Bowed long boards - any remedy?

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
Yes, the central bearer is positioned horizontally, i.e., the wide faces are parallel to the ground. You could certainly strengthen it by adding a piece on the underside (glue and screw), but I really don't thinks it's needed. I say that because in the case of one the beds I've made the mattress supporting slats are 20 mm thick poplar (tulipwood) on top of the ~60 X 32 mm poplar longitudinal bearer carrying an 80" X 60" (2030 X 1520 mm) mattress, and after nearly twenty years there's no appreciable sagging of either the slats or the longitudinal bearer. This bed is in our bedroom, it being being one of a pair I made, one for a customer and the extra one for us. There's also no additional middle leg, and time has proved it's not necessary, but if you want to include one on your bed, that's your choice. Adding one does rather clutter up the under bed space, but it's your choice.

I wouldn't choose your side rail connection method. If I was going to put a bolt of some sort in I'd want the bolt to pass all through the leg. With yours there's a small chance the brass threaded insert could pull out from the leg leading to looseness at the rail leg intersection. In addition you need a spanner to assemble the bed, whereas with the Noval K type fittings the two parts lock together as the side rail hook part drops into the leg mounted socket part. In general I'm not a fan of bolt together beds, but that's just my personal bias. If it works for you and you're happy with it you'll be in line with a lot of other people that have used the same assembly method. Slainte.
Thanks.

I have decided not to use through bolts because I can buy here only cheap-looking bolts (zinc-galvanized no brass other than the hexagonal head). I think that your Noval K fitting is easier to assemble and less work is also required to install it on the rail/leg than my method. What is the correct procedure of installation to ensure that there is no gap between the leg and rail for this type of connector? Shall I screw the first part to the leg, then assemble both parts of the fitting together and then make holes for screws on the side rail when side boards are attached tightly to the leg?

Is there a requirement that either side rail or footboard or headboard boards must be flush with the inner corner of the leg so that there will not be a big gap after I add the mattress? If not, I could use Noval K fitting, because it is less work for me, provided I can make the resulting butt joint tight.
 

Sgian Dubh

Established Member
Joined
12 Oct 2004
Messages
2,696
Reaction score
521
Location
UK
I think that your Noval K fitting is easier to assemble and less work is also required to install it on the rail/leg than my method. What is the correct procedure of installation to ensure that there is no gap between the leg and rail for this type of connector?

Is there a requirement that either side rail or footboard or headboard boards must be flush with the inner corner of the leg so that there will not be a big gap after I add the mattress?
It's been quite some time since I used the Noval K type fittings and I don't recall exactly how the two parts are positioned on the rail and the leg. My memory may be faulty but in the back of my mind I have the impression the fittings come with a card template that you offer up to the wooden parts to get the position right. It's that or suppliers such as Hafele have downloadable technical documents you can use to position the hardware correctly. And if it really comes down to it and there are no templates or technical guidance documents you can always make a mock up of rail to leg parts and do some test installations to get the positioning right.

As to your other question about the inner corner of the leg and the position of the rails (side and head/footboard) the inner face of these rails don't need to be flush with the inside corner of the leg, and setting the rails back from the inside corner by 20 - 30 mm shouldn't be a problem - mattress corners are rounded. From your drawings it looks like the mattress will be trapped by the headboard and footboard and by the side rails because the top edges of all these parts are higher than the top face of the supporting slats. Generally, where this is the case I've always made the internal dimensions of the bed's framework 50 - 60 mm larger than the mattress size. So, for example, if your mattress is 1500 mm wide, the gap between the side rails will be ~1550 mm, and the same applies to the bed's length, e.g., a mattress 2000 mm long has a space ~2050 mm long in which to fit. The reason for doing this, particularly if both the headboard and footboard are tall which is not the case with your footboard, is so that there's room for tucking in bedding neatly, or space in to which downies can drop freely. Slainte.
 
Last edited:

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
It's been quite some time since I used the Noval K type fittings and I don't recall exactly how the two parts are positioned on the rail and the leg. My memory may be faulty but in the back of my mind I have the impression the fittings come with a card template that you offer up to the wooden parts to get the position right. It's that or suppliers such as Hafele have downloadable technical documents you can use to position the hardware correctly. And if it really comes down to it and there are no templates or technical guidance documents you can always make a mock up of rail to leg parts and do some test installations to get the positioning right.

