It looks like a only a slight curve and pretty easy to me. Even dry a thin sheet of plywood bends into a compound curve easily. Just pick the end up by 2 corners. With it wet it looks pretty easy to me. Getting the joints perfect for the gloss finish will be more difficult than the curve on top.
Until you have made your first laminate, fiberglass seems very difficult.
Build the buck out of foam (preferably a foam that does not dissolve under fiberglass resin)(i.e., not expanded polystyrene (styrofoam)) Two-part expanding foam in a big glob to start with may be the ticket. Perhaps a cardboard blank and cover it with foam to not use a huge amount of foam.
Sculpt it. Yes it is a sculpture.
Lay up a mold. sand it. sand it. sand it. gelcoat or cover with release agent. Be sure to brace the outside.
make a single or double thickness lay-up on the finished mold to hold its shape and pop it free. This can be carbon fiber if you don't mind the extra effort/cost. You may want to put some rope in between these first 2 layers to help it hold its shape. NO BUBBLES allowed!
lay up the rest of the glass.
It REALLY isn't as hard as it seems. And the finished part is as good as your patience allows.
Build the buck out of foam (preferably a foam that does not dissolve under fiberglass resin)(i.e., not expanded polystyrene (styrofoam)) Two-part expanding foam in a big glob to start with may be the ticket. Perhaps a cardboard blank and cover it with foam to not use a huge amount of foam.
Sculpt it. Yes it is a sculpture.
Lay up a mold. sand it. sand it. sand it. gelcoat or cover with release agent. Be sure to brace the outside.
make a single or double thickness lay-up on the finished mold to hold its shape and pop it free. This can be carbon fiber if you don't mind the extra effort/cost. You may want to put some rope in between these first 2 layers to help it hold its shape. NO BUBBLES allowed!
lay up the rest of the glass.
It REALLY isn't as hard as it seems. And the finished part is as good as your patience allows.
More curved cabinets than you can throw a politician at
I've done most every curved cabinet that you can think of. But I cheat with a vacume pump and plastic bag. The simplest way to produce your top curve is to do the same as you plan on the sides. The difference is that you will have to plan a brace setup in 3D. Not as hard as it sounds. If you use 3mm MDF then you can force it to shape with bags of sand that you can purchase at a builders supplier and then return because you have not used them. You will need allot of weight to force a 3D curve at least 4 bags of sand. Once you have piece number one the next will be much easier. By the way there are speacial bending plywoods that are available. They have three layers two that are thicker and oriented on a thin central ( 1mm ) ply. The two outer plys are oriented perpendicular to the core veneer. It works very well. Any way hope this helps and if you need a brain to pick email works wonders.
Mark
I've done most every curved cabinet that you can think of. But I cheat with a vacume pump and plastic bag. The simplest way to produce your top curve is to do the same as you plan on the sides. The difference is that you will have to plan a brace setup in 3D. Not as hard as it sounds. If you use 3mm MDF then you can force it to shape with bags of sand that you can purchase at a builders supplier and then return because you have not used them. You will need allot of weight to force a 3D curve at least 4 bags of sand. Once you have piece number one the next will be much easier. By the way there are speacial bending plywoods that are available. They have three layers two that are thicker and oriented on a thin central ( 1mm ) ply. The two outer plys are oriented perpendicular to the core veneer. It works very well. Any way hope this helps and if you need a brain to pick email works wonders.
Mark
Wind Bags need not apply!!
A vacume pump simply removes air from a plastic bag. What happens when you remove enough air is that the atomospheric pressure @ around 14 psi starts to push down on things the way you want it to. Normally the atmospheric pressure is around us and it provides an even pressure all over. But remove the normal pressure that it provides on the interior of an object by applying a vacume and most objects will be compressed. You can use a pump bag, form, combination to bend laminate pieces of wood ply or laminate veneer or what ever on flat panels etc. There are web sites that purport to explain it all but I haven't seen a good one yet. There are some good books available though.
Mark
A vacume pump simply removes air from a plastic bag. What happens when you remove enough air is that the atomospheric pressure @ around 14 psi starts to push down on things the way you want it to. Normally the atmospheric pressure is around us and it provides an even pressure all over. But remove the normal pressure that it provides on the interior of an object by applying a vacume and most objects will be compressed. You can use a pump bag, form, combination to bend laminate pieces of wood ply or laminate veneer or what ever on flat panels etc. There are web sites that purport to explain it all but I haven't seen a good one yet. There are some good books available though.
Mark
I used three layers of plywood and a a very strong "matrix bracing".
I used polyurethane glue. It swells during drying so it fills all possible air pockets.
