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Adirondack Chair Class #9: Back rest assembly

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Blog entry by Betsy posted 950 days ago 2857 reads 1 time favorited 4 comments Add to Favorites Watch
« Part 8: Arm Supports - short lesson Part 9 of Adirondack Chair Class series Part 10: Arms rests »

Now we move onto the back rest assembly which is made up of parts A, B, C, D and E.

First off I want to say that this part of the blog was hard to write to make it clear. So if you have any problems with my explanations or have questions please feel free to ask. And for those of you who have PM’d me and said you plan to do this project in the spring, please feel free to PM me them if you have questions.

Also I apologize for the poor photography. I think I may have to have Degoose come over from the other side to help me take better pictures! Actually, if I’d open my wallet and get a better camera ….

We first start by cutting the slats. Part A is best made by using a 1×8 which is actually 7 1/8” wide.

Part A needs to be 7” wide so you barely need to cut just an edge off to hit your 7” mark. If you are using a new board (8’ long) you’ll need to cut it down to size. The final length to cut to is 33”, but cut it about ¼” longer so you can square up the other end.

You can see that my board has a few knots at both ends. So I have to decide which end to use if I choose to use this board. I can do one of several things.

1) I can use the end where the knot is solid and trim the edge without the knot to 7”
2) I can cut out the knot which makes me lose about 6” of my board that could be useful
3) Because the knot is not at the very end, I can use this end for the bottom of part A.

I would not use the end of the board where the knot is loose and likely to come out at some point in the life of the chair.

Be sure to use some support to hold the long end of the board while you make your initial cut at the chop saw.

Once cut to length, rip that 1/8” extra inch off of the board to make it the 7” needed.

The next step is to make the arc needed on the top of the board. Measure down from the top of the board 3.5” and in from the side 3.5” to make an intersecting point.

Set your compass on the intersecting point and swing the compass from side to side making your arc. You’ll see that you will cut off just a bit of the top making the arc. This allows you to cut the curve avoiding a flat spot on the top.

Cut the arc at the band saw, then sand down to the line. Once the curve is sanded go ahead and break the edges so the piece has a soft edge all around. That will complete Part A.

Parts B & C are the same width (2-7/8) but not the same height.

A 1×4 is perfect for these two parts, but you can also get two parts out of a 1×8.

Part B is 29” tall and Part C is 26.5” tall.

You’ll need two B’s and 2 C’s for each chair.

Cut the boards to the length needed at the chop saw and then cut to width at the table saw.

Learning Point – Normally you would stack cut both B’s and both C’s together, however, since you need 1 B and 1 C on each side of Part A it’s better to cut a B & C stacked together. That way when you cut the arc and sand to the line both parts will have the same exact arc.

Use carpet tape to secure Part C on top of Part B (the longer slat). Mark the arc on the top of Part C. Use the same method to get your arc measurement – either use the full size pattern or measure the compass size using a measure stick.

Cautionary note on carpet tape – the backing paper is quite slick. So when you take it off the tape, don’t let it fall on the floor. It’s so slick that it’s easy to slip on causing a fall.

2nd cautionary note on carpet tape – If your board has any bow at all the carpet tape will NOT hold the board flat – so make sure you use flat boards.

Since you are stacking a short board on top of a long board, be sure to draw your arc on the short board.
To mark the arc measure down 2 and 15/16” from the top and set your compass.

Take to the band saw and cut as before. Once cut keep the stack together and sand to the line. Mark the two pieces to keep them together on one side or the other.

You’ll notice that you take a little off the top of these parts like you did on Part A – this keeps you from have flat spots on your slats.

Now is a good time to break the edges of each slat so that they are smooth instead of a hard square edge from the saw.

Next you need to make Part D which is the bottom support piece. Part D is 3.5” wide by 19.5” long.

Let me digress a little as we approach Part D. If you have read my other post about making this chair – you’ll notice several things I’ve done differently with this chair. Yep – even old dogs can learn new tricks. One of the things I’m doing differently on this chair is that I’m not using pocket hole screws to attach Part D to the back slats (parts A, B and C). I think if I’m honest with myself, and you, I would say that I used the Kreg system to do this particular joint just because I really like using it. But when you step back and look at it, the pocket holes on this particular part is probably just overkill. It’s a tiny bit more difficult to do just regular screws but not that much that it warrants using the more expensive pocket screws.