As to your other question about the inner corner of the leg and the position of the rails (side and head/footboard) the inner face of these rails don't need to be flush with the inside corner of the leg, and setting the rails back from the inside corner by 20 - 30 mm shouldn't be a problem - mattress corners are rounded. From your drawings it looks like the mattress will be trapped by the headboard and footboard and by the side rails because the top edges of all these parts are higher than the top face of the supporting slats. Generally, where this is the case I've always made the internal dimensions of the bed's framework 50 - 60 mm larger than the mattress size. So, for example, if your mattress is 1500 mm wide, the gap between the side rails will be ~1550 mm, and the same applies to the bed's length, e.g., a mattress 2000 mm long has a space ~2050 mm long in which to fit. The reason for doing this, particularly if both the headboard and footboard are tall which is not the case with your footboard, is so that there's room for tucking in bedding neatly, or space in to which downies can drop freely. Slainte.
That is a great idea to create short pieces from scrap with identical cross-sections and try the hardware there. I will see how stiff the joint is on this test piece.

The mattresses will be 60 mm down in the area enclosed by foot/headboard and sideboards. I have added 1 cm extra in total width and length for some allowance. You suggest 5 - 6 cm. The issue is that I will not have one single mattress, but two 90x220 cm. I am afraid that they will part away during use and a gap will be created in the middle. I can create the space around two mattresses a little bit bigger, but I think I would need to make two wooden sticks for each side of the bed that will constrain the mattresses from moving around. They will be planed down to the width that is as wide as the actual gap between the mattresses and sideboard/footboard/headboard.
 

Sgian Dubh

Established Member
Joined
12 Oct 2004
Messages
2,696
Reaction score
521
Location
UK
That is a great idea to create short pieces from scrap with identical cross-sections and try the hardware there. I will see how stiff the joint is on this test piece.

The mattresses will be 60 mm down in the area enclosed by foot/headboard and sideboards. I have added 1 cm extra in total width and length for some allowance. You suggest 5 - 6 cm. The issue is that I will not have one single mattress, but two 90x220 cm. I am afraid that they will part away during use and a gap will be created in the middle. I can create the space around two mattresses a little bit bigger, but I think I would need to make two wooden sticks for each side of the bed that will constrain the mattresses from moving around. They will be planed down to the width that is as wide as the actual gap between the mattresses and sideboard/footboard/headboard.
If no guidance or template is provided, to create your test piece screw the slotted part of the Noval K fitting to your leg mock-up. Then connect the metal hook part to the slotted part, offer up your rail to the hook part and mark the screw holes. Bore the holes, attach the hook part and assemble your mock-up. Adjust as required.

As to the oversize space allowance around your mattress(es), I would only finalise this requirement based on the actual mattress. In other words, I'd want the mattress available to take into my workshop if necessary so that I can do physical tests for the allowance, not a theoretical mattress available online, in a shop or a paper catalogue because what gets delivered may not match exactly the manufacturers stated dimensions. Still, in my experience I've always found an allowance of about 50 mm greater than the mattress dimensions has worked for me. Incidentally, can your two mattresses be linked together with clips or something so that they in effect act as one unit? Slainte.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
If no guidance or template is provided, to create your test piece screw the slotted part of the Noval K fitting to your leg mock-up. Then connect the metal hook part to the slotted part, offer up your rail to the hook part and mark the screw holes. Bore the holes, attach the hook part and assemble your mock-up. Adjust as required.

As to the oversize space allowance around your mattress(es), I would only finalise this requirement based on the actual mattress. In other words, I'd want the mattress available to take into my workshop if necessary so that I can do physical tests for the allowance, not a theoretical mattress available online, in a shop or a paper catalogue because what gets delivered may not match exactly the manufacturers stated dimensions. Still, in my experience I've always found an allowance of about 50 mm greater than the mattress dimensions has worked for me. Incidentally, can your two mattresses be linked together with clips or something so that they in effect act as one unit? Slainte.
Thank you very much for your precious advice. So in reality, I would have to buy mattresses before I trim all long boards to length and start cutting tenons on footboard/headboard. I will do as you advise and I will add 50 mm allowance in total (i.e. 25 mm from each side for width and length). I can always fill up the gap, but when the mattresses are too big for the frame it would be a far worse issue.

I have no idea if there is a standardised way to link two mattresses together or I only need some DYI solution. I will have to google it.
 

