WesWorld

Summary
During the South American War, the Chilean Navy received a rude awakening by watching the minelaying and minesweeping experiences of the Argentine, Brazilian, and South African combatants. The Chileans had not anticipated the importance of mine warfare and swiftly moved to address their shortcoming with the construction of a class of sixteen minesweepers. These vessels were intended for a secondary role as slow coastal escorts.

Following the end of the war, Chile signed over the last four DM1935 class vessels to Brazil in order to address Brazilian shortcomings in clearing mines. Under the terms of the arrangement, the Brazilians retained these four ships and built four new vessels to the DM1935 design which were given to the Chileans. The Brazilian-built vessels were very similar to the originals, differing mainly in construction materials and a number of minor details.

Index of Classes and Vessels
DM1935 class Minesweepers
- DM-1: In service
- DM-2: In service
- DM-3: In service
- DM-4: In service
- DM-5: In service
- DM-6: In service
- DM-7: In service
- DM-8: In service
- DM-9: In service
- DM-10: In service
- DM-11: In service
- DM-12: In service
- DM-13: Transferred to Brazil before completion
- DM-14: Transferred to Brazil before completion
- DM-15: Transferred to Brazil before completion
- DM-16: Transferred to Brazil before completion

DM1938 class Minesweepers
- DM-13: In service
- DM-14: In service
- DM-15: In service
- DM-16: In service

YDM-1 class Light Minesweepers
- YDM-1: In service
- YDM-2: In service
- YDM-3: In service
- YDM-4: In service
- YDM-5: In service
- YDM-6: In service
- YDM-7: In service
- YDM-8: In service
- YDM-9: In service
- YDM-10: In service
- YDM-11: In service
- YDM-12: In service
- YDM-13: In service
- YDM-14: In service
- YDM-15: In service
- YDM-16: In service

DM-1-class, Chilean Minesweeper laid down 1935, Refit 1948
A general-purpose minesweeper and patrol ship, used for coastal purposes. As refitted 1948.

Displacement:
425 t light; 440 t standard; 528 t normal; 599 t full load

Dimensions: Length overall / water x beam x draught
190.00 ft / 190.00 ft x 24.00 ft x 8.00 ft (normal load)
57.91 m / 57.91 m x 7.32 m x 2.44 m

Armament:
2 - 2.95" / 75.0 mm guns in single mounts, 13.23lbs / 6.00kg shells, 1948 Model
Dual purpose guns in deck mounts with hoists
on centreline ends, evenly spread
2 - 1.57" / 40.0 mm guns (1x2 guns), 1.95lbs / 0.89kg shells, 1948 Model
Anti-aircraft guns in deck mount
on centreline forward, all raised guns - superfiring
2 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1935 Model
Machine guns in deck mounts
on side, evenly spread
Weight of broadside 30 lbs / 14 kg
Shells per gun, main battery: 210

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.79" / 20 mm 0.59" / 15 mm 0.59" / 15 mm
2nd: 0.59" / 15 mm - -

- Conning tower: 0.79" / 20 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,385 shp / 1,033 Kw = 16.00 kts
Range 5,500nm at 13.00 kts
Bunker at max displacement = 160 tons

Complement:
54 - 71

Cost:
£0.120 million / $0.479 million

Distribution of weights at normal displacement:
Armament: 4 tons, 0.7 %
Armour: 4 tons, 0.8 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 3 tons, 0.6 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 1 tons, 0.2 %
Machinery: 39 tons, 7.4 %
Hull, fittings & equipment: 248 tons, 46.9 %
Fuel, ammunition & stores: 103 tons, 19.5 %
Miscellaneous weights: 130 tons, 24.6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,284 lbs / 583 Kg = 99.8 x 3.0 " / 75 mm shells or 0.9 torpedoes
Stability (Unstable if below 1.00): 1.08
Metacentric height 0.7 ft / 0.2 m
Roll period: 12.2 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.16
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.507
Length to Beam Ratio: 7.92 : 1
'Natural speed' for length: 13.78 kts
Power going to wave formation at top speed: 51 %
Trim (Max stability = 0, Max steadiness = 100): 25
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 15.50 ft / 4.72 m
- Forecastle (20 %): 11.00 ft / 3.35 m
- Mid (50 %): 10.00 ft / 3.05 m
- Quarterdeck (15 %): 10.00 ft / 3.05 m
- Stern: 10.00 ft / 3.05 m
- Average freeboard: 10.71 ft / 3.26 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 57.6 %
- Above water (accommodation/working, high = better): 110.3 %
Waterplane Area: 3,058 Square feet or 284 Square metres
Displacement factor (Displacement / loading): 218 %
Structure weight / hull surface area: 41 lbs/sq ft or 202 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.07
- Longitudinal: 5.44
- Overall: 1.26
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Breakdown of Miscellaneous Weights:
- 9 tons for Kodkod launchers (with 64 reloads)
- 15 tons for Suite-48 electronics
- 6 tons for depth charges (28x420-lb bombs)
- 55 tons for minesweeping gear
- 10 tons for heating / air conditioning system
- 35 tons for miscellaneous gear

