The Defiants - InDIYana 2019 Build

[wogg]

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

[KEtheredge87]

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!

[KEtheredge87]

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 ​​​​​​​

[tomzarbo]

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

[tom_s]

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

[KEtheredge87]

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!

[Nismoron]

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.

[4thtry]

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

[KEtheredge87]

That's awesome Bill 4thtry Thanks for sharing

[scottq]

Looking great Keith! You're handling the speed bumps with great control of jerk and jounce! 👍👍😁😁 Sent from my Pixel 2 XL using Tapatalk

[KEtheredge87]

Thanks for all the encouragement friends! Makes it much easier to keep rolling as often as I can.

Post #1 for tonight - Epoxy fix for cabinet A

I picked up some 30 minute epoxy today and used a heat gun during the mixing to reduce the viscosity. This method preserves the strength of the final joint at the expense of a reduced pot life, where adding acetone or something else will keep your pot life but reduce the strength of the final joint. Before I started mixing, I prepped the cabinet with some masking tape to contain the mess. Once I started the mix, I would stir for a few seconds, hit it with the heat gun on low... and repeat two or three times until the consistency was nice and runny. Then I poured it into the cracks...which didn't really work. The thinned epoxy still wanted to sit on top of the crack, so I used my popsicle stick ram-rod mixing stick once more to cram it all down where it belonged.

I mentioned in a previous post how adding heat shortens pot life for the epoxy by speeding up the chain reaction... well here's the proof! This mix of "30 minute epoxy" kicked within 5 minutes due to all the added heat. Everything left in my little mixing cup was hardened by the time I finished stuffing the epoxy into the crack. Science at work!

[KEtheredge87]

Post #2 for tonight - The Jankapotomus Router Jig

Most of my setup work appears a bit more "thought out" than this... but tonight it was all free-form design as I prepared for the curved top router cuts. This is definitely the most janky setup I've attempted, but the quality should be there.

The idea here is to let the router sled to ride on the curve while taking shallow cuts off the top. By setting my final depth equal to the top / front edge of the cabinet, I can use the plunge router turrets to take graduated steps down into the cabinet as I work from left to right taking passes and removing material. I used this same method on my Jedi Mind Trick translam subs to great effect in baltic birch plywood. In fact, the router sled is the same one I built for that project. I really don't need one this wide for The Defiants! Unfortunately, these cabinet tops are just MDF, so it the cut surface won't be nearly as pretty to look at, but that's what veneer is for!

I'll try to take some more video tomorrow when I make the curved router cuts. I need to use my plunge router one more time on cabinet A to flush cut those edges after the epoxy cures, but then I can swap bits and mount the plunge base on the router sled. It's gonna be a big day!

[Wolf]

I would definitely apply a layer of hardboard to the MDF top before veneer if possible. You won't have edge-creep this way.
Later,
Wolf

[KEtheredge87]

I would definitely apply a layer of hardboard to the MDF top before veneer if possible. You won't have edge-creep this way.
Later,
Wolf

Thanks Ben, I like that idea and should have enough HDF laying around to accomplish that after router cuts are finished. Can probably use some sandbags as clamps on that kind of surface to distribute the pressure. I'll think on it more as I get there!

[KEtheredge87]

Hey Guys - good progress on cabinet A this morning, followed by a delay of game!

I got the flush trim completed after the epoxy fix, and flush sanded the rear and front panels. I didn't mention that much before, so on the front panels I also took the 60 grit sanding board and gave it some attention. The HDF edges of the front were ever so slightly angled away from the front face due to the way the router was sitting on the curved side for each trim. It wasn't bad to begin with... but this little detail will help with the final fit and finish later. Now the front faces of each cabinet are more equal... or planar... maybe I should just say they're flatter than when I started!

After the flush trim was done, I could convert my router so I turned attention to a brief cleanup and prep of the router sled for curved top cutting. I quickly realized that my bit depth was not sufficient to make this cut safely, so I ran off to the interwebs to rush deliver an MLCS 1/2" router collet extension to give me enough added length. It should arrive tomorrow.

For now, my pictures show WHAT ** NOT ** TO DO with router bits... which is chuck them up with barely any shank gripped in the collet.
That's how bits suddenly fly out and (best case scenario) turn your pants brown...

I would not make the cut like this. Only showing this for the sake of the photo and explanation of how far off I am.

With that out of the way... A little more thought revealed the difference between this curved top and my Jedi Mind Tricks subwoofer tops. The subwoofers had material steps on the outside of the cabinet too! In the case of The Defiants, there's no external stair step, which was a conscious choice to make layering and trimming the sides easier. The consequence of that choice is that there's also a lot more material to remove on the outside. That required me to keep my template curve higher from the top surface than I was able to do with the subwoofers. If I had put the template lower on the Defiants, the back side of the sled would be crashing into the cabinet material as it tried to slide down the curve.

Guess I'll pick this back up tomorrow and work on other stuff in the meantime!