michael mott

Bending with heat only

35 posts in this topic

A recent tool acquisition and remembering Chuck's tutorial on planking, and Druxey's question regarding the hot air soldering station for bending wood.

 

I can say that the tool works brilliantly for this task.

 

The photograph shows a strip of hard maple .041"  x .125"  using the middle sized nozzle 1/4 inch diameter and using the highest temp setting the strip became very pliable in seconds

 

The other strip is .o41" x .2" Castello and it was the same in seconds it became very flexible and bent very easily.

 

post-202-0-11516800-1479419294_thumb.jpg

 

Obviously there are all sorts of other tests that can be done at varying temps etc but I have a feeling that this tool will be a very useful one in the tool kit from now on.

 

Thanks again to Wefalck for putting me onto this tool.

 

Michael

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It is one of these

 

post-202-0-64103800-1479420715_thumb.jpg

 

the unit on the left is the hot air soldering handle mine came with three nozzles 1/2 inch 1/4 inch and 3/16ths

 

The air can be dialed from very low to quite high over a scale of 1-8 the temperature can be adjusted in 1 degree increments from 100c to 480c

 

This temp range also applies to the soldering Iron side on the right hand side this is the unit that I purchased.

 

Michael

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The components of the wood are not soluble in water.  The function of

water in bending wood is:

to transfer heat more efficiently

to retain the heat longer

to inhibit the cooking or charring of the surface of the wood where the heat is applied.

 

With thin wood, the difference in heat transfer with and minus water may not be significant.

The balance is to apply enough heat to liquefy the lignin  without oxidizing the wood.

 

The negative effect of water is that it swells the wood fibers and leaves a previously sanded

surface uneven.  Most of the time, this swelling effect only occurs with the first exposure to water,

if water is applied, allowed to dry and then sanded - subsequent water usually does not swell the wood

any further.

 

To readdress a subject of folklore: aqueous/household ammonia does not help in bending - other than what

the water it is in does.  The ammonia part only has negative effects.

It takes liquid ( anhydrous ) ammonia to debond lignin for bending.  This is an industrial chemical: even if

a civilian could obtain it -  that would be a really bad idea.

Seventynet, mtaylor, davec and 9 others like this

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Michael,

 

Maybe I missed it elsewhere, but what temperature are you setting it for when bending the planking.   I know auto-ignition of wood varies with species, but was curious as to what temperature settings you have tried for the Castello.

 

$99 does not seem terribly expensive and is worth the tranquility derived from not using her hair dryer!

 

Allan

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Hello all

I have only done one test so far, it is my intention to do some extensive testing across a range of Temperatures and times with different thicknesses and types of wood. as soon as that is complete I will publish a chart of my findings here.

 

Michael

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Real yacht builders, back in the days when the yachts had to be planked rather than coated with resin, used to use steam boxes. That was how they made the planks conform to the needs of the hull.

When I soak my planks in boiling water, I'm doing the best I can to emulate the methods of the old builders. Hell, they weren't even all that old. I actually witnessed the procedure less than ten years after WW2. Hair dryers, or the similar-but-more-lethal hot-air paint strippers, might be a more modern way of bludgeoning our micro-planks into submission, but sorry, I'm just a backwards-looking traditionalist,

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Hair dryers, or the similar-but-more-lethal hot-air paint strippers, might be a more modern way of bludgeoning our micro-planks into submission, but sorry, I'm just a backwards-looking traditionalist,

Brian I take it then that you do not use scalpels or micro saws or modern glues, but  get out the adze  or take a spell in the saw pit then split up some treenails, oh and  heat up the old glue pot..... I couldn't resist Sir.

 

One has to accommodate all modes in this wonderful hobby of ours.

 

Pressing on, after an evening of cutting and testing a variety of width thicknesses and temperatures, I am not sure that a chart would be all that useful.

 

This is what I discovered though. I used my small clamp fixture to hold the various test pieces.

 

post-202-0-44558500-1479523784_thumb.jpg

 

The smallest being .025" x .085" and largest being .125" x .280" of Castello

The smaller sizes worked well with a setting of 212f

 

It was better to use the hotter temperatures with the thicker wood. I was able to bend easily .060" x .225" with 300f and very easily with 450f  because the nozzle is so focused I was able to hold the  wood quite close to the bend area . All of the bends were free formed and let go a few moments after the heat was removed. I had 2 structural failures because I was too aggressive with those bends.

 

It was easy to char the wood at 400f

 

The heat gun is very easy to adjust and only takes moments to get to temperature, In my view the tight focus of the heat is the best feature of this tool

 

Here are a couple of shots of the tests, the five pieces on the left are yellow Cedar from .070" x .450"  and .162" x .10"

 

 

post-202-0-51676400-1479524816_thumb.jpg

 

I would recommend this tool to anyone who needs to do any heat bending or soldering 

 

This was just done with the same hot air, the thin strip of flat stock .007" x .062" joined to a small section of 1/2 round .038" x .020" I placed a small piece of flattened solder between the springy flat piece and the 1/2 round.

 

post-202-0-51133100-1479526121_thumb.jpg

 

post-202-0-32600300-1479526142_thumb.jpg

 

Michael

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Real yacht builders, back in the days when the yachts had to be planked rather than coated with resin, used to use steam boxes. That was how they made the planks conform to the needs of the hull.

 

Indeed... because it was, and still is, impossible to apply dry heat to such large real-world piece of wood.  But if it WERE possible, they probably would have done so centuries ago since, as has been well documented now, water and steam are only carriers of the heat which is what does the actual work of softening the lingnin.