Getting a suffisient pressure by using screw clamps was more or less impossible so I used several screws to attach plywood. I tooks the screws out after the glue had dried. I put the screws in different place in every layer and the swelling glue filled all the holes so there was no downside using screws. I veneered the sides of the encluse by using contact glue.
http://www.dvdplaza.fi/forums/attachment.php?attachmentid=775
I used polyurethane glue. It swells during drying so it fills all possible air pockets.
Getting a suffisient pressure by using screw clamps was more or less impossible so I used several screws to attach plywood. I tooks the screws out after the glue had dried. I put the screws in different place in every layer and the swelling glue filled all the holes so there was no downside using screws. I veneered the sides of the encluse by using contact glue.
http://www.dvdplaza.fi/forums/attachment.php?attachmentid=775
I use 1/8'' baltic plywood on radii as small as five inches no problem and 1/4" on radii of twelve inches and up, so this box should take 1/4" easily. You just need to make internal bracing to screw it to ala boat or aircraft frame/skin contruction. Cylindrical walls are almost impervious to vibration, so even with a sub I suspect two layers of 1/4'' would suffice. Use only 3 equal thickness plies; plywood with thin veneers over a thicker core don't bend well.
HI,
I am not a wood worker, but have an idea that my be practicle for a sub enclosure.
I have thought that the properly shaped enclosure would help reduce many of the standing waves and resonances that effect the amount of distortion that are created by the flexing of the cabinet.
This type of design principle has been used by many speaker companies over the years, Sonus Faber comes to mind.
My thought is to cut several layers out of MDF then stacking them, possibly using different thickness'.
Make sure you cut several strategically aligned holes so dowels can be used to keep the stack aligned, or you could use threaded bolt material with washers and nuts at each end, a clamp so to speak.
You could easily cut each layer using a router and the proper jig, or a saber saw, what ever is available.
If you want to veneer the outside for looks, it could be done easier if you design all of the edges with a slight radius.
I am not sure how the cabinet material will effect the sound characteristics of the over all system and integration.
But, I do think that this design could be implimented by experimenting with different types of materials, like a quality plywood in place of the MDF, also different types of glue.
By adjusting the material thickness and interal shapes to deal with resonances could go a long way in obtaining the best cabinet.
A possible internal shape could be chosen, like a set wavy pattern similar to a sine wave, then alternating each stacked layer of material with the peaks 180 degrees out to help break up standing waves.
I am sure that there will be many factors to consider other than the cabinet materials.
Obviously using a CNC type of router would expand the posssibilites and reduce the labor involved, it would also remove some of the human imperfections.
That is my 2 cents.
I hope that at least this has gotten a few people to think along these lines and someone will chime in.
Good Luck
Norris Wilson
I am not a wood worker, but have an idea that my be practicle for a sub enclosure.
I have thought that the properly shaped enclosure would help reduce many of the standing waves and resonances that effect the amount of distortion that are created by the flexing of the cabinet.
This type of design principle has been used by many speaker companies over the years, Sonus Faber comes to mind.
My thought is to cut several layers out of MDF then stacking them, possibly using different thickness'.
Make sure you cut several strategically aligned holes so dowels can be used to keep the stack aligned, or you could use threaded bolt material with washers and nuts at each end, a clamp so to speak.
You could easily cut each layer using a router and the proper jig, or a saber saw, what ever is available.
If you want to veneer the outside for looks, it could be done easier if you design all of the edges with a slight radius.
I am not sure how the cabinet material will effect the sound characteristics of the over all system and integration.
But, I do think that this design could be implimented by experimenting with different types of materials, like a quality plywood in place of the MDF, also different types of glue.
By adjusting the material thickness and interal shapes to deal with resonances could go a long way in obtaining the best cabinet.
A possible internal shape could be chosen, like a set wavy pattern similar to a sine wave, then alternating each stacked layer of material with the peaks 180 degrees out to help break up standing waves.
I am sure that there will be many factors to consider other than the cabinet materials.
Obviously using a CNC type of router would expand the posssibilites and reduce the labor involved, it would also remove some of the human imperfections.
That is my 2 cents.
I hope that at least this has gotten a few people to think along these lines and someone will chime in.
Good Luck
Norris Wilson
Ok, there are a few directions I could take with this:
1. carving out of solid timber - I'll consider this an option if I'm not happy with what I find with other techniques.
2. fibreglass - I want to consider this more, although it does seem like more work and effort
3. CNC router - still interests me, although cost is an issue here and would like to find out more from anyone who knows about the process
4. bending thin layers of timber or something else over ribs - similar to aeroplane construction
5. cutting slices of 3/4" MDF to an accurate curve and sanding - transverse lamination - I think this is similar to how it would be done via cnc, except I might be able to achieve this with a bit more work at home
6. a hybrid laminating / carving - creating a simple curve by bending sheets over ribs, then laminating sheets together, then carving - not keen on this method
7. variation of 4 - make ribs and stretch a membrane over the ribs - which can be used as a mould to then pour in (insert name of substance here) - then apply epoxy resin over the membrane to form the hard outer layer - I especially like this idea, and have seen it used in car audio
1. carving out of solid timber - I'll consider this an option if I'm not happy with what I find with other techniques.
