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chuck540z3

1/32 P-38L "Kicked Up A Notch". Jan 15/16: FINISHED!

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Chuck, we have a thread about this already in the Techniques forum:

 

http://forum.largescaleplanes.com/index.php?showtopic=33396

 

Perhaps you could add your thoughts there? That way it's all in the one thread. I understand if you'd prefer not to, though. Just thought I'd point it out. Looking forward to your tutorial either way!

 

Kev

Thank you Kevin. I'm always interested in new techniques, even if they are only for me. I just read through the thread and I was surprised at the use of turpentine! I use ordinary Tamiya cement instead, so I'm sure my experience and possibly problems, will vary quite a bit. Like a modeler who prefers enamel paint over acrylic ( or vice versa), I think I'll stay with what I'm used to- and can predict the outcome. I have had extremely good results so far and a few almost disasters, so I think I can now tell what works and what doesn't. That doesn't make my method better at all, but another perspective on the creation and use of Liquid Sprue might be useful to some.

Edited by chuck540z3

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While your sharing your amazing tips, any chance you could let us know how you get such a realistic finish on the brass gun barrels? I think they are the best looking barrels I have ever seen!

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Liquid Sprue Tutorial

 

So- called “Liquid Sprue†(LS) has been around for a long time and it has many uses as a filler and an adhesive, but like most things used in modeling, it has its strengths and weaknesses.  I am no expert on the stuff, but I have experienced what many of these properties are in the past 18 months since I started using it, so I offer what I have learned so far.  The LS I am using is made entirely of Regular Tamiya plastic cement and small bits of sprue melted into a thick mixture right in the bottle.  It is best to start off with a bottle of glue that is maybe only 1/3 full, to make room for the sprue.  The consistency of LS I use is as thick as possible, but still thin enough that you can apply it easily.  This is very much like creamed honey that is white and not the much thinner yellow honey that is easily poured.  The thicker the LS, the less glue that needs to dry, which is very important as you will see later.  It might take a day or two to achieve the right mixture, since the sprue usually takes several hours to completely dissolve before you can stir it.  To apply LS, I just use the brush on the cap of the glue bottle or a small microbrush.

 

Let's start with an example on my most recent attempt to tighten and straighten the cannon hole on the nose of this P-38 build.  Here is the “Before†pic of the football sized hole as found on the kit part.  Not only is the hole too large, but it is offset to the right.

 

 

 

Cannonhole1.jpg

 

 

 

This is what it looks like today after the application of LS a week ago.  You can barely make out the outline of the old opening, but there are no holes or blemishes.  Pretty amazing if I do say so myself.

 

 

 

Nosefix5.jpg

 

 

 

Here is how I did it.  I filled the hole with some LS, being careful to fill the entire hole and only a small amount of the surrounding edge of the hole.  I then made sure I applied about twice the thickness I needed, to compensate for shrinking, but you also have to compensate for sinking.  This honey-like mixture wants to fall through the hole due to gravity, so I inverted the nose piece several times over the period of 5-10 minutes until the LS set as it started to dry.

 

 

 

 

Cannonhole2.jpg

 

 

 

 

Here it is after drying for 1 week.  You can't let LS dry long enough, but 1 week for this thickness of LS is a minimum time period.  Note how the LS has shrunk and wrinkled.

 

 

 

 

Nosefix1.jpg

 

 

 

 

After sanding down the LS to conform to the rest of the nose cone, I drilled a small hole, then used a fine circular file to enlarge the hole to the size and location I wanted it, then carefully sanded it smooth.   The base of the brass cannon has a large collar which I'll never see, so to allow insertion of the cannon from the front, I placed the end of it in a power drill, using the drill as a lathe as I applied a file to the base, grinding it down to size.

 

 

 

 

 

Nosefix2.jpg

 

 

 

 

 

 

With the cannon in place, the hole looks much better and more to scale, but a few problems are still left behind, both of which are very common when using LS.    As the LS shrinks, or if you work the LS too much when applying it, air bubbles are very common.  This pic shows that I also didn't apply the LS to the upper right margin enough, which has left a depression behind.

 

 

 

 

 

Nosefix4.jpg

 

 

 

To fix these problems I used to apply a bit more LS, let it dry, then sand it down again.  My experience has shown that new LS applied to the older LS melts it and makes it unstable, so the process of adding more LS and fixing flaws can takes weeks to achieve a satisfactory result.  The quicker and easier solution is to fill all flaws with ordinary thin CA glue, apply accelerator, then sand it right away.  Before you do, it is best to open up the air pockets with a needle so that the CA glue can fill the entire cavity.

 

 

 

Here again is the nose after using CA glue to fill the gaps, then sanding it down smooth.  As before, I applied a dark wash to check for flaws, which seem to have disappeared- at least around the hole.  I will let this sit for another few weeks before painting to make sure there is no more additional shrinkage.  More on that later.

 

 

 

 

Nosefix5.jpg

 

 

 

 

 

 

Now I'll show another example on my last build of the Trumpeter A-10 kit.  The fit of the upper and lower wing halves at the wing tip have a very large and ragged gap on the underside.

