Help! Seams won't go away!

The seams that give me the most trouble  are the ones where one side is higher than the other. You cannot just sand the high side down to match the low side without creating other problems. These have to be feathered with putty which I have to keep at over and over.

Question on this: after you apply `whatever`method, how do you deal with covering up raised details like rivets and raised panel lines. This is a continual frustration for me...sanding away detail to get rid of the seam!!

Often times I find that the putty didn't really fill the seam so much as bridge it. So, as I'm sanding it later, the gap under the putty is revealed. In this case, it may appear that the seam is reoccurring but in reality I'm just sanding the void open. That's where practice, practice, practice comes in. Gotta make sure your putty is filling, not only spanning, the joint.

And, as others said, glue strips of thin styrene into wider gaps before puttying.  

Gamera

BTW make sure the seam is actually cemented together. I've puttied and sanded seams a dozen times and they would not go away. Found out later that the seam wasn't glued and when I'd put pressure on it with the sanding stick it would 'pop' and I'd end up with a crack again. Worst situation was on a 1/72nd B-29 - the long seams on the top and bottom of the fuselage kept popping loose over and over- took me a while to figure out this was what was happening.  

Yes!  This is the big problem with the original post. If the orignal glue joint is not good enough, no amount of filling will be satisfactory.  The glue joint MUST hold.  Then you can worry about fillng the remaining seam.

For really stubborn, wide seams, I'll run a couple of strips of tape down both sides of the seam, then lay the putty in the trough, leveling it with a putty knife or piece of plastic card stock.  Pull the tape, let it set, then hit it with a sand paper board.  It seems to do a better job of hiding the seam, and not making a big mess down the side of the seam.  

Gene Beaird,

Pearland, Texas

I have no luck with CA so I tend to use putty.

Also, if using putty or something like it, mask the area to get it on as small a part of the model as possible. It makes a step, but that can be sanded off.

Sometimes (slowly- both of my Dremels have good speed control) but more frequently I just grab the brush in my fingers and use it like a conventional file card.  Hardest thing to clean out is solder when I have been working with soldering brass.  Plastic and filler clean out fairly quickly, primer paint is somewhere in between.

Do you actually run the dremel with that wire brush on the file or just use the brush by hand? I happen to have one of those...

JimNTENN

To keep files clean you can use a file card that you should be able to get at any home improvement store. But, as an alternative, I usually wipe the file off right on my pants. That works good enough for me.

File cards sold at most hardware stores tend to be too coarse to really do a good job on fine needle files. I found a dremel wire brush wheel with very fine wire, and use that to clean my needle files.  Also occasionally use one of those 3M kitchen scouring pads.

To keep files clean you can use a file card that you should be able to get at any home improvement store. But, as an alternative, I usually wipe the file off right on my pants. That works good enough for me.

Wow guys thanks SO much! I'm sorry I haven't been as involved here as I should be - for some reason I stopped getting email notifications of responses.

I think my biggest problem is trying to rush through the seam work and not letting things set up, in combination with using too much pressure and sanding too much. I have been trying to experiement with some of the putties that can be "wiped" down (Tamiya or Mr. Surfacer with Lacquer or Perfect Plastic with water) but these seem to be a little bit finicky for me.

Patience, gentleness, and learning when to stop sanding are going to be my keys to success, it seems like. I am working on an F-14 and F-18 and they both have plenty of seams that I am working on for some good practice.

To answer one of the questions - I have used CA Gap Filling, Perfect Plastic, Tamiya white, and Mr. Surfacer 500. I tend to mix these up depending on the type of work I am doing.

Also, when you guys sand, say, Tamiya or Perfect Plastic, what do you use - straight sandpaper or pads/sticks? I am wondering of the "padding" of paper/sticks is hurting or helping, or if regular paper with fingertip application would be any better.

Also, how do I keel files clean? As Don said, they clog up incredibly quick but I do love using them for heavy work...

There are some really good ideas and suggestions here but I have a couple of observations to make.  If you use CA, get it filed/sanded down as soon as possible after it sets up - the longer it sets, the harder it gets (I once applied a mixture of baking soda and CA to the underside wing joint to an  1/72 and then went to summer camp at Fort Carson, Two weeks later came home and the joint was like a piece of granite!)  And if you need to apply a coat of putty that is more than 1/32 of an inch try to apply the putty in 2 or 3 thin applications instead of one thick coat (let each set up before applying the next coat).  

It takes me a week to build a quarter scale fighter from start to finish. Depending on the kit the equivalent of three days of that time is spent on seams. My current build is the old Monogram TBD-1. I started it Saturday afternoon and yesterday it went through it's second and third rounds of seam work. I haven't worked on it today but the next bench session will be the forth and final round of seam work. Speed isn't a problem.

The one part putty I use sets in twenty to thirty minutes, the same as the primer I use, so an hour after I apply it (depending on how long it takes to smooth the putty) I will know if I need more work on the seam. I use auto body glazing putty and krylon primer.

