Iron Keels Versus Lead Keels

[twofish81]

Dear all,

Can anyone please advice what are the pro and cons for both Iron Keels and Lead Keels? Besides the highmaintainance cost of iron keels, what are the advantages for iron keels?

As I know iron price is 6 to 8 times lower then lead, and regarding about the environment issue now a days, most of the people is moving away from lead keels to iron keels.

I'd really appreciate the advice from you guys that have so much experience.

thank you


Regards,
Clarence Leong

[sailingfool]

I think the advantage of iron keels is that they are less expensive for the builder, period. Whether that transaltes into a more affordable value for the buyer is for the buyer to decide.

[christyleigh]

Lead is heavier, doesn't rust, and will deform a bit if you smack into something. A friend of mine hit an underwater rock with his c36 at around 6kts which made a 4" gouge in the keel. No other damage (except him flying across the cockpit) to the boat so it was a simple re-fair that winter. That same hit to a harder iron keel - may have - done more damage to the keel connections and the people on board.

[Idiens]

I think it depends a bit on the keel. If it is a long thin foil with a bulb at the end, having a steel foil and a lead bulb might be a good idea. If it is a tandem keel with a bit fin, that the boat can stand on, maybe all steel makes sense. Otherwise lead seems to be the best choice. (Unless you can afford tungsten or depleted uranium).

[sailingdog]

As for lead keels... they're denser than iron keels, so provide more ballast for the same volume. A keel of equal mass and righting moment made of lead will be smaller and have less underwater surface area—resulting in a faster boat. The metal is more malleable, giving in the case of an impact. It is less likely to cause damaging corrosion. Iron expands when it rusts...leading to the breaking of encapsulating fiberglass... etc.

Overall, if you have to have a heavy keel... lead is really a much better material for it.


Idiens-

Osmium is denser than either tungsten or deplete uranium... in fact it is about the only metal that won't float on mercury. Tungsten is about 19.25 gm/cc and uranium is about 19.1 gm/cc—Osmium is 22.61 gm/cc, and not very radioactive.. but it is considerably harder than lead... so not as forgiving. Iridium is a close second to Osmium in density, and both are in the platinum metal family. It is very expensive... with the one stable isotope of osmium going for as much as $25,000 per gram.

[Idiens]

I didn't think your tri needed any ballast SD.

[sailingdog]

I keep some tungsten and lead aboard... in the form of buckshot and slugs to help repel PWCs... Amazing what damage a good slingshot can do with a .50 caliber Tungsten pellet.

Originally Posted by Idiens

I didn't think your tri needed any ballast SD.

[Idiens]

Wow! SD! You are even prepared for armour plated PWC!!!

[Rockter]

My own ship has a big fat lead keel encased in glass fibre.... the ship is a Union 36, with a modified-full keel. Now into her 30th year, the keel is zero maintainence, so far.... no visible corrosion, and no keel bolts!!!!

Cast iron is likely to be a good material too. Despite the association with steel (there is a lot of iron in steel !) cast iron really does have good corrosion resistance (witness raw water cooled Volvo motors... cast iron).
It is a rather brittle material though.

[sailingdog]

They have started using carbon fiber and kevlar in the high end PWCs haven't they???

Originally Posted by Idiens

Wow! SD! You are even prepared for armour plated PWC!!!