Bending Wood

[dave0]

I need to bend some gunwales for the Rob Roy I picked up. I already tried to clamp them into place and force them like I do on my 16' canoes but they are too short and I hear a lot of protesting from the wood. I am thinking about just soaking them in water for a day or so and then seeing if I can bend them to where I want them but am also thinking about making a steam box of some type, probably PVC piping. I have also heard about using an ammonia/water mix as well but not sure of that one. This is an area where I'm lacking any knowledge.

For reference it's ash with a rabbet at 6' 2-6" long by 3/4" or so.

I'd really like to avoid the steam box but will go that route to get this done if necessary.

Has anyone bent wood before and have some advice they would care to share?

dougd

 

[memaquay]

You might get away with soaking for a few days. I usually do both, soak and steam. I usually let it soak for three or four days. Having said that, I have never had to steam or soak any of my gunwales, even on the chum, which had a fair bit of upturn. I guess the shorter length might be the problem, although that would make it easier to steam.

 

[Canotrouge]

Soaking them for a few days and then hot water towels just before the instal!

 

[Alan Gage]

Laminating could be an option that would avoid soaking and steaming while also upping the chances of an entertaining story of how you handle three spring loaded strips of ash slathered with glue with one hand while trying to tighten a two handed clamp with the other.

Alan

 

[sweeper]

I've wrapped a towel around the area to be bent and pour boiling water on it, waited a couple minutes and bend it. It worked great even on a little 12' glass canoe I retrimed in oak

 

[Boatman53]

Easiest steaming ever is with a wall paper steamer an a piece of plastic or bag. Clamp the gunnel in place slip the bag over the end insert the steam hose into the bag and let it steam. In a half hour or so check it to see how flexible the piece is. If it's flexible just bend it into place and clamp it, with the bag still on or slid the bag off. Either way it is fast and no time or heat lost pulling a big long gunnel out of a box and trying to line everything up. A steamer will run less than $50 I think. Here is a photo using this method but I've got three planks in the bag, the steamer is the black and white box on the floor.

Jim

 

[Jim Dodd]

Here's a vid that is the same idea as Boatman 53's

I've never steamed wood, but this looks good to me.

Jim

 

[Robin]

I soak the area for a couple of days, then use towels and boiling water. On real big bends like an Old Town OCTA, I build a jig and use the steam box to get it ready for the bend, then bend it on the jig and leave it for a couple of days, then when removed from the jig, it might need some boiling water to make it fit just right.

 

[Mihun09]

Yea, what they said.

We soak at least 4 days and have done steaming on the boat with RV waste hose instead of plastic sleeving, we have done towels and boiling water with oak, we have done streaming and jigs, but we always soak. The issue you may have is the rabbet. The wood "may" want to twist in the direction of least resistance which is not how you want it to go. If it has been kiln dried it will be more stubborn. What they sell as Bending Ash is just Ash with a moisture content around 25%.

So get it screwed or clamped into place as far as you can go, then do one method to relax the wood and she should go where you need it. Take it slow, pull it up, clamp it or put a screw in, just a bit at a time. All is good.

 

[stripperguy]

I've used a length of 3" PVC and a wall paper steamer...45 minutes and the wood is like a noddle, but not for long! Be sure to have your fixturing and clamps ready.

 

[Boatman53]

Stripperguy that's why the bag on the boat idea is so nice. You can take your time as the wood will be in steam till the last clamp is in place.
Jim

 

[pblanc]

I have had reasonable success supporting the wood on sawhorses at both ends and suspending weight plates on loops of nylon webbing, then periodically soaking the wood by pouring hot water over it. The process can take several days, however.

 

[Fitz]

For gunwales, bag it baby, bag it!