 

 

 

 

 

Wings2.jpg

 

 

 

 

 

To fill the gap and adhere the wings together solidly, I applied a liberal amount of LS to both sides, then squeezed the wing halves together, followed by more LS to the outside of the join.

 

 

 

 

 

Wings38.jpg

 

 

 

 

 

 

After letting the LS sprue dry for about a week, I sanded it down, leaving a nice smooth finish.  After paint, things looked pretty darn good.

 

 

 

 

 

Panel-linewash6.jpg

 

 

 

 

 

Well, about 2 full months after paint, small depressions started to show up on the wingtips, making them look lumpy!    AAAAGGGHHH!  Apparently the thick application of LS was still drying months later- and shrinking- making it unstable.  I bet I fixed both wingtips at least 6 times over the course of the next 2 months before things settled down.  Lesson learned.  If I had to do this all over again, I would still use LS, but much less of it and I would repair any flaws with CA glue.  So here are a few tips that I now use:

 

 

 

Liquid Sprue Tips:

 

 

1)  Make the LS mixture as thick as possible, while still thin enough to apply easily.  The less glue, the less shrinkage.  If the mixture is quite “stringy†when applying, that is about right.

 

2)  LS will shrink approximately 40%, so double what you need in the first application to compensate for this.

 

3)  Totally the opposite of the above, try to use as little LS as possible.  It's a fine line, I know.

 

4)  Let LS dry for at least a week before sanding.  You can still sand it after only a few days, but due to additional shrinkage over time, you may be wasting your time.

 

5)  If you need to scribe a panel line through LS, let it dry for a month at least, otherwise your panel line will be ragged as the LS tears rather than cuts.

 

6)  Try to apply LS in one application.  Multiple applications of LS are unstable and they invite air pockets.

 

7)  To fill air pockets and other flaws, use thin CA glue to fill them rather than more LS.  For air pockets after sanding, poke a hole in them with a needle to make them wide enough to accept CA glue.

 

8)  For the first 5-10 minutes, LS wants to sink due to gravity, so if you want it to remain upright, rotate the model or part until it sets.

 

9)  If you used quite a bit of LS for whatever reason, give it an extra few weeks to dry before painting to make sure there is no more shrinking.

 

10)  The last tip is very obvious based upon the above.  Liquid Sprue can be wonderful stuff, but only if you are very patient and not in a hurry.  If you rush it, it will bite you!

 

 

Cheers,

Chuck

Edited by chuck540z3

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Chuck, this is terrific. Thanks so much for taking the time to post the tutorial, it isn't quick, but jeez it's helpful.

 

The shrinkage story is a familiar one, on my current project I got so frustrated with Tamiya white putty shrinking that I applied a boatload of it and let it set for eighteen months while I worked on other stuff ... but then not everybody's projects drag on so long as mine! ;)

 

Cheers

Jim

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Awesome tutorial, Chuck. Full of great tips and advice, wrought from hard-won experience. I plan on using liquid sprue to fill the panel lines on my Matchbox Emil kit, so I can rescribe and re-rivet the kit later.

 

Kev

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Thanks Chuck :)

 

I will need this tricks and advice when i build my CF-118 (Academy).

 

As usual your build threads are full of nice trick and are a joy to read (particularly the Cf-118)  :)

 

Stephane

Edited by S.Pelletier

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Thanks guys!

 

 

Awesome tutorial, Chuck. Full of great tips and advice, wrought from hard-won experience. I plan on using liquid sprue to fill the panel lines on my Matchbox Emil kit, so I can rescribe and re-rivet the kit later.

 

Kev

 

 

Kevin, why don't you just use thin CA glue to fill those panel lines?  I read the other LS tutorial you showed above and I think using LS to fill panel lines is a huge amount of work that is unnecessary and hard to do.  I can fill a 4 inch panel line with CA glue (use a toothpick or similar), add accelerator and have it sanded baby bum smooth in 1-2 minutes.  Really!

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Chuck, You make me laugh out loud!  Great tutorial.  Appreciate the time and effort you go thru to put these together.

 

Sincerely,

Mark

 

 

Ha!  I was hunting around for more pics of "Marge" the other day and quite by accident, I found the one above with the very same panel line gap as my model.  Too funny, considering you pointed it out just days before.  I think the real Marge should get an "inconsistent panel line" deduction, don't you?   :P

 

For those who missed it......

 

 

Front%20Nose5.jpg

 

P38-Marge.jpg

Edited by chuck540z3

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Kevin, why don't you just use thin CA glue to fill those panel lines?  I read the other LS tutorial you showed above and I think using LS to fill panel lines is a huge amount of work that is unnecessary and hard to do.  I can fill a 4 inch panel line with CA glue (use a toothpick or similar), add accelerator and have it sanded baby bum smooth in 1-2 minutes.  Really!

 

The main reason is that I don't have much luck re-scribing through CA. It tends to crack and flake, or otherwise produce a jagged line. Using accelerator makes it worse, as one of its side-effects is to make CA even more brittle than it already is. I figured the liquid sprue, once hardened-off properly, will be just like scribing through the original plastic. And those Matchbox panel trenches would require an awful lot of CA to fill! I'm happy enough to experiment with it. I can easily set the kit aside afterwards for as long as it takes.

 

Kev

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