lag time

Well if you say so and you've done it before, but I would be concerened.

Its not something ive thought about before, but I would have thought that they were cast in.

 

Lead shrinks considerably when it cools and though "J" bolts can be cast in it and commonly are, the Columbia keel is bolted on. You wouldn't be able to cast bolts in place and expect them to form usable threads, unless it was a special, very deep thread. "J" bolts work, not because of the tight grip the cooled lead has on the bolt, but because of the mechanical advantage the bolt shape has within it's hole (self binding). On some keels you'd see the bolts, all welded together to an armature, forming a support for each other and also a mechanical lock to prevent withdrawal when the nuts are taken up tight. So, yes, they can be cast in, but this means a lot of trust in the foundry that is pouring your ballast, to have the bolts in the proper locations to fit the hull. Whereas if cast without the bolts, you can drill down through a jig and insure the bolts will be where you need them.

 

the keel

I'm back.
I was putting new shocks in the car so I didn't get a chance to look at the thread til now. Wow! some interesting input.

Par, it sounds like you know this design. I am relieved to hear this was not some one-time hangar design that is ready to drop off or fail.
I have surfed the web for about a year now(unfortunatly my only source of data) and not heard any alarming stories about Columbia 36 keels. The boat does have it's share or shortcomings though, but it's fast for and old timer

I have the squarish keel(see attached pic) My hull # is 44 but that's only from some piece of paper I found on the boat. I read that the early boat's keels were an experimental design that was not satisfactory to the designer. It was sold to me as a 1968 model but my owners manual has drawings in it from 1972, and the keel design details sheet and specs are missing.

Some more details of our intensions:
We plan to drill for 1-1/8" machine threads. I think that's 7 tpi:?:
If we can get the old bolts loose then we will use the old locations.
I don't know if the factory used self tapping style lag bolts or what so we will just go oversize and use machine threads.
We will use ann old 1-1/4" prop shaft and cut it into four studs. I can only imagine what this would cost to order , but we got it and we're gonna cut it. The rest of the studs will have to be replaced as we get more stock. I want some good bronze for this.

Par, thanks for the tips on tapping fluid. I have lots of experience tapping in steel and iron and Al but not lead. I think I will tap a bunch of holes in my extra diving weights so I can get a feel for it.
If you know this boat design at all and want to chat, I'm all ears. Can you tell me what is the MK II?

Thanks for the interest,

Russ

ps: I think the ballast ratio is around .43 but details are sketchy.

 

I still cant see my way through the whole job of taping into lead . Like you say if you get the tap jammed!!!! OH.

I would I think prefer the toggle method because I can see it working,-- lining up,- and most of all having strength. You would also be able to easily remove or replace as you wish without removing the keel. Something a surveyor would appreciate.

 

This might sound nuts (pun ) but those bolts really don't look that bad. You can still see the threads quite clearly, so the shanks of the bolts are as yet basically untouched by corrosion.

There are many standard taps available above 3/4 such as 7/8-9 , and 1-8 as well as 1-10, before you drill all the way out to 1-1/8 or bigger. If you want to stop future corrosion in the threads use an anti-corrosive/anti-seize coating like Mastinox.


Jimbo

 

Tapping threads is like approaching wildlife.
It's not for the uninitiated, You must always watch for warning signs, back off when you hear a growl, and never show fear—they can smell it.

 

Okay Russ you probably have the "Scheel effects" keel, unless you've been upgraded. Later versions of the keel looked like a truncated shark fin, which was the trend at the time. Ballast ratio was in the mid to high 30's in cruising trim, but as delivered it was 43% (bare bones, and an empty boat).

Contact Columbia (now reorganized and marketing a 30'er I think) or possibly Dick Valdes and see if they have some records laying around about the bolts.

 

Thanks again,
I bet if Dick Valdes wrote up some notes and self published a book featuring all the old designs he worked on, he could sell one to every person that is maintaining an old Columbia.

I always though the the swept back hook shape was the Scheel keel, but this makes sense now. My boat is a low hull #(44)

It sails well enough for me, but it would be fun to sail on a later MK II to look for differences.

cheers,
Russ

 

The Scheel keel will have a "lip" of sorts along it's lower edge, which parallels the LWL.

 

For the sake of quality, let's hope he's willing to accept payment upon delivery, and not insisting on being paid up front!

 

method for tapping underdifficult circumstances

if you can make drill and tap blocks, which are blocks of metal with the tap drill size drilled through it and the tap size which will probably be slightly larger than the nominal bolt size

fasten or clamp these to the keel to guide the drill and tap

the drill should feel slightly dull on the cutting edges or youll have a problem with id grabbing, take a stone and dull it if need be, wont take much but you dont want a sharp feather edge on the drill you want to have to apply a bit of pressure on the drill to get it to cut and make sure the shoulders are not sharp

when tapping try black cutting oil, the kind used for threading pipes.

go slow and remove the tap completely often and with a wire rod bent into a hook clear the hole completely of any cuttings some time a long extension drill

of about 3/16" that will reach the bottom of the hole and not touch the sides .
use it in a drill motor and turn it moderately fast to break up any chips that may become packed in the bottom of the hole

chips will be your worst enemy so keep the hole clean of them and sense its lead you may also consider going in first with an under size tap then finishing with the on size tap as the lead may squeeze in

 

When loaded in shear, it probl'y wont matter much but any bolt you can make on a lathe by cutting the threads, or by using a die to cut threads in a piece of bar stock will be far inferior in strength to one made in a factory by thread rolling.

Jimbo

 

Tom,
The machines get shut off at happy hour

wardd,
It sounds just like drilling in uhmwpe—that stuff can grab you tool too.
I like he blocks idea. That black cutting oil smell will always remind me of salmon canneries or old boat sheds

Jimbo,
the critical feature (if that) is the pull-out strength of the lead threads, And we're going oversize from original there.

chin, chin
Russ

 

The original arrangement seems to have worked quite well. Kerosene was the old school lubricant used for drilling and tapping lead, which I don't recommend of course. I'm fairly confidant they used a fine machine thread bolt. The pilot hole is generally bigger then usual for the tap when cutting lead. I've snapped both taps and bolts in lead holes, it's pretty easy to do, so work slow and clean.

 

I would suggest doing some practice on some lead before moving to working on the boat.
I do not believe you need to tap for lags in lead, you just need to have the hole the right diameter for the area where the threads are. That is what is required in wood also with lags. But the hole size could be different for lead.
I would not make 'custom' threaded bolts. Lags bolts and hanger bolts such as you have on your keel are highly developed and engineered items, even if they do not look like it. For instance, I have been told that they are designed to hold at least the tension strength of the bolt if the threads are embedded six times the diameter of the bolt.
Folks who are emphasizing how difficult drilling and tapping lead is are exactly right.
I also hope you are not going to all this trouble to cure something that is not a problem. Of course curing anxiety about the bolts may be just as important as fixing the bolts themselves.