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Brian I take it then that you do not use scalpels or micro saws or modern glues, but  get out the adze  or take a spell in the saw pit then split up some treenails, oh and  heat up the old glue pot..... I couldn't resist Sir.

One has to accommodate all modes in this wonderful hobby of ours.

 

Well yes, Michael, I do use modern tools.  I'm no Luddite.  My workshop bristles with Proxxons!  My preference for using hot water (would like to use steam, but not a practical modus operandi) is little more than nostalgia really.  But it works.  And if it doesn't, I can (and I do) resort to lamination.

 

Perhaps a brief soaking, or even just wetting, of the wood before hand?

 

Wouldn't that be equivalent to just soaking in hot water?  Or perhaps steaming?

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    One technique I have seen/used, particularly when a compound curve is involved, is to soak the plank and clamp it to the hull until dry.  I am tempted to use this method with a heat-gun, but am concerned with how it will affect the wood already in place.  Will repeated heating damage the wood?

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Chuck: Heat may make the glue release on planking (and other structural components) already in place. That would be a more likely risk than damaging wood. Of course, it's an alternative method of un-glueing joints without isopropanol....

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Wouldn't that be equivalent to just soaking in hot water? Or perhaps steaming?

I don't believe so. With one method the steam itself is the heat source, with the other the water is simply a barrier against scorching from a dry heat source (air or an iron).

 

Admittedly I'm only just getting acquainted with wood in my modelng journey, but I imagine one should use whatever method works best for a fairytale giant building a tiny ship...and those methods may be different from that of a 1:1 man. After all we don't have 1:16, 1:48, 1:350 size men on our desks helping us. :).

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...  a fairytale giant building a tiny ship  ...  methods may be different from that of a 1:1 man. After all we don't have 1:16, 1:48, 1:350 size men on our desks helping us. :).

 

Are you trying to tell me the guys who live in the box marked "palm chisels" on my workbench aren't real?

Not that they've been doing much work recently.  I think they've worked out how to siphon the gin from my workshop bottle ...

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Just on the topic of using dry heat, I took the following shot of plank bending being done over an open hearth at a ship-builder's at Essaouira in Morocco a couple of years ago.

 

That's a fairly thick plank, now with a very nice curve. It's lying on an iron bar, which probably acts a bit like the hair curling tongs, though I think this one wasn't borrowed from his partner.

post-229-0-39152800-1479594667_thumb.jpg

 

Tony

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OK, the thread is already a few weeks old, but I just wanted to chip in. Below is a picture from a dhow-building place in Nungwi on Zanzibar in 2012, where these boats are built using the traditional methods:

 

124127-72.jpg

Source: http://www.maritima-et-mechanika.org/maritime/tanzania/tanzania.html

 

The scorching shows that an open flame was used to soften the garboard plank, which then was held in shape and place until set using various clamps and levers.

 

Steam-bending was and is a common process in furniture-making. The most famous of all probably is the German firm Thonet, that had before the war their main production facilties in what is now the Czech Republic. They made incredible complex pieces using massive cast-iron pattern to hold the steamed wood in shape until set.

 

On the hot-air soldering station: I got mine several years ago and use it on all sorts of heating tasks between 100°C and 400°C(not F !). No problems with the equipment so far. I rarely read product reviews for such things as I feel quite capable to deal with issues. One problem is that people pay KIA and expect to get Mercedes. There is a reason why things are cheap and not only economy of scale, so I am prepared to rectify (some) issues as a trade off for a lower purchase price (that not necessarily guarantees quality these days). A lot of the Chines-made equipment has to be considered to be in an 'advanced stage of production' and you can finish it to your requirements. With this attitude you safe yourself a lot of aggravation.

 

If the air-gun comes on, when the main switch is off, this is, of course, a concern. However, by looking at the wiring, it is easy to tell, wether the main switch is really the last element before the wires leave the box. If not this would need to be rectified. Otherwise, I have all my equipment plugged into extensions that can be switched off and that are so, when I am not in the workshop. Or, I unplug pieces of equipment out of principle.

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Tony, and Wefalck, thanks for those interesting photographs of traditional work being done with "low tech". All the work that we do in my view is a set of procedures that we learn from successes and failures, we continue to use and improve those that work and generally discard those that don't. The ones that work are also subjected to our human inventiveness and we look for ways to assist those methods that work. Sometimes a happy accident leads to a whole new way of accomplishing a task.

 

It is with this mindset that I am willing to try out new or different ways of getting to that success mentioned earlier, this often comes as a result of a simple question "what if?"

 

This whole thread was the result of Druxey's question to Wefalck "This sounds like a very versatile tool, Wefalck! At low setting, have you used it for bending wood?" and his Answer "No, had no need (yet)"

 

Having made a steam box to bend small pieces of wood and also watched Chuck's planking video where he bends a small piece of wood with a regular hair drier type hot air gun, I thought it would be worth following up on Druxey's question, will I use this for all my heat bending in the future probably not but i will definitely use it for quite a few time that I need to bend a small piece of wood.

 

Don I have not tried to edge bend yet I suspect that it will work well enough the key it my view is to ensure that the wood stays flat as the bending is done, perhaps another form of jig needs to be devised which can be as simple as small wooden clamps set to prevent the the tendency for the wood to want to rotate to bend in the thin direction.

 

Michael

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I use clamps to hold the wood in an arc for edge bending and a hot air gun to supply the heat.  I've found that if the wood gets hot enough (wihout scorching, it will hold the curve when cool.  If I didn't get it right the first time, a quick dip in the water bucket and back on the jig and apply the heat gun again.  

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