SPA Modeler

This well known Dora is going to be a future build. I'm in the process of getting together all of the materials including not one but TWO conversion sets. The old JRutman resin conversion...


And the newer (and less complete) Real Model conversion from the Czech Republic...


I don't like the idea of using the resin fuselage and want to utilize as much of the kit exterior as I can so my plan is to use the Real Model components and manually add the cowling bulges to the kit fuselage using the Rutman fuselage and reference materials as a guide. Volume 2 of the Eagle Editions Dora set has some good photos of the cowling as well as a set of drawings for a D-13 including some pertinent cross sections.

If anyone finds any good reference photos or drawings of the D-13, especially around the engine cowling, post em up!

I think Rutman sold his D-13 molds to Grey Matter and that's where I got my D-13 conversion from.

Looks like an interesting project John!

I just received the Grey Matter D-13 conversion kit. It is a resin conversion comprised of two fuselage halves, the engine cowling, supercharger intake scoop, spinner, prop blades, center fuselage section and a bulkhead of some sort.


The parts are molded in light grey resin and upon first inspection, it is a mixed bag in terms of quality. The fuselage pieces are quite thin and flexible. The thickness of the parts seem to be similar to the kit parts, which is probably an attempt by the maker to reduce the amount of work it would take to accommodate the internal kit parts. However, the loss of rigidity may introduce alignment/strength issues but perhaps the joining of the fuselage pieces to one another would achieve an acceptable level of strength.



The cowling has been modified to reflect the absence of guns above the engine.


Next, I'll take a closer look at the resin set by doing some dry-fitting and comparing them with the kit parts.

The Jumo 213F engine of the D-13 required larger support arms that necessitated bulges in the frontal fuselage as well as a larger supercharger intake.


The D-13 utilized wide paddle-shaped propeller blades (VS9) and a MG 151/20mm cannon firing through the spinner. You can see a bit of the inconsistent molding quality in the Grey Matter spinner.


The single central gun used one central chute for expended ammo casings and the resin kit provides the necessary modification.


The fuselage parts are not perfectly square with one another and there is some minor warpage but with a few minor adjustments, they should go together reasonably well.



All of the D-13 modifications occur forward of the cockpit. The major mod being the addition of a subtle bulge on either side designed to accommodate the larger engine support arms that runs from the forward cowling hatch to the front edge of the fuselage.


Comparing the kit fuselage on the left with the resin fuselage on the right, you can see that the thickness of the resin is comparable to the kit plastic. You can also see some of the inconsistencies of the resin mold... the plug for the exhaust stubs will not be able to seat properly without some major cleanup.


A general observation of the molding quality of the resin kit... the components that are unaltered from the Hasegawa kit are clean and molded about as finely as you would find on the kit part. The areas of modification, however, varies in refinement as evidenced by this circular fuel port, which is mounted slightly higher on the D-13 than the D-9. And I thought I was bad at centering concentric circles!

I know this may be of very limited interest to most of you since the D-13 was not a widely used aircraft. I'm kind of using this as a frame of reference for a future build and the contents will probably be cut and pasted into the build once it gets started.

Back to the work table and using tape to put together the major components of the resin conversion, I can compare it to the Hasegawa kit. The resin fuselage features the same internals as the kit plastic, down to the locating tabs, locating pins and holes, which make fitting the pieces a little easier. But even so, it takes a bit of effort to tape the resin halves together.



It seems pretty obvious to me that the masters for the resin mold were most likely the actual Hasegawa fuselage parts with the D-13 modifications grafted onto them. Not making a judgement on that... just an observational guess as to how this resin set came to be. This is in line with my previous observations that the details shared by the D-9 and D-13 seem to be molded much more uniformly than the added details. There are some exceptions to this including some messiness around the exhaust openings and the bottom cowling seam.



Resin inherently comes with set of common risks like shrinkage and warping. Here is an example of resin warping at the tail joint.


Looking at the interior side of the cowling parts, I'm guessing that the resin cowling master was formed by sculpting the Hasegawa part. You can see evidence of putty or other material being used to fill in the voids to facilitate sculpting from the other side.


Based on my personal distrust of resin as a model construction material, I'd prefer not using these parts if possible. I think it is possible to follow in the steps of the resin maker and make my own modifications to the kit parts, using this set and other references as a guide. The port side bulge seems to be fairly simple to sculpt as it is pretty uniform and there is nothing in the way. The starboard side is a different matter. I'd have to contend with the base of the supercharger intake, which is much larger than found on the D-9. To analyze the situation even further, I can place the kit cowling onto the resin fuselage to see the contours of the added material.



The port bulge should be fairly simple to execute using Milliput as sculpting medium and perhaps a strip of sheet styrene to serve as a base/form for the sculpt. I haven't figured out the starboard bulge yet. I could remove the upper portion of the supercharger base and then sculpt the bulge in a similar fashion to the port side, ideally at the same time to maintain symmetry.

Another option is to mate the starboard resin half with the plastic port half. That would cut in half the amount sculpting I would need to do and also give me the two locating pins to mount the radiator cowling assembly, which is missing on the resin parts. I'd have to still mess with the messy resin around the exhausts and try to correct the warping so I'm not loving this approach.


Since the D-13 modifications are confined to the forward portion of the fuselage, I could also take a modular approach to replacement. To avoid the headaches of having to deal with the supercharger, I could graft a portion of the resin onto the kit fuselage. This simplifies some things but complicates others since it involves cutting and trying to match parts to one another.


My initial game plan is to make the necessary modifications to both starboard and port sides of the kit fuselage and capping it off with the resin cowling. And then falling back to the resin fuselage parts, if necessary. Just for fun, I may take a stab at trying to sculpt the cowling since there is nothing to lose by doing so.

That looks to be a lot of issues to deal with. I feel confident that you will win!

First: brilliant photography both in the light box and on the bench. It was truly a pleasure to read and follow your thoughts and see the relevant sections depicted so clearly. That is a hell of a lot of work and you do it as well as anybody out there.

Thank you for a very evenhanded review of the Ruttman-Grey Matters resin conversion kit, John. You probably know this already but the cross section looks like it warped as it air cooled; that is common to a lot of 1/24 X-Wing resin kits out there. I was nodding my head and agreeing with your thoughts and choices as probable, possible, and even pertinent changes to be made to the pieces as they stand. I think the nose section-cowling will require considerable cleanup, rebuilding and a “discovery factor” attached to it. Is it possible to carefully clean up and reheat the fuselage sections that they straighten out? That would be my approach—heat ‘em with hot water and steam, gently at first—and begin to train them back to true.

What you wrote about modular fitting was apt. With that in mind, I would start with straightening things out as though the resin was your first choice (which I think was your initial thesis here) then modify as warranted. I really did not like the off centered concentric circles, because a garage kit builder is usually going to aim for a higher standard in terms of details and accuracy. That really bugs me. That is just not necessary. It is clearly a mistake.

I began to wonder though if a good set of plans and a few sketch ups in rhino might be a masterful John Kim project and not have you interpret and improve upon someone else.

Wow! This is gonna be a very ambitious project. Can't wait to see it.