Tank head gores
Domed heads on round tanks, vertical or horizontal. Snap line is the manual's method from two field measurements. True shape works out the exact curved gore for elliptical, F&D, parabolic and hemispherical heads. Not for flat heads; for a cone bottom use the concentric reducer.
Inputs
Method
Measured
Over the insulation, edge to edge. Twice the gore length.
Head type
Over the insulation
Rim of the head to the crown, over the insulation
Set from the diameter; change it if you like
0Tank diameter
0Heel (circumference ÷ gores)
0Width at the heel (+ ¾")
0Width at the centre
0Gore length (+ 3" lap)
0Line spacing (8 parts)
Gore pattern
Gore pattern
- Draw a centreline the length of the gore and divide it into 8 equal parts. Square a line through each and number them 1 (heel) to 9 (centre).
- Mark each distance from the table on both sides of the centreline. Join the marks with a smooth curve.
- Add 3" past line 1 for the lap that rolls onto the body.
- Trace out gores. Starter gore gets two crimp edges, finish gore two bead edges; lefts and rights shed water.
- Before the gores: a 4" to 6" band of jacketing on the end of the body, a circle for the centre, and two 2" to 3" bands to hold it. Pop rivet the centre to the band.
- On a horizontal tank, start at the bottom centre with the starter gore, work up both sides and finish at the top. Space the rivets with dividers.
Method: Advanced Metal Jacketing (IIIATF), Task C.3, Gores for a Tank Head. Gore count by diameter: to 3' 28, 3'–5' 32, 5'–8' 36, 8'–12' 40, 12'–20' 48, over 20' 52. True shape: gore width = head circumference at that line ÷ gores. Check the first piece on the job before cutting a batch.