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Hi folks. I am preparing to veneer a curved surface (curved in one plane only); the problem is that there are depressions and shallow recesses that need to be filled before I can proceed. The substrate is both baltic birch and MDF. What products would permanently adhere so I do not have to worry about the veneer peeling away or peeling the filler away from the substrate? In auto circles the best analogy I can think of is Bondo. Thanks.
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Replies
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Hi Paul,
I'm confused; Baltic Birch
i and
MDF as the ground? Would you mind providing a few more specifics please?
Dano
*Bondo.
*Hi Paul,You can/should use Bondo to fill in major holes. But if the substrate is rough/uneven you should make a 2-ply (two sheets of veneer glued together with grain running perpendicular to each other). The two ply becomes an extra thick piece of veneer which prevents the unevenness of the substrate from telegraphing through.Hope this helps.Best,Kim Carleton GravesCarleton Woodworking
*Howdy Dano,It's hard to explain, but they are speaker cabinets (2'x2'x5') that in silhouette look like a .45 slug. They are 3/4 BB with 3/4 MDF laminated on the inside, so the outside is BB, except on the top, curved portion where I used the MDF to make literally hundreds of slats that look like the ribs of a boat (I had the MDF leftover). Yes, they weigh a ton, but the BB provides structural integrity (biscuits, screws and glue) and the MDF provides mass, ie, sound damping. They'll be finished in a cherry veneer with a solid cherry face glued to the front baffle (which has an additional MDF interior layer) to make a thickness of 3".
*Thank you very much, Kim. The veneer is 1/16" thick already, should I still double it?
*Hi Paul,I’m having a hard time envisioning what you’re doing. However if you’re going to use 1/16” thick material as veneer and not put a correspondingly thick layer on the inside, it seems to me that the structure will distroy itself fairly quickly. This is due to the outside veneer moving with nothing to restrain it on the other side of the panel. Also, you shouldn’t need to fill the particle board if it’s furniture grade and 1/16” veneer will cover up any irregularities in the substrait anyway. But 1/16” matererial is going to be hard to bend onto a curved surface. How are you going to do that? Why don’t you just use regular veneer (1/16” material is too thick to be called veneer in the modern sense)? So I guess I’m at a loss about what to tell you. Do you have a drawing or a picture of the piece? Best,Kim Carleton GravesCarleton Woodworking
*Paul,Well then that makes sense then, shape sorta like Bose? Sounds like they might have a fairly good sized base and woofers. I'd stay away from the bondo then. There are a number of epoxy fillers that are used for stitch and glue boat construction. Gougeon Brother's and System Three makes these fillers, though I think there might be a couple of others, these are the ones I'm familiar with. They will certainly penetrate and bond better. Good luck.Dano
*Thanks guys. Kim, the "veneer" is already cross-layered. There's a 1/32" face with a 1/32" thick layer at 90 degrees to it (also wood, not paper) beneath. Came that way from the shop, but $70 per 4X8 sheet.Dano, the drivers are two 15" woofers, two 15" passive radiators (one on each side), and in the center is a 17" x 17" horn which itself has four midrange drivers and a compression tweeter.
*Paul,Definitly go the epoxy filler route. Those dudes are gonna put out some vibes. Know how you can "feel" a kid's car with a trunk full of speakers coming from two blocks away? They pull up to next to you; yours and everyone elses car trim starts to hum. The kid's trim rattles, care to guess the cause? Ain't no bondo on MDF gonna stand up to that.Dano
*I'm gonna hit the local marine store tomorrow, see what I can find. Any recommendation for what glue I should use on the veneer? I've built furniture for years, just never veneered anything, so this is new ground for me. Do appreciate the advice!
*Paul,Assuming that you are addressing me, my first inclination is to recommend hide glue. The MDF would have to be sized first, though. What I am unsure of is how it would bond to the epoxy filler. Another, and perhaps more likely solution, would be an urea resin glue. Going this route will require pressure either by caul, press, or vacumn. Just out of curiosity, how many watts can be pushed through these babies, any who?Dano
*Dano,Well, they are very efficient, on the order of 95dB/1W/1m, which is far above your average speaker, so it does not take much to make them sing. 75wpc will give over 110dB easily, and because they are horn-loaded, there is exceptionally low distortion. Realistically you would go deaf long before you reached their max power capabilities. You can see the drivers at http://www.lambdacoustics.com though they're not readily available to the DIY crowd anymore. I have the Unity Horn and the TD15 woofers.As for the hide glue, what did you mean by sizing the MDF? I'd considered resin but the lack of a vacuum press or caul system gave me pause--now I remember why I have avoided veneer for so long! ;)
*One thought I had was to use band clamps; I have many around the shop, enough to have one every 6".
*Paul,They do sound (pun intended) like real kickers, thanks for the link.Sizing refers to "sealing" the MDF. Because it is so absorbant, the moisture in hide glue could cause problems due to swelling. Most will use thinned down glue to control this.Actually, cauls could be made by using 2 x 4s on edge, while I make mine from hardwood, if this is a one shot deal they would work if you have plenty of clamps. Even a rudimentary press could be made. The object is to have even pressure over the entire veneered surface. So, if you were to put a slight "rocker" on one edge of your cauls, and sandwich the veneered panel between to sheets of ply then clamp the sandwich together using you cauls, top and bottom, at their protruding ends you will in effect have created a "press" of sorts. The slightly crowned edges against the sandwich will distribute the pressure more evenly along the length of the caul, the sandwiches will serve to distribute the pressure perpendicular to the cauls as well.The more I think about this, the more I'm inclined to recommend this approach. Though my explanation may seem long, this really is the simpler and more efficient approach in my mind (it's my lack of writing skills that make it seem so "long winded). Especially in regard to sizing, hide glue, hammering it down and what not. There is also the hide glue/filler bonding issue as well. Since hide glue does rely on it's sucking properties, I'm still uncertain that it would work on epoxy, which I do feel is the best solution to that little problem.The problem I see with using band clamps is the pressure will be applied to the corners or edges rather than clamping and holding the veneer down to it's ground.I hope that this helps rather than cause confusion.Dano
*Thanks very much--I bought some marine epoxy filler, "Gray Marine Tex," and now am pondering the next step. I think I see what you're saying about the caul system; I'll let you know how it goes (if it goes!).
*Is there any chance that sandbags would apply sufficient pressure?
*Paul,Good man! Guess we were "over thinking" the problem, or at least I was. Totally slipped, my mind. Sand bags are great and is commonly used, especially on radius pieces, you will still need the top layer of the "sandwich" as long as the table used for the glue up is perfectly flat, if not then the bottom layer of the "sandwich" comes into play.Dano
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