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Just installed the latest free version of DELFTship (v. 13.10 (324)). It appears that there are a lot of improvements. Most obvious to the familiar user are revisions to the menu tabs. However, if you dig into the settings, the user now has the option of creating models in centimeters and inches as well as the standard meters and feet. You can also set the decimal precision, which is really handy, since the default was four decimal places.

 

This update may be of interest to modelers, who can now create their digital models in the actual dimensions they will build in. [Edit 2/11/2021: Clarified the nature of the dimensioning changes, now that I understand them better!] Former versions had two dimensional unit choices, Metric (meters) and Imperial (feet). If you created a model in one set of dimensions, then changed them to the other, the model would scale in size up or down depending on the direction of the change because the number of units remained the same. Fore example, if you created a 100-foot vessel mistakenly in meters, then changed to feet, the model would downsize to 100 feet. Now, that is OK if you did make the original error in selecting dimensions. However, if you simply wanted to switch dimensions, to understand the size in the other dimension system, that was a problem. With the latest version, you can switch freely among all four dimensional units without any change in the actual size of the model. I found this useful when working on small details in my Galilee model, where creating things in inches was more appropriate than in feet. Scaling down the hull to model-size is easily performed using the program's Scale feature.

 

There is also a new manual that goes with this version, but I haven't looked at it yet.

 

Terry

 

 

Edited by CDR_Ret
Clarifying the new DELFTship dimensions option.
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  • 2 weeks later...
  • 2 weeks later...
On 1/27/2021 at 10:25 AM, Sailor1234567890 said:

Do you know if Delftship models things like mass, weight, shape etc. to be really useful as a naval architecture program or is it a simple CAD shapes and you have to figure out weight yourself? 

Even in the Free version, there are basic hydrostatic functions available. I haven't tried the more complex ones that involve displacements, material thickness and water density, etc. Those don't usually pertain to a modeler. Back-yard boat builders—yes.

 

Terry

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A Guide to the New DELFTship Background Images Feature

 

Attached are the five parts of a guide I have drafted up to assist modelers who think they want to get their feet wet using DELFTship. It is intended for the complete DELFTship novice, but even those familiar with the program will find this guide useful, I think.

 

Please read Part 1, which includes an intellectual property disclaimer.

 

If you have any comments or corrections, please feel free to post them here so everyone can be aware of them (and I can fix them). I am particularly interested in fixing things that are unclear or don't work as intended.

 

Be sure to install the latest version of DELFTship (13.10 (328 or later)) before you use this guide. It's almost completely incompatible with earlier versions!

 

Thanks.

 

Terry

Part 1-DELFTship_Bkgrd_Images.pdf Part 2-DELFTship_Bkgrd_Images.pdf Part 3-DELFTship_Bkgrd_Images.pdf Part 4-DELFTship_Bkgrd_Images.pdf Part 5-DELFTship_Bkgrd_Images.pdf

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Just for fun, I thought I'd try out whipping out a Sturgeon-class SSN hull using the new background image feature in DELFTship. Setup was really quick. Shaping the hull was another story...

 

image.png.851f80dae8090de41fb70c68a45b097e.png

Plan: USS Sturgeon (SSN 637) by Greg Sharpe 

 

Being an old submariner, I may spend a little time on this!

 

Terry

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Probably the most difficult aspect of a Cold-War-era submarine model is getting the propeller right. Nearly all nations with advanced submarines came to recognize the acoustic advantages of a seven-bladed, minimum cavitation propeller. The blade shapes are extremely complex, requiring the use of a sophisticated, multi-axis, computerized milling machine.

 

I have attempted to approximate a submarine propeller in a variety of 3D CAD programs including Sketchup, Blender, and now DELFTship. None of them are easy to use. There is nothing symmetrical about a propeller, except in rotational symmetry. Even then, one has to get the proper blade shape before you can duplicate and rotate the blades to their proper positions. The blades are 51.429 degrees apart (360° ÷ 7). If you are inclined to create a 3D printable model, then you have to cleanly combine the blades with the hub to make the model manifold. That was the hard part.

 

The following images provide a fairly good approximation of a US nuclear submarine propeller before the advent of the ducted pump-jet types found in the Seawolf- and Virginia-class submarines. This model was created in the latest version of DELFTship. In the process, I discovered several program bugs/properties that made the work even more difficult than it should have been ...

