There have been some great discussions on steam bending on this forum. I needed some tack strips for my touring so I am bending some out of oak.
This is my steamer.
I made this form out of scrap lumber.
My oak is old and dry and the first ones fractured. The top picture shows one glued and clamped in place. The second strip is glued. The bottom one is the pattern used to build the form.
These are the fractures.
I have started soaking the wood in water now and the fractures are much less severe. It's a fun project and makes me appreciate the fact you can buy better strips already made or the ploy stuff that you can heat and bend. These are not perfect but will work fine. Thanks to those who have shared their experiences.
How do I get the clamp concession?
Would it help to bend less at a time and re soak every time before bending, or is that the hazard of oak?
Bob, I never have enough clamps. I'm not getting enough steam out of this little set up. You only have a couple of minutes to bend the oak and then it won't go back in the steam tube. If I were doing more of this I could build a better steamer but this will work for what I need.
You have quite a set up there. A more reliable method for tight bends is to add a metal strap on the outside of the bend so that the wood deforms mostly in compression and not tension where it may pull apart and crack. I don't know how that would work with compound bends like the tack strip.
Thanks Jim. I did use a steel bar but it started splitting the other direction. The water soaking before hand seems to be preclude the need for it. I have several more to do and by the time I'm finished I'll know all I need to to start.
I recently had my first experience steam bending oak tack strips. I must say that I was very apprehensive at first. Fear of the unknown (for me anyway).
I made tack strips for a '14 Wide-Track Roadster and a '27 Touring. As a matter of fact, it was a "Green" '27 Touring. Montana 500 folks will know what car I'm referring to.
We had a length of 3 in. dia. galvanized pipe threaded and capped on one end only, filled about 1/3 full of water and placed it capped end first, laying as horizontal as possible, into a lit propane barbecue.
Next we placed pre-cut strips of white oak, lengthwise into the pipe. The wood strips had been pre-soaked in a swimming pool for a week prior to this operation. I had also inserted drywall screws with a length of wire attached to them into one end of the wood strips to aid in removing them from the pipe. I should also mention that the strips were just a little longer than needed to reach from the center of the body, out to the end of the lip of sheet metal.
When water began to slightly bubble out of the outer ends of the strips, I figured it was time to start. I was right.
While wearing heavy leather gloves, I withdrew the first strip of wood, placed it approximately at the center of the body and started shaping it to the body curve followed by two assistants with C-clamps as I went along, clamping the newly formed wood as I went.
After a quick learning curve, I found out that moving too fast would split the wood. Moving too slowly would allow the wood to cool and become very hard to bend. The trick was finding a happy medium. From there, it was cake.
The wood was allowed to cool and normalize (about an hour) while being held with the clamps. We then removed the clamps as we used screws to attach the wood permanently to the car. I installed the backrest upholstery a few weeks ago.
I always enjoy learning something new.
I used to steam white oak ribs in my father's boat shop. first we did not use kiln dried oak. Used green white oak...red oak just wants to split and has minimal bending capabilities. Next we would boil it until it was black, then place and wrap in old rugs.
For a tight radius piece like you are doing, try a spring steel strap with a small piece of angle iron riveted on the ends. Holding the outside tight to a specific length and all the stress being compressive on the inside of the bend.
I tried steam bending once I had the same thing happen so I gave up. then latter a wheel guy told me my wood was to dry, i tried to use kill dried wood, you need air dried wood .never tried again ,as I used black Lexan. charley
The trick to successful steam bending is to hold the workpiece in compression when bending. With compound curves that can be difficult but it is essential.
If the workpiece is allowed to move, the laminar movements of the fibres will allow the minor curve to relax, (You need compression) while forcing the major curve fibres to stretch and rupture.
The metal strap is useless unless the workpiece ends are clamped to it while bending.
I've built a few skin on frame kayaks with steamed ribs. I used an old tiedown strap for compression on the outside of the bend. That stop a lot if the cracking.
For the steamer I used a clothes steamer and a long polystyrene fruit box.
I tried bending the timber both dry and also after soaking for several weeks and didn't see much difference in the failure rate. This was with kiln dried timber, Western Red Cedar and Radiata Pine.
I'll see if I can find some photos of the setup.
