Seams: When does one give up?

I actually try and avoid filling as much as I can. I work hard to get the seam as close as possible then carefully sand and buff the seam away. Then if I destroyed any detail, I'll rescribe and if need be I'll use a metal scribing template so I don't mess it up. I really hate to use putty. Hate, hate, hate... Maybe I haven't found good putty yet. I also hate using gap filling CA to fill.

But there are times when you must use putty. Is this not true? Or are all the models I'm building lately just that bad?

Dana

The problem with putty is that it shrinks as it dries. All "ready to use" putties use a solvent, usually toluene, to dissolve the solids into a paste. As the solvent evaporates, the putty shrinks. What you thought was a perfectly filled seam ends up being too low. If you are going to use putty, you need to slighty overfill the seam and let it dry rock hard, preferably for several days before scraping and sanding. As an added precaution, I often carefully "paint" the dried putty seam with liquid model cement to make sure that there is good adhesion between the putty and the plastic, so that when I sand it, I don't have little flecks of putty popping out of the seam and leaving little holes to refill. All this work is the reason many people don't use putty and fill their seams with CA glue. But this has it's problems too. After filling with cyanoacrylate glue and cureing it with accelerator, you need to sand the seam very quickly before the CA reaches it's maxium hardness, otherwise the CA becomes harder than the plastic and the plastic will sand away faster the the seam, leaving the seam raised and the plastic around it concaved. I'm not sure there is any easy solution. Bondo is another way to fill seams, but it is a pain to mix small amounts and it stinks like mad. On the plus side, since it is a catalyzed product, there is no solvent to evaporate, hence no shrinking. And it doesn't have the hardness problem like CA does, at least when used in a timely manner.

Thanks for the encoragment guys. I don't usually have a problem with seams on fuselage halves. My latest case is trying to get the wing of a bronco to match with the wing root molded into the fuselage half. It's on top of the aircraft so it's obvious. Also, it's 1/72 scale so it's being easy to destroy detail. I'll keep at it thought.

Dana

I primarily use a scratch and pinhole filler and have discovered that there is a lot less shrinkage if I apply several thin coats and let it dry 24 to 48 hrs before sanding - I also put tape on either side of the area I'm working to protect the surrounding detail - Another item I use is typewriter correction fluid - works great on thin cracks (unfortunatly most of the seams and steps I get are far too large to use it with )
Then I start sanding w/360 sandpaper working my way up to the finest I can find (2000 grit) - If its a metallic finish (aluminum) I will finish with a fine automotive rubbing compound - any how thats what works for me

I also build 1/72 and gave up using putty years ago. I make my own filler by using a small amout of liquid cement and keep adding bits of styrofoam until I get the consistency I want (very thick). A small square Testors liquid cement bottle is very good to use for this, just get rid of the built-in brush. I usually apply this to the seam with the point of a round toothpick or a straight pin. The only down side to this method is that it takes a week or more, depending on the weather, to dry. But, since it is plastic, it bonds itself to the surrounding area; there is minimal, if any, shrinkage; and it sands at about the same rate as the kit plastic. Try it, you might like it.

As an aside to this, try thickening your liquid cement to about the consistency of pancake syrup for gluing large assemblies together, fuselage halves and wings. You will find that it won't dry, like straight liquid does, before you join the two pieces. Most times, a small bead will squeeze out of the seam which eliminates filling altogether. Just sand and rescribe if neccessary.

Pete

I try to get as close fit as possible by sanding the components.
Then I overglue the parts causing a molten plastic overflow. I do not touch it at all until dry. Then sand. That usually eliminates the need for filler and eliminates seams since there is a uniform material bonding all around. I also use mr liquid putty with good results.

I use Bondo Glazing Putty...nothing to mix, just use outta the tube.No shrinkage.

Dana,
I think thyamis probably has hit closer to home than any other on this thread. Just from a different perspective, I've found that when I have a seam that doesn't want to "go away", more often than not, there's a lack of a bonding agent holding the part together. I've experimented a little by taking a knife blade and gently sticking it into the troublesome seam. More often than not, the knife blade has easily parted the seam area. A little glue and drying time, as well as some sort of filler usually solves the problem.
Gip Winecoff

I prefer Testors putty to CA. Testors is my miracle worker, but yeah, always try and get a good fit first. Also, don't be afraid to lose detail! It's all rebuildable!

