Cascamite Vs Cascaphen

And very nice she looks too
Nick
I hate to say it but I am fiercely anti plastic when it comes to my Deb's and before you think I'm just some wierd traditionalist ( which I'm not ) I'll explain why
When I bought her it seemed like she was entirely intact and just needed a paint job , but trying to be thorough I decided to check her over completely . What I found was loads of repair work done using plastic and glass but where the work had been done it hadn't always taken properly to the wood , so water got behind the plastic and was held in place up against the wood . So when the water found a screw hole it got through the surface layer of ply and spread along the grain effectively rotting the wood from inside out .
Now I do like the idea of sheathing the deck in another layer of ply but unless someone can convince me otherwise , plastic is going nowhere near my baby again . Without the plastic the wood could easily have dried out , so it was the plastic that did the damage as far as I'm concerned
Oh , and yes , it is the bulkhead between anchor chain locker and main cabin . I'll be uploading all the pics to my blog eventually but if it'll help I can send the password to my photobucket account and you can see more pics
Let me know if interested
 
Sorry about your experiences with "plastic", but you seem to be talking about polyester and (probably) CSM. In that case I agree. However I have owned a plywood boat for nearly 30 years and have used epoxy for repairs, including making good damage to cascover sheathing for all that time. Nothing would get me back to older style adhesives for repairs needing high structural strength such as your repair. You just need to understand its properties. Needs dry wood, good working conditions, particularly cure temperatures and low humidity and does not like UV or high ambient temperatures so needs a covering coating if used in exposed situations. My only reservation would be about sheathing large flat areas underwater where I think vacuum bagging is essential to ensure a complete bond. Sheathing decks is less critical using woven glass cloth (which is what I think Nick is suggesting) as small voids can be tolerated. However, just epoxy coating and finishing with a conventional deck paint is adequate if the extra strength of sheathing is not required. By the way, I am also a fan of Balcotan and would use this in preference to epoxy for interior use where it is not structural as it is easier and cheaper to use.
 
The stuff I took off was woven mat hence my concern but when you say 'epoxy coating' do you mean something like garage floor paint ? That's the only stuff I can find
If epoxy is definately going to stick to wood properly I may be convinced but glass is just asking for trouble as far as I'm concerned
 
Not the same thing at all!! The main manufacturer is WEST, others are SP, Blu Gee, Mase, International. If you have not used it before suggest you go on this site www.wessex-resins.com and click on West. This will give you a whole load of information on the product, how to use it and where to buy it.

Epoxies are extensively used in "modern" wooden boatbuilding including Ply for bonding, coating and structural applications. I have made ply dinghies with no fastenings, only epoxy and they have survived 20 years out in the open.

What you have seen is polyester resin which is not intended to be either an adhesive, or structural. It is just used (very effectively) to hold together glass in a moulded form. It does not soak into wood, just sits on the top, so when it is used, for example for bonding in bulkheads to a GRP hull the joint is mechanical rather than chemical as with an adhesive.

Possible downside of using epoxy for the purist is that it is so good as a gap filler - with the right additives it can be stronger than wood - there is a temptation to "bodge". However, in my experience there are times when what a purist would call a bodge is the only practical and economical solution. A good example is where water had got into a deck beam and bulkhead through a failed glue joint (probably cascamite) and caused local rot. Cut away the rotten deck ply,dug out the rot in the core of the bulkhead and the deck beam, judged that the remaining wood was sound, poured in neat epoxy which encapsulated the remaining wood fibres, filled the remaining hole with thickened epoxy and laminated a new section of ply into the deck. That section is now inert and sealed so no more water can get in.

Other areas in a ply boat that are vulnerable are deck edges, particularly if a rubbing strake has been screwed down with a bedding compund. Water gets in and delaminates the ply - guess that is probably the cause of your damage. I removed all my rubbing strakes and toe rails (helped by damage from the 1987 storm!), made good the delaminated edges with epoxy and a mixture of veneer and woven glass cloth as appropriate and then glued (with epoxy) a one piece rubbing strake covering the deck edge and providing a toe rail. Been there ever since and as sound as the day I repaired it. Nobody would know it was not original, except that it is much better engineered.

Life as a wooden boat slave will change forever when you get into epoxy!

Keep up the good work. Old ply boats need good owners and repay them well for their care.
 
<<If epoxy is definately going to stick to wood properly I may be convinced but glass is just asking for trouble as far as I'm concerned>>

Epoxy to dry wood will give a joint stronger than the wood itself - i.e the wood will split before the epoxy lets go. But the wood must be really dry - makers quote a maximum moisture content of 16%. Most of us find it works well enough on old timber that has dried out enough to feel dry.

And you are quite right about 'glass fibre' on timber. Putting Polyester resin reinfoced glaass fibre mat on a boat is about the worst thing you can do to it. Polyester resin does not stick to wood and rapidly detaches. Water gets drawn into the void by capillary action, and stays there creating ideal conditions for rot.

On Plywood it seems even worse, and a GRP polyester resin 'sheath' will kill a sound hull in about 3 seasons.

I once bought a plywood Bell Seamew. The seams had been leaking because the cascamite had failed, and the previous owner spent the winter 'glassfibreing the hull' to make it watertight. He then bolted varius bits back through the GRP shell. I left it a few months, then stripped the GRP off. Dead easy - it took about 20 minutes, as the GRP just lifted off the ply, which was soaking wet - everywhere! There were just a few points where it was still adhering after 6 months!

The boatyard boss threatened to charge me double, because I had almost ended up with 2 hulls - One ply, one GRP!

Properly applied epoxy would never ' let go' like that.
 
Another point worth remembering is that good quality marine plys are often manufactured using epoxy type glues - so you may well already be using epoxy in your boat without reaslising it.

Epoxy for stressed joints, Balcotan for everything else - nothing else comes near it.
 
As you probably guessed by my silence , I have been chasing up some of the contact information given and have now had a long chat with a very helpful gent at West Systems . As a result of which I should be getting some very helpful information straight from the horses mouth ( figure of speach ) and it looks very much like I shall be following the advice given here
Never thought I would say it but yes , it looks like I'm going to cover her with epoxy /forums/images/graemlins/blush.gif
Thanks everyone for the advice and the links , totally changed my way of thinking , just hope I can get it all done in time for the launch now
 
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