Visit our Popular Forums

colo.sail · 05-02-2010, 15:45

still building this thing but oh so close to pouring the keel. Should I use Stainless or Bronze keelbolts (plans call for 1/2Inch)

AND - should keelbolts in lead go clear through keel or can they be embedded during hot lead stage?

Thanks

sailvayu · 05-02-2010, 16:40

I am sure there will be a lot who will disagree with me on this but I would use plain steel. Bronze is good but a soft metal and will stretch. Stainless steel suffers from pit and crevice corrosion. I had a Contest 25 built in 1962 with steel keel bolts In 2000 I removed the keel due to a failure of the wood filler. The only bolts that were bad were 2 in the area of the soft wood, the other 4 only had a slight surface rust. Builders for 100's of years used steel. Only recently have builders switched to stainless and that is because buyers who do not know better think it is better. Of course I also hear of more keels falling off now then I did when I started in this business.

Fair Winds

sildene · 05-02-2010, 19:54

Quote:

Bronze is good but a soft metal and will stretch.

Sailvayu, any reason you could not simply increase the thickness of bronze bolts to counter stretching? After all, some turnbuckles are bronze.
Is there a metallurgical issue with the use of bronze nuts/threads with the loads involved?
Have to like the idea of bronze keel bolts - no rust, no crevice corrosion; should last a while.

Martin

sailvayu · 05-02-2010, 20:00

No reason I can think of other than cost, but now that you mention it I have never seen it done.

Fair winds

CarlF · 05-02-2010, 20:08

You can make a plenty strong keel bolt from either. Equal strength bronze bolts will be a little thicker than stainless. Good bronze is about four times the cost of stainless so most boats are built with stainless to save money. Bronze will last pretty much forever while stainless may develops crevice corrosion ten or more years out because the keel stub area has little oxygen. Stainless below the waterline is fairly recent. Herreshoff designs used Tobin bronze for most underwater metal including keel bolts.

My advice would be to consider how difficult it will be to drop your keel to inspect the bolts. In some boats, the bolts are easy to reach. In others you need to take a chain saw to the interior to get at all of the bolts. In the latter case, the extra cost of bronze might seem pretty smart.

Carl

delmarrey · 05-02-2010, 21:18

The best for the money is 316L. Mine are 30 YO and still strong.

MarsKeel - Technology

S&S · 05-02-2010, 21:24

On ours, primaries are bronze and others were added later that are stainless (acme threaded). no problems with either.

If I were doing new, i'd go with bronze and make them through bolts- embedded bolts are impossible to replace.

**James S** · 05-02-2010, 23:43

Bronze

colo.sail · 06-02-2010, 19:09

I was thinking Bronze - except for the price
BUt like one comment here - the design doesn't allow easy access/replacement. They would be embedded during the pour.

One more question. Plans call for just FOUR 1/2 inch keel bolts. Really - its 1800 pounds just hanging out there. How do you measure what would be needed?

**Jim Cate** · 06-02-2010, 19:16

Seems to me that it depends greatly on what type of keel we're talking about. If it is a lead "shoe" along the bottom of a long keel then the bolts only have to support the weight of the ballast, and perhaps the 4x1/2" would be OK. But if it is a fin of any sort where the bolts are subject to great stresses when the boat is heeled (due to the lever arm effect of having the ballast at the bottom of a deep fin), then they seem woefully inadequate.

Cheers,

Jim and Ann s/v Insatiable II lying Broken Bay, NSW, Oz

colo.sail · 06-02-2010, 19:21

I guess is how you'd explain it. Thanks Jim.
It is about 6 feet long x 1 foot deep - tapers from 9 to 3 inches - so not a lot of external pressure on this thing. Just hangs on the bottom. It also has some deadwood fore and aft that will give some measure of support

Melting all those damn wheel weights - just hate to see it fall off first time in the water

delmarrey · 06-02-2010, 19:22

Quote:

Originally Posted by colo.sail

I was thinking Bronze - except for the price
BUt like one comment here - the design doesn't allow easy access/replacement. They would be embedded during the pour.

One more question. Plans call for just FOUR 1/2 inch keel bolts. Really - its 1800 pounds just hanging out there. How do you measure what would be needed?

That would be an engineering question that only an expert or boat manufacturer should answer!!!!!

Again: MarsKeel - Technology

**Jim Cate** · 06-02-2010, 19:33

Quote:

Originally Posted by colo.sail

Melting all those damn wheel weights - just hate to see it fall off first time in the water

G'Day Colo,

Been there and done that! Was involved with the casting of a 4 tonne bulb keel, all from scrap lead, of which about 2 tonnes were wheel weights. They are a MESS when you melt them! Lots of dirt lodged behind the clips, so that you have to skim a huge lot of crap off the top of the puddle, to say nothing of the clips themselves. YUCK.

Have fun, and good onya for doing it yourself... do remember a good respirator for you and anyone involved in the process.

Cheers

Jim