That tricky seam....

[drdave]

On the bottom of a box section fuselage. Pup for example. How do you get rid of it? I have tried and tried.

[BLOWHARD]

Most times those aren't really square/flat, they're concave. That makes it hard to sand them flat. Plus the two sides usually don't match and end up stepped.
But the worse part is that this type of seam usually won't support itself and will continue to break open when you put pressure on it.

The best thing to is identify what problem or problems you have. Some bulkheads or shims inside the fuselage will take care of supporting the seam and making sure the two sides align correctly.
If you've got a stepped seam you can cut and ad some thin plastic stock and glue it in on the low side. Between sanding and filling with some sort of surfacer you'll do ok provided you don't crack the seam open and more importantly that you don't sand your fuselage out of square or shape. Major sanding can be really dangerous if you don't take the whole shape into account and focus on only one one area.

To give you a more detailed answer we'll need more details on what's going on with your Pup.

[buzz1941]

Also, sometimes there is actually a seam there on the real aircraft.

[BLOWHARD]

Too true Buzz ...although not on a Pup I think.
***But unfortunately seams in plastic models and seams in fabric covering (or any other real life scale seam) rarely ever look the same. A gap in the plastic is a mistake. Making that plastic one piece and then making appear as if it were two pieces is the best way to go. Or in other words, don't pass off shoddy workmanship as intentional.
Unless you've got an absolutely perfect fit and a consistently even gap you're better off filling and rescribing that seam.
Always think in scale and always make your work deliberate and intentional.

[Jessie_C]

You could superglue a piece of sheet plastic onto the entire bottom of the fuselage and then trim it so it meets the edges. Use .005" to keep from making the fuselage too deep. Superglue prevents the melting effect that styrene cement is prone to cause.

Jessica

[sean69]

Follow jessica's suggestion... You can get sheet styrene in almost paper thin thickneses..... Your other option would be.to hife it with stitching or something.

[Beto]

Jessica's approach of covering the complete bottom area with a thin sheet of plastic card works great also for models with a central bottom seam, like the Fokker DR1 or D-VII, since you can drill two rows of holes and sew a thin lenght of heat stretched sprue. A careful application of heat thightens the sprue.

[BLOWHARD]

Or...just do it right, add bulkheads or supports and test fit until it fits right and aligns perfect and you won't have any problems. Adding thin plastic is one of those last ditch type things after you've given up on everything else...unless you do that properly and remove the whole underside and replace it with with a new piece.
Still, if you don't it right you shouldn't have problems. No hiding needed, hiding things is a poor solution.
And again, hiding a central seam with stitching just isn't an option if we're talking about a Pup. It only works with Fokkers or similar.

[Jessie_C]

Originally Posted by BLOWHARD

Or...just do it right, add bulkheads or supports and test fit until it fits right and aligns perfect

To be fair that only works if the kit you're building is going to fit properly in the first place (and the Airfix Pup does fall into this category). If it's got two different thicknesses on each side of the seam then internal supports may not do much good. Sometimes you have to resort to extreme measures to salvage a build


Of course, there's a reason that the local IPMS members call me the Queen of Junk Kits...

Jessica

[eisenstein]

When prepping plastic for aluminum paint (so NOOOO seams!) I use liquid glue as usual, then, when it's good and dry, go over the seam with standard superglue (not the the super thin stuff) allied with the tip of a needle right on the seam. Let it dry and then polish away with the usual succession of grades of wet-and-dry. Looks perfect under Alclad. HTH

Martin