Exploring FreeCAD for ship modeling

[Sailor1234567890]

Looks like the tuck for finishing off the grommet was tucked somewhere around the 8 o'clock position.  Nice job. 

[Dane]

Did this one made from 3 strands or from 1? 🙂

[TonyM]

Sorry about the delay in responding to Sailor and Dane.

Sailor - Yes the tuck was around 8 oclock and was not pretty. I can probably work to improve it but the ring was just to explore the method which was difficult.

Dane - yes it is done from 3 strands.

I have an easy method for a straight rope which is to form a polar array of 3 helixes and then sweep a circle of each strand cross section along each helix.

The curved rope (shown as a ring) is done by creating a polar array of triangles and 3D splines are woven through the points of each triangle forming 3D helixes around the array of triangles. Then I sweep the strand cross section along the splines. Very time consuming and I want to find a better way.

 

The purpose of the circular rope is to feed it through a block.

Here is a fragment of the schooner with the main upper throat block. 

 

 

 

[CDR_Ret]

Tony, that looks simply ... agonizing. I can appreciate how much labor went into those lines.

 

Terry

[TonyM]

Thanks Terry,

Actually it s not as bad as it looks. I have segments of straight rope that I fuse together and half circles which were cut from the ring earlier in this post.

It is still a bit rough and there is some discoloration which I will fix but the idea is to have rope components that I can assemble.

 

Tony

[Kris Avonts]

Hi Tony,

Glad to see that you made such nice progress on your schooner.

Sorry I didn't post some updates of my efforts to create a hull for a 74-gun ship.

But last week I finally succeeded in making several surfaces that represent the hull quite well.

Only at the stern it still has some 'wrinkles'. Maybe it is good enough to start lofting timbers.

 

Here is the framework of stations, waterlines and other guiding lines made from sketches.

 

And next you can see what the hull looks like based on the above frame.

 

So, after all, it is possible to make a ship hull in FreeCAD....

...but it requires significant effort and patience before a result shows up.

 

I hope you succeed in all your detail work with the schooner. It is inspiring.

best regards,

   Kris

[TonyM]

So I decided to fully rig the schooner since the display mechanism seems to be Sketchfab and my first attempts were quite encouraging.

The process was a bit tedious and involved exporting the model from FreeCAD in STEP then transforming it to .glb to load into Sketchfab. When I make the image public on Sketchfab I will reference it in the posts.

 

The rigging seemed to need sails so there is some exploration work to deal with surfaces in 3 dimensions and the projection of seams onto the curved sails. This is exposing challenges such as the geometry of the leaches (which are all straight at the moment) along with the angle of the gaffs, booms and sails to the centerline (which are also straight at the moment).

 

 

Obviously this is just a rough setup which will give me an idea of what is possible but progress in happening.

Edited June 1, 2021 by TonyM

[JeffK]

Impressive.  I’ve used some cad in my original layouts, but not anywhere this level of detail. Looks great. 

[Dane]

Hello TonyM.
There is a simple method to make a grommet which is a three strand ring but made from one long strand. You should go around a grommet in three turns. As a result you get rope grommet. There is a good explanation in ABOK:
2864, 2865. The COMMON GROMMET is made with a single strand in two ways. After completing two circles with any wanted number of loose turns, start the third circuit either as #2864 or as #2865, and continue to lay the strands parallel. The ends are finished off as in a LONG SPLICE. These two starts make all possible grommets of three leads. A grommet in Manila is tied preferably with a single. strand of four-strand rope. In tarred hemp, grommets are made of small stuff, the full size. EYELET HOLE GROMMETS in sails are of marline or small wire. The length of strand required for a grommet is three times the circumference of the grommet plus six times the round of the rope. 

Edited August 17, 2021 by Dane

[TonyM]

Some time has passed since my last post. I have rethought the rope construction which although successful was very expensive digitally when generating the rendered image which now can be loaded online at SketchFab.

 

 

 

The model is almost complete with some more running rigging to complete and I will switch attention to the displaying of 3D models.

The flat screen rendering is not very exciting and there is some new technology called "Light Field" display which I will research in the new year. It apparently gives a stereoscopic illusion using a special display screen. 

 

I will update the forum when I have more experience of this technology.

