Balsa Core

[roverhi]

Have a 45 year old boat with balsa cored decks and has almost no issues with core rot. Problem ares like stanchion bases were in solid glass. With the exception of a couple SPOT fixtures, everything was properly bedded and had no leaks. The areas that had leaks with core rot were very limited in size and easily filled with thickened epoxy. If a boat was built right and hardware properly bedded core leaks shouldn't be an issue. Have gone back and removed every fitting on the deck, routedneeded anytime the boom is out to the point that the traveller/mainsheet does allow enough down force to properly flatten the sail. Letting the boom rise to bag out the sail and dump air is only a temporary move to reduce healing moment till you can reef or the momentary increase in wind velocity passes. If you aren't using the vang when it's needed, you out the core with a Dremel 199 bit, filed the puka with thickened epoxy, redrilled the holes, and rebed dead the fittings with LifeCaulk or Butyl. Should be good for the next 45 years.

One advantage of balsa core is it is end grain. Water that may get in is confined to the cells immediately adjacent to the leak. Rot cannot progress until it breaks down the cell walls before it can spread. That makes core rot a slow progression. Plywood core is very prone to large areas rotting because water wicks out along the grain making large areas wet

[barnakiel]

I like balsa core. I do not like idiots who will drill holes in balsa sandwich.

b.

[Cheechako]

Originally Posted by roverhi

Have a 45 year old boat with balsa cored decks and has almost no issues with core rot. Problem ares like stanchion bases were in solid glass. With the exception of a couple SPOT fixtures, everything was properly bedded and had no leaks. The areas that had leaks with core rot were very limited in size and easily filled with thickened epoxy. If a boat was built right and hardware properly bedded core leaks shouldn't be an issue. Have gone back and removed every fitting on the deck, routedneeded anytime the boom is out to the point that the traveller/mainsheet does allow enough down force to properly flatten the sail. .......
One advantage of balsa core is it is end grain. Water that may get in is confined to the cells immediately adjacent to the leak. Rot cannot progress until it breaks down the cell walls before it can spread. That makes core rot a slow progression. Plywood core is very prone to large areas rotting because water wicks out along the grain making large areas wet

"If a boat was built right and hardware properly bedded core leaks shouldn't be an issue."
Yeah, but that's a huge "IF"!

"Water that may get in is confined to the cells immediately adjacent to the leak."
From what I've seen (and experienced on one boat!) it does travel through. I had about 12 ft of travel and about one foot wide from one thru hull! The boat was 6 or 7 years old.

[Schrewsburyduo]

Get a Contessa 32 Original English build (build by Jeremy Rogers, not the Taylor Canadian version!). Solid GRP deck. Sadler said it is springy and it's supposed to be (due to solid glass). Several owners reinforce it with foam core etc but that defies the design which uses the flex to absorb shocks etc.

So there's your answer - you only need $50-100K for a 20-30 yr old iconic blue water, tiny (by today standards) 32, but it will take you everywhere, is great to day-sail etc., and has no balsa.

One more comment - if you are worried about balsa rot, in no circumstances don't ever get a teak deck boat. On those boats water intrusion chance is increased 1000 fold by the screws used to fasten the teak to the deck.

For all it's worth, I had two run of the mill production boats with balsa cored deck, and no rot at all. If they have been well cared for they last. The way the balsa is used (end grain) makes sure that any water intrusion stays and does not travel via capillary motion. At most you might have to keep an eye around chainplates, and any hardware some PO might have put in without drilling and filling with epoxy. You can find old boats with no issues. Or save up and get a Contessa or something similar. 1979 Contessa 32 Sail Boat For Sale - www.yachtworld.com

[rognvald]

Originally Posted by skipmac

Don't know the specifics of the CT but are you sure the decks aren't cored? Even if the decks aren't cored they are teak which I assume uses about 11 zillion screws into the deck to attach the teak.

Skip,
I'm sure the deck is solid glass since I helped my friend ,who owns the boat, with several deck repairs. The information is also is stated in the original sales brochure. It does, however, have teak decks that bolt to the glass below which have the obligatory "11 zillion screws." As a side-note, I was very impressed with the sailing characteristics of the CT out in the Gulfstream with fairly light winds( less than 10K) and large swells. The boat accelerated very quickly once we had the feathers up and sailed in the middle sixes to seven on a close reach. Pretty impressive for a 65,000 plus pound vessel. In comparison to my Pearson 34-2, I felt like I was on a cruise ship. Good luck and good sailing.

