Soundness of balsa cored hulls

[coopec43]

Originally Posted by boatpoker

Deblen, I think we are pretty much on the same page except that I have seen quite a few foam cored rudders where the foam has disintegrated. I have also seen a number of saturated and disintegrating foam cores in Boston Whalers that weighed in 3-4 times their advertised weight.

I am sure you would agree there are many types/brands of foam cores.

When you say
"I have also seen a number of saturated and disintegrating foam cores in Boston Whalers"

Have any been Airex, Klegecell, Divynicell? I can't imagine a Airex "disintergrating"

[TeddyDiver]

Originally Posted by Fore and Aft

Dockhead you have an optimists view of Balsa/foam core resin infusion. Just this year two Fountaine Pajot cats I sueveyed had core issues. Fountaine Pajot even proudly claim on their website resin will fill any gaps. I have no idea about the science of water entering between a core and fiberglass skin but when it does the results can be very interesting.

Cheers

I don't think FP can be regarded even remotely as high quality..

[Joli]

With cored boats a key factor is build quality and maintenance. Either can lead to future problems.

Our cored boat has about 250k miles on it through all the major oceans. I know of one small area below the waterline that had delam but has since been sealed. We opted not to recore it when last hauled Maine. It's not propagating so it's fine for now.

We're currently in Trinidad and will next sail to Spain. I wouldn't worry about sailing a good cored boat anywhere.

[mikereed100]

Originally Posted by coopec43

I am sure you would agree there are many types/brands of foam cores.

When you say
"I have also seen a number of saturated and disintegrating foam cores in Boston Whalers"

Have any been Airex, Klegecell, Divynicell? I can't imagine a Airex "disintergrating"

Agree. The cross linked PVC foam made by manufacturers such as the above is a very different beast from the expanded polyurethane foam used in Boston Whalers. If memory serves, Derek Kelsall did some immersion testing of Airex panels back in the day and found that they held up very well. Expanded polyurethane is "closed cell" but cells tend to break down with extended immersion. The foams I have used were marketed as good for no more than one year if wet.

[Dockhead]

Originally Posted by Fore and Aft

Dockhead you have an optimists view of Balsa/foam core resin infusion. Just this year two Fountaine Pajot cats I sueveyed had core issues. Fountaine Pajot even proudly claim on their website resin will fill any gaps. I have no idea about the science of water entering between a core and fiberglass skin but when it does the results can be very interesting.

Cheers

Cheap mass produced boats like FP can of course have problems. Proper execution of cored hulls is expensive and requires technology, vacuum bags, etc.

Have you ever heard of a Swan, HR, Contest, or Discovery with core problems? Even one?

You wrote "Balsa works great when done right; I just don't see that very often" -- naturally you don't! People come to you when they have problems; they don't show you sound hulls. The surveyor's perspective is extremely valuable because you know everything which can go wrong. But that doesn't necessarily mean you know what goes right, because you may not see it.

[s/v Jedi]

Jedi is balsa cored throughout. But the cored is tapered out ending in solid fiberglass wherever a fastener goes through. This includes all of the hull to deck joint, at all the chain plates, thru-hull fittings etc.

We are the second owner and at some point discovered a damaged spot on the deck where something very heavy the size of a bowling ball was dropped. It had fractured the top skin and the repair was done with fairing compound and paint, which started to come off. There was an obvious soft spot which means wet core.
But balsa core is divided into small squares which are fully encapsulated by resin when done right (vacuum bagging, resin infusion) and thus this damage was limited to 3 such squares and easily fixed.

I don’t think I have heard of core damage below the waterline ever. If one just pops a hole in it for a fitting then you are an id|ot and deserve the damage.

[boatpoker]

Quote:
Originally Posted by s/v Jedi View Post
"But balsa core is divided in to small squares which are fully encapsulated by resin when done right (vacuum bagging, resin infusion) and thus this damage was limited to 3 such squares and easily fixed. -I don’t think I have heard of core damage below the waterline ever. If one just pops a hole in it for a fitting then you are an idiot and deserve the damage."


Like this one on a high end motoryacht whose throughull fell out when I gave it a hand pressure jiggle. Thankfully bungs and an emergency pump saved the day. I can post photos of this stuff from supposedly high end boats all day long."

I agree balsa works great when done properly, I just don't see that very often.

