DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

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alan watson
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DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by alan watson »

I am attempting a first restoration of a Magnum 5. At first sight it is basically sound BUT there appears to be some rot travelling along the internal layer (s) of ply.

Obviously the best solution is to cut out and replace all areas in doubt but this is beyond my skill.

However I can
A) Cut scrape and drill out almost all of the rotten ply
B) I can then drill along the rot line and either
1) Insert a mixture of epoxy and micro balloons to stabilise and strengthen or
2) Use commercially available wood hardeners and ( for want of a better word) rot killers eg from Ronsan
C) I then plan to fill any voids with foam which I can then sand down to provide a strong base ( on top of the treated timber) on which to epoxy carbon sheets.

Does this sound about right ? or is there a much better way to go ?
Is it worth considering applying the wood hardeners and antibacterial rot killer as Ronsan ?

Any Advice very welcome.

Cheers
ALAN
PS Sorry about the rather silly "mothman" username but its derived from many spendid trips to Carrick Roads near Falmouth when I was known as mad !!
Rupert
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Re: DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by Rupert »

And there was I thinking you had the most appropriate surname in the cvrda...

Yes, wood hardeners work. Pippa's Puffin would have been thrown away without them. I didn't even do any drilling (there was nothing to drill, really). It reminds me a little of fossilizing the wood - it hardens it up, but it certainly becomes pretty lifeless after. I suspect it is one of those things that will last X number of years, and then the whole lot will suddenly just fail, with bits of epoxy (or in the case of some of my boats, windowsill filler) simply falling off, once the wood round the hardened area gives up the ghost. I've not got to that stage after 10 years of using it, though.

I can never remember which one I use. Cuprinol make one, and Ronseal. One tales 6 hours to go off, the other 1/2 an hour. It is the 1/2 hour one I use - life is too short...
Rupert
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Ed
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Re: DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by Ed »

Hi Alan,

yes, wood hardeners do work.....and can be very useful in the right place and time.

I am not sure about using them on a ply hull skin though. Maybe if it is in a low-stress place and not too big, then it will work, but it depends on where it is. If it was around a transom/hull join, where water has collected, but there is no or little stress, then it might be ok, but if it was near a stress point like near the daggerboard or chainplates or internal structures like bouyancy tanks or whatever, then I am not so sure.

I always prefer to remove rotten wood if at all possible, but try and leave as much of (or all) the good wood if I can.

If an outer layer of ply has gone soft, you can simply remove that and replace just that layers with veneer. But a couple of provisos. First is that outer layers are normally better quality and harder and more rot resistant than inner layers, so if the outer layer is soft/rotten, then it is more than likely that the inner layer is too. Second is that once water is in ply, it tends to work its way down the glue-lines so the rot can travel much further inside the wood than you are first aware of.

So, although I would certainly agree that wood hardener can and does work, I would recommend an approach more like this:

1) cut out all the soft wood. dig about and anything that is soft enough for penknife to easily cut away is marked out and then as close to a rectangle patch is marked out. Then get a sharp chisel and cut away the rotten wood one veneer at a time. Try to not go through the bottom layer....but if it is soft, then accept that you will need to replace a section of ply all together.

2) stabilise everything that is left. Wood hardener would do this, but my preference would be for a thin epoxy like eposeal sp300 or a woodseal like UCP, blakes wood seal or Bondamarine G4 Wood hardener....or just a thinned epoxy or thinned G4 but with the correct diluent of course.

3) build up the damage with new veneers. Either making it pretty or not as required. By preference use epoxy.

4) skin the wood afterwards with some glass or carbon cloth and epoxy. Use some heat to get it nice and thin and some peelply to absorb any excess resin and minimise the amount of work cleaning it up afterwards.

All this is well within your capabilities! I remember the new stem you put on Rozzer. That was a way harder job than doing this, even if you have to replace a bit of ply. Promise :-)

We are here to hold your hand and I can come by to take a look.....is the boat in Bristol?

cheers

eib
Ed Bremner
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simonmw
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Re: DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by simonmw »

I hope those who have already posted don't mind me adding a little?

