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The Defiants - InDIYana 2019 Build

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  • 4thtry
    replied
    Keith,

    I know you are way too far along into your project at this point to start building a custom type clamping fixture, but since this is how I did my Kowaxial curves, I thought I would just mention my method and post a few photos just in case someone might want to try this. Hope you don't mind.

    Positives:

    1) The fixture eliminated any sliding of the panels as the clamping pressure was applied. The panels were forced into one, and only one, position by the fixture.

    2) No gaps appeared along the long length edges. The fixture and clamps forced a large, very even squeeze out of glue.

    3) After about 48 hours, the 3/4" thick 6 layer composite panels were rock solid.

    Negatives:

    1) I didn't make the fixture quite long enough, so I got slight gaps at the end of the fixture, which I quickly corrected with extra clamps and blocks of wood before the glue set. This problem can be corrected in any future curved builds by always making the fixture slightly longer than the panel that needs to be glued up.

    2) I can't remember exactly, but the fixture took me over a week to build. And another week or so prior to this to design it on paper.

    3) The fixture was made from large remnants left over from cutting the profile side panels. So if you don't have large remnants from cutting the sides, making a fixture would be very difficult.

    4) I could see impressions of the three fixture ribs on the curved side panels after painting. But no one else mentioned them, so I got away with this boo-boo.

    Keep up the good work!

    Bill

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  • Nismoron
    replied
    For the vacuum bagging process, has anyone tried PeelPly? My other hobby is rebuilding boats. It is used in the marine industry while vacuum bagging. It's kind of like the little clear layer on the pad of a baindaid. The breather material (in vacuum bagging) or the gauze (in the bandaid) soaks up the excess while the PeelPly separates the two and does not allow them to stick. It works well for epoxy and polyester resins. But I do not know if it would work for wood glue. I dont see why it wouldn't.

    Leave a comment:


  • KEtheredge87
    replied
    Originally posted by tom_s View Post
    Thanks for your build thread! I've been planning to take the plunge and build some curved cabinets and even have most of the materials ready to go in the shop. I sure didn't plan on 6 layers. Those will be some pretty stout boxes! I've been following along, getting inspired, hoping to learn from your progress - and most importantly learn how to fix the mistakes I know I'll make along the way.

    Looking forward to seeing more of your progress!

    Tom
    Thanks Tom. Just to be clear, there's nothing magic about 6 layers... its all about layering it up until the cabinet resonances are sufficiently damped out. In more technical terms, you're making a composite material and increasing the stiffness of the material with each layer. Higher stiffness = higher resonant frequency of the cabinet (knuckle test pitch goes up) = less reverberant contribution of the cabinet to the overall sound (remember... we want the cones to move, not the cabinet!)

    I'm targeting 3/4" thick walls, which means I need 6 layers of my 1/8" HDF material. I didn't do any engineering calculations to arrive at this. It just happens to be a decent thickness for damping those cabinet resonances, and matches the rest of my cabinet's MDF wall thicknesses. If I were really gung-ho, I could add even more layers... but I imagine we'd hit diminishing returns quite quickly after ~3/4" of curved cabinet material. These suckers are pretty darn heavy as they sit right now... I'll weigh them tonight and see where we're at!

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  • tom_s
    replied
    Thanks for your build thread! I've been planning to take the plunge and build some curved cabinets and even have most of the materials ready to go in the shop. I sure didn't plan on 6 layers. Those will be some pretty stout boxes! I've been following along, getting inspired, hoping to learn from your progress - and most importantly learn how to fix the mistakes I know I'll make along the way.

    Looking forward to seeing more of your progress!

    Tom

    Leave a comment:


  • tomzarbo
    replied
    Keith,

    I took a peek at the video you did, Short and to the point, good job. the sound of the 'plink' tells it all. I've never done 6 layers, that's gotta be pretty strong.

    I actually had a sort of weird experience with gluing up multiple laminations of this stuff this weekend. I'll explain a little more later. But something interesting happened that I wasn't expecting.

    Looking good, I have an idea of how I'd do the curved top... looking forward to seeing what you come up with.

    Tom

    Leave a comment:


  • KEtheredge87
    replied
    jhollander and Kevin K. - Thanks for the added documentation on vacuum bagging and strap clamps. Hopefully future folks reading this will see it and consider all their options. I actually did a fair bit of vacuum bagging in grad school working on carbon fiber composites, so that method is near and dear to my heart... just not my wallet! I didn't mind shooting through rolls of breather and bag materials when I wasn't the one paying for it all ​​​​​​​

    Leave a comment:


  • KEtheredge87
    replied
    Originally posted by wogg View Post
    I love your build threads Keith. I have no input, but am looking forward to seeing these in person.
    Thanks bud! I figure if I'm going to ramble on the internet, someone should at least get to benefit from it! Gotta keep pushing through this bit so I can tackle the next challenges. Curving the top is something I've only done once before, and creating the chamfered front baffle will be new territory completely. I'm excited and nervous about that work... which usually equates to lots of extra thinking time as I wing it through!

    Leave a comment:


  • wogg
    replied
    I love your build threads Keith. I have no input, but am looking forward to seeing these in person.

    Leave a comment:


  • Kevin K.
    replied
    I think the strap clamps would yield more consistent pressure throughout but as you pointed out, the ends would have to be protected from crushing. A scrap panel of 3/4" a little smaller in width than the front and rear panels would probably do the trick. Also thinking with the strap clamps, you'd see less of an issue with the panels sliding around since the pressure would be pulled down consistently on both ends. Not sure how often one would need a strap, maybe every 4"-6" or so? Start with a strap in the middle and work your way out would be my approach. Suspect I'll be building a pair of curved cabinets this next year, will report back with how it works out for me, good or bad.

