Swing Keels -- Pros? Cons?

[Dockhead]

Thinking about my possible, hypothetical, new boat, which I would make for heavy duty, high latitude, long distance cruising.

I spent a fascinating day at the KM Yachts factory in Makkum, Holland, on my way back from the Baltic, in August, kindly arranged by CF's Noelex and SWL, and this yard is presently at the top of my list for my hypothetical new build.

Most of the boats they make -- and many of them are for the kind of duty I have in mind -- have swing keels.

I wonder if this is worth considering?

I've been living with 2.5 meters of draft, and other than in the Ijsselmeer, it has not really been a big problem.

But the next boat will be a little bigger (60' to 65'), and once we start to talk about 3 meters or even more, then this starts to be a different question.

And in any case -- any fixed keel is a compromise. A moveable one could be much deeper when down.

So despite the added complexity, which is very undesirable, I started to think that this might not be a bad idea. There are a few advantages that I can see:

1. Uncompromised deeper draft when down

2. Obviously, much less draft for shallow water.

3. Dry out.

4. Much easier to put the boat on the hard; much easier to get on and off the boat when on the hard.

5. Grounding is far less scary.

But disadvantages:

1. Complexity; cost; potential for failure.

2. No bulb; probably not ideally balanced and probably not hydrodynamically ideal either.



Am I missing anything? Views? Experience?

[Steadman Uhlich]

I have been interested in Swing Keel hosts since I learned about Damien 2 boats years ago.

There is a CF member that owns one, ISSUMA, with a red hull, and has sailed high latitudes in her. The member and boat name is ISSUMA.

That and other high latitude boats using them successfully have impressed me.

I think CF member LITTLECHAY would have good experience on them too, as he worked with Skip Novak.

Skip Novak's boat PELAGIC AUSTRALIS is what I consider an ideal design for that size boat 23m, and is a swing keel boat. Here is a link showing the keel.

Pelagic Expeditions Fleet Overview

I like the idea that if one has the keel down, and touches an uncharted rock in remote areas, there is a chance to raise the keel to get off the rock more easily or quickly. And if the keel is allowed to swing, the grounding could happen with little damage to the keel if it is not locked down at the time.

While I don't own one, I would like one.

[SV DestinyAscen]

I saw a very nicely done version on a small jenneau a year or two ago at the yard during commissioning. It will kick up if grounded and can continue to sail. Mechanism doesn't create risk of flooding keel/bilge. I can't remember what model it was... But it was maybe 35 feet?

If I were in your shoes I'll focus more on results as opposed to swing keel/shoal keel. Get the designer to do the numbers and go with the better performing one. Sirius yachts shoal keel don't sail any worse than their "regular" version and dries out nicely. More stable than a swing keel.

[Steadman Uhlich]

I also wrote a detailed comment with links about Swing Keels in this post:

http://www.cruisersforum.com/forums/...ml#post1854254

[Dockhead]

Originally Posted by Steady Hand

I also wrote a detailed comment with links about Swing Keels in this post:

http://www.cruisersforum.com/forums/...ml#post1854254

Thanks very much.

Note that my design brief is a bit different from this, and from Pelagic Borealis -- I want very good sailing performance, so keel should be high aspect and shaped as well as it is possible to shape a swing keel.

The KM Yachts swing keels seem to fit that bill, but I would be interested to know if the compromises in the shape affect performance much.

[Steadman Uhlich]

I mentioned those yachts, DAMIEN, PELAGIC AUSTRALIS, because of their size.

NOTE! ISSUMA has a blog, with a detailed post about repairing or maintaining his keel, including photos and good description.

Another aluminum expedition yacht is SEAL. 56'
Expedition Sail - Sailboat Seal

And I seem to recall that Peter Smith's (ROCNA founder)boats were Swing keels too, though I may be mistaken.

And most know about the OVNI.

And there is the custom or prototype KIRIBATI 36, which is similar to an OVNI, but simpler for lower cost.

[Dockhead]

Originally Posted by Steady Hand

I mentioned those yachts, DAMIEN, PELAGIC AUSTRALIS, because of their size.

NOTE! ISSUMA has a blog, with a detailed post about repairing or maintaining his keel, including photos and good description.

Another aluminum expedition yacht is SEAL. 56'
Expedition Sail - Sailboat Seal

And I seem to recall that Peter Smith's (ROCNA founder)boats were Swing keels too, though I may be mistaken.

And most know about the OVNI.

And there is the custom or prototype KIRIBATI 36, which is similar to an OVNI, but simpler for lower cost.

That's still far from any kind of performance keel.

I'd be looking for high aspect, and about 12' of draft I guess.

Something more like this:






But no saildrive! :gag:

[SV DestinyAscen]

Found it. 349.

http://www.jeanneauaustralia.com/ima...ey-349-G14.jpg

http://rs804.pbsrc.com/albums/yy322/...h=480&fit=clip

[fallingeggs]

Why not consider a lifting bulb keel? Seems like you could get one that also cants (awesome) or that telescopes so that it doesn't need a keel box inside the boat.

Tenderlift – Canting / lifting keel

Marine engineering and hydraulic design : Owen Clarke Design - Yacht Design and Naval Architects

I'd have to imagine either would be incredibly expensive

[UNCIVILIZED]

Originally Posted by Dockhead

Thinking about my possible, hypothetical, new boat, which I would make for heavy duty, high latitude, long distance cruising.

I spent a fascinating day at the KM Yachts factory in Makkum, Holland, on my way back from the Baltic, in August, kindly arranged by CF's Noelex and SWL, and this yard is presently at the top of my list for my hypothetical new build.

Most of the boats they make -- and many of them are for the kind of duty I have in mind -- have swing keels.

