Fuselage seem lines

Please can anyone offer any advice. I always get a small ridge when I glue the two halves together and cant understand why this happens.
I bring the two side together and apply one or two small pieces of masking tape to hold them in place. Then I run Tamiya Extra Thin along the seem applying a small amount of pressure as I work my way along the seem.
Once it has set ( a day later ) I find there is a small hollow ridge along the seem. I then have to fill this and sand it back.
I also find that because the ridge is so shallow the filler sands away and once more I am left with the ridge.
The only way seems to be to sand material down below / flush with the ridge but at the same time I remove surface detail. For information the filler is Deluxe Perfect Plastic Putty.
How do you guys go about joining your fuselarge together and just what am I doing so wrong.

I apply the glue to the mating surfaces. When these are pressed together molten glue squeezes out along the seam. When this has set hard, it can be sanded down, often meaning little or no filler is needed on the seam. It's not always perfect, but works ok.

Awins said:

Please can anyone offer any advice. I always get a small ridge when I glue the two halves together and cant understand why this happens.
I bring the two side together and apply one or two small pieces of masking tape to hold them in place. Then I run Tamiya Extra Thin along the seem applying a small amount of pressure as I work my way along the seem.
Once it has set ( a day later ) I find there is a small hollow ridge along the seem. I then have to fill this and sand it back.
I also find that because the ridge is so shallow the filler sands away and once more I am left with the ridge.
The only way seems to be to sand material down below / flush with the ridge but at the same time I remove surface detail. For information the filler is Deluxe Perfect Plastic Putty.
How do you guys go about joining your fuselarge together and just what am I doing so wrong.

Click to expand...

I used to have this problem, but as I applied different techniques, it fixed itself.
Can you post any pics?
Also, what filler are you using? I use epoxy putties and Gunze/Tamiya Grey type filler.
Cheers, John

As Colin wrote. Glue on the parts then press together. I find that Tamiya thin evaporates before a good weld can be made and you get that little "shrink" mark.
Ordinary liquid poly (I use Humbrol or Tamiya) works well just be on the look out for runs! If it should run, dont touch it as it will scare the surface. Just let it evaporate away and it will be almost unnoticeable.

Whichever cement you use it is important to apply sufficient to dissolve a layer of plastic in the join and to apply enough pressure when making the join to force an ooze of this out of the seam along its length. Then leave it alone to harden. When you later sand off the dried excess you should be left with a filled seam.
On longer seams, which I usually do in stages, it is very important to make sure that the mating surfaces are actually mating. If not you will inevitably left with an incomplete seam. If the surfaces don't mate you have to fix that issue first.
If for any reason I need to fix a seam I use CA glue because you won't sand it out of a seam and, crucially, it doesn't shrink as it dries. You do need to judge when to sand it, finding when it is hard enough to stay in the seam, but not harder than the surrounding plastic. There's no easy way to explain this, all glues are different and it is just a matter of practice and experience.
Cheers
Steve

I use old spruce warm with a lighter and stretch to desired length/girth. Hold it in place and apply Tamiya thin. Give it an hour and gently sand away the excess. Using the spruce from the kit your building will give optimum results.

I don't do many aircraft but I usually remove the locating lugs and do a butt joint which allows me to position the edges without a step.

Now & then I have the same annoying problem Alan. Usually it's just down to not applying the cement properly or as Steve said, not making sure the surfaces are mating sufficiently.
Sometimes too much clamping force can cause a gap to widen without realising it.

The best filler for me is superfine Miliput, the white stuff. It doesn't shrink as it cures, you can roll it into a thin 'rope' to nicely fill a gap & smooth it while wet with a damp cotton bud, which reduces the amount of sanding needed.

dubster72 said:

Now & then I have the same annoying problem Alan. Usually it's just down to not applying the cement properly or as Steve said, not making sure the surfaces are mating sufficiently.
Sometimes too much clamping force can cause a gap to widen without realising it.

The best filler for me is superfine Miliput, the white stuff. It doesn't shrink as it cures, you can roll it into a thin 'rope' to nicely fill a gap & smooth it while wet with a damp cotton bud, which reduces the amount of sanding needed.

Click to expand...

That's the same stuff that I use as well. Epoxy putties certainly are very good.
Another trick to fill gaps is to get an old tube of modelling plastic glue, put it in a glass jar, clip off old sprues and chemically melt the plastic. You then apply it to the gap. It then hardens and bonds to the same consistency of the plastic around it and can be sanded with no shrinkage. However, I only use this for really big gaps, as the hassle and messiness is not worth it for the smaller gaps.
John

I use the same method but using Mr S Cement to run down the seam. I the briefly rub the seam with a sanding sponge then run a bead of Mr Dissolved Putty down the seam. I make sure that dried properly then out comes the sanding sponge to sand it down. I look along the seam into a light to see if it has disappeared, sometimes you can see traces of the seam so I will use another bead of mr Dissolved Putty to finish it off.

Priming, with a good primer, is used for a final check of all seams and for any other build flaws before painting the base coat. Any further corrective measures can be done then, it is sometimes needed.