Fletcher Gun Tubs and Mark 49 Director

[aptivaboy]

I'll probably put two types in the model the solid bulwark and maybe the rails covered by canvas. The modeler could choose which one for themselves. I think MOI can distort the surface to replicate clothing, I think.

Shapeways says the Hughes deckhouse has shipped! Soon, it will be in my greedy hands, soon!

[MatthewB]

I'll probably put two types in the model the solid bulwark and maybe the rails covered by canvas. The modeler could choose which one for themselves. I think MOI can distort the surface to replicate clothing, I think.

Shapeways says the Hughes deckhouse has shipped! Soon, it will be in my greedy hands, soon!

It should be able to do so.

If not, I know of something that can.

But... I need to know:

Can you import an .obj into MOI, and can it convert polygon models to solid/surface/nurbs?

If it can't, then I can.

But... My suggestion would be to send me the model (as an .obj), and I can convert it to Polygons, and then use Mudbox or ZBrush
to sculpt in the cloth surface, and then export it as an .obj that can then be imported back into MOI.

Alternatively, if you leave the sculpting to the last thing, I can sculpt the cloth in, and then export it as an .stl and send it back to you.

MB

[aptivaboy]

Thanks for the offer but I can't import/export OBJs into MOI. I usually import IGS files from Geomagic into MOI. Its a superb program, but a little bit limiting in terms of import and export options. Then again, that's what makes it so robust and inexpensive. Anyway, I think I figured out how to make it work, but thank you again. I may not even attempt to distress the "canvas" since they would have been tied really tight and taut. Its probably that dimples and fabric deformations wouldn't be there, or else wouldn't be visible in the scales were dealing with.

Here's a rough draft of the repositioned clips with small mounting brackets on them. Thoughts? Too simplistic? I was able to get the clips to remain by exporting to Geomagic as a STEP file.




Bob

[MatthewB]

Just as a suggestion.

You might want to think about getting something like ViaCAD.

Or, if you can spend about twice what ViaCAD costs (it is $99 standard, but Smith Micro offers sales All the time - just go subscribe to their notices at smith micro.com), you can get a yearly subscription to AutoCAD (the full deal) for $265 for PC/$210 for Mac (Autodesk began transitioning from PC to Mac as their primary platform a few years ago, so the prices are cheaper).

I can guarantee you that the increase in power, and the height of the learning curve (with the support from Autodesk) will be VASTLY more worth it than MOI.

The control of object snaps alone in Autodesk speeds up your work at least twice as fast as most lower-end products that do not have the controls that are in Autodesk products.

But, even if you cannot afford an AutoCAD subscription, I would get ViaCAD, as it is as far ahead of MOI as is AutoCAD from ViaCAD.

And the ability to transition between different model types (polygon mesh, Parametric Solids, NURBs, etc.... AutoCAD has several I have never even used, and probably should learn) gives you the ability to create things that would otherwise stump you in another package. The only package I have seen come close to AutoCAD is Solidworks, but only for parametric solid modeling.

And the ability to import/export ANY format will make your life easier as well.

And this isn't just because of the cloth...

Oh!

And I discovered how to get Shapeways to alter their print-orientation. It sometimes requires modeling supports into the model for overhanging parts of a model, but the guys as ViaCAD told me that Shapeways only prints in a specific orientation as the file is delivered.

So, if you wish different print orientations, you need to do separate files for each orientation. I will need to check the deviation from file to print-bed that they gave me. But it is possible. You just need to list each orientation as a separate product.

MB

[aptivaboy]

Money. I'm poor, which is the reason I use MOI so much. Its cheap and surprisingly powerful. You can even add your own scripts to it! I know, other programs can do this too, but MOI is unique in that the designer (one of the original Rhino founders and designers) actually answers your questions on the forum. Today, I learned how to add an "Export to JPEG" script. Cool!

