By the way, it may also be possible to use heat to bend wood permanently.
https://en.wikipedia.org/wiki/Heat_bending_of_wood
I have used Gorilla glue on a build similar to yours (but a smaller bookshelf). I used layers of 1/8" Baltic Birch and strap clamps, but it wasn't "bendy" so I had to cut kerfs. I used Gorilla glue because it expands enough to fill those gaps.
But Gorilla glue doesn't have a long open time so for a large speaker I would be nervous. I'm currently making a large curved speaker - quite the challenging curve. 1/8" hardboard kerfed layers. I used Loctite construction adhesive for the first layer to frame. Then I'm using Titebond II Extend glue for each additional layer. I'm pretty sure Titebond II is stronger than III, but III is more expensive because it is waterproof.
But Gorilla glue doesn't have a long open time so for a large speaker I would be nervous. I'm currently making a large curved speaker - quite the challenging curve. 1/8" hardboard kerfed layers. I used Loctite construction adhesive for the first layer to frame. Then I'm using Titebond II Extend glue for each additional layer. I'm pretty sure Titebond II is stronger than III, but III is more expensive because it is waterproof.
@newvirus2008 it's absolutely possible. That's a very old technique that is still in use but the open flame has been replaced by either a propane torch firing into the pipe or an electric resistive element placed inside the pipe. I tried a new approach simply using a heat gun and it worked unbelievably well. This bracelet was created while just playing around to see what was possible. Using a scrap of one of the hardest, most dense woods on the planet and expecting certain failure, I was shocked when, after exuding a bunch of oil (smelled fantastic), it began to bend. If you look up "fox style bender " you'll find it's a form for bending (typ) guitar sides using light bulbs for the heat source. 3 x 100w bulbs and a dimmer is all it takes but adding a line level thermostat is an improvement. It's the Easy Bake Oven bender. Scaling either technique to speaker panel size sounds daunting thoug
h.
Attachments
Any glue used will rely on the quality (and quantity) of glue holding the plies of the manufactured wood together, which will most likely be less than that of most glues us DIYers would use to bond the ply to itself or the frame.
Using more layers of thinner flexible ply will make life so much easier when forming the curves, and gluing up the curved panels on a former first eliminates so many problems of trying to do it on the speaker frame itself. Use slow PVA and a notched spreader used in a single direction to laminate the layers, and use a hard rubber or wooden roller to consolidate the layers - this helps the air escape. Ratchet straps and a sacrificial (unglued) cover piece and a polythene interlayer works well over a convex former. Dampen the ply with a mister before gluing if more working time is needed.
Remember to buy flexible ply with the curve in the right direction on the sheet too!
Using more layers of thinner flexible ply will make life so much easier when forming the curves, and gluing up the curved panels on a former first eliminates so many problems of trying to do it on the speaker frame itself. Use slow PVA and a notched spreader used in a single direction to laminate the layers, and use a hard rubber or wooden roller to consolidate the layers - this helps the air escape. Ratchet straps and a sacrificial (unglued) cover piece and a polythene interlayer works well over a convex former. Dampen the ply with a mister before gluing if more working time is needed.
Remember to buy flexible ply with the curve in the right direction on the sheet too!
Yeah, I didn't even want to try heat or steam bending. Sounded like a recipe for irregular bends across the full panel.
Also, for the non-bendy parts, I now fully understand the difference between nice 11-ply furniture grade baltic birch, and the lower quality 9-ply birch ply sold at Home Depot. I bought small piece of the HD ply to make a few more of the inner brace pieces. Definitely lighter, does not cut as smoothly. Luckily not a critical part of the build.
@jayme I agree. It works well and is widely used in production work with high pressure and uniform heating that would be hard to achieve as a diyer.
@MrKlinky 100% agree that a solud, positive bending form, multiple thinner plies with an unglued top-sheet to help distribute pressure is the most user friendly, consistent, repeatable method for most of us. With forms and jigs, I always remember the Abe Lincoln quote: give me 6 hours to chop down a tree and I'll spend 4 hours sharpening the axe.
@MrKlinky 100% agree that a solud, positive bending form, multiple thinner plies with an unglued top-sheet to help distribute pressure is the most user friendly, consistent, repeatable method for most of us. With forms and jigs, I always remember the Abe Lincoln quote: give me 6 hours to chop down a tree and I'll spend 4 hours sharpening the axe.
Thanks Dave. It's Lignum Vitae. The most fascinating, frustrating wood I've ever worked. The first nuclear sub used it for shaft bearings! Just south of you, across the strait, Edensaw sells "bearing grade" billets... by the pound!! Last time I looked, it was $35/lb if memory serves but that was several years ago. I'm running out there soon, so the betting pool is open. $50/lb???
With a higher specific gravity than water, that adds up fast. The frustrating part is it eats non-carbide saw blades and chisels for breakfast. Making one piece mallet heads and having to chisel it cross grain is like cutting stone. Scary sharp, Narex chisels that cut most things like butter required a complete regrind afterwards.
Adding:
In this part of the world, look for Pacific Dogwood. The trees are easy to mistake for Alder until you get to cutting. Impressively hard and was used for golf clubs at some point.
I had a dogwood in my front yard that died. Had to cut it down. Trunk was only about 8" around, but damn that was hard wood to cut through, especially since I only have a demolition saw with the long tree limb cutter blades. It was rock hard.
Don’t get me wrong, I am mostly not an advocate of that adhesive for much else, but I have had decent results in that application.
Many adhesives won’t stay wet long enough to apply it and get everything clamped up.
We had access to a cnc router for making the forms with lots of interlocking structure, but you can do it using carefully made jig saw profiles, or make a master template and finish the profiles using a router.
Many adhesives won’t stay wet long enough to apply it and get everything clamped up.
We had access to a cnc router for making the forms with lots of interlocking structure, but you can do it using carefully made jig saw profiles, or make a master template and finish the profiles using a router.
I have access to a cnc router for the first time but haven't learned the software yet. I need to get on that.
Taking as long as necessary to make one perfect template and routing copies is the hands-down best non cnc method out there. It's absolutely worth the $ to invest in high quality pattern bits like Amana, Whiteside etc.
Taking as long as necessary to make one perfect template and routing copies is the hands-down best non cnc method out there. It's absolutely worth the $ to invest in high quality pattern bits like Amana, Whiteside etc.