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A small cog by silverman834 - scale 1:20 - c. 1410


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Hello, I just found this forum and find lots of information that help in my build, thank you very much. And perhaps I then also should make a build log of it.


It is a scratchbuild of a small cog from around 1410 and it will be my third boat model and my first scratchbuilt. A month ago I started to watch the Youtube channel 'From acorn to Arabella' where they build a wooden ship and it made me also want to build one, but I felt that I don't have space for anything much bigger than around 2'.


I dabble in medieval reenactment, so I wanted to find a ship from the 15th century and it must be small so the scale will be large so the wood working details will not be too small.


Looking around I found a list of medieval wrecks and simply chose the smallest one from the correct time period. It was called NZ43 and was 11 meters or 36 feet. And then I found the thesis work 'A cog-like vessel from the Netherlands' not only describing the wreck in detail but also hypothesizing on how it might have looked when used. (it looks a lot smaller in this image, but the sailor stands on an aftdeck to control the tiller)


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Two of the most striking features that the author hypothesizes about are the bipod mast and the boom for lifting cargo. The planking will also be very interesting and challenging as some of the strakes will be flush midship, than lapstrake and than go back to flush in the ends. Let's see if I will be able to do this. And the strakes are of different widths which I think will look interesting.

 

I chose the scale 1:20 as this would land the size to just under 2' and it will mostly be built in fir as I live in Sweden and it's readily available everywhere.

 

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The first step was to make plans.  The thesis included this plan, but the sections just tell you the final shape of the hull and not what each frame looks like.  (the thesis is readily available from the web, but I compressed the plans any way in case somebody worries about copyright infringement)

 

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This illustrates where the frames are and where the sections of the plan are. They do not line up.


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I imported the sections into Inkscape and extrapolated the shape of the frames. The black curves are the sections from the plan and the red ones are my frames. The general shapes are from the drawing, but how they connect to the keel plank is based on measurements of my model.


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The midship frames are made out of three pieces, floor and futtocks, and frames towards the ends just have the futtocks. Scrapwood is added as support. Some of the joints are also reenforced with treenails. I think that only the floors were sawn in the original and the futtocks were bent to shape, but I'm sawing them all.


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The spine of the ship consists of stems connected to the keel plank via hooks.


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The joints are reenforced with treenails.


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Rabbets are cut for the planks in the stems and hooks.


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I have to reenforce the model with something sturdy to fasten the frames to as the boat just have a flimsy keel plank and not a real keel .


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The frames are glued into place with wooden blocks connecting the frames. The lines on the frames show the top of the sheer strake and where the frames will be cut.


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You can see how the frames get thicker towards the ends, this is based on measurements from the wreck.


The frames are not yet chamfered. I thought about doing it before fastening them to the model, but decided to try to do this afterwards with a dremel. Let's see how that works out...
 

 

 

 

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Nice to see another mediaeval ship, Silverman, and nice to see another cog! I take it you re-enact 15th century stuff?

 

You're already well into it, and the model is already looking very good. I like the fact that you're basing it so firmly on research and archaeological finds.

 

A bipod mast on a cog seems very unusual. What does the author base that on?

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I applaud your choice of subject and have something of a penchant for the working mediaeval vessel myself. I am happy to see you are referencing the excavation report. Do not hesitate to contact the archaeologists as they will undoubtedly be keen to assist you. Those trenails seem a little oversized. Does the thesis give information on their diameter. I find Byrnes trenail maker very cheap and easy to use to get accurate diameters of trenails (I use split bamboo to make them).

Good luck with your build of a very interesting vessel.

Cheers

Dick

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3 hours ago, Louie da fly said:

Nice to see another mediaeval ship, Silverman, and nice to see another cog! I take it you re-enact 15th century stuff?

 

You're already well into it, and the model is already looking very good. I like the fact that you're basing it so firmly on research and archaeological finds.

 

A bipod mast on a cog seems very unusual. What does the author base that on?

Thank you, I really like to use good sources for my reenactment. I started out with early 14-century, but am switching over to 15th century as they had nicer accessories then.

 

Yes, the bipod mast looks unusual indeed. I'm not fully convinced by the author, but I roll with it as I like the look of it.

