KrisWood

First step is trying to read the numbers from https://www.academia.edu/49550641/Rekonstruktion_af_Osebergskibet_Bind_II plan 2 (page 26). This will be necessary for the curvature of the keel, which is what all other numbers are based on. I've got all the numbers plugged in from page 29. The green lines are the stations. Lines below the base line are ones for which no height was given in the plans.

Hi all! It's been a while. I had to take some time away while life got in the way of hobbies. Things are settling down now and I'm thinking about picking this up again. This time around I'd like to start over and do it open source. Most of the lines can be derived mathematically. Some of the lines cannot be derived mathematically and must be based on existing reconstructions. My question is, if my CAD files are drawn by hand by me, how different must they be from existing plans to count as original work?

That is what I thought. I found the equivalent of Max's FFD boxes. It's called Cage and CageEdit. It takes a little getting used to but gets it into the right ballpark and I can improvise from there, though it's never going to be exactly accurate.

Two questions for you all... 1. How do you project curves onto a surface in Rhino? 2. My reference materials from the stems are, I think, based on Johannessen's reconstruction drawings and Sofie Krafft's detailed drawings of the carvings. They do not line up with Ms Bischoff's reconstruction. In my game modeling days in 3D Studio Max there was a tool called Free Form Deformation that could scoot curves into place en-mass in situations like this. Is there an equivalent in Rhino?

Now to do the aft stem and then I'll be ready to slice it into printable layers. Edit: oh wait, I still need to figure out how to project the carvings onto the stems...

And next question is, depth of rabbets, drawn in CAD or just the placement of the rabbets and cut them to depth physically when building? Edit: Here's a fun diagram to explain how to draw the depth of the rabbets on any Viking ship that has them. It's actually surprisingly easy. The following is a cross section of the stem at a point where I have no numbers beyond those calculated from the documentation for top and bottom width of the keel / stems. The plans have lines for the top and bottom of the rabbet and the bottom of the keel in profile view. I've drawn these as horizontal lines in RED. Given the measurements of the widths from the documentation, I can now make a trapezoid shape connecting the dots, which I've done in BLUE. Next I draw the depth of the keel as two circles, centered at the intersection of the red lines with the blue line, which I've drawn in GREEN. I'm not bothering to taper my planks, so my circles have a diameter of 2.5cm along the entire length of the keel / stems. To get the correct ANGLE of the rabbets, draw a line connecting the two circles from the intersection of the top circle with the top red line to the tangent of the bottom circle, which will give a perfect right angle to the bottom of the rabbet, drawn in BLACK.

Question: Is there a good (free?) automated tool for importing ship plan drawings from any raster format into any vector format which can be imported into Rhino? I've tried a number of methods but they all end up with curves drawn as bubbles around the black lines rather than through the middle of the black lines. I've got photoshop if anyone knows of a method there as well.

Finished the port-side fore-stem carvings, moving on to the "tingl".

So many carvings to get into the right format. This will take a while...

Drawing the carvings for the first time. I'm going to need to print them on card and then paint over the parts that are too small to cut. It's fun to be doing art instead of math for once on this project. And with that I'd better get some sleep!

Ok, I'll start a new one when I start my card build and return to this one when I can work with wood again. 🙂

Hi everyone! It's decision time. I am unable to proceed with a wood project at the moment. In the meanwhile I'm going to proceed with card unless anyone has a CNC mill and wants to collaborate on making parts. (Anyone here interested?) Now I'm considering two questions: What is a good scale for working with card? 1:75 fits the entire keel on a single US Letter sized sheet of card stock so I can print it in one piece, but I think the parts will be too tiny to get the level of detail I'd wanted for my project. I've decided to go with 1:50 Since this thread is for my wood project, should I start a separate one for my card project, or just keep posting here? I've also got a separate thread for my CAD related questions in the CAD forum.

Ha. Hahaha. HAHAHAHAHAHAHAHAHAHAHA.... 🤪 I went and added my beautiful, new, mathematically derived lines for the stem back into my guesstimate that I'd made before the new, more detailed plans and numbers were published. All that work and none of the lines moved by more than a centimeter... My old guesstimate was as close as makes no difference at scale... 😆 That said, I guess I'm going back to a previous save and simply converting my files to a card-friendly scale/format... Edit: Also, the way I ended up getting a three dimensional stem-top was to take Johannessen's cross sections and adapt them to Bischoff's numbers, then voila, it matched Saga Oseberg. In doing so, I realized a simple truth about all Oseberg reconstructions. Every last one of them is historically inaccurate. In Mr Finderup's "Saga Oseberg" book, he explains that they ran out of time at the end of the project to fully analyze the remaining fragments of the stem top, so they went with a mathematically derived approximation in a single solid piece, even though the original used multiple pieces. Comparing excavation drawings to both Johannessen's and Bischoff's reconstructions, the original stem top would have been somewhat larger and at a different (somewhat unknowable) angle. Because it makes zero difference to the functioning of the ship, I think Ms Bischoff's approach is the correct one. Johannessen did what looked good for the museum display. Bischoff did what functions given the most probable dimensions of the planks which made up the hull of the ship.

