How to control entrance or run angles of curves (i.e. 1st derivative of splines at its endpoints)?

[Ralph Grothe]

Hello DS lofting community,

I am an absolute newbie to DS and digital lines lofting (though I have done it a few times by manual drafting).

I have a problem that I don’t know how to control the slope or angle of the tangent of splines at its endpoints.

E.g. I have started with below reconstruction of hull lines of MV Sovereign of the Seas from a tiny General Arrangement Plan (A4 Size) which I loaded as far as stem and stern contours and deck lines were concerned as background images.

As a first draft (still pretty unfair and requires a lot of smoothing) I ended up with attached body plan which superficially doesn’t look too bad.
However, if I zoom in within the waterlines view I don’t know how to make the splines of the bulb intersect CL at a right angle (viz. infinite slope) to produce a nice round bulb.

Also I don’t know what causes the oscillation of the spline of the bulb section at FP (i.e. section 20)?
I rather would give it a shape (smoother of course) of what I scribbled in a green line on the attached pic.

Regards
Ralph

P.S. Oops, where are the sample pics that I attached to this posting?

Attachments:

• bodyplan_sample.jpg
• WL_entrance_bulb.jpg
• oscillating_bulb_section.jpg

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