Sgian Dubh

Established Member
Joined
12 Oct 2004
Messages
2,696
Reaction score
521
Location
UK
Thank you very much for your precious advice. So in reality, I would have to buy mattresses before I trim all long boards to length and start cutting tenons on footboard/headboard.
As a general rule I aim to have any hardware, or similar, to hand before I embark on making. That applies to anything that has to be bought in and later fitted or attached to what I've made. Many years ago I got caught out because I built a piece on the assumption the type of hardware I'd used before, planned to use again on this new piece, and would buy later. Of course, when I did go to buy the hardware it was either discontinued and no longer available, or the specs had been changed - I can't remember which now. I had to do some bodging to marry whatever hardware I ended up being supplied with with the already made piece. I learnt my lesson, i.e., never assume that what you plan to buy is actually as you expect it to be; sometimes it's not. Slainte.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
As a general rule I aim to have any hardware, or similar, to hand before I embark on making. That applies to anything that has to be bought in and later fitted or attached to what I've made. Many years ago I got caught out because I built a piece on the assumption the type of hardware I'd used before, planned to use again on this new piece, and would buy later. Of course, when I did go to buy the hardware it was either discontinued and no longer available, or the specs had been changed - I can't remember which now. I had to do some bodging to marry whatever hardware I ended up being supplied with with the already made piece. I learnt my lesson, i.e., never assume that what you plan to buy is actually as you expect it to be; sometimes it's not. Slainte.
That is a good idea - I also want to buy hardware first and then drill holes, make recesses, etc. But as this is my first bed ever, I have a rather illogical feeling, that I am afraid to buy mattresses before I build the frame. I hope I will get over such feelings as I get more experienced.
 

throbscottle

Established Member
Joined
12 Jun 2022
Messages
35
Reaction score
16
Location
Nuneaton
New to the forum here, but I can relate to bent stuff!
When I worked for a guy who made antique furniture, we'd produce a bent cupboard door now and again. The trick is to soak the inner face of the bow, which expands. Fastening it in place so it can't go back when it dries makes it keep it's shape (or in his case, keep it long enough to sell the piece anyway). I used the same trick on a piece of skirting board earlier this year too.
So turn it so the ends stick up, fasten them down, and give the upper side (ie, inside of the curve) a good wetting and leave overnight. Hopefully it'll be a lot straighter when it's dry again.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
New to the forum here, but I can relate to bent stuff!
When I worked for a guy who made antique furniture, we'd produce a bent cupboard door now and again. The trick is to soak the inner face of the bow, which expands. Fastening it in place so it can't go back when it dries makes it keep it's shape (or in his case, keep it long enough to sell the piece anyway). I used the same trick on a piece of skirting board earlier this year too.
So turn it so the ends stick up, fasten them down, and give the upper side (ie, inside of the curve) a good wetting and leave overnight. Hopefully it'll be a lot straighter when it's dry again.
Thank you very much. I will try that soon.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
I have finished planing the boards for the bed. Legs will be 51x51 mm and long boards (foot board, head board and side rails yielded 120x25 mm. Some of those long boards are still slightly bowed, but by screwing bearers to side rails and also on the board on the footboard and bottom board on the headboard they will straighten out nicely.
 

Sgian Dubh

Established Member
Joined
12 Oct 2004
Messages
2,696
Reaction score
521
Location
UK
It seems like you've made satisfactory progress, and in doing so it looks like you might have allayed your anxieties about any bowing, or that you can see that bows you have in certain pieces can be pulled straight.

Incidentally, I appreciate the progress report, it being a form of validating feedback for those that try to help those with questions. Slainte.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
It seems like you've made satisfactory progress, and in doing so it looks like you might have allayed your anxieties about any bowing, or that you can see that bows you have in certain pieces can be pulled straight.

Incidentally, I appreciate the progress report, it being a form of validating feedback for those that try to help those with questions. Slainte.
Thank you. Yes, I try to get back to the threads that I have posted and drop progress/success/failure note so that people know what is my current status with the matter.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
What is the adequate size for tenon when legs are 50x50 mm and rails are 25 mm thick? Will 12 mm tenon be thick enough for a bed? Only footboard and headboard will be tenoned. Side rails will be mounted with hardware as mentioned above. Width of the rail is 120 mm and there will be 2 x 40 mm wide double tenon that will be 35 mm long.

Thank you.
 