2. fibreglass - I want to consider this more, although it does seem like more work and effort
3. CNC router - still interests me, although cost is an issue here and would like to find out more from anyone who knows about the process
4. bending thin layers of timber or something else over ribs - similar to aeroplane construction
5. cutting slices of 3/4" MDF to an accurate curve and sanding - transverse lamination - I think this is similar to how it would be done via cnc, except I might be able to achieve this with a bit more work at home
6. a hybrid laminating / carving - creating a simple curve by bending sheets over ribs, then laminating sheets together, then carving - not keen on this method
7. variation of 4 - make ribs and stretch a membrane over the ribs - which can be used as a mould to then pour in (insert name of substance here) - then apply epoxy resin over the membrane to form the hard outer layer - I especially like this idea, and have seen it used in car audio
Stocker, pls excuse my ignorance as I'm not very familiar with fibreglass construction.
What is a buck?
Isn't it harder to make a mould than to actually do the fibreglass? The mould would have to be a concave compound curve, that sounds even harder. Or have I got it the wrong way? Should I in fact build an MDF box and use that as a mould and lay fibreglass on top of that and then add the curve and sculpt it? The problem I have with this is how to get it smooth.
...
Mark, I can't see how you can bend MDF or plywood to a compound curve without cuts! Surely you need cuts! Do you have any links to these vacuum bags, I'm trying to get my head around the concept and how you would use them.
...
Mark and Stocker ... do you guys have pics or websites? It sounds like you would have a lot of experience that would be of interest with diyers.
...
I'm going to look into fibreglass construction some more. This challenge has got my mind working!!! ... time for some more research ...
What is a buck?
Isn't it harder to make a mould than to actually do the fibreglass? The mould would have to be a concave compound curve, that sounds even harder. Or have I got it the wrong way? Should I in fact build an MDF box and use that as a mould and lay fibreglass on top of that and then add the curve and sculpt it? The problem I have with this is how to get it smooth.
...
Mark, I can't see how you can bend MDF or plywood to a compound curve without cuts! Surely you need cuts! Do you have any links to these vacuum bags, I'm trying to get my head around the concept and how you would use them.
...
Mark and Stocker ... do you guys have pics or websites? It sounds like you would have a lot of experience that would be of interest with diyers.
...
I'm going to look into fibreglass construction some more. This challenge has got my mind working!!! ... time for some more research ...
i reckon make a template for the bracing that the curve will follow, soften some wood, and screw to the bracing.
i think ply will be better for bending than mdf.
why not curve the top and bottom more, and the sides less, so u have a uniform shape behind the sub? might need a long spike on the back, but i reckon it would look good.
i think ply will be better for bending than mdf.
why not curve the top and bottom more, and the sides less, so u have a uniform shape behind the sub? might need a long spike on the back, but i reckon it would look good.
Re: have you tried plywood 3ply bond together
for the sub I haven't tried anything yet
I have been thinking about curving the bottom as well. Would only do this if I find a way that isn't over the top in tedium! No sense spending forever to impress the carpet.
This box will be very thick. I have in mind 30mm minimum for the sides and 36mm minimum for the flat parts (and possibly more). This is a sealed box which will have a linkwitz transform, and the size and shape is determined more by aesthetics than by volume required. It will be probably more than a cubic foot, but I want it thick and heavy as when you put a high xmax driver in a small box it can move. I've seen a small sub with the XLS jump off its feet literally (it had a downfiring passive which wasn't helping). It's also nice to knock on the walls of a speaker and for it to sound like solid timber rather than something hollow.
Daniel-A said:
for the sub I haven't tried anything yet
mvagusta said:
I have been thinking about curving the bottom as well. Would only do this if I find a way that isn't over the top in tedium! No sense spending forever to impress the carpet.
This box will be very thick. I have in mind 30mm minimum for the sides and 36mm minimum for the flat parts (and possibly more). This is a sealed box which will have a linkwitz transform, and the size and shape is determined more by aesthetics than by volume required. It will be probably more than a cubic foot, but I want it thick and heavy as when you put a high xmax driver in a small box it can move. I've seen a small sub with the XLS jump off its feet literally (it had a downfiring passive which wasn't helping). It's also nice to knock on the walls of a speaker and for it to sound like solid timber rather than something hollow.
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