How do I bend wood for a ship model? by Rob Macks

Reprinted from the Ship Modeling FAQ

The best method to use depends upon the dimensions of the stock, and on the degree of bending required. In general, wood should be pre-bent; if it is simply "wrapped" onto the model the resulting tension can easily tear the model apart after a few years. Instead, use one the methods listed below to pre-shape the wood; fasten it after it has "set" and holds the shape by itself.
First of all, you'll have better luck if you chose your stock so that the grain runs lengthwise (I've frequently found commercial strips to be severely cross-grained at some point, perhaps with the grain as cut from a board near a knot).

A thick or complicated shape may be easiest to form by carving it from the solid -- perhaps laminating the solid from a number of pieces so the grain tends to follow the final curve (I use this technique for sailing ship head-rails, which can be a half-circle in some cases).

You can also laminate a piece from a number of thinner pieces bent to a former -- the thinner the individual wood pieces, the easier they are to bend, an the necessary thickness is achieved by gluing these side-to-side over a form...the result will hold it's shape when it's removed from the form. (This method is frequently used to make "mast hoops" by wrapping a glue-coated plane-shaving around a waxed dowel and then slicing off the hoops when it has dried.)

Wood can also be bent more easily if it is wet or hot or both. Simply soaking a strip in water will make it more pliable. If you then bend it to shape, and let it dry out it will "spring" back only a small amount. Hot water works better than cold. Wood is a "plastic" material, and thus can be deformed under heat or as a result of chemical softening.

Many people use household ammonia for this purpose (instead of soaking in water) -- if you can bear the smell. It may also discolor some woods.

You can also hold the strip over a kettle and steam it. The trouble with this is that thin strips cool off so fast that you'll end up working with cold, wet wood by the time you get it in place.

For reasonably thick work, such as deck beams, I've had some success either wrapping the stock in wet rags, or floating it in a dish of water, and then micro waving it for about a minute.

It's relatively easy to wrap planks around a hull. it's much harder to bend them sideways (i.e., give them an "edge-set").

For some places where I need a plank bent edge-wise (e.g., railings), I find it easier to take a WIDE piece of stock whose thickness is the final width, and bend this piece to shape. I then saw curved planks from the edge.

Do not use these methods on multi-layer board (e.g., plywood). Water soaks the glue and causes the board to warp or split. The best way to bend boards is to score the "inside" curve and build a jig.

You can also get a good job with the plank-forming pliers and bending jig from Micro-Mark. Jig is adjustable. Using a plank bender without heating or soaking the wood will likely just fracture the wood.

{This includes suggestions from: Chris Maxfield, Clayton A. Feldman, Rich Gortatowsky, Ron Ginger, Trevor Farrell, PKAeronaut, Jack Silvia, and Keath Wong.}

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In bending planks, I use an old soldering iron I got over twenty years ago.
It no longer has a label, so I don't know what the wattage is, but the barrel that holds the nib is about 3/4 of an inch in diameter and the nib is about 1/2 inch, and I suspect it runs about 40 watts. I think it might have been used for automotive body work, but don't know for sure. Scrounge the yard sales and flea markets...

I find it works better than a plank bender, because a plank bender, at least the ones I've seen, works the arc in the plank while holding the plane of the width of the plank constant. This gives you a nice curve for a plank that would lie on the hull all in a horizontal plane, but hull planks usually sweep up in addition to curving toward the bow and stern. With the soldering iron, I can form both curves at the same time.

Here's the steps I go through:

Cut the bow and stern taper in 4 planks, leaving them about 4 inches (2 on each end) longer than they need to be on the hull. You use the extra to give you something to hold onto while you bend them and install them. Cut them in pairs, one for each side of the hull.

Float them in a soaking tray, (a piece of 4" or 6" pvc capped on both ends, then cut longitudinally in half works well for this) for about a half hour. Flip the planks over and soak for about 15 minutes more. Pay attention to which planks form a pair. Plain, warm water works fine. For some woods adding ammonia helps, for others it makes them more brittle.

While you're waiting, cut two more planks and set them aside, clamp the soldering iron in a bench vice (by the handle) so its sticking straight up, and plug it in to heat.

Work the flat of a plank against the side of the nib holder of the soldering iron, stretching it and pulling it into shape. For one side of the hull, use the side of the iron opposite to you and pull the bend toward you and up, for the other, use the side nearest you and work the bend away from you and up.