Ok I'm stumped. I couldn't figure out how to model with solids like you did, so I did it my own way using open curves. I've forgotten how to get solids out of these though....

Count me amazed. How do you do that so fast? Are you using Rhino? The rabbets can be modeled more simply as being perpendicular to the inside of the stem and not cut out. That's how they were made on Saga Oseberg. They didn't cut them until they were ready to lay the next plank down, and then they cut it to the depth of that plank.

Hmm when saving it as a jpg it blurred the numbers horribly

Here's all the relevant details. Bischoff reconstruction on the left, Johannessen reconstruction on the right. How in the world would you model the transition from stem to stem-top?

Anyone want to help draw the stems? I'm having a heck of a time getting the thickness of all the parts correct. Most of the dimensions are on page 28 of "Rekonstruktion af Osebergskibet" Bind II. The dimensions for "Snit E" are on page 27.

The curved stems of Saga Oseberg pull the bow up slightly. The straighter, narrower stems of Dronningen caused it to dive naturally at the bow. 😣 Part of the problem with Dronningen was that it was built from Lundin's 1957 plans. Lundin didn't have access to measurements of all parts so he had to guess more.

I think she got it closer than the museum reconstruction. The original conservator didn't take into account that the keel had been flattened by the burial mound settling on top of it for a thousand years. He also assumed the decks/oar holes were flat, when they actually line up better if curved. The knees were broken in multiple places so any reconstruction is somewhat guesswork, though the museum display has them shorter than the excavation drawings. (Note, the original conservator also didn't have computers to do wood grain analysis to figure out which way the curves of broken pieces went together) Anyway, like the two of you suggested, I'm thinking I'll end up with something that looks very much like the oseberg ship, which does not agree 100% with the plans.

Next problem with my plans. I've got three kinds of errors: 1. Scanning / scaling artifacts: A number of the published resources were either scanned from paper or rescaled from digital files to the point where the numbers are too distorted/pixelated to read 2. Measurement errors: A number of the measurements in the resource materials disagree with each other within 1cm. There's no apparent way to tell which are the right ones 3. Typos: Unavoidable in any materials with this many numbers in them I've got a situation where some lines by the numbers are 1cm away from where they are drawn. Furthermore the numbers are out of fair. So I'm stuck with a choice, draw the lines as drawn, or draw them as calculated and try to fair them? What would you do?

The main reason I've kept them so far has been the scale I'm working at (1:25) makes it very difficult to find wood long enough to make the keel in a single piece. I'd still need to make scarfs for the stems anyway. 🤷‍♂️

Re-reading volume 1 of Ms Bischoff's work, she explains that the scarfs are not only S shaped, but TWISTED, so that no part of the top S curve is parallel with any part of the bottom S curve, thus creating interlocking curves. 🤪

For the CNC part, I had thought to: Use a sheet of wood a little more thick than the keel width. CNC four holes, one at each corner of the sheet so that it fits over guide posts Model the whole sheet with the keel turned on its side Have the CNC mill a little less than half the depth of the keel Flip the sheet over and mill the other side of the keel Then use an X-Acto knife to cut through the thin remaining wood around the keel, like the sprues on a plastic kit model. Would something like that work?

It seems bizarre to me that this problem might actually be more easily solved with technology the Vikings had available to them than with technology we have today. I started thinking about how I would solve the problem as a viking and it was intuitively obvious. I know the dimensions of the keel, including the depth of the rabbet, which I don't want the diagonal line to go through. All I need is a length of string a bit longer than the depth of the rabbet. Measure and mark that distance from one end of the scarph on the top of the keel. From that mark draw a circle with the string measuring its radius. Repeat on the other end of the scarph. Draw a straight line connecting the tangents of the two circles. Use the same ratio of keel width to circle radius to repeat the process on the bottom. I'll try it out in rhino after I get some sleep...