Fin Keel Strength ?

[goboatingnow]

This thread is just circular at this stage. I never understand the motives of those that advocate long keels.


The fact is that the majority of fin keels do not give trouble. The part is not troublesome. Yes of course it's checked like all other parts of the boat. But that's it. Should you be worried , unless you have some specific knowledge , no of course not, and the vast majority of cruisers are not worried.

Dave

[cal40john]

Originally Posted by Don Lucas

I doubt that it is less expensive to have a foundry make up a casting into a shape, melt and pour in a bunch of lead, have keel bolts cast into it at very specific locations, and ship it to the boat company, than it is to:

glass in a keel shape, stack some metal bricks into it or pour a bunch of shot into the keel and then to cover it with some epoxy or fiberglass etc.

I don't believe that many of the older designs cheaped out on the ballast. I have done keel repairs on an Islander, a Bristol, and a Cal. These are encapsulated keel designs. These were all damage through the glass to the lead inside. The lead conformed to the shape of the keel in the exposed area.

This article describes a cast lead ballast in the Cal 25:
Seal's Spars & Rigging: Cal 25 Used Boat Evaluation

I can't find it now, but I've seen a brochure for Cal where there is a picture of a keel shaped single piece of lead being lowered into the boat during construction. IIRC I've read that resin was then poured around the lead to fill the gaps and then the top was fiberglassed over into the boat.

John

[barnakiel]

Originally Posted by goboatingnow

(...) I never understand the motives of those that advocate long keels. (...)

- speed,
- pointing.

Both easy to understand and justify in the racing aspect.

However, my perception is that, in the cruising context, the fin keel has been introduced due to manufacturers finding it easier/faster/cheaper to manufacture (either the appendage, or else the whole design becomes cheaper, if a fin keel is designed into it).

Nearly all modern cruising boat designs (ban some single one-off productions) are cost-driven.

b.

[sailorboy1]

Morris is a pretty expensive boat, they are using fin keels and ............ spade rudders.

[Randyonr3]

Designs change through the years and boat keels are no exception.
Might be for sales, maybe production costs, but they do change.
And I know personally of a Passport with a full keel that will run circles around
Most fin keel boats built. But I've also been on fin keels that have more stability
than any full keel heavy weight.
To pick a boat based on its underwater design is ,IMO, the wrong place to start.
And when we chose a boat, and many know this, it was a choice that narrowed down to
two boats, A Hans Christian 38 MK ll and a FIRST 38. Then I sailed them both, and decided on the FIRST . Odd thing that our decision came down to two boats so different in design and performance but very close in creature comforts. And that's only me, ended up buying the 42. Same layout, just larger.
Just trying to get the point across that you may be set on a full keel boat as the design is a favor.for many cruisers, only to find a very bad handeling boat. Same.goes for the fin for performance, you could find a pig.

[noelex 77]

Originally Posted by barnakiel

- speed,
- pointing.

Both easy to understand and justify in the racing aspect.

However, my perception is that, in the cruising context, the fin keel has been introduced due to manufacturers finding it easier/faster/cheaper to manufacture (either the appendage, or else the whole design becomes cheaper, if a fin keel is designed into it).

Nearly all modern cruising boat designs (ban some single one-off productions) are cost-driven.

b.

A bolt on iron fin keel is certainly the cheapest option. An encapsulated lead filled fin keel with a skeg hung rudder is likely to be the most expensive construction method.
Long keels allow considerable savings in not having to produce separate support for the rudder and prop. In addition the chord length and modest performance expectations of long keels encourages the use of cheaper ballast materials which is often taken advantage of.

[daddle]

I would think a bolt-on lead keel would be the most expensive. Casting, machining & fairing a lead keel to proper shape must be more expensive than laying up a hollow keel to accept a rough casting. The most expensive boats tend to have the former while cost-conscious boats the latter.

[neilpride]

Doesnt matter if is cheap or expensive if is properly build it and design ....

