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Gluing Planks When Wet


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We all have to bend planks once in a while. While there are several ways to do it the common denominator seems to be adding moisture to the wood. Soaking it, steaming it, whatever. The wood softens up from moisture, we bend it, let it dry out, then glue it. At least that's what I've always done.

 

While this will shape the stick, once it dries you've got a bent stick that is just about as brittle as it was before bending it. If you still have to put a little twist in it while gluing it is about as likely to break as before.

 

Lately I've read a few comments that almost sound like the builder does the soaking and bending and then glues the strake while it is still damp. Am I totally misunderstanding or is this possible? If it is possible what glue is used? I suppose you would now have to wait for the glue and the stick to dry before moving on. How do you manage shrinkage?

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place and clamp the plank in as near to exact position as possible whilst it is wet/damp. allow to dry (I usually leave overnight), then glue in place. some extremely minor movement maybe required prior to final dry gluing, but not too much as to break the plank.

 

Never glue damp or wet planks. it results in the glue being diluted, and thus not creating as strong a bond as you would desire and expect.

 

also, wood expands and contracts when it is damp. once it is dry, it will hold its shape better.

 

chris

 

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OK Chris - a couple of follow ups:

 

1. What style clamps do you use?

2. How do you manage multiple wet strakes? If leaving overnight is required (and I get that) I would definitely want to put down multiple strakes in one sitting. Otherwise it could be 4-6 weeks at one strake per evening.

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I've glued them in place when damp and had no residual effects with shrinkage.   I use white or carpenter glue to cement them in place,  getting them as tightly in place as possible.   the glue is water based,  so it doesn't affect the bonding capabilities at all......if anything,  it makes it bond better.  I tend to think that shrinkage is a byproduct of relative temperature......fluctuating humidity levels will cause wood to breathe.  folks in a dry climate might see it more than others. I also use a home made plank bender,  made from a flat pine board and plastic pegs.   with this,  I get them near the bend required,  and when dry,   shape them the rest of the way on the model

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The wood I am using now is walnut. I can bend it just fine for the most part and if that's all it needs there's usually no problem. But if I'm planking a bow or stern and the stick (bent or unbent) needs some twist to lay flat on the frames, that's where I'm getting the breakage.

 

Popeye's comment reminded me of something. Totally off topic but I was surprised to learn this - aquarists that maintain plant tanks often fasten plants to a piece of wood or a rock. The recommended way to do this is with CA. And the surfaces don't have to be dry for this to work. I was surprised about the dryness thing but it seems to be true. You just have to hold it in place for about a minute. I also would have figured CA to be toxic in an aquarium but apparently it isn't. FWIW.

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Part of the problem is kits in general.  The wood quality (straight grain, for example) is marginal along with age of the wood.  We often hear about kits with wood so brittle that it cracks in the blink of an eye.  The grain issue is a big one also as the manufacturers aren't concerned with making sure the grain is straight and the parts take full advantage of the grain.

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Hello Mark - thanks for stopping in. This is going to sound strange but similar to what you said - I can feel the brittleness in the sticks. When I'm holding one tight in thumb & forefinger it's real obvious the stress I'm causing applying just a 1/8 rotation twist. With where I am in planking this build I've broken 5 out of 21 sticks.  That seems high.

 

Should we keep our wood in a humidor? :D

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To supplement Mark's post, in addition to the run of the grain, the species used can also produce problems.

The solution is to use species suited to our needs.  They tend to be more expensive and harder.  The hardness

means longer milling time and increased wear on cutting tools. 

The catalyst for the CA glue bonding reaction is water, so the bond should occur faster if anything with a damp

surface.

Wood in a humidor?  My guess is that fungus would find that favorable.  The wood should be in equilibrium with it

finished environment.

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hey mike, 99% of the time I just use nails for the first planking. of course they are not driven in all the way and are easy to remove once the plank has dried and taken on its shape. at this stage it is pretty rare you will need any clamps to glue it into place, but if I find I do I mainly just use rubber bands.

 

I also only ever put one plank on each side whilst waiting for it to dry. ok, so it does take a long time this way, but as I am doing this I just begin other aspects of the build. here you can begin deck furniture, guns, masts etc. so you are not really losing any time on the overall build.

 

chris

 

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When I started boat building the first woods I used were lime, mahogany and walnut. I gave up on all. The problem with walnut is the interlocking grain. I found it difficult to cut and have a clean edge and when bend could suddenly break diagonally along the cross grain fibres. Shaping a strip, it could follow the stray fibres.

There are much nicer woods. It finishes superbly though!

 

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The "one plank at a time" = 

one method of planking is to

fit the wales

fit the garboard strake.

If the remaining space is large, site a batten or two to get

a smooth run and divide the area into manageable zones.

Determine the width of the first plank and fit it.  Then measure

the remaining space and determine the width of the next plank

from that, not all planks measured at once. 

Since this is wood and a complex curved surface, each addition will change

the open space in an unpredictable way. 

It kind of precludes mass application, when doing this properly.

 

It is more like two planks at a time - since P&S are measured together.

