Is Balsa really that bad ??

[rwatson]

Just had a read of the Australian catamaran magazine "Australian Multihull World" may/June 2009

Our mate, Derek Kelsall had an article in there, where he advocates banning balsa as a core material.

He states there are a plethora of articles on the internet on the "wet balsa problem".

I understand most end grain balsa is encapsulated in either Vynelester or Polyester, which is not as waterproof as Epoxy. is that the problem?

Is it really that bad - what have people found ?

[oscarvan]

It's cheap, it's strong, it's easy to work with. If it gets wet, it rots.

[rwatson]

Is it really that cheap ? - my rough calculations make it around $85 per square metre for 1/2 thick. That is more expensive than strip planking in Western red cedar here in Australia.

I suppose you would save on Epoxy V GRP ....

[TeddyDiver]

Polyester is defineatly a problem. Another problem is that balsa cores aren't excactly encapsulated, instead only on the laminate sides, not inside the core itself (compare to striplanking where is a real encapsulating) so a single small hole (besides the sweeping water throw polyester) will destroy the whole boat..

[CDK]

If weight is a major consideration, balsa is frequently used. For all other applications, any other kind of much cheaper plywood -impregnated or not- can be used.
And Glastron nowadays builds all small craft under 27 ft. without any wood because they use polystyrene foam as a core material. Elan, a European builder uses carton in the shape of egg boxes for their cheap fishing boats....

[lymanwhite]

I've had esperience with end grain balsa layed up in a mold with carbon and epoxy, then bagged and heat cured.
There were some 20 - 25 boats pulled with these materials as I recall, about 10 years ago.
There were some decks that experienced areas of de-lamination possibly due to too little epoxy in the layup. These and most problems were due to deck fittings done wrong, allowing the moisture to get to the balsa. This would be a problem with any core. One reason we chose end grain balsa is that it tends to isolate moisture to the area of penetration. Foam can allow moisture to travel via flexing and can create a delam that can be a bigger area by comparison.
Also end grain balsa breaks along the line of the grain, forming a clean edge for repairs. Foam tends to crush by comparison.
Aside from these few isolated problems the balsa, carbon, epoxy schedule is awesome. Very hard, strong, and repairs and deck / hull fittings are straight forward.
I still have one of these boats and would recommend balsa, although most modern layup schedules whether foam or balsa or another core are all pretty close in performance. I find the biggest variable is in the knowledge and skill of the craftsman.
Also Balsa is an old boat building core technology, while foam is much newer.

[Manie B]

My 2 cents

In my travels i have seen some very bad balsa jobs

Either it is too difficult to work with, or poor workmanship, or what ever

The boats that i saw with horrendous balsa delamination were even "repaired"


These boats look great when new, and the first owner may not notice problems. But after 2 maybe 3 years the second owner lands up with a pile of absolute junk.

The combination of balsa and polyester is poor, which is rife around here.
I can well believe that balsa and epoxy could be great BUT you need skilled labour to do these jobs. Unfortunately my country like many others are been used as "cheaper labour" to build boats, i can assure you there is nothing "cheap" about unskilled labour and unscrupilous "boat builders"

I dont like balsa because i have yet seen and old balsa core boat without serious problems, I have been on rust buckets and plywood "wonders" that are absolutely fine and safe.

I cant say that balsa should be banned - Derek Kelsall has got infinitely more knowledge than me - but i believe that there is nobody around here that could do a decent job, either building with balsa or repairing it.

[Stumble]

The problem is not with Balsa but with the lack of enginearing that goes into the design, or with the lack of understanding of how to properly protect it from water damage. The problem is that ANY core material is suceptable to water damage just of different types. Foam can litterly be pulverized when water gets into a core by a process called hydrolic erosion, balsa rotts, not much else is light enough to really be used as a core.

Here are a few articles that do a good job of explaining the issues:

http://www.yachtsurvey.com/core_materials.htm
http://www.yachtsurvey.com/cored_hull_bottoms.htm
http://www.yachtsurvey.com/more_on_cores.htm


Personally I see it as a problem with the process of using a cored design, more than with the core material itself. And Balsa is still one of my favorite core materials, but it does require, like any other highly engineered structure, proper maintenance and care.

