Hi all. Been a while since i posted. I have a fun problem solving challenge, and thought it would be fun to use the hive mind.
I am building a sort-of mezzanine bed for a customer, which will be seen from below. He had an idea that he wanted me to build the frame that goes directly under the bed (which will be tatami mats and a futon - this mini remodelling project has taken on a japanese theme) in the style of the 'cradling' that 'old masters' picture frames sometimes used to build very large and very solid picture frames. It also ties in with the japanese look.
So I agreed it would be a fun design principle and have designed something along similar lines
This is it seen from below:
My question relates to the grid in the middle. The timber by the way is all yew(!) which is lovely to work and also annoying in that finding and getting useable sections out of even a big fat juicy looking board is difficult. Luckily he has access to a decent stash.
Material worries aside, the grid is currently drawn in 30mm wide by 45mm high sections. The sides are the narrower edges, the wider are head and foot boards. My current concern is how to join the grid to maximise rigidity over the span (6' both ways), and my options as far as i see it are a) dominos at all edges and lap all the internal joins, or b) dominos at all edges, keep all head to foot spans whole and domino each of the cross-wise 'noggins' in.
Pros and cons to each, both pretty laborious and obviously will require much focus while machining! I feel like half-lapped joints are weaker, even if they are all perfectly nice and snug and glued, because every single piece has its effective load bearing height halved, 22.5mm isnt much. But on the other hand there are a lot of them to spread the weight, and the one good glue face will count against this to some extent, and i wonder about offsetting the lap in favour of the downward facing joins that want to open up and reducing the height at the join of those below, which will want to pinch shut under pressure anyway.
The alternative, of putting a million dominos in everywhere, is very time consuming, but allows for greater material efficiency (can use up short sections of stock rather than needing lots of decent long ones) and leaves all spans full height, in one direction at least. The joinery will be aesthetically more forgiving, and yew is pretty stable but if those joints aren't all snug over time thats a visual and structural problem. A butt join and through domino (might machine up extra long small ones even) through each junction, glued across noggin ends, is more side grain glue surface, and feels like it might be stronger. However I cannot even begin to imagine how hellish that glue up would be!
This is all coming from intuition, which is why im asking. Im no structural engineer - I have under-engineered things in the past and it can be quite unrelaxing! So id be very grateful for opinions (other than, youre mad, its not going to work) and ideas, open to any other totally different approaches too.
I am building a sort-of mezzanine bed for a customer, which will be seen from below. He had an idea that he wanted me to build the frame that goes directly under the bed (which will be tatami mats and a futon - this mini remodelling project has taken on a japanese theme) in the style of the 'cradling' that 'old masters' picture frames sometimes used to build very large and very solid picture frames. It also ties in with the japanese look.
So I agreed it would be a fun design principle and have designed something along similar lines
This is it seen from below:
My question relates to the grid in the middle. The timber by the way is all yew(!) which is lovely to work and also annoying in that finding and getting useable sections out of even a big fat juicy looking board is difficult. Luckily he has access to a decent stash.
Material worries aside, the grid is currently drawn in 30mm wide by 45mm high sections. The sides are the narrower edges, the wider are head and foot boards. My current concern is how to join the grid to maximise rigidity over the span (6' both ways), and my options as far as i see it are a) dominos at all edges and lap all the internal joins, or b) dominos at all edges, keep all head to foot spans whole and domino each of the cross-wise 'noggins' in.
Pros and cons to each, both pretty laborious and obviously will require much focus while machining! I feel like half-lapped joints are weaker, even if they are all perfectly nice and snug and glued, because every single piece has its effective load bearing height halved, 22.5mm isnt much. But on the other hand there are a lot of them to spread the weight, and the one good glue face will count against this to some extent, and i wonder about offsetting the lap in favour of the downward facing joins that want to open up and reducing the height at the join of those below, which will want to pinch shut under pressure anyway.
The alternative, of putting a million dominos in everywhere, is very time consuming, but allows for greater material efficiency (can use up short sections of stock rather than needing lots of decent long ones) and leaves all spans full height, in one direction at least. The joinery will be aesthetically more forgiving, and yew is pretty stable but if those joints aren't all snug over time thats a visual and structural problem. A butt join and through domino (might machine up extra long small ones even) through each junction, glued across noggin ends, is more side grain glue surface, and feels like it might be stronger. However I cannot even begin to imagine how hellish that glue up would be!
This is all coming from intuition, which is why im asking. Im no structural engineer - I have under-engineered things in the past and it can be quite unrelaxing! So id be very grateful for opinions (other than, youre mad, its not going to work) and ideas, open to any other totally different approaches too.