    You're getting there man, hang tough.

    To clarify, vacuum bagging the panels would be better but that's an expensive approach (bag and pump) unless you plan on numerous cabinets.

    Leave a comment:


  • jhollander
    replied
    Vacuum bagging the HDF should be like veneer where the glue squeeze out is below the edge as the bag wraps the edge. I add tape on the edge to protect the already veneered side, that would probably not be required to protect the MDF frame. I would probably add some breather/ batting to capture the glue and protect my bag.

    Fibre Glast usually has their bagging film on sale. I'm going to try the thin composite bag for my next veneer project. I got about 3 uses from my $30ish diy vinyl bag.

    Leave a comment:


  • KEtheredge87
    replied
    Originally posted by a4eaudio View Post
    Keith, thanks for running into all these problems now, I'm about to start some curved cabinets this weekend.
    What do you think is causing the gaps? Do you just need more clamps, or something different like strap-clamps, or is it just the nature of the HDF?
    Glad to be of service ;) The more I practice with these glue-ups, I start to conclude that I am the problem causing those gaps. Warning: Engineering nerdery ahead...

    During each glue-up I've been fighting with the HDF to keep it from sliding backwards when I tighten the rear clamps against the angled wall. By adding those two front-to-back clamps, I'm trying to pull all the panels forward / counteract that backwards slide. That front-to-back clamping force is acting at 90 degrees to the front clamps that just want the panels to smash against the wall, so the HDF layers are the weak links caught in the middle. Without a solid glue line to support them in the shape that I want, they give way and flex a bit to help the whole system reach a force balance.

    For this build I decided going 1/2" larger than the cabinet walls on all sides would be sufficient overhang for the HDF during glue up. I did not anticipate the sliding issue though. While it may be more wasteful, next time I would make my front and rear overhang something like 1" or more to give myself more margin for sliding error. It all gets trimmed off anyway.

    On the number of clamps... I think the 5-6 harbor freight clamps I've used on the front and back is probably OK. Strap clamps would be good if I had a big spacer or something to keep the straps from crushing the overhang on the HDF layers. In my head I can see those HDF layers cracking or crumbling when the strap tightens around the corners on the front/rear. I could be overthinking that though...

    A better method would be something like vacuum bagging or having a bunch of special cauls that match the curved profile exactly. That would apply a pressure evenly across the whole HDF sheet rather than only on the edges. Of course proper vacuum bagging would be a glue squeeze-out nightmare. I don't know how you'd pull that off without having to clean all kinds of dried glue off your good surfaces between each layup.

    Hope those thoughts help you plan your own curved cabinet build!

    Leave a comment:


  • KEtheredge87
    replied
    Originally posted by Nismoron View Post
    Super interesting build. I'll be following. I'm thinking of building something very similar.

    Anyone have a link on the alleged video about building curved cabinets? I would love to see it.
    Thank you sir! Tom Zarbo has his videos on YouTube for curved cabinet construction. That's the method I've been following here. He's got 3 parts to the video, here's the link to part 1: https://youtu.be/Yeczz85R8tc

    As for Wolf's Nephila, He's a very active participant on these forums. I'd imagine you could send him a PM or just start your thread and tag him with the @ symbol to get his attention.

    Leave a comment:


  • a4eaudio
    replied
    Keith, thanks for running into all these problems now, I'm about to start some curved cabinets this weekend.
    What do you think is causing the gaps? Do you just need more clamps, or something different like strap-clamps, or is it just the nature of the HDF?

    Leave a comment:


  • Nismoron
    replied
    Super interesting build. I'll be following. I'm thinking of building something very similar.

    After a 20ish year hiatus from speaker building, I'm trying to decide whether to finish a previous build that I bought all of the parts for (but tweeters damaged in storage and are now NLA) or just buy a Wolf Nephila kit. The previous speaker was going to be constructed much like this except was a 40inch tall tower with a bit more curve to it. The widest part is about 1/3 way back from the baffle. But it is only sliiiiightly wider. I found the Nephila kit by accident and it really intrigues me. But I cant find much info on how it sounds.

    Anyone have a link on the alleged video about building curved cabinets? I would love to see it.

    Not trying to hi-jack with my comments. I'll actually be starting a thread about it soon. As soon as I do some more reading and thinking on it.

    Leave a comment:


  • KEtheredge87
    replied
    Tonight my speakers are teaching me more about patience.

    had hoped to finish the flush cut and sanding work on cabinet A, but I found two more gaps in the panel glue-ups. These are much smaller than the last one, at only 1.5 to 2.5" deep and ~3 inches wide. Some of the Titebond II glue also wasn't 100% set inside the cracks. My makeshift depth gauge hit the bottom of the voids with a squishy, not-quite-cured-yet feeling.

    The cracks are even smaller than before which is great... but difficult all the same. I expect my Devcon 5min epoxy will be too thick to cram into these cracks, even with the hot-tub treatment to pre-warm / reduce the viscosity of the resin and hardener. I also worry about working time with these smaller cracks, as any added heat accelerates the epoxy chain reaction and thus shortens the already small 5 minute window. I also considered a few drops of acetone to thin the mixture, but that also negatively impacts the holding strength of the finished epoxy, with the risk of it just getting rubbery instead of curing solid. Finally, I also thought of just putting more Titebond II down there, but that won't really be a strong joint, and glue is not meant to be a gap-filler!

    Ultimately, I think the best option will be to go buy some 30 minute epoxy tomorrow and heat that up to a pourable / wick-able consistency. Best to do it now before final flush trimming to cut down on added spot sanding later on.

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