I guess my problem is fear of losing detail. I need to work on rescribing panle lines. With that, I have a few questions.

First, in the case of intricate panel lines that, well, you've removed, how do you know what and where to rescribe? Is it just a case of doing the research?

Also, I usually prime my models while filling seems. First of all, this in itself "helps" to remove the panel lines. Any comments on that? Also, is there any issue to scribing the lines after this prime is applied? Or should I attempt to remove the primer somehow?

Thanks guys!!
Dana

If you fear that you are going to lose delicate or intricate panel lines or detail, I've often used the old pencil rubbing technique from elementery school, where you use the edge of a pencil and lightly rub it across a piece of paper layed on the surface. The pencil "skips" the recessed areas, giving you an exact duplicate of the panel lines. If you have to re-scribe later, you have a perfect copy of the area to work from. As for filling seams, CA is my weapon of choice, using a sculpting tool along with several sandings to feather out the detail. You might want to invest in a scribing tool, available at most hobby shops. It makes the job much easier than using exacto blades, and you don't have to remove the primer.

demono69

You could also try epoxy-type of putties, such as Milliput. It does not shrink. You'll need a strong joint first as Milliput does not contain stuff that 'melts' the plastic so the joint you achieve with Milliput is 'weak'. The great think about this sort of putties is that they can be shaped before they get hard (a couple of hours), using a variety of tools (toothpicks are my favourite), fingers, and water.. So, no sanding required!

If you do use toluene based putties, a good way to avoid sanding is removing the excess putty with Q-tips and nail polish remover. But the shrikage problem is not resolved.

For very intricate panel lines, I just leave 'em filled, if they're so intricate and or tiny, they usually wouldn't show up in a small scale, anyway. Also, if the panel lines are pre-scribed, what I would do is use a scribing tool to deepen them. I usually make my lines twice as deep as the originally were. This way, no matter how much sanding you do(and believe me, I do A LOT of sanding and filing!), you still have the panel lines! Also, it allows for more wash to sink in, which makes the lines more defined!

apply the liquid glue with a small brush all along the joint and bind the pieces so as to let some glue come out of the joint.Let it dry and then sand it.It's the best way i think.However we all have to use puttie some time.Try Milliput or make one of yours!Mix talk and celulose varnish.Adding more talk the puttie seems like the common putties we use,adding more celulose the puttie will become more like the liquid putties such as Mr surfacer.Good luck!

QUOTE: Originally posted by dimmutal apply the liquid glue with a small brush all along the joint and bind the pieces so as to let some glue come out of the joint.Let it dry and then sand it.It's the best way i think.However we all have to use puttie some time.Try Milliput or make one of yours!Mix talk and celulose varnish.Adding more talk the puttie seems like the common putties we use,adding more celulose the puttie will become more like the liquid putties such as Mr surfacer.Good luck!

Just a question on this "universal technique". When people refer to applying the liquid glue to the joint, is this an appliction to each side of the piece and then pressing them together?

"Capilary action" also mistifies me. If I hold the two pieces together then the glue just stays on the surface of the two pieces.

I have read elsewhere about wedging an exacto blade inbetween the halves and then applying the glue.

Am I supposed to wedge the blade in a tiny bit instead of completely between the two edges?

Last of all, the type of glue.

I just bought this "Super Thin" 3second setting glue.

I have as yet to get the plastic into a molten state, so I am still stuck with a seam. I am trying to practice on another model kit to get this right.

Anyway, frustration is the word. I have been to Naplak's site and read through the forum there and I have looked through this Website and someone else's website for help on the subject.

All say about the same thing, but I have not been able to duplicate the result.

Hi ngc7293. I use Ambroid ProWeld but other companies make similar products like Tenax. This glue is very thin and flows into the seams and melts the plastic together. If you squeeze the parts together some of the melted plastic flows from the seam and fills in spaces. Once this is dry you can easily sand the seam away if you have a well engineered kit and have the parts positioned well. Watch out for this glue though. I manage to spill a bottle every couple of months and if it hits plastic parts it'll make an unhappy mess.

Not to be harsh, but you have not said anything I have not heard already (except for that glue brand). Let me be a little more descriptive; perhaps that is what I am not doing.

Here I have a model of a V-22 Osprey 1/48 scale. The inside has been glued in place on one half of the fuselage.

