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| MDF radius dish- repair or scrap? http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14733 |
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| Author: | AndrewGribble [ Thu Nov 29, 2007 1:28 am ] |
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Recently I have acquired a 15' MDF dish made by LMI from a friend who has not used it for a few years. This dish is 3/4" MDF and doesn't exactly lay flat in in my go deck. I think it may be salvagable once glued to a piece of 3/4" Baltic birch. I plan on checking it with a 15' radius gauge if I do indeed laminate it. Any thoughts on this? Does anyone else out there laminate new dishes for stabililty reasons? I have recently received a 30' Extira MDF dish from Tracy and am wondering if it might be a good idea to glue that one up as well while I'm at it. Thanks. |
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| Author: | Brock Poling [ Thu Nov 29, 2007 1:36 am ] |
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Yeah I would glue them up to a piece of FLAT high quality plywood. Honestly though, I have a couple dishes that don't lay quite flat and I just clamp them down in my go bar deck and they are fine. I have a radius template I check them against and once clamped up they are perfect. I wouldn't scrap it. |
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| Author: | AndrewGribble [ Thu Nov 29, 2007 2:17 am ] |
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[QUOTE=Brock Poling] Thanks Brock, would you recommend something other than the 3/4" BB? I would think the extra weight of the birch laminated to the dish may make it easier to sand the radius into the back too. |
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| Author: | WaddyThomson [ Thu Nov 29, 2007 2:20 am ] |
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As I recall, a lot of them come as laminated dishes, don't they? Either 2 thicknesses of MDF or laminated to BB Ply. |
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| Author: | Mike Mahar [ Thu Nov 29, 2007 2:23 am ] |
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The first thing I do when I get a new dish is to glue another 3/4" flat dish to the back. I've had the LMI dishes be taco chips when I receive them and the flatten out nicely with the backer board. |
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| Author: | Bob Long [ Thu Nov 29, 2007 2:53 am ] |
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Hey Andrew... I have mine laminated with MDF, but I put a piece of MDF 20" in diameter between the dished board and the backing board. That makes a good place for clamping and makes them much easier to pick up and handle. Also, it gives you a steering wheel to hang on to when you sand rims, your fingers are not in the line of fire and hanging on to sandpaper. long. |
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| Author: | Shane Neifer [ Thu Nov 29, 2007 2:59 am ] |
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The dishes I offer are indeed two layers of 3/4" MDF laminated together and then I apply two coats of diamond coat water based varathane. I actually store them in our cold room and they stay absolutely flat. I actually laminate them prior to carving the radius but I think that laminating them after the fact will work also, just be sure that when you laminate it that you have your dish and new substrate both clamped to something solid and flat. What ever condition your dish is in when glued will likely remain. Good luck Shane |
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| Author: | AndrewGribble [ Thu Nov 29, 2007 4:05 am ] |
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Thanks for the tips fellers... Bob that is a great idea! Upon first read I thought you glued a dish with a 20" (20') radius on back. After scratching my head for a few moments the lightbulb came on. Yeah, after banging up my hands and sanding a few layers of skin off the 'steering wheel' method seems like a great set up. Thanks everyone for the great ideas in this thread and all the others. Much obliged! |
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| Author: | FishtownMike [ Thu Nov 29, 2007 6:55 am ] |
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Most sellers recomend that you attach the mdf dishes to a base like plywood or something else. Mdf is porious like regular wood and can warp and bend. |
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| Author: | Blanchard [ Thu Nov 29, 2007 7:21 am ] |
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I think those dishes go out of flat when they are made. MDF has higher density on the surfaces than it does in the middle. At full thickness, the two surfaces "balance " each other and the sheet stays flat. When the surface is cut off of one side, the dish goes out of balance and cups to the side that was cut. It doesn't really have anything to do with moisture. Gluing them to something stiff, such as ply wood or particle board, really helps. When I made my dishes, I glued a layer of MDF to two layers of 3/4" particle board, then I cut the dish into the MDF. They weigh a ton, but they hold their shape really well. The extra weight does make sanding the rim easier and faster. So, Andrew, glue them to a backing and they will be fine. Mark |
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