Suite-48 Electronics:
- Type 103.1 "Nalca" navigational surface and air search radar (1 radar, 2 tons)
- Sisdef SPR-48P Passive (Rochelle Salt) Hydrophones (1 primary, 1 secondary, 5 tons)
- Sisdef SPR-48A Active Hydrophones (2 primary, 2 secondary, 5 tons)
- Roth-389b backup diesel generator set (3 tons)

Change log:
- Radar added
- Sonar updated
- 37mm AA replaced with 40mm AA
- 76.2mm deck gun replaced with 75mm deck gun
- Kodkod added
- Excess miscellaneous weight dropped to improve stability.
Refitted 1948 for 64t each.



DM1935 Dragaminas, Chile Minesweeper laid down 1935

Displacement:
425 t light; 440 t standard; 528 t normal; 599 t full load

Dimensions: Length overall / water x beam x draught
190.00 ft / 190.00 ft x 24.00 ft x 8.00 ft (normal load)
57.91 m / 57.91 m x 7.32 m x 2.44 m

Armament:
2 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1935 Model
Dual purpose guns in deck mounts with hoists
on centreline ends, evenly spread
2 - 1.46" / 37.0 mm guns (1x2 guns), 1.55lbs / 0.70kg shells, 1935 Model
Anti-aircraft guns in deck mount
on centreline forward, all raised guns - superfiring
2 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1935 Model
Machine guns in deck mounts
on side, all amidships
Weight of broadside 30 lbs / 14 kg
Shells per gun, main battery: 210

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 0.79" / 20 mm 0.59" / 15 mm 0.59" / 15 mm
2nd: 0.59" / 15 mm - -

- Conning tower: 0.79" / 20 mm

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,385 shp / 1,033 Kw = 16.00 kts
Range 5,500nm at 13.00 kts
Bunker at max displacement = 160 tons

Complement:
54 - 71

Cost:
£0.120 million / $0.480 million

Distribution of weights at normal displacement:
Armament: 4 tons, 0.7 %
Armour: 4 tons, 0.8 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 3 tons, 0.6 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 1 tons, 0.2 %
Machinery: 39 tons, 7.4 %
Hull, fittings & equipment: 199 tons, 37.7 %
Fuel, ammunition & stores: 103 tons, 19.5 %
Miscellaneous weights: 179 tons, 33.9 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,082 lbs / 491 Kg = 80.1 x 3.0 " / 76 mm shells or 0.8 torpedoes
Stability (Unstable if below 1.00): 1.06
Metacentric height 0.7 ft / 0.2 m
Roll period: 12.5 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.16
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.507
Length to Beam Ratio: 7.92 : 1
'Natural speed' for length: 13.78 kts
Power going to wave formation at top speed: 51 %
Trim (Max stability = 0, Max steadiness = 100): 25
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 15.50 ft / 4.72 m
- Forecastle (20 %): 11.00 ft / 3.35 m
- Mid (50 %): 10.00 ft / 3.05 m
- Quarterdeck (15 %): 10.00 ft / 3.05 m
- Stern: 10.00 ft / 3.05 m
- Average freeboard: 10.71 ft / 3.26 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 67.6 %
- Above water (accommodation/working, high = better): 110.3 %
Waterplane Area: 3,058 Square feet or 284 Square metres
Displacement factor (Displacement / loading): 181 %
Structure weight / hull surface area: 33 lbs/sq ft or 162 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.86
- Longitudinal: 4.35
- Overall: 1.01
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Ships in Class (DM1935):
- DM-1: In service
- DM-2: In service
- DM-3: In service
- DM-4: In service
- DM-5: In service
- DM-6: In service
- DM-7: In service
- DM-8: In service
- DM-9: In service
- DM-10: In service
- DM-11: In service
- DM-12: In service

