Roofing material for bedding?

Cosmoline is that waxy stuff they used to keep artillery and naval guns greased and clean. The mixture is a non-cross linked wax and petroleum formulation. Little more then wax in suspension within oil. On metals it can keep a clean, raw metal piece "preserved" so to speak, but on wood it will contaminate the surface, making any additional treatment (paint, glue, epoxy, etc.) very difficult. I haven't seen this stuff in quite a while. Every so often I'll open a piece of equipment and see the remains of cosmoline packed into corners. It was commonly used inside machinery to keep parts from rusting during storage or shipment. Once the machine started up, heat and friction mashed it into the voids within the machine, where it would dry out into a cakey, hard wax like goo.

 

On a joint, mostly on a timber keel, it is the fastening which is important, the bedding is just an addition, not the answer.
If the wood is well treated before the very efficient and closed spaced fastening, the bedding I will recommend is a neoprene type like the Dewitt's.
But the bedding can be also a thick coat of zinc based oil paint, or if you fastened in bronze, a thick coat of lead putty, providing the wood is already saturated with oil, if not the oil in the putty goes to the wood and the bedding turn to just a lead powder.
You can use roofing tar but only underwater. You can use also a mix of coal tar, it keep a good elongation rate over the time, but difficult to paint over.
The fastening and preparation of the wood, and quality of the joint is the real priority, what you put in the middle, is what you feel comfortable, with your own experience.
As I said on a classical construction I recommend the Dewitt's.

But that's me.

Daniel

 

Dolfinite is also a good choice for well fitting, pre-oiled timbers. These are pure, traditional bedding compounds with no adhesive qualities to them.

 

Yes, absolutly, and is now easy to find on the market, after some time of disparition.
Good stuff.
Daniel

 

is pressure treated wood any good in boats?

 

Yes, and no, depends on application, but generally no, though some working craft can use the stuff.

 

There has been some large replicas wood ships built using custom glue-laminated timbers, that were pressure treated. It worked out well, and I see no issue with it for the boat, except the following: to be effective the wood parts have to be treated AFTER they are cut to shape to ensure good penetration of all surfaces. So you would form up and fit the timbers, dead wood, etc. dismantle it and have it all sent to a wood treatment plant, and than reassemble it all.

Two other issues that should be considered; The pressure treating compounds are basically toxic pesticides. They kill any wood eating organisms that come in contact with it, do you really want your hull made with toxic compounds? Unlike epoxy or other adhesives, it must stay actively toxic to be effective. You should wear gloves and respirators every time to work with it, you do not want these compounds penetrating your lungs or skin. You will breath it into your lungs every time you cut, plane or sand it. The other is the current compounds are very corrosive to ferrous metals, and will even penetrate galvanization, so much so that the building industry has issued warnings that you must use heavy galvanized hangers and fasteners (not electro-plated), or all stainless for anywhere it comes in contact with the wood. I have seen a galvanized hangar corrode through in only a year with the current pressure treated wood.

So if these issues are addressed, it would be a viable option.

 

Most treated lumber also comes with a very high moisture content, making fits difficult and joint gaps considerable afterward. On substantial timbers, you may have to wait 6 months before they're down to reasonable moisture content levels again.

The latest crop of CA treatments is just a wait and see issue, before it's banned from use, much like CCA was. If you are of child bearing age and interested in not having three headed babies, then avoid the PT treated yacht.

 

"three headed babies", reminds me of one i once saw out on the road, not only three heads, but no arms and only one leg, he was trying to hitch a ride.

I pulled over and said " hello, hello, hello, you look harmless, hop in".....

 

. . . my ex-wife again . . .

 

Some of the Boats I took apart for repair (1948 to 59) had a lot of Tar down between the Keel and the Devil.
Some keels were soaked with it. As if they heated the keel and the Tar and brushed it on till it wouldn't take any more.
But....that stuff separates from the wood if the wood is soaked with water.

Those boats were pretty old. Some of them from the 20's and had been in Puget sound working all their lives.
I never found any Rot down there in the bottoms though. The Rot was always up above the "continuously wet" parts.
So that Old sort of Roofing tar, without any additives might just work for as long as you'll last as the boat owner.

The Poly stuff wont work at all. One of the Roofing companies had to replace my Roof over those new Shingles that had Fiberglass stuff instead of tar.