Twin keel research

[MikeJohns]

I am looking into twin keels for a sailing yacht.

Lord Riverdale apparently researched twin keels yonks ago and his conclusions were published in a technical paper. This paper was offered to the Royal Institute of Naval Architects on December 15, 1967.
Also Riverdale was involved with extensive tank testing undertaken on the twin keel design Bluebird of Thorne II along with the designer Arthur Rob.

The results of the tank testing were apparently published separately to the Riverdale paper, but I can't find where.

RINA has the Riverdale presentation available for 10 pounds stirling (scanned onto CD )

Has anyone bought this off them and is it worth getting ? Is there a free synopsis available anywhere else ?
Does anyone know where I can find the tank test results?

Any other research published or accessible that anyone knows about?
Seems this is an interesting area waiting for a lot of investigation.

[Sean Herron]

Hello...

Has done a lot of tank testing at the University of British Columbia...

See site http://www.brayyachtdesign.bc.ca/ - articles - advantages of twin keels...

SH.

Prof. Joachim Heinrichs of East-Germany did a lot of research on twin keels back in the seventies and eighties. His keels were and are used with good success in the hundreds in Reinke's (West-German) yachts in the same period. These are asymmetrical Gö-693 sections, 9% at the root, 12% at the tip, and of a depth that makes max. thicknesses coincide. There's a very small toe-in. In section the keels are almost vertical, and quite close together.

A lengthy abstract of Heinrich's research is to be found in the book "Yacht Design" (I think that's the name) by Reinke/Muhs/Lütjens.

Some of Reinke's designs (they are ugly, but work well) are at http://www.reinke-yacht.de/

There's also an article on twin keels at http://www.kastenmarine.com/
that is well worth reading.

BL

[FAST FRED]

One disadvantage to twin keels is the difficulty to heal a grounded boat to unstick her.

Second is the uguly job of power washing and repainting between the keels.


If tidal storage is the requirement , many Brit boats use legs attached to the chain plates , with a chain between the bottom pads to keep them from seperating.

These boats take the tide unattended , season after season.If that was the purpose of your desire for bilge keels.

FAST FRED

[MikeJohns]

Thanks for the info.

I had been asked to look into the feasability of retrofitting twin keels to an existing yacht. The owners want to be able to take the ground in areas of large tidal range without fuss, with the advantages of reduced draft with increased damping (he gets seasick easily).

Reading what I have been able to get my hands on indicates that the existing published data only gives a starting point for a new design and that moreover; the twin keel hull interaction, tracking stability and high possibility of induced drag with minor imperfections in position section and angles are so high as to make considerable tank testing mandatory for each and every design. There are so many variables with these keels.

The Reinke information looks interesting thankyou, the website shows some very "different" design approaches. The Reinke approach appears to favour a flat bottommed hull. I will try and read his material if I can find the book.

Does anyone know if it is available or its ISBN ?

[brian eiland]

Originally Posted by MikeJohns

I am looking into twin keels for a sailing yacht.

Lord Riverdale apparently researched twin keels years ago and his conclusions were published in a technical paper. This paper was offered to the Royal Institute of Naval Architects on December 15, 1967.
Also Riverdale was involved with extensive tank testing undertaken on the twin keel design Bluebird of Thorne II along with the designer Arthur Rob.

The results of the tank testing were apparently published separately to the Riverdale paper, but I can't find where.

RINA has the Riverdale presentation available for 10 pounds stirling (scanned onto CD )

Has anyone bought this off them and is it worth getting ? Is there a free synopsis available anywhere else ?
Does anyone know where I can find the tank test results?

Any other research published or accessible that anyone knows about?
Seems this is an interesting area waiting for a lot of investigation.

Hi Mike.
You might have a look at a posting I made awhile back on the cruising aspects of twin keels.

And you might refer to the monohull section of my website http://www.runningtideyachts.com/monohull/.

