# Instruments and Equipment > Builders and Repair >  Method & Jigs for steam bending F5 sides

## Roxy64

does anybody have a sucessful process and jigs for steam bending the sides for an F5 mandolin (as opposed to a heated bending tube).  I've been experimenting with different jigs and forms and just cant seem to sucessfully bend the tight curves without some breakage or splintering.  I've been using  .125" thick maple and steel backing strips on the various bends.  I'm now on ~ my 10th iteration on jig design and about ready to throw in the towel.

Spring back is also a problem and I've tried to compensate for it by using progressivally tighter curves which increases the breakage\cracking problem.  There has to be a "happy medium" between curve shape and springback.

My steam box works great and heats the wood to ~200 deg F & I've been letting the strips steam for 1/2 hr.  I'm finding it very difficult to coax the bends before the wood cools too much.

Any suggestions would be much apprecited.

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## nkforster

If you are doing this for the enjoyment of building, and not just trying to churn 'em out, I would urge you do do it by hand. Here is a clip of me bending a guitar side, it should give you a few tips. If you trawl through my other clips I go into the process in a little more detail and from different angles, but basically, mandolin sides are not hard to bend. It's a nice job to do.

http://www.youtube.com/watch?v=9jf8J6rt6ng

http://www.nkforsterguitars.com

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## Jessbusenitz

Your sides may be a little thick, causing them not to bend as nice, I know Siminoff's book  suggests .125, but some people go down to .65 .  LMI offers an electric heating strap that you could put around your form to help keep the wood warm longer. Just my .02  http://www.lmii.com/CartTwo/thirdpro...ket+%26+Timers

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## sunburst

Curly maple does not like to be too wet for bending, it will crack and break much easier when it is too wet. I suspect you're steaming too long. I also agree that .125" is too thick.

I've steam bent curly maple many years ago, but I use a hot pipe for instrument sides.

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## Roxy64

Thanks,  I thought that my test strips were a little too thick.  I researched some of the other threads and found one that recommended using a heating blanket & form.  I looked up LMI & they have a heat blanket for mandolin sides. I want to try this method. 

http://www.lmii.com/CartTwo/thirdpro...ket+%26+Timers

Thanks for the video clips, I'm really interested in finding an efficient process to bend the sides with a very high degree of consistency.

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## Mario Proulx

Once you get the ribs down to .070" to .080", you'll find them a lot more forgiving. The higher the figure, the less water I'll use, too; moisture simply helps conduct the heat into the wood, and we really don't even need moisture if we take our time. I get my pipe as hot as I can go without burning the wood; I will allow it to lightly scorch if the rib asks for it.

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## barry k

Im on the less is best bus. Dont pre soak maple,  get a misting spray bottle and spray as you bend. Also as Mario states, get the bending tube hot, if it scorches a little...so what, your gonna sand anyway. The .50 to  .80  thickness is the right way to go.  Some Gibsons that I have had apart for repair  had areas of the sides that were .20 and .30 thick.

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## Dale Ludewig

Barry, I think you meant have a zero to the left of your numbers.  
Back to the OP: In any case, .020- .030 is really thin.  I think violin sides are usually about .040, as told to me by a fairly well known fiddle builder.  I used to bend mandolin sides at .100 but after some well given advice I went to .080 and it made a world of difference.  No soaking as Mario was saying with highly figured wood.  Also, if you're going to use a jig and bend, you might think about getting a heat blanket, spring steel to support both sides, etc.  That's going to run into some bucks before you even get the jig forms figured to accomodate that setup.  I would certainly learn to do it by hand on a bending tube/ iron before investing in something more elaborate, even if you're planning on going into production.

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## barry k

OOPS........... :Redface:   I stand corrected, dang I hate getting old !! :Laughing:

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## Steve Sorensen

I just went from bending nightmare to bending success with the 0.065 advice!  I can't imagine how Siminoff bends curly maple that is 0.125 . . . I sure couldn't.

Sure hope his other measurements aren't so "generous". :Laughing: 

Steve

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## Keith Newell

I get a huge satisfaction from hand bending my mandolin rims. It is amazing how certain species bend so much easier than others. I agree with Sunburst that heavy figured maple if too wet will pop and split. With that one I have to have higher heat and more patience on bending. Also you can work on your playing calouses with a hot iron  :Smile: 
Keith

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## Steve Sorensen

Gary, 

The other KEY bit of advice here is to not soak figured maple.  

