Fin Keel Strength ?

[neilpride]

Originally Posted by Cheechako

Got any stat's?.... just interested. I hear of keel failures but havent heard of much lost lives... doesnt mean they dont happen though! A lot of what I hear is the go fast round the world racing boats etc....

Cynthia Woods a Cape Fear 38 competing in a regatta have the keel gone , 1 casualtie.

A bavaria 42 also have their keel gone and have 1 casualtie.

Moquini a sout african yacht founded without keel and 6 crew members missing.

There is more reports in the net Cheechako but im not going to post it,
fin keels are great in perfomance, like spade ruders , but need to be build smart and be tough , in many cases is not the keel who fail, the hull and structure is the culprit, Hallberg Rassy no longer build that tough and nice keel, same as Wauquiez , Amels have their keels bolted with 22 bolts in the maramu series, and you cant do much in this bolts because water tanks are integral with the keel stub, kinda funy but with 22 bolts why bother.
cheers.

[mr-canada]

Hopefully I'm not the only one seeing this simplicity to the issue.

If you are going to run aground so hard that you're going to knock your bolted fin keel off the boat maybe you need to pay better attention to your charts.

AFAIK the only number 1 big problem with keel design is those that have lead shot as ballast instead of moulded iron or lead. Run hard aground by accident which knocks a hole in the bottom of the keel and the ballast lead shot pours out like liquid leaving you with a keeled but unballasted boat - which equals a 90 degree heel in a hurry otherwise known as a really bad broach and that boat ain't righting itself.

While keel bolt corrosion is always an issue to be concerned about in my 26 those bolts are 1.5" in diametre and the bolts are about 3" in diametre. Its going to take one hell of a load to shear those 8 bolts off.

While sailing a tank is obviously safer, there are going to always be some weaknesses to any design. If you're concerned about running so hard aground youre worried about dropping your keel you need to either take a course in navigation and reading charts or perhaps go with a keelless boat that can be beached.

[K_V_B]

Originally Posted by vtcapo

The video shown of a production boat crash test is no indication that is would survive hitting a container or a reef. If I remember correctly the keel never hit the rocks.

Actually the keel is what hit the rocks, repeatedly, in that video.
The commentator mentions that despite repeatedly hitting the rocks there were no cracks, no leaks. There was only superficial cosmetic damage.
The only thing that really dented the hull was when it hit the pontoon, which would be similar to hitting a container I'd say.

My suggestion and this only applies to Blue Water, go with a full or modified full keel for cruising. If you are looking at more modern designs and speed and better performance is what you are after consider only fin keels with encapsulated ballast. Also, a rudder hung off a full keel will be there whereas a spade rudder will probably shear off if hit hard. Therefore of you go with a fin make sure if has a stout skeg hung rudder.

I've been rereading some of the stuff Steve Dashew writes about keels and rudders, and he makes a very good point that in a grounding a spade rudder is probably going to fare better than a skeg or keel hung rudder.

A spade rudder will probably just lose part of the bottom when it hits something. Completely shearing off is only possible if the blade has been designed stronger than the stock.
With a keel hung rudder the bottom support of the rudder is often vulnerable in case of grounding. If that support fails you quickly end up losing the whole rudder. The same applies to skeg hung rudders. The chances of something happening to a skeg or keel hung rudder that immobilises it is higher too.
If you devote the same amount of material a spade rudder will be stronger than a rudder with a skeg.
A spade rudder is a better, more efficient rudder too, as it leads to better directional stability as steering loads become a lot less.
Steve Dashew is a strong believer in building boats able to survive anything. He's probably forgotten more about boat design than you and I will ever learn. And he builds his boats with fin keels and spade rudders...

[Andrew Troup]

For anyone who plans to make a habit of running aground, (eg expedition yachts routinely working close inshore in uncharted territory) a strongly built metal boat with a well engineered swing keel (probably with hydraulic raise and lower) is probably your best bet.

[K_V_B]

Originally Posted by Andrew Troup

For anyone who plans to make a habit of running aground, (eg expedition yachts routinely working close inshore in uncharted territory) a strongly built metal boat with a well engineered swing keel (probably with hydraulic raise and lower) is probably your best bet.

