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

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Filling in Gaps on Structures - What is Best to Use?
Posted by richhotrain on Friday, January 04, 2019 4:08 AM

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

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Posted by Jumijo on Friday, January 04, 2019 6:19 AM

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.

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Posted by kasskaboose on Friday, January 04, 2019 6:52 AM

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.

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Posted by mbinsewi on Friday, January 04, 2019 8:09 AM

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, Off Topic

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Posted by 7j43k on Friday, January 04, 2019 8:56 AM

richhotrain

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.

What have others used successfully for this purpose?

Rich

 

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.

 

 

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Posted by ROBERT PETRICK on Friday, January 04, 2019 9:06 AM

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

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Posted by MisterBeasley on Friday, January 04, 2019 9:45 AM

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.

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Posted by richhotrain on Friday, January 04, 2019 10:03 AM

7j43k
  

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.

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

Rich

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Posted by richhotrain on Friday, January 04, 2019 10:04 AM

ROBERT PETRICK

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 

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

Rich

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Posted by richhotrain on Friday, January 04, 2019 10:06 AM

kasskaboose

Are you referring to gaps between the walls? 

Yes.

Rich

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Posted by RR_Mel on Friday, January 04, 2019 10:46 AM

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.
 
 
 
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Posted by dknelson on Friday, January 04, 2019 10:53 AM

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

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Posted by PED on Friday, January 04, 2019 11:00 AM

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. 

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Posted by ROBERT PETRICK on Friday, January 04, 2019 11:24 AM

PED

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. 

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

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Posted by doctorwayne on Friday, January 04, 2019 11:41 AM

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...

...and the engineer's side before sanding...

I store the tightly-capped tube upright, in order to keep the solvent at the top, and have used the same method on several other projects, including this shortened styrene tender...

I find it easier to apply than the Squadron stuff, and easier to sand, too, and the fact that it doesn't dry-out in the tube like Squadron is a big plus.

Wayne

 

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Posted by richhotrain on Friday, January 04, 2019 12:19 PM

dknelson

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

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

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Posted by mlehman on Friday, January 04, 2019 2:34 PM

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.

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Posted by snjroy on Friday, January 04, 2019 3:18 PM

richhotrain

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

 

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.

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Posted by ctyclsscs on Friday, January 04, 2019 4:48 PM

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

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Posted by Doughless on Friday, January 04, 2019 5:20 PM

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.

 

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Posted by zstripe on Saturday, January 05, 2019 4:07 PM

richhotrain

 

 
ROBERT PETRICK

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 

 

 

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

 

Rich

 

Rich,

I use Evercoat glazing spot putty over primer surfaces to fill in rough spots and minor imperfections that the primer will bring out, The glazing putty is not really used for a fill over 1/8'' thick...keep that in mind. It's used as a prep, prior to painting for a smooth finish.

I use Squadron white putty for filling seams and such in styrene, ABS etc.

If You still plan on building the CMR lift bridge kit, Your use of the Squadron putty will give You some experience when it comes time for the bridge, because that is what they recommend for filling in the top of the girders on the main span of the bridge so it is smooth. The instructions say to use Green, but that is before the White came out. I decided not to fill in the top of the girders on My bridge.......

I believe it looks ok without them being smooth on top........photo before touch-up:

A Xacto #17 chisel blade in a #1 knife works good for spreading putty.

Take Care! Big Smile

Frank

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Posted by Erie1951 on Saturday, January 05, 2019 4:45 PM

Rich, is your building supposed to be concrete, wood, or brick? I don't think that you mentioned which. There are different techniques for creating wall-end trim for each such as end-caps, columns, etc.

Russ

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Posted by dknelson on Saturday, January 05, 2019 5:32 PM

I was just reading Jeff Wilson's book on Structure modeling ("Modeling Structures," his second one, basically a rewrite and expansion of the first one, "Basic Structure Modeling") and Wilson interestingly uses sucessive (and careful) application of thick CA to fill up such gaps, not putty.

Dave Nelson

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Posted by doctorwayne on Sunday, January 06, 2019 2:22 AM

After re-reading your original post, Rich, I think that you'd do better by filling the gaps with styrene.  Any type of putty filler, caulking, glue, etc. may fill the gap but because the gaps are between sections of wall, such fillers offer little-to-no structural strength.

When I narrowed a couple of Bachmann Ten Wheeler tenders, I used a handsaw (not a modeller's saw, but a carpenter's saw) and the cut was a little on the rough side. 
I cemented the two sides together as best I could, then soaked both the gaps and the filler-pieces of styrene with solvent and jammed the filler into the gaps.  The next day, after the joints had hardened, things were cleaned up, and any minor irregularities puttied over...

richhotrain
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.

