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I referenced your data and formulas above, and I think I've got it figured out now - key part was understanding moment of intertia (had to find a slightly different formula due to rectangular shape), which is the only variable I need to change here when comparing different size beams. Have used...

No, it's a simple question, with a very definite answer, and worth asking because to rely on AI calculations (or my own calculations, not having any prior knowledge of structural engineering) would be risky seeing as this thing will right above my head! I did thank you for your "suspension...

Have started a new thread, as the plans and main questions have now changed (thanks to advice given in this thread!) Please feel free to close this thread. The new one is: https://www.diynot.com/diy/threads/advice-on-size-thickness-of-hollow-box-section-aluminium-beam.645962/

Apologies for starting another similar thread to the one about angle iron - but thanks to advice given in the previous one, the plan has significantly changed, and the main question is now different: I have determined hollow box section aluminium beams are what I need for this project, and the...

Here are some basic sketches of the new plans (batten arrangement, side view, and top view) now that the idea is to have the beams resting on wooden battens either side of the room (so as to eliminate the problem of deflection of the beams stressing any fixtures). Just need to figure out what...

Yes - the shelf idea! Was thinking it through last night: if the stress on the fixings due to deflection is the problem, how do I eliminate that? Solution I came up with is mount a 50x50mm batten on either wall, then use L brackets screwed into the top of the batten, perpendicular to wall, to...

Mattress foam won't do much for sound insulation. You really need something like rockwool or some type of fibreglass.

Tried a totally different AI - completely different answers again!! OK, lesson learnt there. Also found a bunch of different "deflection calculators" but nothing that seemed to both suit this scenario and that I could figure out all the necessary data for. May just have to spend a bit of time...

The AI was saying around 8mm max, and this at least it was consistent about in it's different answers. Would be good if someone could confirm this sounds reasonable though. Visually I don't really care if it's more - but I suppose the main consideration is that too much deflection would pull on...

Makes sense. Will change plans to use box section. Any thoughts on what dimensions/thickness I'd need? Just called "The Metal Store" for advice, but they apparently have no technical knowledge of their products: "we're just a retailer"... As you said before, I think deflection is the main...

I suppose it is, just across a small section of the room

Have been reading up on this, and have indeed concluded that box section tube is more suitable! Which kind of makes the title of this thread redundant, should probably start a new one... But could you recommend what sort of thickness and cross-sectional size would work for this? (3.1m span, 6kg...

My original plan was to use wood - but after exploring options I concluded this would be heavier, more bending (so more strain on wall plugs) and just less reliable over time than metal. But change my mind! Wood would be easier overall to work with.

Thanks for this - and for the engineering toolbox link! Yes, the AI... I was actually just logging back on to say I'd double checked the AI's answer by initiating a separate "conversation" (with the same AI model) and asking the same question. And got a totally different answer... So tried a...

Hope this is the correct section of the forum to post this. I'm constructing something within a home studio to suspend acoustic panels from - they'll be right over my head, so want to make sure I'm choosing a sufficient thickness of aluminium angle iron! For multiple reasons, I cannot suspend...

I'm constructing a rather complicated contraption for mounting overhead acoustic panels in a home studio, which I won't try and describe here, but it'll be made using a combination of wooden battens, aluminium angle-iron, and heavy duty L-brackets. I'd like to paint all these with the same paint...

Just to report back, this red devil one time filler came in very useful indeed, so many thanks for that recommendation! Not just for the nail holes in skirting, but also various general filling and smoothing of small cracks and imperfections in walls before (and during painting) - ended up going...

Any tips re. sanding glossy doorframes before repainting? Main questions are: 1) Will wet sanding work here? And if so, what's the best method, e.g. cold vs warm water, and does it help to add some fairy liquid? 2) What grit should I use? 3) How much do I need to sand? Is it OK to just lightly...

I've got a feeling the nail holes are so tiny that swelling etc wouldn't be an issue - BUT have missed my slot for painting this weekend, so will take no chances, and order some RedDevil. Unless there's an equivalent product that is stocked by Screwfix/Toolstation/Wickes/B&Q? e.g. would...

Just looked up some info on RedDevil OneTime - this does look ideal - for one thing, it says it's suitable for wood, which polyfilla doesn't claim. That said, have experimentally filled a couple of holes with polyfilla, and it looks fine so far... Holes filled, looks level, doubt you'd notice...