Using PVA, an hour or two should be enough clamping time and since

the process does not stress the plank, the next plank can be worked on,

rather than over night.

 

If you do not mind the holes and the support is sufficient, hitch chucks and lils will

clamp a plank with some force.  Water may close the holes, they can be filled with bamboo

"trunnels", if the lils are brass, nipped and filled - if you like the brass peg look-  I am thinking

of trying drawn copper wire as trunnels. 

Did anyone else see the photos of the old model where iron trunnels were used?  The chemical reaction

with large black stains in the planks and erosion of the iron? 

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Chris - I'm going thru my first experience with nails on another build. Although that one really doesn't need them. This build with the walnut is a single plank and I'm not sure nails are right for that. I've bunged up quite a few with the other build. Left a few marks.

 

vaddoc - you're describing the breakage perfectly. Fibers on one side or one edge start to separate and that's all she wrote. Guess I need to try and understand the grain thing better. Will also be looking for a walnut replacement for future builds.

 

I'm a boxwood biggot at heart, but I do realize there are situations where it doesn't fit well.

 

4 hours ago, Jaager said:

Since this is wood and a complex curved surface, each addition will change

the open space in an unpredictable way. 

Jagger - how true!

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I strongly urge you to read the tutorials here on planking.   If the strakes are properly cut (straight strips are not good for much of the planking)  and pre-bent while wet then left to dry, there should be no edge setting issues.  Walnut is a beautiful wood, but not for ship model planking, IMHO, other than perhaps for the wales to give the dark contrast rather than painting.  If you can,  use a more appropriate wood such as Costello box, pear or some such.  If you follow the tutorials, clamping is not needed for the most part.  Where clamps are required, Ed Tosti has provide a lot of information on clamps in his threads and in the Naiad books.  

 

Just one opinion based on my own experience over the years.

 

Allan

 

 

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I recently finished planking my hull. I used 1 mm micro screws to temporarily secure the planks. These when then removed and the holes filled with tree nails that I make in bulk. It worked beautifully but I built in scale 1:10, I ll paint the hull and my planks were 70 cm long. But maybe it can work for you

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There is no need for nails or other means of securing the planks if the wet plank is clamped in place as close as possible to the final curvature and allowed to dry.  When dry any area of the plank needing an additional bend can be wet again locally and re-clamped in place to accommodate the additional curve.  When dry if there are any slight gaps they can be closed with slight pressure when glue is applied and the plank clamped into the final position.  Very little pressure is required as clamping is only needed for the glue to set.  The gaps can be closed with slight edge pressure.

One question that was asked was about clamping issues affecting the wood.  Soft woods like basswood can be compressed by clamps - spread the force out with a wood block between the clamp and the wood.  If a dent is made in the wood by a clamp it's able to be eliminated many times by wetting the wood at the dent and applying some heat to the area.  As the heat can also loosen and reactivte the glue be sure to lightly clamp the plank on adjacent frames/bulkheads until the glue resets.

Kurt

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Allen - you are confirming the conclusion I am coming to. There are better choices for planking than walnut. THAT SAID - I do not want to start a debate about that here. I recognize that there are thousands of beautiful builds with walnut planks. Like a lot of what we do, it's just a personal preference thing.

I love working with boxwood. Anyone who has followed one of my logs can attest to that. I used it to plank Niagara (and fell in love) but that hull is painted. IMHO it doesn't take a lot of stains very well and it's too lite colored for a walnut replacement. So for that walnut color we all love, I am still looking for an alternative.

 

Kurt - I am going to give your "wet clamped" process a try. Can the drying time be reduced with a hair dryer or heat gun or does that cause too much shrinkage? I'm also curious about gluing while the stick is still wet. I've seen that CA works OK on damp objects. It was mentioned in this thread that PVA can too. Although I imagine the drying time is increased.

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The drying can be sped up with a hair dryer and I have done this many times w/o noticing any shrinkage.  You have to be careful to not heat the wood excessively - that's why I use a hair dryer instead of a heat gun (have both - hair dryer's heat is adequate).

 

As to shrinkage - I don't soak planks any longer than a minute and most times I allow them to dry clamped in place w/o any heat and have not experienced any shrinkage.  If the plank doesn't get soaked enough to expand any appreciable amount and the plank is dried w/o heat the wood structure returns to normal equilibrium and the same size you started from.  Allowing the plank to air dry assures that it returns to normal equilibrium with the shop's atmosphere thus no shrinkage.

 

I would not glue planks when wet as any shrinkage as they dry has to set up stress on the frames/bulkheads - is that adequate to break the glue joint?  Maybe.  What's the rush?

 

Kurt

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5 minutes ago, kurtvd19 said:

The drying can be sped up with a hair dryer and I have done this many times w/o noticing any shrinkage.  You have to be careful to not heat the wood excessively - that's why I use a hair dryer instead of a heat gun (have both - hair dryer's heat is adequate).

 

 

Sounds like a plan.

 

5 minutes ago, kurtvd19 said:

What's the rush?

 

Always looking for the proverbial "better mousetrap" :D

 

Thanks for the feedback. Everything you're describing makes sense.

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