Engineering whitepaper draft published
James
A rough draft of our first seasteading engineering paper has been
released. Details here, feedback welcome! Eelco, the author, is on
this list, so your comments will go straight to the source :-)
James
--
James Hogan, Director of Operations
The Seasteading Institute
www.seasteading.org
Michel Santos
I recently finished reading through v.0.1 of the report. The overview
of the assumptions, in Section 1, prior to discussing the candidate
designs, in the future Section 2, was done technically well, and was
written well, too; the latter was a happy surprise. And reviewing all
of the assumptions and methodology is valuable for any report,
especially one that is as broad as this report.
I also appreciated when certain assumptions or conclusions were made in
light of insufficient data because: (a) this really assists the reader
in better understanding which conclusions could merit additional review;
and (b) permits the analysis to proceed anyway. In conclusion, I
thought that the report was very good.
I also have a bunch of small edits and typos that are probably
uninteresting for this list. Should I send these directly to the "eng@"
address? Also, do you have an editable version of the document (e.g.
OpenOffice Writer or MS Word) with which I could make changes through
tracking?
Michel
Lasse Birk Olesen
I haven't read the whole paper yet but I have a comment for the
section on the Baltic Sea.
While you consider the Gulf of Finland, which has the drawback of
being cold, have you considered the south-western Baltic? East of
Denmark, south of Sweden.
While I don't know the 100 year maximum, Finnish Helcom (
http://www.helcom.fi/environment2/ifs/en_GB/cover/ ) provides maximums
for 2008, 2007 and 2006 for the two locations Darss Sill and Cape
Arkona (as marked on this map: http://www.tinyurl.dk/16363):
2008
Cape Arkona: 4.1 m
Darss Sill: 3.7 m
2007
Cape Arkona: 4.9 m
Darss Sill: 3.7 m
2006
Cape Arkona: < 4 m
Darss Sill: < 4 m
I also suspect that if you move further north than the position of
these two buoys, you will have smaller maximums because of a smaller
fetch. Unfortunately, I don't know of any wave data from a location
outside the territorial waters to confirm this. On the Google Maps
layer I have indicated with a green icon the most northern position in
this region possible without entering territorial waters.
Another interesting location is further southwest, between Germany and
Denmark. Measuring for 12 nm from the coast, there should be a small
area outside territorial waters. I have marked the location with a
green icon here: http://www.tinyurl.dk/16366
The blue icon a bit to the east indicates a buoy for which I have wave
data in the years 1931-1960 in an old book. In these 30 years, the
maximum wave height recorded was 5.0 meter.
Compared to the 1 year max of the ClubStead location of 7 meter, don't
these maximums seem like a significant difference?
Lasse
On Mar 4, 12:23 am, James <jho...@seasteading.org> wrote:
> Hey all,
>
> A rough draft of our first seasteading engineering paper has been
> released. Details here, feedback welcome! Eelco, the author, is on
> this list, so your comments will go straight to the source :-)
>
> http://www.seasteading.org/blogs/main/2010/03/01/research-update-tsi-...
Lasse Birk Olesen
territorial waters 3" on http://www.tinyurl.dk/16366
The two nearby buoys recorded a maximum wave height of 4.2 meter
between 1931 and 1960. The location may be less jurisdictionally
attractive, because it is only close to one country, but the waves do
seem nice.
On Apr 11, 5:53 pm, Lasse Birk Olesen <fimpf...@gmail.com> wrote:
> Hi
>
> I haven't read the whole paper yet but I have a comment for the
> section on the Baltic Sea.
>
> While you consider the Gulf of Finland, which has the drawback of
> being cold, have you considered the south-western Baltic? East of
> Denmark, south of Sweden.
>
> While I don't know the 100 year maximum, Finnish Helcom (http://www.helcom.fi/environment2/ifs/en_GB/cover/) provides maximums
Patri Friedman
Hi
I haven't read the whole paper yet but I have a comment for the
section on the Baltic Sea.
While you consider the Gulf of Finland, which has the drawback of
being cold, have you considered the south-western Baltic? East of
Denmark, south of Sweden.
While I don't know the 100 year maximum, Finnish Helcom (
http://www.helcom.fi/environment2/ifs/en_GB/cover/ ) provides maximums
for 2008, 2007 and 2006 for the two locations Darss Sill and Cape
Arkona (as marked on this map: http://www.tinyurl.dk/16363):
2008
Cape Arkona: 4.1 m
Darss Sill: 3.7 m
2007
Cape Arkona: 4.9 m
Darss Sill: 3.7 m
2006
Cape Arkona: < 4 m
Darss Sill: < 4 m
I also suspect that if you move further north than the position of
these two buoys, you will have smaller maximums because of a smaller
fetch. Unfortunately, I don't know of any wave data from a location
outside the territorial waters to confirm this.
Whenever we manage to fund the location research, we will be able to get this data from satellite wave data, so suggesting potential locations even if you don't have wave data for them is useful.