Ships in Class (DM1935/38):
- DM-13: In service
- DM-14: In service
- DM-15: In service
- DM-16: In service

YDM-1 class, Chilean Light Minesweeper laid down 1942

Displacement:
190 t light; 204 t standard; 257 t normal; 300 t full load

Dimensions: Length overall / water x beam x draught
140.05 ft / 134.51 ft x 24.28 ft x 6.56 ft (normal load)
42.69 m / 41.00 m x 7.40 m x 2.00 m

Armament:
1 - 3.00" / 76.2 mm guns in single mounts, 13.50lbs / 6.12kg shells, 1942 Model
Dual purpose gun in deck mount
on centreline forward
2 - 1.57" / 40.0 mm guns (1x2 guns), 1.95lbs / 0.88kg shells, 1942 Model
Anti-aircraft guns in deck mount
on centreline aft
4 - 1.10" / 27.9 mm guns (2x2 guns), 0.67lbs / 0.30kg shells, 1942 Model
Anti-aircraft guns in deck mounts
on side, all amidships
Weight of broadside 20 lbs / 9 kg
Shells per gun, main battery: 650

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 1,048 shp / 782 Kw = 17.00 kts
Range 4,000nm at 15.00 kts
Bunker at max displacement = 96 tons

Complement:
31 - 41

Cost:
£0.080 million / $0.320 million

Distribution of weights at normal displacement:
Armament: 3 tons, 1.0 %
Machinery: 27 tons, 10.6 %
Hull, fittings & equipment: 110 tons, 42.8 %
Fuel, ammunition & stores: 67 tons, 26.1 %
Miscellaneous weights: 50 tons, 19.4 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
552 lbs / 250 Kg = 40.9 x 3.0 " / 76 mm shells or 0.6 torpedoes
Stability (Unstable if below 1.00): 1.11
Metacentric height 0.7 ft / 0.2 m
Roll period: 11.9 seconds
Steadiness - As gun platform (Average = 50 %): 62 %
- Recoil effect (Restricted arc if above 1.00): 0.05
Seaboat quality (Average = 1.00): 1.19

Hull form characteristics:
Hull has raised forecastle
and transom stern
Block coefficient: 0.420
Length to Beam Ratio: 5.54 : 1
'Natural speed' for length: 14.15 kts
Power going to wave formation at top speed: 64 %
Trim (Max stability = 0, Max steadiness = 100): 52
Bow angle (Positive = bow angles forward): 15.00 degrees
Stern overhang: 1.31 ft / 0.40 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 15.75 ft / 4.80 m
- Forecastle (20 %): 14.44 ft / 4.40 m (7.55 ft / 2.30 m aft of break)
- Mid (50 %): 7.22 ft / 2.20 m
- Quarterdeck (15 %): 7.55 ft / 2.30 m
- Stern: 7.87 ft / 2.40 m
- Average freeboard: 8.95 ft / 2.73 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 67.2 %
- Above water (accommodation/working, high = better): 95.9 %
Waterplane Area: 2,114 Square feet or 196 Square metres
Displacement factor (Displacement / loading): 206 %
Structure weight / hull surface area: 32 lbs/sq ft or 157 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.97
- Longitudinal: 5.41
- Overall: 1.16
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate

Breakdown of Miscellaneous Weights:
- 10 tons for Suite-42b electronics
- 8 tons for Kodkod antisubmarine rocket-launched depth charges
- 6 tons for depth charges (28x420-lb bombs)
- 16 tons for paravanes and other minesweeping equipment
- 10 tons other miscellaneous
50 tons total miscellaneous weight

Suite-42b Electronics:
- Type 103 "Nalca" navigational surface and air search radar (1 radar, 2 tons)
- SPR-42 Sound Projector-Receivers (5 tons)
- Roth-389b backup diesel generator set (3 tons)

Ships in Class:
- YDM-1: In service
- YDM-2: In service
- YDM-3: In service
- YDM-4: In service
- YDM-5: In service
- YDM-6: In service
- YDM-7: In service
- YDM-8: In service
- YDM-9: In service
- YDM-10: In service
- YDM-11: In service
- YDM-12: In service
- YDM-13: In service
- YDM-14: In service
- YDM-15: In service
- YDM-16: In service