Masking cone shapes

[Gern]

Masking Cone Shapes.

Here is a quick guide to cutting masking tape to help paint tapered shapes. It is not absolutely accurate except for perfect cones but will give better results than trying to mask with straight tape.

You need to create a piece of masking tape that curves in a circle so that it will lie flat against the surface of your cone-shaped object (bomb, rocket, nose cone etc). The simplest way to measure how large to make the circle is to measure the distance from the point of your object to the point where you want your masking tape to start. Measure along the surface of your object – do not try and work out the vertical height!

Make that distance the radius of your circle and draw it on your masking tape.

Decide how wide your masking tape needs to be. It needs to be fairly thin or you will have problems fitting it to anything except a perfect cone shape. If you need to mask beyond this piece, just add masking tape as best you can – it does not matter how many pieces you have to use as you already have the straight edge you need. Assume you make your tape 2 mm wide.

Add this 2mm to the radius you used earlier and draw another circle using the same centre as before.

If you now cut out your two circles, you will end up with a thin strip of masking tape 2mm wide which you can place on your object. It should lie flat to the surface although it may not be perfect depending on how close your object is to a perfect cone. It will certainly be better than trying to use a straight piece!

You will need some sort of circle cutting device for the inside circle as this edge will be the one that defines your line; therefore it needs to be cut accurately. The outside edge is not quite so critical unless you want your tape to mask some sort of band such as the yellow stripe seen on US bombs. If this is what you want to mask, you will need to make the width of your tape the width of the band you want to mask.

You can calculate the length of tape you need by measuring the fraction of the whole circle needed, but it is much easier to lay the tape in place and cut it to the exact length when it is in place.

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[Gern]

Sorry folks. Forgot to mention that you need to cut through your circle of tape using a straight cut pointing towards the centre of the circle.

Place one of the cut ends on your object and lay the tape in a circle until the ends overlap. Make sure you've got it all straight and level where you want it and then cut through the tape somewhere in the overlapping section so you cut through two layers of tape. Point the line of your cut towards the point of the object.

By removing the top piece of tape from one side of the cut, and the bottom piece of tape from the other side, you'll make sure the two ends of the tape meet perfectly. You should seal where they meet with a little Klear or Maskol though, just to make sure your paint doesn't wick through the gap between the two ends of the tape.

Gern

PS Apologies for the poor drawing. Best I could offer this time of night!

[Gern]

I'll do the tape length formula for you anyway. As it is difficult to measure the accurate length of a curved line, we will use a different measurement to work out where to cut the masking tape.

The length of tape you need to go round the object at the point you want is the circumference of a circle at that point. To find the circumference, you need to measure the diameter. Without going into the mathematical detail, what you need to do now is to divide this diameter by the distance of the tape from the point (the original measurement you made). Now multiply this answer by 180. The number you get from this calculation is the angle you need to measure at the centre of the circle.

Gern

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