Join Date: Nov 2011
Thanked 0 Times in 0 Posts
Rep Power: 6
Re: Replacing lead Keel bolts
Sweet! I have been thinking about this.
I dont think I will be able to drill perpindicular, intersecting holes precise enough to do the window method. I will end up with over sized holes to get my studs to thread into dowel nuts.
There are currently six 1/2-13 studs casted into the keel which weighs 1400 lbs about.
The largest hanger studs I can find are 1/2-13, 6 in long, with the lag portion 3 inches long. According to my calcs, the pullout strength in pure lead is about 6000 lbs. With the boat at a 90 degree heel, the tensile load on the 2 out board bolts is about 7000 lbs. That ignores the fore and aft single bolts. So thats 3500 per bolt. If you want the preload to be higher than the joint separation load, we exceed the pull out strength in lead (conservsative).
So, I am going to use six 3/4 dia by 6" stainless Lag bolts. Pull out strength on each one is 13700 lbs in pure lead with 4 inches of thread engagement. This will allow my preload to be 2x the joint sep load and still have a large margin of safety. I will torque these to 100 ft lb, and use Bellville spring washers under the head that flatten out at 5100 lb of preload, so I have a visual indication of adequate preload.
These will also be easy to install. So, I think this is the best approach. Catalina should have hired me.