Adventures in Curved plywood. - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips

Construction Tips Construction techniques and tips

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 10th June 2011, 04:15 PM   #1
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Default Adventures in Curved plywood.

I've been experimenting with curved plywood in an effort to build cabinets for my Tang Band W8-1772's ("Curvy Tangs"....haha ).

The goal is to end up with a 45L BR cabinet tuned to 45Hz or so. These cabs will end up on tubular stands with the port and binding posts on the bottom of the cabs.

So far I've tried 3/8" wiggle wood, which didn't work because un-kerfed it will not bend tight enough, and after kerfing halfway thru at 1/2" spacing, it cracked since the grain runs parallel to the bend.

Similar results with kerfing 3/4" MDF. I cut almost all the way through every 1/4" with an 1/8" width blade, and the board broke apart when making the tight rear bend. 18mm baltic birch took a couple of attempts; the trick is to kerf down to the last lam, and make sure the last lam grain is running perpendicular to the bend.

The two strips on the flat face are fixturing to keep the formers aligned in the same plane when wrapping and gluing the sheet around the sides.

The formers were fabbed by printing a full size paper template, then carefully jig-sawing out the first one, and using it as a template to make additional formers with a router and laminate trimmer bit. They are also 18 mm BB.

Next step is to laminate 1/8" poplar bending plywood on both faces (inside & outside) of the curved skin and then trim everything, including cutting the ends of the curved panel flush with the front baffle (which may be a bit of a challenge).
Attached Images
File Type: jpg curvy tang 1.jpg (194.8 KB, 692 views)
File Type: jpg curvy tang 2.jpg (189.5 KB, 671 views)
File Type: jpg curvy tang 3.jpg (167.2 KB, 666 views)
  Reply With Quote
Old 10th June 2011, 04:48 PM   #2
evanc is offline evanc  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New Jersey. About 1 hour from NYC and 1 min. from the beach
boywonder very cool project.
I'd skip the kerfed wood and use multiple layers of the bending ply. You could use formwood 2ply veneer for a nice outer skin.
Two-Ply Wood on Wood Veneer Stock List
The multiple layers of glue will make a very stiff final product.

Tight bond will work, But for the ultimate in glue I like
Vacuum Pressing Systems -- Veneer Glue
Its kind of nasty, and dries slowly, but will allow no creep when its dry.
good luck...Evan
__________________
http://www.evancotler.com
  Reply With Quote
Old 10th June 2011, 04:49 PM   #3
diyAudio Member
 
LineSource's Avatar
 
Join Date: Sep 2003
Location: SiliconValley
Your cabinet shape is becoming popular. I have seen stacked laminate or translam construction, as well as frame+bended board similar to your efforts on several commercial speakers. The old school construction discusses steaming thin plywood sheets and laminating them together around a frame.

Some speakers attempt to reduce cabinet edge diffraction, reduce speaker side-cone reflections, and taper the rear to reduce standing waves and rear cone reflections.

White Light speakers use an airfoil shape cabinet front in a effort to reduce diffraction effects. The bluge in front provides some space between the speaker side cone and cabinet walls. The tapering reduces standing waves. I wish I had the cabinet skills to build an MLTL for my Tang Band W8-1808 shaped like the White Light cabinet. I was surprised how much cleaner the bass from the MLTL was over past wide-and-shallow bass reflex cabinets.
Attached Images
File Type: jpg whitelight2.jpg (113.5 KB, 654 views)
File Type: jpg whitelight.jpg (37.6 KB, 623 views)
  Reply With Quote
Old 10th June 2011, 05:01 PM   #4
badman is offline badman  United States
diyAudio Member
 
