etc.) or where many fasteners exist (deck-hull joint for example). I would not be charmed by a hand lay-up cored hull either.

My boat is not as old, but generally ditto on all of this.

I would not drill a hole in the cored part of my hull, period. I know it's possible to do right, but I just wouldn't do it. The builder reserved solid fiberglass areas for through-hulls anyway, so why would you need to? No holes = no place for water to get in. I've got enough more than enough holes already, thank you

The other great leap forward in this technology was resin encapsulation of balsa blocks. When this has been done, if water does somehow get between the hull layers, you still won't get a soaked or rotten core.

Balsa has a big advantage over synthetic coring material in that it has quite a lot of strength in compression, so a GRP-balsa-GRP sandwich can really be immensely strong, which is a definitely good thing. My boat is skinned in Kevlar ahead of the keel, taking that still a little further. Downside of balsa, of course, is that if it is not encapsulated and gets wet, it will rot


A cored deck is much riskier than a cored hull because there are many more potential points of water ingress. But we can't do without cored decks -- there just isn't any other practical way to do a strong deck on a GRP boat. Once you have the cored deck, you might as well go the whole hog Because you are already hostage to quality and skill of the builder anyway.

[Dockhead]

Originally Posted by nhschneider

Our 29-year old Contest is completely end-grain balsa cored, right down to where the keel bolts on. When I was adding a second depth transducer recently, we found the core (at least in that area) to be dry but I have no reason to suspect that there is water entering the core anywhere else. By the way, our boat received a Lloyd's certification when it was built.

Fair winds and calm seas.

For those who don't know Contest yachts (they are not very common in the U.S.), this is one of the world's finest sailboats (and unfortunately on of the most expensive), built in the Netherlands Absolutely gorgeous boats. Known to last forever despite their fully cored hulls

[DerekKelsall]

Tom,

I believe we agree. Beware.

The point I would like to make is that this industry as a whole has a lot to learn about the different cores. If everyone had the all round experience of being involved in all aspects over a few decades, no one would push balsa. When I started foam building, I saw it as the end of the rot in boats situation. The industry seems intent on keeping "rot" on the scene.
I saw one very serious case where the moisture meter and the tapping did not reveal the extent of the problem. A soft spot at one chain plate lead to the whole side of a nice looking 55 ft cat, 5 yo. have the whole outside skin removed chasing rot. Ie with the thin skins of multihulls they should never use balsa core.

Balsa was first being put into decks - the last place it should be used - but designers still spec balsa for decks.

I am primarily concerned with new build. There are many ways of achieving the same effect without using a material which needs very special care and still cannot be guaranteed.

Happy boating,

Derek

[s/v Jedi]

Defrek, are you saying that foam cores do not rot? I have seen rotting foam cores...

And how about the melting foam core in rudders?

[albergsailor]

The practical boat buyers guide was what i was missing! that book is great as it talks of the construction of hundreds of different cruisers. Im glued to that book! It tells me which ones are solid glass and which are cored ect. I now see that there are many many boats that have solid glass hulls. the boat i was looking at b4 was a whitby 42. it really is a tank why they cored the sides down to just below the waterline i may never know? I do know i wont buy a cored boat. thanks everyone!