Bedding compounds

[gaffer61]

Hi.

I am building a 33ft gaff cutter, carvel planked larch on sawn oak frames. I am just about to bolt the centre line timbers together but am uncertain what to use in the way of a bedding compound, I have had conflicting advice on this matter. Does any one have any thoughts?

 

[rjp]

For what it's worth a previous poster (youngwrinkley) on this forum recommended Plumber's Mate as a suitable bedding compound for fittings and even for bedding a keel. A search on his or my username will reveal the thread (underwater sealant).

John

 

[Mirelle]

Hats off to you for such a project!

Some thoughts:

No conventional bedding compound on the planet is going to stay soft for the life of the boat.

A polyurethane type may introduce other problems - should it have a void it can never be sorted, it in effect acts as a glue, and the time required to get the joint together may be too short to bolt up properly.

My suggestion (which may seem ludicrously old fashioned) is to first paint the faying surfaces with, ideally, red lead paint, allow that to dry, then lute them well with white lead paste. The reason for painting the faying surfaces first is to stop the binder in the luting compound leaching off into the end grain of the wood.

I would expect the white lead paste to stay flexible (and poisonous to critters!) for many years, on this basis.

Stopwaters still needed, of course.

 

[gaffer61]

Thanks for your responses. I quite like the idea of plumbers mate but would be interested if any one has experience of using it below the waterline in a marine environment? I also like the idea of white lead paste Traditional, Poisonous to nasties, Straight forward to apply. and as you say its the stop waters that are going to prevent the ingress of water.

 

[Casey]

For what it is worth I have used polysulphide under the tingle I put over the drain plug. It comes off fairly easily and remains flexible but only stays there for two years at the most. I think that it is easier to use than Sikaflex and not so expensive.

It is similar stuff that builders use when sealing windows and door frames although it comes in different qualities.

 

[kestrel1891]

I used Black Pudding from Traditional Boat Supplies to bed all the timbers on Kestrel's centreline.
It's lovely tarry stuff in a liquid form that you thicken to taste using Portland Cement. Sounds unlikely, but it really does work. Just put in about half as much cement again as you first think likely or it tends to run.
It supposedly never goes hard, though I haven't taken anything apart to prove it.

 

[Porthandbuoy]

I have a boat repair book dating from the 1930s which recommends a mixture of red, or white lead putty, and paint as a bedding compound. I've used it as a sealant under deck fittings and when fitting seacocks; seems pretty good. I added just enough pink primer to the putty to acheive a consistency that let me stipple it with a stiff paintbrush.

 

[Lakesailor]

I used Plumber's Mate to seal a wooden plate I made to cover a 3" hole left in my grp deck after removing a chain pipe.
I removed it after 2 years as it was letting in water and after undoing the bolts the plate came away easily. There was no obvious bonding between the two surfaces, but a lot of damp. So, in my experience, it was not successful.

 

[Mirelle]

For what its worth, I took a fitting off some years ago and the original white lead bedding was still soft after 47 years.

 

[gaffer61]

How messy did you find the black pudding mix when you did your center line timbers on Kestrel? How easy is it to clean up and did it keep squeezing out after you tightened up the bolts. It sounds like good stuff but I am concerned about it being a constant mess inside the boat, or am I worrying needlessly.

Have you finished Kestrel and what sort of boat is she?

 

[Wayward_Son]

3m 5200 for bedding through hulls, windlasses, portholes, etc. Phenomenal holding power, sealing capabilities, and longevity. Works above or below the waterline and the components being bedded will have to be replaced before (if ever) the 5200 breaks down.

 

[pelorus32]

The big centre line timbers on Zuline (32 foot Lyle Hess) some of which are up to 26 feet long by 12 inches wide are bedded in Hydroseal.

These timbers are Tasmanian Blue Gum and were kept in a creek until needed and worked and kept wet until launching to limit movement. Hydroseal is a plumbers' flexible roofing mastic and comes in "brushable" and "trowlable" consistencies.

12 months after launching the hydroseal is still the consistency of somebody's discarded bubble gum. These timbers move a lot at first and whatever goes in there needs to be flexible.

The other good thing about Hydroseal is that you can load it into a grease gun and drill a hole to send it in alongside keel bolts etc if you feel the need at some later point.

Building a boat like yours (and mine) is a life changing experience. I hope it gives you a huge amount of pleasure.

Regards

Mike