Internal area including hearth and piers is
Internal surface area = area of circle = π r², where r = internal radius of whole building, c = internal radius of central area
Surface area of roof = area of conical central roof + area of corbelled edge
= area of curved surface of a cone + area of a circle (with centre part removed)Hornish, South Uist Point Structure 1 (Barber 2003)
= (½(circumference of base) X (slant height)) + (π r²(for whole area) - π c² (central area))
= ½(2πr X l)
= πr √2 (r²+h²) [l = √2(r²+h²), for 45°pitch roof, h = r]
= π r √(2r²)
= π r √2 r ≈ Approx. 4.44r² + (π (r²- c²) Maximum rafter length = √2 r², where r is radius or half the breadth
Internal diameter 7.5m, piers perhaps 7 (0.4 by 1.4), central area perhaps 4.7m
Internal surface area = π r² = π 3.75² = 44.2 square metres - area of piers (= 7(1.4 by 0.4) = 3.92 square metres) = approximately 40 square metres
Roof surface area ≈Approx. 4.44r² + (π (r²- c²)
= 4.44 (5.5) + (π(14.1 - 5.5) = 24.5 + 27 = 51.5 square metres total
Conical central part surface area = 24.5
Max rafter length = √(2 r²) = 3.3 metres
Bruthach An Tionail Ard, Kilpheder, South Uist (Armit 1996, 137)
Internal diameter 9, central area 5, 11 piers
Internal area = 63.6 -approx 10 = 53.6
Roof area = 27.8 + 44 = 71.8
Central area = 27.8
Rafter = 3.5
Alt Chrisal, Barra (Branigan and Foster 2000, 151)
Free-standing wheelhouse at Alt Chrisal Barra (Branigan and Foster 2000, 151).
Internal diameter of approximately 6.3m, central area 3.7m diameter.
Internal surface area = π r² = π 3.15² = 31 square metres - area of piers (= 7(0.8 by 0.4) = 2.24 square metres)
= approximately 29 square metres
Roof surface area ≈Approx. 4.44r² + (π (r²- c²)
= 4.44 (3.4) + (π(9.9-3.4) = 15.096 + 20.4 = 35.5 square metres total
Conical central part surface area = 15.1
Max rafter length = √2 r² = 2.6 metres
Allasdale wheelhouse, Barra (Young 1953)
8m internal diameter, central is 5m. Originally nine piers (each perhaps 1m by 40cm
Internal surface area = π r² = π 4² = 50 square metres - area of piers (= 9(1 by 0.4) = 3.6 square metres) = approximately 46 square metres
Roof surface area ≈Approx. 4.44r² + (π(r²- c²)
= 4.44 (6.25) + (π(16-6.25) = 28 + 31 = 59 square metres total
Conical central part surface area = 28
Max rafter length = √(2 r²) = 3.5 metres
Sollas wheelhouse, North Uist (Campbell 1991)
10.9 m internal diameter, 7m central area
13 piers - each approximately 1.2 by 0.4m
Internal surface area = π r² = π 5.45² = 93 square metres - area of piers (= 13(1.2 by 0.4) = 6.24 square metres) = approximately 87 square metres
Roof surface area ≈ Approx. 4.44r² + (π (r²- c²)
= 4.44 (12.25) + (π(16 - 6.25) = 54.4 + 55 = 100 square metres total
Conical central part surface area = 54.4
Max rafter length = √(2 r²) = 5m
Cnip 9-1 wheelhouse, Lewis (Crawford 2002)
6.7 m internal, 4 m central, 8 piers (1.2 by 0.8)
Internal surface area = π r² = π 3.35² = 35 square metres - area of piers (= 8(1.2 by 0.8) = 7.68 square metres) = approximately 27 square metres
Roof surface area ≈Approx. 4.44r² + (π (r² - c²)
= 4.44 (4) + (π(11.2-4) = 17.8 + 22.6 = 40.4 square metres total
Conical central part surface area = 17.8
Max rafter length = √ (2 r²) = 2.8 m
Cnip 9-2 wheelhouse, Lewis (Crawford 2002)
Diameter = 6.7m. Hypothesise central diameter 4m + 8 piers as with Cnip 9-1
Figures the same as 9-1.
