Ironbark 28' Traditional Displacement Boat

Similar Designs
  • Ironbark 28' Traditional Displacement Boat
  • Ironbark 28' Traditional Displacement Boat. Ironbark is under construction in Southern Norway.
  • Ironbark 28' Traditional Displacement Boat. Ironbark is under construction in Southern Norway.
  • Ironbark 28' Traditional Displacement Boat. Ironbark is under construction in Southern Norway.
Click on the image for full-size version and slideshow

  • Vessel Specifications and Comments

    • Construction: traditional or cold molded construction.
    • LOA: 28’ 0”
    • LWL:
    • Beam : 9' 10"
    • Draft : 3’8”
    • Displacement : 16,250 lbs
    • Ballast: 2500 pounds
    • Power: 62 HP Perkins 4-236
    • Cruising Speed: 6.8 knots
    • General Comments: Though actually not a very large boat, Ironbark will have the feel of a real ship. Her slow deep roll, straight tracking, and ability to keep on going no matter what, are the benefits reaped from plenty of weight, a long straight keel, and fine, deep sections. Ironbark is one of ten power boat designs created for the article “Power Boat Design, Form and Function” published in Wooden Boat #137. Download the “Power Boat Design, Form and Function” PDF.

  • About the Plans

    • Construction Method and Materials:

      Traditional or cold molded construction

    • Number and Type of Drawings:

      Full size plots (e-mail or CD) for bulkheads, stem and transom, plus pdf building plans.

    • Study Plan:

      --

    • Base Price:

      $850.00 CAD
    Order the Plans -->

Design Comments

Though actually not a very large boat, Ironbark will have the feel of a real ship. Her slow deep roll, straight tracking, and ability to keep on going no matter what, are the benefits reaped from plenty of weight, a long straight keel, and fine, deep sections. She is very much a traditional type; her lineage started before 600 AD with Norse Viking ships, comes through Scandinavian and Irish fishing vessels, and finally through the fishing boats of my home waters, Canada's westcoast.   

Ironbark's looks are also entirely in keeping with her performance, no tricks here! The deckhouse and accommodation is very limited for her weight and cost, but a large deckhouse can visually overpower a graceful hull; get the proportions wrong and the boat starts to look top heavy.

Ironbark carries 2600 lbs of ballast in the form of lead pigs down on top of the keel between the floors. Ballast? in a powerboat, how come? Because it lowers VCG (vertical center of gravity) and lengthens GM. GM is the distance from the CG (center of gravity) to the metacenter. The metacenter's height is dependent on waterplane inertia, a narrow, fine waterplane gives a low metacentric height and a rolly boat. A wide, full waterline gives a tall metacentric height and a stiff boat. As the boat heels the VCB (vertical center of buoyancy) moves about the metacenter, and righting arm is the distance between a vertical line connecting VCB and metacenter, and CG (center of gravity). The longer the GM, the faster a large righting arm is developed, and the faster the boat returns to upright. There is no real agreement on how much GM is enough, Francis S. Kinney in Skene's Elements Of Yacht Design, mentions a GM of 2'-2'6" for small power cruisers. Ironbark is right in the middle of that with a GM of 2.25'. The CG two inches above DWL allows for additions of weight up high, a heavier mast and stabilizer poles, or a dinghy on the cabintop.

Ironbark is under construction in Southern Norway.

Tad Roberts