Steam Bending Stems

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Charley
Posts: 16
Joined: Tue May 18, 2004 11:58 am
Location: Ottumwa, Iowa

Steam Bending Stems

Post by Charley » Thu Mar 21, 2013 3:24 pm

I just finished steam bending the stems for my third Redbird. I developed a new technique and I told my helper (my wife) that if the rest of the project goes as much easier as this did, the third time will indeed be the charm.

I started out as “Canoecraft” suggests by deciding in what order and orientation the strips will be stacked and aligned on the stem mold. As “Canoecraft” notes, once you remove the strips from the heat, you will not have any time for such weighty decisions. I then made 15 spacers, each about the size and thickness of a dime out of slivers of scrap wood. I then bundled the 6 strips together with nylon zip ties with 5 spacers between the strips where the zip ties go. One set at each end and one in the middle. This raft-like bundle fits nicely inside the piece of aluminum gutter downspout that I use for the steam box. I have trimmed the bottom end of the downspout to fit as snuggly as I can against the surface of the tea kettle I use for the steam source. Previously I have just put these 6 strips loose in the tube but had some trouble keeping them from sliding out the bottom and even though I had them marked for the order I wanted, it took a little time when I took them off the heat to align them. I had some concerns that the steam and heat might soften or loosen the zip ties on the bundle. If anything the steam and the heat caused the wood to expand slightly and the zip ties got even tighter. With this method all the surfaces of the strips are equally exposed to the heat and steam.

After 45 minutes in the steam box, it was very easy to cut loose the zip ties with a pair of dykes and still hold the strips oriented in the bundle while the shaking or knocking loose the spacers. As I said this really worked great for me. I hope my description is clear.
Charley Montgomery
Ottumwa, Iowa

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Patricks Dad
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Re: Steam Bending Stems

Post by Patricks Dad » Thu Mar 21, 2013 9:23 pm

My approach is pretty simple.

Decide the order of the six strips. Align them and drill a 1/8" hole through the end of the stack (that will ultimately be NOT in the finished stem). Fish a 12-14 gauge wire through the hole and twist the wire to tighten the end of the stack (this maintains the order and the lengthwise alignment of the strips and actually tends to make the other end of the stack spread out a bit). Soak the strips over night (I use a a PVC pipe full of water standing in the corner of the shop. Steam 15 minutes (20 max). Bend. Having the stack of strips tied at one end with the wire makes it easy to put in (and more importantly pull out) of the steam tube. If your steam tube is vertical, use the wire hooked over the end of the pipe to keep it where you want it inside the tube). Once the whole thing has cooled and dried, remove the wire.

I've never had a bend failure with this approach.
Randy Pfeifer
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Randy.Pfeifer1@gmail.com

Charley
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Joined: Tue May 18, 2004 11:58 am
Location: Ottumwa, Iowa

Re: Steam Bending Stems

Post by Charley » Thu Mar 21, 2013 9:58 pm

This sounds even simpler than my way... Does this mean I will have to build a FOURTH Redbird?
Charley Montgomery
Ottumwa, Iowa

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Patricks Dad
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Re: Steam Bending Stems

Post by Patricks Dad » Thu Mar 21, 2013 10:07 pm

No. you don't HAVE to build a 4th Redbird. Build a Freedom next. :wink
Randy Pfeifer
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Randy.Pfeifer1@gmail.com

Charley
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Joined: Tue May 18, 2004 11:58 am
Location: Ottumwa, Iowa

Re: Steam Bending Stems

Post by Charley » Fri Mar 22, 2013 8:43 am

I'll have to check out a Freedom. Is that a "new" design since 2002?
Charley Montgomery
Ottumwa, Iowa

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Patricks Dad
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Re: Steam Bending Stems

Post by Patricks Dad » Fri Mar 22, 2013 12:56 pm

The quite popular Freedom 17 has been on the site since as long as I've been on here (2004?). I was referring to this plan:

http://bearmountainboats.com/plans/cano ... id=8254801

There is also a Freedom 15' version (which I have built).

but now that you reference "new" designs, there is also a fairly new (2009?) Freedom Solo:

http://bearmountainboats.com/plans/cano ... id=8201260

enjoy your build!
Randy Pfeifer
(847) 341-0618
Randy.Pfeifer1@gmail.com

BearLeeAlive
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Re: Steam Bending Stems

Post by BearLeeAlive » Sat Mar 23, 2013 9:48 am

I had a couple failures steam bending my cherry stems, and ended up doing a method similar to Randy.

