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Malahini Chine bending

Posted: Sun Mar 11, 2018 10:02 am
by footer
Im having a problem bending my mahogany Chinese. Have broken 4 boards trying. One I even steam bent.
I did read something about kiln dried boards are difficult steam bend.
Is there something I'm missing?
The chinesI have in place seem to be holding, but I heard some slight cracking doing it.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 10:18 am
by neel thompson
I have had good luck with "cold soaking". I got a long piece of pvc pipe and glued a cap on one end. Then prop the open end up a little, stick the boards in and fill it with cold water. Let the boards soak for about 24 hours. Remove them and clamp them in place on the hull (no rush here, unlike steam bending). Let them dry for a day or so and then unclamp them and glue them to the frames. They will hold enough of a set to make them easy to bend in place. Make sure they are dry before gluing. I have never steam bent anything. Also, you don't really have to soak the whole board, just the part you want to bend. It works for me......

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 10:28 am
by obd
I went with triple laminations glued on one layer at a time. The sapele bent into position effortlessly. Just make sure your first lam follows a nice fair curve.
Bob

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 10:30 am
by Mark-NJ
That picture of the split wood....is that one, thick piece? If so, that's at least some of your problem.

You'd be far better off to laminate several thinner pieces. My chines were 2 pieces of 5/8" thick.......put on the first one, then walk the second one over top, with a lot of glue in between. My shears were 3 pieces of 1/2". (whoops! OBD beat me to it!)

And, yes, kiln-dried wood doesn't react to steaming the same way green wood does. Kiln drying hardens the lignin, and there's not really any returning. Wetting helps, but that "floppy, soft, do-what-you-want-wth-it" steam result simply isn't going to happen with KD wood.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 10:32 am
by vupilot
Yep, you don't need to do them in one full thickness. You can apply them in two lamination half the thickness. This makes it much easier. Also, try bending them a little then letting sit overnight, then bend some more. Take a couple days to do it, each day it will bend further, easier. You can wrap Chine in towel and pour boiling water over towel for a little extra help.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 11:38 am
by Mark-NJ
I did the "towel + boiling water" thing, too. It helped a lot. Not nearly as effective as steaming green wood, but with KD it definitely offers some strain relief.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 11:53 am
by hoodman
You'll get it eventually. And you'll be able to use the scraps later on in the build.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 1:02 pm
by PeterG
From your photo, part of the problem too, may be the wood grain direction. Flat sawn wood with the growth rings parallel to the wide face will tend to split when bent around the frames. Quarter sawn wood with the growth rings perpendicular to the wide face will be less likely to split. Laminated chines may seem to be more work with the extra layers but it's definitely worth it to avoid the splits.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 1:13 pm
by obd
One other comment with lams. Other than maybe one screw to hold in place at the stem/chine blocking, I would only epoxy to frames until all laminations glued in place. Then you can go back and drive a single screw through all your layers and into each frame.

Re: Malahini Chine bending

Posted: Sun Mar 11, 2018 1:15 pm
by Bill Edmundson
footer

You're not alone. Most of us have heard the dreaded CRACK :!:

Bill

Re: Malahini Chine bending

Posted: Thu Mar 15, 2018 3:36 am
by footer
Thanks for all your input. The boards had several very small knots through them and that was where they were breaking. I only had three Mahogany boards and they all had knots in them. So, I decided to go back to my supplier and got a 1x10x16' white oak with perfectly straight grain and ripped and planed it.
I heard soaking kiln dried wood in water with fabric softener in it for 7 days before steaming will help. Well, I wasn't waiting 7 days, so I sped up the process and used a little softener in my steaming water and steamed them for three hours. I won't say the softener or even the steaming helped much in the bending, other than it did keep most of it's form when I pulled it back off. :)
Ultimately, I was able to make the bend with the white oak and had no signs (or sounds) of cracking and I feel very secure in the thought that its not going to break now.
Thanks again you guys.
I did steam my Mahogany sheer's and they bent beautifully, but they were thinner boards. (They are laying on top there in the picture).

Re: Malahini Chine bending

Posted: Thu Mar 15, 2018 5:53 am
by Bill Edmundson
Footer

Nice recovery! :)

Bill

Re: Malahini Chine bending

Posted: Thu Mar 15, 2018 12:02 pm
by PeterG
Nicely done! Great job with those chines (and sheers). Sweet looking lines too.
I am looking forward to assembling my Malahini this spring, right now it's an enormous stack of pre-fabbed parts. I made my chines and sheers with African mahogany and noticed they have a few pinhole knots too, thankfully not in areas that have a lot of bend. Will need to keep an eye on those areas.
As always, feel free to ask questions, post photos and have fun!

Re: Malahini Chine bending

Posted: Mon Jul 23, 2018 5:43 pm
by Shelboss
I am using Khaya mahogany and have read that it is dried without excessive heat so the lignan that bonds to the cellulose in the wood can be softened. It takes steam to do this, about 1 hour per inch of thickness. I watched a video of a shipwright who used polyethylene sleeving to steam the pieces he was bending. I ordered some 4"continuous sleeve poly, borrowed the wife's Shark steamer, taped the ends and pointed it down hill with a weep hole. Came back an hour later and quickly clamped the chine in place. It made easy work of the bend and twist that the Zip 1'" x 2" chine goes thru. I also sleep better knowing that I have relaxed some of the stress that would have normally been in the wood. Yes this can be done with boiling water and rags, but doesn't your wife need a steamer anyway? The shipwright made a steam generator out of a 5 gallon can on a propane burner with a lid and pipe off the top.

Re: Malahini Chine bending

Posted: Mon Jul 23, 2018 7:39 pm
by Bill Edmundson
Sounds like a still!

Bill