Bamboo Core - What's Wrong With Idea?

[James Mills]

What is wrong with this idea?? Bamboo cut crosswise used as a core material. Build a hard chined or multichined plywood hull over forms using thin plywood. Bamboo cut into rings 2" or 4" or whatever is appropiate. Glue the rings onto the plywood. Cover then hull with bamboo rings all over it with another layer of thin plywood. Encapsulate the whole thing in glass and epoxy resin. Cheap and light. Balsa has been used for years as a core material and it rots very nicely when wet. Suppose you could use some pour in place foam between the rings to bond them all together prior to outer layer of plywood or pour foam into all of it if voids are undesirable. Not familiar with cost and stuctural properties of pour in place foam.

The want-to-be boatbuilder/dreamer with more time than money, could have his bamboo patch out back and harvest the core material over years time as he got closer to actual boatbuilding.

[PAR]

Do yourself a favor and look up the mechanical properties of typical core materials and compare them to bamboo cut as you suggest. The labor would be much higher, the weight would be much higher and the cost, more then conventional cores. Attachment would be problematic at best, more of a stitch and glue deal, with a bunch of rings, extra lumber/plywood, fastening another plywood skin, additional labor tossed into the mix, just because you have more time then money, right?

Why make it hard on yourself? Build a single or multiple chine single skin hull of ply. If you like extra planking, try double planking. Want to save weight, wholesale? Try composites.

Bamboo is a weed, found throughout the far east. It's so bad in some places, whole forests are burned, but it returns the following year. They don't want the stuff, can't get rid of the stuff, hate the stuff and would love nothing more then to have it get a foot hold over here so we can understand what they've been bitching about all these years. It's not a very good wood and can only be had in short pieces (with reliable properties) Boat builders like manly lengths of lumber, nice straight grain slabs of meaty chunks of wood.

Tell you what, if all their teak supplies come with their wimpy bamboo then it would be a deal. We can continue selling them over priced stock from the northwest of our country (they'll continue to process it and sell it back to us) and we'll toss in say North Dakota. Who'd miss it except folks living close to the state line in South Dakota . . .

[SailDesign]

PAR says:

<snip rant>

Geez, PAR, get out of the wrong side of the bed this morning? Late night last night.


Either way, maybe a good bike ride will cure that.
http://www.americanbamboo.org/Genera...ooBicycle.html

Steve "just kidding, dude, just kidding...."

[Black Swan]

Well... not to rain on your idea, I appreciate the innovative approach, but...

A double plywood skinned / bamboo cored / polyester (vinylester?) resin or epoxy coated hull? You would probably still have to use fabric, or mat or a combination of both to achieve the needed compression strength of the hull surface. Just gelcoating the plywood won't do it.

Yes, balsa was used as a core material by some manufacturers for decks and (yikes) hulls. For a group of essays on the wisdom of this method, go have a look at David Pascoe's website on Marine Surveys.

Is the idea innovative? - yes. Is it practical for a "one-off" project? Probably not. Is this something that a boat manufacturer might become interested in? Only if it can be demonstrated to increase strength, reduce weight, reduce material costs, reduce labour costs, and be marketable to the boat buying public as a technological innovation. Should you fool around with it just to see what you can achieve? Absolutely... Are there any other projects that this "sandwich" might be appropriate to? Probably... strong lightweight roofing panels, wall panels, floor panels, doors... who knows, you might just be onto something.

Although the idea of cross cut bamboo doesnt appeal to me, bamboo is an interesting material, good enough for fishing poles. THe lengthwise fibers must be great in tensile strength though I havn't checked. MAybe crush the poles and harvest strips to use like fiberglass cloth...a grow your own material. Doesn't sound economically feasible but who knows where you can go with it? Would be fun to fool around with.

[dougfrolich]

I have to take issue with Black Swans comment "was". Balsa core IS used as core material for decks and if I may -- Still without "yikes" used as a core material in hulls above and below the water line. Balsa is one of the finest core materials around, especially when used with High Modulus Skins. Just dont go around poking holes in them without knowing what your doing.

THe more I think about it , the more I like the idea too. Maybe take bamboo in a big rack/plate with hollow bamboo positioned in the rack , then press into some kind of normally too soft but light foam sheets and cut off the bamboo stalks top and bottom of the sheets. Think of holding a bundle of straws and stabbing into a piece of bread. Don't freak out . This is pure brainstorming designed not to be practicable but to inspire other ideas.