Lasse, I will give you access to the location document where we are tracking ideas and preliminary data for now until we have the project funded & staffed.
On the Google Maps
layer I have indicated with a green icon the most northern position in
this region possible without entering territorial waters.
Another interesting location is further southwest, between Germany and
Denmark. Measuring for 12 nm from the coast, there should be a small
area outside territorial waters. I have marked the location with a
green icon here: http://www.tinyurl.dk/16366
The blue icon a bit to the east indicates a buoy for which I have wave
data in the years 1931-1960 in an old book. In these 30 years, the
maximum wave height recorded was 5.0 meter.
Compared to the 1 year max of the ClubStead location of 7 meter, don't
these maximums seem like a significant difference?
Lasse
> http://www.seasteading.org/blogs/main/2010/03/01/research-update-tsi-...
On Mar 4, 12:23 am, James <jho...@seasteading.org> wrote:
> Hey all,
>
> A rough draft of our first seasteading engineering paper has been
> released. Details here, feedback welcome! Eelco, the author, is on
> this list, so your comments will go straight to the source :-)
>
>> The Seasteading Institutewww.seasteading.org
> James
>
> --
> James Hogan, Director of Operations
--
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--
Patri Friedman, Executive Director
The Seasteading Institute
www.seasteading.org
crmo...@verizon.net
thought out and well
written.
I have a few comments regarding the selection of materials and
maintenance over a long period of time.
I have always been a fan of the use of ferrocement in ocean
structures. As stated it is low cost, and low maintenance, although
very labor intensive in construction. But ferrocement is not
maintenance free. Concrete is very strong in compression, but very
weak in tension, hence the need for a steel core to take the tension
loads. However in a mobile environment, such as a seastead, the ocean
structure can be expected to undergo frequent bending and torsion
loading from wave and current action, as well as from purposeful
movement of the seastead. These loads over a period of time can lead
to small microscopic surface cracks in the cement from surface tension
loads. The cracks can slowly grow over time to a size that will allow
seawater to seep into the ferrocement core and allow galvanic
corrosion to occur in the embedded steel structures. If allowed to
proceed unchecked, then failure of the ferrocement structure will
eventually occur. Also cement is not completely impervious to
seawater. Over a long period of time seawater will slowly soak into
the cement and aggregate structure of the concrete. The salts will
then weaken the chemical bonds of the Portland cement, causing
cracking and flaking of the cement. These are the reasons that
ferrocement boats are still painted, like other boats. The paint coat
protects the cement from seawater intrusion as well as filling and
binding the microscopic surface cracks that occur from bending and
torsion loadings. There are now epoxy coatings that can be applied
underwater, so maintaining a barrier coat on the seastead, even after
construction and at sea, should be considered a maintenance
requirement for long life of the seastead.
The problem with ferrocement structures for very long term is the
difficulty of repair. We cannot make the assumption that damage to
the seastead of some sort will never occur. As mentioned above an
undetected seawater intrusion into the ferrocement core can cause
damage. Collision with another seaborne object can also cause
damage. Such a collision can occur from a ship which is improperly
piloted, or even a cargo container lost overboard by a carrier at some
point and carried by a wave into the seastead structure. A collision
with floating cargo containers happens on a surprisingly frequent
basis and due to their size and weight can cause considerable
damage.
Small surface damages and cracks in the concrete can be easily
repaired at sea by either applying a fresh overcoat of cement if above
the water line. Below the water line is a bit trickier. There are
cement mixtures which can be applied underwater, but they are hard to
work with. There are also other epoxy based fillers which could also
be used. The problem with ferrocement repair comes when damage is
more than superficial and on even a localized basis impacts the
structural integrity of the seastead. Structural repair of
ferrocement structures is a very difficult process since the steel
structural members are embedded in the concrete, and the concrete is
designed to be a single homogenous structural. This makes removal and
replacement of a damaged section of ferrocement difficult, especially
underwater. And even if successful, the shell is no longer a
homogenous structure, so without proper sealing seawater can seep into
the repair cuts.
While steel cannot be classified as low maintenance, it is also no
longer a high maintenance material. Modern epoxy coatings easily
prevent most corrosion, and when combined with proper anti-galvanic
protection using sacrificial zinc anodes, per standard commercial
practice, the lifetime of steel structures can now be made nearly
indefinite. The real advantage that steel has over ferrocement is
ease of repair. Damaged or corroded sections of steel can be easily
cut out and replacement sections welded into place for a structurally
strong and fully watertight repair. Even underwater repairs of this
nature are regular commercial procedures. And with the new
generations of underwater epoxies that are available, underwater
seastead steel structures can be routinely ground bare under water
section by section and repainted with a fresh epoxy barrier coating as
part of regular routine seastead maintenance. And regular replacement
of sacrificial zinc anodes would also be part of this regular
maintenance schedule, even at sea. These days commercial steel ships
are dry-docked for maintenance more out of convenience than out of
technical necessity.
