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Old 29-06-2009, 10:23   #1
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What's Your Cat Bridge Deck Clearance?

The intent of this tread is to gather specific information on bridge deck (under wing) clearance for various catamarans. Your contributions are appreciated.

Once there is a substantial number of post the results will be posted here in summary form.

Here's what's requested
  • Make
  • Model
  • Year
  • Length
  • Beam
  • Design Displacement
  • Actual Displacement (if known)
  • Maximum under wing dimension
  • Minimum under wing dimension (read "Notes" for example)
  • Quick note about how your boat is loaded (i.e full/empty tanks, laden with cruising gear or light ship for racing.
  • Affirmation that YOU took the measurement with the boat in the water.
  • Boat measured in fresh or sea water.
  • Measurements may be in Feet and inches or Centimeters

Notes:
1). Dimensions should be measured with the boat in the water.
2). Most catamarans have protuberances that compromise bridge deck clearance. Example: Fountain Pajot
Venezia 42' has a nice maximum bridge deck clearance at the centerline, but near the hulls the MINIMUM dimension is maybe 12". These bump outs allow superior accommodation, but certainly must add to wave slap noise. Other examples of protuberances are under wing stingers, outboard engine fairings, escape hatch fairings, etc. Please ensure you identify and record both the Minimum AND Maximum under wing dimension accurately.

Please use this format when submitting your information (copy and paste to your post and list data next to each item).
  • Make:
  • Model:
  • Year:
  • Length:
  • Beam:
  • Design Displacement:
  • Actual Displacement:
  • Maximum under wing:
  • Minimum under wing:
  • How loaded:
  • Boat measured in: (fresh or sea water):
  • Measured in water: (yes or no)
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Old 29-06-2009, 10:41   #2
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Boat: Chris White Atlantic 42
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  • Make: Chris White design built by Lombardi Yachts
  • Model: Atlantic 42
  • Year: 1997
  • Length: 42
  • Beam: 23'-4"
  • Design Displacement: 14,500
  • Actual Displacement: ~15,500+
  • Maximum under wing: 26"
  • Minimum under wing: 25"
  • How loaded: Full tanks + 1/2 full holding, Loaded for extend cruising, multiple anchors, tons of spares, extra Genoa, water maker and (2) big A/C units (getting removed soon), boards up.
  • Boat measured in: (fresh or sea water): Sea water
  • Measured in water: (yes or no) Yes, measured in water minutes ago.
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Old 29-06-2009, 12:45   #3
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Boat: Endeavourcat Sailcat 44
Posts: 2,313
  • Make: Endeavourcat
  • Model: Sailcat 44
  • Year: 2002
  • Length: 43.5 ft
  • Beam: 18ft 9 inches
  • Design Displacement: 14,500 Lb
  • Actual Displacement: ?
  • Maximum under wing: 27 inches (forward) (21 inches under wave splitter)
  • Minimum under wing: 21 Inches (aft) (15 inches under wave splitter)
  • How loaded: Full Fuel (110 gallon) and water(120 gallon) Moderate amount of spares, guessing 500 lb. 1 person on board, 250Lb RIB on davits(note: fore measurement of 27 inches made with RIB off the davits). 55 Lb delta on 200 ft of 3/8 chain, 44 lb bruce on 20 Ft of chain and 200 ft 3/4" rope rode. Washing machine, watermaker, ice maker, refrigerator freezer, 5.5 Kw genset, 4 scuba tanks, 100 Lb dive weights, 50 gallon holding tank half full, 2 4D house batteries, 2 size 27 starting batteries. 24 inch radar dome, 4 solar panels.
  • Boat measured in: (fresh or sea water): Brackish (1/2 strength seawater)
  • Measured in water: (yes or no) yes
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Old 30-06-2009, 22:52   #4
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I am following this with interest, but must offer one caveat. Estimating the weight of stuff on a boat is like estimating how much money you spend on boat parts. If you are not keeping accurate records, you WILL go into denial and underestimate.

Case in point. For reasons not important now I weighed the contents of a Catalina 250 WB. Set up for occasional one to two week cruises. Nothing exorbitant. Some food stores, a few tools, boat hook, inflatable life vests, some handheld electronics, you get the idea.

Every time I stepped off with a box or basket I stepped on a scale....

The results: 800 pounds, more than twice what I estimated!!

Food for thought.
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Old 01-07-2009, 00:14   #5
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Stuff IS heavy.