Obiviously I was much interested in this subject, and still am. I just haven't paid it much attention in quite some time. Last year I had suggested a 70' version to a potential client, but he did not pursue the project. Just yesterday I received an interesting inquiry into a 50' design by a gentleman who owns a smaller twin keeler. I sent him a copy of the RINA presentation for his review. I had tried to get some of the actual tank testing data, but it appears as though that got tided up in the estate proceedings of Arthur Robb, maybe never to see the light of day.

I would be interested in hearing more of your desire to dig deeper into the subject, and how we might work together on such an endeavor.

[Sean Herron]

Hello...

Another interesting approach is the Red Fox Vision of the UK...

See http://www.selectyachts.co.uk/redfoxhome.asp?ArtID=13 ...

I sailed one on my honeymoon and the thing ended upwind of where I was pointing...

You can Email the designers son at info@selectyachts.co.uk and if his father is available he will get back to you...

SH

[sorenfdk]

Originally Posted by MikeJohns

Does anyone know if it is available or its ISBN ?

The title is "Yacht Bau", authors Reinke, Lütjen & Muhs, published by Delius Klasing Verlag, but AFAIK only in German. The ISBN of the third edition is 3-7688-220-5, but there might be a newer edition.
It is not exactly on my must-have list, but the chapter on asymmetric twin keels is quite informative and interesting.

[MikeJohns]

Originally Posted by brian eiland

I would be interested in hearing more of your desire to dig deeper into the subject, and how we might work together on such an endeavor.

Brian thanks for your post, I am working on developing a cheap model testing rig to improve the cost and availability of model testing. If it all comes together ( non-paying projects tend to be at the bottom of the pile ) I shall be looking at testing various twin keels to gain a bit of insight into the intricacies therein, because I am interested .

Have you read Prof. Joachim Heinrichs work ? I have done little study yet into twin keels and have yet to obtain Riversdales paper.

Anecdotaly owners either praise or condemn the performance of their twin keeled vessels, but many have been designed poorly by indifferent designers with no tank testing (merely providing legs).

One owner I interviewed a few years back said his twin keeled 45' yacht was the slowest thing afloat. A subsequent owner a few years later had re-rigged the vessel added a mizzen along with significantly more sail area and reported it a good and stiff performer that pointed well . That owner has now cruised extensively and is very happy with all aspects of the boat. He wouldn't move back to a single keel.

So I am interested, but not yet a convert. Being an Engineer I want some numbers. I might try and get some lines off the above vessel as a starting point (one off design, dead and gone designer, no plans). Next year hopefully.


sorenfdk
Thanks for the book info.

To everyone else
Thanks for you input

[Sean Herron]

Hello...

Found an old folder of links on a zip disk...

http://www.lerouge-yachts.com/mono_TKS.htm

http://www.johnsboatstuff.com/Boat%2...4/twinkeel.htm

http://otrc.tamu.edu/Pages/fpsoroll.htm

http://www.webb-institute.edu/stability/IKEDA.pdf

http://books.nap.edu/books/NI000359/...3.html#pagetop

http://www.ybw.com/ym/drying.htm

SH.

I fully agree with the above notion that Reinke's book is not a must-read. Actually, it's mostly biased, crap, plain wrong, outdated and self-glorifying. I also submit again that his designs are among the ugliest afloat. Just my personal opinion, of course.

And yet, and yet... there's something to his twin-keel approach. I've been witness to a series of direct tests of one of Reinke's designs, one with the conventional, moderately long single keel, the other with the twin-keels, the boats otherwise being fairly equal. This was conducted in (i think) 1985 by a German boating magazine and lasted for several days, under different conditions.

The results were, basically: there wasn't much difference either way, which was considered a success for the twin keel concept back in the day.

