Daggerboard versus keel fin on cruiser

Uh... before I comment back, I am not sure I am clear on the meaning of this. Was that an insult?

 

It would be nice to see some actual data. 2 keel/fin flaps plus a rudder are 3 shaft linkages to make and maintain- not exactly inexpensive. It is an interesting idea. If we take a page from Newick's proas how about a combination daggerboard rudder? It has the flap effect and eliminates a whole appendage and can be pulled up for shoal water and beaching + removed easily for maintenance.

 

WOW...flaps on fins

This is very interesting...

I am struggling to find the article on the web site...can you put in the link. Is there more info (especially a drawing/picture of the concept/idea.

It seems to line up nicely with the concept of the flaps on an aeroplane wing. Very interesting and would love to hear more.

Mick

 

Trim tabs on LAR keels? An interesting development, but certainly not something to fit and forget, which is often what cruisers want. It will be interesting to see how they work in practice. I have used them on monohulls in the 1970's but they fell out of favour with the demise of the IOR

I once made an experimental trim tab on a dagger-boarded dinghy (nearly 40 years ago now). It was quite fun to close reach yet actually be sailing sideways and to windward relative to other boats. So I later drew them on my first racing multihull, but they were never made. A bit too complex then (and probably now)

Having said that, there is still the problem of increased WSA offwind and extra buoyancy midships, which is bad for high speeds and increases pitching

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Here http://www.chriswhitedesigns.com/atlantic_cats/a47/

This is the most interesting quote from a man with much experience......

It's clear from the performance of the Atlantic 55 and A57, which have fixed fins and retractable boards, that upwind performance with the boards retracted is still quite good. Basically, if a cat is reasonably light, has an efficient sail plan and some type of fin under the hull, it will sail well.


Regards.

 

I suppose the was an insult then. My response was:
Nice ctrl-v or "command-v" skills. Very knowledgeable.

So you have more experience than Richard Woods, Kurt Hughes and Morelli and Melvin? Each of those designers are likely to disagree with that copy and paste.

 

The French cat with twin keels and twin daggerboards was launched on Saturday and I got a chance to speak with its owner about daggerboards.

He told me that with only the keel the performance of the cat to windward is good...so good that he seldom uses the daggerboards.

On the negative side he told me that the retracted boards are always IN THE WAY and that when in use, under certain wind and wave conditions , they make his cat " trip " and this motion causes insecurity for the crew

On the plus side..under certain conditions the daggerboard helps the cat track better and is easier to steer and hence the autopilot has less work to do.

 

Catbuilder: Love the LAR on the Chris White cat.. Beautiful design. Have not surveyed one of these but would love the opportunity.

As far as the subject goes, I lived and cruised aboard a 2001 34' Gemini 105 MC for several years and loved the performance and option of the retractable centerboards that were designed to "kick up" into the hull if they struck the bottom while under sail. I never had to worry about that or had that happen, but I am all about safety first so I always felt warm and tingly to know that design was there.

I have seen many vessels that have keel damage from fixed keels where the energy was transferred to the structure of the vessel. Some of the bolt on keels would partially sheer away and the glassed in keels would have at the least fiberglass damage along the weakest points of laminate near the keel.

I guess this would come down to the vessel's intended use. For deep water cruising and performance I would go with the keel fin. For more shallow water cruising like here in South Florida I would go with the daggerboards. That is just my humble opinion from my training and experience with mono hulls and catamarans.

 

The Newick Proa rudder/daggerboard , also used by Russell Brown, could be done in a fin keel arrangement as well. The funny thing is it then becomes a shorter modern version of the rudder on keel boats of years past such as the old meter boats. For the gadget prone a windvane linkage could be set to "tack" the trim tabs when coming about on the Chris White version.

 

Agree completely - and I used to have a Catalac 10M which is what the Gemini was based on, originally. Great boats in a lot of ways.

I will make a note of your screen name, since I'll have some survey work in FL coming up within a year.

Do you specialize in catamaran surveys?

 

The Gemini was actually based on the old Aristocat 30 molds aquired by Tony Smith in the year 1... Now about losing those troublesome stern rudders....

 

Whoops! They both came from Bobcats. My mistake:


Following the successful development with Bill O'Brien of the Bobcat Catamaran in the 1960s, Tom Lack Catamarans LTD specialized in building these early cruising catamarans. In fact, they built hundreds of Bobcat Catamarans. It was 1970 when they came to the decision to end building O'Brien's Bobcat and working with boat designer John Winterbottom, created their own design, the Catalac 9M. This marked the beginning of the Catalac line of cruising catamarans.

The Catalac 9M was formerly introduced in 1970, followed by the Catalac 8M in 1975, 12M and then the 10M. The boats had a stellar reputation for build quality and seaworthiness. Close to 1000 cruising catamarans were built by the Lack family, 600 of them were Catalacs, making them a cruising catamaran success story as well as one of the pioneers in multihulls. A related footnote is that boat builder Tony Smith of Performance Cruising Inc. (Gemini Catamarans) also worked for O'Brien at that time. It's no coincidence that the layout of Gemini's and Catalacs are very similar.


http://www.catamaransite.com/catalac_history.htm

 

I'm not sure if that's true. I don't think Tony is old enough. But he did work for Derek Kelsall in the early 1970's

As I recall, the Aristocat (which was a commercial failure in the UK as it wasn't as good as the Prouts or Catalacs) was designed by Robin Musters

I think Tony got the Aristocat moulds about 1983

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

All you guys, you need to be very careful that you don't attract the attention of the people who have the CBTF patent. They are very hot on litigation with people who build or sail boats which they consider breach their patent rights.
For further information just Google CBTF.
Or read this.
Licensing

The CBTF patents cover sailing yachts using a canting keel or ballast with fore and aft controllable foils or rudders to affect changes in side force and/or maneuvering, including sections with trim tabs and jibing daggerboards.
Learn more

Note: The contents on this website are subject to change.
Schock 40/CBTF Video

Note: This video requires Quick Time Player - download here

 

Thank you for the input, Richard. If anyone knows the history of these boats, it is probably you. Rick should probably change his website.