[PAR]

There's nothing wrong with the material. In fact, it's quite difficult to find a suitable material that can equal or exceed the performance of end grain balsa in cored construction, all things considered.

Most manufactures have recognized the need to use better resins and engineer tolerant laminate schedules.

In the end, when you look at the millions of balsa cored boats, the vast majority without issue, it's clear the small percentage that have problems are usually owner or damage related, which has nothing to do with material choices made by the designer.

[dougfrolich]

I agree with PAR!
I was just sailing yesterday on a Balsa Cored Santa Cruz 52 Built in 1992 and still as sound as the day she was built ---after over 100,000 miles under her keel. High Quality Materials, High Quality Workmanship, High Quality Product.

[eastcape]

Educating the general public on the correct methods of installing fittings through End Grain Balsa Cores is a difficult task, but would be a very good place to start.

All the failures I have come across in 9 years of using End Grain Balsa panels stems from someone adding a fitting to the vessel and incorrectly sealing the End Grain Balsa Core material or not sealing it at all. There are correct methods for working with this material and in the wrong hands will lead to problems down the road.

End Grain Balsa Core is not for everyone. It should be designed, manufactured, and constructed by experienced personnel. Owners should be educated on how to maintain their vessels and any modifications later should be made by experienced builders.

The ocean is scattered with success stories, but then again you never read about successful projects.

[mark775]

My boat was built in 1979. I replaced the balsa deck to a different design in 1989 and there was no sign of any problem with it.
laminate schedule; 2 x 3208 BTI, 1 x 13oz mat, 1" balsa, 1 x 13oz mat, 1" balsa, 2 x 3208
I have had four wheelers dropped from a crane because of choppy water, 10,000lbs of lumber, skiffs dropped from rail high, and 400lb halibut doing their best to de-construct, all without so much as a groan from the deck. A 11/2" camber helps but the deck is stout and watertight (I cut a hole two years ago and it was dry and still one piece.
When I build my dream boat, it will be full of high tech materials and design... and a hell of a lot of balsa.

[Landlubber]

I think mostly materials are damned by the builders of poor quality constructions. Such as ferro....personally, not for me, but in fact, if done CORRECTLY, it is a century long material to use.

End grain balsa has many advantages, so do most other suitable boat building materials, but the correct usage of these materials is the determining factor in their longevity.

Cost of construction and time of construction are the commercial determinations of the "best" materials for the purposes of boat building, removing the cost and time factors certainly will change the build quality of any boat, and the end grain balsa arguement is affected by these parameters.
Non compliance with known world best standards will render any core material unsuitable.

[mark775]

By the way, as I look at the picture I drew on "paint" ( I don't have a nice rendering program), I thought I'd go off topic a bit about cutting freeing ports at hull/deck joints;
I believe that ports should be cut two inches up the hull side to avoid a delam at the juncture. Also this will prevent stains (fish scales/blood, mineral stains) to the hull sides. Also, this will allow freeing port holes to be aligned for esthetics rather than just follow the deck-line which may be different than the hull lines. Of course this means cutting scuppers in the horizontal, not-cored area - plan for this before deck layup. WHAT? You don't have freeing ports - only a little plastic deck fitting in each corner of the cockpit?

[rwatson]

Originally Posted by Stumble

The problem is not with Balsa but with the lack of enginearing that goes into the design,
Here are a few articles that do a good job of explaining the issues:

http://www.yachtsurvey.com/core_materials.htm
http://www.yachtsurvey.com/cored_hull_bottoms.htm
http://www.yachtsurvey.com/more_on_cores.htm

Great links Mr S. Thank you very much.

As I am in the process of deciding on materials for my next boat, this has been a great contribution.

All the other points raised are very, very usefull as well -the 'skill of the builder' theme raised in so many of the comments seems to be a huuuuge part of the equation.