Filling in Gaps on Structures - What is Best to Use?

Model Railroader Layouts and layout building
1

I am building a large structure with a lot of wall joints. I want to cover these gaps, but I am not sure what to use.

I do have an unopened tube of Testors Contour Putty that I bought some time ago on the recommendation of the guys at my now closed LHS. Is that the best solution for filling in gaps? Or, are there better ways to do this?

I have read about all kinds of techniques including caulk, Elmers Glue, wood glue, even mixing plastic glue with styrene sprue to make a ‘goo’.

What have others used successfully for this purpose?

Rich

2

Joint compound is a good choice, because it’s easy to apply and cleans up easily with water. Once dry, it can be shaped and smoothed with a sanding stick.

You can also glue the walls with thick tube glue. It will act as a filler and can be sanded once dry.

In order to lessen the amount of gaps, file each edge and dry fit before glueing to ensure a good fit.

3

Are you referring to gaps between the walls? If so, you can get thin Stryene tubes to serve as gutters. They fill in the gaps nicely.

Perhaps a picture might help.

4

I used just a thin bead of latex caulk, and spread it down the joint with my finger. I did this from the inside. After the outside was painted and finished, no more tiny gaps.

I think the putty you have would work too. Elmers might seep through to the out side.

Not that this as anything to do with this, but I remember the finish carpenters at work, while building the fancy wood counter for the receptionist desk at the clinics we built, painted the drywall behind the wood work flat black, were ever their was a joint in the finished wood work. It was albout hiding the joint.

Yea, I know, [#offtopic]

Mike.

5

That’s going to depend on what material you are building with. And what the texture is. And what the prototype surface is. And how invisible you want the joint. And how much work you’re willing to put in. And…

I WILL say that you’re going to have a problem getting an invisible butt joint for clapboard siding.

Ed

6

Squadron putty. Made specifically for styrene. Goes on easily using small little tiny spatulas/trowels that come in a variety of shapes and sizes. Sands smooth using 400- or 600-grit (or finer) sandpaper. Used to come only in green. Now comes in gray and white as well.

Makes invisible joints. Not virtually invisible. Invisible.

Robert

7

I use square balsa wood strips inside all the corners of kits. I glue it there with CA. This stops light leaks at the seams and provides a much more solid joint between sections.

8

The structure is made out of injection molded styrene. The surfaces with the gaps are smooth, just like the prototype.

Rich

9

OK, that sounds like a resounding endorsement of squadron putty.

Rich

10

Yes.

Rich

11

I’ll second the Squadron Putty! If needed you can thin it with Testors Liquid Cement. Easy to manipulate, doesn’t shrink and sands good to.

Mel

My Model Railroad
http://melvineperry.blogspot.com/

Bakersfield, California

I’m beginning to realize that aging is not for wimps.

12

I used Squadron Putty (green and white tubes) for years and was satisfied. Then I noticed in the latest MR that Cody Grivno used a different putty product in the article about building the limited run resin kit for the Kalmbach Publishing building in West Allis: Perfect Plastic Putty by Deluxe Materials. Since I was newly out of Squadron I went to the LHS and they enthusiastically endorsed Perfect Plastic Putty. Interestingly enough it is a British import. It costs a bit more than Squadron.

I have yet to try it so cannot give a personal reaction, only relay the enthusiasm of the guys behind the counter and the seeming endorsement by Cody Grivno.

Needless to say – for sure, the primary goal should be to avoid such gaps when possible.

Dave Nelson

13

I use Vallejo Plastic Putty which I think is pretty much the same thing as the Squadron Putty. I use it because it is an acrylic based product to match the Vallejo paints I use. Good working time, sands good and can be used to fill large gaps but may take several applications.

14

Yeah, there are several brands these days, and they seem to be very similar. Tamiya also has a family of different formulas for different types of plastic.

They appear to be plastic resin dissolved in solvent, very similar to the goop OP mentioned, but smooth fine-grain consistent texture. The solvent blends and bonds into the structure parts like weld material, and as such it can be ‘ground’ just like a weld and leaves an invisible joint.

Check out the hobby shops’ tool section for a set of those tiny spatulas: round, square, pointed, flat, offset hosel. Thin flexible stainless steel blades. Easy to use, easy to clean. Gets into tight places.

Robert

15

At one time, I used Squadron putty, but I found its shelf life to be less than useful, and its application unsatisfactory, the latter perhaps due to my methods. It’s not the best for sanding, either.

Nowadays, I use Bondo’s Glazing and Spot Putty: it comes in a tube, is much cheaper than comparable hobby products, and seems to have an unlimited shelf life. Once applied, it hardens quickly (don’t apply it too heavily), and sands easily.
It’s available at any automotive supply store.

I first used it to repair a brass tender: a previous owner had attempted to alter the coal bunker, and started to cut-off the top of the sides, using a cut-off disc. It’s my guess that he started on the rather plain fireman’s side of the tender, but realised, when going to the engineer’s side, that the ladder detail was going to complicate the plan.

I soldered some sheet brass to the inside of the tender to close-off the inside of the cuts, then used some JB Kwik Weld to fill most of the depth of the cuts, making sure to not fill right up the the surface level of the sides.

The Bondo product comes in a tube, and upon opening it, I discovered a lot of liquid (the solvent) at the top of the tube. Usually, the process is to knead the closed tube to mix the ingredients, but instead, I simply stuck a small screwdriver into the tube, intending to stir them. Since the screwdriver wasn’t long enough to reach too far into the tube, I withdrew it, planning to use a longer screwdriver.
However, there was a nice blob of putty on the end of the little screwdriver, so I wiped it into the cut and smoothed it using an X-Acto chisel-type blade. It looked pretty good, so I simply continued with that method.

Here’s the fireman’s side of the tender after sanding…

16

For sure. The problem here is that it is a multi-story warehouse building, three panels wide. The upper story panels are ever so slightly wider than the first story panels, so I cannot manage a tight fit, leaving slight gaps to be filled.

Rich

17

My gaps tend to be minimal, but often frustrating as they show up when I light up buildings. Waht works best for this is often black liquid electrical sealant. It’s like blakc vinyl tape in a bottle. It can be a little nasty to work with until you get used to the fact you have to keep it off your fingers or you’ll be marking up everything.

I use toothpicks or stripwood scraps to apply it. I suppose a syringe might also work. Works great for light leaks, but is also flexible, which is a good property. It sticks well to just about everything, too. Comes in different colors, which can be useful, although basic black works well for me.

18

I have used Testors putty for years. It is easy to apply and it has a long shelf life. It is easy to sand, but I prefer to apply multiple light coats, removing the excess putty with an X-Acto knife. This minimizes sanding that can damage the other components of the model. It does shrink, so a single coat is rarely sufficient. After applying a primer coat of paint, I sometimes add some putty to improve the finish - it seems to bond well on sanded primer. Since you already have it, why not try on spare parts? It won’t go bad if you open the tube.

Simon

19

I don’t know if this will help, but on some concrete structures you can see lines or joints between different pours. Or when they added sections horizontally, they often poured new columns against existing ones. So not everything has to be one perfectly smooth stretch of concrete.

https://www.google.com/maps/@40.450598,-79.9863337,3a,68.4y,149.37h,91.23t/data=!3m6!1e1!3m4!1sty8m4ozy3SYAFfDx-OpnUA!2e0!7i13312!8i6656?hl=en

Jim

20

I would think that caulk would be the easiest if its simply filling in gaps from the inside and it won’t be seen from the outside.