bedding compound

[bart]

I'm putting in the false bottom on my Swampscott dory and want to bed it in. I priced Dolphinite but it would take $150+ to cover the 9 sq ft of bottom. Lifetime caulk would be even more expensive. I know they used to use roofing tar. What do you think?

[Joe ( Cold Spring on Hudson )]

http://images.orgill.com/200x200/6142806.jpg

Same thing ;)

[Bob Smalser]

Henry's Roofing Cement at Home Depot comes in caulk tubes and gallon pails. I use the solvent-based cement for your purpose in my solid-wood work boats. Paints over OK with oil paints and remains soft. Will bleed in the sun.

9SF might cost you a whole 4 dollars.

On plywood boats I use an industrial poly sealant similar to 5200 but not as adhesive. Apply it between two primed and painted surfaces and its adhesive properties are no longer an issue, although it's a lot tougher to remove than tar. Lasts forever and doesn't bleed like the tar does.

More expensive than the tar....9SF might cost you 8 dollars.

[seayou77]

My ballast is bedded in roof tar. Added a layer of cheesecloth to prevent it from squishing out and leaving a dry spot. That stuff that is designed as mold inhibitor for paint additive, might be good to stir in as it is nasty stuff!

[landlocked sailor]

Dolphinite has a thinner consistency than plumber's putty, so it has much different working properties. I think plumber's putty works great for bedding bits of hardware but I sure wouldn't want to try and spread it over a broad layer. Roofing stuff is probably what you want for your application. Rick

[Joe ( Cold Spring on Hudson )]

Originally posted by landlocked sailor:
Dolphinite has a thinner consistency than plumber's putty, so it has much different working properties. I think plumber's putty works great for bedding bits of hardware but I sure wouldn't want to try and spread it over a broad layer. Roofing stuff is probably what you want for your application. RickI used plumber's putty to bed the CB cap on my Salisbury skiff. It worked JUST like Dolphinite even better because of its thicker putty consistency. Also if you work it and kneed it before applying it thins up substantially. I think its a perfect solution for this application. Also you I don't think you can re-do the roofing stuff. You can always go back and re work the putty it's not permanent which is a good thing for a bedding compound to be.

[ 03-11-2005, 06:23 PM: Message edited by: Joe ( Cold Spring on Hudson ) ]

[Tristan]

A friend built a 65 foot tandem-CB dory schooner about 28 years ago and sheathed the bottom with copper. Bedded the copper in roofing tar. He had his boat in salt water for 26 years, never hauled out, just occasionally scraped her off while she was in the water. Hauled out a couple years ago and laid up the schooner beside his barn. Where the flat bottom rests on timbers the roofing tar squeezed out from under the copper a little. It's still soft, pliable, and still firmly "cementing" the copper sheeting onto the bottom of his schooner.

[dunbarpm]

around here it is referred to as plastic roofing cement, sold by the gallon bucket (and, recently in caulk gun tubes). Doubt there are many workboats here on the Eshore that don't have use it somewhere as a bedding compound. good stuff - just stand near the bucket and it gets on your pants and a sleeve. Used it for many years on several tough old boats, as well as my Meadowlark.

[dunbarpm]

of course our town 'corker' wouldn't cork no boat that got tar in er.

[Leon m]

Just curious, what happens to dolphinite/plumers putty/roofing tar when it gets really hot out?does the stuff get runny? Somebody told me to use it for bedding rubrails once.I could just imagine it getting hot and running down the sides of my boat,so I used 5200 instead.

[bart]

I just found a place where I could get Dolphinite for $64 a gallon instead of $34 a quart.
The common theme seems to be that roof tar will work fine but can run. If it is running it is running out of where I want it to be and I would suppose be leaving a gap.
Has anyone out there used Dolphinite? The spec sheet said it was silicon, mica, and mineral spirits. I think I still need more information and I'm sure there are lots of you out there that will run into this situation sooner or later. Thanks for the help, keep those comments coming.

[carioca1232001]

bart wrote:


The common theme seems to be that roof tar will work fine but can run. If it is running it is running out of where I want it to be and I would suppose be leaving a gap.
We have 3-grades of roofing-tar in Brazil and I hope the following account helps.

I was in doubt of which one to use on some of the seams around my waterline, but on reading the specs, noticed that one also doubled as a caulking material for boats.

On opening the gallon-can, I noticed that it was dull(matte) and pretty solid, unlike the other two-grades that are shiny and in liquid-form. It said on the can that heat wuld be needed to make the stuff flow, so I complied.

It changed colour to a shiny peanut-butter consistency and I had to apply it quick, before it became matte again and set. Added some cement to it while it was flowy and it has not run, despite our "hot as blazes" summer season.

[Tristan]

Originally posted by Leon m:
Just curious, what happens to dolphinite/plumers putty/roofing tar when it gets really hot out?does the stuff get runny? I used Dolphinite to bed the caprails and rub rails of a Bahama dinghy that I had for five years in the hot Florida sun. IT DIDN'T RUN. I also used it to bed rails of another boat down here. It has not run. Dolphinite is only for use ABOVE the waterline as I recall. Below the waterline, in a boat kept in the water, roofing tar seems to work fine.

[Leon m]

Originally posted by Tristan:
I used Dolphinite to bed the caprails and rub rails of a Bahama dinghy that I had for five years in the hot Florida sun. IT DIDN'T RUN. .Good to know...Thanks !

[Canoeyawl]

I have used a nice thick coat of soft copper bottom paint as bedding for large areas like this with good success. Using a roller to apply it, a fairly uniform thickness can be obtained. This is also an effective worm barrier. With sacrificial planking overlays, (especially plywood) there is the “pillowing” effect to beware of. When all the fasteners are tightened the thing may look like a quilt if the compound is to thick or “heavy”

[bart]

Good thought. A quilt is not the effect I wanted. I'm using black locust in the false bottom and it is about as rigid and tough as any wood I've ever used so quilting may not be a problem.

[ssor]

Bart, Black locust is common here in Maryland but how do you come by it in Washington? You're putting this on the outside of the boat on the bottom? And you don't expect to ever remove it? If yes to the last two questions , then use plastic roof cement. warm it in hot water and it is much easier to spread, use a notched tile setters trowel, at least 1/4x1/4 notches. Wear clothes that you don't want to keep, ( that stuff jumps outta the can and sticks to ya like bad news.) After a couple of weeks it will dry enough to paint. If you are concerned about full coverage thin a small portion with paint thiner and prime the surfaces. I repair houses for a living and roof cement and fiberglass cloth makes as durable a patch as you can find for roofs, rain gutters, and chimney flashing, but it isn't pretty.