Optimizing Hook Angles for Hanging Sound Absorbing Panels from a Ceiling

[PSuran]

Hello! I have a pretty basic question I think, and I hope you smart people can help :)

I'm hanging some sound absorbing panels from a celing, they look like this -> https://www.dropbox.com/s/3assll5b1wbj8b6/2017-06-26 21.50.21.jpg?dl=0

1.2m x 0,6m, around 7 kg heavy, light wooden frame, mineral wool inside.

I'll screw in little hooks to each corner of the frame (4 hooks), and then hang the frame parallel to the ceiling (they will hang around 30 cm away from it). On the ceiling there are some wooden beams to which I will also screw hooks, and connect them with a chain to hooks on the corners of my panels.

The "problem" is that the distance between the ceiling beams is more than the width of the panel, which means that the chains will be at an angle. A bit hard for me to explain... Here's how it will look like -> https://www.dropbox.com/s/odbdi0ckoy3k7ei/2017-06-26 21.50.05.jpg?dl=0 . There's a beam on both sides of the panel obviously.

My question is... How to ANGLE the hooks so that there's least stress on the weakest parameter, which is the wooden frame I think... Should hook screws be perpendicular to the frame / ceiling (as they are in picture), or should I angle the screw hooks one towards the other, so that they follow the direction of the connecting chain?

My intuition is that if they are perpendicular to the wall / frame, then there's more stress on the part of the screw just outside of the wooden frame, so the screw might brake, but if the screws are screwed in at an angle (following the direction of the connecting chain), then there's more "stress" on the wood ... Is this correct?

Suggestions?

Thank you!

p.s. - I apologize if this is too basic :)

 

[bestudy]

Wood is made by several "layers", as you can see from the cutted section of the beam. More wood layers the screw pierces, more it will grips to the wood. If you screw the hooks at a angle the risks are that the screw pierces few layers or that it drills wood between layers, in which case wood is more likely to break. The fact that screw might break depends on how much the panel weighs and how many hooks you are going to screw.

 

[PSuran]

Thanks for the answer. So basically, it's best to screw the hooks as I have them in the picture above, and use "tough" screws?

 

[fresh_42]

Thanks for the answer. So basically, it's best to screw the hooks as I have them in the picture above, and use "tough" screws?

It might be necessary to use a kind of metal plugs, that spread once they are in the hollow space above the wood, because otherwise you risk that you screws don't carry the weight and fall off. It depends on the density and thickness of the wood the ceiling is made of. It could rip apart and no longer support your screws.

 

[PSuran]

It might be necessary to use a kind of metal plugs, that spread once they are in the hollow space above the wood, because otherwise you risk that you screws don't carry the weight and fall off. It depends on the density and thickness of the wood the ceiling is made of. It could rip apart and no longer support your screws.

Wood the ceiling beams are made of is very dense. Acoustic panel frames wood is a bit less dense.. Plus there's no hollow space above the wood. The screws will be completely in both the ceiling beam wood, and frame wood. Also, each screw will have to support around 2 kg, I guess that's not a lot.

I was just thinking there's an optimal angle for the screws inside the wood...

 

[fresh_42]

I was just thinking there's an optimal angle for the screws inside the wood...

2 kg should be without problems. But will it remain 2 kg throughout its lifetime? In general, it's always better to have an angle different from 90° with a long screw. But haven't you said, there is mineral wool above the ceiling panels? That is basically the same as a hollow space, regarding the forces, since it won't support the screws.

 

[berkeman]

But haven't you said, there is mineral wool above the ceiling panels? That is basically the same as a hollow space, regarding the forces, since it won't support the screws.

Agreed. When I first read this:

On the ceiling there are some wooden beams to which I will also screw hooks, and connect them with a chain to hooks on the corners of my panels.