As to Prof. Heinrich's research papers: I've seen them, and they do not look like you would expect from a scientific paper these days: No CCP, no fancy equations, etc. It's more of a documentation of a years-long trial-and-error process (tank and real-life): unscrew the keel, screw it on with a different angle or with a different acpect ratio, repeat. There's no "magic logic" to tell you how to calculate keels for any particular hull, based on tangible parameters. It's like shooting in the dark. There's little linear behaviour: If you vary one parameter (as good as you can), things may go downhill first, than pick up, than completly bottom out, only to pick up again and reach a maximum of sorts.

Only the Gö-693 section and a NACA 00xx section were tested, and the latter was eliminated halfway through, because it never really performed.

I think the choice of the Gö-693 was merely a hunch, based on long years of work with foils.

The conclusions, as I said in my earlier post, were that on a number of quite different hulls, asymmetrical Gö-693 sections, 9% at the root, 12% at the tip, of a depth that makes max. thicknesses coincide, small toe-in, almost vertical keels, quite close together, performed best overall. (the 'flat' side goes outboard, of course)

The amount of toe-in was in the <1% range, and the keel placement fore-aft and athwart was eyeballed by aligning the outer surface of the keels at the hull-keel intersection with the hull diagonals at that place, until they coincide visually as best as possible. With this framework of reference points, there's little ambiguty left about keel placement, length, chord, thickness and aspect ratio, but it's not exactly 'scientific' - more a question of 'feeling'

The rest of the paper is an attempt to rationalize the results qualitatively, mostly static and steady-state, as is to be expected from somebody with a background in airplane aerodynamics. It's probably easily shot full of holes these days, but at the time it was the state-of-the-art.

The flat-bottom setup of Reinke's yachts is a (controversial) addition of his own.

As I understand, the old Reinke felt kind of heir to Heinrich's work and would sell copies for a nominal amount, if asked. I assume his son, who's now in charge, will do the same. I don't know for sure, but I think young Reinke doesn't speak a word of English, so better get a german-speaker to ask for you. Just don't ask me, because we're not getting on well...

[MikeJohns]

Ben Lindenberg


Thanks for your post, I think the chances of coming up with equations for placement, sweep back angle, size, depth, toe-in, foil shape.... is zilch. Thats why I want to build a comprehensive test rig that can change several variables in one tow. Then we can shoot in the dark and work up to a brightly illuminated dawn

I am looking for good starting points from which to take aim, ie successfull twin keelers. There was a Melbourne designer that built a couple of racing twin keelers (20 years ago) that performed very well I have a magazine article and am trying to find him (probably wandered on by now).

Over the years predjudice has thwarted much interest in this field largely due to the designers that simply added landing skids to designs that had performed well as single keelers.

Ben
could you give me your email address please
mjeng@supernerd.com.au I'll add you to my database and keep you informed if we do research this.

[brian eiland]

Originally Posted by MikeJohns

Have you read Prof. Joachim Heinrichs work ? I have done little study yet into twin keels and have yet to obtain Riversdales paper.

Hi Mike,
Can't wait till we get this damn election thing finished here in the US....so distracting as its so important.

I can get you a copy of Lord Riverdale's paper either by scanning mine and/or by mail. Then everyone is on the same page as we go forward with more discussions. Could prove real interesting in getting this twin keel concept
re-jumpstarted. I still believe it has such excellent possibilites.

I did find the use of hard-chine hulls by the Prof interesting, particularly for metal hulls (and with fewer frames ala Origami metal boatbuilding premises). I just can't read German....use to looooong ago

Higher up in this thread there's this picture of a yellow model hull turned turtle. This a a nice specimen of what is guaranteed NOT to work, because the keels are way to much forward. Plain dangerous. I wonder why they even bothered to build the model. Probably they guys from Bray Design think that by posting a picture like that in an article about their twin keel research they protect their secret results? Whatever...

Ben

[sorenfdk]

Brian:
If it's not too much trouble, I'd like a copy of Lord Riverdale's paper, too.

Ben:
Why do you think that the keels of the yellow model hull are "guaranteed NOT to work" and even "plain dangerous"? To me, they don't seem to be located that much forward. Their longitudinal position must be related to the CE of the sailplan (which we can't see).