Hello!

With all due respect, you have to be careful with that - if you have too much patience, you may end up spending months on one seam in your model. If you have the misfortune and fill a rather large seam with generally avaialble one component putty, you can wait two weeks just to discover the seam shows through the primer. And again. And once more. Six weeks gone. That's how the thread started in the first place. Some people use two component putties - you just slap them on, sand wet and hopefully you're done in just one evening - can be done too!

But of course practice and patience ARE very important when modelling. Let's just not waste the opportunity to do things better and faster.

Have a nice day

Paweł

I used to battle seams then I figured out the secret.

Patience.

Work the seam with your desired method and then leave it alone for a day to fully cure. Observe the seam for your desired look and then repeat as often as required to make it disappear. Wait another day for everything to cure. Repeat.

Once you are happy with the work primer it and let the primer fully dry, then reinspect the seam. Primer will reveal any problems. I've even used BMF (Alclad) as a primer because nothing shows shoddy seam work like BMF.

When the work is correct it may still look bad. You may see feathered lines where plastic, primer, and filler material are all visible at the same time, yet the seam will fully disappear under paint. When in doubt, primer again.

Patience, practice. You'll get it.

if it looks like a tight fit, say a gun barrel, use a lot of plastic cement and let it oozeup and dry, then scrape it down and sand. i use 3M body putty a lot (not the 2 tube version). if the seam is at a mard to reach place like between the fender and side of a tank hull, i run white glue along it and wipe it down with a damp Q-tip. may take 2 or 3 runs because the glue shrinks but makes a nice fill and paints well. any NATO tank barrel that goes south can be draped with a camo net. i have done that a few times.

Filling is a technique I am far from good at, so really appreciate all of the great tips and advise here. Great thread and thanks, Todd, for bringing up the subject.

For very thin short seams I use gel CA.  With the gel stuff you don't need the baking soda.

Me too seams drive me nuts there is one more method I'll try on my next plane build it usese baking soda and thin super glue. Acording to video I saw you fill seam with baking soda then apply thin super glue,the baking soda act just like accilrator and dries the super glue as soon as they mix. Then you can sand and finish seam right away.             ON BENCH REVELLE F4 PHANTOM C/D 1/48             ACESES5        

I usually use needle files to sand filler in seams.  Downside is it clogs files quickly and you have to keep cleaning them, but ithey do a great job. They take off material rapidly, but leave smaller marks more like very fine sandpaper.

I've had good luck using the regular ole Tamiya Grey putty. I smooth it out with acetone (nail polish remover) and Q-tips. Let it dry. Sand it smooth with Micromesh (usually 3200)

What type of putty or filler are you using? I find Gunze's white putty or Mr. Dissolved putty very easy to sand and blend in, without shrinking or flaking off. Its all I use to fill in sink marks or other suface defects.

Thanks guys I will keep trying with some of your suggestions. My biggest issues aren't actually joint seams but actually the type of stuff like filling panels and gouges in the surfaces... but It's all the same really. But like I said I will keep trying! I think I am just being too aggressive, probably.

The trick to sanding cured CA is to use a flat jeweler's file to get the bulk of the cured CA then the sanding stick comes in.

In addition to all this good advise consider that sometimes the sanding medium is too coarse or you may be applying too much pressure which can actually sand filling material out of the seam ever so slightly.  Remember that putties and paint fillers like Mr Surfacer are not as dense as the plastic and will sand out more rapidly.

Next time try using a finer grit sanding stick or pad and use very light pressure.  Wet sanding also works better IMHO.  It takes longer using fine sanding mediums but typically you'll get good results.

And I'm really talking about sanding over putties and Mr. Surfacer type fillers.  With CA glue you do need to be a bit more aggressive.

As people above have mentioned, there are two problems.  First is the seam is not adequately cemented/glued together. In some cases it can just be reglued. In other cases, some kits do not have strong enough parts and maybe too thin of a gluing surface. In some cases you can use strip styrene to make a "flange" inside the joint that will, after the joining, bridge the seam making it much stronger.

The second problem is filling the seam but not level.  When applying the filler, make sure you mound it up a bit higher than the surrounding surfaces.  Be sure it has fully set.  Then, when you sand or file the seam you can get a decent looking seam.  With some fillers that take awhile to set and shrink a lot, you may need two coats of filler.  Primer should reveal if the seam is properly filled and smooth before you apply color coats.

The best method I have found is using either Tenax or Plast I Weld applied with the Touch n Flow applicator. For joining fuselage halves as an example, I run the tip of the Touch n Flow applicator along the seam and within a few seconds, the glue melts the plastic and creates a solid join like welding it together. I squeeze just enough to force a little ridge of plastic on the seam and when dry, it's easily sanded and buffed to a complete invisible join. If you have a larger gap then thick CA and even mixed with some  micro balloons to create a thicker more filling goop will work. When dry, sand out to a smooth join.