badman's Avatar
 
Join Date: Sep 2003
Location: Sunny Tustin, SoCal
Hey, nice work! Are you putting a curvature on the front panel? That's where it's most critical for diffraction. I need to get down your way soonish.
__________________
I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!
  Reply With Quote
Old 10th June 2011, 05:03 PM   #5
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Quote:
Originally Posted by evanc View Post
I'd skip the kerfed wood and use multiple layers of the bending ply. You could use formwood 2ply veneer for a nice outer skin.
Evan: Thanks for the links! I've been considering layering up 1/8" bending plywood if the heavily kerfed BB didn't work out. My hope with the kerfed 18mm BB is that I'll end up with zillions of little 7/8" tall I-beams once I glue the thin bending plywood to the inside surface. At least on paper, it should be lighter and stiffer (or at least as stiff hopefully, I haven't done any bending calcs) than one thickness of 18mm BB. With a layer of 1/8" ply on both the inside and outside surfaces, the walls will be 1" thick.

This is presently an experiment so who knows what I'll end up with.......
  Reply With Quote
Old 10th June 2011, 05:19 PM   #6
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Quote:
Originally Posted by badman View Post
Hey, nice work! Are you putting a curvature on the front panel? That's where it's most critical for diffraction. I need to get down your way soonish.
The present plan is for a two layer (1 1/2" thick) front baffle with 3/4" roundovers everywhere. The baffle will be flat where the driver mounts, as curving the whole front would be another level of complexity for my tiny brain.

Since this is an experiment, feel free to stop by and make some saw dust (and some router dust)...I'm game to do more curving.

Yes, you'll have to stop by and check out my latest setup; TubeLab 300B and Half Changs........Send me a PM and let me know your availability.

Last edited by boywonder; 10th June 2011 at 05:29 PM.
  Reply With Quote
Old 13th June 2011, 07:33 PM   #7
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Quote:
Originally Posted by evanc View Post
You could use formwood 2ply veneer for a nice outer skin.
Two-Ply Wood on Wood Veneer Stock List
The multiple layers of glue will make a very stiff final product.
What advantages does the 2 ply veneer offer on curved surfaces compared to the conventional paper backed stuff?
  Reply With Quote
Old 15th June 2011, 09:11 PM   #8
evanc is offline evanc  United States
diyAudio Member
 
Join Date: Sep 2009
Location: New Jersey. About 1 hour from NYC and 1 min. from the beach
sorry i'm slow getting back.
The 2 ply veneer doesn't transmit whats under it as much. and bends well without cracking.
__________________
http://www.evancotler.com
  Reply With Quote
Old 27th June 2011, 08:58 PM   #9
chrisb is online now chrisb  Canada
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
Quote:
Originally Posted by evanc View Post
sorry i'm slow getting back.
The 2 ply veneer doesn't transmit whats under it as much. and bends well without cracking.

the downsides are restriction in attainable radius ( i.e larger ), and more exposed edge core than with the paper back
__________________
you don't really believe everything you think, do you?
community sites t-linespeakers.org, frugal-horn.com commercial site planet10-HiFi
  Reply With Quote
Old 27th June 2011, 10:25 PM   #10
diyAudio Member
 
boywonder's Avatar
 
Join Date: Jan 2008
Location: So.Cal.
Quote:
Originally Posted by chrisb View Post
the downsides are restriction in attainable radius ( i.e larger ), and more exposed edge core than with the paper back

The edges will be covered with solid ends and baffle....this experiment is continuing..had a few failures... but I'm slowly moving forward. I'll have more time to build these shortly.

I've been building some fixturing that will allow trimming the front edges on the tablesaw. The test piece shown is also twisted about 1/4' end to end, so I've make some fixturing for that also.

My present plan is to still use kerfed BB (1/2" presently), then contact cement 3 or 4 layers of 1/8" bending ply around the BB, then veneer.

I have a 4x8 sheet of paper backed quarter sawn cherry, so that will be first up once the design is up and tested.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
thin curved and braced plywood for cabinets kifeinthesink Multi-Way 14 10th December 2005 09:52 AM


New To Site? Need Help?

All times are GMT. The time now is 05:51 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2