In other words. An OVNI, or a Boreal.

[vtcapo]

Originally Posted by Jim Cate

It is amazing how many poorly designed, shoddily built plastic boats with bolt on fin keels turn up on the opposite side of the ocean from which they set out... with the keel still hanging down there where it started the voyage. Lots of those voyages were made by fairly inexperienced crews, too, so it might be that the boats kept them out of trouble when they made mistakes of seamanship like grounding or running into things... the things that happen to voyagers.

I'm not a big fan of the current batch of AWBs, but really, their fin keels seem to work pretty well. And a couple of years ago there were two Westsail 32s abandoned at sea because of some sort of damage to hull or rig. I don't remember the details and am not bashing the W-32... just pointing out that selecting examples of failures that have occurred does not necessarily condemn a design or feature.

So, vtcapo, being very sure that your sort of design is the only way to go seems to ignore the THOUSANDS of boats of other design philosophies that are going into "Blue Water" and amongst coral reefs... and returning intact.

Cheers,

Jim

Jim if you were to re-read what I wrote I said the safest design if grounded or hitting a container or reef is a full or modified full keel with encapsulated ballast. I don't think anyone except KVB will argue that point.

I would have no problem taking a fin with encapsulated ballast and skeg hung rudder across the pond as long as it is moderate to heavy displacement and built by a reputable manufacturer. The notion that "THOUSANDS" of fin keelers have made it across doesn't exempt them from the fact that they are more prone to maintenance issues and total failure.

A full or modified full keel is MY preference. What others choose to voyage in is their concern. I never said it was the ONLY way to go.

RT
PS When was the last time you read about a full keeler losing it and turning turtle? Guaranteed if you did it was bolted on....

[K_V_B]

Originally Posted by vtcapo

Jim if you were to re-read what I wrote I said the safest design if grounded or hitting a container or reef is a full or modified full keel with encapsulated ballast. I don't think anyone except KVB will argue that point.

The point I'm arguing is not what is safest, but what is sufficient. A tank will be safer in a collision than a Volvo. I prefer to drive a Volvo though.

A boat needs to be strong enough, not as strong as possible. And bolted on fin keels can be strong. Some yachts are grounding twice a day on bolted on fin keels...

[Pete7]

Originally Posted by vtcapo

A full or modified full keel is MY preference. What others choose to voyage in is their concern. I never said it was the ONLY way to go.

RT
PS When was the last time you read about a full keeler losing it and turning turtle? Guaranteed if you did it was bolted on....

So can you buy a new one of these yachts with a fully encapsulated keel, say from one of the large yacht producers?

Pete

[neilpride]

Originally Posted by Pete7

So can you buy a new one of these yachts with a fully encapsulated keel, say from one of the large yacht producers?

Pete

Probably not Pete, not many builders build anymore encapsulated keels, but is not the point, bolted or encapsulated, the point is if the keel is bolted with enough bolts to a wide and strong stub like a Nauticat or Amel as a example instead of a thin flat no stub hull laminated .. Cheers.

[goboatingnow]

So can you buy a new one of these yachts with a fully encapsulated keel, say from one of the large yacht producers

nope, you cant, why , they dont fail, and nobody but vtcapo wants one and a market of "one" isnt enough. today virtually all mainstream producttion from high end Oysters and Halbergs to mid market Bennys etc to entry level Bavarias and Hunters are external fin keel.

And the "maintenance" issues are no more then any yacht.

Dave

[neilpride]

Originally Posted by goboatingnow

nope, you cant, why , they dont fail, and nobody but vtcapo wants one and a market of "one" isnt enough. today virtually all mainstream producttion from high end Oysters and Halbergs to mid market Bennys etc to entry level Bavarias and Hunters are external fin keel.

And the "maintenance" issues are no more then any yacht.