You don't say whether the rot is in the hull or the deck?

Has it rotted from the outside, or just end grain, or- one to be wary of- from the inside out if in the hull?

If it is in the deck, then to my mind it really isn't worth saving a suspect deck. By setting a router to a depth equivalent to the thickness of the ply you can have a deck off in an hour if its convex or flat, only slightly more fiddly if it's concave as some Moth cockpits are- and a new deck on easily in a day to the stage where it's ready for sheathing, paint or varnish as appropriate.

If it's in the hull then I would also possibly consider the above, depending on how sure you are of the condition of the internal structure and whether there is any rot you can't see in bulkheads/stringers etc. It would allow you access to determine the condition of the internal structure and also possibly give you the option of fitting reinforcing doublers to the inside of any suspect/thin areas if this proves appropriate.

If it's just a few bits in isolation and you are reasonably sure there aren't any hidden 'nasties' on the inside, then I agree whole-heartedly with the approach Ed has detailed!

Hope this helps :)
Current custodian of-
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alan watson
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Re: DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by alan watson »

Thank you very much Rupert Ed and Simon for your kind advice,

Encouragement helps and so I have made a start. I have removed almost all paint and all of the obvious rot. which seems to be confined to the stem for about 4 inches top an bottom as it were and I can stabilise with epoxy / hardener. I plan to replace these sections with a stiffener of 400 gm carbon insert into the stem and with microballon / epoxy filler and outer hull layers of 200gm carbon.

Otherwise the hull seems very good, some obvious areas of repair with some exceptionally hard material and glass sheet.

Ideally I'd like to remove a mm of wood all over and then skin with 150 / 200 gm carbon. However I have been told that , without a vacuum bag, wet lay up is heavy because of the excess epoxy and so I'd be better off using glass because it absorbs less epoxy in a wet lay up and so is ultimately lighter ?

But apart from a couple of areas the hull pretty strong. So perhaps all I need to do is just patch holes/ dodgy areas and then sheath with 150 glass.

Or I could patch and fill holes and dodgy area and sheathe the whole hull in 150 glass rather than carbon without removing any ply and pay a weight penalty. Or I could just sheath the curved water line areas and bow and leave the vertical sides which are beautifully filled and smooth. Would that create an line of weakness between the sheathed and unsheathed.

So its a choice between skinning the whole hull in carbon
Or glass
Or patch dodgy areas and skin them with carbon / glass
Or patch and sheath just the water line and below areas.

The hull is a bit heavy ( but the lines are very sweet ) and the reason for wanting to trim off some of the ply and replace with cloth is to loose weight and increase strength.

Again any advice most welcome.
CHEERS
ALAN
alan williams
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Re: DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by alan williams »

Hi Alan
I removed two layers of ply from the bottom panels of a Hornet when the rule were changed to allow thinner panels. I did this with a belt sander successfully but the ply was 6mm. I would not recogmend this method with the very thin ply used on Moths. My Chelsea Morning decks were 1mm modellers ply and the hull 2mm modellers ply skinned with a very thin layer of tissue glass and polyester except in the load bearing areas (floor and wings),where this was doubled up, a very light space frame took the loads. We only expected a hull to last a season and then threw them away or burnt them on Bonefire Night, as a new hull could be built in a weekend and finished the following. Hope job goes Ok.
Regards Alan
alan watson
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Re: DO PROPRIETRY WOOD HARDNERS AND ROT KILLERS WORK

Post by alan watson »

Thanks again to you all for your advice. Briefly :

Hull stripped, most rot removed all I could get to at any rate holes filled

Sanded faired filleted where needed and skinned with 135 gm glass cloth and patched with 200 gm carbon.

Three coats of high build epoxy and sanded. However I have now run out of workshop time. I was working with Mike Cook of Aardvark Technologies in his workshop wich was very interesting with Moths OK masts and Int Canoes all being worked.

Next job topcoat and decking.

Thanks Again
Alan
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