A friend who does woodworking suggested soaking the wood in ammonia, then bending and clamping until the ammonia evaporates. Has anybody out there tried this method? I've tried steam bending, but the results were kind of hit and miss...
I use ammonia . Use pvc with a cap on the end half and let set for a day. Bends right around.
I always use green white oak. Red Oak is not any good to bend, It is too brittle. White oak is a long fiber stringy type of wood. Kiln dried is not a good choice, because the wood cells have been changed at a molecular level by the drying process and become brittle. Then if you want to stop any chances of splitting or "checking" at the end grain, soak the finished bent wood items in "PEG" it will remove all water from the cells and stabilize the wood for good. PEG is Polyethylene Glycol. Do a Google search of Peg or Polyethylene Glycol for lots of info on how to use it...
Two things I have learned in steam bending timber.
First, give up on the steam. Boil the timber in water to make it soft enough to bend. I watched a wheelwright in New Zealand make wooden felloes by boiling hickory blanks for just a few minutes. He even let me do the bending on some! A dipper of cold water was applied once the blanks were bent around his former. This cools them instantly, so they could immediately be put into old rims to hold their shape as they dried out for a few days.
As others have mentioned, if possible, the timbers to be bent should be bent under compression. How that can be done on tack strips is a little challenging. On my 1915 tourer I made my tack strip by laminating strips of marine grade three ply.
Hope this helps.
Allan from down under.
Boy this brings back memories. Way back when I was young and dumb, (now I'm just OLD and dumb), I re-decked an old 16' Lyman. Needed new oak at the gunwale where the metal rub rail screwed to. I made a steamer out of downspouting but since it was winter and I wanted something to do, decided to steam them on top of my gas stove in the kitchen! Big mistake. I ended up repainting my entire rented house, as the moisture peeled off all the interior paint! Live and learn.
Thanks for the comments. This should be a good resource for those who want to steam bend wood. It is an adventure.
I steamed some top bows in the late 90's using 2 hot plates and 2 coffee cans. The steam box had a sliding door and I could steam while bending. While those bows had some minor splitting they have fared well for 15 years in some strong winds. At least the tack strips don't carry much load.
I've bent some 5/4 white ash and never had any splits. Are you getting the temperature hot enough, you need at least 160º at the exhaust, 180º is better. Wrap your PVC pipe in old towels or rugs to keep it warm. You'll need less steam to get to temperature also. Use a cooking thermo and place it in the exhaust steam. Are you steaming it long enough? Generally you need about an hour per inch of thickness. And you are correct, there is not much time for bending, you need your jigs and clamps ready. You need to wear gloves and have a helper. My opinion is that you are not getting the temperature you need or waiting long enough. The wood should be fairly soft when you pull it out of the steamer. Looks like you have good jigs and clamping method, maybe you only need to cook longer and hotter. Mike
I agree with Mike, mostly the longer part. I watched. PBS special on steam bending wood for reproduction chariots. They were steaming wood for 8 or more hours to avoid splitting. To make a seat tack strip for my Fordor, I used a 3 inch pipe with caps (vented), filled with water and the wood strip. This was placed on a bed of charcoal briquets and "boiled" the wood for 8 hours. When I took it out it was almost like a wet noodle. It easily bent to the form (edge of the seatback) and held in place with clamps until cooled. It rapidly cooled in just a couple minutes. And I used off the shelf wood from Home Depot, presumed to be kiln dried. I think patience is key here.
I've only ever steam bent air dried white ash. Here in Minnesota, in our environment, wood air dries at a slow rate. I've never been able to air dry wood below 15%. To get it any lower took several weeks in my dry kiln. At 15%, whie ash steam bends quite nice. The only way I've ever made curved pieces using red Oak was by laminating thinly cut pieces on a form. And I only ever used Elmer's Glue-All Max.
I bent some Honduras Mahogany for a windshield trim on a prototype car we were restoring. Used
ammonia in the steamer--which was a big piece of pipe with one one on a gas burner from an old water heater. Took a few tries, but finally did it! Great looking fixture Richard! That's one of the hard parts of this process.
