Review of Diana 21

The hull is made of hand laid fibreglass while the deck is made of fibreglass. Generally, a hull made of hand laid fibreglass requires only a minimum of maintenance during the sailing season. And outside the sailing season, just bottom cleaning and perhaps anti-fouling painting once a year - a few hours of work, that's all.

The interior is like few other boats made in fibreglass.
The boat is equipped with one cabin and 2 berths.
Note: the boat has also been sold to be self-made/-interiored, which means that the quality of each boat may vary.

The Diana 21 is equipped with a long keel. A long 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.

Diana 21 can enter even shallow marinas as the draft is just about 0.45 - 0.55 meter (1.48 - 1.78 ft) dependent on the load. See immersion rate below.

The boat is typically equipped with an inboard Volvo Penta MD2010 diesel engine at 10.0 hp (7 kW).

The transmission is a shaft drive.

The fuel tank which is made of stainless steel has a capacity of 30.0 liters (7 US gallons, 6 imperial gallons).

What is Theoretical Maximum Hull Speed?

The theoretical maximal speed of a displacement boat of this length is 6.3 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.

The immersion rate is defined as the weight required to sink the boat a certain level. The immersion rate for Diana 21 is about 82 kg/cm, alternatively 464 lbs/inch.
Meaning: if you load 82 kg cargo on the boat then it will sink 1 cm. Alternatively, if you load 464 lbs cargo on the boat it will sink 1 inch.

What is L/B (Length Beam Ratio)?

The l/b ratio for Diana 21 is 3.58.

Compared with other similar motor boats it is slimmer than 100% 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'.

In Denmark, you are required to have achieved a 'powerboat driving license' in order to sail a powerboat.
In this context a boat is considered a powerboat if:

According to this definition this boat is not categorized as a Powerboat.
Though, if you install a motor of 47 kW (63 hp), then the boat will become a powerboat, and you will need a Danish 'powerboat driving license'

This section shown boat owner's changes, improvements, etc. Here you might find inspiration for your boat.

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

We are always looking for new photos. If you can contribute with photos for Diana 21 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.

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