Richard Braithwaite
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Confusingly, this lines plan is drawn to two different scales. The sections are at 1:10. However the waterlines and buttocks are both drawn to 1:10 in the vertical (in the case of the buttocks) and athwartships (in the case of the waterlines) directions BUT at 1:50 in longitudinal direction. I guess John Coates did this so that he could fit the drawing (with a decent size for the sections at 1:10...) on a shorter piece of paper. The drawing would be over 3.5 meters long at 1:10... Some of his other drawings give the locations of the station placement in relation to the structure of the ship (eg Plans 8,10 and 11)- 536 replies
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I designed a simple prototype rowing machine that produces an elliptical rowing stroke. The machinery fits underneath the gangway on a 1:24 model of Olympias (in between the vertical stanchions). there is a link to a video of the machine installed in a 1:24the section of the ship on my Trireme Olympias thread on this site. Adding a software controlled stroke, as proposed here, would be really interesting as it would give you complete control over the stroke geometry.
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A Thalmian oarsman's view (looking aft) of the 21 seats Ive installed so far on the starboard side of the ship (149 to go...)
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Yes, I've tried some modelling of humans using a similar program that is freely downloadable (DAZ3D). I guess you could save in a file format readable by a 3D printer?
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Great to see someone producing a model based on another of John Coates reconstructions! Building frames first and then planking them seems to work fine. I produced my trireme hull the other way round... Planking first onto a jig of temporary frames at the hull stations. Here is the hull planked up to the level of the floors: And then fitting the frames from the inside Working up level by level until all the planks and frames were in place and then removing from the frame jig:
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Upping the tempo on the Thalmian beams, stretchers and seats. Here a Jig for installing the stretchers between the thalmian beams: The little wire clip is useful in holding the stretcher at the right height while the epoxy cures. Unfortunately this jig will only work on the starboard side. I think Ill have to completely rebuild for the port side. Would have preferred to come up with something a bit more ambidextrous (oh well...) For the seats themselves, I'm building them in strip fashion so they can be cut off one by one and finished before installation...
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Just looked through your Dromon Thread. Great reconstruction. I see you carved individual oarsmen! I don't think I have the endurance to make 170 for my model! I am thinking of three of my manikins to demonstrate a single triad or oars. I suppose one could make a CAD model and 3D print them? Has anyone tried that?
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I do take your point. Not the most efficient stroke... Apparently the diagram was taken from a video record so should be reasonably accurate representation of what this particular oarsman achieved at this time. However, "the video record did reveal the variable quality of the bladework". Looking at the report which shows similar traces of what some of the other rowers were doing it appears that the diagram is one of the better ones (by a long way!). Bear in mind that this was 170 people rowing together for the first time in a vessel that they were unfamiliar with often from constrained seating positions with very little visibility. So technique was not optimal at all... The report does comment on the large difference observed between the effective stroke length and the total length of the stroke saying that "the reasons why they mostly took their blades out of the water long before they had finished moving them sternwards require investigation.." One reason suggested was that "the high moment of inertia of the oars which meant that they could not be manipulated quickly: if they were slowed prematurely because of this they would have to be taken out of the water early to avoid backwatering" Even in a modern high performance racing 8 the blade is moving before it enters the water in order that it is at least travelling at the same speed as the water that is passing the boat (otherwise there will be a degree of backwatering at the catch and a negative force on the boat). For similar reasons the oar will be moving at some speed at the finish. The distance taken to accelerate the oar to this speed before the catch ("catch slip") or decelerate it after the finish (the "release slip") will largely be a function of the inertia of the oar (as well and the strength/skill of the oarsman) as suggested in the report, and the oars fitted to Olympias were much heavier and had higher inertia than those of a modern racing shell. They did make some effort to address this with lighter oars in later trials on Olympias. This did enable higher speeds to be achieved, but I haven't seen any traces of oar path to see if the catch and release slip had been significantly reduced. There are some good diagrams at the following link which shows this effect and oar traces for modern racing shells. http://biorow.com/index.php?route=information/news/news&news_id=30 even these guys seem to waste some energy moving the oar up and down in the water during the power stroke
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This document contains a bit more detail on the trails and calculations described above and application to a working model of Olympias using the elliptical machine shown in the video on a previous page of this thread. Rowing Machine Calculation.pdf One interesting finding is that with The top tier only (i.e. 62 oarsmen) the average speed is predicted at 6.53 knots, tis increases to 7.72 knots with all 170 oarsmen. So a significant increase in speed, but not as much as one might expect for all these additional oars. The main benefit would have been acceleration and maneuverability (very important in combat) which, I guess is why it was so important to pack as many oarsmen as they could into the boat.
