Steam bending surfactant

patrick corry

patrick corry

solo canoeist
I'm going to steam bend mahogany outwales soon. Although the bending is not extreme in any way, I've been reading a bit about steam bending mahogany and some suggest that it's problematic at times. I believe my material is an African mahogany variety, probably Sapele. I read that adding a surfactant such as fabric softener to the pre-soak apparently reduces surface tension in the soaking water aiding in penetration of the fibers. Does anyone have experience with this, or comments pro or con? The material has been rabbeted for the plank/canvas overlap but left unshaped until clamped and dried to conform. Final shaping, tapering at the ends, etc will be completed with hand tools prior to final installation.

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Soak for at least one day. Use a bending strap. clamp the two outwales together so that don't bend at 45 degrees instead of 90 degrees. Good luck. Gil
 
Thanks all for your replies.

I think I failed to adequately articulate my premise. I'm content with the actual bending method which I've done successfully on several canoes; in this case I will be steaming on the canoe prior to final paint (it's currently filled/ no primer) using the bag method. The unknown for me is the addition of a surfactant; It's this detail about which I was asking. I will be pre-soaking the material for several days prior to bending day.

Surfactants in wood steaming, particularly for techniques like steam bending, are used to improve the penetration of water into the wood, breaking down the surface tension and allowing for better wetting. This enhances the bending process by helping the wood absorb more water, softening the lignin and making it more pliable.

Elaboration:
  • Surfactants and Water Penetration:
    Surfactants, like those found in many cleaning products or fabric softeners, work by reducing the surface tension of water. This allows the water to spread more easily across the surface of the wood and penetrate more deeply into its cells, even against the resistance of the wood's natural structure.
  • Steam Bending:
    In steam bending, the goal is to heat and soften the wood, making it pliable enough to be bent into a desired shape. Surfactants help achieve this by ensuring that the wood is thoroughly soaked with water, allowing the heat to effectively soften the lignin, which is a key component of wood that provides rigidity.
 
What works best for steam bending is just straight water, the additives make no difference. a two minute soaking of the wood is going to get the surface as wet as it can get.The wood does get wet but the steam is heating the wood. The steaming process is in fact lowering the moisture content of the wood. For the wood to absorb enough moisture, deep into the wood, to make any real difference, like if the wood was green, it needs to soak for many days if not weeks. Every Maine lobster boat building shop had a secret additive, from a wide range of cleaning products to kerosene, for their steamer and they all worked because they were still boiling water.
 
Patrick
As I'm sure you know steam bending relies on heat making the lignin in the wood soft enough to allow the cells to move against each other. Different types of timber are better or worse at this.
True mahoganies do steam bend without too much trouble, but Sapele is not a true mahogany. The wood data base describes it as not a true mahogany, not even generally accepted as mahogany, but with the acceptance of it being mahogany related.
In my experience, it does not like to steam bend!

Sam
 
Thank you Rollin; just what I wanted, an unvarnished (pun intended) point of view!

Sam, yes I am aware of the method by which the cells move. I really don't know what species I have but it is prepared and I'm confident it will work. As I said, the canoe (Rollin's Atkinson Traveler) requires relatively gentle curves- no outrageous upsweep at the stem. If it doesn't work well I'll try this stuff; it's 18' long so great for a 1-piece outwale. It's also a so-called Mahogany!
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I'm not sure how much of a difference it might make, but as I recall, the rails on our Traveller (spruce) were installed without using any steam. Just lots of clamps and a bit of patience were enough to get them installed. As long as that grain is not too squirrelly, you should be fine.
 
Patrick, Nice shop!. I likes seeing all the wood shavings and the work bench on wheels. The board looks like mahogany to me but whatever it is, you should be able to bend it on the Traveler without steaming. Of course the steaming will make it a little easier to bend and its always fun to have a successful steaming operation. You have to take your victory's where ever you find them!
 
Thanks Rollin! The shavings are from two fun paddle projects made from scraps in progress: Red Cedar for the beavertail, and red cedar/sycamore for the more radical looking one. I guess you'd call it a modified otter tail?
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Okay, I dunked the outwales into water for a 4-day soak, steaming them this weekend. I do recognize that these could be applied without steam, but an initial trial suggested that the last 30" or so would be fraught with potential trouble. Besides, my logic (for what that's worth) suggests that steamed outwales once dried in place won't, or are less likely, to harbor tension trying to get back to straight! Maybe they will rest easier on the hull once steamed and dried.

I soak in a closed aluminum gutter 20' long. Just seal up the two end caps and pour in 5 gallons of water. I'll probably use that water for the steamer since it's already up in the barn.

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Weighed down with two plastic coated dumbbells.
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The water will help for sure and should SET the wood when dried after a couple days. Certainly won't hurt! I use the gutter as well. Generally, I soak for 48 hours before bending using the bag method. I have some rail caps soaking for a Thursday steam currently.

Zack
 
at the first time to bending in 2015 on my alu canoe with fir tree , so I try the same thing from mahogany last year ... mahogany from old stairs ramps too short ... sawed in two ,planed , scarfed , glued ... I begin by the middle , half and half , 8 times in a row
my aluminium chymney is not fixed as you can see , so a cork with a wet laundry and a steam wallpaper stripper , and you progess with temporary screw
sorry no picture from this second renovation , but very easy , with gloves of course , you work , and the steam work with you
I hope you understand how I do ... and you can use the tube for bending with an helping wood pole who do the third hand as you can see
 

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Pardonnez moi, mon Francais est limite!

So many screws penetrating the bottom for the outer skid rails and inner strips! Does your canoe leak? Certainly a unique canoe, at least from my experience.
 
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