Cracks in clinker Folkboat planks

[joliette]

I was looking at a friends clinker Folkboat at the weekend. I found cracks along the edges of a few planks, just aft of the chainplates, in the vicinity of the waterline. The cracks are right along the rivet line of the lands (where one plank overlaps the other) extending over a distance of about 1 metre. This features across a few parallel planks. The cracks are very clearly visible on the inside and can also be seen under the exterior paint, so are developing right through the lands.

I suspect this has been caused by the short aft chainplates that have been fitted and the resulting stress across the planking when the boat is heeled. Some of the frames are doubled in this area so my suggested solution is to scarf in new sections of planks and to put in much a longer aft chainplate, extending 2 or 3 planks lower than the cracked planks.

Has anyone come across this problem on clinker Folkboats before and is there a best practice solution?

What would you do?

[skaraborgcraft]

I have a folkboat with split planks too, but my splits are in the middle of the plank rather than across the fastenings. My planks also close up after being immersed for 48 hours. Is the rig been altered? Is this a standard Nordic Folkboat, or an East German built or UK copy? I have only a single shroud each side,bolted through a large backing pad and the planking. My boat was built in 1949 and there is no sighn of any stress in the area you are talking about. I have been putting of replacing the plank,only because she is tight shortly after launching,and doesnt appear to take on any water through the planks,or through the lands when under sail. Hard to say without seeing a picture the extent of the splits, but if its loose around the fastenings i would be more concerned that the plank may suddenly spring. Sounds like you need a new plank section and re-fasten.

Im just about to post a thread on a split plank myself.....

[RFNK]

Loose fastenings will cause it but it's also common to find clinker boats with the rivets in line too close to the edge of the planking. My Folkboat has plywood planks so it doesn't have this problem. The chainplate fastenings could be corroded, placing unfair stress on some chainplate fastenings. I'd draw out the chainplate fastenings and replace them and I'd check the fastenings to the frames throughout the midsection. Once all that's sound, I'd cut out the split bits of planking and replace them, using butt blocks to reinforce the new joins. Alternatively, you might be able to grave a new strip in if you can rout out the splits but it's likely that you won't be able to do this as it's along the edge. You might be able to run a new edge along the split parts but you would need to get the old planks very dry and clean for gluing. As above, pictures would help.

Rick

[joliette]

I think she's a UK build. She has an alloy mast, although I don't know if this is original. I am now wondering if the rig could've been overtensioned. This would certainly stress the planking and could cause cracks to form along the lands ....?

[Mark Reuten]

I've come across this as well. My solution to the split repair was to remove rivets in way of the split. Route a slot for a spline along the split but holding back from the full plank depth just a tad. Glue in spline with a flexable adhesive. In that case I used Petit Flex-poxy but now I would try West System G-flex or even polyurethane. Fair off and fasten. My repairs were below the waterline and ten years on still holding fine. In your case, I would put time into diagnosing the cause. Sounds to me like a combination of bad frames and stress from the chain plates. An over-tensioned rig sure wouldn't help.

[skaraborgcraft]

Alumnium mast? Sounds like a deck stepped job,and probably more than one shroud, and overtightning. The above is a good fix too,makes for a neat job.

[joliette]

I've come across this as well. My solution to the split repair was to remove rivets in way of the split. Route a slot for a spline along the split but holding back from the full plank depth just a tad. Glue in spline with a flexable adhesive. In that case I used Petit Flex-poxy but now I would try West System G-flex or even polyurethane. Fair off and fasten. My repairs were below the waterline and ten years on still holding fine. In your case, I would put time into diagnosing the cause. Sounds to me like a combination of bad frames and stress from the chain plates. An over-tensioned rig sure wouldn't help.

The cause has now been diagonsed: she was fitted with a (keel stepped) high aspect aluminium mast with the rig wound up tight for racing, and she was very successful ... but with consequences!

What is the advantage of using a flex epoxy for carrying out repairs like this in planking? I generally use either a foaming poly if I have a really tight fit or an epoxy (Gurit SP 106) if I need some thickening to fill gaps.

[Mark Reuten]

The advantage of using the G-flex is that is is tolerant of higher moisture contents when bonding. When I used the flex-poxy the idea was that it had a high degree of compressibility which would help prevent causing further damage when the plank swelled up. The flex-poxy had a consistency much like dense silicone. The product is now off the market.