In choosing a material for building seasteads I think we have to
consider long term maintenance and repair as a factor. While
ferrocement may still be the best choice, I think steel should not be
completely discounted just yet.
Great job on this first paper!
Eelco Hoogendoorn
Hi Lasse,
Sorry for the late reply; the email adress with which I was subscribed
to this Group was discontinued, so I dropped out of the loop without
noticing.
Let me start out by saying that whatever oceanographic research I did
is far from comprehensive, and additions to it are very much welcome.
Indeed I looked mostly at the gulf of Finland, because it has a good
combination of low maximum waves, shallow waters, and non-territorial
waters with large cities nearby, and one nation whom we think will be
particularly friendly to seasteads (estland). But the ice seems like a
dealbreaker.
As for the southern Baltic, I havnt looked at it in much detail. One
thing I noted is that waves in the open bodies of water can in general
become quite big. Usually they are not too bad, but the worst case
scenarios recorded over the past centuries are worse than clubstead
conditions. However, these extrema are due to storms coming from the
atlantic, so headed east. They probably don’t generate large waves in
the locations you marked. But still, it would be good to try and get a
handle on information concerning worst case scenarios, since ive found
they can be surprising.
A 4m maximum would be great. The difference between 4 and 7m is huge,
because not only are these smaller waves smaller, they also tend to be
shorter, which results in a much more manageable situation in terms of
comfort as well as structural integrity. Wave drift forces are
quadratic in waveheight, and hogging/sagging is cubic in wavelength,
so indeed it matters a lot.
Water depth is also a useful piece of information. Dynamic positioning
adds quite a bit of costs, both capital and for many concepts
prohibitive operating costs, so if water depths allow effective
mooring, thatd be great. This is a rough estimate, but id say 50m is
the limit for effective mooring of vessels in close proximity. Beyond
that, vessels would have too big a watch circle to allow easy movement
between them. Many places in the Baltic fail that criteria, but these
areas seem like they might be shallow.
One issue would be that both Denmark and Sweden are rather regulation-
happy nations, but then again if Christiania can get away with stuff
then why couldn’t we? (‘no enemies to the left, no friends to the
right’, as moldbug would say, but whatever).
Eelco
On 11 apr, 17:53, Lasse Birk Olesen <fimpf...@gmail.com> wrote:
> Hi
>
> I haven't read the whole paper yet but I have a comment for the
> section on the Baltic Sea.
>
> While you consider the Gulf of Finland, which has the drawback of
> being cold, have you considered the south-western Baltic? East of
> Denmark, south of Sweden.
>
Eelco Hoogendoorn
Hi Carl,
Thanks for the feedback, it is much appreciated.
Marine concrete is starting to become more and more mainstream, as the
material has been building a track record over the past decennia.
There are a bunch of reference in the paper where I got my (possibly
wrong) information from; here are some replies based on that
information:
Cracking: unlike normal reinforced concrete, post-tensioned concrete
does not suffer from cracking, as a strictly compressive stress will
always be maintained in the concrete (assuming things don’t completely
break). Longer boat/barge like structures that are subjected to large
hogging/sagging forces should most certainly be built using post-
tensioned concrete rather than ordinary reinforced concrete; indeed,
that would be a questionable idea.
Corrosion: indeed, this is something to take heed of. Instead of an
external coating I believe the solution most commonly applied nowadays
is to add a resin to the cement mix that fills the cement pores.
Besides, marine concrete construction standards demand active electric
protection of all embedded steel components. I do not believe there
are any known cases of marine concrete built using modern standards
that have suffered from any of these issues, but I know that it is a
liability; one mistake here and your entire structure is scrap,
basically.
Overall, regarding maintenance in concrete: there are several floating
concrete projects that have served for decades without any maintenance
on the main structure. With modern techniques, hull maintenance should
be avoidable with concrete.
Wrt damage: indeed, collisions between vessels is really something
that has to be avoided. I don’t think steel-to-concrete collisions
would be a problem, for the concrete vessel at least, but steel-to-
steel or concrete-to-concrete would be disasterous. Considering that
we want to operate these seasteads in relative proximity, this is
certainly something to think about. Given that we don’t care a whole
lot about hydrodynamicity, perhaps adding an extension bumper zone
around all vessels would be wise.
I am very interested in your comments regarding steel maintenance, as
I know little about it, and couldn’t find much information on it, and
essentially no information regarding costs. I know wet-maintenance is
technically possible, but in practice I read a lot of reports of oil
platforms being scrapped when they have reached their designed
corrosion- lifetime, rather than being repainted / reused. Therefore,
I got the impression it must be quite expensive, and drydocking is not
an option for seastead concepts that fall outside the standard ship
paradigm.
I was also curious how much drydocking a steel ship really needs. In
case drag reduction is a large motivation for the high frequency of
drydocking, then we could get away with far less as seasteaders, id
say. Do you have any sources w.r.t. that issue?
Thanks again,
Eelco