Dumas 1:20 scale PT Boat Upgrades

Looking for upgrade weapons for your Dumas PT-109 kit? The 48 inch-long 1:20 scale model? Something more than wood dowels for machine guns? And you’re bummed that neither HR Products nor Mosquito Boat Hobbies’ aftermarket offerings are available anymore?

Well, I have a number of detailed weapons available as 3D-printed kits at Shapeways, in my Matthews Model Marine shop:

Each has a detailed instruction document, available to download from my store.

The weapons are also available in 1:24 and 1:16 scale, and can be further scaled up and down as required… except, I usually can’t offer 1:48 or 1:35 and smaller, as many details on these models are already at their smallest printable size in 1:24.

The material used for most of these parts is Shapeways’ “Frosted Detail”, which is a UV-cured acrylic plastic. Please see my document Working with Shapeways’ “Frosted Detail”, posted at my Shapeways shop.



Breech door assembly for Mk 18 torpedo tube.


50 caliber Browning machine gun sets, available with ammo belts.


Cowl vent hoods… make the rest of the vent with tubing, easy.


20mm Oerlikon, also available on the new lighter tripod mount.


The famous 37mm cannon liberated from Army P-39 fighters.


40mm Bofors single

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40mm Bofors Mount Now Available


Designed in CAD for you.

I’ve teased some photos below of a large scale Bofors 40mm cannon I’ve been working on. It is now available at Shapeways as a kit in 1:16, 1:20, and 1:24 scales. (Please don’t wait around for offerings in 1:35 or 1:48, the model as designed won’t go that small).

The kit is currently only offered in “Frosted Detail” plastic, a multijet printed medium that produces fine detail, but which also causes these large models to be a bit of an investment– sorry about that! But please see my instructions for working with this plastic, it ain’t the same as your familiar model kit styrene!

The Bofors 40mm kit also has a complete instruction set, which can be downloaded and saved at any time.


The actual 1:16 version, assembled.


Instruction manual is available online.


Instructions include clear images for step-by-step assembly.


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Monterey Clipper Reference Site

I’ve long had a thing for Monterey Clippers, those charismatic traditional fishing boats seen at Fisherman’s Wharf in San Francisco. I’m still pondering the actual build of a model, slowed down somewhat by a lack of knowledge about their details. Their iconic fishing gear is all out in the open, and their traditional Hicks engines– complicated works with moving pushrods and gears and rocker arms– are also exposed, meaning you have to get them right!

So as I’ve started to accumulate details and lore about Monterey boats, I decided to organize it all in one place– a Monterey Clipper-pedia site. It’s just gone live recently, and will continue to grow over the next few months and more. See it at:
Monterey Clippers



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Dwight Brooks- A Giant of a Modeler


Dwight Brooks at the launch of his new model yacht “Atlantic”, Gull Lake, MN

Dwight Brooks built large scale model boats in the 1980s and 90s. His work is familiar to readers of the old Scale Ship Modeler magazine, where a number of his models appeared. See the links (at the right hand side here) for some of his SSM articles.

Dwight passed too soon in 1996, but his boats can still be seen in the Santa Barbara Maritime Museum, where all 32 were donated.



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Painting Shapeways’ “Frosted Detail” Plastic

I sell a good number of 3D printed parts through my Shapeways shop:

Of the various choices for plastics and process at Shapeways, the “Frosted Detail” line is the best for finely detailed parts on our models. But I’ve had issues painting this stuff, such as enamel paints that never cure or flat acrylic paints that cure, but then start showing a stain, as if something oily was wicking into the paint.

And I think that’s exactly what is happening, though it’s been confused with another FD issue, basic cleanliness. A little info about the process will help us to understand the perils:

Frosted Detail is actually made on a 3D Systems ProJet 3500HD printer using their “multi-jet” process. Think of an inkjet print head sweeping back and forth, but spritzing out drops of resin instead of ink. Then add a moving print platform that allows the head to print layer upon layer to build up a 3-D shape. BTW- these droplets are small. Remember when laserjet printers finally removed all the “jaggies” from text and line art? This happened when print resolution finally reached 300 dots per inch (DPI). The 3500HD is capable of printing at over 700 DPI- parts should be near optical quality!

But there’s more to this process. Liquid droplets won’t make a solid part, so the resin needs to be cured. This is done with a flash of UV light on every pass of the print head… and herein lies one of our painting hazards. Think of the resin as a bowl of wet spaghetti noodles, where the noodles correspond to the long polymer chains in the resin. The noodles want to stick together… let them set out a bit, and you’ll have a rock hard bowl of pasta (the strands have “cross-linked”). Add some oil first, and the noodles will stay slippery longer. In our UV-curable resin, we have the equivalent of this oil… a special oil that can be zapped into extinction when it’s hit with UV light. Kill the oil, and the noodles stick.

