Sagging?

[wizer]

Hello

I want to get a quick project out the door using this Iroko. It's a simple coffee table with a somewhat wacky design feature.

I want to use steel rod for the joinery, giving it a floating feel.

Question is, will this sag? The size is 550 x 1100 x 22mm I looked it up on the Sagulatorand it seemed to output a sag of 1.3mm assuming a 25kg weight was left in the middle. Is this a real life issue, should I brace the top with thick timber?

 

[jasonB]

I don't think it will be a problem, 25kg is a big bowl of fruit :wink: and even if you sit there with your feet up on it a mm or two won't matter. Also the span between supports will be 960mm so this may reduce the calculated sag.

just sink the rods in a decent distance as they are close to the edge of both the legs & top.

Jason

 

[wizer]

Thanks Jason, how might I glue the rods in? Epoxy? Any idea where to get it from?

 

[Mattty]

Thanks Jason, how might I glue the rods in? Epoxy? Any idea where to get it from?

Araldite would probably do for this though i'm not certain. Easily checkable though.

It looks like a contrasting timber in the middle of the leg. What have you got in mind?

As for the sagulator!! What a find, i've never seen this before.

 

[cant-weld-wood]

if you go ahead with this tom let me know wot size rod you need
a friend makes steel gates.
i should be able to get some of cuts for you.


ps: and let me know wot i owe for fuel i will drop it round to you

 

[thomvic]

An interesting design though not my cup of tea! I suggest chromed steel or satin finish stainless fixed with Araldite.

 

[OPJ]

I reckon it'll be fine with the weight as well. How heavy's your bobbin sander? That's gotta be close to 30kg - I can't imagine you're likely to have anything more than a few cups of tea and the odd magazine on top, so I wouldn't worry about it.

Are the top and shelf edges finishing flush with the outside faces of the legs?

 

[Steve Maskery]

Wizer

Your bigger design problem is that there does not appear to be any allowance for cross-grain shrinkage-expansion.

I can recommend West Systems epoxy from Axminster.

Cheers
Steve

 

[jasonB]

Araldite would do the job OK as its easy to get hold of and you don't need vast amounts.

I would go with stainless steel rod, spin it up in a bench drill and use either 320g silicon carbide paper or a scotchbrite pad for a easy "brushed" look.

I don't think cross grain shrinkage will be an issue as all the grain runs the same way in both the top, shelf and legs

Jason

 

[Steve Maskery]

Quite right, Jason, I hadn't spotted that - no rails at all

S

 

[newt]

Wizer I to have an issue with cross grain movement

 

[wizer]

Guys many thanks for your help.

With regards to the design. It's not really my cup of tea either. I thought it would be a nice quick project for me (hence the rods) and it's for my sister-in-law who likes ultra modern furniture (Read: Ikea/Habitat). It will also give me a chance to see how the Iroko looks and works. The contrasting timber is beech (guess why?). However, I am playing with an altered design which uses a tapered leg and I'm not sure that contrasting sandwich would work in that situation.

I am concerned with this cross grain issue. Here is a view from the top of a leg/corner

Will this be a problem?

 

[Jake]

That's going to be an interesting joint to assemble - unless the rods go through the legs and are plugged over?

 

[wizer]

Good point Jake, I am here to learn.

They could only go all the way if they where off-set.

One thought I had was to make the top and shelf 'loose', just resting on the bar in grooves. Making transport easier, but I thought it might be a bit unsteady and naff.

 

[Chris Knight]

As Jake says!

Why bother with the transverse rods at all?

 

[wizer]

Yes that makes sense, I'll see what it looks like in SU.

 

[Jake]

Thinking about it, you could araldite the rods on one side into a block of wood, which then at main glue up slides into a groove recessed in the side of the top (and is itself glued in).

Like Jason, I don't see any cross-grain problem.

 

[wizer]

Or one side had grooves milled in under the top which where later filled with timber?

 

[jasonB]

Now I can see rods in both sides of the leg ther is a minor Xgrain issue but as its only over about 2" (assume rods on 1" cts) it will be minimal.

If you want rods both ways drill one set of holes over long, slip in dry rods, glue the other set as structural then slide out the dry rods and just glue them into the leg, we won't tell anyone how you did it :wink: Best to have the dry ones in line with the short dimension then the fact they are not structural will help with the Xgrain issue.

Jason

 

[wizer]

I think I get it Jason. So I'm clear, the rods are fed, dry, into a hole bored 30mm long in the top. When the rods on the other side are dry, some glue can be put in the leg holes and then the dry rods can be slid into the holes on the legs?

Am I seeing that right? Sounds like a plan.