[sailorboy1]

The problem isn't with the coring, whether it be balsa or plywood. The problem is that holes get drilled into the coring.

More modern boats prevent this by not having coring at places when holes are going to get drilled! But if you later decide to drill one somewhere that they didn't plan you need to take out the coring beyond the hole and fill with epoxy etc. so that the coring doesn't get wet WHEN the fitting starts leaking.

[lifeofreilly57]

Most cored boats are cored to the waterline and then solid glass from there, note, I said most, not all.
I've had cored boats and agree with all the previous comments, it's a game of Russian roulette when buying used, it all depends on the previous owner (owners) and how well they cared for them.
I found on the last one I had to rebed the deck hardware on a rotating basis with different sets of hardware getting done every other year. THis made it so I didn't have any huge projects in any one year and kept the leaks to a minimum.
Sealing all the through deck holes with thickened epoxy is a good idea, if there was limited moisture ingress you can speed the drying process by pouring in rubbing alcohol and then allowing it to dry out. Rubbing alcohol is hydroscopic and will bind with the moisture and then help it evaporate more easily. In cold months I've done this by covering the deck, pouring in the alcohol, allow it to spread then heated the boat from inside to allow the moisture to evaporate. It's not a fast process so is best done in the off season if you are in an area where this is possible, and again, only for limited moisture penetrations.
Once done and the through deck holes sealed at the edges properly you should have no problems for years.
If the boat has major moisture penetration in the core and is in a climate where there are big freeze/thaw cycles your better to walk away.
If your looking at any boat you can be assured the deck is cored with something, be it balsa, man made coring, plywood, planking, you name it, no used boat will have a perfectly dry deck unless it's been stored inside for some time.

[Dockhead]

Originally Posted by rognvald

Skip,
I'm sure the deck is solid glass since I helped my friend ,who owns the boat, with several deck repairs. The information is also is stated in the original sales brochure. It does, however, have teak decks that bolt to the glass below which have the obligatory "11 zillion screws."

The 11 zillion screws are a liability on this type of teak decks, and an even bigger liability if the deck is cored. A much, much better method of attaching teak decks is with glue and without screws. This technique only appeared around 2000, so won't be found on old boats. As far as I know, this is now the way most or all of teak decks are attached in Europe; I don't know about the rest of the world.

I almost bought an Oyster 485 -- had a deposit paid -- which had had much of the interior joinery destroyed by leaks through the deck through such screw-holes. When I realized that not just the joinery, but the deck cores would have been ruined, I backed out of the deal. Imagine such a defect from such a highly respected, very expensive maker. Probably an isolated screwup, I guess.

The decks were already pretty knackered, too -- bungs coming out, ridged, split at the screw holes in places. The boat which I then proceeded to buy already used the new type of teak decks. Although she was only one year newer (2001 versus 2000), the decks were incomparably better, almost like new, in fact, and they are still excellent more than five years later -- better at 13 years of age than the Oyster decks were at 8 years of age.

So another thing to keep in mind when you're judging construction techniques -- they evolve over the years, sometimes radically. Teak decks are much better these days than they were before 2000, last much longer, with less (or zero) risk of causing leaks. Same thing with balsa coring -- the way this is done nowadays is simply not comparable with balsa cores from the '70's or '80's when the technique was still experimental.

And one more thing: Any construction technique is going to be more or less appropriate depending on the level of care and workmanship used in building the boat. Balsa coring, which is higher performance, more complicated, and more expensive, is naturally more demanding and less idiot-proof than solid glass, which is weaker and heavier but simpler and cheaper. So in sum, if you're going to buy either an (a) old; and/or (b) cheap boat, balsa coring is something the think carefully about (and survey carefully). In either a (a) newer; and/or (b) high quality, expensive boat, there's not much to worry about in most cases, as long as no one has been hacking holes in it.