[noelex 77]

Originally Posted by neilpride

Doesnt matter if is cheap or expensive if is properly build it and design ....

I disagree. Keel design and materials are a fundamental property of a sailing boat.
Yacht manufacturers would like us to notice the new colour scheme on their latest model. They don't like embarrassing questions about construction methods, but these are important characteristics that will determine the performance, safety, maintenance, and value for money.

[Cheechako]

If you have ever observed a hull with encapsulated keel being laid up, it is difficult at best to get in the keel and do the layup. Some hull molds are split to allow better access and then bonded together afterwords. This is one major reason that newer modern designs have bolt on keels, you just cant make a good performing thin wing well if you are laying up an encapsulated keel. Lets face it, a 12-20" wide (thick) keel isnt the best for performance, and when it's longer, it's just more wetted area. A balanced spade rudder gives an easier helm and better steering.
Doesnt mean modern is better for all purposes, but comparing performance of a long keel boat to a modern design is like comparing your favorite 57 chevy to a new BMW. On the road there's no comparison.... except the looks you get from other gearheads!!

[Bash]

Originally Posted by Cheechako

If you have ever observed a hull with encapsulated keel being laid up, it is difficult at best to get in the keel and do the layup. Some hull molds are split to allow better access and then bonded together afterwords. This is one major reason that newer modern designs have bolt on keels, you just cant make a good performing thin wing well if you are laying up an encapsulated keel. Lets face it, a 12-20" wide (thick) keel isnt the best for performance, and when it's longer, it's just more wetted area. A balanced spade rudder gives an easier helm and better steering.

Agreed. It may well be that considerations about strength and expense are a wash, but it terms of performance the bolt-on keel will always be superior.

[noelex 77]

Originally Posted by Bash

Agreed. It may well be that considerations about strength and expense are a wash, but it terms of performance the bolt-on keel will always be superior.

When discussing performance we need to distinguish the type of Bolt on keel.

The common bolt on iron keels generally have poor performance. The low density creates only a poor righting moment and the frequent lack of any aerodynamic cross section means the thin plate is inefficient and stalls at relatively low angles of leeway.

[Bash]

Originally Posted by noelex 77

When discussing performance we need to distinguish the type of Bolt on keel.
.

Fair enough. I've been assuming the conversation has been about lead keels, whether bolted-on or encapsulated, but there are numerous exceptions in either case of less dense material being substituted.

[neilpride]

Originally Posted by noelex 77

I disagree. Keel design and materials are a fundamental property of a sailing boat.
Yacht manufacturers would like us to notice the new colour scheme on their latest model. They don't like embarrassing questions about construction methods, but these are important characteristics that will determine the performance, safety, maintenance, and value for money.

Thats what i say, cheaper or expensive there is ways to make it properly,
builders dont need thousands of dollars to include in the mold a stub or a real grid system to spread loads evenly, is a matter of save costs in the production line, as i say before not many new buyers ask for cutouts samples from the hull, now how is posible to glue a 4000 pounds of lead in a 6 mm hull thicknes properly?? because everything is nice and shine when the baby leave the mold and the guys drill holes in the hull to bolt the fin, long time agoo builders have in mind all the posible consequences of collisions , groundings, pounding, thats why old vintage boats are build it like tanks , today , boat builders are looking at the numbers, is really hard to found in the net a encapsulated keel boat loosing the ballast, or fliped, instead the net is plagued of cases , people asking why the crack, how to fill it, why my bolts are corroded , do i need to drop the keel etc... the worst example of how to do it bad is to fit a deep and thin section of fin keel to a flat surface bottom without a strong structure inside, and many junk are build this days like that....Later the brand get bad reputation, but thats ok because many new buyers are not aware of the problems, thx to the forums people know whats going on with certain model, take as a example FP and the osmosis ****.....
Cheers...

[endoftheroad]

This picture may be disturbing to a "performance cruiser" but that 1974 lead encapsulated keel really does it for me.