10th-11th century Byzantine dromon by Louie da fly - FINISHED - 1:50

[Louie da fly]

Interesting times. I've had to discard two of the lower bank oars. One I'd made broke in the middle while I was making it and I glued it back together hoping it would be ok. I coloured the inner end blue (it'll be invisible below decks) to remind me, then forgot what the blue was for (having a "senior moment"). But the glueing wasn't successful, so I have to replace it. 

Another was the wrong shape at the inboard end and also has to be replaced. So here is step one - sawn roughly to shape

As I make progress on this I'll post pictures.

 

 

When I made the lower bank oars I wasn't sure how I was going to attach them, so I left the inboard end rough. Now I'm going through them trimming the inner end of each to fit against the oar frame - in line with the taper of the oar loom, so they'll all be at the same angle when they're attached to the frame. The upper one is before trimming, the lower one is after. 

 

I used a ruler as a straight edge to get the correct line.

Half are done. Another 25 to go.

 

And I'm now also working on the middle mast. First cutting it roughly to shape with a coping saw:

 

Then trimming it with a Stanley knife.

 

And thinning it down.

   

Roughly trimmed, ready to get exactly to shape. Then I'll take off the corners, and gradually give it a rounded section.

 

When finished, the mast should look like these (from the Homilies of Gregory the Theologian, Byzantine c. 880 AD):

 

Steven

[Louie da fly]

Smoothed off the mast and getting ready for final shaping.

  

 

Apparently there's supposed to be a sheave near the masthead for the halyard. I have one (modern) source that puts it in the mast itself, but the upper vessel in the Homilies picture above seems to show it centred in the funny curved bit (there's a line coming from there which I'm pretty sure must be the halyard).

 

On the other hand, a picture on the Pala d'Oro in Venice seems to show the halyard going to a point on the mast below the yard. Or is it a pair of shrouds? Mediterranean lateeners generally seem to have the top of the shrouds below the sheave for the halyard. And should I rely on this one as much? Although the style is Byzantine, the text is in Latin, so perhaps it's a Western example.

I have to say, having the sheave in the curved bit makes sense to me. If the purpose of the curve is to bring the halyard forward of the mast, then logically the sheave should go in the end of the curve. I'll think about it a bit and decide where the sheave should go. (Sigh)

 

Steven

Edited June 18, 2018 by Louie da fly

[BANYAN]

I would not know for sure Steven, but your logic is sound for placement in the bulge at the top.

 

cheers

 

Pat

[woodrat]

the halyard, at the end of the day, should pull the yard away from the mast so it runs smoothly as it raises and lowers. I believe there should be a line which pulls the yard against the mast once it is in the correct position and is released for tacking or changes on yard position. I show the arrangement on my carrack. Athough the dromon does not have parrels, the principle is the same. Keep up the good work.

Dick

Edited June 19, 2018 by woodrat

[Louie da fly]

Thanks everyone for all the likes.

 

Thanks also to Banyan and Woodrat.

 

Pat, the only concern I have is that the curved bit may not be strong enough to take the weight of the yard and sail. On the other hand, by judicious choice of trees with branches which approximate the curve (or even training branches to do so) this issue might be overcome.

 

Dick, I've already been mulling over what form the attachment of the yard to the mast will have to be. Haven't got a final answer, but I think a rope loop that can be loosened should fit the bill. Many contemporary and near-contemporary representations, and modern Mediterranean lateeners, have something of the sort.

 

Steven  

[Mark Pearse]

Hi Steven

 

an interesting & difficult problem. Ideally you would put the shrouds & halyards converging at the same point, we can do that now because of our metalwork. If you take away that technology then bringing all these lines together to one point is much more difficult. Unpicking the reasoning behind that I think is the key.

 

I think that you are correct to assume the hockey stick end is the halyard: the shroud loads will be balanced by the mast & should connect directly to the mast, or in line with it. I feel the mast cap piece has to be a second piece of timber, & probably some sort of tough, strong timber. A good choice of timber for a mast wouldn't be a good choice for the cap timber.  The sketch below might work, the grain is at 90º to the mast & it held in place by the shrouds load, & mast housed into the cap. The closer boat in the Homilies picture has a line that might indicate a separate piece of timber, & it looks to show the shrouds going into a hole above the top of the mast. The shrouds could be fixed to the mast by wrapping around the top or back of the cap a couple of times & then back down the other side, so the shrouds are continuous.

