Sanding seams - which direction?

[zeus60]

When sanding seams, is it best to sand along the seam, or across it (that is, perpendicular to the seam)? Does it matter?

Just curious.

[Edgar]

As far as possible, I try to go across it, especially on a curved surface, like the top of a fuselage. If you continually go along it, there's every chance you'll get a flat line, which will only become visible when you paint, or, worse, you sand away the top of the (softer) filler, and end up with a trench, which needs filling again. One material, that I discovered several years ago, Micro Mesh, actually tells you to use successive grades at right angles to the one before; as well as giving a superb smooth finish, it helps to stop flat spots. They supply some grades on flat sticks, just like ladies' nail polishers.

Edgar

[zeus60]

Thanks for the quick responses!

Across the seam it is.

[Zmey Smirnoff]

Some LHS gurus recommended circular motion whenever possible. Works for me.

[kenlilly106]

Perpendicular as much as possible, parallel just removes the putty and makes a trench.

Something that improves the results is to use a sanding block or stick, I've found that if you use your fingers, they're softer than the plastic surface and will cause the sandpaper to follow any dip or the softer putty, so you'll end up making a dip in the putty that you'll have to fill and sand again.

Ken

Edited June 10, 2006 by kenlilly106

[trojansamurai]

Diagonally. I start about 15 to 20 degrees off from the seam and then repeat at -15 to -20 degrees.

This allows even sanding in both horizontal and vertical directions and prevents flats spots and indentations.

[David Walker]

Diagonally. I start about 15 to 20 degrees off from the seam and then repeat at -15 to -20 degrees.

This allows even sanding in both horizontal and vertical directions and prevents flats spots and indentations.

That's pretty much the technique I use also.

[zeus60]

Okay, I've thought of another question, related to my original question. Across the seam or diagonal is fine for the top and bottom of a fuselage, but how about where the top of the wing meets the fuselage? There really isn't enough room to go across the seam. Is there any special technique for sanding that area?

[pingu1]

but how about where the top of the wing meets the fuselage? There really isn't enough room to go across the seam. Is there any special technique for sanding that area?

Although I tend to use a circular motion, out of habit as much as anything else, I suspect that it doesn't really matter, so long as you're careful not to create flat spots where there aren't any, and that you use increasingly-fine grades of wet&dry, to eliminate the scratches made by the previous grade. I finish off with 1200-grade and a superfine sanding stick. Careful assemby can help to minimise the need for sanding and filling here, anyway. Try cementing the wing undersurface half to the model, and then the uppersurface halves, cementing first at the wing root, and using CA glue. With modern, well-fitting kits, you can often just use liquid poly for the join.

Unlike fuselage centreline joins, wing-fuselage joins normally occur where there is a panel line on the real thing. Therefore, so long as the join is smooth and properly filled, it's not essential totally to eliminate the join line itself. Indeed, there have been occasions when, having filled and sanded the wing-fuselage join, I've actually had to rescribe the join line. Re-scribing surrounding panel lines is normal.

Protecting the surrounding areas of the wing and fuselage with a couple of layers of masking tape helps to minimise collateral damage while sanding.

Cheers,

Chris.

Edited June 12, 2006 by pingu1

[David Walker]

but how about where the top of the wing meets the fuselage?

Here's another technique that works well specifically for that area. (though it's useful in other areas as well):

http://www.aircraftresourcecenter.com/tnt1...ding/tnt029.htm

[pingu1]

Here's another technique that works well specifically for that area. (though it's useful in other areas as well):

This method also works well with Superfine (white) Milliput (dampen the Q-tip with water), or, if the gap is only small, white glue (water again) or Tippex (isopropanol).

Cheers,

Chris.

[mossieramm]

but how about where the top of the wing meets the fuselage? There really isn't enough room to go across the seam. Is there any special technique for sanding that area?

Well, one way is to cut of a piece of sprue, stick a piece of blu-tac on the end, then stick a piece of sanding paper to the blu-tac, roughly mold it to form the area you want to sand and away you go. This has an advantage of not only being able to sand sharp corners, but inside areas where fingers don't fit as well.

David.

[madmike]

I hae just finished sanding the seams off of 4 1:144 main gear wheels and 2 nose gear wheels for my Challenger CL604 build. the nose wheels are 3mm in diametre...

heeeheeeheee..

One tool I find extremely useful is a Flex-i-file. This handy tool from Squadron allows sanding of curved surfaces without issues of sanding a flat area on a curved surface.

MikeJ