 

The wreck have two heavy chocks where the mast step lengthwise should be, but far to the sides and she argues thus:

Screenshot_20200811-172829_Drive.thumb.jpg.de5605c244f4d83a93a50e5da0c5be3e.jpg

The seal that she refers to looks like this

Kuinre-rechten-Zegel-1399.jpg.c5a92091bac9f7478ec12158d6d6f775.jpg

(But I honestly think that it also could look like shrouds)

 

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3 hours ago, woodrat said:

I applaud your choice of subject and have something of a penchant for the working mediaeval vessel myself. I am happy to see you are referencing the excavation report. Do not hesitate to contact the archaeologists as they will undoubtedly be keen to assist you. Those trenails seem a little oversized. Does the thesis give information on their diameter. I find Byrnes trenail maker very cheap and easy to use to get accurate diameters of trenails (I use split bamboo to make them).

Good luck with your build of a very interesting vessel.

Cheers

Dick

Yes, I think too that they are a bit oversized, but the report actually says that the biggest ones were 4 cm. My local hobby store didn't have thinner, but I should defintly look into using a draw plate to make smaller ones, thank you!

 

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Välkommen till MSW!

 

As has already been mentioned it is a really interesting subject you have chosen. Several unusual features in the construction of the find, such as the thin keel, frames that are wider in the top, and the bipod mast. This will certainly be interesting to follow!


Is there any information available on the net of the find?

 

 

 

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Silverman,

 

Three thoughts:

 

Your choice of wood:  Fir (the English seem to interchange Fir as a name for what is Pine here, but regardless, similar characteristics for this use.)

Using a softwood species for frames, planks, beams, chocks, ...   you are making this a more difficult, frustrating, less elegant process than it could be.

Guys a lot closer to you than to me, seem to have ready access to all the Pear they need.   You would probably really like how it looks and works a lot more than Fir.

If you want a lighter color,  there is Maple - in your case -  Common Name(s): Sycamore maple, European sycamore  Scientific Name: Acer pseudoplatanus

 

The planking -  The usual nature of lapstrake/clinker planking  is flush - in a gradual transition - only at the ends.  Are you certain that the middle is flush?

 

Frame first -  Have you considered making a plug/inside the planking mould?  Planking over that?  Adding the frames to the inside of the hull?

 

I will be subjected to stoning,  but if a Byrnes draw plate costs more than is in your comfort zone ( I own one, so it is not about quality)  drill gauges can do the job.

Here, wire gauge drills,  there are two   necessary  #80 to #61   and # 60 to ~1/4" not sure - but only the #50's really matter.

Bamboo skewers can make strong trunnels.  The species of Bamboo used can make a big difference in how easy it goes. 

hard strong holds together needs a lot of force

hard brittle fights you all the way low vield

soft holds together peels off with less work - do not hammer -push

soft splits easily crushes  not worth the effort

This may require visiting different vendors  -  if you have a local independent Chinese grocery store - there may be several types available as well as Bamboo chopsticks

Gripping the bloody things - to pull them thru - without crushing - a constant challenge.

 

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Jaager, thank you very much for your thoughts. That's one thing that really impresses me of this forum - how much well thought feedback people give.

 

Wood: Yes, I'm beginning to see your point. One reason that I use fir is that I'm a bit sick of how hard oak is from some other projects. But something inbetween might be a better chose. Such as pear as you suggest. I will think about it.

 

Planking: from the thesisScreenshot_20200811-221011_1.jpg.43e651d4318ec5ca3ea2dffeff31fe8a.jpgand at another place it says that these strakes get flush again at the rabbets.

 

Frame first: That was my first plan. But I'm afraid I will get to much internal stresses in the planks that it will deform the shape when I remove the plug.

 

Draw plate: I will look what a Byrnes draw plate costs in europe, but your idea of drill gauges sounds as an alternative! I did a quick test of just drilling holes in a steel plate, but I'm not yet sure of how that turned out.

 

Interesting thoughts about bamboo. Somehow I just thought it was all the same kind, which it of course is not.

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7 hours ago, silverman834 said:

I started out with early 14-century, but am switching over to 15th century as they had nicer accessories then.

Yes, early 14th century is rather "generic mediaeval" - 15th is the start of a huge change in all kinds of things - tailored clothing, armour, you name it. And, of course, ships - 15th century sees the birth of the carrack. Interestingly, quite a few early 15th century ships seem to be a transition between the cog and the carrack, so it's hard to categorise them as either one or the other.

