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Patching Gaps in Styrene Kits

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Patching Gaps in Styrene Kits
Posted by CajonTim on Wednesday, January 25, 2017 8:29 PM

I was reading the thread on patching gaps in foamboard and it got me to thinking about how you patch gaps, imperfections, etc. when building styrene kits or scratchbuilding?

I've always used Squadron Putty and it works well enough, but I model in N scale and there can be a lot of waste with the Squadron Putty.  I try using tools to apply it but nothing seems to work better than a finger tip!

Does anyone have suggestions or recommendations?

Thx!

Tim

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Posted by dknelson on Wednesday, January 25, 2017 8:58 PM

Squadron putty, green or white.  But also you can use the solvent nature of styrene cements to insert a sliver of styrene, a dose of solvent cement, and then gently wet-sand the area to create a seamless seam.  

I have also heard of guys who mixed bits of styrene shavings plus solvent cement to create a "goop" that can close gaps.  But it is likely the surface will show the "damage" unless lightly wet-sanded.

Dave Nelson

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Posted by hon30critter on Thursday, January 26, 2017 12:44 AM

Hi Tim:

I use a variety of fillers but the most cost effective is automotive glazing putty. One tube will last you a lifetime (or until it dries out Smile, Wink & Grin). It goes on very smoothly, it can be thinned with liquid styrene cement, and it can be sanded to a very smooth, almost glossy finish. Sanding doesn't take much effort. It also doesn't dry out as fast as the Squadron Green putty when you are applying it and there is very little shrinkage when applied in thin coats. One word of caution is that if you apply a thick coat to a thin piece of styrene it will soften the styrene to the point of having it deform.

https://www.walmart.com/ip/Bondo-Glazing-and-Spot-Putty-4.5-oz/16927984

I also like Tamiya's white filler for tiny gaps and depressions. It is more liquid than the Squadron Green, but it does shrink a bit if you are applying larger amounts.

http://www.tamiya.com/english/products/87095putty/index.htm

Also, I use a palette knife to apply the putty. It seems to be easier to apply a smooth coat with the knife than with a flat screw driver. I've never tried using my finger. With my general lack of dexterity I'd be leaving finger prints all over the modelDunce:

http://www.michaels.com/10010981.html#pmpt=qualifying&start=7

Regards,

Dave

I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!

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Posted by doctorwayne on Thursday, January 26, 2017 12:57 AM

I might occasionally use putty to fill a shallow depression, but for holes in styrene, nothing works as well as more styrene. 

For round holes, use styrene rod and for square or rectangular holes, use strip styrene - both rod and strip material are available in a wide range of sizes from Evergreen.  I always keep a good selection on-hand, and used .060" sheet styrene to make a holder for all of it...

Select a strip or rod with a shape similar to that of the hole, but about .004" or .005" bigger in diameter or dimensions than the hole.  Coat the filler material with solvent-type cement (I use MEK), and use a small brush to coat the insides of the hole with cement, too. Let both sit for a few seconds, then repeat another one or two times - you want both surfaces to be softened by the solvent.  Next, force the tip of the filler material into the hole - if it won't start easily, withdraw and repeat application of the solvent to both surfaces.  When properly installed, the filler piece should protrude right through the material being filled.  If not using a short piece of filler, cut or snap the plug off some distance from the actual repair area, then leave it to harden overnight or at least for a few hours - if it's too soft, the repair area will be difficult to finish properly.
Once the plug(s) have hardened, use a sharp blade to trim the protruding ends (both inside and outside), then finish using knives, files and/or sandpaper.  Once finished and painted, it should be at least next to impossible to detect.

Among other things, I'm currently doing a little re-working of a Bachmann locomotive.  Some of that involved removing details and replacing them with better parts, but it also included simply removing things and being left with holes to fill. Here's the loco with some new stuff, while the white dot on the steam pipe and white dot and and white rectangular areas on the boiler are styrene-plugged holes:

If the holes cannot be matched with filler material slightly larger than the holes, then re-drill the holes to a larger size that will suit the filler strips which you have on-hand.

Here's an Athearn boxcar getting some modifications.  In addition to lowering the eaves and adding a new roof, I also replaced the ends with ones from Tichy.  The Tichy ends come with some holes cast into the part to allow installation of details, but they weren't where I wanted them to be, so simply filled them with some styrene rod.  Here's the end with some new details and the old holes filled and finished:

I also modernised a couple of Bachmann 10 Wheelers, but thought the stock tenders to be both too long and too wide,  Too long was easily handled by a razor saw and the clean cut left little to clean up or fill.
However, making the tender narrower posed a problem.  The usual procedure is to cut a block of pine to fit snugly into the body shell, then run the whole shebang through one's table saw.  Lacking such amenities, I cut blocks using my Skilsaw, then did the disection with a handsaw, as the saw's kerf was about the same width as the amount needing to be removed.  However, the work was a little less precise than hoped for, and after the two halves were rejoined using an interior splice plate of .060" sheet styrene, there were irregular gaps to be filled on both ends of both tenders. Bang HeadWhistling
For these, I used strip material a little thicker than the body shell, and just crammed in whatever would fit, filling the bulk of the opening, then adding strips of .005" material to fill in any gaps.  I let it sit for a day or two, then shaved off the bulk of the excess using a sharp #17 blade. Here's the rear of one tender...

...and the front...

...and the deck, where I did use some putty over the styrene gap-filler, as the thickness of the deck was not the same on both halves:

Painted and in service, the repairs aren't noticeable and I have no worries that the plugs will drop out or the gaps re-appear, as the parts are as good as welded together:

Wayne

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Posted by j. c. on Thursday, January 26, 2017 7:30 AM

for large gaps  i use nitro-stan(automotive glazing putty) for smaller gaps i use sherwin-williams shrink free spackling .

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Posted by Eric White on Thursday, January 26, 2017 9:01 AM
For applying putty, I use an old no. 11 blade. I scrape the putty off it when I'm done with another old blade. Sometimes I have them in a knife handle, sometimes I just use the bare blade. It's small enough to get into most spaces, and I can dig a tiny amount of putty out of the tube without wasting it. To prolong the life of the putty, I keep it in a zip-lock bag.
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Posted by Lone Wolf and Santa Fe on Thursday, January 26, 2017 6:39 PM

I use Testors Contour Putty.

Modeling a fictional version of California set in the 1990s Lone Wolf and Santa Fe Railroad
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Posted by CajonTim on Thursday, January 26, 2017 11:15 PM

Thanks for the input everybody!  I went to Pep Boys today and picked up some Bondo Glazing & Spot Putty to try out.  It worked out well and was a little slower setting up than the Squadron Putty, which was very helpful.  I also tried out Eric's suggestion on the #11 blade.  In addition I used a single edged hobby razor blade.  Both enabled me to waste less product, which in turn mad the sanding quicker and easier.  I definitely recommend using a respirator with the Bondo (fumes and dust).

Thanks again!

Tim

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