Dave

Maintenance isues is another history, a full encapsulated keel dont have any maintenance schedule, 0... a bolted fin keel lets say have the joint to inspect, keel bolts retorque, corrosion in bolts, some builders still using iron for the fin,, corrosion rust, leaks in the bilge, etc.... yes a fin bolted keel have maintenance isues and a encapsulated keel is free of maintenace .....

[goboatingnow]

Maintenance isues is another history, a full encapsulated keel dont have any maintenance schedule, 0... a bolted fin keel lets say have the joint to inspect, keel bolts retorque, corrosion in bolts, some builders still using iron for the fin,, corrosion rust, leaks in the bilge, etc.... yes a fin bolted keel have maintenance isues and a encapsulated keel is free of maintenace .....

I have seen encapsulated keels that have minor damage weep water and cause untold hidden problems. Ive seen damage to encapulated keels that required major rework, whereas in a lead bolted on keel, virtually nothing was needed ( didnt look the best cosmetically).Ive seen encapsulated keels weep vast quantities of rusty water from internally corroding ballast.



when an minor impact occurs on the GRP surrounding the ballast, you may have compromised the coating, at least on a fin keel all that happens is a ding in the metal ( if that).


Maintenance on fin keels is no worse then maintenance on other parts of the boat.

The fact is bourne out by the fact that the vast multitude of production boats are using such keels and they do not give trouble on any sort of regular basis.

why why is it that people seem to want to run down perfectly good technology and return us to the model T.

External keels and internal keels all have compromises, like everything on a boat.
Dave

[Pete7]

Originally Posted by neilpride

Probably not Pete, not many builders build anymore encapsulated keels, but is not the point, .

This is exactly my point, higher manufacturing costs without a real need have consigned long keel hulls to history unless demand from yachties changes, which is unlikely. So the choice is lots of new or secondhand fin keeled yachts or some manky auld boat (MAB) with a long keel. We have to accept that if you want a second hand but newish yacht in the future it will have either a fin keel or or two hulls.

Pete

[neilpride]

Originally Posted by goboatingnow

I have seen encapsulated keels that have minor damage weep water and cause untold hidden problems. Ive seen damage to encapulated keels that required major rework, whereas in a lead bolted on keel, virtually nothing was needed ( didnt look the best cosmetically).

Maintenance on fin keels is no worse then maintenance on other parts of the boat.

The fact is bourne out by the fact that the vast multitude of production boats are using such keels and they do not give trouble on any sort of regular basis.

why why is it that people seem to want to run down perfectly good technology and return us to the model T.

External keels and internal keels all have compromises, like everything on a boat.
Dave

Ok, water coming from a internal encapsulated keel is not a maintenace isue, is a problem , please explain the other problems,, most water problems in internal encapsulated keels come from groundings , in any case this problems dont put the boat integrity at risk when in a fin keel boat yes, in other words 3 or 4 groundings in a encapsulated keel can flood the cavitys in the laminated but the boat can be safe until repairs are done , same groundings in a fin keel boat can deform the lead if the keel is lead or destroy the internal grid, or bend a bolt or open a crack in the joint ,,,,and the repairs are far more worse than in a internal encapsulated keel,

As i say 5 or 6 post ago we have here in the boatyard 3 fin keel monohulls fairly new with serious keel problems , the guy from the Etap38i is crying right now, he cant understand why such a problem in a fairly expensive boat and the guys in the boatyard cant understand why such a problem in the keel area , further investigation and questions to the owner reveals that the owner run hard aground 2 times in the med 1 year agoo , now we have a internal grid system broken loose, the tabbing broken , 1 bulkhead loose, a masive gap crack open in the aft trail edge , water intrusion explained by the owner , a bilge pump working every 10 minutes , and a expensive bill to fix it properly, because keel need to be droped , mast down and a couple of grinders working hard inside.

Good technology my ASS dave, many boats use this technology well , other are just playing lame with future owners,, Fin keels YES, but well designed and well buil it...

[Freerider]

Are keels ever bolted on and encapsulated in fibreglass?

Lifting the keel off is the only thing I'm not going to do before relaunch, so naturally its the only thing i wonder about.

I was thinking if it was also glassed to the hull it would just add to the safety factor.