One of the issues with infusion is that there is no way to confirm that the kerfs were ever filled without cutting it open (as evidenced by the Bertram photos I posted earlier). I have literally seen hundreds of such boats cut open and have rarely seen 100% fill of the kerfs between those blocks of balsa.

Seems we have several fortunate people here who have a different experience than I. Admittedly I have become a bit cynical after 30 years of inspecting crap from many builders. I trust none of them until I see it/check it for myself.

[JPA Cate]

Originally Posted by boatpoker

Quote:
Originally Posted by s/v Jedi View Post
"But balsa core is divided in to small squares which are fully encapsulated by resin when done right (vacuum bagging, resin infusion) and thus this damage was limited to 3 such squares and easily fixed. -I don’t think I have heard of core damage below the waterline ever. If one just pops a hole in it for a fitting then you are an idiot and deserve the damage."


Like this one on a high end motoryacht whose throughull fell out when I gave it a hand pressure jiggle. Thankfully bungs and an emergency pump saved the day. I can post photos of this stuff from supposedly high end boats all day long."

I agree balsa works great when done properly, I just don't see that very often.

One of the issues with infusion is that there is no way to confirm that the kerfs were ever filled without cutting it open (as evidenced by the Bertram photos I posted earlier). I have literally seen hundreds of such boats cut open and have rarely seen 100% fill of the kerfs between those blocks of balsa.

Seems we have several fortunate people here who have a different experience than I. Admittedly I have become a bit cynical after 30 years of inspecting crap from many builders. I trust none of them until I see it/check it for myself.

^^^^^And, i'd like to thank you for your suspicious attitude: it seems perfect for a professional boat surveyor.

It is why, although we had many sea miles with our Airex cored hull--like Jedi's it also had solid f/g along the hull to deck join, but on ours, the balsa cored deck was not done in the infused squares way, and our mush could have spread. Particularly, the areas by the chain plates were not done right.

So, while someone may have a no problems vessel, it is difficult to be certain it will stay that way. The ultimate decision you make would depend on how good you are at fixing picky problems; on your risk tolerance, and prudence.

A personal decision, but boatpoker's experiences read to me like a great big warning sign. Ymmv.

Ann

[Fore and Aft]

Boatpoker this is always my personal favourite. People who cut holes in the deck or cockpit sides and then don't seal the core afterwards. This vent and couple of others caused the balsa core to rot out around the whole cockpit coaming. The water had been trapped for so long there is blisters on the sides.
Cheers

[s/v Jedi]

I didn’t have motorboats in mind when writing that because yes, I heard many such stories about wet core and no sealing, let alone tapering to solid glass on them.

But many sailboats are done right.

All the balsa core I have seen is constructed as squares of end grain balsa glued onto a fiber scrim material. This allows it to conform to shapes and resin adheres very well to/into that end grain as well as around the squares to seal them.

TPI in Newport, RI used the SCRIMP method of vacuum bagging and resin infusion and this process is well established and known to provide these good results. AFAIK all the boats built by them since the early 90’s are done this way, incl. J boats, Lagoon and of course the Sundeer production series.

[GordMay]

Originally Posted by Wandering1

... The boat was built to Lloyd's 100A1 standard. ...

Says who?
Was the boat actually “classified”, or “certified”; or did the builder simply claim to have built it to 'standard'?
BTW: I am NOT questioning the design, nor build quality of you boat - just trying to determine exactly what you meant.


A Lloyd's Register classification [“Maltese 100A1", or +100A1"] continues throughout the life of the yacht [unless it fails a survey], while certification attests to the condition, only at the time of delivery.
To keep a yacht "in classification," it must be inspected on a regular basis, usually annually, or whenever changes, or damage to the yacht, might affect the classification.
The Lloyd's "Building Certificate", and "Hull Construction Certificate", do not involve ongoing classification surveys.


In the USA, Tillotson-Pearson, for example, is ABS certified, although the yachts they produce are still carefully monitored during construction, before the ABS +A1 classifications are awarded.
Christiensen Yachts is the only U.S. builder [of megayachts] to ABS classify every yacht [except one that went with Japanese NKK society classification to that country], and, they actually keep a furnished office for the ABS surveyor, who is almost constantly on hand.
Dave Christiensen estimates that the added cost is about 3 percent of the total, and probably adds 300 to 400 manhours of engineering time, to prepare extra drawings and plans.