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You can get strain guages for full size oars and I have thought about making a full size mockup of a single rowing position to measure forces to validate my computer simulation. However, it is probably impractical to measure the strain in a model oar shaft as the loads on the oars are really tiny. For example the maximum thrust I measured in a zero speed trial of my Mk 1 galley (750mm long, 500 grams in weight, 12 oars, 150mm outboard length at 45 strokes per minute) was 0.0123N (measured using a fine thread attached to a post on the stern running to a pully with a hanging weight). So that's only 0.001N/oar! The average speed achieved by this galley at this stroke rate was 0.09 m/s. If we say that this galley was at a scale of 1:24 then this speed equates to around 2.16m/s or around 4 knots (if we scale speed by length). This isn't particularly fast, but then a constant speed circular oar motion is not particularly efficient! The motor in my Mk 1 galley was way over the power required, but that's not really a problem (I wasn't interested in efficiency here) but it does ensure that any friction in the mechanism (much more significant than the propulsive forces) is easily overcome. (Now if you fitted your rowing machine to a full size galley, or a really large scale model, the loads would be larger and easier to measure!!) It might be better to measure the boat speed somehow and program your oar motion accordingly rather than try to measure these tiny forces? Alternatively you could increase the speed of a small scale model, but that would require ridiculously high stroke rates! Ive Just found a simple spreadsheet model that I used to predict the oar forces in the first trial (zero speed 45 spm) I referred to above: RowingMk2Trial1.xls And here is the spreadsheet set up for the second trial (steady state speed at 45 spm) RowingMk2Trial2.xls Since this rowing machine moves the oars at a constant (circular) speed no matter what the boat is doing its relatively easy to simulate with a spreadsheet. Still I was quite pleased at how close my spreadsheet came to the measured performance of my little model. Adding a human being into the simulation does, however, makes it a lot more complicated!!
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I did some trials with an early prototype rowing machine. If you go for a "realistic" stoke rate of say 50 spm the speed of the boat is very low (it can never be faster than the oars move through the water!) and the force required (and hence torque on your servos) is trivially small. A more significant factor determining how strong your servos need to be will be the friction in your rowing machine mechanism. A couple of pictures of my Mk 1 Galley and its rowing machinery (simple, circular path, constant speed...). I found, that as the scale speed is so low you need a really calm day if you do the trials outside! My calculations suggest that this will still be the case with a 1:24 scale model of Olympias even with its 170 oars...
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A couple of figures from the Olympias sea trials that may be of interest (Ref The Trireme Trials 1988 Report on the Anglo-Helenic Sea Trials of Olympias, J F Coates, S K Platis, J.T. Shaw, Oxbow Books) The first shows a trace of the oar handle and blade of one of the Thranite oarsmen (top tier, who tended to provide most power as they had the least constrained positions): The next plot is of speed from a standing start (Thranites only). Acceleration and maneuverability are particularly important for this type of vessel so that they could break from a slow moving formation faster than the opposing vessels and so achieve a tactical advantage and get into a position to ram. You can see that the first few strokes are at a lower rate, accelerating as the boat speed increases and the pressure on the oar blades reduces for a given stroke rate (at higher speeds the inertia of the oars will become more dominant in determining stroke rate). My current simulation code allows you to set a maximum load that the oarsman can apply to the oar handle and then works out the dynamics of the oar handle (and the resulting forces on the boat) accounting for water pressure on the blade and oar inertia. When I use the data for Olympias with Thranite oarsmen only I get the following match for the trials data: For a working model (it you wanted to make starts more convincing), you already have the ability to vary the rate of the power and recovery parts of the stroke. You might be able to add a sensor for boat speed (gps or spinner?) and adjust stroke rate accordingly? I just noticed that this thranite oarsman achieved a 700mm stoke (the design hoped for 800mm ...), which is similar to the stroke length that my manikin figure is managing on my model (on the more constrained, lower level). I've just posted a GIF animation of him in action on my blog!
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Lovely model great workmanship. I have 170 oars to make for my current model and the jig you used for your oars looks interesting...
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I like your method of taking the shape of the floors. I built my trireme model is a similar way (planks over a jig and then shaping frames to fit...) It took ages, as every frame was different... And after
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I suppose its a good thing that his head is made of wood... Its taking me long enough to build this one so I don't think Ill be making another one soon. I have been developing a computer simulation, however, which I'm hoping might be useful in supporting some design work to assess the extent to which performance could be improved by optimizing the layout.