You guys are awesome. I had draped a towel over the steam pipe but wrapping it tighter and using claps raised the exhaust temp from 155 to 170. I also soaked the oak overnight. I borrowed a candy thermometer from my wife. I hadn't thought to measure the temperature. The bend this morning was almost perfect. I increased the steam time from an hour to an hour and a half.
Thanks again for the ideas.
The boiling of the wood as suggested for large size material is the best way to go. Making stringed instruments years ago, steaming worked well for thin (1/8 inch) work. You may want to get a copy of Fine Woodworking: on Bending Wood.
Amazon or Carriage Association of America Book store.
Richard, show us some pictures of your finished items. I really like your compound bend you made. Good Luck, Mike
Here is one of the tack strips. I have been doing lefts and today I made another form for the rights. It might be better to make left and right all one piece but much more complicated.
Had to bend some tack strips out of old oak for my 26 roadster and without my wife knowing I put them in my hot tub for three days and the bent like rubber. Not going to give her my password.
Rich, that's a nice bend with no splits. Mike
I tried my hand at steam bending for the first time building a Delivery Car body with its steam bent top lathes and rear elliptical window frames. I read everything I could find on the internet and got a lot of confusing and sometimes contradicting info on various forums and wood articles. I spent most of my research time later at the online patent office and learned what the "old timers" and one "modern" company did and why. I have always relied on patent info as being somewhat authoritative since it requires a thorough understanding of the subject in order to get past the examiners (of old). Steam bent wheel felloe patent search yielded a basic machine that seemed to work and was simply copied and re-patented years later with some "improvements" that really weren't anything. What was interesting was that a somewhat modern steam bending machine patented way later simply stated that the main thing they were patenting was the quickness with which their machine could be cleared of broken wood pieces that didn't bend right. They simply stated this was a common thing and to be expected with steam bending. I studied that and it was obvious that their machine violated all of what the 100 year previous machine patent said was necessary to prevent breakage.
I decided the earlier folks had a better idea of what was going on with the wood than the modern guys did. It seemed to me they didn't even cite the previous patents (too old I guess). I steam bent all of the 28 or so lathes for the roof of my Delivery Car and also steam bent 2 elliptical window frames and not a single piece of wood split or broke. As I understand what is going on with actual "steam bending" alone - the steam is merely a source of heat that is uniform and can completely surround a piece of wood and thus uniformly heat it up if it is in a chamber that allows the entire piece to be suspended in the chamber so that steam can surround it. Water is a by product of steam and frankly undesirable in the actual process because it causes the wood to be dried out. Putting 2 pieces of wood in a steam chamber at the same time is not going to work unless you have 2 forms and 2 teams to work on both pieces separately. The formula for 1 hour of steaming for each 1" of wood thickness is accurate so long as you begin that time when the chamber is up to full 212F temperature. Continuing to steam it beyond that time will just turn the piece to pulp like a wood toothpick in the mouth. When you have reached the appointed time you remove the piece quickly from the chamber and immediately begin to put tension on it in the direction you want to bend it and at the approximate place it needs to bend. I did this in mid air as I walked the piece toward the form. You need to have the form totally ready with clamps preset to need only a few clicks to tighten them up. You need a steel band along the bend on the outside radius and blocked at the ends so that the bending compresses the inner radius wood while not stretching the outside radius fibers. The wood resin is natures glue that holds all of the wood fibers together in a parallel configuration like a stack of horizontal noodles. When the entire piece of wood is 212 all the way through the resin will be soft for a time while it remains hot but the wood is now starting to turn to pulp. During this time you can re-position the fibers (thus permanently bend the piece) before the resin sets up again when the wood begins to cool. The entire process of steam bending dries out the wood a bunch and you cannot re-steam a part if the first bend attempt is unsuccessful because you were too slow putting the wood under tension and putting it on the form and fully clamped. If properly steamed white oak will bend like butter and is what was used for the elliptical frames. Hard Maple is rather difficult to bend and the bend radii must not be severe. Hard Maple is what Beaudette used for all of the body parts of the Delivery Car but the roof radii where not too severe so it worked. I found a good rule of thumb for "spring back" with the Hard Maple form was to bend the wood at a radius that was about half the final radius desired. The final roof of the Delivery Car had no stress in it when assembled. The roof lathe pieces were merely tacked in place with small nails to locate the parts but those nails did not hold any of the bent parts to radius.