[clockwork orange]

Originally Posted by capttman

Most balsa used today and as far back as the 90's was impregniated with resin which helps it resist breaking down. It is also laid on edge as it is cubed and held together with a thin sheet of glass. U would not rush to the conclusion just because you had a leak you have a problem.. Oh some do but most dont


Sent from my iPhone using Cruisers Sailing Forum

What a load of misinformation, balsa today is not impregnated with resin, nor would you want it to be, what you may be thinking of is a grade that is available where the surface is pre sealed to reduce the absobsion of resin into the core, it is not all made that way, its the builders choice. It in no way reduces water getting into and migrating throughout the core from poorly bedded hardware because it is only a surface coating applied to the end grain. Also, balsa core has always been end grain blocks, either glued to each other to make rigid sheets ,or bonded to a light fiberglass scrim on one side to conform to compound curves as in female molds.The pre sealing does not help the balsa resist "breaking down", it doesn't "break down", as long as it is kept dry it will remain the same as it was when it was built indefinatly. Balsa has never been used in a face grain form as a core in production boats. So, in fact, the core used in production boats today is pretty much the same as was used 40 to 50 years ago.

Steve.

[clockwork orange]

Originally Posted by sailorboy1

The problem isn't with the coring, whether it be balsa or plywood. The problem is that holes get drilled into the coring.

More modern boats prevent this by not having coring at places when holes are going to get drilled! But if you later decide to drill one somewhere that they didn't plan you need to take out the coring beyond the hole and fill with epoxy etc. so that the coring doesn't get wet WHEN the fitting starts leaking.

There is nothing modern about not having core where hardware is to be installed, all the lessons of how to properly build a cored structure were learned very early on in the history of composite construction, its just that a lot of schlock builders choose to ignore them. I am appalled at some of the build practices used by the likes of T P and others building boats like J boats.

Steve.

[colemj]

Originally Posted by Cheechako

"Water that may get in is confined to the cells immediately adjacent to the leak."
From what I've seen (and experienced on one boat!) it does travel through. I had about 12 ft of travel and about one foot wide from one thru hull! The boat was 6 or 7 years old.

It is very difficult, even with core bond compound and vacuum bagging to get a completely void-free layup against the core. There always exists a few channels within a layup. If you happen to be on the short side of the odds and have a wet hole near one, then water can wick and travel. Likewise if you have a resin-starved area.

Manufactured panels like Duflex seem to do a good job with quality control. Balsa is one of the best cores in almost all aspects, but it requires much more control of the layup to be good. Having non-cored areas for ALL penetrations helps tremendously.

If you are looking for a true core material nightmare - its name is plywood.

Mark

[Dockhead]

Originally Posted by colemj

Balsa is one of the best cores in almost all aspects, but it requires much more control of the layup to be good. Having non-cored areas for ALL penetrations helps tremendously.

Indeed. And what makes balsa truly great is that it is not just a filler, like foam is, but it is an immensely strong material in its own right -- stronger than steel weight for weight. Because it's not dense, you can fill a composite structure with it and get the beam from separating the skins, but it plays its own serious role in the strength and rigidity of the combined structure. Then if you use an aramid outer skin like Twaron or Kevlar, you have one of the strongest and lightest structures produced by mankind at any price accessible to mortals.

[cpa]

After rebedding all of the deck hardware on our Compass 47 (Kearley Ltd Built). I can attest that the only area on the entire boat that is cored is the aft 1/2 of the cockpit(maybe 3-4 feet) and the first three feet of the foredeck. Everything else is solid glass with stringers underneath. The bow section is dry and I recored the cockpit core with Coosa BW26. I am hoping to be good. Here are a few pictures from underneath.

[clockwork orange]

Several people have repeated the balsa manufacturers spiel about water not travelling laterally due to the cell wall structure, this is absolute garbage, if it were true the rot would be confined to the immediate area of the penetration but of course this is not so. Now in lab tests it may be correct but in the real world the water can travel a great distance by way of the slits between the blocks. By the very nature of the way scrimmed balsa is used in a female mold the slits are open on one side creating hundreds of open pathways for water to travel. In theory the core should be draped over something curved and resin coated to try to get resin down in the slits but it is rarely done and it really does not get the job done so water travels and large areas rot. These days now that we are all resin infusing its a whole different situation as every crack, crevice, seam etc gets filled with resin and any leaking fastener truly is confined to the block it is in so there are no real drawbacks to using balsa, especially now that we can get it in a density close to H80 foam.

Steve

[Island Time O25]

After reading this thread I wonder how many members of this forum had catastrophic boat failure due to wet deck only? Not near misses, not "what might have happened", not "few years from now", not "wet deck and x, y and z", etc. but real boat loss due to only the deck core being too wet. Please let us know if you had such a failure.