What you should have done is sanded or filed the too-long panels back to match the width.  
It also sounds as if you assembled the upper stories first, then added the ground floor, and the accompanying gaps.  It would have been a simple task, before putting the latter walls together, to cement a strip of styrene of suitable width (and matching the thickness of the walls) to the end of each wall section. 

Done in that manner, there would be no gaps to fill and no weak spots in the finished structure.  Perhaps you can force some strip material into the gaps, as I did with those tenders.

I'd also advise similar techniques for filling holes in styrene things, whether they're a result of a mistake or a feature of something which you don't wish to retain. 
For small round holes, up to about 1/8", styrene rod, about .003" larger than the hole works well:  coat the rod and the inside surface of the hole with solvent-type cement, then jam the rod in place.  You can use similarly-sized strip material for square holes, or simply drill them out to accept appropriately-sized rod.
Trim-off any excess after the joint has fully hardened - it shouldn't need any filler, and should be undetectable once painted.

The wall shown below is spliced together somewhere near its mid-point.  I trimmed both segments to maintain window spacing, then used a styrene splice plate on the interior, liberally-wetting the mating surfaces - wall ends and backs and splice plate - with solvent, then forced the sections together.  When hardened, I re-carved the mortar lines to completely hide the joint.....

...the wall is as one piece.

Is there any chance you could disassemble the offending walls? 

Perhaps a photo would help us to offer more suitable advice.

Wayne

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Posted by richhotrain on Sunday, January 06, 2019 3:43 AM

Erie1951

Rich, is your building supposed to be concrete, wood, or brick? I don't think that you mentioned which. There are different techniques for creating wall-end trim for each such as end-caps, columns, etc. 

The building represents a poured concrete multi-story warehouse.

Rich

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Posted by richhotrain on Sunday, January 06, 2019 3:48 AM

zstripe
 

Rich,

I use Evercoat glazing spot putty over primer surfaces to fill in rough spots and minor imperfections that the primer will bring out, The glazing putty is not really used for a fill over 1/8'' thick...keep that in mind. It's used as a prep, prior to painting for a smooth finish.

I use Squadron white putty for filling seams and such in styrene, ABS etc.

If You still plan on building the CMR lift bridge kit, Your use of the Squadron putty will give You some experience when it comes time for the bridge, because that is what they recommend for filling in the top of the girders on the main span of the bridge so it is smooth. The instructions say to use Green, but that is before the White came out.  

Thanks, Frank, for that info. Yes, I do still plan on building the CMR lift bridge kit, although I am going to fabricate my own towers to look more like the PRR lift bridge south of downtown Chicago. The CMR lift bridge towers are too angled for the look that I am going for.

Rich

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Posted by richhotrain on Sunday, January 06, 2019 3:58 AM

doctorwayne

After re-reading your original post, Rich, I think that you'd do better by filling the gaps with styrene.  Any type of putty filler, caulking, glue, etc. may fill the gap but because the gaps are between sections of wall, such fillers offer little-to-no structural strength.

 

richhotrain
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. 

What you should have done is sanded or filed the too-long panels back to match the width.  

It also sounds as if you assembled the upper stories first, then added the ground floor, and the accompanying gaps.  It would have been a simple task, before putting the latter walls together, to cement a strip of styrene of suitable width (and matching the thickness of the walls) to the end of each wall section. 

Done in that manner, there would be no gaps to fill and no weak spots in the finished structure.  Perhaps you can force some strip material into the gaps, as I did with those tenders.

Is there any chance you could disassemble the offending walls? 

Actually, I assembled the first story walls first, then added the upper stories one at a time. The varying widths of the wall sections were not all that significant, so I took no precautionary steps to even them out for fear that I would create an even bigger problem. Except for the gaps, the finished wall looked pretty even.

Regarding the gaps, I decided to sand the connecting walls before proceeding with filling the gaps. To my surprise, the gaps filled in, presumably as a result of the sanding filling in the gaps with the styrene particles resulting from the sanding. So, now, I am going to do a little more finishing sanding and then spray paint the entire wall structure. I will either sand or file the ends on the wall where it meets the side walls to even everything out.

Rich

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Posted by Graffen on Sunday, January 06, 2019 4:00 AM

New times, new tech and new methods.

I use water soluble Vallejo putty on my modeĊ‚s as it is easily  applied and then, instead of waiting for it to dry and then sand, I immediately use a moistened Q-tip to shape the joint.

It may require more than one application, but it doesn't damage surface detail.

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Posted by zstripe on Sunday, January 06, 2019 5:39 PM

Rich,

I also used the Squadron putty to fill in seams and imperfections on all the piers/counter weights for the bridge so no seams would show on the concrete parts.....then I roughed them up with #40 grit sand paper to give them a texture........so keep that in mind (the putty) when You are ready for the bridge:

Take Care! Big Smile

Frank

 

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Posted by bearman on Wednesday, January 09, 2019 4:30 AM

I am in the Squadron putty corner.

Bear "It's all about having fun."

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