I used a bit of wet teeshirt and just lightly swabbed the strips once before starting to bend.  For tighter bends it took 2 - 3 cycles of bending and lightly re-wetting with my little bit of rag.

If a section of the strip was thicker than 0.075" I started to have splitting troubles . . . but much less than when I tried soaking the wood first.

Cool how you can see the moisture come through the strip to the dry outside just as it releases and bends.

I used a setting of 5 1/2 to 6 on the Ibex iron.

Steve

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## Michael Lewis

To the original post, 200F degrees is not steam, but a sauna.  200C would be live steam, and with that you could bend 1/8" maple easily.  that is what Roger Siminoff is doing.

Be very careful if you are doing live steam as it causes the absolute worst burns to human skin.

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## Lefty Luthier

I regularly bend 0.125 curly maple rims. The key is to get the piece very smooth; I sand to 400 grit before bending. I use a quick dip in boiling water, not long, and then use an inside shaped form to roll the volute area by pressing hard against a flat surface. Once that critical area is shaped, I dip the balance of the rim piece into the boiling water and clamp it into an outer form the shape of the completed rim and leave for 2 days before assembling the other rim components. There is nothing wrong with using a bending iron but it is more difficult without thinning the rim down below 0.100.

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## Steve Etter

Lefty - any chance you could posts a video or series of photos of your process?  I would love to see it in action (especially a video).

Steve

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## barry k

Why would you want sides thicker then .100 anyway? .080 for that matter. Seems like overkill to me. Lighter is better , and thinner is lighter.  Just out of curiosity, what is the thickness for the sides stated for on HOGO's plans..I have never seen a set. Where do (did) most of you guys (and some gals) get your dimensions from for your mandolins?  and yes, I  agree that violin sides can run from .020 to .040

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## Roxy64

I've got the latest version of HOGO's plans and they set the rim @ .1" (.08-.09 nominal)  & Siminoff starts w/ .125 to bend and sands to .110- .115".  

In reading the posts, it appears that I need more heat.  I thought that 200 deg would be adaqate, but it appears that more like 300-400 deg is needed to loosen the wood up enough for a tight bend w/ no springback.  I use an old pressure cooker as my steam boiler w/ 1/8" fitting & coppper tube to evenly distribute the steam in the steam box, which is fabricated out of rigid foam core insulation.  I'm not quite sure how to get the steam any hotter without some kind of pressure valve that enables the boiler pressure to substanially increase thus superheating the steam.

I've used a bending pipe & torch and that works but, I really think that theres a way to get better consistancy in the bends and minimize any burning.  

I'm gonna experiment with some .1" strips today to how much of a difference that makes.

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## Geoff B

For consistency, the heat blankets around a form work really well for ton's of guitars I've seen built.  I know some mando builders use them, but a hot pipe has worked well enough for me that I haven't pursued the blankets personally.

Lefty, how does sanding to 400 help with bending? I'm failing to see how it could...

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## Mark Franzke

Here is a photo of my jig and a drawing of the blocks. I spray water to mist the wood on both sides then sandwich between 2 pieces of aluminum flashing material. I use a tea-kettle with a gas-line hose and brass nozzle to shoot steam at the wood as I bend. Once I get it bending, I use a clamp to slowly press the side into the concave side first, then work around the scroll. The real key is to make sure the aluminum is tight against the wood when you go around the curve. This will keep the wood from splitting (most of the time). I leave it in the fixture for a couple of days to make sure the moisture is all out, and it holds its shape without springing back.
This method still takes a lot of practice, just like everything else. I keep plenty of rib sets on hand because I still split some of them, but I have had success with this method. Wear gloves!
I start with the ribs just over .10.

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## Roxy64

so for your method, you dont actually heat the wood in a steam box.  How long do you have to spray the steam on the spot that you want to bend before it becomes pliable?

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## dunwell

Mark, I tried a similar block system but used a 2" wide heat blanket on the outside. It "sorta" worked but it was awfully fiddly and I never used it.

I'm remembering a cool jig that I saw somewhere that was made with a motorcycle shock cover for the circular center part and the a lever gizmo that pulled around it. There was a block for the rest that came around to the waist. That block also had a slot it it that you stuck the side into for the start point. You put the side in, topped it with a heat blanket and a metal slat and then pulled the lever slowly around to the waist and it pulled the whole mess around and down snug. Just slicker than goose <ahem> on linoleum! Michael, was this your rig or am I remembering wrong?