7 hours ago, silverman834 said:

Yes, the bipod mast looks unusual indeed. I'm not fully convinced by the author, but I roll with it as I like the look of it.

Yes, I tend to agree with you that the lines on the seal could be interpreted as shrouds rather than a bipod mast, and it's a rather thin piece of evidence to base a definitive statement on. However, I agree with you - it's your model, it'll be unusual and interesting, and nobody can prove you wrong . . . :D

 

I agree with Woodrat about contacting the archaeologists. I've often found them to be (i) amazed than anybody but themselves is interested in this kind of thing, and (ii) very helpful indeed.

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4 hours ago, silverman834 said:

Planking: from the thesis

The description in the thesis is clear as mud to me.  It does not read as though it was written by someone who understands hull construction.

You could correspond with him and further define just what he means by:

"lay flush"  

"were not fastened to one another" - as opposed to?

"stakes overlapped"  a picture of what exactly he means

"the central......garboard....not connected to it."   apart from Med very ancient blind mortise and tenon plank to plank - the attachment is plank to internal structure - the between is for waterproofing material

"the bottom and bilge strakes..."   is he describing carvel planking where the planks would grind in a beach?  There was a time of transition from clinker to carvel - but I imagined it was between strakes and not within one.  The hull having a carvel planked bottom and lapstrake sides up to the rail. 

 

About the plug.   The trick is to fix each plank to its final curve before it is attached.  Pre-bent as it were.  This way, they stay were you fixed them.

 

Plank bending 101

The lignin that holds wood fibers together is not soluble in water. 

Heat loosens its bond and allows for bending while hot and staying in its new position when back to room temp.

Steam transfers heat better than dry air . Wetting wood before bending is to provide steam.  The time of immersion need not be long.

Different species of wood have very different reactions to being bent.  Some are pliable and some would rather break.

Lignin is soluble in ammonia.   But it is the anhydrous ammonia that was used for commercial refrigeration and is liable to explode.  The active part of cleaning ammonia solution as far as bending is the water that it is in.  The ammonia there just ruins the surface of the wood and makes it an ugly color.

There are many ways to provide the heat.  The trick is to choose a way the does not cook you in the process.  Does not char the wood.  Does not dent the wood while bending it.

 

Your homemade draw plate = 

to cut/shave the wood,  hard steel = good. 

stoning and honing a crisp cutting edge at the hole and holding it  hard steel = good

drilling the hole to begin with  hard steel = not so easy

 

For draw plate trunnels - bamboo is pretty much it  getting something to draw from wood is too much work and too much is wasted.

For short - just for show trunnels  you can find examples here of   steel medical needles --  tip ground to be like a lab cork borer -  drill press - stock is a block of wood and boring it on an end grain face.   

If you drill thru the block, the trunnel is longer, but stays in the bore.  I do not know if boring the next open will push the earlier one up the bore of the needle or just stop the process.  If it moves on up, I guess the quill center could fill with trunnels.  If it does not move, pulling the needle , and ramming the trunnel out for each one would get tedious real fast.  

The other way is to bore part way and when as many as can be got are bored, the distant end is cut off at the intersection at the depth of cut.

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1 hour ago, Jaager said:

The description in the thesis is clear as mud to me.  It does not read as though it was written by someone who understands hull construction.

You could correspond with him and further define just what he means by:

"lay flush"  

"were not fastened to one another" - as opposed to?

"stakes overlapped"  a picture of what exactly he means

"the central......garboard....not connected to it."   apart from Med very ancient blind mortise and tenon plank to plank - the attachment is plank to internal structure - the between is for waterproofing material

"the bottom and bilge strakes..."   is he describing carvel planking where the planks would grind in a beach?  There was a time of transition from clinker to carvel - but I imagined it was between strakes and not within one.  The hull having a carvel planked bottom and lapstrake sides up to the rail. 

   It sounds to me like he is describing carvel planked (flush) and clinker/lapstrake (overlap).  The first three strakes (garboard, broad and #3) were carvel and the rest clinker.  The sources I have read do indicate that in estuaries and such, the cog could/would settle onto the river bottom.  The flush planking would facilitate that.