 

It's hard to say how the halyards are connected, but maybe it was just a loop of metal & the halyard ran through it.  Alternatively, could it have had a single sheave? The sheave probably in some really tough timber & lubricated with fat.

 

 

 

[cog]

Mark did you take into account the forces on the top of the mast. Those would be tremendous, and I wonder if the mast top would be able to withstand those. I would expect the top to split without the aid of a metal band - which wouldn't be available at that time, at least I presume it didn't ...

[Louie da fly]

Mark, I think that if there was a separate piece making the end of the hockey stick (why didn't I think of that name?) the downward force of the halyard would cause a powerful moment (turning force) to make the cap piece pivot around its attachment to the mast. Also, all the contemporary representations of the "cap" show it as "U" shaped rather than at right angles. I think the line you mention is probably where the tops of the shrouds wrap around the mast.

 

Carl, you raise a good point and I don't know a good answer except what I mentioned above. But the Byzantines certainly had the technology to make iron reinforcing bands.

 

Anyway, I've bitten the bullet and put the sheave in the blob at the end of the hockey stick. I can't be certain it's correct, but it seems the most logical configuration (always assuming the structure is strong enough).

 

        

 

Steven

[mtaylor]

Steven,

 

I like your approach.  You're thinking like someone of that era for solving the problem.   Curving the wood as it grows seems logical as I don't think we know if they knew about steaming it and bending it.  Fascinating watching the thoughts and research as this comes together.  

[Louie da fly]

Mark, 

 

We don't know if the Byzantines did it, but the Iberian (Spanish, Basque, Portuguese) shipbuilders of the 15th century apparently trained growing trees into the shapes they wanted - sort of bonsai, if you like. These guys certainly thought ahead, and I can't see why the same thing couldn't have been done elsewhere and elsewhen.

 

Steaming and bending? Probably, but no evidence we can rely on.[Edit: I believe this technology is so basic and widespread that nobody ever bothered to comment on it. I've seen heating and bending (steam really isn't necessary - wood is quite capable of bending just with the application of heat - especially if the wood is green) used to bend planks for a traditional Arab dhow, and Australian aboriginal people have used fire since the beginning of time to straighten spears. I'm sure the Byzantines had this technology, but there's simply no written proof.]  

 

Steven

Edited June 20, 2018 by Louie da fly

[Mark Pearse]

2 hours ago, Louie da fly said:

the downward force of the halyard would cause a powerful moment (turning force) to make the cap piece pivot around its attachment to the mast

Hi Steven, yes you'd probably be correct on that....but perhaps the mast rotating isn't a problem - if the force stays in the same direction as the hook it would reduce twist loading on the mast. 

 

Could the shaped end be to help the lateen spar clear the mast as they go about? 

[cog]

26 minutes ago, Mark Pearse said:

Could the shaped end be to help the lateen spar clear the mast as they go about?

Interesting. Maybe to avoid it from passing over the top of the mast ...

[Louie da fly]

I had second thoughts about the location of the sheave. Logically, I'd have thought it should be at the very top of the arch of the "hockey stick" - it would be stronger there, and less likely to split off at the end. So I had another look at the picture in the Homilies; But really, if the line in the picture is to be believed I've already got the sheave in the right place. So I'm following the original drawing, even though it's a bit counter-intuitive.

 

15 hours ago, Mark Pearse said:

Could the shaped end be to help the lateen spar clear the mast as they go about? 

Mark, I think that's a major part of the reason for that configuration. It appears the lower end of the yard was pushed around behind the mast when tacking - there are contemporary illustrations of this being done - so the sail isn't blown against the mast. On the other hand, apparently it's not uncommon for lateeners not to bother with this, and just keep the yard in the same place and live with the loss of efficiency. 

 

The other major reason, per Woodrat, is:

 

On 6/18/2018 at 8:10 PM, woodrat said:

the halyard, at the end of the day, should pull the yard away from the mast so it runs smoothly as it raises and lowers.

These are similar reasons, of course - to provide freedom for the yard to move.

 

Carl, I don't think there's ever been a satisfactory explanation for the "hockey stick" configuration - not that I've seen, anyway. "To hold the halyard forward of the mast" is about all I've come across. So we're reduced to guesswork, but at least it's educated guesswork.

 

Steven

[Louie da fly]

Onto the mast steps. I've been very fortunate that Professor Cemal Pulak of the Texas A&M University who took part in the excavation and study of several of the Yenikapi wrecks in Istanbul has kindly provided me with information and advice on various aspects of the wrecks, including the mast steps. I'm very grateful for his help.