Remember that the bends need to be mirror images of one another. Work fairly quickly, and pay attention to how dry the wood is getting. If it dries out completely, it will discolor or burn. Feel free to dunk it into the water if it does begin to dry out too much. What you're doing is making steam that penetrates the wood, pulling it into shape, and cooking the water back out again.

Once you have it close to shape, you can install it on the hull.

Between installing the first and second planks, put two more into the soaking tray, and cut two more and set them aside. Installing two planks, while two planks are new in the soak tray, seems to work well relative to the timing of the soak. Just keep track of which are new. You should have 4 in the tray all the time you're working.

I've been using a cryo based glue (Krazy glue, wood & leather) as my working glue, and it doesn't seem to care if there is still a little moisture in the wood. A day later, I reinforce the joints between the bulkheads and planks with carpenters (Elmer's yellow) for as many strakes as I can reach before the sides meet the deck. I've got two hulls I did in 1986 that don't show any signs of separating, even at the strakes that are held only by cryo, but who knows how they'll look 100 years from now. I also 'nail' my hulls though, so that may also be helping to hold them together.
Keep repeating the process from step 4 until you get bored or tired. Then call it quits. When you do, clamp the keel into a keel clamp to make sure it doesn't bend while the wood finishes drying.

Note: The important message here is work one plank on each side of the hull at a time, even if you're doing the second layer of a double planked hull. Once the planks are fastened to the bulkheads or inner hull, their environment is different from wherever you were storing them. They change shape and try to straighten back out. Wood is an imperfect medium, so you can't control the shape change. Working port, then starboard, with the help of a keel clamp, tends to average the stresses out by the time you reach the gunnels. You can hide a slightly bent keel, when the distortion is side to side, when you mount the model, but if you hog the hull, there's no way to hide it.

Note 2 (for beginners): A keel clamp is fairly easy to make. Get some oak flooring, 2" wide and longer then your hull length, and drill holes about 1/2 of an inch from one edge, so you can put 1/4-20 bolts through and clamp the boards together. Slip your keel in along the opposite edge, between the oak boards. Tighten the nuts down and let it sit overnight. If you want to get fancy, and have a much easier time rigging, you can rig a stand to one side of the clamp so you can hold the finished hull in a bench vice while you're doing the deck houses and rigging.


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Another easy way is to heat up an old style electric soldering iron, clamp it vertically in a vise, and bend your hot water soaked planking strips around it, moving the strip slowly into the curve you need with second or two of contact at each mm along the way. Experiment with a bit of scrap to determine the correct contact time for bending and before scorching.
{Clayton A. Feldman, MD}

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This method can certainly be used - but you had better not try to use the soldering iron for soldering afterwards! I found that my iron was covered with a sooty residue after bending planks (of course, the iron may have been too hot. An iron on which you could regulate the temperature would be the best for the purpose.)
Anyway, the point is that wood can be bent using heat, and water will keep it from scorching. You can also use live steam to bend planks, as a lot of modelers do, but it would involve a bit of gear (heater, water container etc) and I guess you could easily get burnt. What I like about the water/candle method is that it doesn't involve a lot of equipment - and you don't have to have an electrical outlet within arm's reach.
{Staale Sannerud}


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I just use the 100w light bulb on my bench lamp...it's plenty hot for stripwood.
{John O. Kopf}

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I used to attend the very active Alberta Ship Modelers' Society meetings and the modelers have two methods.
Use a (.5in or .75in dia) copper pipe to contain the plank strips and run live steam from a kettle through the pipe. Pin planks to hull formers until dry then glue.
Soak the planks in laundry ammonia to soften them. You will have to do this in the garage or outdoors on account of the stink.
{Peng F. Mok}

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I find that the candle-and-water technique I have mentioned earlier on this group works well - I basically first bend the planks one way for sheer and then bend it the other way to lie against the frames - it takes time, though:)
I would guess that any bending technique can be applied in this manner: First sheer, and then the other way. If you use steam, I guess the whole plank will become wet and flexible - pin it in place while it dries and it should fit pretty well when it dries! Anyway. the important thing is to make the plank fit naturally in place, so the pins and glue don't have to force it to keep in place!