And glad you mentioned about measuring in salt water or fresh. I've only measured mine in fresh and while reasonable, it will be nice to have it a little bit higher in salt water!
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Old 03-07-2009, 06:24   #6
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Boat: Bob Oram Design, 44C, 13.5m -
Posts: 34
# Make: Bob Oram Design
# Model: 44C
# Year: probably 2009
# Length: 1350 cm
# Beam: 650 cm
# Design Displacement: 5200Kg
# Actual Displacement: Probably 5500Kg
# Maximum under wing: 73.5 cm
# Minimum under wing: 65 cm

# How loaded: Will be for cruising as per sister ships.
# Boat measured in: (fresh or sea water):not yet
# Measured in water: no, however all others in the water have very similar levels
# Bridge-deck length is 7.5m
Please note: Bridge-deck/Hull length ratio plays a large part in the effective clearance. I therefore respectfully suggest you should consider this.
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Old 05-07-2009, 15:56   #7
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Boat: Maine Cat 41
Posts: 519
  • Make: Maine Cat
  • Model: 41
  • Year: 2005
  • Length: 41'6"
  • Beam: 23'
  • Design Displacement: 14,400lbs empty, 21,400 loaded
  • Actual Displacement: 20,000 loaded
  • Maximum under wing: unknown
  • Minimum under wing: 31"
  • How loaded: Full fuel (96 gals), Water (120 gals), food for 6 months, clothing, bikes, kayak. safety gear, 2 anchors each with 150+' chain, 2 windlasses, screacher, CF pole, spinnaker, dinghy w/8HP 4-stroke. other extended cruising gear etc
  • Boat measured in: (fresh or sea water): salt
  • Measured in water: (yes or no) no

FWIW, we have never measured the bridgedeck clearance, but we do float approx 2" above the waterline, so we might have 33".

Fair Winds,
Mike
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Old 06-07-2009, 23:32   #8
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Wharram pahi 42 22 ft beam not sure but I can drive my dink under it.
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Old 08-07-2009, 16:55   #9
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Boat: Turtle Island 16 'Miss Cindy'
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Turtle Island 16

Make: Turtle Island
Model: 16
Year: 2008
Length: 15'-8"
Beam: 8'-5"
Design Displacement: 950
Actual Displacement: 850
Maximum under wing: 18"
Minimum under wing: 14"
How loaded: Loaded for extend cruising, no crew aboard. Clearance minus 1.5" with crew aboard.
Boat measured in: (fresh or sea water): Sea water
Measured in water: (yes or no) Yes
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Old 08-07-2009, 19:26   #10
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The ratio of bridge deck width to height is what matters, not the absolute figure.

Quote:
Originally Posted by scrumble View Post
# Make: Bob Oram Design
# Model: 44C
# Year: probably 2009
# Length: 1350 cm
# Beam: 650 cm
# Design Displacement: 5200Kg
# Actual Displacement: Probably 5500Kg
# Maximum under wing: 73.5 cm
# Minimum under wing: 65 cm

# How loaded: Will be for cruising as per sister ships.
# Boat measured in: (fresh or sea water):not yet
# Measured in water: no, however all others in the water have very similar levels
# Bridge-deck length is 7.5m
Please note: Bridge-deck/Hull length ratio plays a large part in the effective clearance. I therefore respectfully suggest you should consider this.
And I think the width, more than the length of the deck.

Rather like ground clearance on an SUV, it is the break-over angles, not the clearance.

Also, the location of the minimum matters. A loaded Gemini practically scrapes the water, but the location of the minimum is such that is it not so bad. Worse than others perhaps, but not nearly so bad as the numbers would indicate.

My guess is that these numbers will mean very little.
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Old 08-07-2009, 21:26   #11
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Beam to bridge deck height ratio.

Thinwater has a good point re the ratio of beam to bridge deck height. That is probably the significant ratio in a design with out a bridge deck carried to far forward.

I have personal experience with an overloaded Gemini from Hawaii to San Francisco. The numbers for the Gemini are not likely to indicate just how bad that boat pounded. The main beam came untabbed and floated, the cabin bulkheads cracked, cabinets fell off the hulls. When I slept my dream worlds jumped up and down.

Tony

Quote:
Originally Posted by thinwater View Post
And I think the width, more than the length of the deck.

Rather like ground clearance on an SUV, it is the break-over angles, not the clearance.

Also, the location of the minimum matters. A loaded Gemini practically scrapes the water, but the location of the minimum is such that is it not so bad. Worse than others perhaps, but not nearly so bad as the numbers would indicate.

My guess is that these numbers will mean very little.
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