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Review of Blanchard Knockabout Sr.


Basic specs.

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

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Hull

The hull is made of wood.


Keel

Fin keel

The Blanchard Knockabout Sr. 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 full keel.

The boat can enter even shallow marinas as the draft is just about 1.07 - 1.17 meter (3.51 - 3.81 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 Sr. is 2.22, 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 6.1 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 Sr. is about 91 kg/cm, alternatively 511 lbs/inch.
Meaning: if you load 91 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 511 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 Sr. is 10.2.

Low High 7% 0 50 100
Comparing this ratio with similar sailboats show that it is more comfortable than 7% of all similar sailboat designs. This is a comfort value significantly below average.


L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for Blanchard Knockabout Sr. is 3.72.

Wide Slim 99% 0 50 100
Compared with other similar sailboats it is slimmer than 99% of all other designs. It seems that the designer has chosen a significantly more speedy hull design. This type of design is also referred to as 'needle'.


D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for Blanchard Knockabout Sr. is 96 which categorizes this boat among 'ultra light racers'.

Heavy Light 95% 0 50 100
95% 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 15m2 (161 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 7.9 m(26.0 feet)10 mm(3/8 inch)
Genoa sheet 7.9 m(26.0 feet)10 mm(3/8 inch)
Mainsheet 19.8 m(65.0 feet)10 mm(3/8 inch)
Spinnaker sheet17.4 m(57.2 feet)10 mm(3/8 inch)

Boat owner's ideas

This section is reserved boat owner's modifications, 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 Sr. 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