Suggestions For Bending New Gunnels On Old Town Near The Ends.

I am installing new spruce gunnels on a 1925 HW Old Town. I know the original gunnels were shaped narrow at the ends to make the severe bend. Having trouble getting the spruce to bend. I have heated the ends with hot moist cloth. First attempt cracked. I do not want to cut down the top part of the hull at stems as someone suggested. I would like to keep the shape original. Any ideas out there on how to shape those gunnels to the original hull shape? Thanks Bob

 

To bend wood, it generally needs to be heated to about 200 degrees or more. The best way to do this is with steam, commonly using a steam box, but if you don't have a steam box (and perhaps even if you do) an easier way to steam something long and thin is by using a polyethylene tube. See:

http://forums.wcha.org/showthread.php?12999-STEAM-BENDING-IN-A-POLYETHYLENE-TUBE-part-1

 

Thank you

 

Bob,
Greggs suggestion is a good one but first you need to get moisture in the wood. Submerge the gunnel ends in water for a few days before attempting to bend the gunnels. The first 4 ft should do. They need lots of moisture to bend and hold shape.

 

Thank you. I appreciate your taking the time to share with me.

 

If you are steaming in a plastic bag tube, you can soak them in that. Just put a couple of folds and clip the end before filling with water.
Sam

 

Thank you Sam

 

Soak for a day or two. Stick the ends in a upright piece of pvc, with a cap on the bottom of course. Steam for no more then an hour. Clamp. Leave it a few inches long for leverage. Nice if you have a helper, humans work best.

 

Thank you. I appreciate your help!

 

David Satter, is see by you pictures that you bent the outwale right in place. I guess that I thought that it was necessary to bend to a form or a jig.
I'm preparing to steam the out wales for my OT 17' HW.
I've selected Ash and I'm hoping that turn out as nice as yours.
Brad

 

The best form or jig can be the canoe you are restoring -- it's the right size, right shape, and already made, and works for both inwales and outwales:



Pictures taken at gunwale bending demonstration, WCHA Assembly 2016

 

A couple years ago Craig Johnson had some of this plastic tubing. If he still has some for sale maybe he will chime in here. You still want to wet the wood prior to putting it into the tube. As is shown in Gregs photos, start in the middle and bend toward both ends. A lot of clamps and a couple friends makes this job easy. TM..

 

A question for those who have used the plastic bag method. What is the mill thickness of the plastic used. I tried that method on the in-wales of my project. The problem that I had was, the plastic couldn't take the steam heat. I figured that the plastic bag was not heavy enough. I'm going to try it again on the out-wales, this time I think I'm going to put 2 or even 3 ( one inside the other).

 

Fitz got the poly bag material we shared and used, so he may remember better than I, but I believe the stuff we used was about 3 mils thick. Very little strain needs to be placed on the poly tube -- the job should be set up with things cold -- placing the wood in the tube and clamping the center of the rail in place -- and once the wood is heated enough and flexible, it bends into place for clamping pretty easily, with the clamps going right over the tube. We had no problems with the tubing tearing, either at the Assembly demonstration or when we had each done it separately ourselves before then. The tubing does soften up and weaken substantially when heated -- while I think 1 or 2 mil material could be used, 3 or 4 mil (or even a bit heavier, I suppose) would certainly be better.

Once the entire rail is clamped in place, the tube can be stripped away one clamp at a time, reclamping after the tube is torn away -- we waited until things had cooled off. Alternatively, the tubing could be cut and stripped away while steam is still being fed, as a rail is clamped in place at the center of the canoe, then working toward an end -- as I did on my first tube-bending attempt. I fed the steam in from the bow or stern end instead of from the middle, and pulled the steam tube back out as I clamped from the center to the end -- see the pictures in the link in the second post above. But even proceeding this way, I now would keep the tube in place until the whole rail is clamped and things have cooled off. I think inserting steam in the middle of the rail run and then working to each end is better, as we did at the Assembly demonstration, but I think you need more steam than I had on my first attempt, when I used a steam wall-paper remover.

The clamps are best kept in place for a couple of days till things dry out, but I suppose that if you are in a rush, the rails could be fastened down almost right after they are cooled.

The plastic tubing is cheap enough that there is little sense in trying to save it. The only issue with the tubing's cost is that we have only found it available in fairly large quantities -- 1000 feet minimums or more -- even shared, a lifetime supply for an amateur -- but even if the cost cannot be shared, the cost is probably less than building a steam box from new materials.

 

I bought one of those 1000-foot rolls, which is 6 mil. I remember thinking it was cheaper than buying plywood for a long steam box. That works and doesn't melt. I used it for planks so I got the 6" wide stuff. I have "welded" seams with a heat gun. With care, the seams can be water-tight but for steaming, that doesn't matter as much. It's not that easy to see through it to make sure your part is placed exactly right.

I haven't seen any comments on this, but most glues aren't happy about being steamed. Titebond III is only rated to 150 degrees. So I would avoid gluing the scarf joint, or steaming an already-glued one.

I was going to make forms for the gunwales on my HW. I made forms for the stems and even the ribs. If I think I need a clamp somewhere, I just drill a big hole in the form. Not so easy on the canoe. I can make the form with a tighter radius to account for springback. But the curve is not as extreme as the stem, so a form might be extra work.

On my HW, I have about a 9 degree tumblehome, and the rabbet on the inside edge would be a lot easier to cut in advance on a table saw. I don't know how I'm going to incorporate that into a form yet.

 

It is possible in some cases to account for springback when using your canoe as a bending form.

These pictures show how a gunwale can be overbent at the ends to deal with expected vertical springback. What the pictures do not show as clearly is that this rail was overbent horizontally at the end as well -- the rail was bent a couple of inches past the centerline of the deck when steamed and then when cooling and drying.



On most canoes, I don’t think overbending the gunwales is necessary. Consider that when a canoe is first constructed on the building form, the gunwales are not overbent. In the pictures shown, I overbent largely as an experiment.

A stem would not be so easily bent using the canoe as a form, and overbending would be more difficult yet, even though there may be more reasons for overbending a replacement stem.

 

Thanks for the good info. As it turn out the Ash that I was able to get was only in 12' lengths. So I'll be using the Steam Box I built for the ribs. I'll need to splice it at midship. Not what I would have preferred.

 

Thank you all for the detailed information. Bob

 

While resorcinol is not the easiest glue to use, it is water proof and very strong and suitable for some difficult woods such as white oak. While I have no experience with using it in a steam-bent joint, it is supposed to be able to withstand boiling. I have used it a bit otherwise, and have been pleased with it, although I have not tried to use it in a steam-bent scarf -- but the written literature on it suggests that it would hold up under such use. Because the bend of a gunwale is least at the center of a canoe, the stress on a scarf at that point would be minimal.

If anyone wants to try steam-bending a scarfed resorcinol joint, we would all be interested in the outcome.

 

Thank you for the information.