MOI is also one of the best programs out there to use for organic shapes. Its a favorite amongst jewelry designers and concept art folks to do the basic shapes and work before porting over to more advanced programs for surface detailing. I use it for my Trek hulls almost exclusively.

Anyway, here's the director tub in MOI. There is a 1mm hole on the inside for mounting the builder's director of choice. This is the totally plain version. I'm working on one right now with pipe rails in the interior.

Bob

[aptivaboy]

Director tub with internal pipe rails and sheet metal splinter shielding. This took less than 3 minutes in MOI, its that simple and intuitive once you get the workflow down. Coming from a parametric background, the learning curve was steep but once I figured it out, wow is it powerful and quick.

[aptivaboy]

Some tests - the director tub installed. Thoughts? Methinks the director tub may be slightly too tall, although they certainly varied from ship to ship.

[aptivaboy]

Variant with the director tub hanging past the tail end of the main gun tub.

[MatthewB]

Excellent work.

MB

[Rick E Davis]

Ahhh ... is it just the way my image gets displayed or are you way off in how the director base interfaces with the "tub"???

The bottom of the director base should be at the same level as the tub floor. The Mk 51 director platform should be at or a little higher that the top of the bulwark around the "tub". The director base was pretty much hollow. To save print material that would be the best way to go. The hollowed out area can go through the tub base and a hole similar to the one for the twin 40-mm mount left in the top of the director base/platform.

The actual Tub-Director base interface, shown here with a Mk 49 director, would look like this;

Below is a profile view of a unit with a Mk 51 director without a bulwark around it or showing the railings commonly used late in the war.

The platform that the Mk 51 director was mounted to was mounted to the top of the base (where the Mk 49 director would have been).

Do you get what I'm saying???

[aptivaboy]

Better?



Some pics seem to show a simple cylinder, others the way I have it, a slightly larger cylinder atop a slightly smaller cylinder. Is there a preference either way?

Bob

[Rick E Davis]

Are the tub and director base separate pieces or all one integral part?

Why is the base protruding below the tub??

[aptivaboy]

They can be either. They can each be altered in height, moved up or down, locked/joined, etc.

The base is protruding below the tub for positioning purposes to ensure a seamless join between the base and the tub's deck. It will be deleted once the design is finalized to create a perfectly flat tub underside.

Bob

[aptivaboy]

A slight alteration of the director tub.



A resize of the director tub. Even though it looks right as per the plans dimensionally, it looks wrong to my eyes so I reduced it in size.

[Rick E Davis]

OK. Better, I'm not use to CAD drawings in the "RAW".

I use to be a draftsman some 40-years ago ... with old-fashion paper and pencil.

What will the final lengthwise cross-section through the part look like when done? I envision a "bottomless barrel" with a "opened top tub" on top for the director base.

[aptivaboy]

Right now, there's a mounting hole about 1mm in diameter for the director. I imagine the director having a 1mm thick cylindrical post which will fit in there.



By the way, do you have any rough dimensions for the Mark 49? All I really need is width and height; I can freelance the rest.


Bob

[aptivaboy]

PS. A little more on painting. I've come across some references to people having trouble in general getting enamels to properly cure on printed parts. I've never had that issue, assuming the parts were properly cleaned, but some others on the interweb are recommending using water base acrylics only. Just thought I'd pass it on.

My best advice is to clean the parts, and then test out enamels if you're going to use them on a scrap or interior piece to ensure they cure and adhere properly. If you have concerns, then consider using acrylics. I might also paint the interior of the deckhouse to create a nice light stopping surface so you don't have to overpaint the exterior to cover up the shinyness of the nearly clear part.

Bob

[Rick E Davis]

I keep forgetting to say this. I would suggest that the parts of this thread dealing with the FLETCHER class "Tear-Drop" tub should be broken-out in their own thread. Otherwise no one else is going to know about what you are doing.