 

The Byzantine mast steps are a bit of a puzzle - there are aspects of them that haven't yet been satisfactorily explained. The ones that have been found have each had two mortises - one a simple slot, the other longer and with an angled base to the slot. The simple slot is (in one wreck - they vary from ship to ship) about 200mm (10") long and about 600mm (2 ft) forrard of the other which is about 800mm (2'7") long. The angled base is deeper aft than at the forrard end. By the way, despite my drawing, in most mast steps found the straight mortise doesn't go right through the step - it stops short.

 

 

Exactly how this worked is still unknown, though there are currently a few theories. I've got my own ideas which may or may not be correct. None of the wrecks discovered has been found with both mast step and mast partner in place, so the relationship between the step and the mast is not known - which is why it's difficult to figure out how it all worked.

 

For my own model, unfortunately I introduced a further complication when building the hull. I was under the impression that all the wrecks had keelsons, so I put one in my model. Now it turns out that very few had them. The wreck I based mine on was one of them and its mast step hadn't survived, so I don't know what kind of step goes with a keelson. So I've done something which could have worked but hasn't any firm basis in archaeology. It doesn't have the two mortises (I didn't have long enough pieces of wood the right thickness), but it should do the job. I'd have preferred to do it exactly right and test out my theory about the two mortises, but it's probably too small a scale to test it out properly anyway. And as it's all going to be hidden below decks it doesn't really matter too much.

 

Here it is:

 

Glueing one side piece to the centre pieces to make the mortise. I could have used a single piece and cut the mortise out but this seemed easier.

 Adding the other side piece

   

Cutting the angled ends of the assembly.

smoothing off the top with a file:

   

Finishing off, and the assembly dry fitted in the hull.

The eagle-eyed among you may notice that the pictures don't quite align with each other. That's because I fudged it a bit. I've taken photos of the various stages of the two different mast steps and combined them as though it's just one.

 

Steven

Edited June 20, 2018 by Louie da fly

[Louie da fly]

Here's my idea of how the mast step in Byzantine vessels worked. I haven't tried it out and don't know if it would really work, and I certainly don't know if that's what they actually did, but it's a possibility. 

The mast sits in the forrard mortise with the fixing block slotting into the other mortise, and a wedge between the two to secure the mast and also impose a rake on it as it leans against the mast partner. The angled bottom of the second mortise would enable the fixing block to be dropped into place and help it stay in place against the horizontal force from the mast and wedge. That's my idea, for what it's worth.

 

Steven

[Mark Pearse]

Hi Steven

 

the setup you've drawn would allow disassembly - the fixing block could be removed by a hefty thwack from the side. I am guessing that with the loads & movement of the boat, the difficulty is having a mast step that is both strong & also reliably easy to take down.

[BANYAN]

Your research effort and commitment to authenticity is commendable Steven.  The model detail is looking good!

 

cheers

 

Pat

[Louie da fly]

5 hours ago, Mark Pearse said:

Hi Steven

 

the setup you've drawn would allow disassembly - the fixing block could be removed by a hefty thwack from the side. I am guessing that with the loads & movement of the boat, the difficulty is having a mast step that is both strong & also reliably easy to take down.

Exactly, Mark. Those were the considerations I had in mind when trying to come up with a design for this. I expect the mast would also have been wedged in place as it passed through the deck.

 

Funnily enough, the "strong" part doesn't seem to have bothered the Byzantines all that much - some mast steps were just fixed to the floor of the vessel with a couple of nails, some were loose - just held in place by the weight of the mast!

 

Thanks, Banyan. Much appreciated - particularly from the builder of the HMCSS Victoria, which I've been following with great admiration.

 

Thanks everyone for the "likes".

 

Steven

Edited June 21, 2018 by Louie da fly

[Louie da fly]

Well, I finally got the mast steps and masts together and dryfitted into the hull. And really, not very happy with the result. I based the mast lengths and positions on those in Age of the Dromon, (calculated by extrapolation from the known mast sizes of Sicilian galleys of the 13th century) but they just look wrong.

 

 

I checked and discovered that I'd made the middle mast too short; fair enough, my mistake. But even when I put in a dummy mast the right length, it still didn't look like the two masted lateeners in contemporary pictures, even allowing for artistic licence and the tendency of artists of the time to make the ships smaller, shorter and tubbier than they were.

