rvchima

Planking Separation Over Time

My Tugboat is Developing Leaks!

 

I planked my Anteo tug boat in February of 2015 and completed the model in August. Here's the build log:

Anteo Harbour Tug (Panart)

 

This was my first double planked hull, and I was pretty proud of it.

post-806-0-13062900-1483640563_thumb.jpg

 

And now, less than two years later, the planking is separating at the glue joints due to seasonal movement of the wood.

 

post-806-0-46683300-1483640433_thumb.jpg

 

Of course I soaked the basswood planks before gluing them down to make them pliable, so they would have swelled to their maximum width when installed. Now it's winter, the air is dry, and the wood has shrunk.

 

Is this a common problem? Is there any way to avoid it?

 

mtaylor, thibaultron, EJ_L and 1 other like this

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Sorry to hear what happened to you.  One should never glue down the planks while they are wet.  The results are what happened for the reason you gave.   You can wet the wood and then pin the plank in place and let it dry.  After it completely dry it is removed and then reset and glued in place. 

 

There is no fix for this except maybe filling, sanding and repainting. 

 

Allan

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Eventually even well seasoned wood will show plank seams through paint. Humidity variation is the cause. Think of it as a badge of ageing.

EJ_L, mtaylor and thibaultron like this

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Good point Druxey.  Even Longridge's model of the Victory developed a lot of open seams on the planking, but  could that also be that was not fully framed?

 

Allan

EJ_L, Mike Y, mtaylor and 1 other like this

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Hi Rod.

Even the full size ships/boats develop joint leaks.

My rowing boat did and at the start of the season after being laid up in the boathouse for 4 months.

I just rowed it out to the sand bank and sunk her for a day.. next day pull her in and refloat her.. no more leaks for rest of season.

Not to be done with your model....

Regards Antony.

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Allan: I believe that part of the issue with Longridge's Victory model was damp storage underground during WW2, and subsequent drying out in the museum.

mtaylor, EJ_L, allanyed and 1 other like this

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Take heart it's a set back not a disaster. If it is bothering you each time you look at her fill, sand and repaint.

Cheers,

Medic :D

mtaylor and thibaultron like this

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I've had not just seams open up a bit, but strakes develop a crack or shake within the wood itself.  Winter's a killer of wooden models.

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Another reason not to soak planks before bending!!

 

Tom

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If the water content of the wood was higher than equilibrium level during

assembly, then the shrinkage should be one way.  A fix now should hold.

 

If the wood was at equilibrium during assembly and its environment has 

changed enough to open the seams,  I would worry that a reverse change

would cause a swelling effect.  If a repair that filled the cracks was made

using a hard material, then a swing to swelling would lead to a buckling

stress.  If the fastening is strong enough to resist the hydrostatic pressure

then all should hold and the water molecules would be kept out, rather

than the wood move.  If the water pressure force is the stronger one, then

the planks would probably pop up.

mtaylor likes this

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Perhaps a harder wood species, like cherry or pear, would be less susceptible to shrinking, than bass. Also, it is better to do most bending of a presoaked plank off the model, say with a hot soldering iron with an appropriate head, and glue the plank to the hull when it is 'almost' dry. That way the internal forces of the wood are minimal.

I planked a model with cherry several years ago and today it still looks like I did it yesterday. No cracks and shrinking.

By the way, it was a single planked hull.

druxey and mtaylor like this

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There is nothing wrong with soaking planks, provided you leave adequate time for them to dry out again before final fitting and attachment to the hull. Most of us lack the patience to wait, is the issue!

Jaxboat and mtaylor like this

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I agree Druxey. I once lived in a converted 225 year old converted Barn. The builders cut all the beams (old growth white oak, hickory and Chestnut) in the fall and put them in the farm pond. In the spring they raised the water logged beams wet. During the summer the beams dried and shrunk rock hard. Then they put the exterior planking on. It was almost impossible to drive a nail into the beams.

Jaxboat

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Does temperature fluxuation also cause problems? I have moved my building to the garage and depending on the time of the year it can be quite cold or quite warm. I would liked to have keeper the work in the house but the dust got to be too much.

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Does temperature fluctuation also cause problems? I have moved my building to the garage and depending on the time of the year it can be quite cold or quite warm. I would liked to have keeper the work in the house but the dust got to be too much.

 

Wood has a low thermal expansion coefficient - meaning the size does not change much with temperature.   However, the temperature of the air affects the amount of water vapor in the air (relative humidity), which will, over time, change the moisture content of wood.   As a result, you may see changes in the size of the wood if you leave it in the garage at different temperatures.  

 

Cabinet makers have long know to store wood at the same moisture content as it will eventually be used.  In most houses, that's about 6% - 8% moisture content.  Since, it takes time for the moisture content of wood to change, the first thing  to do is keep your wood supply in the house, not the garage.  Second, if you can, keep the model in the house when you're not working on it.  

 

There may be another trick - over-dry the planks before putting them on the hull.   As the planks come back to equilibrium moisture content, they will swell slightly, closing up the seams, just as planks on a real ship swell when the hull is put in the water.  There was a comment earlier that this may cause the planking to buckle, but I doubt it.  

 

FYI, a version of this trick is used by chair-makers to securely hold the bent backs into the seat.  The ends of the back are shaped slightly over-sized to the holes in the seat.  The backs are then dried in a small oven, just heated by light bulbs, to perhaps 2% moisture content.  With the slight shrinkage that occurs the ends now fit (snugly) into the holes, but when the moisture content comes back to 6%, the end is solidly locked in place.  

 

So, if you're too impatient to wait for the planks to dry, make a small oven above a light bulb (or perhaps a heat lamp or a halogen).  The drying time would be pretty fast for pieces as thin as planking and you may get the added benefit of over-dried planks.  

druxey, mtaylor and alde like this

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Bruce, thanks for the great information. I have been storing my wood in the house for the most part but leaving the model in the garage. It would be easy enough to move it into the house when I'm not working on it. It's a small one right now. When I move to a bigger model I can move it inside for masting, rigging and fitting out. That tends to be cleaner work anyway.

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