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Re: S&G: Plate development *PIC*
By:Hubert Schreier
Date: 12/13/2016, 4:00 am
In Response To: Re: S&G: Plate development *PIC* (Hubert Schreier)

I have made a little bit of progress and wrote a new ruling line computation program that optimizes a monotonic B-spline which maps the parameter space from one Bezier curve to the other. This program always finds a smooth ruling, even if the shape is not developable and I can look at the twist to see how close to developable the shape is. I have also incorporated penalty functions to trade twist for reduced curvature. This works pretty well as long as the stems are not too steep, but I still have not been able to create a nicely developable shape with plumb stems. I either have a lot of twist (8-12 degrees) or a lot of curvature in the cross sections.

I got curious to see what other programs are available and found a linux version of FreeShip. So, I created a file with 100 data points each for keel, chine and sheer from Bezier curves I had fitted to the Sea Tour 15 offsets. I imported this into FreeShip and generated panel developments. I compared the generated panels to a panel development I had made with my software from the Bezier curves with straight cross sections. I roughly aligned the two panels and plotted them in the attached figure. The two plots show the same data, the top plot has an exaggerated y-scale. This is the panel between keel and chine. FreeShip reports zero edge error and an area error on the order of 3e-3 (units unknown, could not find much information in the manual).

As you can see in the plot, the FreeShip development has a much more concave keel at the stems than the straight line ruling. I got curious and figured out how to show cross sections in FreeShip, and sure enough they are concave at the ends. I am not sure what to make of it, but I cannot imagine getting the concave keel line to be convex after assembly. It looks like the keel has to be pushed up by about 40mm over a distance of 0.5m in an area where the panel is already pretty vertical. There are some free S&G plans on the internet that I have looked at, and some have a concave keel near the stems, but nothing as dramatic as the FreeShip panel shown in the plot.

The problem shown in the plot gets worse if I use plumb stems. I either get cross sections that deviate from a straight line by more than half an inch, or I get a lot of twist resulting in the concave keel line. The only way around that I have found is to use an extra chine that is level with the keel near the ends. This results in nicely developable panels unless I pinch the ends of the bottom chine too much.


Messages In This Thread

S&G: Plate development
Hubert Schreier -- 12/3/2016, 4:10 pm
Re: S&G: Plate development
upchurchmr -- 12/3/2016, 4:38 pm
Re: S&G: Plate development
Hubert Schreier -- 12/3/2016, 4:55 pm
Re: S&G: Plate development
upchurchmr -- 12/3/2016, 5:45 pm
Re: S&G: Plate development
Nick Schade - Guillemot Kayaks -- 12/3/2016, 10:14 pm
Re: S&G: Plate development
Hubert Schreier -- 12/4/2016, 12:57 am
Re: S&G: Plate development
upchurchmr -- 12/4/2016, 3:37 am
Re: S&G: Plate development
Hubert Schreier -- 12/4/2016, 11:45 pm
Re: S&G: Plate development
Alex Ferguson -- 12/5/2016, 3:38 pm
Re: S&G: Plate development
upchurchmr -- 12/5/2016, 5:42 pm
Re: S&G: Plate development
Hubert Schreier -- 12/5/2016, 9:23 pm
Re: S&G: Plate development
Alex Ferguson -- 12/5/2016, 9:55 pm
Re: S&G: Plate development
Hubert Schreier -- 12/6/2016, 12:34 am
Re: S&G: Plate development
Nick Schade - Guillemot Kayaks -- 12/4/2016, 8:20 am
Re: S&G: Plate development *PIC*
Hubert Schreier -- 12/5/2016, 10:23 pm
Re: S&G: Plate development
Bill Hamm -- 12/6/2016, 12:56 am
Re: S&G: Plate development
Hubert Schreier -- 12/6/2016, 1:03 am
Re: S&G: Plate development
Bill Hamm -- 12/6/2016, 1:09 am
Re: S&G: Plate development
Hubert Schreier -- 12/6/2016, 1:20 am
Re: S&G: Plate development
Mike Bielski -- 12/6/2016, 1:09 pm
Re: S&G: Plate development *PIC*
Hubert Schreier -- 12/6/2016, 3:07 pm
Re: S&G: Plate development
Mike Bielski -- 12/6/2016, 4:35 pm
Re: S&G: Plate development
upchurchmr -- 12/6/2016, 7:14 am
Re: S&G: Plate development
Hubert Schreier -- 12/6/2016, 8:45 am
Re: S&G: Plate development
Nick Schade - Guillemot Kayaks -- 12/6/2016, 8:49 am
Re: S&G: Plate development
Hubert Schreier -- 12/6/2016, 10:04 am
Re: S&G: Plate development
upchurchmr -- 12/6/2016, 11:04 am
Re: S&G: Plate development *PIC*
Nick Schade - Guillemot Kayaks -- 12/6/2016, 7:29 pm
Re: S&G: Plate development
Hubert Schreier -- 12/6/2016, 8:26 pm
Re: S&G: Plate development *PIC*
Hubert Schreier -- 12/7/2016, 12:27 am
Re: S&G: Plate development
Nick Schade - Guillemot Kayaks -- 12/7/2016, 7:45 am
Re: S&G: Plate development
upchurchmr -- 12/7/2016, 9:29 am
Re: S&G: Plate development
Nick Schade - Guillemot Kayaks -- 12/7/2016, 10:21 am
Re: S&G: Plate development
upchurchmr -- 12/7/2016, 12:43 pm
Re: S&G: Plate development *PIC*
Hubert Schreier -- 12/13/2016, 4:00 am
Re: S&G: Plate development *PIC*
Nick Schade - Guillemot Kayaks -- 12/13/2016, 6:54 pm
Re: S&G: Plate development
Hubert Schreier -- 12/13/2016, 8:03 pm
Re: S&G: Plate development *PIC*
Nick Schade - Guillemot Kayaks -- 12/13/2016, 11:10 pm
Re: S&G: Plate development
Hubert Schreier -- 12/30/2016, 6:08 pm
Re: S&G: Plate development *PIC*
Dan Caouette (CSCWC) -- 12/14/2016, 6:55 am
Delftship
Nick Schade - Guillemot Kayaks -- 12/14/2016, 8:50 am
Re: Delftship *PIC*
Dan Caouette (CSCWC) -- 12/14/2016, 11:57 am
Re: Delftship
Nick Schade - Guillemot Kayaks -- 1/25/2017, 9:41 am
Re: Delftship
Dan Caouette (CSCWC) -- 1/25/2017, 6:19 pm
Re: S&G: Plate development
Hubert Schreier -- 12/30/2016, 5:53 pm
Re: S&G: Plate development
Dan Caouette (CSCWC) -- 12/31/2016, 8:57 am
Find "MultiConic Dev of Hull Surfaces"
mick allen -- 12/5/2016, 8:16 pm
Re: Find "MultiConic Dev of Hull Surfaces"
Hubert Schreier -- 12/5/2016, 11:07 pm