Torsion box shelf construction advice

[claptonkid]

Hi all,

I'm soon to make some 40mm thick alcove shelves for a client, which'll measure around 1100mm long x 370mm deep. They'll be handpainted by the client once fitted.

I thought of following the 'torsion box' method with two 6mm mdf skins and and an inner frame using 25mm x 28mm mdf battens. I'll then slide the shelves onto battens fixed around the alcove (assuming the space is wider at front than at the back). If not I'll screw the two skins around the battens on site.

Could anyone possibly advise on the best arrangement for the inner structure, i.e. spacing, number of battens etc? I'll be assembling using a pin gun and clamps. Also considering investing in a bag press if it aids the process.

Thanks in advance for any help.

Karl

 

[andersonec]

Karl, have a look here.
http://www.woodworkersinstitute.com/page.asp?p=705
And here
http://www.woodworkuk.co.uk/forum/viewt ... f=9&t=3053
I have Never done it before but am due to have a crack at a couple for a friend sometime in the near future with cherry faced mdf and walnut nosing, doesn't seem to be much of a problem with the construction, it seems the problems start if the walls are out of parallel, the guy at woodworkuk solved it by making cleats for the ends, dry fitting them then offered the whole thing up and scribed the cleats.
Andy

 

[Steve Maskery]

Just a word to the wise if you use a vac bag.
It is all too easy to apply so much vac pressure on your structure that it collapses. It doesn't collapse gently, oh no, it collapses with a vengeance. It not pop, it's BANG, job over.

Don't ask me etc., etc.

Cheers
Steve

 

[mailee]

:lol: Ah I see you have done that too then Steve! Of course I would never do that with my vacuum bag. :roll: I did that the first time I tried to make a template for curved doors. It certainly does go with a bang doesn't it? :roll:

 

[claptonkid]

Brilliant - really useful advice. Thanks chaps.

Impressed by the scribing cleat idea - fortunately, these shelves are just going to be hand-painted MDF. So, if alcoves are dovetailed awkward way round, I'm now thinking of gluing up the shelves in situ; top skin with battens already attached to underside and then screwing/pinning bottom skin on from below. Then filling. Sound ok?

And I too have heard about the vacuum press collapsing the shelves. Guess that putting an extra couple of protective pieces of MDF around the shelves might help avoid this happening?

Also, any views on what I should be charging for 6 No 1100mm x 370mm shelves like this? Plain MDF. I'm in London.

Thanks again for the advice.

 

[petermillard]

Hi. I do it the other way around - fit the softwood battens to the alcove first then scribe the top & bottom 'skins' to fit. Pinned and glued around the sides and back, just clamped and glued along the front edge whilst the the glue grabs. Front edge is covered with strip wood or 6mm MDF to hide the MDF/softwood/MDF sandwich. For a full alcove of shelves, I usually template the alcove all there way up so I can minimise the scribing onsite.

If I know the shelves are going to take a lot of weight, or if they're a particularly wide span, I epoxy a square-section steel bar behind the leading edge, just to be sure they don't sag.

For six-off in the same alcove I charge £480 fitted, primed but not painted. I'm in West London.

HTH Pete

 

[claptonkid]

Thanks Pete - that's really useful.

So, just to clarify - battens are screwed to sides and back of alcove first - then you scribe top and bottom skins to alcove. Do you next glue timber reinforcing frame to top skin and lastly put in place and screw bottom skin to top skin?

Thanks

Hi. I do it the other way around - fit the softwood battens to the alcove first then scribe the top & bottom 'skins' to fit. Pinned and glued around the sides and back, just clamped and glued along the front edge whilst the the glue grabs. Front edge is covered with strip wood or 6mm MDF to hide the MDF/softwood/MDF sandwich. For a full alcove of shelves, I usually template the alcove all there way up so I can minimise the scribing onsite.

If I know the shelves are going to take a lot of weight, or if they're a particularly wide span, I epoxy a square-section steel bar behind the leading edge, just to be sure they don't sag.

For six-off in the same alcove I charge £480 fitted, primed but not painted. I'm in West London.