I first laid out the strips in the order I wanted them, drilled a 1/4" hole in on end outside of the used length, put a 1/4" dowel through this hole, and then with them separated a bit, I soaked them in the tub for a few hours. Then instead of steaming, I boiled a couple kettles of water. I clamped the end of the strips with the dowel pin tight, and clamped this end to a bench sideways (with the width up and down) with the rest of the stem hanging over a small plastic tub. I put popsicle sticks between the strips to splay them apart a bit, and in the area where the tightest part of the bend would be, slowly poured the boiled water over the strips. I then pulled the popsicle sitcks, quickly mounted the strips to the stem mould, and bent them around the curve really easily.
-JIM-

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Patricks Dad
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Re: Steam Bending Stems

Post by Patricks Dad » Sat Mar 23, 2013 10:43 am

All of my outer stems have been cherry (inner stems have been either cherry or cedar). I have always soaked for at least 12 hours (usually 18- 24). I've used both dried and not dried).

When I bend stems, I always use 7 strips. The outer strip is a sacrificial strip which helps avoid splits in the lower 6 strips. I discard the sacrificial strip when done (I've never had one of those crack either but I still use them just in case).

In the case of a dowel tightly clamped through a hole in one end, while ensuring that you maintain your desired order and some separation for steaming, you might actually make the challenge a bit larger (just brainstorming here). All of the "stretch" of the outer strips has to flow through the entire length of the strips (that doesn't describe it very well). If you have some freedom of movement on both ends (which you get with just a wire through a hole in the strips, the strips can slide over one another a bit in both directions as you bend the stack of 7 strips. This might be a minor consideration.

For a stem that has a fairly sharp bend that is mostly in one place (eg., the Freedom) it would seem that pouring boiling water might work fine. I would think that it might be harder to do with a stem that has a more gradual curve over the entire length of the stem (e.g., Redbird). I know a builder who used to boil their stems and ribs (for wood/canvas canoes). I would guess you could resort to boiling the stems themselves also but I've never had any problems with the approaches I've always used (If it works, I keep using it.)
Randy Pfeifer
(847) 341-0618
Randy.Pfeifer1@gmail.com

KenC
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Location: Oakville, ON

Re: Steam Bending Stems

Post by KenC » Sun Mar 24, 2013 10:24 am

I also drill a hole through the stack at one end, and wire to keep them in order.

One other thing I would add. When stacking, be careful about grain orientation. On one of my stems, I had inadvertently flipped half the strips, which made it impossible to plane in a direction that avoided tear-out. Planing in one direction, every odd-numbered strip tore out, while every even numbered strip cut smoothly. Planing in the opposite direction, every odd-numbered strip cut smoothly, while every even numbered strip tore out. Lesson learned, I never did that again.

I have used the boiling method, for smaller items, such as a protective wrap around the tip of a paddle or for small hooks & tiedowns. Tightest bend was a 180* bend on a 1/4" radius -- 4 x 1/16" plies make for a very strong 1/4" hook. Worked like a charm.

In still other situations (moderate bend around a cockpit coaming) I have used a heat-gun for dry-bending.

Brian Hayes
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Joined: Fri Mar 15, 2013 3:52 am

Re: Steam Bending Stems

Post by Brian Hayes » Fri Mar 29, 2013 3:49 am

Thanks for sharing guys these are great tips I`m building a 19.6 flat back and this will speed up the process. Cheers!

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Kermit
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Location: Ottawa, Ontario

Re: Steam Bending Stems

Post by Kermit » Wed May 22, 2013 9:24 am

I used Patrick's Dad's techique this weekend for my stern stem. I used 3 WRC as the inner stem, and 3+1 ash for the outer stem, and it bent like a dream. Waiting for it to set nice and tight before I glue.


Thanks so very much for all the usefull tips and help guys and gals. I will be updating my sorry excuse for a progress post soon.

Chris.

Stencil
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Re: Steam Bending Stems

Post by Stencil » Sun May 26, 2013 8:54 am

I have good success with boiling. Birch and ash both respond well to a good soak and then boil. Ash will bend just with soaking depending on the radius (not radical). I talking about solid full dimensional wood not just strips.

alick burt
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Re: Steam Bending Stems

Post by alick burt » Thu Aug 15, 2013 3:33 pm

Hi folks
For me the best discovery I made when it comes to bending stems is that using Air dried timber as opposed to kiln dried is far easier to work with.On my most recent build I soaked air dried Ash strips for just an hour in cold water and then bent them over the forms with a paint stripping gun doing a dry run a strip at a time and then I did the glue up using PU adhesive (which actually likes a little residual moisture to help it cure) and left it to set overnight.The result was a pair of really good stems with very little spring back from the form shape.
Cheers
Alick :wink

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