Caulking / Red Lead Putty

Hi.... Over the past year I've been extensively restoring or should say rebuilding a 1940's 'Shakespeare Class' Ex-admiralty Launch (48ft). I have no experience of boatbuilding so have relied on books and internet articles etc.. which has worked well up up to now..

The hull is copper roved throughout and consits of a mixture of pitch-pine & larch carvel planks on steam-bent oak frames. Below the waterline the hull is sound but I've had to replace almost 2/3 of her topsides (approx 600ft) and a large quantity of frames (approx 1ft intervals). All copper roved.. and yes me and my oppo now have arms like popeye!

Could someone please advise on the correct procedure / timing between processes when caulking / seam sealing a carvel planked hull

My question is this...

What state should the putty be in when the boat is put back into the water..??

I am using 1/2 kilo balls of Caulking Cotton (8 strands) and red lead putty made from 16 parts linseed oil putty to 1 part red lead powder (as red lead powder manufacturer recommends) The cotton has been driven into the seams with an iron until hard up against the back of the beveled seams, then left for 2 days to ensure it doesn't uncoil and spring out. I have done a couple of test seams with the putty before completing the boat... The Red lead putty has been spread into the seams using a putty knife..

However I've recieved conflicting advice on what to do next and could do with some guidance.

From what I've read the watertight skin is formed by compression, the planks take up water and swell around the cotton..

What state should the putty be in when the boat is put back into the water..??

I've been told I can paint over the putty when it's formed a thick skin and put the boat back in the water for the planks to swell.

However to my mind, If the putty is still at all plyable it will be squeezed out of the seam as the planks take up water and swell or is this the point ?? should excess putty be slowly squeezed out as the planks swell, leaving only what each seam requires at maximum swell??

if this is the case should I just apply a single coat of primer, go back in the water for a couple of months whilst the planks swell, then sand back the now hardended splurge of excess putty along the seams, then re-prime and apply topcoats before going back in the water?

Or

Do I wait until the red lead putty had gone rock solid (linseed oil putty manufacturer states this is approx 28 days) then sand back the excess, apply undercoat and topcaots etc, then go back into the water?
This also doesn't seem to sit well with me. Wouldn't the rock solid putty fracture / crack away from the seams during both lifting and swelling?

Having seen a very unsightly boat with a very expensive paint finish with about 5mm of rock hard splurge underneath which had spilled out along each seam and also heard horror stories of overcaulking breaking frames, fasteners and planks sliding about, I am now very concerned and obviously want to employ the correct techniques and proceedure.. However to me if caulking causes frames and fasteners to break and allow planks to slide about there must be a much more serious constructional problem present...

Anyway, [B]what is the traditional technique? [/B] Nothing I've read mentions anything about the 'state of the putty' nor anything regarding timing regarding going back into the water...

I'm now working on my 48ft boat single handed so the 'state of the putty' is a concern. If it has to go back in the water plyable I am going to need to get some help filling the seams as by the time I get close to the finish the first seams filled will be rock hard anyway!!

Please Help....

All advice would be gratefully received...

Many thanks

 

I have never used red lead putty on seams so someone who has may improve on what I will say.
Typically you want underwater seam compound to stay pliable. As the edges of the underwater planks come together some by absorbing water the compound will push out and make a ridge higher than the surface of the planks if you leave the compound flush with the planks. So what I do on each seam after I put the seam compound in is to drag a short piece of smooth metal rod whose diameter is such that about a quarter or a third of its circumference matches the seam width along the seam to make a depression which leaves room for the compound to move out some without standing proud of the surface; hopefully. You will be holding the rod at a very low angle in the direction of the seam as you drag it along and can collect what comes out for the next seam.
I would do the underwater seams last in your situation so they are softest when you put the boat in the water.
I also advise you to prime the seams with paint right after caulkiing and not put any compound in until just before you paint the bottom or very close to when you paint, say a few days perhaps.
Seam compounds for bottom seams I have used include linseed oil mixed with cement, roofing tar, and Interlux and Petit seam compounds. For topsides I have used linseed oil putty and also Interlux and Petit products.
No doubt there are other good concoctions I don't know much about.
I do hope you have not put too much cotton in the seams but I can't tell about that without being there.

 

I forgot to mention if the seam compound tends to drag too much on the metal rod lubricate the rod with linseed oil as you go along and that should take care of that issue.

 

Many thanks for your reply Gilbert... That makes sense for the underwater seams. I will certainly attack these last... What about the topsides though? What state shoud the red lead putty be in for these? Hard or pliable?