The Mk 49 dimensions are hard to come by. After the USN cancelled the project in October 1943, they appear to have DUMPED the records in the trashcan. Attached is a drawing I found providing the "Foundation Ring" for the Mk 49. It shows that the pedestal base (and by the way this would be about the diameter of the director base ... the BIW drawings provide the inside radius as being 2-ft, 7.5-in) has an outside radius of 2-ft, 9-in for a diameter of 5-ft, 6-in. The operator station inside was more or less a "ball" that could tilt up and down and rotate side to side. I assume, it almost has to be, a spherical radius of about 2-ft, 6-in to allow it to sit inside this pedestal. What I don't know is the height of the pedestal. I have not found construction drawings for the Mk 49. But from these "Manual Photos" I have done a cheap and dirty scaling. Since the diameter is pretty firm at 5.5-ft and the photo ratio of the height to diameter is around 75%, the height from the bottom of the pedestal base to the top of the cylinder is right around 4-ft. to no more than 4.5-ft. The photos seem to show this to be about right. On some installations a 18-in riser was added to the bottom of the Mk 49 director to get it higher, but that isn't the case here. We won't get into the directors that actually "got" the radars intended for these mounts, there weren't that many and they get complicated ... and I have NO dimensions for them. If you decide to make the Mk 49 directors, a bag of three would be about right. Many of the FLETCHERS with Mk 49 directors had three of them.

I had completely forgotten about BIW drawings showing the Mk 51 installation atop the Mk 49 foundation. Below are the views of the Mk 51 installation.

This drawing shows that the foundation for the Mk 49 is 3-ft, 4 11/16-in tall. About the same height as the bulwark shield around the tub.

Finally, here is a pretty good view of USS FULLAM (DD-474) showing her Mk 49 director installation from the forward aspect. Also this shows where/how they cut off that section of the tub bulwark forward of the director as being unnecessary. Plus another view of the Mk 49 director installation onboard USS WALKER (DD-517) before the forward section of the bulwark was cut-off. The sailor standing on the bulwark rim gives an overall height.

[MatthewB]

Re: Paints on printed parts.

Enamels will work.

But:

1) Clean the part.
2) Prime it with a decent primer. The Primer should be a smooth finish, with just a bit of tooth (not completely smooth, as I have seen some people prime. This means multiple coats of primer, with the can between 6" and 8" from the model)
3) Sanding the primer with 1000 grit sandpaper will help as well (some parts cannot be sanded easily due to their shape. The inside of the tub comes to mind. But the sanding is not necessary if you have the primer applied correctly).
4) Apply a light wash of the base-color over the part first and allow it to dry/cure for a few days.
5) Then apply the color in a typical set of two light coats to get even coverage.

Above all else, I am a miniature painter, which is what I have done longer than anything else in my life, and painting was among the things I studied the first time I went to college (in the 1980s - I was studying Fine Arts as a rebellion against my Father).

So when 3D printed parts first started to appear about 10 years ago (not to the general public, but among a few miniature and model makers - I was lucky to be employed by a company that had a decent Stereolithography at the time; they now have all manner of printers and CAD/CAM mills), painting them was something we discovered could be tricky, due to the strange nature of the materials (some 3D parts can't be painted with anything - such as the SLA or Wax printed parts. You wouldn't want to paint one of them anyway - but we discovered that many Deposition Plastics tended to have a greasy finish, and the volatiles in the plastics would leech for months - to years - afterwards, causing paints to flake or slough off).

One other issue.

In the drawings above, the gun director looks like its radius/diameter is smaller than the base upon which it rests (one is shown without the cover, and obviously is smaller in radius).

Yet the 3D model shows the director base being narrower than the director.... At least if I do not have the parts confused (which is a possibility).

Not exactly something that is a huge issue. But if this is the case, then it would be easy to fix.

MB

[aptivaboy]

Taking Mr. Davis' suggestion, I'll be putting any new CAD work on these parts here in their own thread so as to not clog up the Sims thread.

Simple drawings...