 

[dave0]

Thanks for all the feedback. I picked up a PVC pipe today, 2"x10' and cut it down to 8'. I wanted to get a 3" pipe but low and behold they didn't have caps for that size at the big box store. I am going to soak the gunwales for a few days in this setup and then use the towel and hot water as mentioned. With the warm spell coming I am going to use G-Flex to fill all the old holes and then test drill new holes using some left over gunwales to see how close it comes to the lip of the cockpit, I had a disaster happen with another kevlar boat and don't want to repeat that. These new gunwales are thinner then the ones I mill out but I'm going with the rabbet so that's why the test run. I really entertained the idea of a steam box of some type but if hot water, a long soak, and towels can do it I'm all for that. One less thing to store as I have limited space right now. Once again, thank you all for the feedback, valuable info for future plans. I may be out of storage space but there is always one hull out there waiting for a fix.

dougd

 

[dave0]

Well, the wood has been soaking for 4 days now and I am going to take them out of the tube and see if they give a enough to make the bend. While comparing notes with Mr. McCrea the question of an unheated workshop and wet wood came into play. Before I go further I do have permission to bring the boat into the house for a few days but if I do bend the gunwales into place and clamp them will the water in the wood expand in these cold temps and damage the wood in my unheated workshop? Never done this before and I'm thinking I should have timed things for a better/warmer season to do this. Never said I was the sharpest knife in the drawer!!

 

[Alan Gage]

How cold does it get in your shop? I'm guessing you'll be fine.

Alan

 

[dave0]

Alan, It an unheated workshop that only heats up from the sun so it's as cold as the temps outside. One thought is to let the gunwales "dry" out a little in the house and then take them to the workshop and clamp them into place. I just don't know much about wood moisture and cold weather in this application. I'd prefer to take it to the workshop but can bring it in to warmth. Ya know I really need a new workshop!!!!

 

[Guest]

How cold does it get in your shop? I'm guessing you'll be fine.

I looked at the forecast for Doug’s overnight temps. In the teens for a few nights, with a low of minus 7F next week.

I have no idea what happens to ash soaked for 4 days at sub freezing temperatures. Would it dry if frozen, or worse, split?

At minus 7 I wouldn’t even be walking out to the shop to check.

 

[Boatman53]

No worries, it will be fine. What are the dimensions like 3/4" square or so? I've re ribbed a big cabin cruiser in one of those instant garages temps in the twenties while we are bending 1 1/4" square stock. Turn out the lights and go home, never had a problem. If you want a bit of piece of mind, after the bend take a heat gun or hair dryer to it while clamped in place. That will take some of the moisture away.

Jim

 

[dave0]

After 5 days of soaking the wood and a forecast for 40 degrees out I decided to go for bending these gunwales. In the wee hours of the morning it suddenly dawned on me that there was a much easier way of going about this then clamping them on the hull. Sometimes it works against one to over think the process! It came to me that I had the old gunwales I could as a template as they already have the bend I needed, being a frugal Yankee I tend not to throw out much which can make for a bit of a nightmare when cleaning out time comes. The only thing I really needed was a new top on one of my benches, 8' x 17" w. I just happened to have a piece of plywood that would fit the bill but wider then the original. I put that into place and then used the old gunwales to trace the arc/bend onto the wood.

I brought my the PVC pipe down with the soaking wood and literally had to tap the top cap off. To my dismay the wood had floated up so the last 3" or so were dry, oh yeah dumbass wood floats!, but being the very end I wasn't to concerned. My plan was to use screws to hold the gunwales in place for the bend knowing that they would mar the wood a hair but a little sanding would correct that. Starting at the middle I worked my way up both ends until I reached my lines that I had drawn by tracing the old gunwales. On the ends I pushed over that line as I thought maybe spring back of the wood could make a difference. I've not done this before so once again I'm making it up as I go along. I took the old gunwales and laid them out to compare and by Gawd they were almost perfect so I was satisfied with it.

During a dry fit on the hull these gunwales creaked like a SOB and I thought they break but this time they just bent without any protest. Sweet! After talking with Mr. McCrea, who knows as little about this as I do, the topic of wood drying and twisting came into play. I opted to use scrap pieces of wood to clamp down from the vertical to hold it flush so 8 clamps and 4 pieces of wood later I think I may have it where I want it. BTW, these are roughly 3/4" x 3/4" give or take. Gunwales from another hull.

Cut down the other set of gunwales and plan using a plug to hold the wood down for soaking so the entire length will get wet in the tube, let soak for 4-5 days, let the first set dry out a bit and see what happens. If I didn't have to deal with the rabbet cut I wouldn't even bother with this but hell it is a new learning curve.
I still have to plug all the old drill holes on the hull. From a test fit with scraps of the gunwale I know they will fit but it is going to close to the sheerline.

So now it's just a waiting game of drying out and the wood holding memory and keep the fingers crossed it works. Here's pics of what I did.


http://picasaweb.google.com/11565649...32/BendingWood