# HOW DO i SOLVE THIS PROBLEM



## 650bill (May 23, 2011)

I bring this problem to the group in hopes someone will tell me how to solve it. Here is the probem. I have spent a lot of time trying to solve this problem, but have been unsucessful so far.

When building a model and after joining the 2 halves of the fusealuge, or for that matter, any two halves, even after dryfitting it together with masking tape to be sure the 2 sides fit together perfectly, I find that I am still left with a problem after gluing, and I use liquid plastic cement when gluing.

The problem is a fine hair line is still visible after gluing the 2 halves together, no matter how careful I am. I file and sand the areas, using the finger nail test. Meaning that when I can no longer detect the joint with my finger nail, I am ready to paint. After I have painted over the jointed area, a fine line appears where I had previously filed and sanded.

Painting doesn't cover up this line, and I don't want them showing up on my models becase it looks tacky. Using body putty doesn't help because after painting one can see where the body putty was applied.

Anyone got any suggestion on how to get rid of the joining lines.
Thank you, 650bill


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## djnick66 (May 2, 2008)

650bill said:


> Painting doesn't cover up this line, and I don't want them showing up on my models becase it looks tacky. Using body putty doesn't help because after painting one can see where the body putty was applied.
> 
> Anyone got any suggestion on how to get rid of the joining lines.
> Thank you, 650bill


Putty and sand down with fine wet and dry paper until its smooth. This is useful to blend in parts that don't fit like a wing root, tail plane, scoop, etc. that sticks on but has gaps and seams.

This isn't a plane but its the same idea...

Aurora's Zorro...



















Airfix B-24 Liberator has some areas to smooth out for sure










Defiant NF had some horrible gaps to smooth out










Frog's DH Hornet needed a step filled in where one side was a bit off










Poor fit on a Messerschmitt jet fixed with putty and sandpaper


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## 650bill (May 23, 2011)

*Thanks*

Thanks for the lesson John. In the past, I had naturally applied puddy, but after sannding and painting, I was still able to see where I had applied the puddy. I am guessing that I didn't sand down far enough and have not used wet sand paper.

As I understand what your are saying is that puddy can be used on a seam even though there are no gaps, just fine lines. I know that what you say is correct because I have seen many other examples of your body work and they are perfect.

I guess I just need to sped more time and practce now that I have the right direction.

Gaday to ya mate, 650Bil, from the land of the Canadian Border


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## MightyMax (Jan 21, 2000)

Dave gives good advice. 
I might add that if you don't have this tool you need one.
A Flex-I-File. 
Makes sanding wing leading edges and other curved surfaces a treat!

Cheers
Max Bryant


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## djnick66 (May 2, 2008)

I use mostly black wet and dry sandpaper. You can buy it by the sheet at places like Ace Hardware. I will use a more coarse grit to cut down the putty quickly, then use finer grades to finish the seam. You don't want to oversand and remove all of the filler, either.

Bondo Red Glazing Putty is easy to sand but sometimes a bit too easy and you remove too much. I use a lot of Squadron Green Putty (available at Hobby shops). Its been around forever and is a decent general purpose filler. You can see both in the above photos. I actually use two or three different types of putties. Sometimes also you have to work on the seam two or three times.


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## 650bill (May 23, 2011)

*do I have the correct grit*

Hi, its me again. I have wondered if my choice of grit is correct. I use 100, 220, 320 ad finally 600 for my final work. Should I use a finer grit than 600 for wet sanding? I will purchase the types of puddy you mention because I have found that the one type I am using is not sufficent enough. It doesn't provide the variables that I need to accomplish perfect quality finish.

Now John, here is one more step I wonder about. Working in the automotive field for 35 years,I spent a lot of time around the body shop. I noticed the body repairman would use a red color paint after they had finished their bonding and sanding. This red coat would expose any imperfections in their puddy and sanding. Have or do you use this same step in your final preparation?
650bill


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## agentsmith (Mar 27, 2005)

I agree with djnick66 about filling and sanding seam lines.

I go one extra step after the putty is sanded down, I brush paint some paint on the seam line and wait for it to dry, after the paint is dry I wet sand with fine grade sandpaper to smooth and blend in the area that was filled with putty as a final check to see if the model is ready for painting. If you do this you will not have any nasty surprises waiting for you when you go to paint your model. 

Agentsmith


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## 650bill (May 23, 2011)

*what grit*

Agentsmith--what grit do you use for wet sanding. Bill


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## Skymods (Feb 5, 2001)

The red paint you mentioned was probably primer. Are you priming your model before painting?


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## djnick66 (May 2, 2008)

100 grit is wayyyyyyyyyyyy too rough for modeling applications. use maybe 220 to rough something down but 400-600 for final work. If you are doing a natural metal finish, which must be super smooth, you can polish the model with 1000 grit or fine polishing creams and a soft cloth. 

Painting a real metal car is a bit different than plastic. Metal needs to be primed because it will rust or oxidise, and paint will not stick to bare metal. Usually a couple kinds of primers (sandable and etching) are used to give a good base for the color coats.

On a model, you can use primer. In this case, it is to help show any flaws in your putty work, provide an even color to apply your paint over, and in some cases to help with adhesion. Acrylic paints often do not like to stick to bare plastic... it is too smooth.

Here is my Zorro horse with some Squadron green putty










I then sprayed it with a light coat of white primer










The horse is now base coated with Tamiya Rubber Black, which is a very very dark grey










And then the final finished model. The figure was puttied, sanded and primed in a similar fashion.










Here is the Airfix Bismarck (a very ill fitting kit !!)










Since the putty is a bit dark, and the lower hull has to be painted red, it was primed first with white. The finished hull...










This M4A3E2 "Jumbo" assault tank was primed with Krylon spray primer










The shell of this M4A1 Sherman's turret was primed becuase I had done extensive sanding, texturing, and reshaping. So I wanted to make sure it was good before I added all the extras. I added the casting seam around the rear bottom edge of the turret.










Hope that helps

David


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## agentsmith (Mar 27, 2005)

650bill,

For most sanding I use medium grit sandpaper, for the final bits of sanding on the seams I use sandpaper much finer than 600 grit. Sorry I don't remember the exact number.

Agentsmith


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## RMC (Aug 11, 2004)

......remember, all fillers tend to shrink regardless of what they say !

when I get a stubborn seam,i apply a little bit of crazy glue,let dry and sand smooth
(it works because after the crazy glue dries,it will not shrink)


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## SteveR (Aug 7, 2005)

It's a good idea to keep an eye on the Krazy Glue, and not to wait too long before sanding, as it can dry harder than the plastic. Test on scrap.

And I usually end with 1200 grit and water for smoothness.


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## whitewarrior (Nov 29, 2008)

When having a fine line to putty I sometimes file it out some to where it is now a V shape. Seems to work better for me and hold the putty better. Am I the only nut who does this? Go ahead, I can take it! I also have puttied a seam, let it dry (or so I thought) then sanded it. Done, right? No! The next morning I discover the line has "sunken". All I can think of is that the putty was not completely dry underneath.


Terry


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## AJ-1701 (May 10, 2008)

Great tips here :thumbsup: Seams and joins have alway been a bug bear of mine too :freak: I haven't tried the green squadren putty though I also use a product over here called timbermate. It is designed a wood filler but it's water based has very little shrink and is very easy to sand and when its dry and I'm happy with the fill I add some super glue to to harden it up. But I'll get myself a tube of the green and give it a go too.

Cheers,

Alec.


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