I thought he was screwing into the wooden ceiling joists above the ceiling. But then in his picture:

Here's how it will look like -> https://www.dropbox.com/s/odbdi0ckoy3k7ei/2017-06-26 21.50.05.jpg?dl=0 .

it looks like he is trying to run his own beams under the ceiling. @PSuran -- What structure is above the ceiling? Can you find the ceiling joists and drive screws into them from below the ceiling? Do you know how to use a "Stud Finder" tool?

http://thesweethome.com/wp-content/uploads/sites/3/2013/10/06-stud-finder-prosensor-710-630.jpg

 

[sophiecentaur]

Something very relevant to this is the nature of the 'beams' above the ceiling. Are they floor joists, supporting a floor above or are they just ceiling joists, supporting a plasterboard ceiling? IF they are floor joists then you could expect them to support a grand piano !. If not, the possible load would be quite a bit less - as people who try to store things in their loft space often find.

On a totally practical level, as long as you can locate the joists accurately and put the screws into the middle 1/3 of their width, you shouldn't have many problems. If you do what I always do, you will use twice as many fixings as anyone sensible would and you can fit and forget your panels. The angle of the suspension wires is really not critical if you use more than the minimum number of screws. A bit of shear force will reduce the risk of a screw being pulled out but, hey, you won't be hanging yourself on those hooks.

From your information, it should be a simple task. With two screw eyes or hooks on each edge of the panel frame (5mm screws) and picture wire taken to similar screw eyes in the joists, you should have no problems. If that feels too flimsy and the joists are not floor joists, the battens (far more chunky in your picture than needed) would easily stop the joists from sagging if screwed tightly to the joists with several screws. But that could look a bit overkill.

You should consider how heavy light fittings are fixed in your average house. A glass bowl and metal chain etc would easily be two kilos and it's common to use just three skimpy screws - sometimes hung on a square pad just behind the plasterboard (not in my house though!).

PS it's easier to see pictures in a post if you put them directly into the post. I drag and drop.

 

[PSuran]

Thanks for helping everyone!

But haven't you said, there is mineral wool above the ceiling panels? That is basically the same as a hollow space, regarding the forces, since it won't support the screws.

Sorry, I explained poorly. The mineral wool is inside the frames already. The end result should look something like this (one panel 8 kg):

it looks like he is trying to run his own beams under the ceiling. [

Exactly! The beams are not attached to the ceiling at all, because the ceiling looked suspicious. Beams are attached to side walls of the room (only 3,5 meters across). They are attached properly (concrete walls), and I have no worries that they will hold, I think I could hang a horse from those beams. Just for testing, I put one of these beams on two bricks at each end, and tried jumping on the middle of the beam, it didn't budge, and I'm 95 kg light :). Max total weight per beam will be around 16 kg, and not all in one point (4 times half of one panel = 8 connections x 2kg). To clarify, I will have two panels hung between two beams, 8 panels total. This means I need 5 beams. Each panel is 8 kg. This means that the first and last beam will suspend only half of two panels (8kg total), while center 3 beams will each suspend 2 times half a panel from each side = 16 kg.

Also, I won't use wires but chains to hang the panels.

I was worried because the panels won't hang directly under the panel - the chains will be at an angle (as on my original photo). I guess I shouldn't worry too much, but better to ask than have something fall on my head :)

Thanks!

 

[sophiecentaur]

Also, I won't use wires but chains to hang the panels.

More attractive option. You need to use the screw depths to equalise the tensions to some degree. Not very critical but spreading the load is worthwhile if the suspension (ceiling) is not moving to spread the load itself.
It would probably look better if you could avoid having exposed batons / beams fixed to the ceiling so could you not check the dimensions of the existing joists? It may be worth while doing a rough estimate of the existing load on the ceiling support and compare it with the extra load you are planning. Plasterboard is quite heavy stuff. Have you access above or via a light fitting to look with a small mirror and lamp? If anyone ever walks on top of the joists and if they have not fallen through, your few kg wouldn't matter at all.
I just had a thought. If you don't want the panels to swing in a draught then multiple angles for the suspension would prevent that happening. (A triangle is a 'strong' shape)
We MUST have a photo of the result!

 

[PSuran]

More attractive option. You need to use the screw depths to equalise the tensions to some degree. Not very critical but spreading the load is worthwhile if the suspension (ceiling) is not moving to spread the load itself.

Keeping that in mind, thanks.