Alan D.

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## Lefty Luthier

> Lefty - any chance you could posts a video or series of photos of your process?  I would love to see it in action (especially a video).
> 
> Steve


Working on same for my new website as well as a few other techniques that were learned the hard way over the years. Hope to have the site up and running about 1/15/10.

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## Mark Franzke

The wood starts bending right away, but ease it into the tight bends. Let the wood tell you. I leave the aluminum strip longer than the rib and pull on it to bend around the curve. That way it stays in tight contact with the wood. It actually goes pretty fast. If you have a helper, it is pretty smooth.

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## Dale Ludewig

Hey Keith- try wearing welding gloves!  That's I've gone to.  

As far as the temp goes, I have one of those thermometers from stew-mac that sits on the heating iron.  I'm not sure what my temp is.  I just know it's running on about 9 (is that 11?).  It's hot enough that when a bit of spittle drops on it (sorry)- it doesn't boil per se.  It turns into a bouncing bubble and then is gone.........

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## j. condino

Wow!!! .120"- you sure won't need to worry about warranty issues with ribs that thick! Even on a carved double bass, I shoot for about .090" rib thickness and my favorite pre-war Martin had ribs that spec'd out to about .065". 

Around .200" is the thickest that I can consistently bend ( solid linings), but even at that, you will get compression on the inside of the curve.

I've been lusting for this setup from Tom Ellis after it was posted here a few months ago:

j.
www.condino.com

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## Dale Ludewig

Now that is almost mando builders' porn.  I believe we're looking into quite a bit of investment there.

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## Roxy64

HOLY SMOKES!! Now thats what I'm looking for.  I think I'll have more fun building the jig than the mandolins that come from it.

Any more info on it?:

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## BadeInBulverde

These photos were taken in October when I attended the Siminoff Lutherie Camp on F5 building ... one of the very first demonstrations Roger did was to show us how he bends the sides with steam (a bending jig and setup he custom built that is indeed a sight to behold in operation!) ... I doubt he ever has much breakage with this setup but it is a beast!

http://picasaweb.google.com/BadeMill...33252609520594

There are several pics before and after this one in the web album of the operation

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## Michael Lewis

I like Tony Pires' saying "to make it complicated it takes an engineer, to make it simple takes a genius".  Yes, Alan, that was a rig I made.  It worked well enough but now I bend by hand on a heated "iron" because it is just plain simpler and causes much less damage to expensive materials, and is fairly quick.

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## siminoff

We're bending regularly with steam. We prepare our mandolin and mandola ribs to .110" and soak them for one hour in an open trough of water. Our steam chamber holds 15 gallons of water and is heated with a 4500w 220V heating element (like you have in a electrically-heated household hot water heater). The chamber is made of steel pipe welded together and has two compartments: the lower portion holds the water and heating element, and the upper portion holds the steam. The chamber takes about an hour to heat up and to build up to about 50psi of steam (it has a pressure relief valve set to 60psi). The steam is lead from the chamber through a 10' length high-pressure (reinforced) rubber hose to a gate valve and a pipe/elbow assembly that acts as a sort-of sprayer head. The wood is taken from the trough and placed in our three bending fixtures, and the steam, under pressure, is applied directly to the part as it is being bent. Under direct steam, and at about 215° (as Michael Lewis suggests), the wood bends like leather. One great feature of steam is that the temperature is always consistent. After the parts are bent, they are quickly moved to drying fixtures of slightly-tighter-than-final shape and allowed to air dry (which they do quickly) in the California sun. We bring them back to about 14%-16%mc before they are removed and packaged. We bend about seven (7) sets of ribs an hour and rarely have any breakage. We use this process to bend maple (all types), walnut, mahogany, rosewood, cocobolo, claro, koa, etc. Bade's photos (above) show the fixture that bends the piece from scroll to lower point. We show our campers how to do steam bending (so any campers who attended our program can attest to how easy and fast it is) but I have not made drawings publicly available because of the huge liability of someone building a steam chamber improperly that fails. (While I do have a drawing of the steam chamber in m_y book Constructing a Bluegrass Banjo_, the publisher did not want me to include one in _The Ultimate Bluegrass Mandolin Construction Manual_ for liability reasons). Gibson used steam also. Here is a photo of Gibson's steam chamber I took in 1970 or 1971 (Kalamazoo, lower floor, back of old building). I have pictures of Gibson steam bending fixtures, but will have to dig for them - I hope to post them soon.
Happy New Year to all...
Roger

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hank

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## SteveB

Yes, I shoot for 0.07-0.08 too.  Then you can also live with some of the inevitable springback without breaking.   I read somewhere that Dude thicknesses to 0.065.

