Foredeck varnish cracks

25/01/2010 21:46:43
Andy Hay - 3626 Business as Usual
Having braved the cold to check on her majesty in the garage, I noticed some fine varnish cracks in line with the surface veneer on the foredeck. I can just feel them with my fingernail. Three questions for the forum experts:

1. Once I have built a tent in the garage, added some heat to get the temperature above 2 degrees, rubbed back the deck, will a single thinned coat along the crack, then a full coat over the deck make the cracks disappear?
2. Is this a side effect of the temperature fluctuations (and the cold especially) with the two pack varnish?
3. How do I stop this happening every winter - do I have to give BAU a room in the house with central heating and an ensuite - sorry, a heated garage?

Any pointers?

25/01/2010 22:43:53
Ben 2529
Hi Andy
Some years ago whilst maintaining a Solo dinghy that I owned I noticed a similar problem. The veneer was that lovely, stripey sapelee (sliced horizontaly as opposed to rotary cut ply) but appeared to be lifting at the edges of each sliced laminate. The boat was only about 6 years old so I called the builder - for help not to complain. He told me that he still had the ten year guarantee certs. for the material so I spoke to the supplier. I think they were Brunzeel etc. So, eventually they sent two guys to have a look and to cut a longer tale short ... they paid for it to be redecked. The deck was actually in very good nick, looked a treat but you could just detect something going on - and they agreed. Rotary cut ply cannot be 'stripey' and must be one complete laminate across whole 8 x 4 sheet so such a problem should not occur. Perhaps this doesn't help very much but it is getting late and is vaguely connected !

25/01/2010 23:04:43
Dave Lee
Hi Andy

I suggest you give Tim Coombe a call on 07970033489. He has done some excellent work refurbishing and maintaining many of the Driver wood Let It Rides, so should be able to offer some good advice.

25/01/2010 23:48:42
d.h.
Andy , I suggest you speak to kevin first,he will tell you where he sourced the ply from, some are made with a chamfer overlapping the veneer some are just butted,it sounds like its more likely to be the latter, im sure kev will have the answer! rgds phil

26/01/2010 00:43:53
Roy
I have the same problem with Second Thought 3570 A Laurie Smart "Make IT So". I put tape over the cracks to keep any water out before the winter. It spends the winter in a friends barn about 50 miles from where I live so I will not see it again until I collect it in the spring. Any suggestions on how to proceed would be helpful.

26/01/2010 01:26:31
Robin Szemeti
I suspect the problem is no that its got damp .. its that it has dried out.  The air in winter is a lot drier than it is in summer, plus safely tucked up in a garage and missing its weekly soaking at the lake ....

You'll probably find the top side of the deck is varnished to within an inch of its life .. and the underside isn't .. When you get significant changes in humidity, the wood moves, the varnish doesn;t and there you are, cracked.

I guess with twopack, you need to either maintain a fairly regular humidity level or make sure you coat the underside as well, and all the little gaps and cracks too. Its like epoxy-varnishing teak fittings on yachts. You cant just do the visible surfaces, you have to take them off the hull and do the backs and the screwholes too, or its Not Good (tm).

Thats my theory anyway, and I'm sticking to it.

26/01/2010 08:44:03
Colin
There's a coincidence!
I've just looked at our NSM2 (3387 - next sail no to Andy's old boat), there's a fine crack along the edge of veneer on the foredeck.

that's the first time I've noticed that. The boat's kept at the club with aa polycotton cover. I suspect that there's been a cold/dry, thaw/damp cycle which has stressed the varnish and wood (1 pot).

Once the warmer weather is here, I'll rub it down (800 or 1200 grit wet/dry), then a thinned varnsih (about 10% thinners) to soak into the minute crack, then recaot (I use about 4% flow modifier in the varnish - it really does reduce the brush marks).

I would be very careful about using 2-pack in the cold - if it doesn't cure then it's a mess taking it off...

Cheers,

Colin

26/01/2010 09:44:58
Garry R
Two pack can go beautifully milky if the humidity is wrong and that really doesn't look good.  I believe that Chris Barlow had some cracking on Spriteful and that isn't the stripey ply.  It seems that some batches are better than others.

26/01/2010 10:50:14
KM
Wasn't there a thread on this subject - of 'Brunzeel'stripey sapele no longer being able to get a guarantee for it's use for dinghy decks, and subsequently only being imported by a firm in Scotland. 
From memory, it was alledged that oven curing of 2 pack promoted the delamination. I was told by a guy who does alot of wood boat repairs it was made worse by the dampness coming from under the decks which hadn't been fully sealed (previous post).

