split keel

[Gaia_jan]

HI there.
I am the owner off a danish one off sail boat built in GRP. Can be seen on danish home page www.gaiamarine.dk. The boat has a draft of 2,2 meter, and often is that a problem for us. The keel is made in steel with lead melted down inside, and then bolted to the bootom. We like the boat and dont like the idea of selling it. I am facinated by boat with lifting keel, but it is not possible on our boat, it has to be made like that from original. My idea is to make a keel similar to the one we have, but split the lowest 70cm up in two in the lateral plane, and make them moveable 90degrees, like to a wing keel. This will give a high redusing in the draft. And no changes on the hull. I only had this idea for a couple of days now. I want to here about any ones experience in this type if ever made. I am working as tecnical designer, and would be able to make the technical drawing my self.
Best Regards
Jan Jensen

[Dutch Peter]

Dear Jan,

Not that I don't like the idea, but the problem with what you're suggesting is the strenght of the construction and how to operate it.
Not that you should abandon the idea, but also consider replacing your current keel with a wing keel with less draft. Ofcourse a designer would have to check whether this has no adverse effect on the stability.

[sorenfdk]

Hej Jan!

Jeg vil give Dutch Peter ret: Ideen er ikke dårlig, men den bliver nok svær at få virkeliggjort!
Hvis det var min båd, ville jeg nok vælge vingekølen i stedet eller måske en bulbkøl.
Du er velkommen til at henvende dig, hvis du får brug for professionel hjælp.

And for the rest of you: I agree with Dutch Peter. If it was my boat, I'd probably go for a winged keel or a bulb. Anyone in need of professional advice is more than welcome to contact me!

[MikeJohns]

It has been done.
Marine growth is a problem if the keel is left split open. As the others have posted; if you can wear the reduction in immersed lateral area then you are better off with a shallower draft keel without the moving parts. You could use the existing keel , shorten it and fair in a wider bottom portion for the ballast such as the scheel keel.
Bulbs are often not worth adding, Ted Brewer for example reported on tank tests that compared bulbs with NACA foils on conventional cruising hulls they cause more drag, so be careful.

[Dutch Peter]

Jan, Soren, Mike,

The Dutch shipyard "Jongert" has developped a 'butterfly'-keel. 4 panels connected with hinges, 1 hydraulic cylinder for actuating.

Check out this site: http://www.jongert.com/index2.html

Jan, I told you not to abandon the idea, but be assured, it's gone cost you a bundle!!!

[D'ARTOIS]

Hi Peter, You are 100% correct, however the main reason for this keel was the ability of the boat to enter shallow locations, being small harbours etc. The keel is not designed to sail actually with it.
Therefore a solution in the direction of Van Oossanen's Models are more feasible.

[Dutch Peter]

D'Artois,

You're ofcourse completely right. I assumed that would become clear when watching the short film on the website of Jongert. You can't do any on the edge sailing when you change your draft with 2 mtrs and the related change in your CG.
But thanks for the extra note.

Kind regards,

[D'ARTOIS]

Sorry Peter, I didn't see their website just for now. Jan, if you come again with this kind of complicated questions give it hands and feet to play with. Your website is unclear to me and I am not able to read it well save for some words that are similar to Dutch, German or English.

There is a proverb in French that says:"le conseilleur est jamais le payeur" - the advisor never pays the bill - in so many words.

What you want matter of factly is a wingkeel. Now I am definately no expert of that kind of configurations but Van Oossanen is not far away and if you will be so kind to sum up the particulars of your boat together with a small drawing, I will find out for you what the best feasable option might be.

[SeaDrive]

The advantage of the wing keel over a bulb is that the wings function as a bulb and also improve lift. Most designs that are available with both wing and fin keels have a little more ballast in the wing version, to make up for the higher center of gravity.

Antonio Dias has designed a boat with a shallow draft wing keel with a board that lowers to greater draft when needed.

[sorenfdk]

Hej igen

Jeg er enig med alle de foregående indlæg, dog er det ikke nødvendigt at rejse helt til Holland for at få udarbejdet et forslag til en vingekøl eller hvad det nu ender med at blive. Der findes firmaer i Danmark, der har både erfaring og ekspertise på området - det vil nok være at reklamere lidt for meget, hvis jeg nævner et bestemt firmanavn her, men du kan finde et link under min profil

And for the rest of you: I agree with all previous posts, but it's not necessary to look for help outside Denmark - there are designers with experience and expertise in this area here, too! I don't want to mention any names, but there's a link under my user profile

[D'ARTOIS]

Soren, I cannot step in your shoes,answering for you, I can only speak for myself, but of course I appreciate and understand your answer.
Regards
Brien

[mistral]

have you tried to contact Beneteau?? from the picture i guess your boat is one from that shipyard, maybe a first 42 or similar; they develope a decent amount of winged keel, almost in "Oceanis" cruising line; they may suggest you a designer and/or a shipyard suited to your needs.
I've seen you've been here in Sardinia ! how did you finfd my windy island ?? crowded, i guess......

Mistral

[Dutch Peter]

Soren,

I have no intension of offering my services, I'm in an other line of bussiness. You're welcome to it, or better, let Jan decide.
Nice to see your not only stuck to the TP52 and related threads!!

Welcome back.

[Gaia_jan]

wow a lot off opinions. We dont want to sail with the sail in shallow water mode. I now that moving the part up and down are the expensive part, and I think that it need some more thinking regarding this problem. Now I want to see some of the suggested web pages.
Regarding Sardinia, we really loved the island in the Magdalena group of island, with great crusing water an not crowded at that time we were there.
Best regards
Jan Jensen

[Gaia_jan]

After have seen the side of Jongert, I think my idea is a little more simple.But If that keel can stand a full grounding with 7 knots, it is a brilliant idea by jongert. I guess they have an idea of the pricelevel of their keel. It really look expensive, for reference I would ask for an offer!
Best regards
Jan Jensen