Who's qualified to do "detailed engineering analysis"?

TealTiger · Feb 26, 2012

Dear Ad Hoc,
Would you mind extrapolating? How much experience? What kind? Why?
Thank you.

kvsgkvng · Feb 26, 2012

strong reservations on /bamboo/epoxy/concrete/sealant/ composite material

Petros said: ↑

I am a licensed professional engineer with 30 plus years experience in aerospace structures, aerodynamics, as well as spent most of my career designing land based structures (buildings, retaining walls, towers, bridges, tanks, etc), and with a fair amount of marine and automotive experience as well. I am familiar with wood, steel, aluminum, concrete, and fabric structures using a variety of bonding or fastening methods, with some limited experience with composites.

We are collegues ;-) I beat you with experience though.

Concrete is not water proof, and bamboo will not bond to concrete reliably. Wow, that I strongly disagree with this statement! So even if you could get a bond, moisture intrusion will eventually break down the bamboo. There are reasons these materials are not used to make structures that are expected to last a long time.

Bonding epoxy? don't you use it on all dowels? Before pouring concrete -- smudge enough epoxy on bamboo and you will get double whammy, excellent bonding and watertight sheath. Don't forget to sand the bamboo for extra adhesion!

I can not see how concrete and bamboo composite could ever work reliably together. Even to get steer bars to bond to concrete it has to have ridges on the bars to keep it attached. Also concrete does not tolerate much flex at all, while bamboo will take quiet a lot, this kind of incompatible materials will only crumble away as it is loaded and unloaded in repetitive cyclic loading even if far below its tested strength. That was inaccurate. Principle of equal strain allows concrete to be reinforced with anything, including sowing thread. In case of bamboo, all you have to do is to convert concrete stiffness to bamboo stiffness and to design a proper composite material. However, to achieve sufficient carrying capacity under dynamic loading you would need a lot of composite reinforcement though. Your bamboo composite beam/plate will last as long as the concrete will. With the surface impervious sealer, it would be a looooong time.

Laminated Bamboo primary structure might have applications in hull structures, if it can be treated to resist rot. It would be interesting to make woven or laminated sheets of bamboo that could be used like plywood, or even better, cold form it in strips over a mold. It would be labor intensive, but so is most traditional boat building. Except you have the added task of gathering the raw materials and preparing it to make the beams, ribs, stringers and sheets you need.
If you want to see an example of bamboo laminate, take a look at bamboo flooring. It will allow to "feel" how it would behave. For marine application, the bonding should be done with water impervious materials.

Of course that means finding a suitable adhesive; epoxy, polyurethane, or perhaps reprisinol or Tightbond 3 (this is a brand name which is a common derivative of generic epoxy with additives). The strength to weight ratio of bamboo is not too favorable
WOW that is a very gross understatement! Bamboo is EXCELLENT longitudinal strength to weight material! Some of ancient bamboo reinfoced structures are still in existence in Cnina.
compared to other woods, nor its rot resistance. But if it your goal is to use low cost materials, and a suitable and acceptable adhesive can be found, and an acceptable way to make it more rot resistance can be found, it can be done.

If your intent is to use low cost materials to prove it can be done, there are lots of way to accomplish such an undertaking. Concrete has limited applications in smaller private vessels, in larger commercial vessels it can be made to work but there has not been a large whole sale shift to concrete for building barges and cargo vessels. There are economic reasons.

What design did you have in mind? Typically you would design the hull around your intended use, and the structural engineer will determine structural details; fasteners, beam sizes, hull thickness, etc. I would choose a proven design if your intent is to experiment with new materials or construction methods. Just as I would recommend you choose proven materials if you were experimenting with new hull designs. Too many changes at once means you double your risks and will not likely have a successful design.
Click to expand...

This is what I think - sorry for being a bit straightforward. I stumbled on this thread by accident and could not hold my opinion down when I see that it disagrees with mine. If you have doubts -- post the question on www.eng-tips.com there many knowledgeable engineers there and they can advise you in addition to these two opinions.
You can do anything, if you have money and time. Developing new technology requires a lot of initial research to establish many things. It does not necessarily guarantees that the result may be cost efficient compared to established techniques, if it is going to be a small-scale operation.

Look, the final thing is that developing new technology with new material will yield either of two things. The first the proper one would require lots of time, money and expertise. The second one would end up with building something which is going to fall apart after two months. It is like me - building "a new boat" when everyone is saying "get bigger and cheaper second hand one!" Yeah, I can do that but the fun would be gone...

If you go with unproven technology, you may end up with a cracked all over wreck in two month.

I would not want to occupy all the people reading this post with trade specific details and I do not solicit here any employment.

IMHO these things are done off the list. Regards.

viking north · Feb 26, 2012

Most questionable construction can be successfully achieved if enough funds are thrown at it, however an important consideration when posting an answer is it financially wise to do so. ---

Ad Hoc · Feb 27, 2012

TealTiger said: ↑

Dear Ad Hoc,
Would you mind extrapolating? How much experience? What kind? Why?
Thank you.
Click to expand...

Well, firstly you say you’re designing a 40-60’ ocean going cat. This is not Child's play…and then, on your assumption with concrete and bamboo, requires a working knowledge of these materials, not theory, actual real experience of using such materials and in different applications.

So, for the design of the ocean going cat, this requires a high degree of previous experience. Ocean going boats, of whatever description must have so many aspects taken into account, far beyond that of a simple GA. Thus you need a qualified and experienced (this is the key, experience) NA whom has designed ocean going cruising cats before. Anyone can draw a pretty picture...BUT, is is sfae enough, will it float, will it float upright under all expected conditions... what occurs when damaged, is it structure adequate in hurricane winds etc etc.

As for the materials side, books only teach you theory, not application. Exotic materials do not always behave in a classic manner, especially as noted in suppliers’ manuals. Thus hands on experience of using said materials in similar working environments are very important when dealing with "exotic" and compsite structures. If you don’t know how the material is made used, fabricated and effects of service history, then how can you design with it or properly?

Thus, you need an experienced NA, otherwise you’ll just waste time/money…and possible a life, if not careful.

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Who's qualified to do "detailed engineering analysis"?

TealTiger Junior Member

kvsgkvng Senior Member

viking north VINLAND

Ad Hoc Naval Architect

IBEX, who's going to Kentucky?