Son of Bedding Compound

[Tristan]

In a related post BART asked about bedding compound. Dolfinite was mentioned as a possibility but expensive. I suggested roofing tar and commented that Dolfinite was not recommended below the waterline. After the fact I got out my only can of Dolfinite and it can definitely be used below the waterline according to the mfgrs. recommends (as it is recommended for cross planking bedding). Don't know what I confused it with to think it can't be used below waterline. HOWEVER, my can of Dolfinite (about 2 1/2 yrs old) had a 1/2 inch thick, leathery, layer across the top. Beneath this was the soft, normal appearing Dolfinite. I still would hesitate to use it, as it does harden into a thick, dry, crumbly layer, probably as the oil leaches out into the wood. I was reminded of this yesterday when I pried the cover off the centerboard of my gunning dory. It had been bedded in Dolfinite.

[ssor]

seems like all of the bedding compounds harden after a while. some harden much more quickly than others. Painters putty is intended to harden and can be sanded after just a few days, plumbers putty will stay soft under a sink faucet for a couple of years, "Dap 31" glazing compound stays soft but "skins" over in about three days, but will harden in the can in six months. I have removed bath tub drains after thiry years of service and the putty was very firm but yielded to a scrapeing with a stick. All too often tightening the item being bedded squeeses most if not all of the bedding out, and a small countersink at each hole helps to keep the bedding where it is needed.

[pcford]

? !!
If you are looking for a bedding compound why not start by using one that says bedding compound on the can.

It is true that Dolphinite's mineral spirits vehicle will leech out if some care is not taken. However, this can be controlled to a large extent by sealing the surfaces (aka faying surfaces) to be joined.

[ssor]

Years ago, no matter what sort of a seam-sealing or bedding operation you had in mind, you picked up a putty knife and a can of oil-based bedding compound. Oil-based compounds rarely failed due to problems caused by incompatibility with other boatbuilding materials; they always failed within a few years, however, due to drying, cracking, and lack of adhesion. Over the past decade, oil-based bedding compounds have all but disappeared from the shelves of marine hard ware stores and ship chandleries. They have been supplanted by synthetic rubber adhesive sealants. The synthetic rubber compounds typically last for ten to twenty years or more. Nevertheless, a tube of adhesive sealant must be chosen much more carefully than a can of bedding compound; the various polymers exhibit vastly different properties, and frequently fail due to incompatibility with other materials.
The above is an excerpt from an article at the "Bosunsupplies.com" web site

[paul oman]

What about using thickened epoxy as a bedding compound below the waterline? You can get 'regular' or flexible thickened epoxies for the task.

I have to admit, I'm in the epoxy industry, but rarely hear of specialty epoxies being used for bedding applications. Anyone know why, or is it just lack of knowledge????

paul oman
progressive epoxy polymers

[ErikH]

Bedding compounds need to be watertight, often removable, frequently slightly flexible, and "squishy". Epoxy normally only suits #1. You don't 'bed' something in epoxy, you attach it with epoxy.

[ssor]

I shall make up some test pieces with a variety of bedding compounds and caulks and check back in three or four years. :D

[Undaunted]

I am facing replacing the bedding compound under my white oak sacrificial keel (12' lapstrake dory) and have been looking to see if anyone has a suggestion for a synthetic compound that might last longer than Dolfinite, but to no avail, anybody have any ideas?

Must be waterproof below the water line and replacable in maybe 10 years...

SWG

[The Bigfella]

I'm facing a similar issue with the new hatch on Grantala - and there doesn't seem to be any comparable product to Dolphinite out here.

Given that I've got a glass panel under the front section of the hatch, I need the hatch to be removeable in case the glass ever breaks (unlikely given it is 12mm thick toughened glass). My plan is to seal the bottom surface of the hatch with epoxy and bolt it to the teak deck from underneath (SS lag bolts into epoxy plugs in the hatch) and to use a thin smear of an oil-based mastic as the bedding compound.

If I were to bed it in Sikaflex, its a bit like using epoxy unless I set it in quite a thick bed of Sika so that I could "hot wire" it for removal.

Any thoughts?

[pipefitter]

3M 4200. Not as permanent as 5200.

I was told a long time ago to flute the sacrificial keel on the doped side to keep more compund within the layer. I fluted the false keel on my Simmons to hold more epoxy instead of it all squeezing out. It is also supposed to help relieve the piece slightly from movement against the fasteners.