Thread: Repairing cabin wood rot

Don't even think it,

CUT OUT the ROT until you have clean solid timber then put in a new piece of ply, glue with epoxy glue, and seal & paint.

If you do as you suggest then you will have the EPOXY PUTTY , fall out when you least expect it.

Do the Job properly first time and you won't have to re-do it in 3 months time.

Jeff

what makes you think the epoxy will fall out? It's supposed to dry rock hard.

The "wood hardener" products now available fall into three basic categories, acrylic polyurethane (such as Earl's), solvent based polyurethanes and thermoset plastics, which typically are polyester or epoxy based.

The single part acrylic and solvent based polyurethanes are great for furniture makers and restorers, needing to fix a non-critical part. They aren't especially flexible, particularly the solvent based stuff, nor especially durable, but their role is just to offer a moderately solid base for additional filler, in which role they do okay, if the piece remains static (doesn't move or flex). The polyesters and epoxies are more flexible and can tolerate more movement. The epoxies are the toughest and will actaully return the wood's strength (with fillers). The polyesters will add some stiffness, but in a humid environment (like that on a boat) they tend to lose grip with time on wood, though is great on other materials.

For your cosmetic repair, I'd skip the wood hardener all together and just move to an epoxy (Bote Coat?). The wood hardener an unnecessary step and will have marginal results on a boat. Don't get me wrong the wood hardener can work, but it will not be as durable a reapir as some of the other choices.

In other words, if you're going to use epoxy anyway, why bother with the other stuff, when epoxy is the best choice of the bunch. Wet out the well cleaned area with neat epoxy. When this has gone slightly tacky apply a thickened mixture, then sand and paint when cured.

Cheers for that. The Epoxy I linked to in my original post is aimed at outdoors use for the concrete industry. Can you see any issue with using it instead of a tin with "marine epoxy" on it which no doubt costs 10x the amount?

Yes, I can offer some things to consider about epoxy formulations. You can make epoxy have the physical properties you need. For a concrete application you'll kiss off some modulus of elongation in favor of a really hard mix, that isn't going to be asked to move once installed. This would be a typical concrete formulation. On wood, you need a higher modulus of elongation, so it can cope with movement and stress without breaking. It's sort of like using bathroom caulk. You have several different formulations to choose from, as a result some work a lot better then others.

Will you be okay, probably, considering the piece you're working with, but then what to do with the rest of the tin of goo. Bote Coat is fairly reasonably priced, I understand and it's something you'll need again, so could be considered investment in the boat.

Marine epoxy is actually cheaper, if the cost of the Ramset cement epoxy tubes in Bunnies is any indication. (Botecote - $35 for 750ml, $62 for 1.5 liters, $97 for 3 liters. Considering it doesn't go off, its handy to have a litre or so around.)

Product Information Pages

most important thing as VK4 says is to completely excise the rot.
Any remaining organisms will just continue to turn your wood into powder
under your repair. A distant second-best is removing 'most' of it & treating
the remainder with one of several fungicides, eg CCA, CCB or Glycol.
While I haven't had any problems with CCB or Glycol, the mere fact of their
residual presence logically means a less effective bond for your epoxy.
cheers
ALan j

I was under the impression that Earls Wood Hardener was some sort of fungicide treatment that killed the fungus infecting the wood but also had some sort of resin which set hard to give some strength back to the wood. Is this not the case?

There are fungicide agents in Earl's Wood Hardener, but nothing on earth will make rotten wood whole again. What it does is firm up some of the fluffy wood, but once mass is removed (eaten and digested by the beasties) it can't be returned without a similar density substitute being installed. Even epoxy requires some reinforcements (fillers and/or fabrics) to replace what has been eaten. There are two trains of thought in this regard, the traditional one is to cut back to known, good wood and install some sort of Dutchman type repair (replace the wood with wood). The second approach is to use plastics instead of wood as the substitute. Plastic wood filler doesn't do much in regard to strength. It's just a cosmetic surfacing agent. It also requires the area under it, be stable and clean or it'll pop out, which it can also do from vibration. If epoxy is used, it too is a surfacing agent (without fabrics), but the prep stabilizes the wood and the bond is tremendously strong.

Ok, so if I didn't go down the Dutchman path and went the lazy man path I could kill the fungus using Earls Wood Hardener then use BoteCote putty to push into the cavities to return the wood to having shape and form. Then sand and paint over. It's not the best way but it should do the trick shouldn't it?

Bote Cote is an epoxy and to make it sandable you add in the suitable filler which in turn to my understanding doesnt have a lot of strength. So what you could do is add the strong filler and buildup to just shy of the surface then add in the sandable filler ( in a new mix ) to finish to surface. Neat epoxy is a b&^% to sand.

If you use the Earl's wood hardener for fungicide/biocide effects, you've then got to prep the surface of the Earl's stuff to take an epoxy bond - which is not at all dissimilar to trying to sand PVA glue, and I expect the chances of achieving a good bond to the Earl's are going to be pretty close to none whatsoever.

Use some borax solution as a fungicide, let it dry, mix up some epoxy, use some unthickened to prime, then thicken the remainder up with sawdust to a nice thick mix and recreate the missing bit of timber. You can choose thickening agents for the epoxy to suit your strength needs, all the way from talc (very easy to sand) to aluminium or stainless steel powder...which you really won't want to sand.

Epoxy will stick to Earl's, but it does need to be properly prepped (toothed). I still think Earl's is an extra step you don't need. If you remove the rot, the epoxy wet out and subsequent filling will lock it down, all the while using only one product and no additional prep. If you use Earl's, you still need to remove the rot, but then you have to prep the surface for epoxy (or any other filler). Earl's is fine if you're interested in repairing the fascia board on the front of your house, but really doesn't offer much in the marine environment.

You can use fungicides, but really this isn't the best approach either. Removal of the suspected areas, is the logical route and this doesn't need any poison. Epoxy will rob any beasties of air and moisture, if applied properly and this will kill them off anyway.

The advise as I see it from all contributors , my self included,is to CUT OUT ALL THE ROT , then do the repair with epoxy Resin of your choice.

Using a fungicide, and leaving suspect timber in place is a no win situation, as the chemical may not kill all the rot spores.

The choice is yours do it once and cut out all the rot , or chance it with a fungicide, and have the possibility of having a bigger repair to do in the future ..


My 2 cents worth.

Jeff
vk4