Different woods behave differently, too. I used obeche for wales on my Neptunus model (80 guns, 1789) and I found that it was much easier to bend and handle than pine, not to mention balsa. If the planks on the Golden Hind won't behave, you might consider buying planks of a different wood and using them instead - it is available if you know where to look.
{Staale Sannerud}


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Several years ago Philips made a travel steamer; a small hand held container which you fill with water. Plug it in and steam comes out of a row of small holes. The steam issued at a high temperature and with a bit of pressure. The purpose of the device was to steam the wrinkles out of clothing when traveling.
I found that the row of steam holes was just right for ship model planks. A few moments in front of the device and you can bend a plank to fit any stern curve. Hold the curve until the wood cools, let the plank dry, and then glue it in. There must be similar units on the market now.
{Dan Johnston}


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I am building my first mode, the Cutty Sark, and I am now trying to put the hull planks on! I can bend the round part but when it comes to bending them up or down it doesn't work for me. I am using a soldering iron and I went to Seaway and looked up how to bend plank for the hull . Please help me one more trip to the liquor store and I will be in bad shape.
{Bear Mac Coy}
You have made probably the worst mistake anyone can pull in running before you can walk with attempting the Sark as a first model. Attics and basements all over nearly every land on this planet have a Cutty Sark or Victory in some unfinished state or other gathering dust, so you are in good company. Seldom does a first time builder actually finish a kit of this complexity and usually falls at the first hurdle. That being said, let's try and help your little box of wood grow and you out of the liquor store my friend before your loved one chirps up with "I told you so's".

Bending wood is no real hardship once you know. The simplest and cheapest way is to steam it round using no more complicated equipment than a tea towel and an ordinary clothes iron. Soak the towel and wrap the wood up in it a plank at a time and then iron the towel with the iron set on very hot. The wood should be really supple when it emerges from the towel and will stay so for a few minutes so you will have to work quick to bend it round the frames.

You will need a pack of wooden clothes pins, the sort that has the tension spring in the middle. On the profile of the gripping end, cut a piece out about half way up the profile so you have an 'L' shape. Inside the gripping end glue a piece of 240 wet & dry abrasive paper with contact adhesive. On the inside of the squeezing end, glue some more 240 and make a timber wedge to fit. Around the spring, wrap some string to stop the peg separating. It doesn't have to be too tight - just enough to stop too much spread. Once one has steamed the plank, clamp it to the frames with the pegs. The long piece of peg slides over the frame and the shoulder holds the plank in place. The 240 offers enough friction to inhibit the pin sliding off the frame. Just to make sure the pin doesn't slide off, bang the wedge in the gripping end to separate it a bit.

Now, you can't use PVA glue to glue up wet wood, which your plank will be after steaming so leave it to take the shape of the hull and to get it dry before gluing up. A hair dryer will help accelerate the drying process.

At the gluing stage you can quicken the pace of building somewhat by drilling a tiny hole the same diameter as a brass pin in both the plank and a small square of tinplate. A cut up metal oil can will do the trick here. The nail is passed through the tin and then squeezed into the plank and frame. The idea of the tin is it gives the nail a bit more spread area and it makes it easier to remove the pin for planning and sanding the hull smooth when all the planking has been done. The nail holes can be filled with small bamboo dowels prior to sanding, or 'scrubbing' as it is known here in UK yards. To make these bamboo dowels which are called 'tree nails' or 'Tennels' (trunnels, depending on which side of the pond you live). You will need a draw plate to make these and there is a very nice chap I know down Florida way who will be delighted to flog you one. You don't need it just yet and by the time you do I will have come up with his addy for you.

Right matey, this should keep you busy for a little while, out of the boozer and your misses off your back. Oh, I almost forgot.. Don't plank the hull past the deck line as it will be murder to scrub the deck smooth with the bulwarks in the way, as these can be added later. By all accounts you will have to put the camber back into the frame lines anyway, unless of course you want your Cutty to look like an aircraft carrier!
{Mike Taylor}


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The folklore about the believed advantages of bending wood that has been soaked in household ammonia has made it into the full-sized boatbuilding world. Here is a posting from kayak-building list to which I subscribe:
Bruce Hoadley, professor of wood technology, at U Mass Amherst covers the subject of bending with ammonia in his book "Understanding Wood".

He says, "ammonia interacts with the lignin as well as the cellulosic portion of the cell-wall structure."

He states," Two basic systems have been developed; immersion in liquid anhydrous ammonia at atmospheric pressure, and treatment with gaseous anhydrous ammonia in closed chambers at 145 psi pressure. (Household ammonia, commonly used for cleaning, is a water solution of ammonia and useless in plasticizing wood)."

He further states, "With the liquid immersion process, heavy duty refrigeration equipment is required to keep the ammonia below its boiling point of -28°."

The fumes produced and equipment required are beyond most small shops' budgets.

So whatever luck you have in bending soaked wood has nothing to do with the household ammonia you're using.
{Rob Macks}