Drawing a tightening curve between a line and a circle...

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Drawing a tightening curve between a line and a circle...

Paul S
Hi all
I am new to Librecad and I am struggling with something. I have Librecad V 2.1.2.

I am trying to draw a boat in plan view. The sides of the boat are parralel for about 20% of the boats length amidships.

The bow is not a point but in fact an arc of relatively small radius.

I would like to join the straight line amidships (which lies parallel to the vessel centreline) to the bow arc with a curved line which progressively tightens as it travels forward.

Essentially it could be slightly less than a quarter of an ellipse say... But I have played around and I can't make it work without getting lumps and bumps - the line should be fluid from midships to bow.

Any ideas or am I asking too much? I tried Delft ship (paid for Pro) but it is entirely unworkable for accurately reproducing an existing design. Is there a better package for old-school naval architecture? I am trying to do what I did decades ago on a drawing board using splines and ducks.

Thanks in advance
Paul
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Re: Drawing a tightening curve between a line and a circle...

dellus
I am not a specialist on this, but I have experimented a bit. I know what is needed is a feature not available in LibreCAD - Spline with connection angle. Is there a workaround?
Tools - Curve - Spline. Set the first control point at the one end of the straight sides, the second at an enlongation of it, the third at an enlongation of the arc, the fourth at the end of the arc.
When you click on the resulting spline, you will see it marked and the control points shown. You can move them now to influence the spline, but they have to stay on the enlongations (blue in my example) for not to get bumps.
Choose spline degree 2 or 3. I don't know the difference.


Good luck.
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Re: Drawing a tightening curve between a line and a circle...

Paul S
Thank you Dellus
I will play around with this tomorrow now I have something to work with.
Awesome, I can't thank you enough.
Kind regards
Paul