Steam Bending a New Stem

[dawagoner]

I am rebuilding a 50's era wood canvas canoe.

I need to replace bot stems and have purchased ash stem stock but I am having trouble with the bending.

I have steamed the stems and bent them on a form but the wood splits at the last part of the bend.

The first stem (bottom one in the picture) was steamed for 1 hour 40 min at 215 degrees. The second one was steamed for 3 hours at 215 degrees. The wood seems pliable and bends easily however it splits at the very last.

Am I doing something wrong? Should the wood be cut differently?

Any suggestions would be appreciated.

 

[Larry Meyer]

If you are content with the shape of the stems (that is, you’ve gotten the curve right) in your shoes, I would make the best of what you’ve got by gluing those small splits back in place. You are going to be beveling the sides of the stems along the curve in any case. You’ve done a 99% successful job.

 

[Dan Miller]

(Thread moved to appropriate forum).

+1 what Larry said.

Also, your bending stock has a lot to do with it. Best is green lumber, second best is air-dried. Kiln-dried can be bent, but with a significantly higher failure rate. Best to soak overnight in fresh water for all bending stock.

Rule of thumb is one hour of steaming per inch of thickness. 3 hours is way too long to steam a stem. Steaming too long dries out your blank, and increases the failure rate.

 

[Cliff Ober]

View attachment 24699

...The wood seems pliable and bends easily however it splits at the very last.

Am I doing something wrong? Should the wood be cut differently?

A metal strap held tightly on the outside of the bend will help keep the wood from splintering/splitting.

Cliff

 

[Grandlaker]

I remember asking an old time canoe builder about bending stems. I asked him how long he soaked them and then how long he steamed them. He got a funny smirk on his face and said.
soak em till there wet steam them till they bend.

I like to soak my stems for 2 days. 40 min. to no longer than 1 hr. of steaming. Steaming will dehydrate your wood.
When I do stems I start with 5 or 6 and hope to get 2 or 3 good ones when I am done .

 

[Mark Adams]

Another thing no-one seems to have mentioned, is the use of a compression strap.

 

[Treewater]

I had the same problem recently with oak. Does changing the orientation of the grain help?

 

[Larry Meyer]

Just to explain my reasoning further.
1. I think the splits you’ve got can be successfully glued back in place.
2. To complete your stems, you still have yet to remove a lot of material. Something like 50% of the wood there you’re going to get rid of in beveling the sides and making notches for the ribs, etc. Your splits are on the outside curves, exactly where there is a lot of material still to be removed.
3. How big are your dimensions now, 1” by 1”? The curve parts are going to get even smaller. Your splits may even be now outside the area of what you need for a finished product stem.
4. In doing restorations, people who aim to save and reuse the old stems often slather them with a coat of epoxy, just to restore enough structural integrity to hold tacks and screws. Stems end up with a lot of holes in them. Never in the course of history have so many fasteners gone into so little wood.
5. I am not an expert at steam bending ash. A compression strap, more or less steaming, green wood vs. kiln dried, voodoo or prayer all might have made a difference. It looks like what you’ve got is a result of edge grain run-out. But what I see is a pretty good result for a first try. Your second try may be worse. If the curve is right (you have not had too much bounce back), then the battle is largely won.

 

[Dave Wermuth]

I also think you might be able to use those stems. I have a couple youtube videos on the matter. I broke the first 3 or 4 stems years ago. I haven't broken any since (about 25). http://www.youtube.com/watch?v=8jsd5HapWpE The video is not pro quality and just the raw video. the part two shows the bending. Part one, attached here, shows the preliminary stuff. Short homemade videos but you might find something useful. My youtube id is davidwermuth80

 

[Andre Cloutier]

Like Cliff said, use a thin metal strap held tightly over the face of the stem, I've not had one blow apart after soaking for 24 hours, though without the strap they try to, you can see them wanting to sometimes. Avoid the kiln dried where possible, but a good soaking goes a long way as the stock is only about an inch thick. Definitely dont over steam them, but those arent catastrophic failures so a strap will likely solve your problems.

 

[Lazy Jack]

I would laminate. Much easier, much lower failure rate, much less spring back, much stronger...just better overall IMO.
Unless your after The Experience of Steam Bending a Stem, I can't see any practical reason to do it that way.

 

[Cliff Ober]

I would laminate. Much easier, much lower failure rate, much less spring back, much stronger...just better overall IMO.
Unless your after The Experience of Steam Bending a Stem, I can't see any practical reason to do it that way.

Agreed; it's much less stressful way to go (in more ways than one ).

Cliff

 

[Jerry Fruetel]

No question, laminated stems work well, but are they compatible with the methods of traditional wood canvas canoe building/restoration? I'm sure there's no consensus, but personally I view steambent stems as a core component of a wood canvas canoe, especially a restoration.

 

[KAT]

I had exactly the same thing happen on a couple of ash stems I bent recently. I just glued them back together and finished shaping them. I figure they will be fine in the long run.

 

[Lazy Jack]

No question, laminated stems work well, but are they compatible with the methods of traditional wood canvas canoe building/restoration? I'm sure there's no consensus, but personally I view steambent stems as a core component of a wood canvas canoe, especially a restoration.

I don't disagree, but consider that lamination for canoe stems has precedent in many of the native american canoes - the predecessor of the WCC - so is a contemporaneous technology except that today we use glue instead of spruce root to bind the laminations together.

 

[davelanthier]

Another trick is to split the stem piece, except for the last 8" or so at the stem base, with a table saw. Soaks, steams and bends easy then. Once it is bent and left to cure the two pieces are glued back together. Now finish shaping the stem.