Twin keels v. fin keel

[AliM]

Lots of us have bilge/twin keels to explore the shallow East Coast, but the “sailing experts” all tell us that we lose performance relative to our fin-keeled cousins, so I just wanted to share this with you…

As many of you know we had a new boat launched in Germany a few weeks ago – she has twin keels. Yesterday we met her designer (who also races and designs high-performance boats), and he sailed on our boat for several hours and then on an identical boat with a fin keel for a few hours afterwards. We sailed alongside each other (no, we don’t race!!!), so we compared speed, pointing, general handling at several points of sail, in winds from 5 to 22kts app. and sea state flat to about 80cm waves. In total we sailed about 22 nm - a pretty fair test!

The designer confirmed that there was no difference in pointing, speed or handling between the two boats. When we first met him, he expressed some scepticism about why anyone would want to choose twin keels, and he said he’d been very reluctant to take on the design for twin keels in the first place. At the end of the day he was very positive about twin keels and very proud of the success of his design.

 

[Tom Price]

What boat?

Class/type, designer please.

 

[AliM]

Sirius 310

 

[Bru]

The problem is that twin keels are lumped in with bilge keels in the minds of most people and gain an underserved reputation for poor performance as a result

Properly designed with asymetric foil keels, a twin can come close to the performance of a shoal draught fin and even be better on some points of sailing (a deep fin is going to win hands down in most conditions though)

Back in the good old days when the leisure yachting explosion took off, there was very little understanding of the hydrodynamics of yacht hulls and especially of the effects of bolting two keels on instead of one.

Designers got it wrong as often as they got it right (probably more often in fact) even when they were trying to come up with something with a half decent performance. And sometimes they didn't even try and just clagged a couple of vertical slabs on either side of the boat and said "that'll do"!

There were also various instances of long keel, fin keel and centreboard designs that were then modified to satisfy a demand for twin/bilge keels and this was rarely totally satisfactory.

As a result, there were a lot of boats with two keels around that had the performance of a bathtub generating excessive drag and leeway and unable to point up anywhere near the wind. The mud has stuck in the minds of most people even though there were boats in the 60's which, er, broke the mould and with the advances in knowledge gained over the years modern twin keelers are usually pretty decent performers

 

[benw]

We are East Coast based and have a Sadler 32 twin keel. I have not been disappointed by the performance of our yacht. 11 hrs to Oostende in f4 with a couple of hrs much more but comfortably done. Return 13.5 hrs which was a couple of hrs less than the snazzy racers with racing sails deep fIns and big wallets.
I am more than happy with a 32 ft er that can handle a big breeze, take the ground and accommodate the family safely.
The paperwork suggests a twin keel 32 will sacrifice a bit close hauled but our keels are as deep as the shallow fin vsn, only the deep fin chaps have the advantage.
I think sails can make a huge difference and all up cruising weight ie there are lots of other variables that get in the way of blistering up wind performance.
Glad you are enjoying your new yacht. The pics looked great.
Ben