[Black Swan]

I stand corrected Doug. Yes, balsa is considered by many to be a fine coring material, and methodology has improved exponentially since its' introduction. Saturation techniques, more solids being used in areas likely to be utilized for attachment, the continuing development of material testing technology, advances in computer design, the evolution of exotic resins, the use of HMS... all have contributed to a far higher success rate and reliability for all core materials. Some have evolved, some have undergone refinements, some have disappeared. Some manufacturers have abandoned coring, and some have embraced it.

And indeed, the "problems" that I have encountered with balsa cored structures have nothing to do with the balsa itself, they have all come down to the methods used with regard to penetrating the cored material, the purpose of the penetration, (structural stresses being applied to the area or simple anciliary installations) and methods used in sealing the penetrations. As I understand it, quantum improvements have been achieved in contemprary use of all coring materials.

Most of the cored decks and hulls that I am called upon to assess and repair were manufactured very early in the learning curve of the use of these materials. Consequently I find that many assumptions were made about the mechanical properties of the material which simply did not turn out to be true. Exposed to water, the cores did not stand up as well as the materials that are now used for backing plates and attachment points. As stated, this is not the fault or a bad property of balsa, it was just a part of the learning curve. The "yikes" comment was simply meant as an opinion, based on my experiences in repairing problems that have come to me. Of course, I don't get to see the cored hulls that DON'T have problems, I just get to fix the ones that do. Repairing a balsa cored FRP hull that has suffered a water intrusion, either from impact or a "sealing" problem is not a pretty or simple process. I am often the one who has to break the "bad news" to an unsuspecting owner, that an expensive repair is on the way. That weeping through hull fitting can turn out to be a multi-faceted major repair if it has been un-noticed or ignored long enough for the core to de-compose. That always gives me a "yikes" moment.

As I said previously, for an interesting and detailed perspective on the use of core materials in boat hull and deck construction, I would recommend the Marine Survey essays by David Pascoe down in Florida. His wealth of experience and articulate "no nonsense" approach brings yet another opinion to the table.

[edneu]

Bamboo is split and laminiated for fly rods which are very strong and flexible for their weight.

There are some flooring products and cutting boards that are made from what appears to be end grain bamboo. As others pointed out it is heavier than balsa, and probably subject to the same deterioration if not properly encapulated against the elements. The makers of these cutting boards claims that it is 15% harder than maple.

A huge benefit of bamboo is that it grows really fast and is really easy to grow.

[Steve Clark]

This could just be me, but I think cutting the bamboo up into little tiny peices and using it as core material would be a mis use of bamboo prime virtue.
Bamboo is long and relatively straight. It is damn strong nd is used instead of metal tubing in many temporary structural applications ( like scaffolding).
It is relatively light in it's hollow form, but the wood fiber portion is relatively heavy.
So it seems to me that this would be good stuff to use as stringers and struts. Uffa Fox used to use it for masts and booms. Boathooks, paddles and oars also seem like likely canidates. I used it for battens when I was a kid.
For hull construction, I might consider "strip planking" out of bamboo. Obviously there would be a lot of filler required to make the skins smooth, or maybe one could use a stringer frame and light skin aproach happily. Might be the ultimate compliment to Platt Monfort's geodesic boats or some other skin boat concept.

[tom28571]

Bamboo is wonderfully strong stuff but using is in little slices as a core material is way overkill and probably a bad idea. Since it grows so fast, I keep thinking that someone will use it as structural fiber in the same way the building industry uses tree fiber in OSB, flakeboard and glulam beams. I suspect that bamboo strength/weight is very high compared to other wood fiber.

I wonder what a foam panel with bamboo fibers mixed in would be like?

The very best, or at least highest priced, fishing fly rods are made of laminated (lengthwise) bamboo strips.

[Kyle]

We install quite a bit of bamboo floring in resturaunt applications. The product is 5/8" thick and comes laminated with numerous strips to form whatever width of flooring is desired. Incredibly resiliant to the humidity swings that N.E. Oklahoma sees, 20% up to 100% for sustained periods. The stuff is typlicaly imported from China. When ripped it laminates beautifly into radius stair treads. No clue how it would behave below the waterline. I'd love to know however. I can try to laminate with system 3 epoxy and plunk a tread under water for a couple of months. If there would be a better goo to use let me know and I'll try it also.