Die Kogge Von Bremen by kentyler

[kentyler]

Thanks for the clarification Roger

that's the plan.

I hope to construct a shell around the plug of the hull planking

then lift the plug out and put in the internal frames.

With luck, I want to make the model so the internal framing can be lifted out to inspect the framing

rather than leaving parts of the hull exposed.

 

[AnobiumPunctatum]

The planks at the bottom of the hull are krawel planked. So I think it is a good idea, to add some real frames to your shell.

Edited February 15, 2021 by AnobiumPunctatum

[Jaager]

On 2/11/2021 at 6:18 PM, kentyler said:

I'm going to assume that the lines provided are to the outside of the hull planking.

The Body Plan does not show a rabbet at the keel, so that is probable.  You intend to plank instead of the model being a carved hull, so that makes for an additional step in the lofting process, The planking thickness must either be subtracted from the lines, or the plans can be treated as though the lines are inside the planking.  The Body Plan is fairly straight forward about the way to do this for carvel planking (But it is a way too fiddly process for me.) The clinker is not evident and how much to subtract is ambiguous.  That it is not shown on the Body Plan provides points that support this being inside planking.  The waterlines and buttock lines intersect the planking at an angle, so any subtraction there presents a nightmare of the first order.  This is another lead bar on the side of the scales in favor of inside planking.

 

I would do this in a different way from your proposed method. 

The plug idea is a tried an true technique.  It is a common way of building ship's boats.  They are usually much smaller than your vessel as far as the size of the model, but that is just detail.  Your vessel is more boat than ship anyway.

I would make the plug from transverse segments. I would use the Body Plan to provide the shapes.  This is how most ship's boats plugs are made.

I would do most anything to avoid getting up close and personal with Masonite.  Awful to work in the way that you intend.  As far as your skin and lungs, it would be like rolling around nude in blown-in fiberglass.

Use 2x4 (or 2x6 or 2x8 depending on the needed dimension) framing lumber instead. The "bread slices" will be easier the rough shape before they are all joined up.  Off the shelf Bamboo skewers and dowels make handy alignment devises.  The locations for the dowels are done on the whole in the drawing program.  When the individual layers are isolated and printed, the dowel locations for the long axis are in perfect alignment.

 

Now - a major worry will be separating the plug from the finished planking.  I have an idea for a way to make this easier.

On the Body Plan - draw a line that is parallel to the center line and 1/6 the total width on either side of the center line.  This divides the cross section into 3 parts - a middle section and two outer sections.  When the planking is finished, the center section can be removed.  Then the two outer sections can be folded in and pulled out.  I came up with this as a way to use a plug for a hull with tumble home.

The trick is to devise a way to hold it all together as a single unit for abusive shaping- until you do not want them to be a single unit.

 

OK - make the plug taller than the rail.  The three parts can be held together by 2 or 3 transverse dowels.  The sequence of sections can be held together by much longer dowels going down the long axis.  Remove them and the plug becomes like that game where a tower is built with sticks and then sticks are removed trying not to collapse the tower.

During shaping, the 3 section parts can be held together with : 1. Duco and then use acetone  2. PVA and then Iso  3. Hide glue and hot ethanol.  The cross dowels can be drilled at this time. Two or three points and everything goes back together perfectly.

 

Edited February 15, 2021 by Jaager

[kentyler]

may end up slightly larger than a breadbox

the plans are taped down to be cut out with a jigsaw

i think the paper will have to be removed before gluing

thus the tape, instead of gluing the paper down

 

[Roger Pellett]

Accurately deducting planking thickness is not as simple as it might appear.  You have to consider the angle at which the planking crosses a station line.  For my last model I made a table of offsets from a lines drawing, entered this into an Exel spreadsheet, along with the required angle for each offset data point.  I then multiplied the planking thickness by the sine of the angle and subtracted the result from the offset.  It was then necessary to replot and fair all the data points.

 

My advice to you; don’t bother!  The lines that you have, were developed from  reassembled wreckage, so they are an interpretation of what she once looked like.  When completed you will still have an accurate representation of a Cog.

 

Roger

[kentyler]

Thanks Roger,

Good and helpful advice

Ken

[kentyler]

Still waiting for some help for my jigsaw. I think the battery has completely died. Planning in the mean time. Two holes through each piece for bamboo skewers..holes always "wander" a little. I'll center punch them and drill with a small drill first, then follow up with one that is just a little bigger than the skewers.

