Building A Resin Kit Step-By-Step, Part I: Choosing a Kit, Evaluating The Fit

If you’re building a fleet of HO-scale Thunderjets, sometimes you want more than just what Aurora and Auto World have made. And if you don’t want to spend $65 for a MEV body, or if you want something even more unusual than what they make, what do you do?

You go hunting for one cast in resin. There are several people out there making resin kits that, for the most part, are molded from die-cast bodies of cars made by Hot Wheels, Matchbox, and some of the other collectible 1:64 scale makers.

The resin kits are light weight and thus can be fast if they go together well, but they can be challenging to build since, like so many things in life, they can be like a “house of cards” where a mess up at any step can bring the whole project down.

In my “Meet The Fleet” posts I’ve profiled some of the resin kits in my slot collection. At this point there are only 2 of them actively racing; both are Alfa Romeos, a GTV coupe and a 2600 Sprint coupe; the former is painted, the latter was delivered molded in color. There used to be more, however they didn’t survive long:

So the resin kits are a mixed bag; some of them are a lot better than others. Some are nicely made, but they can fool you, looking great when you buy them, only to find when you go to put one together that the wheelbase doesn’t match the chassis, the screw posts are positioned wrong, or worse, the screw posts are fine but you mess them up drilling them for screws and wind up trashing the body because of it. And they can be fragile; I lost my first 2 Jaguar E-Types to screw post breakage, since the resin had enough air in it when it was cast that the strength of the post wasn’t enough to hold when that fatal crash came. Maybe I should have driven more carefully!

Several times in the past, when I’ve built a kit that came out well, I’ve said, “Well, I wish I’d photographed this.” So this time, I did!

I decided to add another resin kit to my collection as another “reserve car” that won’t be a permanent member of the racing fleet but will “stand by” for special occasions or as a stand-in if something in the fleet is in the shop. I’m going to document the process all the way from start to finish, including my screw ups (I always make plenty)! So consider this a documentation of the process as I go through it, with warnings about what to look out for, and descriptions of the mistakes I’ve made so you don’t have too!

Let’s start with selection: what car do you want to build?

As I’ve mentioned before elsewhere on this blog, I’m not a huge fan of Porsches; my heart belongs primarily to the American and British brands (and Alfas, of course). But there are a few Porsches I like, and my favorite of them is the 356 coupe; it’s just too charming of a car not to like, and though their reputation is outsized in relation to their actual capabilities, there’s no denying they have earned their place in the pantheon of great sports cars. So when I found a 356 coupe for sale from one of my best ebay vendors, I decided to go for it.

So right off the bat, we can see that this resin casting is modeled on the recent Hot Wheels release of the same car. It’s clearly that car, as the size and details show. Seeing this, the first question you should ask is: is the wheelbase of the die-cast car this kit is modeled on going to match the 2 wheelbase options of a Thunderjet chassis?

To answer that, the first thing to do when you acquire your new resin body is test fit a chassis that is either the very one you want to use, or absolutely identical to it. I would also recommend doing this test fit with the wheels and tires you plan to use, although I have not done so here, because I didn’t decide until the project was well underway which wheels and tires I wanted use. Even so, stock wheels and tires will still tell you a lot: check the fore and aft positioning of the wheels and see if it looks good! If you’re already seeing an awkward look, you need to decide right then and there if you are going to be happy making “adjustments” to the body by grinding away material from the wheel wells with your Dremel or perhaps making other mods to get the chassis to fit, or if doing so is going to result in a body that is aesthetically unacceptable. If the latter condition exists, you’re already done; chuck it and look for something else.

In the case of the Porsche I’m building here, the result was what it usually is with resin kits: “close enough.” Some grinding of material away from the rear edge of the rear wheel wells was required to get the chassis to fit properly, but fortunately there was enough clearance inside the body for the motor; there was no rubbing against the rear screw posts or any other of the commonly found “almost but not quite” fitment problems so often encountered when using the Auto World Ultra-G T-jet chassis.

But be careful: do this test fitting with the window insert in place! The window inserts on almost all resin kits are very cheap vacu-form plastic which hardly ever fit right, and I’ve only had one that didn’t need to be trimmed, cut, sliced or diced just to fit the car. The window insert that came with this particular car was especially bad; it was so misshapen that I had to actually cut it in half and take a strip of material out from between windshield and back window, as well as trimming away and discarding the side windows. This second part was OK since I prefer the look of open windows anyway, but it wasn’t even an option.

It can be difficult to test fit the chassis with these windows in place since, once they are finally installed, you’ll be using super glue to adhere the window insert to the body, but you obviously can’t use that for a test fit. I’ve found that using a dab of white glue to hold the windows in place during the test fit can work, once you’ve trimmed the window insert enough that it fits well enough for the glue to effectively hold it. What you are checking for here is that the motor gears clear the window insert at the front and the back, or if you’re going to have to cut into the visible “glass area” on the car in order to clear everything.

One of the issues this body had was that the front screw post wasn’t long enough; the chassis still fit and cleared everything, but the rake that resulted looked awkward, so I choose to insert a large plastic shim at the bottom of the front screw post to raise the front of the body and give the car a better look.

This is all par for the course when fitting a body to a chassis, but expect a poorer fit-and more work to compensate for it-than you’ll encounter with a factory made plastic body designed for a T-jet chassis.

But don’t grab your drill to tap those screw posts yet! In Part II of this saga, I’ll show you how to compensate for another imperfection in the resin casting you are likely to encounter, and how to check for additional potential “gotchas” before you start putting significant effort into the paint and detailing!