It would probably look better if you could avoid having exposed batons / beams fixed to the ceiling so could you not check the dimensions of the existing joists? It may be worth while doing a rough estimate of the existing load on the ceiling support and compare it with the extra load you are planning. Plasterboard is quite heavy stuff. Have you access above or via a light fitting to look with a small mirror and lamp? If anyone ever walks on top of the joists and if they have not fallen through, your few kg wouldn't matter at all.

I don't mind the looks of the exposed beams, I think it will look nice :) Also, fixing things directly to the ceiling is out of the question, we weren't able to figure out it's composition or find any beams. The room was a cooling compartment in an (old) butcher's shop, so standard rules don't apply. We think the ceiling might be a thick layer of some type of glue, with who knows what behind. The solution with the beams is much safer.

I just had a thought. If you don't want the panels to swing in a draught then multiple angles for the suspension would prevent that happening. (A triangle is a 'strong' shape)

Great, thanks for the idea, might even look cool! Please clarify the "triangle" part... I will have 4 suspension points, one in each corner of the frame...

We MUST have a photo of the result!

Definitely!

 

[sophiecentaur]

The room was a cooling compartment in an (old) butcher's shop

Ahh, so you will have some insulation already, works for sound too, to an extent.

Please clarify the "triangle" part..

Two chains from one point on the panel to two different points on the ceiling will prevent the panel moving from in the plane of the triangle. Triangles in structures make them strong. Think of guy ropes and skeleton framed towers. Without some 'triangles', (with just parallelograms) your panels can swing from side to side. You can use common points on the ceiling for attaching two panels to achieve what you need. (Or criss cross the chains above each panel - any arrangement will keep it steady and you are not dealing with hurricane force winds!)
How are your beams to be fixed to the wall? If you can get them to be a very snug fit across the width of the room with long L brackets, that would be strong. Those brackets will be supporting the greatest weight / stresses.

This is an example of what I meant.

 

[BillTre]

A different approach would be to suspend a layer of rods (or whatever) from the already present beams in such a way that the panels can be attached from points directly above them. It is an approach using an intermediary suspension system.

I know you like the idea of using a chain rather than wire, but chain suspension will only provide certain lengths (depending on the length of the links). Wires can be infinitely adjustable.

I also think @sophiecentaur's triangle idea is nice.

 

[jack action]

I might be too late, but how about the arrangement on the right instead of the one on the left:

Not only the angle is less pronounced (even less if you can put the hook on the outside on the bottom beam), but the screw are in shear instead of tension, which I think is better because there is a better chance the wooden threads strip by pulling on it than the metal hook breaks.

 

[PSuran]

Hello everyone, this project kind of got delayed, I finished it much much later than planned, so I forgot to post pictures here. It actually isn't 100 % finished, because the owner ran out of money for other necessary equipment.

I just remembered today when I wanted to post some other (unrelated) question. Not very nice of me, I know :)

Again, not finished, but here are some pictures (ceiling and side wall absorbers + two large poly-cylindrical diffusors, which double as low frequency absorbers).

And THANKS FOR THE HELP!

 

[sophiecentaur]

Hello everyone, this project kind of got delayed, I finished it much much later than planned, so I forgot to post pictures here. It actually isn't 100 % finished, because the owner ran out of money for other necessary equipment.

I just remembered today when I wanted to post some other (unrelated) question. Not very nice of me, I know :)

Again, not finished, but here are some pictures (ceiling and side wall absorbers + two large poly-cylindrical diffusors, which double as low frequency absorbers).

And THANKS FOR THE HELP!

Looks like a good job! Well done. Hope the acoustics are ok.

 

[PSuran]

Looks like a good job! Well done. Hope the acoustics are ok.

Yes, it's pretty good. A bit on the "dead" (less reverberant) side, but the standing waves and other low end mess is contained well. This space is intended for live "modern" music bands/performers, and considering it is a small space, less reverb is good - musicians like it (they would say such rooms sound "tight"), and it makes the recording easier to work with in post-production.

 

[sophiecentaur]

That’s good. If anyone doesn’t like it so dead, some electronic reverb is always available.