John Owles

[John Owles]

Thank you for your reply Maarten,

I would gladly send you the offending dxf file but it is 1.6mb, which is too big for this. Is there an email  address I could send to.

John

[John Owles]

Sorry about the delay, life gets in the way sometimes.

I’ve found the problem at my end. I was looking at an old version model. I hadn’t noticed the nwe “Coordinate system” tab in project settings. Went in, checked and adjusted so that everything is compatible. All functioning corectly now.

Thanks

[John Owles]

No takers?

Today’s export to 2d Curves resulted in two stations behaving normally and a third showing the right way up but moving a construction line up by 1″ resulted in the line moving down 1″!?

[John Owles]

Hello Fernando,

As above, better late than never.

I suggest using Export 2d Curves to dxf. This will give you all the curves in the Lines plan, separated out. You can, as you suggest, use these to form your building jig.

I attach a screen shot of the stations and centreline profile, for the first boat that I built from working with Delftship, that I had printed on a roll. I then glued them onto mdf and set them up according to the station spacing. I also attach an image of the finished boat for your interest.

I now produce a more sophisticated jig for my builds, using the same process, that is CNC cut.

I hope this helps

John

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[John Owles]

Thanks Marven, I am not sure that I understand exactly what skinning is or how to go about preparing for the import surface feature but I am willing to have a look at the idea.

It is a shame when old tech cannot be dovetailed into new tech. It is one of my constant bugbears of the can’t do of modern technology. When tackling some complex piece of engineering from 60 to a hundred years ago, that I am trying to outsource, I am often confronted by  “you do realise Sir, that what was possible back then is quite impossible to do nowadays!”.  I find that I have been under the misapprehension that it was supposed to be the other way round.

Hey ho, back to the drawing board. Yes I do still have one.

[John Owles]

From the silence, do I take it that you don’t think my suggestion will work?

• This reply was modified 3 years, 5 months ago by John Owles. Reason: typo

[John Owles]

Hello Maarten,

I have been away for a couple of weeks and have only just been able to return to this problem of importing a table of offsets and I now think that I may have the answer.

I have imported the table of offsets, for the Airborne Lifeboat project that I am currently engaged with, into DS and it has made a very reasonable fist of the process, as far as the topsides are concerned. Unfortunately, DS has ignored everything below the waterline entirely.

As I have said, ‘old school’ lofting is a part of my day job and I beg to differ slightly with your assertion that “The problem with a table of offsets is that it contains only a limited number of points, the intersection points of stations and waterlines. For the mid ship area this is mostly just fine, but for the (curved) ends of the vessel it means a lot of information required to build a 3d model is missing, such as where a station (or water line) ends at the stem or keel for example. Traditionally this information was filled in by the loftsman who recreated the linesplan on the lofting floor. This lack of information can sometimes be fixed by adding more stations/waterlines.”

This is correct as far as it goes but you failed to consider the buttock co-ordinates, without which the loftsman would, in many cases, struggle to obtain the correct underwater shape of a vessel. Even in the days of working from half models, they often used two models. One sliced horizontally at the waterlines and another sliced vertically at the buttock lines.

Thus a true table of offsets contains the intersection of points from stations, waterlines, buttocks and diagonals. The diagonals are a final checksum for ultimate accuracy and, for the purpose of this exercise, I don’t think we need concern ourselves with these.

However, I do think that the problem that DS has interpreting a table of offsets below the waterline, is the lack of buttock lines. Would it be an idea to include buttock lines into the import routine? It may make all the difference.

I have attached the DS result file 43588, along with the Table of Offsets and a jpg image of the original lines plan that I am working from.

Best regards

John

ABL-MkII_Offsets-DS

ABL-MkII_Offsets-to-DS

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[John Owles]

Hi Maarten,

Thank you for your reply. Lofting is part, from time to time, part of my day job. Particularly for the restoration or re-build of old vessels. In fact I have just lofted a 30ft WWII airborne lifeboat, which was slung under a Lancaster bomber and dropped by parachute to rescue downed airmen off the Dutch Coast or Biscay, etc.

Lofting from a table of offsets drawn up by a designer of the caliber of Uffa Fox is very easy and straight forward but I do take your point.

Perhaps the answer is to take a look at the problem from another angle. Perhaps starting with an original table of offsets and working towards the software coding.

I shall think on the problem, using the ABL as an example, and, if you don’t mind, let you know if I think there is some kind of solution.

I tend to be like a dog with a bone, I’ll whittle around a problem with the feeling that there is no such thing as can’t, just how.

John

[John Owles]

Thank you Maarten,

I’ll try uploading the examples again. I hope they are helpful.

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[John Owles]

It seems that fbm files are not allowed, which is a bit tricky when they are crucial to the current excersize.

I see another post which said that fbm file were allowable. Did that go wrong?

Please let me know how to upload my example fbm files

[John Owles]

From time to time I have a go with offsets as I could really use software that can read them.

So far I have had no joy.

I tried again today by loading up the attached model “14 footer.fbm”, exporting a table of offsets, “14 footer.txt”, and then importing the resulting table of offsets into to a new blank poject. The result was, again, not good, as can be seen in “14 footer from offsets.fbm”

The attached files may assist with debugging.

Here’s hoping. I am very much looking forward to the day when DS is able to work with offsets.

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[John Owles]

The first line of inputs definately define the centre of rotation, with coordinates being relative to the origin (0,0,0).

The second line of inputs seem to define the direction of rotation along an x, y or z axis.
(1,0,0) would rotate along the x axis by n degrees
(0,1,0) would rotate along the y axis by n degrees

I haven’t tried yet but maybe a 45 degree direction of rotation along a combination of x and y would be (1,1,0).

It will be interesting to see whether the direction of rotation can be fine tuned using inputs of o.5 or 1.5 etc.

I need time to play!

[John Owles]

It seems not. At least not through the Model Database access through Delftship anyway. See screen shot.

I don’t see anything in the Forum either.

Attachments:

• ModelDataBase-Select.jpg

[John Owles]

Some progress.
It seems that the axis input defines rotation along the given axis, rather than rotaing around the axis. If that makes sense

[John Owles]

I came to the same conclusion that the first coordinated indicate the location and the second define the axis of the rotation.

So far, regardless of various combinations of axis input, the rotation is always anticlockwise athwartships!

I am thinking that either I am not getting it or there is a problem somewhere that requires advice from Mission Control.

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