To balsa core or not to balsa core?

[ssullivan]

I looked at a Kelsall from the late 90's or early 2000's in that catamaran hunt with all the delaminted boats.

I can safely say, out of all the boats I looked at, his was in best shape. The process must have something going for it, as so many others were falling apart.

The Kelsall was still rock hard with no delam or water incursion detectable.

In fact, if I didn't go for the smaller cat for reasons of upkeep cost, his was my 2nd choice. Night and day the two boats were, but the little slow one made sense for my personal goals. The Kelsall was AMAZING though. I was drooling all over myself thinking about it.

Soooo very fast. Sooo very well built. Sooo very long and wide that I didn't want to pay for it all. lol

Originally Posted by BigCat

Hi, Catty

It would take a lot of guys to vacuum bag a panel 65' x 7' without RI. With RI you can lay everything out at your leisure, test your vacuum for as long as you like, and open the valves and watch it flow. If you want to speed things up you just raise the bucket. I'm going to use a squeal detector to find small leaks.

I have my resin infusion links online at a Yahoo group at:
Yahoo! Groups

This is Derek Kelsall's preferred method now, and I have seen lots of videos and photo essays of this. I haven't done it, but I'll start with a hatch, then a bulkhead, and do big panels like topsides and decks later. No moving on to larger panels 'til I get the smaller ones worked out with no problems.

You can see a long photo essay of a Kelsall workshop here:

KSS Workshop Colorado 2006

I already have the engineering on my unstayed masts-each mast holds 1200 sq. ft. of sail, is 17" in diameter at the base, and 8.5" at the mast head, with a wall thickness of .55". The layup is vinylester / carbon fiber uni, with some +45-45 glass against wringing strains. The USCG has accepted the engineering. The masts are 70' long, with 7' below deck to hold them up. The current cost of the carbon fiber for two of these masts is @ $30,000 (not each, between them.)

[BigCat]

Hi, Maren

Essentially, we have enough experience with these materials to know what has worked well in the past. We know that vinylester has worked out very nicely with foam core and balsa core, but that epoxy has worked best with attaching to planks of wood. Indeed, polyester has worked well with foam or balsa core.

Derek Kelsall says all the boats that he designed since the sixties with polyester / foam core are still going strong. He doesn't like balsa, because it can rot. Others say foam can degrade from water, too. It is certainly true that you want to keep water out of your cores, and it may well be more important with balsa than foam. I have had good experiences with balsa, and am not concerned, but I am using solid laminate below water, and along the margins of the decks where the handrails and mooring cleats are located.

The fact that J-Boats, Hatteras Yachts, Sweden Yachts, Viking Yachts, and Lagoon Catamarans are made with vinylester / balsa lends credibility to claims that the combination is a very good one.

Epoxy has the best adhesion characteristics of the the three classes of resins, and that seems to be needed when dealing with planks of wood.
I don't think there are any solidly pinned-down facts that explain this, though one could speculate about, for example, differential thermal or mechanical expansion characteristics.

[cat man do]

If, as even you admit

Epoxy has the best adhesion characteristics of the the three classes of resins,

Why wouldnt

J-Boats, Hatteras Yachts, Sweden Yachts, Viking Yachts, and Lagoon Catamarans

use it?

Why is it that if Poly and Vinyl are so good with balsa, that I can't find a pre cut kit boat made from Poly/vinyl and Balsa, Yet can find them made from Epoxy Balsa?

Why if poly and vinyl are so good with balsa are repairs to a poly/vinyl and Balsa boat done with epoxy resin?

Dont get me wrong, I have nothing against Poly and Vinylester resin and have used them myself...............................with foam.

Dave

[BigCat]

You may feel the need to double post this, but I feel no need to answer it in two threads. Read the composite thread, and the several dozen posts already made on the subject.

Blustering won't change the facts, no matter how loud you shout, no matter how long you rant, and no matter how many untrue assertions you make with no effort to document your absurd claims.

[cat man do]

Why absurd?

Even you admit epoxy is better

Epoxy has the best adhesion characteristics of the the three classes of resins,

Why use second rate materials?

Show me a kit boat from Poly Balsa or Vinyl Balsa?

(if it was so good wouldnt everyone supply these instead of foam poly/vinyl kits or epoxy/balsa kits ? )

Show me evidence of repairs to balsa, not foam like showed in your other post where they are done in Poly or Vinyl.

Nothing absurd here, just questioning your reasoning as to why you would choose a material that does not work as well as others by your own admittion.

Dave

[catty]

No catmando , the question is.... Why waste money on a resin that is dangerous to use and expensive, when another product will do the job perfectly well and has passed the test of time, for this particular application, namely, bonding to end grain balsa?.

Would you propose the use of gold instead of copper for your navigation light wiring?.

[cat man do]

Originally Posted by catty

No catmando , the question is.... Why waste money on a resin that is dangerous to use and expensive, when another product will do the job perfectly well and has passed the test of time, for this particular application, namely, bonding to end grain balsa?.

Would you propose the use of gold instead of copper for your navigation light wiring?.

None of that addresses or answers my above questions.

As far as the expense goes I have thrown 600 litres of epoxy to date at a 50 footer with about another 150 litres to go.

