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| Getting Ripples Out of Sides http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=3096 |
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| Author: | Michael McBroom [ Sat Sep 03, 2005 9:16 am ] |
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My apologies in advance if this topic has been discussed recently. I just bent a pair of gorgeous cocobolo sides I bought from Bob C. They are well quartered, although they drift a bit off quarter toward one edge. I've learned the hard way to stay away from flatsawn stuff cuz it tends to ripple. I was hoping that wouldn't happen with these, but I got a bit of ripple on one of the sides. I use a heating blanked with a mold for side bending, but I don't use flashing or a mold "mirror" or anything else to apply even pressure along the entire length of the side. Works fine if I'm bending qs stuff. So, I set the side back on the mold, clamped it down, but added another caul at the area where the ripple was. I adjusted the caul while the blanket was on to maximize the area it would cover. This helped some, but I still have a bit of a ripple left. Haven't used my hot pipe in a long time, but now I'm thinking about setting it up and seeing if that won't make a difference. Anyway, just wondering what you guys do to get rid of ripples. To prevent them in the future, I plan to make a "mirror" to the mold and use it as a giant caul. The trick, though, is to make it oversize just enough to compensate for the thickness of the side material plus the thickness of the heating blanket. Best, Michael |
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| Author: | Tim McKnight [ Sat Sep 03, 2005 10:21 am ] |
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You can spritz them, throw em back in the Fox bender for a couple of cycles, or use a hot pipe or if they are thick enough true them up on a belt sander after the box is assembled. Lot's of choices. |
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| Author: | tippie53 [ Sat Sep 03, 2005 12:18 pm ] |
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If I am working wood that I feel may ripple I usually let them a little heavy .090 so I have more wood to work with. Also some times this is residual water and they may flatten. If you can flatten it and use a side support to help hold it . It is the nature of the beast. Some times you just get it john |
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| Author: | rich altieri [ Sun Sep 04, 2005 3:23 pm ] |
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I had this problem during recent build and was so severe I had to scrap the sides but not before experimenting a good bit. What I was able to do is using a household iron and my the flat side of my professional bending iron. Spritzed the wood, placed it against the bending iron and then ironed the outside with the house iron. It did fix them up pretty good but not good enough. Point is, if your ripples are not bad, this approach might work. Rich Altieri |
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| Author: | tippie53 [ Mon Sep 05, 2005 6:38 am ] |
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I have found that often too much water is the culprit of this. The object is to take just the right amount of water you need to help get the heat into the wood. Wood is "thermoplatic" which means it will bend with applied heat. You don't need much water. The only time I use alot of water is on high risk woods. ALso if the quarter on the side is very good this usually ins't a problem. More often than not is when there is some flat sawn or more off quareted wood in the set that can cause uneven bending and shrinking. Next time use less water and more heat. Also keep the sides in the bender will cool . Wood being a natural substance it sometimes will do what it wants reguardless of what you want it to do john hall |
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| Author: | Michael McBroom [ Mon Sep 05, 2005 10:05 am ] |
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John, Just for the sake of completeness, let me add that I lightly spritzed the sides, then wiped them down with a damp rag. I don't believe they got too much water. When bending them over the mold, I could see the evaporation line following the wood as it came in contact with the blanket. I really don't think they got too much water. I also let the sides cool completely before putting them through a second heat cycle, and then let them cool completely again before removing them from the mold. You mentioned that this can happen if the sides are not well quartered. As I mentioned in the original post, they do drift off-quarter -- maybe for about 25% of the width or so, and this is where the ripple occurred. I am reasonably convinced that it is this off-quarter drift that caused the slight rippling. Fortunately I am noticing that after taking the side out of the mold, it has "relaxed" some, and most of the ripple has disappeared. I will likely be able to scrape down most of the high spots. I appreciate very much everyone's feedback on this. Best, Michael |
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