My steam bender was a Coleman Camp stove heating a 5 gallon gas can (NEW ONE so no BOOOOM!) with a rubber hose over the large pouring spout connecting the can to a long 3" diameter PVC drain pipe with threaded cap at both ends. A few bolts drilled through the sides along the length formed a shelf that held the wood in the middle of the pipe. A turkey thermometer stuck into the chamber at the far end tells when the chamber is full of steam. A small hole at the bottom of the far end allows condensed water to drain out and into a bucket as steam blows out there too. The entire pipe chamber was laid across a couple of saw horses. I would post a picture but I took the thing apart and it is in the attic of my shop at this time. The gas can idea allows water to be added to the can via the center cap while the rubber hose stays attached to the chamber. I made the whole thing for cheap. A small 2" to 3" T fitting in PVC from Lowes plumbing department joined the rubber hose to the 3" PVC chamber near one end. All in all it was fun but then that is because it worked. Things that don't work are not near as much fun. I don't see myself as any expert in steam bending but I most certainly credit the patents as being an accurate source of info that worked.
That is some great information John. Today I added some levers and shoes to hold compression on the wood while bending it. I am waiting for the next piece to steam and then I will try it. If it works I will post the results.
One thing I forgot to mention that is super important is that you must not run out of steam while steaming a board. If a board is 1" thick then you will need to steam it for one full hour and you cannot add water as you go since adding water will stop the steam flow and allow the board to cool and that wrecks your chances with that board since the timing is really rather critical and you cannot re-steam a piece of wood without it coming out super dried out and wrecked. Most steam articles warned and I can confirm this. I knew how much water I needed to start a board in my steamer and not run out of steam. If in doubt then start up your steamer without anything in it and time how long it makes steam with a given water level. I did find out that I could turn the stove down a bit while still making ample steam. Just watch the steam exit hole and the thermometer.
pretty wild jig.
Just get good used home
hot water tank tall. Drill some 2 inch holes in top of it. drop your wood down it. Just keep eye on the water level. turn that sucker all way up. in couple of hours or less you will have wood you can bend like a pretzel.
This works pretty well. I am still getting some splitting but these slivers bend down and glue in place nicely. I will have all the strips I need before I perfect the process.
I have used materials I had around the house and garage and have spent no money on this project. It's been cheap fun. Maybe I will tackle a steering wheel someday.
Thanks for all the input and enjoy Model T-ing
I finish the bending today. For anyone following this my conclusions are:
More heat, greener wood and straighter grain would have yielded better results.
The shoes were a nice idea but didn't put pressure in the right spots. If I were to try more strips I would try a series of wedges at the weak points as I bent the wood. This worked well at a couple of points.
The metal band is a great solution if you are just bending in one direction.
I produced what I needed with a little bit of gluing and saved a few hundred dollars.
Most of all it was an interesting project and I enjoyed the ideas and encouragement.
Who could ask for more! You got what you wanted, you saved money, you learnt something and you had fun. Thanks for sharing the pictures. Mike
Maybe oak is a little to fibrous for this, maybe something like ash or maple would be a better bending wood?
I steam bent maple on the bow corners on my 22, worked really well.
I have read that white oak is best followed by red oak and then beach. I haven't tried other woods. If maple works good for you then you are doing things right. Oak and Maple are probably not the best woods for holding tacks. I guess we can't have everything.
Nice work Martin. Did you use two pieces on each bend?
No, they're one piece, I thought of doing it as slats, but thought that it would stronger corner if did them as one piece. I bent them and put them directly into the bow corner to set. You can see the clamp mark at the end there where I clamped it...I had some burned fingers a couple of times until I figured out how to hold the wood and put in the bow without touching it much...with my fingers (Ov-glove guys it really works ) because it was really hot to the touch.
I read up on the strengths of the different woods and determined that white ash or maple would work the best for these corners. Hickory was another possibility but it was too expensive, I couldn't get it any of the local stores without ordering it.
You know what, your're right they're two pieces, I forgot. The ones I took out were also two pieces also. I was considering doing it as one piece, but scrapped that idea when I took the originals out. As I remember the pieces I took out appeared to be just scraps of wood they used as corners. One thing was sure they weren't oak. But the Ov-Glove really does work saving your fingers.
