Encore-Perfect Seams
ByI’ve received a lot of requests for this as well as a link to my thread about “Reading the Seams” that I did on the Aeroscale forum. I will be reworking the thread to make it into an article which will appear here soon.
Perfect Seams – Part 1, by Gerald Voigt
As I evolved as a modeler one of the first areas I wanted to improve on was seams. Aircraft fuselage seams can be the most unsightly flaw in an otherwise great build.
A seam should be as smooth as the surfaces surrounding it, and be as realistic as its 1:1 master. I’ve found the best way to mate two components together is to weld them. Using a solvent applied through an applicator works best for me. It is only one method to apply solvents. You could also brush them on, but you take the chance of leaving brush strokes in the surface.
A smooth seam, like the one pictured here, allows for easy scribing of missing or removed panel features. A properly mated seam, like this one, has no pockets or holes along the seam. It’s as solid as the rest of the piece. Like a good weld in steel, it penetrates all the way through. Ever try to lay a decal over a dip or ridge on the surface? With this method, flaws can be repaired more easily with less damage to surrounding details and features.
We need to have some basic tools to use. Here is a picture of what I used to do this article.
Step one:
Removal of a part from the sprue itself
NEVER EVER break a part off the tree. 
Use a sprue cutter, cut with a knife while pressing against a safe surface (self healing pad), or saw it off. Super fine razor saws are becoming the rage. They provide a flush clean cut, needing only a tad of touch up, which can be done with a polishing stick.
Test fitting
This is something you’ll do a dozen times before even considering mating the two surfaces together. 
The two surfaces, especially on fuselage halves, must be square.this] [ not this > < or this } { or even this } [. You get the idea. If you are a modeler who wants exact scale, for example . the width of the fuselage and you test fit and tape together to check dimensions and find it too narrow, you can add a strip of styrene between the halves. To widen, you’ll need to sand it down, but I personally don’t go that far unless it is grotesquely obvious. From a couple feet away, who’s going to notice a 1/48 scale model missing four or less scale inches or about the width of two of your fingerprint ridges?
Alignment
True up the halves as best you can. Sanding on a full sheet of paper secured to a thick piece of plate glass or a metal surface is my method. I have an extension to an industrial table saw that is made of cast iron and machined. It is perfect for laying out sandpaper. I use magnets to hold the paper down while I sand.
Locator pins not locating? Lop them off with your X-Acto knife. They are not needed. Unless the model is one of those shake-the-box kits, the pins usually don’t accurately line up anyway. I use pieces of masking tape and my thumbnail to align the pieces. Once everything is lined up to my satisfaction, I start the welding process.
Welding
Welding plastic with solvents dissolves the plastic just enough to melt the two pieces in contact together, just as a welding rod does with metal. This forms a stronger, gap-free bond. My particular solvent of choice is Weld-on 3. When I need a cooler or slower solvent I use Tenax. I use a Touch-n-Flow applicator to apply the solvents. A brush can be used and at times its use is appropriate to attach small parts where you don’t want any solvent residue marks around the part.
More to come!
If you enjoyed this post, make sure you subscribe to my RSS feed!
An excellent article covering, what may be for many, basic ideas, but for novices or those rejoining the hobby gives sound info. I am looking forward for the following articles.
Nice start on the basics! I have two questions:
Don’t you find that the solvent sometimes migrates under the masking tape, especially Weld-on No. 3?
What grit sandpaper do you use for truing the parts?
As you are aware, liquid of any kind loves to travel the route of least resistance. I only use the tape to hold the components in place, releasing it as I work along the seam. This way I don’t have the tape inducing capillary action drawing the solvent under it. Also, if you do get solvent where you don’t want it…don’t touch it in anyway shape or form until the solvent has dried/cured. The biggest mistake is trying to correct the error while it and the plastic are wet/soft.
Once you have the seam secured, reapply the tape to hold the parts firmly together and move along to the seam doing small sections at a time. I will use panel lines or openings along the seam as my “sections” guide.
To flat sand on my steel table or thick plate glass surface, I use 500-800 grit depending on how much aggression I need, otherwise for models that don’t need as much aggressive sanding 800-1000 grit is enough to “true” the edges. I prefer a good quality wet/dry paper or emery cloth. In some situations I use a sanding stick making sure to keep it flat across the fuselage I am sanding to true up the edges so that they end up with mating surfaces like this ][ not this >< or this )( to facilitate at larger stronger bonding surface. This also helps eliminate the follow on need for fillers.
Excellent tips! I was wondering what approximate drying time do you give for your welds before sanding? I use Tamiya extra thin cement but it seems to take several days to dry sometimes.
With Weld-On #3 I can start sanding and polishing within an hour or less depending on how much saturation one must apply to soften the plastic to facilitate the “weld” to close completely. I routinely do slam or rapid builds of kits in hours compared to a project that takes days or weeks. You just have to find what you are comfortable with, but it is faster setting than other solvents because it is “hotter.”
July 24, 2008
Where do you get these touch and flow applicators?
TIA
They are available at most local hobby shops. You can also order them online from such retailers as Sprue Brothers.
Hey there GV! I have never (ever) tried the “welding” idea but from what I’m seeing and hearing, it’s a great thought. How do you rid the pieces of the common residue on the seam left over from the solvent? Same as with a ca adhesive I assume?
p.s.- gonna start that aircraft soon!
Kevin C.
I,m glad to find your site. I,m just beginning to use welds and I was curious as to what is the best method for cleaning your applicators when done? Thank You very much and I hope to utilize your site often in the future.
TNX, Joe
Joe,
Be sure to blow any access solvent out of the TnF (if that is what you are using) out. Do not store any solvents for any length of time more than an active building secession. The solvent will breakdown the material that holds the metal tubing in place inside the glass pipette.
Hi Gerald .. may I have permission to add to my Links section ?? .. well worded and clear instructions that go a long way to helping me feel more comfortable as a less than expert modeller ..Regards ..Rob Stevens
Sure Rob, it is my intent that my site help my fellow modelers whenever possible. To me that is the most rewarding part of modeling, sharing it with others.
Can you better describe how to use the touch and flow applicator? I must be using it wrong because anytime I have, the glue dries before it gets to the kit. Do you touch the glue bottle to the stem of the applicator?
Mark
Nice article, Gerry. This is timeless information. While basic, it is these preliminary basics that lay the foundation for good builds. I especially like the parts about truing on sandpaper. dispensing with the alignment pins and using capillary action to “wick” the cement into the joins.
Ive been doing all of this for years, but it is a nice refresher. I can say that those who find this to be “new information” will discover much better builds a result.
A good anything starts with sound fundamentals. Excellence is achieved by following sound fundamental practices and expanding upon them.