Copyright 2011 CONRAD YACHTS All Rights Reserved
Hull Characteristics.
The hull can be best described as a modified constant deadrise form, the most
trusted and well behaved hullform ever developed.
2. Relatively high deadrise at transom(18 degrees), makes her much more comfortable
in sea way than the majority of boats this size, whose deadrise is generally in the 13 to
16 degrees range.
3. The innovative, variable width chine flats are wide aft, gradually narrowing from
amidships forward. The wide chine flats aft give the hull extra lateral stability, while
narrow chine flats forward, allowing the hull to move through the water,  prevent
slamming against oncoming chop.
4. The hull itself is 18 feet long, 20 feet including the engine bracket/swim platform.
Including the outboard engine, the boat is just under 22 feet long.
5.  The hull is the same as the Tuna 18CC(#02). Tuna 18DC(#05) has been
equipped with an upgraded, wide, double console, without a top.
Tuna 20 DC - #05
1. All  major hull structure components are designed and calculated to conform to the requirements of ABS
2. The maximum beam is 8’-0". This is relatively wide for a 20' boat. Tuna 20 is a stable fishing or working platform.
3. Whenever possible, welds are avoided: entire cockpit sole(from the bow to the engine bracket) is made of only two
lengthwise halves, welded together, then welded to topsides(side plates) around the perimeter, and slot welded to
structural members underneath. Each hull half is one piece, so are side plates. This approach yields a much fairer hull.
4. The hull is framed longitudinally, which, again, produces a fairer hull, eliminating the "hungry horse" look of many
metal boats.
5. The structure consists of longitudinal girders and transverse frames, which “egg crate” into one another to make
assembly quick and accurate.
6. I believe in being able to access and remove the fuel tank, if necessary, even after the boat is completed. This is
accomplished by locating the fuel tank under a “soft patch” in the cockpit sole.
7. Alloys used are all top marine grade 5000 series.
Bottom - 1/4"   - 5086 H116
Sides    - 3/16" - 5086 H116
Cabin    - 1/8"  - 5052 H32
1. Transom height is 25”. Using the engine bracket, instead of mounting the engine(s) on the transom, allows the
engine(s) to sit a bit higher and further aft of the end of the hull. This improves the "hole shot" and allows the
propeller to work in less turbulent water flow. It is possible to use 20" leg motor, if preferred.
2. Recommended power for this hull is from 50 hp to 150 hp, single or twin installation.
3. Cockpit is self-bailing.
4. Filling the cavities under the cockpit sole with foam will make the boat unsinkable. This safety feature is required
for boats under 20' in length.
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  • Hull length
18 feet
  • LOA
20 feet
  • Beam
8 feet
  • Draft - hull only
13 inches
  • Draft - engine leg down
29 inches
  • Deadrise at transom
18 degrees
  • Transom bracket angle
13 degrees
  • Minimum cockpit depth - no rail
25 inches
  • Fuel capacity
60 USG
  • Power - single or twin
50-150 hp
  • Capacity ( people)
  • Approx. aluminum weight
1,500 lb
  • Design displacement
3,000 lb
Assembly Drawings:                          
( for
detailed construction study only )
Digital Package:                                             
  1. Assembly drawings.
  2. Parts list.
  3. Nest.
  4. The use of the cutting files-CNC cutting.     
please enquire
  1. All plate parts, cut and formed.
* Does not include tubing, cleats etc.
** Pending current price check at time of purchase
please enquire