[kentyler]

Saw arrived. Now have nice pile of boards. Time to get out the drill press and drill the holes for the bamboo centering pieces.

[kentyler]

I actually was able to find a drill the right size for the bamboo skewers in my tool box

I drilled really small holes first, because on pressboard you don't get much "centering" effect from an initial punch hole

And then with a drill the size of the bamboo

I'm punching the outline of the next layer down through the paper before I do the cutting (because the paper is not glued on, when it is cut to the outline it will come off the board.

So I'll have the 2 pegs and the punch marks to guide me as I glue the layers together

[Louie da fly]

I made my plug from pine -  (following the technique Druxey used on his hospital barge)  out of narrow pieces (lifts) laminated together horizontally, mirrored each side of the keel, because I wasn't sure I could get the two sides of the hull symmetrical.  

 

I screwed together the lifts for one side and smoothed this side off, using the sections I'd cut out of cardboard to check that I'd got the shape right as I went. Once I was happy with this side, I pulled it apart again and used its lifts as templates to modify the lifts of the other side. That way I had the best chance of  getting the shape of the hull symmetrical.

 

 

The full process is here:  https://modelshipworld.com/topic/10344-10th-11th-century-byzantine-dromon-by-louie-da-fly-150-finished/page/2/

 

I also have doubts about masonite or any sort or fabricated board. I think you'd be better with actual wood.

 

In my case, despite the inward-curving "tail" of the hull, I was able to lift the plug out of the hull in one piece (though I was very worried about it when it came to separating them). And the shape of your hull, with no tumble-home, should mean you can just lift the hull off the plug. However, making it able to be taken apart would give you more wriggle room.

 

https://modelshipworld.com/topic/10344-10th-11th-century-byzantine-dromon-by-louie-da-fly-150-finished/page/9/

 

And - terribly important in my experience - WRAP YOUR PLUG IN CLING-WRAP! It keeps the hull and plug from sticking together, which you certainly don't want.

 

Steven

 

[kentyler]

Thanks everyone for all the helpful hints.

Making a little progress

I realized that the bottom 4 sections were NOT 3/8" thick

so I printed up some new plans

and sized the bottom sections.

I keep a stock of heavy card...and i can use one layer for the bottom section

and a combination of 2 thicknesses for each of the 3 layers on top of that

The card drills like wood

after I cut out a section it separates from the plan

I'll have to be sure and write its number on it, so as not to lose track

 

ps

in the 2nd to last picture you can see that i'll need 3 additional 3/8's sections in order to accomodate the full rise of the bow

 

[kentyler]

Got some new blades for the jigsaw and cut a few more pieces

layer 1 is a single thickness

layers 2, 3 and 4 had to be laminated to get them to the right thickness

of course, a little smoothing of rough edges will have to happen before gluing

[Louie da fly]

Good progress, Ken. I'm looking forward to seeing the next step.

 

Steven

[kentyler]

I gave up on the jig saw...there may be something fundamental i don't understand about using it...and switched to a sabre saw. As you can see we are into the thicker cross section. This is #6, so there are 6 more to go

[mtaylor]

Just a guess here on the jig saw... low tooth count maybe compared to the saber? Or the blade is dull.

[kentyler]

no, tooth count is higher, blades are brand new

blade is to flexible, i don't have the knack of getting it to follow the line of the cut

i don't think it's the saws fault... as my dad used to say... its the nut behind the wheel

[Louie da fly]

You've probably been pushing the work through the saw too hard. It's something I'm guilty of, and it makes the blade bend sideways.

 

Steven

[mtaylor]

I think Steven hit the problem.  I've run into that also. More of a matter of just relaxing and taking it slow.

 

[kentyler]

Three more layers. I had an anxious moment so I measured to get a height to compare to the drawings.

I'm 3/32 short....easily made up with some paper shims...so that's a relief

[kentyler]

all layers cut now... i will have to use three of the attempts that did not work to raise the ship high enough above the building board to have space for the bow

next I need to make the building board...with enough space to use it to position the section templates as I shape the hull

[kentyler]

here we are, ready to go
 

[Louie da fly]

Now for the fun part . . . 

[kentyler]

It's not nice to make fun of the poor boat builders

[Chuck Seiler]

Ken,

 

    What news?  The cog world awaits news of your progress.