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## Jim Baker

I was just reading that it is the heat that softens the wood and not the moisture. Also that, with thin sections like sides, it is useless to steam or soak before bending because the wood cools before you can make a bend. 
I watched one video showing a builder bending over an iron that was covered with a damp rag and bent over that. It seemed to work well. He would wet the rag periodically when it dried out. Just another example of creating steam to drive the heat into the wood.

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## thistle3585

> I was just reading that it is the heat that softens the wood and not the moisture. Also that, with thin sections like sides, it is useless to steam or soak before bending because the wood cools before you can make a bend. 
> I watched one video showing a builder bending over an iron that was covered with a damp rag and bent over that. It seemed to work well. He would wet the rag periodically when it dried out. Just another example of creating steam to drive the heat into the wood.


If I recall correctly, Bob Taylor doesn't add any water to the wood when he bends his sides but utilizes the moisture that is already in it.  I worked in a kitchen while in college and I was told to never pick up a hot pan with a wet towel.  Of course, it was a matter of days before I pulled a pan out from under the broiler with a damp towel and it immediately burned my hand.  That wouldn't have happened with a dry towel.  I think the moisture simply acts as a conduit to heat the wood quicker.

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## Lynn Dudenbostel

I had the good fortune to visit Rogers shop in 2007 and he cranked up the side bending fixture and demonstrated it.  WOW!  Talk about an efficient way to bend mandolin sides!   I had dreams about that fixture the next night... got up and told Roger I had a bad case of "fixture envy".  I need to take the time to build a version of this some day soon.  I'm not sure how it could be improved.  Roger is a master fixture designer/builder....and a good guy to boot.

Lynn
Happy New Year!

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## Mario Proulx

Jigging is great, and for guitars, I have a bending form for each model; I also have a 2" heat blanket and tried to make a bender for mandolin ribs, and while it works, I still keep returning to the old pipe. Simple, effective, quick, and I enjoy the process.

I had a simple steam rig for bending solid guitar linings; a large pot to which I'd add a pint or so of water; to the lid, I bolted a 1-1/2" flange and drilled out the center, and attached a 3' long length of ABS pipe to that. Placed it on a hot plate, and hung a set of linings in the pipe, held by a hook at the top. Steam for however long I had the patience to wait(20-30 minutes), then pulled them out and bent them over the guitar bending form with the hot blanket. Worked great! Then at some point I discovered how if I just wrap them up and get them to near 300° before trying to bend, they bent just about as easily.

Lotsa ways to get wood bent.

One caveat with steam: while not an issue with maple, with some nicely colored woods, it can and often will, cause all the colors to run into one another, resulting in one bland color instead of the nice variations we had before steaming. Walnut is a perfect example of a wood you don't want to steam, and I've seen it happen to cocobolo also.

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## Dale Ludewig

Mario, that point about walnut is right on the button.  In fact that is how a lot of walnut sold to the furniture/ cabinet industry is sold: steamed because of exactly what you described: bleeding the darker into the sapwood.

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## Mario Proulx

Also bleeds the reds and yellows and blues of the nice walnut into that drab brown color we know of all too well. They do it so the colors will be consistent. Sad...

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## Duc Vu

> We're bending regularly with steam... The chamber takes about an hour to heat up and to build up to about 50psi of steam... Under direct steam, and at about 215° ...
> Roger


I'm just a kibitzer, but at 50psi water boils at 281 F.

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## Hans

My ribs are sanded to 3mm. I then take a strip and run a trickle of hot water over it in the laundry tub for about an hour. The ribs are sopping wet when they hit the iron. Meanwhile the Stew Mac electric iron is set as hot as it goes, and I use a stainless strap. Works perfectly. 
I use quartered or rift sawn, no slab, and I have a special supply of soft red maple for sides.

