Hull Surface Editing

[Peter Edmonds]

I am still in the early stages of creating hull models. Specifically I am using marker points to generate curves (both longitudinal and transverse in the one set of marker points) fro vessel offset tables, or point offsets lifted from a hull shape.

My specific issue at present is seeking to delete boundary points/boundary edges.

I think what I am looking for is the inverse of edge split, working on a boundary edge. I can’t find this in the menu structure, nor anything in the forum topics Can someone help, please.

My background is that I am a Naval Architect with many years experience on hull shapes, both manual and HULLFORM (Blue Peter Marine), but only limited start-up experience in DELFTship. One objective is to be able to transfer hull shape by IGES file to SolidWorks for onward design, which I have done to a limited extent so far.

Peter Edmonds
Naval Architect
Perth, Western Austyrtalia

[Denis Pratt]

🙁
I’m not sure if I got this right but the inverse of “split an edge” is to “collapse” a point or and curve.
I have recently been introducing internal decks and side shelves into my hull designs and find the best way is to produce a water line, with markers, convert the markers to points, at a low precision or you end up with too many points and use these points to generate a deck either as a face or from an extrusion.
Quite often the number of points on the edge is to many so discrete reduction of the points on the edge curve is necessary by collapsing them.
Hope this helps

[Denis Pratt]

Recently completing a 4.5m planning hull design in DS Pro. The hull plates were un-folded and showed little edge or face stress. The parts were NC cut and the boat started building. Problems appeared at the fore foot area with hull plates not wrapping and sitting well onto the frames. The frames outer edges are too straight and only meet the hull plates at the inner and outer edges.
As part of my investigation of why this occurred, the same data was used to produce a .rep file from my old Aship software.
Loading the rep file back into DS to check the shape gave pretty much the same lines plan of the original DS design.. Fore foot forward frames do not having much curvature against the hull plates.
This is odd, most boats have curved edges in these frames where they meet the hull plates, a basic requirement of developed plates and conic sections. Read Sonny Levi’s book on planing hull designs if you need to understand this.

Anyway, checking further I produced a lines plan in my ancient Aship Gen4 software and sure enough get curved edges at the forward frames to hull intersections.

Overlaying the DS lines to the AS lines, shows the waterlines in DS appear slightly hollow forward and are much different than AS waterlines. The AS shape appear to me to give better water flow compared to the DS shape. My experience tells me the fit of the AS parts would be much better. A plan view of the lines As in blue and DS in red is attached.

Has anyone got an idea on why the DS shape is so different than the AS shape please and how to correct this as a fined DS much better to work with, but the resulting shapes are not to my liking.?

[Marven]

Dear Dennis,

Can you send me the following files so I can investigate the problem:

• The delftship file
• Your AS gen 4 file
• a 3D dxf export of the lines generated by AS

Then I can compare the results, check what happens and get back to you.
You can send the files to info@delftship.net

[Denis Pratt]

The three files were sent to you yesterday. Further investigation still finds “straight” frame outer boundaries even when the control net subdivision is increased. The “developable” view shows mostly green with the plate edges only shown red, this I find is usually the case at longitudinal boundaries.

[Dirk]

Is there any progress on this issue?

[Denis Pratt]

Since my earlier posts on this I have looked more deeply into the develop-ability of this hull.
AS Gen4 allows for a ruling line development, works fine and produces plates which curve normal to the rulings to fit the hull and produces a lines plan from which frames can be extracted with curved outer edges. When gauging what would happen when the hull plates are wrapped on to the frames they appear to fit well.This is hydro-conic development and not development in terms of “nurbs” surfaces.
The latest DS Pro does produce a plates that purport to be developable “within limits”, On the screen, the “developable” image is “green” with only slight red edges to both bottom and side plates and the chine plate is completely “green” . Green suggesting good develop-ability. When unfolded the side plate and the chine plate have approximately zero stresses and the area difference almost zero too.
The bottom plate aft has no real stresses to talk about, but forward the edge and face show stress, less that 10% with an area difference a very low number. This is where I get confused or not seeing things clearly. The plate area difference is easily understood, it would be good if there was some way of judging what the stress percentage numbers mean. I understand the stress in the plate forward means a little forcing into place may be necessary but to what extent would be nice to know.
I still cannot understand why the forward frame bottom edges are not curved more in the lines plan and reflect more clearly where the plats need bending or forcing to shape. It appears more like the frames are generated from approximately straight lines between the keel line and the inner chine edge.
For my next investigation of this I intend to sub-divide the model more and see if this increases the curvature of the frames as they follow the hull plates.

[Denis Pratt]

Guess what? Just installed the latest version of DSpro 7.17.

From the 4.5metre hull design I am studying, used the ASgen4 deck edge, chines and keel line introduced via dxf file marker curves into DSpro 7.17 to see if I could replicate the ASgen4 frame shapes.

Used the new ruling lines method increasing the rulings to 75 per plate and get curved frame boundaries forward where I expected, whoopy!.

There is a blemish to smoothness at the forefoot using the environment map still to check, but very minor. Most probably a mistake I introduced somewhere.