26/01/2010 11:34:38
barnsie
Hi Andy
We had the problem with Moondance Assassin when she was a couple of years old and she was to my knowledge one of the very first boats to have this issue. Unfortunately Brunzil shut the European factory and moved all production, to west Africa near to the plantations. The veneer is glued using thin nylon strips and if the surface veneer shrinks beyond the tolerance, the veneer tears on the ply and the edges lift slightly. As this was a new problem at the time, we had full input from Brunzil. Result was that the Merlin had the decks stripped back and, believe it was sanded (Alan Jackson will confirm) and then flow coated with a new epoxy coating (Boat needs to have its core temperature brought up to make sure no moisture has entered the veneer and that if warm the epoxy will flow more readily). She was then revanished and as good as new. This was a success as we caught it very early. However, I also had a concourse Firefly 2297 Cappachino, that was the end of a series of Fireflies I had built and her decks were not retrievable as water had slightly discoloured the joints. Brunzil paid AJ to redeck the ply and she was returned to her pristine condition. Since that date she has done one Bloody Mary and that is it. She's in the workshop, wrapped in cotton wool and ready to go sailing when I need her. No problem noticed in the ply, but hardly if no UV exposure, very little curvature (MK1A) in the deck and stern tank veneer in compression, so not sure if we may have a problem one day, but she looks fantastic and is one of the fastest ever built, hence holding on to her. You just never know when the urge may call again.
3626, knowing how good she looks, I would have her looked at very carefully and if you can, get a magnifying glass (as powerful as possible) and see if you can see if the veneers have contracted and gaps have appeared. If they have it is a pro job and needs to be sorted before sailing her in anger again. Speak to Glenn and MC to see if it has happened before.
Best of luck

26/01/2010 12:52:04
Fat Pig
Seems to be a problem with all stripey ply eventually, although the older Brunzeel is definitely more resistant to this.  The curvature of the foredeck doesn't help but the sidedecks also tend to go after a few years of vigorous roll tacking.  It's worth checking that coating under the deck is in good condition, though you'd be likely to see the varnish lifting generally rather than just along the laminate joins. You'll need to get evything nice and warm (at least 15C and pref ~20C) to get the epoxy to flow in and seal up the cracks.  Unfortunately the basic weakness is still there in the ply and it will go again...

26/01/2010 15:04:16
Colin
Hi Barnsie - F 2297 that was originally one of 3 Fireflies owned by Decca SC (2296,2297,2298).
When I knew her (at Laleham in the late 60's early 70's) she was a Mk I, and the decks did need some work (problems of a Club owned dinghy).
Glad to know that at least one of the Fireflies I've known still survives in good nick.

Cheers,

Colin

26/01/2010 19:14:46
Andy Hay - 3626 Business as Usual
Wow, I love the Merlin Forum. Thanks for all the advice, I'll ring Kev first. I am with Colin in thinking that this is a temperature cycle, drying issue rather than any ply defect. The veneers look flat and the underside is clearly painted with an epoxy undercoat.

Obviously, starting to panic about getting her to the Dinghy Show in March ....

27/01/2010 09:55:51
Andrew M
Unfortunately this has been a recurrent problem with Heaven Sent and the foredeck has been back to bare wood once at least to deal with it.  It has re-emerged with the overwintering now (I have nowhere to store the boat inside) and there is an area of pale separated varnish near some cracks at the fore end of the deck.  I believe it is the ply issue Barnsie describes.  I will have it refinished (again) this year but was even considering having the foredeck replaced.

27/01/2010 10:20:32
Colin
Hi Andy,

Quick bodge... use nail varnish over the cracks (borrow some from the other half - if it's clear).
It will cover the problem (temporarily) and is easy to remove with acetone when you get to the full re-varnishing cycle.
Obviously - try in a small out-of-sight area first! - you don't want "wicked green" varnish - or sparkles!

Colin

27/01/2010 11:22:55
Andrew M
A better bodge is superglue (see link below) but this is not recommended prior to exhibiting the boat at the Ally Pally

http://www.cvrda.org/boats/hintstips/hintstips.php
27/01/2010 13:55:17
Pat2121
How about Captain Tolley's Creeping Crack Cure??? The hardware shops and chandlers seem to stock it. 
The varnish experts on the cvrda forum may have some more suggestions

http://www.cvrda.org/community
27/01/2010 19:30:43
Andy Hay - 3626 Business as Usual
Update for you all ...

Spoke to Glenn and Tim and it would appear that what we have is perhaps varnish settlement, i.e. the varnish is thicker locally where the veneers are jointed and hence this thicker varnish contracts slightly (and we are talking about a minisule amounts) more than the varnis film on the rest of the deck. Low voltage lighting in our garage exaserpates the situation.

I think I have located a nice warm (20 degrees plus) dry place, so I'll take BAU to work - something along the lines of show and tell - gently rub down the whole deck and brush on a thinned topcoat. Glenn was adamant that the underside of the deck is sealled and he had seen a similar effect before - seems that this is a common issue on Glenn's boats after a year from a revarnish.

Will post any further news and hopefully you can all inspect my handiwork at the Dinghy Show.

29/01/2010 20:49:52
Andy Hay - 3626 Business as Usual
Further update - rubbed the deck gently (well as gently as I can be) and flatted it off. "Cracks" now not visible, so hopefully all good.

29/01/2010 22:11:10
Keith Callaghan
Andy, check with Kevin to see if the deck ply is from Robbins Timber. Their stripey sapele faced 'Tiger-Elite' plywood has a history of this problem. Talk to Robbins, who should be able to advise you. Best cure is to remove all varnish, give 3 coats of epoxy, then varnish over the top. The epoxy resin should stabilise the veneer sufficiently to sort the problem.

29/01/2010 22:13:55
Keith Callaghan
Oh, just one more point - Robbins say that the sapele veneer is 1.0mm thick, but it is often much thinner, so beware of abrading right through the veneer, especially where the deck ply meets the rubbing strake.

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