HTH Pete

 

[petermillard]

I screw the back batten to the wall, then the sides, then the front batten into the side battens - front & back battens run full width of the alcove. Then I scribe the top & bottom skins, glue and pin, clamp etc.... No fixings are used on the leading edge of the shelves, just glued and clamped up for 10 mins..

I start at the lowest shelf taking time to get this level and true; all subsequent shelves are referenced off this one so it has to be right. Spacing is made with simple MDF jigs made from scraps, to whatever the spacing needs to be - I'll have already worked this out from my drawings/conversations with the customer e.g. bottom shelf at 450mm, then subsequent shelves at say, 320mm would mean a pair of MDF jigs/squares at 320mm minus the thickness of the shelf, plus the thickness of the bottom skin - important not to forget about that otherwise your shelves get progressively closer together as they go up - DAMHIKT!

Once the bottom shelf is in, the next back batten just rests on the jigs and is drilled through into the wall - you know it's level because you're referencing off the bottom shelf you took all that time over; ditto the side battens. The front batten simply screws into the end grain of the side battens, then the top & bottom skins fitted.

I've found working this way is fast and efficient - nice earner too

Cheers, Pete.

 

[claptonkid]

Thanks Pete. You've been hugely helpful. It's not a method I've ever considered - sounds great!

Thanks again.

Karl

I screw the back batten to the wall, then the sides, then the front batten into the side battens - front & back battens run full width of the alcove. Then I scribe the top & bottom skins, glue and pin, clamp etc.... No fixings are used on the leading edge of the shelves, just glued and clamped up for 10 mins..

I start at the lowest shelf taking time to get this level and true; all subsequent shelves are referenced off this one so it has to be right. Spacing is made with simple MDF jigs made from scraps, to whatever the spacing needs to be - I'll have already worked this out from my drawings/conversations with the customer e.g. bottom shelf at 450mm, then subsequent shelves at say, 320mm would mean a pair of MDF jigs/squares at 320mm minus the thickness of the shelf, plus the thickness of the bottom skin - important not to forget about that otherwise your shelves get progressively closer together as they go up - DAMHIKT!

Once the bottom shelf is in, the next back batten just rests on the jigs and is drilled through into the wall - you know it's level because you're referencing off the bottom shelf you took all that time over; ditto the side battens. The front batten simply screws into the end grain of the side battens, then the top & bottom skins fitted.

I've found working this way is fast and efficient - nice earner too

Cheers, Pete.

 

[claptonkid]

Hi again Pete,

Finally getting onto this alcove shelf project - now I've got the compressor and brad nailer.

One last question, if you don't mind. Do you machine up your softwood battens or just buy from the timber merchants? I'll be making 40mm shelves so I could machine up some 28mm thick battens, but are timber battens at a similar size off the shelf ok to use. Or are they best avoided given a lot are banana-shaped?

Thanks,

Karl

I screw the back batten to the wall, then the sides, then the front batten into the side battens - front & back battens run full width of the alcove. Then I scribe the top & bottom skins, glue and pin, clamp etc.... No fixings are used on the leading edge of the shelves, just glued and clamped up for 10 mins..

I start at the lowest shelf taking time to get this level and true; all subsequent shelves are referenced off this one so it has to be right. Spacing is made with simple MDF jigs made from scraps, to whatever the spacing needs to be - I'll have already worked this out from my drawings/conversations with the customer e.g. bottom shelf at 450mm, then subsequent shelves at say, 320mm would mean a pair of MDF jigs/squares at 320mm minus the thickness of the shelf, plus the thickness of the bottom skin - important not to forget about that otherwise your shelves get progressively closer together as they go up - DAMHIKT!

Once the bottom shelf is in, the next back batten just rests on the jigs and is drilled through into the wall - you know it's level because you're referencing off the bottom shelf you took all that time over; ditto the side battens. The front batten simply screws into the end grain of the side battens, then the top & bottom skins fitted.

I've found working this way is fast and efficient - nice earner too

Cheers, Pete.