Bronze Frames

[Scott Carter]

Plank on frame construction has been around for centuries, and just about every possible twist on a new idea which is an innovation of an old idea has been tried. We've all seen some pretty crazy ideas tried, too.
This is a hypothetical question in two parts. The frst is: Has anyone ever seen a vessel, of any size, which utilized bronze frames? Not just floors, but full frames, then planked conventionally?
For the second part of the question I'll acknowledge the obvious drawbacks and benefits so no one else has to waste their time pointing them out. Cost leaps off the page as being the biggest con. Why don't we just gold plate the boat nails while we're at it? OK, so that biggy aside there's also the technical challenge of getting them cast. That's do-able for sure by the right foundry with the know-how and proper equipment. Attaching the planking would be a challenge, but again, do-able. Any ideas there?
Pro's - the obvious biggy is a toss up between longevity and structural integrity/stiffness/strength-to-weight, which all tie in together eventually.

The point of this post is to collaboratively discover how this could be done and what some of the possible hurdles (both in building as well as future maintenance) would be.
With no other constraints on the design features, what are the points, both pro and con, of such an approach? As we all know, big vessels and small vessels, sail and power, are approached differently on many levels but we don't have to constrain this conversation to any one type.
Let's get out of the box for this one.
Thanks for your brainstorming.
Scott

[PAR]

The answer is yes, Herreshoff was well known for "composite" (as it was called then) construction.

The frames don't have to be cast, they can be cut and welded from flat stock just like other metal builds.

Even battleships were built in composite, mainly to compensate for the fact that a iron clad hull could not be covered with copper therefore had to be dry docked once a year to get rid of barnacles and fouling.



Herreshoff made the 43 meter "Defender" with a draught of 6,50m and 150 tonnes ballast (55%), she was made of bronce plating on nickel steel frames with a aluminium deck! One can easily imagine the problems she encountered!?



Btw. Max Oertz did the first all Aluminium yacht in 1894 following composite experiments!


Regards
Richard

[Tad]

Originally Posted by Scott Carter

Pro's - the obvious biggy is a toss up between longevity and structural integrity/stiffness/strength-to-weight, which all tie in together eventually.

That I don't see....

For me the biggest question still remains, WHY?

The long-term structural integrity of dissimilar materials remains questionable, I think you need to run a 50 year experiment before I plunk my millions on this.

In the 1990's Legendary Yachts built a few steel framed mahogany planked boats, including the 72' Radiance, a Ticonderoga copy. They are still trying to sell them, even after switching to all cold-molded construction. The market is certainly not asking for this.

As Par says, welding up the frames and bolting the planks on would be a simple problem.....it's just that no ones interested.....

[jehardiman]

yes, most of the later clipper ships were of composite construction (i.e. metal frames and wooden planking). The only advantage to be gained from composite construction was to reduce the non-paying deadweight and volume in high speed (i.e. high value cargo) merchantships in the days before easy and cheap all metal construction. Composite construction started about 1850, peaked about 1865, and dissappeared by 1880, mostly due to changes in iron and steel industry which made rolled plates cheap. Of course metal floors continued in wooden construction for many years because it solved the difficult keel to 1st futtock structural problem.

As far as gold plating goes for fastening, it is too soft to use as is or plated on. Just use Monel, it's about the same cost, lighter, and much better strength wise. FWIW, gold plating is used as a cost savings on high end yacht fittings. It costs less than having to keep a crew to polish the brass constantly.

Finaly, as an aside about the "Panzerschiffes" or more correctly "protected crusiers", there was a more compelling reason for the construction method. Protected cruisers constructed in the mid 19th century had, from the inside, an iron-wood-steel construction above the waterline and an iron-wood-copper below. The reason for the wood was to back the brittle armor against spalling, it was not for strength of the hull or watertightness. The wood was later despensed with after the introduction of face hardened armor about 1885. High speed iron merchant ships of the time also had wood staving below the water to afix the copper to.

[Crag Cay]

Spirit Yachts builds many of its strip planked wood/epoxy on welded stainless steel frames.

They seem to have plenty of customers.

[Scott Carter]

All good background folks. Thanks. I'll give a little more information since the point's been raised. The requirement for this hypothetical large sailing yacht is that it be planked in wood and carry a traditional overall look. So Tad, the dissimilar metals concern goes away for the most part. She won't carry payloads other than passengers.
A big reason for looking at metal frames would be to reduce the amount of timber used, both for envirnomental as well as long-term maintenance reasons.

[jehardiman]

Timber planking over metal frames will not reduce maintenance unless you use monel or bronze frames and bolts, and neither one of those is particulary green. Steel or iron, the two greenest materials, will be nothing but a maintenance headache.

If you want a traditional looking vessel that is environmentaly friendly, do it the old fashioned way and build it cheap out of cheap wood and then strip it and build a new one every 5 years....The reason old yachts aren't around is because they were build as cheaply as possible, used hard, and put away wet. Look at how C F Adams III used his boats...

[Scott Carter]

Well, this wouldn't be a "throw away" yacht. And building it as cheaply as possible isn't an approach I'm comfortable with in any field. What I'm searching for here are methods which are proven (thanks for all of the background on this approach everybody) and which will add longevity (not 5 to 10 years but rather 50 years) to this hypothetical vessel.
Jehardiman, that's a good point about bronze not being the greenest material, but we can't make everything from hemp and bamboo. Or can we ;-)

What about interaction between certain wood species and bronze? With or without oxygen? What do we know about accelerated wood decomposition or accelerated metal (bronze/aluminum/stainless are the likely candidates) oxidation when wood comes in contact with metals under the right (or wrong as the case may be) conditions? Any texts which anyone knows of which address this topic specifically and in any great depth? I know metal to metal interaction (electrolysis, etc) is thoroughly understood and documented, but what about various wood species vs. various metal species?
Composite construction almost certainly went out of vogue due to wood planking no longer being the only option. But when it was the only option it was used because frames of___(fill in the blank with metal species here) brought certain inherent advantages. I'm looking for these advantages, as well as their flip-sides, when used with timber planking of _____ (fill in wood species here).

[jehardiman]

Cutty Sark was teak over iron, and many of the american composite clippers were elm over iron. Iron was selected because it was strong and light compared to wood and less expensive than bronze. The planking was selected based upon the pocketbook of the owner and how much tonnage they wanted to save. As these were high end merchant ships, dense resistant woods were selected to maximize cargo volume and minimize maintainence downtime. A China voyage lasted a whole year because of the wind patterns. Missing the weather window meant a year without profit, so most ships were never docked in thier short hard lives. It should also be pointed out that we are talking about wrought iron, not steel. Wrought iron is much less succeptable to corrosion in seawater than modern crucible steel.

[Tad]

I said dissimilar materials not dissimilar metals. With changes in temperature the metal frames will always move more than the planking. This will stress the bolts continuously.

How is mining and smelting irreplaceable metal more environmentally friendly than cutting down renewable trees?

I designed a 125' ketch (HETAIROS) http://www.superyachttimes.com/yachts/details/1747/

She was launched in 1993 and built by Abeking & Rasmussen. Her hull skin is four layers of cold-molded planking bonded with epoxy. She has laminated stem and stern posts but midships is an all bronze weldment comprising the main mast step and floors, centerboard case, engine beds, and mizzen mast step. We (the designer's, BKYD) were against this but it was pushed by the builders. It caused nothing but trouble in the first few years due to corrosion and leaking welds. A laminated wooden backbone with fiberglass centerboard case would have caused no such problems, which has been proved in other similar vessels.