Boy I would never use Hard Maple for steam bending if I could get away from it. I was stuck on my Delivery Car because it all was visible but it also didn't have any really tight bends. There is a chart I found online that showed the tightest radius that each wood could be steam bent to and white oak was at the top as the easiest wood to steam bend and Hard Maple was near the bottom. I didn't try a lot of different woods since I had the Ford factory drawings for the things I was doing and it clearly stated HARD MAPLE for the body parts I was making. It also clearly showed ASH as the floorboard wood on the early brass T's too. All the wood parts that Ford issued drawings for had the wood species clearly marked as far as I could tell so I never wondered away from the drawing spec. Hard maple is very nice and clear and smooth but it does not like to be planed and gives tear out at the slightest reversal of grain direction in the thickness planer. I resaw and plane about 300-500 feet at a time to make coil boxes. I kinda like to work with it but it did give me some headaches at times when steam bending it.
I've heard of a term called bending oak. Is there a part of a white oak tree that is better for bending than other parts?
"Bending Oak" is probably several thin layers of Oak, which would be easy to bend in one direction. You can get "bending plywood" as well. It has the grain of its plies aligned in the same direction.
I made the same piece you're making. I used oak and just soaked it in water for a few weeks. I then bent it around a jig like yours and let it sit for a month. Worked great.
Does your tack strip have the "C" channel steel piece that ties the right & left halves together?
No Jerry. I am just cutting the 2" long notches or steps in the two pieces at assembly and gluing them together. I have seen the channels on later bodies.
I hadn't heard of bending oak but it would stand to reason that one part of the tree might be better than another. Even the age of the tree might make a difference.
as a carriage collector -- i attended a seminar quite some time ago --
the topic of wood bending came up --
- the speaker claimed you could soak the wood to be bent in
hot water with " fabric softener " -- i never tried it --
FYI -- jack
the "U" channel really strengthens the back panel--If you can put it in, without it showing once your done, I would strongly recommend adding it--I'm adding one to my '16 touring body.
I've got to agree with Dave on the C channel. It's easy to make. Just buy square tubing and cut one side out of it.
Somehow folks seem to think that since the way wood was bent involved steam, that water soaking would do the same thing but without heat or that boiling water would do the same thing but not damage the wood. Boiling water probably provides the heat but also way too much water damage otherwise I should think that people would just boil wood in years past since it certainly would be simpler. Soaking wood in water for a very long time will in fact turn the wood to pulp which can be bent rather easily and unbent just as easily as it falls apart. The steam provides uniform heat at a very constant temperature which just happens to be the magic temperature at which the typical wood resins will soften enough to allow the wood fibers to shift. It is also a temperature at which the wood fibers are not damaged too much. The main problem with steam bending is in fact the water since it can dry the wood out badly as it evaporates and as the wood cools. None of the early steam bending guys tried to resteam and rebend a piece of wood once it was put in the steamer. A steam chamber if properly built and supplied with enough steam will end up being everywhere inside at 212 degrees F unless the chamber is totally sealed and pressure is allowed to build up. That is not what you allow to happen when you steam bend. You adjust the flow of the steam with the heat being controlled by something (gas valve on a stove) but also have a way for the condensed water to drain out and pressure to be relieved. All of the other methods might work on some other principle but they are not steam bending the wood they are doing something else. I have no experience with those methods. Since ammonia has been around for a long time I would think that it would be easier to do if it worked but I don't know its limitations. I do know that if the inner wood fibers are not released by the resin then the wood will not be permanently bent and will attempt to return to its original shape. I also know that too long in the steam makes the wood very dry and rough once it cools. I am amazed at the simple formula of 1 hour/1 inch timing for steam bending since although it sounds kinda general it is in fact very exactly what time is needed so that the pieces bend permanently and the wood is still sound and smooth. I experimented with both longer and shorter and neither worked as well as the 1 hour/1 inch thickness formula.
Thanks for the advice David and Jerry. This car has a substantial board on the inner side that the tack strip screws into. It seems quite strong as is. I'm not sure if the cars that use the channel had this much backing.
I have heard of boiling in linseed oil. It was very large beams so maybe that was the difference. Scott