Polyurea for filler

[TyBoo]

I replaced the windlass on my boat and found the seal around the hole through the foredeck was compromised and the balsa core was saturated for a few inches all around it. I gouged out all the rotten wood and dried it with a heater blowing in the anchor locker for a week.

I started the filling process with Marine-tex epoxy but that was a messy pain. I sealed up around the big hole and the void on three sides of it and planned to fill the rest with Git-Rot liquid epoxy.

But then I got the idea from a carpenter to try some stuff used primarily for filling joints in concrete. Polyurea is a two part elastomer that cures to a hard rubbery solid form in just a few minutes. It is very dense, impervious to almost everything, and hard yet flexible. It cures in whatever thickness and shape is needed. The stuff I used came in two tubes that fit into a double caulk gun tool and feed into a mixing nozzle. It comes out of the nozzle in a consistency like Mrs. Butterworth's syrup and cures to a very hard rubber like substance. It isn't real cheap - about fifty bucks per pair of tubes.

I plugged up the inside of the two bolts holes for the windlass and injected the stuff through the top of one hole until it filled the void and forced out through the other hole with enough pressure to push my thumb away. I was quite happy with the result and have a lot of confidence in the fix. I wish I would have used it to fill the entire area.

My question is - why haven't I heard of this stuff before? Its only drawback as far as I can see is that it does not bond well to other materials, but it strongly bonds with itself to form a very tough solid piece of material that is resistant to crushing and doesn't weigh too much. Since the area inside the foredeck is sandwiched by the force of the windlass studs and my big backing plate clamping it I see no reason why it is not the perfect fit in there. So why couldn't this be used to fill a bulkhead or transom if all the wood was removed? It seems it would be a great fix for a transom if the cap was taken off and all the wet wood was gouged out through the top.

There is one mention of it on C-Brats being used as a coating in a shower (I think) but nobody seems to have used it as a core-replacing filler. It seems like a great material to me. What am I missing here?

[thataway]

Mike,
I think the answer is that it does not adhere well to other materials. The nice thing about epoxy, is that is is an excellent adhesive, both to cured fiberglass and wood, even wet wood to some degree. My concern is that some water could get under the windlass, or other fitting, and then wick around to the balsa wood core. I also would prefer something much "harder, since the deck takes compression when putting in a fitting, such as a windlass..

I would not have chosen either of the epoxy compounds you choose. The Marine Tex, does not allow as good coating of the wood, as a "neat" unfilled epoxy does, and the get rot it way too thin.

There are many types of polyurea (Poly Urethane) compounds. Here is a good read on the history and chemistry of the polyureas http://www.polyurea.com/cnt/docs/PUAHistChemForm2008.pdf

There are single part and two part polyurethane foams, both of which I have used for insulation in boat building, but not in this type of application.

The poly urethanes as a class run form the single or two part paints, to the bed liners, and many other products.

[AstoriaDave]

Is this the stuff, Tyboo? http://www.pcepoxy.com/our-products/joint-and-crack-filler/pc-xtreme.php

It remains flexible and is rated to handle some expansion and contraction. In your application, with the area squeezed between plates I can't see any problems. A dense foam or glass/fumed silica filled epoxy would be more dimensionally stable, and rigid, FWIW.

In contrast, I would not use one of the so called one part polyurethane construction insulation products because they will eventually degrade if subjected to constant immersion. But this is a polyurea, new beans to me, and if it is OK for filling driveway cracks, it must have terrific stability if exposed to water.

I think you are off on a grand experiment.

[AstoriaDave]

Bob,

Bottom of page five in that pdf file they detail how polyurethanes differ chemically from polyureas. Both are two component systems and both use an isocyanate for one component. In lieu of a polyol, polyureas use a polyamine as the second component. This is at the root of the differences between them. Here is the pdf link again: http://www.polyurea.com/cnt/docs/PUAHistChemForm2008.pdf

[TyBoo]

Thanks gentlemen.

Bob, I figured it was too easy to be good.

Dave, this is the stuff I used. It looks to be quite similar to your link.

Qwikjoint 200

We pumped out a tube of the stuff in a paper bucket at work and the next day I smashed a 1" thick slab between steel plates in a press. Oh, some of it smooshed out the sides alright but the part that didn't stayed together under 50 tons, albeit considerably thinner. So no worries about the 5/16" windlass fasteners crushing it.

[AstoriaDave]

Mike, for future reference, you can get epoxy in a two part delivery system similar to a caulking gun from System Three. Mixes in the exit tube. Expensive on a per pound basis, but no waste and really speeds up laying mixed resin. Pretty much have to use up the whole unit in one job. Don't know if S3 has any filled epoxy combos set up that way.

[Robert H. Wilkinson]

Dave, most mixing systems can be reused if you leave the tube in place after using and let it harden - this keeps the unused product sealed. Extra mixing tubes can be purchased, although they aren't cheap. When you want to use it again - remove the tube full of hardened product and replace it with a new tube. The first time you use a new kit squeeze a bit of product out to equalize the tubes of product then install the mixing tube.
We have used a number of different adhesives at my work, Norton - Lord - and currently 3M. The biggest pita for the home handyman is that the "caulking" guns used are usually proprietary to 1 company and very expensive.

Regards, Rob

[thataway]

Although I have not used the two part epoxy in large caulking tube contains/or polyureas Most of these type products can be kept in the freezer after being opened, and thus used again on a short time of rewarming.

Although there are multiple epoxies in dual compartment caulk gun containers,

West Systesm NEW Six10® Thickened Epoxy Adhesive - A 2-part epoxy in a tube that delivers point-and-shoot convenience
Measuring and working with epoxy resin and hardener just got easier. WEST SYSTEM® now offers the permanent, waterproof, gap-filling and gluing performance of their two-part epoxies in a convenient point-and-shoot package. This new Six10 Thickened Epoxy Adhesive meters the proper ratio of epoxy resin and hardener from a multi-chambered tube that fits in any standard caulking gun. The pre-thickened components travel through a static mixer where they are fully blended before being dispensed in a smooth, workable bead.

This gap-filling structural epoxy bonds tenaciously to wood, metals, fiberglass and concrete. The mixture will not run or sag. Unlike other ready-to-dispense adhesives such as methyl methacrylates and polyurethane glues, Six10's physical properties are ideal for stitch and glue boat construction, fiberglass laminate repair and general marine bonding. Six10's sheer, thinning properties make it "thinner" as it's worked. It can be easily tooled into a fillet or used to wet out light to moderate reinforcing fabrics, like fiberglass."

System 3 has a similar product as Dave points out.