PLANKING STEAM TANK

[Walter Biles]

This illustration comes from the steam tank that we used for preparing planks for bending at the Severn River Repair Center when I was in the Navy. 

 

 

 

The steam was regulated to about 30psi.  There was a shelf of expanded metal all the way through the steamer to hold the planks up out of the condensate. 

 

The valve on the upper right of the picture was opened after loading the lumber into the opening hatch on the left end and it was dogged down fully.  The steam was allowed to enter the tank with the bleed valve at the left bottom open for a few minutes, then it was closed for a bit. 

 

After about 5 minutes when the steam pressure was up to it's setting, the condensate valve would be cracked enough open to allow the condensate to dribble.  This allowed the steam to keep entering the tank, It was watched to make sure it did not let the steam to blow out.  Once it was stable, we would leave the wood in it for about an hour, and at that time, the steam was shut off.  

 

Then the condensate valve could be opened all the way to let the pressure off.  Once the pressure was down, and the steam had stopped blowing out, the dogs would be cracked and backed off carefully. 

 

One of the sand crabs(civilian shipwrights) showed me a piece of oak that I had helped him put in that was about 1"x2"x8' and I asked him how much bend could it take.  He showed me by tying a loose overhand knot in it with about a foot of the plank sticking out each side of the knot. He then straightened it out, and used it on the boat he was working on.

 

The pressure of the steam drove the moisture into the wood in just a little while.  When the steam was down, ie. not available, they tied some weight to the timber and attached a line to it and dropped it in the basin overnight.  That was not as effective as the steam, and it would not bend to the same degree without damage. 

 

I thought that some of you might find this interesting. 

Edited January 18, 2015 by Walter Biles

[figuerres]

good info on how steaming is done. i am a bit surprised at how much that oak strip would bend. but then 1 x 2 is fairly thin.

[Walter Biles]

He released it  and laid it on the floor, and it held it's shape. I think it would have done more, but he didn't want to chance damage to it because he was putting it on a boat. 

Edited January 18, 2015 by Walter Biles

[Walter Biles]

After hearing so many asking about bending wood,I get to thinking, if the pressure cooker was big enough around, I think it might work to just bow the pieces around the outer sides of the cooker and give them a pressure cooking for awhile, say 30 minutes.  I think the jar rack plate for the bottom could be used to keep the wood from getting soaked too much in water. 

 

My wife's is a 16qt.  I think I will try that next time I bend. I checked, it's okay.

Edited January 18, 2015 by Walter Biles

[druxey]

Great story, Walter! However, that might be overkill for modelmaking sized pieces of wood. I've never had any issues bending wood using the steam from a kettle. 

[mtaylor]

For all but one wood, I would agree Druxey.   I'm thinking of getting a pressure cooker for ebony, though.    I love the way it looks but that stuff is a <fill in expletive of choice> to work with.

[druxey]

Ebony? Never use the stuff, myself!

[mtaylor]

Ebony? Never use the stuff, myself!

 

I don't blame you.  I've already committed* myself for this model.  The next one... I'll do something else. 

 

* - Both to the project and to the local mental health ward.

[figuerres]

idea for our  model building....  what about the vaporizers sold for when someone has a cold or bad sinus problems ?

do some hacking / modding to attach a large pvc pipe and  hold the wood such that the steam goes into the pipe that has the wood.

no pressure just the flow of steam for a time until you pull the wood out to use it.

 

I have not tried this so I do not know if the steam from the device is hot enough or if it makes enough volume to work....

but the vaporizers are not costly and sold at lots of stores.

[Walter Biles]

The pressure is definately a big plus in getting the wood softened fairly quickly.  I am looking into an adaption of a small pressure cooker with a 3-4 foot (I work with longer wood) chamber attached with appropriate steam and condensate controls.  I believe that most pressure cookers limit to below 20 psi. It needs to be safe. 

Edited January 21, 2015 by Walter Biles

[figuerres]

with the thin cuts of wood used in most models I am thinking the need for any pressure might be less than large scale wood working.

in many cases we are only getting into say 1 to 5 mm thickness.

[Bripea]

I used my wife's fabric steamer.  I traced the nozzle end and made a cut out in plywood thick enough for the nozzle to be almost completely embedded, then another piece of play with rectangular cut out so only 3 of the nozzles actually would supply steam. I put these together and build a plywood box around it.  The lid fits on top so that there is easy access to laying the strips onto the movable coat hanger wire racks inside.  There are 3 vent holes at the back to allow the steam to pass through.  Careful when opening the lid and steaming your fingers, maybe long tweezers to pull your strips out and start bending.  I usually use the kitchen kettle but it clicks off when boil is reached.  I haven't tried this yet since I caught a finger end in my table saw to my dexterity in bending is much reduced until the stitches are out (stupid me).

[S.Coleman]

Would the steam be okay in that wooden box? I mean it won't bend the box out of proportion would it?

[Captain Poison]

Maybe covering the inside walls with aluminum foil to increase and maintain moisture?

I use an old pan that removed the handle lid leaving a hole about 1 cm,very effective..

Edited February 9, 2015 by Captain Poison

[Bripea]

I notice the lid did distort a little.  I tried steaming a number of planks at one time, which did soften them all, but noticed that if I started bending a plank then put it back in to steam some more it would have memory and go more or less back to its original shape i.e. almost flat.  Therefore I only had partial success.  I did, in fact start poking the plank in at the steam end to re-heat while shaping it, so not much better than the simple pot with handle removed idea posted after my post.  What worked best is using the fabric steamer head alone to steam and start shaping the plank, then steaming more after initially attaching the bow end to the hull. This allows me to get it closer to the bend and twist needed to run the length of the hull. I'm also going to try just two racks in the steamer and a weight in the middle to give some initial bend.

[jbshan]

I've just been reading about planking a ship in 1760.  Their box was very similar to the USN one, although made of wood.  I'm thinking they were repairing wooden ships' boats with that 1 X 2?

My book talked about one hour per inch thickness, plus an hour for luck.  Oak plank, up to 9 inch thick, up to 60 feet long.  A bit different animal.

[Walter Biles]

JBshan,

 

The sandcrabs were making a small dingy with marine plywood outsides.  The stringers were screw strips for the longitudinal edges and corners.  They had to be curved in both directions around about 3 midframes and attached to the fore and aft pieces of plywood (marine) which made the ends of the boat.  The front piece angled downward toward the keel pieces, and was only about half of the width of the transom.  It made the bow blunt but allowed for the water to channel down under the bow.  The dingy was only about 7 feet long and 4' beam.  Each side was bowed fore to aft, and the two bottom sheets were bowed along the keel boards creating a V shape for the bottom.  There were frames across the keel that created a floor in the boat.  It could be either rowed from mid seat, or powered by a small motor on the transom.  It was fairly light overall, and easily handled by two persons which was about all it was designed to hold.  

 

These drawings may not be fair, as drawn from memory over 40 years back.  But you can likely see how the pieces would have curved in several directions.  

 

I'd be interested in the book you were reading about the wooden steam chamber from the 1760 era.

Edited February 21, 2015 by Walter Biles

[Walter Biles]

Thank you for your responses to this topic.  I appreciate the variety of ideas shared here. 

That helps others to get some ideas of HOW TO do things in our hobby.