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## Jerry Haynes

I bend side on a torch heated pipe.   And I've had my share of mishaps, burnt fingers, breakage,  wood to thick, wood to thin, to wet, to dry etc.   I have never pre-soaked any sides to bend.   I used to lightly mist or lightly dampen with a wet cloth.  I do use a stainless strap.    A few years ago, fixin to bend some sides, I let the pipe get hot and then began to wet the wood with a damp cloth.  While in the process of moving from water pan to wood to pipe, I droped the cloth and it fell on the hot pipe... steam , steam and more steam.    The light bulb went off in what brain I have,  so I immediatly grabbed the wood and my strap  and laid the wood on the steaming cloth.  
I still have to bend slowly , but (to me) this process makes bending so so much eaiser.  No more scorching the wood.   A really damp cloth will steam for quite a while.   When the steam slows down, rewet and go again.   
Caution..  as someone mentioned in a previous post... steam will leave a nasty burn.  By the time you say  Oh S--t, you're burnt !    It's not really that bad especially using a strap.

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## Larry Simonson

Somewhere in the past I read an article in a woodworking magazine where the author was bending some rather thick pieces and that his secret to bending steamed wood was to bend it first in the opposite direction a bit before bending it to the desired final form.  This apparently stretches the wood to break some of the adhesion so these fibers will more easily slide back over each other when in compression.   While I will try that the next time I bend sides, my experience so far is that there is no substitute for heat.

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## j. condino

If you head over to finewoodworking.com, their on line video series features an amazing demonstration of a fellow steam bending thick (1.5-2" !!!) oak chair pieces. He demonstrates the idea of bending in both directions to loosen the cellular bonds- the results are quite surprising:

http://www.finewoodworking.com/Skill....aspx?id=28507

Not something I use with instruments, but still rather interesting.

If you are really bored, you can also find a sunburst finishing video by one of the local "spruce dorks" around here...

j.
www.condino.com

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hank

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## Skip Kelley

James, Thanks for the video link! That bending is unbelievable! That is one thick piece of ash he is bending!

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## Mario Proulx

Interesting technique; he has to break the lignin bond because he's going to bend the wood on the diagonal, which would be a heck of a trick otherwise. I'll have to try the technique with solid linings some day.

One caveat I see, unfortunately, is that bending both ways like that may weaken our thin ribs, or make them more prone to cracking in the future so I'd suggest trying it on non-critical wood first and do a long term drying test to see if they're structurally as sound as with a regular bend.

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## Wudwerkr

excellent video  Learn somthing new everyday   :Laughing:

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## ellisppi

I backbend the sides on the pipe a bit and then start the forward bend on the pipe before going in the jig. The sides are nicely sanded to .078 before bending, and I do it pretty dry. The bending jig has a thermostat set to 320

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## j. condino

As long as we are getting sidetracked, I'll keep it rolling...I think Chris Mroz's compressed wood company redefines what is possible with bending of wood:

http://www.youtube.com/watch?v=QspGC...eature=related

If you look a bit further into his website and such, there are some pretty interesting uses for this, beyond for the world's thickest guitar sides.

http://www.flutedbeams.com/home.html

Has anyone around here used some of his product in an actual instrument? I spoke with Chris last year about getting some samples for a demo, but didn't get any farther.  I'm pretty curious how it sounds once everything sets up. I'd imagine that f you were the crusty-crusty, grumpy-grumpy type builder, there is no need for it, but if you had an open mind, your possibilities would only be limited by your creativity. 

I can think of a lot of places where triple axis bends with no endgrain limitations would be pretty interesting. Being able to fabricate a Rigel type rib profile in a traditional thickness  would be one area. A full sized double bass with no right angles at the plate / rib junctions with no internal corner blocks?!?!?!? It would be fantastic to have wood binding that went on an F5 like plastic does...

j.
www.condino.com

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## Dennis Davis

I use steam to bend sides at .110 thickness. Never have problems. In fact, the curly maple seems to love steam and hate the hot pipe. That has been my experience but everyone has to find a system that works best for them.
I guess that is called research and development.

Dennis

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## Mario Proulx

*I backbend the sides on the pipe a bit and then start the forward bend on the pipe before going in the jig.* 

Thanks for chiming-in with some first hand info, Tom. I'll file that backbend into the 'ol bag 'o tricks!

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## Steve Etter

The timing on this thread has really been great for me.  I am actively in the process of building #2 and, thanks to this thread, decided to thickness my sides to ~0.065 instead of 0.100 and still use my torch and hot pipe for bending.  After applying the slightest bit of moisture (using the moist t-shirt method) and heating the pipe hotter than I had previously (no temp values - sorry), my bends with highly figured curly maple went amazingly well - no cracks or splits at all.

Thanks guys.  I love this site.

Steve

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