Regarding the quantity of cotton used. The 8 strand cotton when twisted together is approximately 5mm in diameter, however on one of the larger seams (where I could see inside the boat!) I had to use approx 8mm to allow it to bite the back of the seam and prevent it going all the way through... I have so far only done a few seams to test whether caulking was a job I could handle myself.. The majority of cotton removed from the old planks was no greater than 5mm so have used roughly the same. See pic



The puttied seams are directly behind a section of the boats rubbing strake which had to be replaced, so these needed to be done now in order to fit the rubbing strake.. The puttied seam is approximately the same size as the others in the image, I just managed to get the putty all over the planks... any help on NOT getting the putty over the planks would also be welcome.. As, these seams are behind the rubbing strake and I thought the putty was to be left to go hard I assumed sanding back here would be ok..

Also I forgot to ask in the original post... I have lots of old fastener holes that need to be plugged/filled... I've been told that I can just make up either larch or pitch-pine plugs (i.e. the same as the plank with hole) that are slightly larger than the hole and hammer them in... should these plugs be epoxied or are they ok on their own? what is the standard technique for old fastener holes?

Again, many thanks for your kind help

Tom..

 

you can mix epoxy resin & sawdust to fill the nail holes
you can caulk the seams, paint them, then fill with r l putty in one day
whatever settling down / cracking of the seams will happen anyway

 

After hearing your description of the amount of cotton you are using I think you are probably doing fine.
You can rub the excess putty off with a rag after you have scraped as much as you can off with a putty knife. Using a little linseed oil with the rag will help where the rag itself won't do.
The traditional plug should be dipped in white lead or primer before inserting them. They should be a snug fit but they don't have to be so very tight. The down side of using epoxy and sawdust for plugging hoes is that is is difficult to remove and as it is harder than the surrounding wood it makes sanding the hull troublesome and sanding will be required because you have to overfill the holes just as you would for some other filler.
I would like to hear someone who has used red lead putty for seams comment on the above water/below water hardening issue.

 

You should paint the seams before applying the putty. Otherwise the wood will suck too much of the oil and the putty will be dry and crumble. Also, the putty should never be "rock hard". If it is , the movement of the planks will crack it and make it loose. Putty should always have a little pliability.

 

why do you presume i havent used red lead putty

 

Its reassuring to know that the amount of cotton being used is ok.. As a first timer it has been a great worry!

If you look closely you'll see that the top edge of each plank has been painted with Jotun Vinyguard Silvergray 88 Metallic Primer.. but only the top edge.. I was told by a few people including the boatyard where I'm located to leave the other edge... Is this incorrect? I've left tails on all the caulked planks so these could easily be removed allowing me to apply a coat of paint before continuing with the caulking..



I have loads of work to do before I need to caulk / putty the entire boat, I just needed to do the seams behind the rubbing strake to allow this to be fitted..

For the time being I scrape off the excess on the planks then drag a short piece of smooth metal rod along the seam to make a depression leaving room for the compound to move out some without standing proud of the surface, as described by Gilbert.. and apply a couple of coats of primer before fitting the rubbing strake.

Many thanks for the advise guys and anyone else who can add any experience in this area would be most welcome.. I'm sure now I've joined this forum I will be asking for help again on a variety of topics! As a newbie to boats there is so much I don't know!

Kind regards

Tom..

 

I have always painted both sides of the seam. Everyone I know does the same. If you leave a small depression on the putty it should come more or less even when the wood swells. Soft woods swell quite a lot. By the way, nice seams.

 

Thanks Gonzo... there are some far less neat seams between the old planks though! For now I'll remove the cotton from the caulked seams (there's just 5 seams done I think) apart from the 2 puttied seams behind the rubbing strake and give all the new planks a once over with primer before tackling the rest at a later date..

 

Where in the UK is your boat?

 

I was taught to cut a suitable length from the ball of cotton around 20ft & separate the strands into whatever number required often four of five, then spin it up with a hand drill into a rope. The rope was laid into the seam or choked in little loops hanging down then set down in stages, this way if the seam varies in width as often happens with old boats you just close the loops up & choke more in as the seam gets wider. We always painted the cotton with pink primer or red lead primer before puttying.
Its important not to drive it in too hard especially if she hasnt been in the water for a long time & is badly opened up.
On big knackered seams we sometimes used oakum which smells wonderful.
Also Oakum tastes dreadful when some horrible person puts it in a roll up!

 

Thanks Keith, that confirms what I've read, the new seams are all pretty regular and the ones done so far have all required the full 8 strands, twisted up as you describe.. Will certainly adjust the number of strands and employ the loop technique you mention when a seam requires it though.. As a newbie I've been visually checking the entire seam length for potential problems before starting anyway so should notice where it might come in useful.

I assume you mean you painted the caulked cotton inside the seams before puttying.. This sounds like a good technique to employ also.. many thanks for the input..

 

Gonzo.. My boat is currently on the Lincolnshire Coast