Review of K-47 Motorsailer

Basic specs.

The K-47 Motorsailer aka Kettenburg 47 is a large motorsailer designed by the maritime architect Kettenburg in the late fifties. Only a few boats have been produced. The K-47 Motorsailer is built by the American yard Kettenburg Marine.

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Hull

The hull is made of wood.

Interior

The boat is equipped with 946.0 liter fresh water capacity.

Rig

The K-47 Motorsailer is equipped with a masthead rig. The advantage of a masthead rig is its simplicity and the fact that a given sail area - compared with a fractional rig - can be carried lower and thus with less heeling moment.

Keel

Full keel

The K-47 Motorsailer is equipped with a long keel. A full keel provide a better directional stability than a similar boat with a fin keel; on the other hand, better directional stability means also that the boat is more difficult to handle in a harbour with less space.

The boat can only enter major marinas as the draft is about 1.83 - 1.93 meter (6.00 - 6.30 ft) dependent on the load. See immersion rate below.

Engine

The K-47 Motorsailer has been equipped with different engine alternatives.

Alternative 1:

K-47 Motorsailer may be equipped with an inboard Mercedes-Benz diesel engine

Alternative 2:

The boat may be equipped with a Chrysler engine.

The fuel tank has a capacity of 946.0 liters (249 US gallons, 208 imperial gallons).

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 K-47 Motorsailer is 1.66, indicating that this boat could - if evaluated by this formula alone - 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 8.7 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 K-47 Motorsailer is about 360 kg/cm, alternatively 2016 lbs/inch.
Meaning: if you load 360 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 2016 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 K-47 Motorsailer is 37.9.

Comparing this ratio with similar sailboats show that it is more comfortable than 69% of all similar sailboat designs. This comfort value is just above average.

L/B (Length Beam Ratio)

What is L/B (Length Beam Ratio)?

The l/b ratio for K-47 Motorsailer is 3.41.

Compared with other similar sailboats it is more spacy than 54% of all other designs. It seems that the designer has chosen a slightly more spacy hull design.

D/L (Displacement Length Ratio)

What is Displacement Length Ratio?

The DL-ratio for K-47 Motorsailer is 203 which categorizes this boat among 'light crusers & offshore racers'.

62% of all similar sailboat designs are categorized as heavier. A light displacement requires less sailarea and has higher accellerations.

SA/D (Sail Area Displacement ratio)

SA/D (Sail Area Displacement ratio)
Indicates how fast the boat is in light wind:
- Cruising Boats have ratios 10-15
- Cruiser-Racers have ratios 16-20
- Racers have ratios above 20
- High-Performance Racers have ratios above 24
Sail-area/displacement ratio (SA/D ratio): 13.89

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 58m² (624 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**
Usage	Length		Diameter
Jib sheet	14.2 m	(46.5 feet)	16 mm	(5/8 inch)
Genoa sheet	14.2 m	(46.5 feet)	16 mm	(5/8 inch)
Mainsheet	35.4 m	(116.2 feet)	16 mm	(5/8 inch)
Spinnaker sheet	31.2 m	(102.3 feet)	16 mm	(5/8 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 K-47 Motorsailer 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

[Ref 1]: ISO 8666 Small craft — Principal data.
[Ref 3]: ISO 12215-5 Small craft — Hull construction and scantlings.