In multi-jet printing, an entire layer is laid down and zapped all at once. In another process, “stereolithography” (aka “SLA”), a UV laser plays across a pool of the same type of resin, selectively hardening the resin wherever it hits. Now, it’s standard practice in SLA printing to place the freshly printed parts in a UV booth for “post cure”, because the original laser zapping doesn’t fully cure all the resin in the target volume (a few hours in bright sun can do the job too). Hmmm… to my knowledge, Shapeways doesn’t post cure their multi-jet parts, so it seems to me there’s a risk that these parts could contain uncured resin which can leach out over time… and THAT can’t be good for paint!

I was originally blaming another detail of the multi-jet process for my paint woes. These liquid droplets in each layer won’t just hang in space, for example where the part has an overhanging feature. So in each layer, the print head lays down a bit of soft wax wherever the resin isn’t. The next layer’s overhanging resin droplets go on top of this wax, and are supported until they get fused. After printing, this gooey wax (it’s a lot like bacon fat) has to be removed… and Shapeways is not always perfect in doing this job. So it’s up to us to scrub off the last traces of wax, using solvents and/or aqueous cleaners. BTW, you’ll see some surface finish variations on your FD parts. Why? It’s the wax… surfaces “on top” don’t touch the wax, and can appear almost glossy clear. Surfaces in contact with the support wax have a frosty appearance after cleaning. This frost can be scraped or sanded off to improve the finish.

But anyway, I would clean my parts, even using a ultrasonic cleaner, and still my enamel wouldn’t cure. What’s with that? I then found that water based acrylics WOULD cure, so I’ve recommending that ever since. The plastic is an acrylic too, so this seemed to make sense.
Then I made a part that had a printed FD part attached to a brass tube. After painting with a flat grey acrylic, I saw that the paint on the printed part was staining, like it was getting wet, while the paint on the brass tube still looked dry. Again, what’s with THAT?

That’s when I started to suspect non-fully cured resin. For my latest batch of parts, I placed everything under a UV-A lamp (15W fluorescent tube, used for exposing PCB patterns) for an hour. Then everything was cleaned as usual to remove any wax, and painted with spray can enamel primer. It cured, and it’s sticking. Magic!

In summary:
1. Your Frosted Detail parts from Shapeways may contain uncured resin. Finish the cure with an hour under a UV-A lamp, or a few hours out in the sun.
2. Follow up with a thorough cleaning, using a solvent or aqueous cleaner (like Simple Green).
3. Then paint with the paint of your choice (even lacquer!).


Frosted Ultra Detail parts from Shapeways, post-cured, cleaned, scraped, and ready to paint.


Model after priming in enamel, and finished with acrylic.

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Dearborn in Dossin

My big model of the little tugboat “Dearborn” (seen in the header here), has been donated to the Dossin Great Lakes Museum. Since the museum rotates their model ship exhibits, I have no idea how long she will be on display… but she just went into the exhibit in June 2015.


Better here than hiding in my basement!

It’s a little bit sad to give up the model, but it takes up a lot of space at home, where it’s usually just hiding in the basement… I just don’t take the big R/C models out as often as I’d like!

Dossin is a great home for her, as the museum on Belle Isle in the Detroit River is just a few miles from the site of the Great Lakes Engineering Works, the yard which built her and other famous ships, such as the Edmund Fitzgerald.


Dossin Great Lakes Museum

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New Research Project: Towboats from Hillman Barge


I admit that my attention is easily diverted, when it comes to marine modeling. I’ll dive into whatever subject grabs me, whether it’s a battleship, a PT boat, a tug, a schooner, or even a DUKW. For a long time, I’ve been vaguely interested in the diesel towboats of our inland waterways, but I’ve never had a particular attachment to any one of them… just not enough for me to take on a research and modeling endeavor. Until now.

Recently, the early towboats of Hillman Barge and Construction have come to my attention. Hillman Barge was mainly …(you guessed it)… a barge builder, near Brownsville PA, on the Monongahela. But in 1945, Hillman hired on a promising marine engineer, Elmer W. Easter, to design for them a unique line of diesel towboats. Ten of these boats, in two sizes, would be built from 1947 to 1959. Variously described as” the most modern”, “yacht like”, “true streamline”, and “like a luxury liner”, they were also capable and efficient work horses on the rivers of the Upper Ohio region.

Three of these boats still operate today on the Kanawha in West Virginia. One is nearly original in appearance, while two have had their pilot houses raised… but in way that complements their original streamlined design.

So I’m well into my research of both the Hillman boats and their designer, Elmer Easter. I have hundreds of news clippings, a score or more of great photos, and the lines for one of the original 115 foot boats. From this, I’ve created a 3D CAD model… hopefully, I’ll get enough information to do the same for the larger 145 foot boats as well.

3-4a 12h167_1952_HLH2

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