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Dummy leg pipe support template: coping a leg onto an elbow or a straight header

A dummy leg welded to the back of a 90° elbow needs a cope cut to the elbow's curved outside. FitterMaster's Dummy Leg screen gives 16 cutbacks for it: a 3" leg on the back of a 6" long-radius ell has a deepest cutback of 3/8", and the same leg on a straight 6" header needs 1/2".

3 min read · Updated 2026-09-15

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What is a dummy leg?

A dummy leg is a short length of pipe welded to a line, usually to the back of an elbow, so the line can rest on a steel support below. The end that meets the elbow has to be coped to fit its surface. This cope is traditionally eyeballed and ground to fit on the pipe; the template gets you most of the way there before the grinder ever comes out.

Why is an elbow harder to cope than a straight header?

On a straight header the cope is a plain 90° saddle. The back of an elbow is curved in two directions at once: it is a torus, not a cylinder, so there is no simple closed formula. FitterMaster solves each of the 16 points numerically on the elbow's real surface, with the leg centered on the 45° crown of the bend.

  • Elbow surface: (√(x² + y²) − Rc)² + z² = a², with Rc = 1.5 × NPS (LR) or 1.0 × NPS (SR) and a = elbow OD ÷ 2.
  • Each of the 16 lines along the leg (radius = leg OD ÷ 2) is traced in to that surface, and the cutback is the longest reach minus each reach.

How do you get the cope template in FitterMaster?

  1. Open Dummy Leg under Templates (Pro).
  2. Under Support, choose Coped onto: Straight header or 90° LR elbow (back).
  3. Pick the Size of the header or elbow and, for an elbow, its Series.
  4. Pick the Leg Size.
  5. Read the Cope Template: 16 numbered cutbacks, marked back from station 1, with a profile drawing.
  6. If the app shows Leg must be ≤ header OD., choose a smaller leg.

Worked example: 3" leg on a 6" LR elbow

Cope Template, 3" leg (OD 3.500") on the back of a 6" LR 90° ell
Station12345678
Cutback0"1/16"3/16"5/16"3/8"5/16"3/16"1/16"

Stations 9 to 16 repeat the pattern, with the deepest cutback of 3/8" at stations 5 and 13.

The same 3" leg coped onto a straight 6" header starts 0", 1/16", 1/4", 7/16", 1/2": a deeper cope, because a straight pipe does not curve away from the leg the way the back of an elbow does. Using a straight-pipe saddle on an elbow leaves gaps. Our take: if you're not sure which surface you're coping onto, pick elbow — a slightly shallow cope on a flat header grinds out fast, a gap on a curved one does not.

What the app does not do

  • It does not work out the leg length down to the steel. Measure that from your elevations.
  • The leg sits on the 45° crown of the elbow only; other positions round the bend are not offered.
  • No load, stress or support design. It is a cutting template, not a trunnion or support calculation.
  • No printout: you transfer the 16 cutbacks to the leg with a wrap-around.

Questions and answers

Can I use a saddle template for a dummy leg on an elbow?
Only on a straight header. On the back of an elbow the surface is curved two ways, so the cope is shallower; for a 3" leg on a 6" LR ell it is 3/8" instead of 1/2".
Does it support short-radius elbows?
Yes. Choose SR as the Series when the leg goes on the back of an elbow.
Is the dummy leg template free?
No, Dummy Leg is part of the one-time Pro upgrade.

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