 

Edited December 20, 2021 by TonyM

[Andrew Egan]

Some very thought provoking stuff on here, I too use FreeCad, I am making RC models. I started in January 2021 designing and 3D printing at first for a styrene LCT model at 1/72 scale that I built about 20 years ago but didn’t quite finish. Then moved on to an LCG as I had built 2 hulls. The LCG had stalled on the armament, I drew the single 4.7” gun mounts in FreeCad. Took a couple of false starts but even the first efforts were good, printed on my Ender printer they were instantly better than I expected. Have to say I am a complete FreeCad addict now, drew up a D-class Fairmile hull and LCT2 and 3 hulls and detail. The LCTs are very simple until you get to the bow which was tricky. Key items for me are the loft and b-spline tools, thickness can be useful as well. Recently I have been designing for resin printing which really shows FDM up, but FreeCad has been excellent. The hand wheels on the capstan controls are 0.5mm thick. Couldn’t do that in FDM, in FreeCad I could even draw the rivets on the capstan brake band, and they are visible on the print. 

[Kevin-the-lubber]

You’re getting some nice results there in freecad. I tinkered with it about 18 months ago for maybe 30 minutes when looking to graduate from Tinkercad but settled on fusion360 as this was also free but looked better. However it has one or two major bugs and I’m wondering how freecad fares in relation; the worst bug is that f360 can hang and fall over when computing complex designs. For instance, if I was to model that schooner all in one file I know for sure I would spend many wasted hours waiting for f360 to resolve the designs. There are ways to mitigate this through using a good design methodology, but I wondered how freecad fares in this respect?

 

I’d more or less shelved FDM for resin until a month ago, where I resurrected it to make the decks for my Cutty Sark. I simply couldn’t get reliable joints in resin, take a look at my build log for more details. I plan to make a hull in the foreseeable future and would certainly look to FDM for this as the parts are much stronger. It’s worth mentioning some upgrades I undertook on my ender 3 pro as they made a huge difference. I mostly gave up on FDM because the rate of print failure was so high. So, I recently bought a sunlu filament dryer and use this from the moment I load a reel of PETG filament. It has made a world of difference, I simply don’t get failures now. I also upgraded to a silent motherboard and silent power supply fan. I now have the machine on my office desk and can have that running even when I’m in meetings and you can barely hear it. I also installed auto bed levelling, not sure what if any difference that makes though.

 

 

[Patrick Matthews]

On 4/7/2021 at 8:21 AM, TonyM said:

...Then I sweep the strand cross section along the splines. Very time consuming and I want to find a better way...

 

 

 

 

 

In Fusion 360 (and probably other packages), create a single path for the centerline of your rope. For multiple lines in a block, do just one loop and copy the solid segment rather than doing the entire length.
But with your path, create a single sketch with all the strands. Overlap them a bit and cut away the interior overlaps.
Then sweep that sketch along the path, adding twist. In F360, I have to specify the entire twist amount for the entire length, might be a few thousand degrees.
Here's a printable wire spool for my 1:8 DUKW winch.
 

 

One loop of wire:

 

 

The printed wire reel:

[Patrick Matthews]

Same process used here on my "business card", a one-piece print:
 

Edited February 28, 2022 by Patrick Matthews

[Kevin-the-lubber]

Same here for the rope decor on the vic stern, again in F360. It still drives me up the wall sometimes when it's uncooperative but it does have some very nice features and, of course, a wire rope like this takes a minute or two when you know how and can be finessed/revised later to your hearts content in a few moments.

 

[TonyM]

Really nice work Pat.

 

I am thinking of moving from FreeCad to Fusion 360 which would end my commitment to this topic.

The export functions difficulty was the driving reason. I am exporting in STEP then converting to .GLB to load into Sketchfab. 

There are no texture files but the material comes across with color but not all the rendering parameters such as shininess.

This required a lot of editing in Sketchfab which recognizes material by color only.

 

The Light field device from Looking Glass Factory worked and the .GLB file was loaded into a studio software and 3D views were generated to load into the display device called Portrait. It provides a 3D presentation with parallax and stereoscopic simulation so that the model looks real inside the "case".

 

[Kevin-the-lubber]

Via another thread, where I’ve whinged endlessly about the downsides of F360, I’ve been pointed towards Rhino3D. It’s not free but, as I could access an educational licence, it’s not too expensive and you buy rather than subscribe. (I hate this gravitation towards subscription for everything, but especially software). Apparently it’s the industry standard for shipbuilders and is very, very good. The only reason I haven’t done so is I couldn’t face another huge learning curve right now, but if you’re ready for that you might want to use the free trial opportunity which is good for three months. I’d balance this by saying I still have a lurking suspicion that the problems I encounter in F360 are somehow related to my PC; I built it a couple of years ago and deliberately went down the AMD route rather than Intel, and I think F360 doesn’t like AMD graphics cards. And also that, as I become more experienced in it’s use, I’m better able to avoid problems through better methodology. Otherwise, F360 is excellent.