 

  

I'm having serious doubts about the whole issue of two different kinds of masts (which comes from Age of the Dromon) and all through the build I've had a problem with the idea of two masts rather than one. The evidence on which the two-masted concept is based is equivocal - some points to a single mast better than it does to one (for example for the Crete expedition of 949 AD twenty dromons were to be provided with twenty masts. Sounds like one mast per ship to me. But the explanation for this in the book is that these masts (described as khalkisia) were "blockmasts" - with sheaves at the masthead, and that there would have been another mast without sheaves - the one with the hockey stick top. But then the two masts would have been of different types, which doesn't tie in with the pictorial evidence.

 

I'm prepared to give it another go - make another middle mast, and make it the same thickness as the foremast, and see how that looks. But I may end up going with a single mast after all, as shown on the only picture I know to be of a dromon of the right time (it has two banks of oars and shields on the sides, and is using Greek Fire.)

Steven

 

 

Edited June 21, 2018 by Louie da fly

[mtaylor]

Steven,

To my eye, there's distortion and point of view issues with the artwork sources.   Try switching the masts... tall one in the middle and shorter one at the bow.  They possibly could both be the same length so there wouldn't be a mix up at sea.

[Landrotten Highlander]

I was thinking along the same lines as Mark:switching masts (some of the pictures suggest this con figuration) or make them of equal length.

 

Slainte gu mhath

L.H.

[Louie da fly]

Mark and LH,

 

As I understand it, it's important to have the larger lateen sail towards the bow, otherwise the ship can't be properly controlled - the "centre of effort" has to be forward of the "centre of resistance" (which is effectively amidships), so the ship is being pulled through the water instead of being pushed through it. Certainly, that's my understanding, and Age of the Dromon states this was the invariable  practice with mediaeval lateeners. With our own square-rigged tradition, we tend to expect the middle mast to be the biggest, but the lateen rig works differently.

 

I'm doing some more checking on this - there's a very good thesis on the rig of the Serce Limani wreck which goes through the theory in some detail, and I'm going to go through it again, but I'm pretty sure that having the bigger sail towards the bow is correct.

 

Making the middle mast thicker and longer may solve some of the issues, but I'm also not totally confident of the mast lengths - how much similarity was there really between the rig of an 11th century Byzantine dromon and that of a 13th century Sicilian galley? Two hundred years different and a different society and culture, with Western rather than Eastern shipbuilding traditions. 

 

However, my major issue is really the conflicting information about whether these things had one or two masts. I'll give it a go with a new middle mast, but I'm keeping my options very much open.

 

Steven

[Louie da fly]

Whew! I've just been studying the theory behind the theoretical sail plan for the Serce Limani ship. Basically, I had the right idea above - the centre of effort (the theoretical point through which all the forces acting on the sail(s) act - has to be directly above or slightly forward of the centre of lateral resistance (the point through which all the water resistance forces act - about amidships).

 

Then we have to estimate what sail area is necessary to propel the ship through the water. This is almost impossible without a lot of higher maths and a lot of computer memory, or a huge tank and a hull model. (I have the model, but I'm certainly not putting it into a tank.) But it can be done by comparison with other vessels. It's been estimated the Serce Limani ship would have needed about 100 square metres of sail. It's short (about 15 metres) and tubby, while the dromon is long and thin (30 metres), which reduces the water resistance per metre, but increases the number of metres of water resistance. So perhaps these two figures cancel each other out (approximately), and I should be allowing for about 100 square metres of sail for the dromon.

 

NEXT, the higher of the centre of effort above the centre of gravity, the more likely the ship is to turn turtle. The bigger a triangular sail, the higher (and further aft) the centre of effort will be.

As a dromon will turn turtle if you look at it the wrong way, it seems to me that two masts, each with a smaller triangular sail and thus a lower (and more central) CCE (combined centre of effort)  are the better option.

 

Both these diagrams are taken from "The Rig of the Eleventh Century Ship at Serce Liman, Turkey" by Sheila Diane Matthews. My understanding is that it is acceptable to use these for study or discussion, but if the moderators believe it is unacceptable I will remove them.

 

So the masts and sails have to be placed so as to put the centre of effort above or slightly forward of the centre of lateral resistance. I'm going to work this out on AutoCad to get the sizes of sails I need, and where and how big the masts should be, to achieve this.

 

Regarding the larger sail being at the bow, I quote from Age of the Dromon: "from antiquity to the end of the Middle Ages all lateen-rigged ships of all kinds, including war galleys, always had their largest mast and sail towards the bow and a smaller one towards the stern. The documentary evidence for this for Western galleys of the High Middle Ages is very clear and there is no reason to suspect that it was not the case also for similarly-rigged Byzantine dromons".