Got to compare a body plan from within DSpro7.17 and overlay on the one produced from ASgen4. Also got to compare the unfolded plates. All looks good for success!!

Good work Delftship Team.

Denis :cheer:

[Marven]

That’s good to hear!

[Denis Pratt]

Getting along fine with the new update DSPro 7.17, except for the crash when I attempt to open the hull display drop down.. If I close al the control icons with the up arrow at the right of the screen and then open the home page again all is fine.

This might be an issue that you may have already fixed.

One thing that I cannot do in surface editing is decrease the subdivision after I have increased it and saved the data. Is there a quick way of reducing the subdivision once the data is saved, other than collapsing lines.
Denis

[Maarten]

Hi Denis,

I hope your issue is fixed with our new release, could you please confirm?

As for your other question, we have added a ‘Remove’ edge button- this will remove selected edges, while trying to minimize the impact on the overall shape.

Regards,
Maarten

[Denis Pratt]

Hi Maarten,

Thanks for the email.

I am still coming to grips with the changes made to DPSPro.

Regarding the comparison between ASgen4 and DSPro on the 4.5metre vessel, the new version of DSPro does give curved bottom edges to the forward frames when ruling lines are used to produce the surfaces. However the curvature on the frame bottoms forward is more pronounced in AS than in DS. I am going over the issue and comparing the processes by ensuring both methods are using the same number of ruling lines and that the four critical curves of keel, inner and outer chine edges and the deck edge are in fact the same in shape and curvature for both processes.

This could take a bit of time to complete. Eventually, it does not mean much until I actually build a boat and check the fit of frames to bottom. This will probably be done at a 10th scale. When I have got the best fit for both DSPro7.17 and ASgen4, I will send you all the information.

The actual hull built from the earlier version DSPro7.14 is complete, The shape around the lower shoulders is slightly wider than intended due I think to the not perfect wrap of bottom onto frames, which then had a knock-on effect elsewhere, but the hull is “eye-able” so of no concern. She is now completely fitted out with a 70hp outboard, being registered today and will be in the water this coming week-end to see how she performs.

Regarding version DSPro 7.17 version 284, I find at start up the three pull downs for Hull display, tank display and Window are closed. If I click the up arrow to the right below all the icons all pages are hidden. On opening the home tab, the new icons shown include the three previous mentioned pull downs. I prefer this arrangement and would prefer not to have to go through that routine at each start-up.

The remove edge button works well in reducing the subdivision size.

Kind regards,

Denis

[Denis Pratt]

Maarten,
Here are some pics of the finished boat with some comments.
Denis

[Denis Pratt]

too many pics

[Denis Pratt]

too many pics before

[Denis Pratt]

only two pics this time

Attachments:

• imag2.jpg
• imag7.jpg

[Terrance Egolf]

Here is the current state of hull modeling my grandfather’s brigantine Galilee, built by Matthew Turner in 1891 in Benicia, California, USA. I am using plans provided by the HAMMS project archived in the Smithsonian Institute. My project involves revising the stern/transom to conform to photos of the ship as she was in 1906-1908 in DELFTship, exporting the lines view, and developing framing plans for the model.

Does anyone have suggestions for constructing the DELFTship control net to aid in smoothing out the slight irregularities in the hull? The hull in this view looks reasonable (except for the rail line), but the Curvature view shows lots of blotches where the various curves aren’t continuous.

Thanks

Terry E.
Greenville, SC, USA

[Denis Pratt]

Further to my last few posts, I accidentally input dxf file import of the basic marker curves in millimetres not metres. In delftship the program assumes we are still in metres therefore the hull was 1000 times bigger than should be, OOPs.
Checking both sets of un-folded plates scale sizes, the stress levels are the same and the percentage area changes are similar, just as expected.
Looking at the developed surface image to see the “red” areas depicting less develop-ability of the surface of the larger scale vessel has no red areas. When scaling down by a factor of 0.001 to bring the vessel size to actual, red blotches on the develop-ability view re-appear.
It seems that size alters the develop-ability image, one has to be careful when checking develop-ability and not rely on just the image view.

Still have some problems to solve where the bottom plate ends at the bow with only three points for the final face panel, but will solve this somehow. Perhaps have to input an extra control point close to the most forward bottom plate point to make the panel a four point panel.

[Denis Pratt]

Hi to all that are following my stumbling work,

Regarding my recent posts, further research finds a different set of rulings in my very old program ASGen4 to the latest DSPro which as yet I cannot understand.

Just today I have downloaded the centreline, inner and outer chine lines and deck edge of an existing design from 2004 from which I built two 8 metre hulls, which constructed very easiliy and performed extremely well. Importing as markers the edges and developing ruling line surfaces of the three longitudinal hull panels was simple. From the results I compared the lines and stations of the original built hull with those of DSpro, big differences, were evident. The new ruling lines follow completely different paths to the old ones and the frames are differently curved between keel line and inner chine line at the forward shoulder positions.

It is most probably due to a different mathematical interpretation of the longitudinal curves, but I still need to look at this aspect.
I shall have to look further into the type of polynomials used as mathematical interpretation of the curves used as it is most probably due to this aspect that the differences occur/.

Regards,

Denis

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