Now what? It sounds like you are saying that I hold the pieces together. The glue is supposed to run down the line where the two halves meet and then seep inbetween them. The plastic is then supposed to melt a little and I am supposed to squeeze the parts together.

If I have a "perfect" fit, how is the glue going to seep?

I'm sorry, but I have tried this with another thin glue and all I get is a coating of glue on the top surface of the two halves.

If the halves fit too well you might have to release some of the pressure so that a small gap appears, but a very small gap.

ngc7293,
Looks like we may have not been completely clear. Sorry. You don't hold the pieces together so that they touch, but hold them together so that there is less than a 1/32" or so gap between them. Now put some liquid glue in the gap between the halves. If the pieces are close enough together, you'll see the glue run down the gap. This is the capillary action everyone has mentioned. Wait several seconds, close the gap and gently squeeze the halves together. Some glue will be forced further down the seam, while the remainder will ooze out between the halves along with styrene that has begun to melt. Make sure your halves are properly positioned, wait for the glue to dry thoroughly, then sand and Voila! Seam filled!
If you are doing a lengthy piece like a fuselage, you may have to do it in sections to get complete seam coverage. Just take your time, and move methodically down the seam a little at a time.

After everything has dried, there may be a small gap left in the seam (due to no glue, poor fit, etc.). I'll then fill and sand. If the seam is still present after that, and still doesn't want to go away, I'll take a #11 blade and carefully probe the seam: Stick the tip of the knife into the seam and GENTLY twist the blade. If the seam hasn't got any glue in it, it will open up. Holding the seam slightly open with the knife blade, put a little liquid cement on a brush a put it in the seam. Release the knife blade, and the seam will close, releasing glue and styrene as mentioned above. If the seam doesn't open up, remove the blade, throw in a little putty or filler of your choice, wait 'til it dries, then sand.

This is only ONE method for dealing with these things. I am sure there are better ideas from smarter individuals than me, but for me, this is what works in some situations. Experiment some to see what works best for you.

Does this make more sense to you?
Hope this helps.
Gip Winecoff

I think I understand now. This was like walking into a den of computer geeks. People talking about things you don't understand but they have an understanding and forget about those "outsiders"

QUOTE: Originally posted by ngc7293` I think I understand now. This was like walking into a den of computer geeks. People talking about things you don't understand but they have an understanding and forget about those "outsiders"

Ha! You're not kidding!

I remember when I first read about "Evergreen stock." I had no idea what it was, but it sounded like it was made of wood. The pictures in the magazine, however, showed white plastic. I finally learned that Evergreen is the name of the company that sells sheet plastic and plastic structural shapes that a lot of people use for scratch building (http://www.evergreenscalemodels.com/). That's just one example of how I've been confused over the years.

Regarding gluing so that you don't have to fill seams, check out this page. It has some good pictures to go with the description:
.
http://www.aircraftresourcecenter.com/tnt1/001-100/TNT068_gluing_Wilder/tnt068.htm
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It's from the Aircraft Resource Center web site's (http://www.aircraftresourcecenter.com/) Tools and Tips page..

Regards,

-Drew

Excellent link, Drew!

Gip Winecoff

Yeah, it's a great site. I tried this technique for the first time on the F-4J I'm working on now. It worked pretty darned well. I was really surprised. I didn't get it 100% right, so I had to use a wee little bit of filler, but that went pretty well too.

I think one of the things I did wrong was that I let up on the pressure after I had gotten the melted plastic to squeeze out. So I had a good bead for most of the seam, but a couple of sunk in spots where I should have had more pressure.

Live and learn.

Regards,

-Drew

What about plugging a hole or window area with plastic. That's not a seam that will "melt away".

Is this a time where I have to learn how to use putty?

Probably, unless the fit for the replacement part is perfect. For round holes, you can use styrene rod the size of the hole, or stretch some sprue to fit. Use a little liquid cement, glue it in place, cut as flush as possible and hit with a little sandpaper. If everything goes OK, you shouldn't need any filler. Follow the same procedure for a window. Cut some sheet styrene to the approximate shape, fit as flush as possible, glue in place, let dry, then go back and see if you need any filler. You can use CA glue or putty to even things out. The trick to reducing the amount of filling and sanding is to fit your plug as accurately as possible to the opening.
Hope this helps.
Gip Winecoff