I wonder if this is worth considering?

I've been living with 2.5 meters of draft, and other than in the Ijsselmeer, it has not really been a big problem.

But the next boat will be a little bigger (60' to 65'), and once we start to talk about 3 meters or even more, then this starts to be a different question.

And in any case -- any fixed keel is a compromise. A moveable one could be much deeper when down.

So despite the added complexity, which is very undesirable, I started to think that this might not be a bad idea. There are a few advantages that I can see:

1. Uncompromised deeper draft when down

2. Obviously, much less draft for shallow water.

3. Dry out.

4. Much easier to put the boat on the hard; much easier to get on and off the boat when on the hard.

5. Grounding is far less scary.

But disadvantages:

1. Complexity; cost; potential for failure.
Maint. on: Trunk (inside & out), Board, Lifting Gear. But little of it is complex, but for fully dropping the board out once per decade. With but a tiny potential for failure. Such is far more likely to happen in the rig, or elsewhere. As I'm sure statistics would show. Especially given that there are literally tens of thousands of keel/cb trailerable boats out there.

2. No bulb; probably not ideally balanced and probably not hydrodynamically ideal either.
Board position is tuneable for ideal balance on any point of sail. To the point where very little, if any steering input is needed. Thus the self steering gear will have an easier time of things.

Clean, hydrodynamically. See RM Yachts. For example RM1270 - RM Yachts

Am I missing anything? Views? Experience?

Possibility of high speed potential, with better performance due to tuneable hydrodynamic balancing. See yacht Route 66, who's definitively a double-digit speeds type sailboat ROUTE 66

See rating of Keel/CB yachts vs their fin keeled sisterships. For example C&C's in the 40' range. PHRF New England - Handicapping - Base Handicaps

Of course all of this & more has been well proven in other boats, many of them mentioned here. Along with the concepts for same. And a search will turn up same in lots of previous threads on this topic. To include one on the Boreal yachts (as started by the OP?).

[nautical62]

I've owned 2 swing keel, and a number of fixed keel sailboats.

Pluses:

Low draft with keel up allows shallower water exploring, it means being able to anchor further in, not waiting for tide as often, etc. It provides another tactic in groundings. Lower to ground for dry storage (or transport)

Minuses:

More complex
Generally eliminates bulb keel and other such keel options
Raising and lowering mechanism failure potential
Potential leaking through pivot bolt or trunk housing depending on design
Lateral force may damage housing resulting in structural damage
Cranking the keel up and down can get really old.
Potential damage by travel lift
Atypical blocking required for dry storage.

Again some of this will vary depending on design.

[SteveInMD]

Great thread! I've been wondering if it's possible to build a swing keel that is engineered well enough and robust enough to be a serious cruiser. The Southerly system looks rock solid, but who knows?

[Dockhead]

Originally Posted by fallingeggs

Why not consider a lifting bulb keel? Seems like you could get one that also cants (awesome) or that telescopes so that it doesn't need a keel box inside the boat.

Tenderlift – Canting / lifting keel

Marine engineering and hydraulic design : Owen Clarke Design - Yacht Design and Naval Architects

I'd have to imagine either would be incredibly expensive

Would give great performance. Especially the canting one!!!

But neither of those would be any good for uncharted rocky waters. You need one which will swing back harmlessly if you hit something with it.

[Dockhead]

Originally Posted by UNCIVILIZED

Possibility of high speed potential, with better performance due to tuneable hydrodynamic balancing. See yacht Route 66, who's definitively a double-digit speeds type sailboat ROUTE 66

See rating of Keel/CB yachts vs their fin keeled sisterships. For example C&C's in the 40' range. PHRF New England - Handicapping - Base Handicaps

Of course all of this & more has been well proven in other boats, many of them mentioned here. Along with the concepts for same. And a search will turn up same in lots of previous threads on this topic. To include one on the Boreal yachts (as started by the OP?).

Thanks, encouraging!

I hadn't thought of balance-tuning with the keel position. Very cool.

[UNCIVILIZED]

Originally Posted by Dockhead

Thanks, encouraging!

I hadn't thought of balance-tuning with the keel position. Very cool.

Yes, you use it to alter your CLR. Though to get a reasonable draft in a bigger boat isn't all that tough, so a moveable keel isn't needed persay.
Consider that on a well designed hull, the canoe body draws 3' max, if not less. So then it's easy to keep the boat's draft under 2m/7'. Well, unless you're looking for racing performance. But even then...

Look at boats like the C&C with keel/cb's, where they do have true short keels, into which the CB fits. And done right, you can have a hydrodynamically efficient keel & rudder. Where the keel then houses a very efficent foil. So that between your keel/cb, & a high lift rudder, she'll sail quite well. And if you put the heavy bits down low, along with a bit of water ballast, then she won't want for Rm.

Though it is easier to get the weight down low if you don't have a moveable foil & it's housing taking up lead space in the bottom of the keel.

Dockhead, maybe with your thinker you should buy some design software, along with the VPP package. And then hire a grad student/design firm intern to help you play with it. So that you can play with various design features, & see what they add to or subtract from a boat's design in terms of speed.

The Dashew's talk about doing such things when cobbling together designs, in various places in some of what they've written. And there's a super abridged snippet on how it works in the design comments on a Class 40 here Class 40 “Icarus Racing” | Rodger Martin Design Click on the pull down tab at the bottom of the page.

And if your NA hates me, I'll deny that I ever told you to buy the software

Again, read the Dashew's, & also look more closely at some of the bigger racing & performance cruisng designs. None have hulls that draw much (water, as in canoe body draft), & the fins/foils on them mostly are oversized compared to other boats of their size. So it's all what you want to optimize things for.