 

'The garboard strake lays flush to the keel and were not connected to it'.  Might that mean 'not physically nailed or bolted to the keel, but fitted into a rabbet'?

 

I know with viking longships and I believe with cogs, the floor frames were attached to the keel and the lower strakes attached to the floor.  After that (in this case strake #4 and above) were attached to the strake below it clinker style and only after the shell was complete were the first and second futtocks added.

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Chuck,

I completely agree about the three carvel strakes and then clinker possibility.  

On 8/10/2020 at 3:05 PM, silverman834 said:

The planking will also be very interesting and challenging as some of the strakes will be flush midship, than lapstrake and than go back to flush in the ends

It is this interpretation  that I am having a question about.   The same plank going from carvel to clinker along its length?  I can only see it as being one or the other.  If I am right, it saves a lot of work.

 

There are a couple of clinker projects that are active now.  When I looked up a question on the strake lap transition at the bow and stern rabbets, in a modern text,  (John Leather)  I also checked how the fittings were done.  Were there spikes that just went thru the plank overlap and were clinched on the lower strake's inside face?  It looks like the spikes were only at the frames and went thru the two planks and also the frame and was clinched on the inside face of the frame.  Were there any spikes that went thru one plank and then thru the frame?  No.  It appears that it was only at the overlap.  

 

My problem with the garboard description was because I have never seen any reference to a garboard having fittings at the rabbet at the keel and thru the plank into the keel.  My question is, why mention the absence of something that was not done in most any situation anyway? 

 

Thinking about why this would be the situation:

That seam is the most troublesome of all of them.  It is at the place  where two different planes meet, with different dimensional flexing,  I would guess that spikes could impair garboard reactive movement.  The stress could generate a split along the row of spike holes and turn the garboard from one board into two boards producing a fatal leak.  This happening when the sea was particularly lively.   I recall an illustration a ship suspended between two oncoming waves.  One was holding up the bow and one was holding up the stern, with the middle hanging in the air.  I believe it was about hogging and what could cause it.  

 

 

 

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Here is a diagram of how the transition mid-strake from flush to clinker was made

 

flush.png.75e2fa28a4be5d6ec7a6f5ac4a35d785.png

 

Some of the transitions were like this where a plank suddenly got wider to overlap the previous one, but in other places this transition was made at scarf joints where the builder just added a wider plank.

 

Regarding contacting the author I'm sure she would be suprised to hear from somebody reading her 30 year old thesis!

 

And regarding how there was a transition in this period from cog to caravel - I'm a big fan of how the thesis doesn't say that this was cog, just that it is cog like to not be bogged down in discussions about defintions.

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1 hour ago, silverman834 said:

I'm sure she would be suprised to hear from somebody reading her 30 year old thesis!

But also pleased, if she's still around. Worth a try! I've had good success with this kind of thing, and so has Woodrat.

 

1 hour ago, silverman834 said:

And regarding how there was a transition in this period from cog to caravel - I'm a big fan of how the thesis doesn't say that this is was cog, just that it is cog like to not be bogged down in discussions about defintions.

Yes, at this period in particular, you often can't fit a vessel into a category (most of which seem to have been invented by academics anyway). I've put together a collection of pics on Pinterest of various periods and types of mediaeval and renaissance ships, at  https://www.pinterest.com.au/lowe1847/boards/ which you might find of use.

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Silverman,

That planking technique is unique or seems to be.  The illustration clarifies the what and how.  This craft may well be a "missing link" in the transition from shell first to frame first.  

I wonder if that particular planking joinery may have left something to be desired as far as stability and reliability?  The result of that experiment being the reason it was where it could be found far in its future instead of joining the fate of its fellows? 

22 hours ago, silverman834 said:

One reason that I use fir is that I'm a bit sick of how hard oak is from some other projects

I can see how for everyday full size projects, Fir vs Oak is a choice to consider.  In the scale model world, I recommend forgetting that Oak even exists.

Oak is hard, but it is also pug ugly at most any model scale.  It may be useful for totally hidden structures.  But a negative factor for even this is that in some species of Oak, the fibers, being coarse, do not hold together at shape edges and the way out of scale pores could be at the edges and leave dips.  They are awful enough on the surface.

