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Review of Blanchard Knockabout Jr.


Basic specs.

sail specifications
The Blanchard Knockabout Jr. is a small sailboat designed by the maritime architect Norman Blanchard Sr. in the late thirties. Less than 100 boats have been produced. The Blanchard Knockabout Jr. is built by the American yard Blanchard Boatworks.

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Hull
The hull is made of wood.

Keel

The Blanchard Knockabout Jr. is equipped with a fin keel. A boat with a fin keel is more manoeuvrable but has less directional stability than a similar boat with a long keel.

The boat can enter even shallow marinas as the draft is just about 0.70 - 0.80 meter (2.30 - 2.60 ft) dependent on the load. See immersion rate below.


Sailing characteristics

This section covers widely used rules of thumb to describe the sailing characteristics. Please note that even though the calculations are correct, the interpretation of the results might not be valid for extreme boats.

Stability and Safety

What is Capsize Screening Formula (CSF)?

The capsize screening value for Blanchard Knockabout Jr. is 2.32, indicating that this boat would not be accepted to participate in ocean races.


Theoretical Maximum Hull Speed

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 5.4 knots. The term "Theoretical Maximum Hull Speed" is widely used even though a boat can sail faster. The term shall be interpreted as above the theoretical speed a great additional power is necessary for a small gain in speed.


Immersion rate

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Blanchard Knockabout Jr. is about 64 kg/cm, alternatively 362 lbs/inch.
Meaning: if you load 64 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 362 lbs cargo on the boat it will sink 1 inch.


Sailing statistics

This section is statistical comparison with similar boats of the same category. The basis of the following statistical computations is our unique database with more than 26,000 different boat types and 350,000 data points.

Motion Comfort Ratio

What is Motion Comfort Ratio (MCR)?

The Motion Comfort Ratio for Blanchard Knockabout Jr. is 10.3.

Low High 31% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 31% of all similar sailboat designs. This comfort value is just below average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Blanchard Knockabout Jr. is 3.08.

Wide Slim 86% 0 50 100
Compared with other similar sailboats it is slimmer than 86% of all other designs. It seems that the designer has chosen a significantly more speedy hull design.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Blanchard Knockabout Jr. is 152 which categorizes this boat among 'light racers'.

Heavy Light 66% 0 50 100
66% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.


Maintenance

Bottom Paint

When buying anti-fouling bottom paint, it's nice to know how much to buy. The surface of the wet bottom is about 10m2 (107 ft2).
Based on this, your favourite maritime shop can tell you the quantity you need.

Note: If you use a paint roller you will need more paint than if you use a paintbrush.


Rig

If you need to renew parts of your running rig and is not quite sure of the dimensions, you may find the estimates computed below useful.



Guiding dimensions of running rig
UsageLengthDiameter
Jib sheet 6.1 m(20.0 feet)8 mm(5/16 inch)
Genoa sheet 6.1 m(20.0 feet)8 mm(5/16 inch)
Mainsheet 15.2 m(50.0 feet)8 mm(5/16 inch)
Spinnaker sheet13.4 m(44.0 feet)8 mm(5/16 inch)

Boat owner's ideas

This section is reserved boat owner's changes, improvements, etc. Here you might find (or contribute with) inspiration for your boat.

Do you have changes/improvements you would like to share? Upload a photo and describe what you have done.



Finally

We are always looking for new photos. If you can contribute with photos for Blanchard Knockabout Jr. it would be a great help.

If you have any comments to the review, improvement suggestions, or the like, feel free to contact us. Criticism helps us to improve.



References