2 foot chair

[Helvetica]

I'm starting my first woodworking project (not counting my workbench) - a chair for my nephew who is due in a few weeks. It's heavily based on Chem's design, many thanks for that, from this link
childs-table-chair-set-and-cutting-board-t52412.html
I have just finished up the plan in google sketchup and have come across an area I could do with some advice on. The base of the chair is going to be an un-openable box for us to pop things in like photos etc, to be opened in years to come. I plan to tenon the box walls into mortises on the chair legs. The problem is the base, at the moment I have it sliding through from the back of the chair, and resting on a 45 degree mortise out of the front legs, and a through-tenon out of the rear legs, but I'm not so sure this is the best way to for the base. Would anyone have any ideas? Here are a few pics of the sketch. I can attach the sketchup file if anyone is interested in taking a look. Thanks a mill, Paul

 

[Hudson Carpentry]

Am I right in thinking the sliding bottom is the only way to open the box?

If it was me I would use a housing joint, some call it a dado. One on each leg about 4-8mm deep would do the job just fine.

 

[Helvetica]

Thanks 'Hudson Carpentry' I'll try the dado

I bought 2 planks of 12' long 8x2" hard maple which, according to my plan, will give me all the wood I need for one chair. At €50 I hope I don't make many mistakes! First task was to divide 2 pieces in quarter lengthways for the box sides (to make 8 pieces 1/2" thick). My saw skills really need some practise! the kerf is rough as hell.

I have come across a small problem though - I made the cuts a week ago, and the pieces seem to have cupped in the centre by a millimeter or two. Now this isn't green lumber, it's kiln dried. Is this a stage of drying out, or is it more to do with the mysterious pressures within timber that get released when sawing into thin pieces? So what do I do, should I wait another week or two, then put it through the thicknesser (again) before I joint & glue the pieces together?

cheers

 

[Pvt_Ryan]

I have come across a small problem though - I made the cuts a week ago, and the pieces seem to have cupped in the centre by a millimeter or two. Now this isn't green lumber, it's kiln dried. Is this a stage of drying out, or is it more to do with the mysterious pressures within timber that get released when sawing into thin pieces? So what do I do, should I wait another week or two, then put it through the thicknesser (again) before I joint & glue the pieces together?

This is due to the internal stress in the wood I had the same problem when I 1st started with walnut couldnt work out what was wrong with my cutting.

The problem is by ripping the wood in the way you have you have released the stress on one side and not equally on the other. This is why there is so much wastage from wood as to get to a thickness of 12mm from 24mm you have to remove 6mm from each side instead of just cutting it in two.

Someone with more knowledge than I will chip in no doubt and give a better explanation but mine should be accurate enough.

Depending on the thickness required you might just need to scrap those pieces and start again or if you can do as low as 6mm then depending on the severity of the cupping you might be able to get it through a planer/thicknesser alternating the sides and still have something usable. Again I hope someone with more knowledge that I will correct me if I am wrong or there is a better way.

Ryan

 

[Helvetica]

Cheers ryan, I think I'll get away with thicknessing the wood. So do I have to wait for the pieces to stabelise, or has any cupping that will happen already happened?

 

[Pvt_Ryan]

if it's been a week or so you are probably ok, but i'd leave them to almost the last moment if possible.

 

[Hudson Carpentry]

Its may have happened for the reason Ryan has said. You always need to consider this when resawing, by buying big and resawing you can end up costing yourself more in having to buy more wood. The stress release is normally fairly instant and you see the wood bend or notice its not right when you push it through the planer. As you said it happened after a week makes me think it could also be more acclimatising. Has it been stored stood up or in a different place?

If its stress lated just plan it down and that should be the end of it.

 

[Helvetica]

Well I noticed it after a week, but after sawing another today, it looks like it's happening instantly. That's ok I can plane them thinner and get away with it. A new problem has surfaced though! The now 7.5mm maple is flexible, so when it goes through the thicknesser it doesn't correct the cupping, it just bends flat and thicknesses, then the cupping springs back. Any workaround for this? Cheers

 

[Hudson Carpentry]

What part of the chair are they for? It maybe possible to arrange it or fix it in a way where it corrects the cupping due to the flex.

 

[Helvetica]

Fair point HC, these panels make the box part of the chair, and will blind tenon into the legs. Cupping would probably be negligible when they're in place. Thanks again

 

[Hudson Carpentry]

Options:

Arrange them so the cupping is "pointing" inside the box, then put a batten/clit across the back of the panels inside and fix to the the rails/stiles pushing the cups out. If that makes sense.

If you are confident that you could tongue and grove these then there will be no need for a batten inside. Arrange them so there is one cup "pointing" out and the next pointing in and the next out etc. T&G the ends. (its risky on something thats 7.5 thick, if you have the capabilty then a 2mm loose tongue may just be enough. Im only suggesting a T&G method at this size as its maple).

Arrange in the same way for T&G but just butt joint and glue the ends using 4D clamps or the alike and it should counter and be a fairly flat panel once the glue cures. (leave it clamped 24 hours even if the glue says 20min).

Combo of option 1 and 3.

 

[Helvetica]

I got this chair finished, only took 3 months! My tenons are fairly agricultural, but my skills have improved substantially in this project alone. thanks for all the advice, 'twas very valuable. Here are a few pics for you to have a laugh at! I might stain the seat, then danish oil the whole chair, any thoughts?

 

[Helvetica]

Hi folks, quick bit of advice needed again! If you look at the 3rd photo (1986.img) you will see the seat lies on the front legs, but there is no tenon securing it. After gluing, and bringing inside the house to dry (mistake), the seat has curled and lifted off the front of the box and the front legs, breaking the glue joint. I'm wondering should I nail it, screw it down, drawbore it, or leave it alone. Bear in mind a nail would have to go a half inch from the edge of the seat, and would be going into the endgrain of the front legs. Any advise much appreciated!
Paul