Traigh Na Berie/ Cnip 12 (Crawford 2002)/NMRS Number: NB13NW 4.00
Crawford records as the same size as Cnip 9-1 and 9-2
Figures therefore taken as the same as Cnip 9-1. Entry in NMRS suggests in may be larger.
A'Cheardach More, Drimore, South Uist (Young and Richardson 1960)
Internal 12.192, central 6.7, 11 piers (0.4 by 1.5)
Internal surface area = πr² = π 3.35² = 113 square metres - area of piers (= 11(1.5 by 0.4) = 6.6 square metres) = approximately 106 square metres
Roof surface area ≈Approx. 4.44r² + (π (r²- c²)
= 4.44 (11) + (π(37-11) = 48.8 + 81.7 = 130.5 square metres total
Conical central part surface area = 48.8
Max rafter length = √(2 r²) = 4.7 m
Garry Iochdrach, North Uist (Beveridge and Callander 1931)
Internal diameter 7.8m, 6.2m central area, 7 piers (0.95 by 0.45)
Internal surface area = π r² = π 3.9² = 47.8 square metres - area of piers (= 7(0.95 by 0.45) = 3 square metres)
= approximately 45 square metres Roof surface area ≈Approx. 4.44r² + (π (r²- c²)
= 4.44 (9.6) + (π(15.2-9.6) = 42.2 + 17.6 = 59.8 square metres total
Conical central part surface area = 42.2
Max rafter length = √(2 r²) = 4.4 m
Bac Mhic Connain D (Beveridge and Callander 1931)
Internal diameter 8.5m, central approximately 4m, 8 piers perhaps 1 by 0.4
Internal surface area = π r² = π 4.25² = 57 square metres - area of piers (= 8(1.0 by 0.4)= 3.2 square metres)
= approximately 54 square metres
Roof surface area ≈Approx. 4.44r² + (π (r²- c²)
= 4.44 (4) + (π(18 -4) = 17.8 + 44 = 62 square metres total
Conical central part surface area = 17.8
Max rafter length =√(2 r²) = 2.8 m
Cnoc a Comhdalach, North Uist (Armit 1998, 259; Beveridge 1911)
Approximately 23ft diameter, 10ft diameter central area. 7 piers, 4ft by 1.5ft
Area = 38.6-7 = 31.6
Roof surface area = 10.5 + 31.4 = 41.9
Central roof area = 10.5
Rafter = 2.5
Eilean Maleit, North Uist (Armit 1998, 260)
7.3m diameter, 3.4/2.7m central section, nine piers (approx 1 square metre each?)
Area = 32.9
Roof surface area = 10 + 28.4 = 38.4
Central area = 10
Rafter = 2.1
Clettraval, North Uist (Scott 1948)
8m diameter with 4m central area, 8 piers
Area = 50.3-8? = 42.3
Roof surface area = Approx. 4.44r² + (π (r²- c²)
= 17.8 + 37.7 = 55.5
Rafter = 2.8
The Udal, North Uist (Parker Pearson and Sharples 1999, 6)
A - 10 metres diameter, 5 metre central diameter, 10 piers
Area = 78-10? = 68
Roof surface area = 27.8 + 58.9 = 86.7
Rafter = 3.5
B - 10 metre diameter, 5 metre internal diameter, 11 piers
Area = 78 - 11? = 67
Roof surface area = 86.7
Rafter = 3.5
C - 7 metre diameter, 4m central area, 8 piers
Area = 38.5 C 8? = 30.5
Roof surface area = 17.8 + 25.9 = 43.7
Rafter = 2.8
Foshigarry, North Uist (Crawford 2002) NMRS Number: NF77NW 5
A - 11m diameter,
Area = approximately 90?
B-11.9m diameter, 13 piers
Area approximately 105.7-13? = 92.7
C-10m diameter, 12 piers
Area approximately 78.5-12? = 66.5
Uamh Iosal, Usinish, South Uist (Crawford 2002) NMRS Number: NF83SW 2
Diameter 8m, 9 piers?
Internal area perhaps 50.3-9 = 41.3
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