[Dockhead]

Originally Posted by boatpoker

Quote:
Originally Posted by s/v Jedi View Post
"But balsa core is divided in to small squares which are fully encapsulated by resin when done right (vacuum bagging, resin infusion) and thus this damage was limited to 3 such squares and easily fixed. -I don’t think I have heard of core damage below the waterline ever. If one just pops a hole in it for a fitting then you are an idiot and deserve the damage."

Like this one on a high end motoryacht whose throughull fell out when I gave it a hand pressure jiggle. Thankfully bungs and an emergency pump saved the day. I can post photos of this stuff from supposedly high end boats all day long."

I agree balsa works great when done properly, I just don't see that very often.

One of the issues with infusion is that there is no way to confirm that the kerfs were ever filled without cutting it open (as evidenced by the Bertram photos I posted earlier). I have literally seen hundreds of such boats cut open and have rarely seen 100% fill of the kerfs between those blocks of balsa.

Seems we have several fortunate people here who have a different experience than I. Admittedly I have become a bit cynical after 30 years of inspecting crap from many builders. I trust none of them until I see it/check it for myself.

There are no kerfs with encapsulated block construction. The blocks are entirely separate, not grooved (kerfed). You are describing kerfed plank construction as used in the 70's and 80's.

With vacuum bag infusion, there is virtually no risk of untreated wood surface being left.

It's really important to distinguish between the types of construction -- they are as different as chalk and cheese.

Did you ever see a Swan or HR with core problems? Even once?

[Dockhead]

Originally Posted by s/v Jedi

I didn’t have motorboats in mind when writing that because yes, I heard many such stories about wet core and no sealing, let alone tapering to solid glass on them.

But many sailboats are done right.

All the balsa core I have seen is constructed as squares of end grain balsa glued onto a fiber scrim material. This allows it to conform to shapes and resin adheres very well to/into that end grain as well as around the squares to seal them.

TPI in Newport, RI used the SCRIMP method of vacuum bagging and resin infusion and this process is well established and known to provide these good results. AFAIK all the boats built by them since the early 90’s are done this way, incl. J boats, Lagoon and of course the Sundeer production series.

That's the modern way of doing it, as practiced by all the quality European builders of sailboats. It's vastly more expensive than the older methods, so don't look for it in mass produced catamarans or in motorboats.


Now deck construction may be different, as the balsa's tensile strength is needed for stiffness and so the separate blocks may not work. I'm talking about hull construction, where compressive strength is key and blocks are ok.

[Dockhead]

Originally Posted by s/v Jedi

Jedi is balsa cored throughout. But the cored is tapered out ending in solid fiberglass wherever a fastener goes through. This includes all of the hull to deck joint, at all the chain plates, thru-hull fittings etc. . .

That's the right way to do it, and all good sailboats built since the 90's are like that.

Originally Posted by s/v Jedi

. . . I don’t think I have heard of core damage below the waterline ever. If one just pops a hole in it for a fitting then you are an id|ot and deserve the damage.

If you just pop a hole in the cored part of the hull, when there are different spots of solid glass for through hulls provided, then you are certainly an idiot. But even then, resulting damage will not spread, with a properly done core.

I'm an active member of the Moody owner's association, where we discuss -- ad nauseum! -- all of the different flaws and problems with our boats (especially those dam*ed laminated teak toe rails, leaky Lewmar hatches, failed hydraulic swim platform mechanisms, etc. etc.). Not a single mention ever of any core problem, although all Moodys were fully cored since the late 80's. Same with Swan, HR, etc.

The OP will be hard pressed to find a quality boat built since the 90's which is not fully cored. AFAIK, besides cheap mass produced boats like Beneteaus, you can only find solid hulls in the occasional oddball retro boat, usually full keel, like Kraken, IP, etc.

The OP should check around about the reputation of whatever boat he settles on, but once satisfying himself that the maker has a good reputation with hull integrity, he shouldn't worry.

[smj]

Originally Posted by Dockhead

There are no kerfs with encapsulated block construction. The blocks are entirely separate, not grooved (kerfed). You are describing kerfed plank construction as used in the 70's and 80's.

With vacuum bag infusion, there is virtually no risk of untreated wood surface being left.

It's really important to distinguish between the types of construction -- they are as different as chalk and cheese.

Did you ever see a Swan or HR with core problems? Even once?

I’m pretty sure Boatpoker was talking about grid scored balsa not kerfed.