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A little animated gif of my the manikin at this thalmian position. His rowing technique leaves something to be desired (!) but he does illustrate one of the difficulties of the design. The limited space between the deck beams meant that these rowers tended to his their heads at each end of the stroke. It was a particular problem at the finish and could be dangerous if anyone caught a crab… They mitigated it on trials by putting the smallest rowers in these positions (I based my Manikin on a 50% 600BC Athenian build…) and fitting a restraining rope to the oar so that it wouldn’t break their necks if they caught a crab. Not ideal, and the power delivered from this level suffered accordingly. One of the issues to address in any Mk II design… Just noticed that his foot rest had dropped and disengaged from the locating dowel. Should have lashed it tighter... oops!... I think my manikin achieves about 720mm of the full 800mm design stroke. I have modified his joint already to make him a little more flexible but he still had problems pulling the oar right into his torso at the finish of the stroke (as you can see from the GIF above). However, I don't think they often achieved the full 800 mm stroke on trials for the reasons given above...
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First Thalmian (lowest level of three) Rowing position in place (minus the leather foot and heel straps. The small dowel in the stretcher is used to locate the footrest and allow some adjustment for the rowers leg length. These foot rests are pretty much hidden underneath the seats once they are all installed. (Drawing shown is an extract from John Coats Plan No 9 titled "Trieres Foot Stretcher" © Estate of John F. Coates, reproduced with permission)
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Removed the canopy sections so I can start to install the oar seats etc for the lower level (Thalmian). Probably should have done this earlier in the build, but the ability to dismantle my model helps me get away with it! First photo shows the longitudinal stringer that supports the inner end of the Thalmian beams installation using a jig to ensue the correct vertical location. The next photo shows a couple of Thalmian beams in place with a plywood jig to fix the 3 degree rake. The deck beams, walkway, inner stringer etc. all comes away as a boltable assembly, which means I can only fix the inner ends of these beams. The outer end is left resting on the Thalmian stringer. I'm hoping that once I have installed the seats and stringers (which connect the beams longitudinally) this cantilevered arrangement should be stable enough...(Extract of John Coates Midship Section Drawing ‘© Estate of John F. Coates, reproduced with permission.)
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Looks a little "robotic" though. Hopefully can use them for illustrating how the three tiers work together through the rowing stroke. I don't think I will be making 170 of them though...
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An Athenian Marine... I've been looking for a scale wooden artists manikin to demonstrate ergonomics of rowing equipment geometry etc. but they are all on much too large a scale for my model. So I decided to have a go myself at a 1:24 version. For the dimensions I found a good source of ergonomic data for US Marines (https://apps.dtic.mil/sti/pdfs/ADA581918.pdf). I took the data for the 50th percentile marine and scaled it according to the mean height of a classical Greek male (approx. 5 ' 7" as identified from Archaeological studies of skeletal remains ref S. C. Bisel, J. L. Angel, "Health and Nutrition in Mycenean Greece: A Study in Human Skeletal Remains," in N. Wilkie, W.D.E. Coulson (eds.) Contributions to Aegean Archaeology: Studies in honor of William A. MacDonald (Minneapolis 1985)). Given both US Marines and Athenian oarsmen are likely to be of a similar muscular build, I thought this approach would give a reasonable approximation. I know that trials on the full size of Olympias had some difficulties fitting 20th century oarsmen in some of the rowing positions... Anyway the resulting model is shown below: I've used two sort of joints to give the required mobility: 1. ball ended pins to simulate the ball and socket joints of the shoulder and hip (and the rotational joints of the neck and heels) 2. simple one degree of freedom pin joints for the knees and elbows. This works for an oarsman at around midstroke as shown below: And finally standing on the helmsman's platform of the model to give an indication of scale: I'm planning to make 3 of these manikins so I can check the arrangement of the rowing equipment (seats, stretchers etc,) on the model for each triad of oarsmen.
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Insallation of the ladders on the model. The left hand image shows the aft end of the gangway and part of the helmsman's platform with the aft canopy sections removed. the brass lined holes in the deck are to locate the pins on the base of the ladders. The brass lined hole for locating the aftermost stanchion of the aftermost canopy sections can also be seen in the deck beams just outboard of the gangway as can the bolted lodging knees that are part of the system that enables the unbolting and removal of the entire deck assembly. The right hand image shows the ladders (and the aft canopy sections) installed. Finally a view of the ladders, quarterdeck (with Trierarch's chair!) and helmsman's platform looking aft from canopy level. The slots in the quarterdeck (with the turned rollers) are form the steering oars to pass through which are fitted with athwartships tillers controlled by the helmsman standing on the platform in front of the Trierarch.
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Three ladders completed. The brass rod sticking out of the base of the ladders is to enable location on the model. At the moment I'm leaving the top unsecured... Not very seamanlike, I know, but hopefully my model shouldn't be experiencing any violent seas!
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An overall view of my lovely Unimat configured as a milling machine. I bought it in 1985 and its been well used since. The motor packed in some time ago and has been replaced with a rather less elegant modern version unfortunately...
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