 

Which pretty much puts it in a nutshell. I'll go with this and see where it leads.

 

Sigh.

 

Steven

Edited June 21, 2018 by Louie da fly

[Landrotten Highlander]

Thanks you for this insightful comment.

I think the reference to your source is adequte, as anybody can both find the work you refer to and it is clear that you do not claim that work as your own (this is one of the criteria to identify plagiarism in scientific circles).

 

Slainte gu mhath

L.H.

[Mark Pearse]

thanks Steven. Have you seen this video of a replica longship at sea? 

 

 

 

No doubt there are differences, but the hull righting moments might be similar to your craft. The incredible work done in Denmark & Norway on these craft have shown we previously greatly underestimated their abilities, & I might add the hulls seem much stiffer to heel than I would have guessed. A low square sail would be somewhat comparable to low triangular sails. Hope it helps.

 

all the best,

Mark 

[Louie da fly]

Thanks, LH. That's what I'd thought.

 

Mark, that's an amazing piece of footage. It's hard to believe the ship doesn't get swamped by those seas, but back she comes, every time. An incredible amount of movement (and I'm sure the waves get even bigger at times).

 

Unfortunately, dromons don't appear to have been as stable. Age of the Dromon's calculations are that with over 10 degrees of roll it would swamp the oarports and turn over. VERY little freeboard. Experiments with the trireme reconstruction Olympias seem to confirm the instability. These ships were built for speed, not ocean-going.

 

Steven

[mtaylor]

Interesting research, Steven.  I'd go with it.  I'm wondering now if our eyes expect the mast at midships to be the tallest.   Is there any indication of how much taller the foremast should be?  I find it a pity that much of what ship builders did even 200 years ago wasn't documented somewhere to explain the "why" part.  

[Louie da fly]

Thanks for all the "likes".

 

Mark, Professor Pryor estimated the foremast would be 11.85 metres long, and the middle mast 8.4 metres - these being 75% of the sizes of the masts of the Sicilian galleys of the 13th century, as the dromon was about 75% of the length of these galleys.

 

I'm currently working on diagrams for the sizes of sails to reach an aggregate of 100 square metres, while having the CE above or slightly forward of the CLR. I chose two configurations adding up to approx 100 square metres - one where the foresail is 12 metres long and the "middle" sail is 8 metres (corresponding to the relative sizes of the masts), and the other where the foresail is 11 metres and the middle sail 9 metres.

 

Doesn't look quite right yet - I think the sails need to be bigger - which in turn raises the height of the CCE. On the other hand, these sails would probably only have been used if the wind was from directly aft, so the ship didn't lean more than the fatal 10 degrees.

 

Still a work in progress.

 

Steven 

Edited June 22, 2018 by Louie da fly

[Louie da fly]

I checked Age of the Dromon again - it does contain estimates of the yard lengths for the two lateen sails - 20.17 and 15.43 metres, based again on 75% of those of the Sicilian galleys.

 

I tried these against the rough drawing of the ship, putting the Centre of Effort directly above the Centre of Lateral Resistance, [edit]while keeping the mast heights the same[/edit].

 

 

 

Note that the shape which produces the most power for a given length of yard is a 90-45-45 degree triangle, but these yards are at 32 and 37 degrees [edit] due to the height of the masts. Higher masts would enable a greater angle. [/edit]

 

However, although modern lateeners certainly sail with the yard at 45 degrees

 

 

they also quite commonly have the yard at a lower angle,

 

so perhaps this is correct. (Note, by the way, that the above picture shows that the mariners haven't bothered to move the bottom end of the yard to the other side of the mast when they tacked - the sails are being blown against the masts).

 

Certainly you come across a lot of renaissance pictures of lateen-rigged galleys with low angled yards - mostly furled . . .

 

but sometimes also under sail.

 

And the mediaeval pictures also often have yards at a lower angle than 45 degrees (see the posts above).

 

So I'll go with this and see how it works. However, it occurs to me that the Sicilian galleys didn't have a forecastle or central castles as the dromon does, so I'd be justified in having higher masts, which could perhaps have the 90-45-45 triangle after all.

 

I also worked up a drawing of the dromon with a single mast, showing the Centre of Effort directly above the Centre of Lateral Resistance. It looks good too, though the CE is considerably higher than on the two-masted version. [edit] The mast is higher on this one than the lengths shown in the book. [/edit]

 

 

Steven 

Edited June 25, 2018 by Louie da fly
added info re mast heights

[cog]

thought you might like this one