Jacob

Pint of bass, porkpie, and packet of crisps please
Joined
7 Jul 2010
Messages
22,931
Reaction score
2,789
Location
Derbyshire
What is the adequate size for tenon when legs are 50x50 mm and rails are 25 mm thick? Will 12 mm tenon be thick enough for a bed? Only footboard and headboard will be tenoned. Side rails will be mounted with hardware as mentioned above. Width of the rail is 120 mm and there will be 2 x 40 mm wide double tenon that will be 35 mm long.

Thank you.
Pedantic, but two single tenons not the same as a "double" tenon, which you'd expect to be side by side.
Sounds OK but make them 40mm long and add 12mm haunches between.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
Pedantic, but two single tenons not the same as a "double" tenon, which you'd expect to be side by side.
Sounds OK but make them 40mm long and add 12mm haunches between.
Thank you. Yes they are two serial tenons following each other, not two parallel tenons, so word double was inappropriate. I did not think about the haunch, but makes sense to me, so I will add it in between the tenons.
 

Sgian Dubh

Established Member
Joined
12 Oct 2004
Messages
2,696
Reaction score
521
Location
UK
Thank you. Yes they are two serial tenons following each other, not two parallel tenons, so word double was inappropriate. I did not think about the haunch, but makes sense to me, so I will add it in between the tenons.
If they are going to look something like the images below I've always known them as Forked M&Ts. Slainte.

M&T-Forked-700px-web.jpg


M&T-forked 1-cropped-lo-res.jpg
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
If they are going to look something like the images below I've always known them as Forked M&Ts. Slainte.

Exactly, but my mortices will be blind, so no kerfs for wedges and relief holes are necessary. However, I will drawbore them, as I do not have 2 m clamps and oak dowels will give the bed a nice accent.
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
Pedantic, but two single tenons not the same as a "double" tenon, which you'd expect to be side by side.
Sounds OK but make them 40mm long and add 12mm haunches between.
What is the correct procedure for cutting that forked mortice? Do you cut two separate mortices and then remove the material between for hauncheon or do you cut it as a single mortice to a hauncheon depth and then cut two deeper trenches for mortices?
 

Sgian Dubh

Established Member
Joined
12 Oct 2004
Messages
2,696
Reaction score
521
Location
UK
What is the correct procedure for cutting that forked mortice? Do you cut two separate mortices and then remove the material between for hauncheon or do you cut it as a single mortice to a hauncheon depth and then cut two deeper trenches for mortices?Excavate the
Excavate the two mortices first, then clear the shallow section (groove) between the mortices to house the haunch. The reason for this is that you have lines marked to define the length of the mortices that guide the chopping out. If you remove the two marked lines of the mortices nearest the centre by cutting a shallower full length haunch accommodating groove they're no longer readily visible to help guide you as you chop the mortices.

Don't forget that forked M&Ts are often used, in part, because the width of the tenoned part is great enough that a small allowance has to be made for its expansion and contraction, similar to below. This 300 mm wide rail example is much wider than what you're making, but it illustrates the principal. In the below example the tenoned member was wide enough that I needed to allow for free movement of the lower tenon to ensure the rail didn't split if it shrank, which is the reason the lower tenon wasn't glued. Your part is narrow enough that you should be able to glue both tenons, but just make sure you allow for a bit of slop in the mortice lengths, 1 - 2 mm, for rail width change. Slainte.

M&TForked.jpg
 

tibi

Established Member
Joined
27 Nov 2020
Messages
588
Reaction score
227
Location
Slovakia
Excavate the two mortices first, then clear the shallow section (groove) between the mortices to house the haunch. The reason for this is that you have lines marked to define the length of the mortices that guide the chopping out. If you remove the two marked lines of the mortices nearest the centre by cutting a shallower full length haunch accommodating groove they're no longer readily visible to help guide you as you chop the mortices.

Don't forget that forked M&Ts are often used, in part, because the width of the tenoned part is great enough that a small allowance has to be made for its expansion and contraction, similar to below. This 300 mm wide rail example is much wider than what you're making, but it illustrates the principal. In the below example the tenoned member was wide enough that I needed to allow for free movement of the lower tenon to ensure the rail didn't split if it shrank, which is the reason the lower tenon wasn't glued. Your part is narrow enough that you should be able to glue both tenons, but just make sure you allow for a bit of slop in the mortice lengths, 1 - 2 mm, for rail width change. Slainte.

Thank you very much. I have learnt something new. Do I need to make both mortices longer to allow for wood expansion? Does anything change if I want to drawbore the tenons? I do not have such big clamps to do without drawboring and it helps me if my M&T joints are not super tight.

Thanks.
 
Top