Keel bolts - melting lead
After successfully unscrewing nuts inside the boat - with the biggest spanner I could get in Biltema - it was high time to get to work on reaching nuts on the other side - in ballast keel.
My boat has iron keel. Unlike American-built boats, most Swedish boats with iron keel have bolts NOT going all the way through iron but instead they are ended a couple of cm from the top.
There are also versions where bolts are directly threaded into iron ballast. Luckily my boat is not one of them - removing such bolts is impossible without dropping the ballast.
Solution used by Arvid Laurin is to have bolts going through iron, a few cm, and end up in deep pockets. Here the builder will install washers and nuts on threaded bolt end.
On boats with cast which came out from foundry too light, the pockets are filled with lead. If opposite - too heavy ballast - filling is done with cement or wood.
In my case I have lead-filled pockets.
Filling has 2 functions:
to stop water from entering into bolt
to prevent nut&bolt from spinning when it is being re-tightened or unscrewed (to change washers or for removal)
Lead seems to be the best option indeed - adds weight to the ballast and is not permeable for water.
The disadvantage is that some day (like after 60 years) someone will need to remove it to get into the nut and this will be a hell of a job.
So here I am now, with hell of the job.
I’ve consulted with Janne Gustavsson - who has built my boat - on how I should proceed. Well, the best would be to melt the lead, he said. But you need to have a good gas burner for that - all this iron around will dissipate heat very quickly.
All right, I thought - so I buy a gas burner. And so I did - bought propan-butan torch and cheerfully tried.
Nope! With propan-butan I can maybe make creme-brulle for desert but it is too weak for this huge metal clump around.
Off again, I went to buy something stronger - the strongest in fact, if you don’t count acethylene-oxygen setup: MAPP torch.
Cheap it was not but hopes were high so I’ve tried with my new, heavy duty toy.
Weeelll - nope! Not so easy.
In fact I could see that lead is starting to melt but in the next second is was solidifying again. Too much thermal mass around, dissipating heat very quickly.
After blowing 2400 degrees C for 5 minutes into one point on lead it just got soft. Luckily though - this thermal dissipation protects the wood above the ballast but fire extinguishers were at hand anyway.
I then realised that this will not be like walking in the woods. Elbow grease is needed.
I’ve started with mechanical means, to see how it will develop.
It turned out to be quite possible to chisel into lead and cut away small chunks at at time. As long as I was on the surface it went pretty good but the deeper I went the more difficult it became - due to lack of space for tools.
After trying different ways of chiseling the lead I came to a hybrid technique: chiseling and melting.
At first it seemed easiest to make horisontal chipping and then melting lead which sticks out.
The idea is that by chipping the lead you get it separated from material around thus less likely to transfer heat too quickly to deeper layers. It worked quite nicely but after a while I’ve noticed that when melting the upper chips the lead flowing down stops on the bottom chips and solidifies again.
Obvious solution is to chisel vertically - and have gravity on your side.
This prove to work much better.
After I got deeper into the cast opening the lead dripping down is gathering on iron shelf and instantly solidifies again but is very easy to remove - it poorly adheres to rusty iron.
So now I continue my efforts in this way. Chiseling vertical openings, rising the lead and then melting it with flame. Works pretty well but we shall see how it goes when I finally reach this huge nut and bolt deep there.
It will be probably necessary to do the same on the other side of the ballast - otherwise I cannot free the nut from surrounding lead.
Well - I have a few months to do this - and 6 similar bolts after I’m done with this here.
Meanwhile I investigate if I can get even stronger torch. Worth trying!