One of my preferred species of wood is a Maple that is fractionally harder than White Oak.  It is no problem as long as tools are sharp, motors are powerful, and for bulling away a bulk of it - 60 or 80 grit sandpaper.  I find that the resistance to being able to easily overdo its removal to be a plus.

All the more power to you, but the fuzzy nature of a true Fir would have me wanting to act out in frustration.  I find this is much more fun when the species of wood being used works with me, and rewards me in how it looks when replicating something its miniature in scale.

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Thanks forthe links Louie! I have not read these and they seem to contain interesting bits about the decking.

 

There's not much to report on the build, the framing continues. I printed a couple of figures to have as size references to get a better feeling of the scale. Usually I just work on one frame at a time, but now I drew all remaining on the wood as I don't think that neither my girlfriend or neighbours much would appreciate sawing at 6 am on a sunday.

 

The framing looks uneven. Which it should. There are three different spacings between them and one extra big gap where the mast steps are.

 

One of the frames got a bit big and that will be taken care of when smoothing them all out and making the bevels.

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Fairing the hull was easier than expected. I thought I would have to do it by hand, but the model was sturdy enough for using the orbital sander. Two mistakes happened. A scarf joint broke between a floor and futtock, but that was an easy fix. Next thing was that a frame proved to be too small. So I had to cut it off and replace with a bigger version. I had marked the sides of the frames with pencil before sanding so it was easy to see untouched parts and you see how this frame simply was too small.

 

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The new frame looked better.

 

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Those ugly blocks are temporary structures above the shear that will be cut away after planking.

 

Next up is lining off.

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On 8/18/2020 at 3:32 AM, silverman834 said:

The shape shows what a slow cargoship this must have been.

And yet it became the dominant vessel type for at least a century, and was copied in the Mediterranean. So it must have had a lot going for it. Probably cargo capacity had a lot to do with it, and though the square rig had been common in the Mediterranean in Roman times, it had been largely replaced by the lateen. Was there something about square rig that gave it an "edge" over the lateen?

 

You're doing great things - correcting such things as the frame that was too small will help you avoid problems later on. Keep up the good work. 

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Thanks Steven!

 

P8210001.thumb.JPG.8bf3a90a03acebb17751c8de50f661f9.JPG

Before lining off I had to mark the shear. I clamped a wide plank to get the line as straight as I could.

 

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I have seen people use this kind of template for lining off and made my own to get the different strake widths correct.

 

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All frames lined off.

 

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I made templates for the planks using masking  tape.

 

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Planks held in place with lots of clamps

 

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Treenails made from bamboo toothpicks corrected in size using my home made drawing plate (fancy name for a hole drilled in a steel plate). They are functioning and sticks out on the other side.

 

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The inside will look like an inverted hedgehog when the planking is finished.

 

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Gardboards are done! I try to mimic the placement of the joints of the planks in the strakes with the original's. They were sometimes placed between frames, but I will have them all on top of frames to make it easier.

IMG_20200822_201009.jpg

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Steven, thanks, and it's the same timber as the rest. And yeah, it's a bit too visible. But it's ok - I really like the idea for this project of simply using the simple materials that I can source locally. The next model will have better timber and I can then compare the difference.

 

Kent, thank you. But I'd rather have this kind of forum where people give critical, and constructive criticism, then just telling you that all you do is great.

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On 8/21/2020 at 5:41 PM, Louie da fly said:

And yet it became the dominant vessel type for at least a century, and was copied in the Mediterranean

I had thought the cog was purely a northern European phenomenon, from the North Sea and the baltic? I've heard this before though. After seeing woodrat's excellent carrack/cocha however, what struck me is how much the medieval Mediterranean ships look like earlier Roman ships with fore/aft castles bolted on to them - even down to the multiple prominent wales and the curved stems. Since learning about the super unique Romano-Celtic Blackfriars 1 wreck from around 150 CE (look it up, it's really weird!), I've been wondering how that fits in to the history and evolution of northern European ships too. EDIT: Lol, guess I answered my own question there without noticing - are the castles and stern-post mounted rudder what was copied from the cog in the Med?

 

But back on topic, this is a really cool build idea Silverman! I like these different build ideas like this. That two footer mast is very interesting! It's coming along nicely too, looking forward to how it progresses!

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