 

Propeller-3.jpg.2efa23032cccd553712f4f3ad8532a37.jpg

Orthogonal stern view

 

Propeller-2.jpg.69ea9042b39e5c09bfc6335f3163e10f.jpg

Aft stbd quarter view

 

Propeller-4.thumb.jpg.1d29232a72659c70c69163b32e9c70bd.jpg

Aft port quarter view

 

Terry

 

 

Edited by CDR_Ret
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Nice work Terry,

I can't imagine how hard it would be to create a 7 bladed scimitar shaped screw like that. The boats I sailed in (Victoria class) have a similar screw and looking up at it in dock while "sputtifying" (SPUT stands for skimmer puke under training in our navy) I couldn't wrap my head around the design work that goes into them. 

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We don't (er, didn't—it's been nearly 30 years since I retired; perhaps the US Navy is today a more kinder, tolerant culture...) use that particular acronym, but we still considered surface sailors as "skimmer pukes!"

 

In the early days of submarines, it was a typical career path for surface sailors to transition to the conventional submarine force. For the US Navy today, all our boats are nuclear, and virtually all submarine officers and enlisted must complete the nuclear propulsion training pipeline and/or sub school before ever stepping on board any ship.

 

This YouTube video is the basic idea on how a multi-axis milling machine does a propeller.

 

Terry

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I'm working on an early 17th century ship, and have a really naïve question that will clearly show I've never used Delfthsip before:

 

Delftship asks you to input the length. What length? The length of the keel? The length that corresponds to the distance from the foremost station to the aftmost station? Some other length?

 

Thanks!!!!

 

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Anaxamander49:

 

The short answer to your question is, the reference length is whatever works best for the plans you are using. If your plans show the perpendiculars, those would be best, since that is what the program references in its viewports ("AP" and "FP"). The numerical hull length is critical mainly for hydrostatics calculations the program can perform, which generally aren't of concern for modelers of historical vessels.

 

The program works best for creating building plans if you are using the moulded surface of the hull, not the outer planked surface. For this reason you wouldn't want to use the overall length of the hull for the model's length. I found that anchoring your plans to the underside of the rail, and the inner rabbet lines along the stem, keel, and sternpost works best for starting the hull form. All the other details can be added later, if desired.

 

I would recommend you download the free manual (Manual_13_mc0.pdf) from the DELFTship website, if you haven't already done so, and read through the the first three sections (Interface, Settings and Preferences, and Hull Modeling) to become oriented to the software. The manual is adequate for getting started but isn't comprehensive. It describes more what the program does rather than how or why. And it is definitely lacking in processes and pitfalls.

 

Please feel free to PM me or the others here who have worked with DELFTship if you have any questions.

 

Terry

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  • 3 weeks later...

Taking a break from editing the final drafts of the transcriptions of my grandfather's diaries.

 

Added the Sturgeon's stern planes and control surfaces. Started using some of DELFTship's useful tools, like the Mirror tool. This way, you only have to create one-fourth of the complicated curvy surfaces, such as the vertical stabilizers. Then you can mirror the part across the vertical longitudinal plane and the horizontal plane. Only a quarter of the work!

 

Stern_Planes.jpg.e3ad9a9a8dc5531931898a8c35bb05b6.jpg

 

Those vertical slabs really weren't stabilizers. They were originally intended to house the aftermost set of PUFFS (Passive Underwater Fire Control Feasibility System) sonar arrays. That idea fell through for this class, only to be resurrected in a more sophisticated form with later classes of submarines. I think an engineer finally figured out that having a passive sonar array so close to the propeller probably wasn't going to work. Every ship of the class had these housings, though.

 

Here is a view showing the control surfaces. Several popular hull plans of this submarine class floating around on the Web show the hinge of the planes at an angle to the centerline of the hull. That simply wouldn't work. The planes have to hinge on a line perpendicular to the hull centerline. There was only a single huge hydraulic bellcrank to rotate them. They acted together, not like aircraft ailerons.

 

637-Class.jpg.0a2b68f093f3f3741065400a722b2a4e.jpg

 

Next will be the upper and lower rudders—when the opportunity presents itself.

 

Terry

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Yeah, I've heard these stories even back when I was still in the Navy. The circumstances change every time I hear it. The one that was popular back then was that President Clinton had authorized the sale of a poly-axis propeller milling machine to the Chinese even though it was on the strategic items restricted list (or whatever it was called).

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