My expenditure on epoxy has been less than $7000.

If I had done it in poly, I may have saved a couple of thousand in resin, maybe.

What sort of % is this in the overall expenditure of a boat this size? Buggerall.


But using Balsa as a core material would have cost me more, and the total lack of longtitudanal stiffness of the core would have meant more glass and more resin to achieve the same panel stiffness.

Saving gone, weight added.


Health issues, Poly actualy makes me ill, just the smell of it gives me headaches, epoxy does not.

Again, build out of Poly, just dont try and convince me it is a superior resin to epoxy with Balsa.





Dave

[BigCat]

1) VE for flame spread rating! Why is nobody picking up on this? It is very important to me and to the USCG. When Gideon tested a panel of his layup, even covered with (apparently not very good,) 'flame retardant' paint, it caught fire so quickly and fiercely that the people doing the test had to run from the scene.

2) Epoxy has a proven track record of toxicity, unlike styrene thinned resins, no matter how little some people may like styrene. If it's giving you a headache, you need better ventilation.

3) Vosper Thornycroft chose VE for the world's largest single masted sailing vessel because of its working characteristics.

4) Price is 4th. to me. It saves me about $10,000 or $15,000 USD to use VE.

[David M]

In this day and age it seems that there has to be better material than balsa wood for hull coring. It seems to me balsa wood is used because it is cheap as opposed to there a being a better material available. Is there really nothing that is better and more resistant to water absorption?

Why take a chance at all with balsa wood if something better is available and in the big picture is an insignificant percentage of the total cost?

[jzk]

Originally Posted by David M

In this day and age it seems that there has to be better material than balsa wood to core a boat. It seems to me balsa wood is used because it is cheap as opposed to there a being a better material available.

Why take a chance at all with balsa wood at all if something better is available?

Does not balsa have excellent adhesion qualities?

[BigCat]

Balsa is not only cheap, but very strong. It is stronger than the foams usually used in coring hulls, less flammable, stiffer, and doesn't soften in the heat. If you'd read the specifications I have posted, most of your questions would be answered--look at the 'composites' thread, and the 'liferaft' thread, and follow my links. A lot of well respected companies already mentioned are using balsa / VE - if price were everything to them, they'd use ortho.

[David M]

It is a basic engineering concept that the greater the diameter of a tube, the stronger that it is going to be. If you compare two tubes made of the same material that also have the same weight per amount of length, the tube of a greater diameter is going to be stronger...even with a proportionately thinner wall in order to make the weight the same for a given amount of length.

Why is this fact not being addressed? Why not make the stringers hollow using the same material and wrap more material around the outside of the tube...effectively making it stronger than a tube that has balsa wood with a smaller diameter...yet is weaker?

To put it in a nutshell, the majority of your strength and rigidity is coming from what is wrapped around the wood and not so much the wood itself.....right?

You cant get tubes or even squares made of epoxy-glass or polyester-glass and then laminate the same material as the tube over that?

As an added benefit, a hollow core that is open at both ends sure as heck wont hold any water. If it happens to be bowed like a smiley face where the low point is between the openings it wont matter if water gets in there because there is no wood or anything to swell anyways...right?

[BigCat]

CompositesWorld.com - Composites Technology - Getting To The Core Of Composite Laminates - October 2003 for a non-technical discussion of cores, including documentation for my comments on fire retardancy in balsa.

While separation of the faces gives strength, they must be held apart by something which will hold them in that location. When cored laminates are stressed to failure, balsa stands up to more stress--documented on a post in the 'composites' thread in which foam vs. balsa laminates are tested to destruction under identical circumstances.

I have no comments on your proposed new product, except to comment on the use of stringers. Stringers are heavy because they must use a lot of glass to laminate them to the hull. I did the calculations, and was horrified by just how heavy a stringer / solid core hull would be when compared to a hull made with 9.5# balsa reinforced only by bulkheads and furnishings.

[Maren]

Originally Posted by David M

Why is this fact not being addressed? Why not make the stringers hollow using the same material and wrap more material around the outside of the tube...effectively making it stronger than a tube that has balsa wood with a smaller diameter...yet is weaker?
...
You cant get tubes or even squares made of epoxy-glass or polyester-glass and then laminate the same material as the tube over that?
...
As an added benefit, a hollow core that is open at both ends sure as heck wont hold any water.

This is one of the more novel feature I saw on FastCat435's site


"2. The inside stringers are made from carbon fibre and glass and double in function as air channels for your heating and air conditioning."

Actually I have been to most of the boat builders' sites, certainly all the ones on this thread. And, overall, I have respect for what each of them does and the product they put out. But I'm not sure they do for each other based of the tenor of the comments towards each other.

[BigCat]

February 2005 Alcan Baltek Corp. (Northvale, N.J.) has introduced for marine applications its new BALTEK Gold treated end-grain balsa core products, which carry a transferable lifetime limited warranty against decay. Under the warranty, the company says it will cover all costs necessary to replace or repair decayed BALTEK Gold core (up to three times the total value of BALTEK Gold in the boat) if decay is discovered within the first 10 years. After 10 years, Alcan Baltek will supply replacement Gold core only. The warranty will be extended by the builder to a second owner within 10 years of the original purchase.