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Richard Braithwaite
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Everything posted by Richard Braithwaite
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So Im fitting the lower seatings for the tabernacle "remotely" through the deck beams onto the floors. They are both in place with the taberbnacle to ensure proper alignment. The piece of wood lying longitudinally on top of the floor and in between the seatings is intended to help align them fore and aft (the center line drawn on this timber lines up with a centerline mark on one of the floors). The starboard seating has been glued in place in the photo. Hopefully the port one will be easier with the starboard one in place to act as a guide. Not the way I would have chosen to do this if I had planned it all properly. Lowering the starboard seat through the deck beams and into place, after I had applied glue relied on the steadiness of my hands rather more than I usually like to!
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Havent posted for some time... Have been ploughing on with the top level seats, which are now finished. Usually enjoy the therapeutic nature of repetetive tasks, but must admit that 170 seats... Anyway, now putting in tabernacles for masts. Would have been easier to install before planking the gangway, but I am where I am... I took a bit of time to work out how these are constructed from John's drawing (MSR 12 © Estate of John F. Coates, reproduced with permission) and some, not very clear, photographs of Olympias. The main components of the forward tabernacle are shown below: And the hole I have had to cut in the gangway to install it: I was originally thinking I would remove the whole deck assembly (un boltable) to install the lower seating for the tablernacle, but Im now thinking that it will be more accurately alighned if I do it with the deck bolted in place. Just a bit fiddly fitting the timbers through all those beams and seats...
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Simpler at the fore end where the forward most seats on the upper level sit on the removable section. Luckily the bolts that I put in this area cleared them (well almost...). At one point I wasn't planning to fit seats so these bolts were placed without thinking about them...
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Still plodding away with the seats. The series of photos below shows my solution for a removable seat to allow for the removal of the gangway section of the model.
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Problem with ships having a port and starboard sides is that I need to make two jigs... One benefit is that I can now work on both sides at once, which is speeding up production a bit (from my usual snails pace...)
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First check on the ergonomics with my trusty triad of marines: Still to fit their footrests...
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For some reason its taken me a long time to work out how to install and jig the upper seats... The jig ive ended up with at this stage is shown below together with a seat assembly (seat+ foot stretcher + support pillar). The jig consists of two parts. The main part is intended to hold the seat level athwartships and at the 9 degrees rake to the centerline with a removable section that can be unbolted so that the jig can be removed after fixing the seat in place. Here is the jig in place in the model: And, finally with the seat assembly in place: The seat is assembly is fixed to the seat forward of it by its foot stretcher (held in place by the steel clip while the glue dries) and to the beam underneath by its support pillar. The intention is that all the seats form part of the removable part of the model and so this seat assembly can not be glued to the sheer capping... The lathe cutting tool is functioning as a weight to hold the seat down in the jig while the glue dries...
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My triad of oarsmen completed. From right to left: Thalmian, Zygian and Thranite oarsmen holding their appropriate oars. The oars shown are based on the original oars for Olympias which were used for most of the sea trials. The blades are designed with a different shape to account for the differing vertical angle of immersion for the three different levels. A lighter version of the oar was later trialed (where all three levels used the same design).
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The middle tier of oar seats are much more straightforward to install than the lower tier as they are not raked relative to the vessels centerline. This means I can align them easily with a straight edge. Here are 3 going in in one gluing operation:
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Yes, I am finding that 1:24 is about as small a scale as I can manage. The main reason for the full scale reconstruction was to demonstrate that it was possible to arrange 170 oarsmen, each with their own oar, in a ship 37m long... So I wanted to be able to show that this could work on the model... The clearances between the oar blades, and hence the geometric tolerances for building many critical areas of the ship, are necessarily very tight to achieve this even at full scale let alone on a model...
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Starting the installation of the second tier (Zygian) of oarsmen seats. Again, my Manikin is helping to confirm that the seat is in the right place for the downward angle and sweep of the oar and that there is no interference with the lower (Thalmian) oarsmen. The oar blades ae resting on a block of wood placed to give the right downward angle for complete immersion of the blade in the middle of the power stroke (at the design displacement). One the inboard distance of the seat is established I constructed the jig for installing the oarsmen stretchers at the same distance from the tholes which can be seen in the next bay forward of the manikins position. Part of this jig holds the new stretcher in place, perpendicular to the deck beams and the other part is a simple "ruler" that fits over the thole pin marked for the correct distance inboard. I will need to remark this for the shorter oars at the ends of the vessel...
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Yes that is still the plan. However, at the moment I am concentrating on completing the model with as little concession to that as possible. I want the mechanism to be fully removable so that the model can stand with or without. That is on of the main reasons I have made it fully capable of dismantling.
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Disassembled the model today for the first time in a very long time, to check that I haven't done anything to stop me being able to get at the bolts and that the main hull outfit assembly (which includes deck beams, support pillars, inner hull longitudinals, gangway, and now thalmian seating...) is still removable. It takes me just over half an hour to assemble (there are 82 bolts to secure in total...) and I was quite pleased with how easily the main hull outfit assemble fitted into place with no flexing at all and all the bolts perfectly lined up with their holes. I'll have to do it again to fit the mast steps (I know, I could have done that before I put the deck in...) and I'm hoping it will make it easier to get at everything when I finally come to coating the wood with something.
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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)
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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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