Okay – back the task at hand.

You’ll notice that the 19.5” of Part D is the exact width of the inside dimension between the leg supports of your seat assembly.

It’s important that this part is the right size as it impacts how the whole assembly fits on the chair and the width of the arm assembly a little ways down the road. With that said——

Cautionary Note – if you measure the inside dimension and it comes up a little short or a little long – you’ll need to account for that measurement in making part D, and in the width of the slats (or the space between the slats) and in making Part F of the arm support. The final width of the back rest must be the same as the inside dimension of the legs.

Learning Point – Use the chair itself to mark the dimension of Part D. Be certain not to make Part D too tight – you do need a tiny bit of wiggle room to get the parts together at final assembly.

To use the chair as the measure simply put your roughed sized board with one edge just on the inside of one leg and then lay the other end over the leg and make a mark.

Learning Point – be certain that the ends of Part D do not have knots as it will be difficult to drive screws into.

Next up is Part E – the top support. This is one part that can also be made from a piece of scrap. Additionally, it does not have to be exactly 1.5” wide, so if you have a piece 1.25” wide you can use it with no problem.
Part E does need to be at least 18.5” long. No matter the width you have, use a small square to find the center point of the board.

On a project like this I don’t measure to the 1,000th’s of an inch. That’s not to say that I’m not accurate – but you don’t need to get out the fancy calibers. For instance if you know your board is 7” wide then half of that is 3.5. So set your square to 3.5 – make a mark then flip the square to the other side and it should line up with the line you made. If it does not, then simply move the body of the square up or back according to whether you over or under shot the 3.5 mark. I’ve taken a picture here to show what I mean – it’s exaggerated to make the point.

Just keep adjusting until you are pretty sure you’ve hit center.

Once you have determined the center of your board use the square the run the line the length of it. Sometimes it’s hard to hold the piece still and run the square and hole the pencil at once. My solution is to use the edge of my table saw as one anchor point and my six-packs abs for the other. That holds the board good and stead!

Now you need to clear some bench space as it’s time to assemble the back rest. You’ll need your ¼” spacers, two longish clamps and a scrap board that is 3.5” wide and at least as long as Part D.

First job is to find out how close you got to meeting that 19.5” mark. Lay out all the slats and put the ¼” spacers between each one. (Use one spacer at the top and one near the bottom. Place your Part D on the bottom edge of the slats.

Basically this is the set up

If your slats (with the spacers) is a little short of the 19.5” mark, use a few playing cards evenly distributed between the slats to make up the little shortness. If you are over the mark of 19.5” of Part D – you will need to take a little off of the outside slats.
Cautionary Note and a Learn Point
– if say you are ¼” too long. You want to cut 1/8” off two slats. That way your two slats are the same. If you take ¼” off just one slat – you’ll have a slat that will look off.

Now here is a lesson of how when you are trying to write a blog and tell someone else how you do something – you come up with another good idea. It just occurred to me that if you would cut your slats to width and before cutting your arcs check to see that they match the length of Part D, if you are too wide – you can take the little bit off before cutting your arc and that will ensure all your arcs are the same. Sitting here thinking about it, I don’t think it would make that much difference in the appearance of your arcs if you cut them before laying them out – but this is something to think about.

Digression over – let’s move on.

At this point you need to decide if you are going to put the entire back rest together and then paint or if you want to leave yourself some room to paint. Here’s a picture to give you an idea of what I’m saying.

I secure the two outside slats (Part C) and the middle slat (Part A) and leave the two inside slats (Part B) off to the side. To do the assembly you have to have all the slats in place you simply do not screw down the two Part B’s.

I prefer to put on Part E before tackling Part D. I just think it’s easier to manage the whole assembly when you have to turn over the assembly to attach Part D.

First up – we have to do a little measuring. On the BACK both outside slats (Part C) measure up from the bottom 23.5”. Then at that point, measure in ½”. This will give you the “box” where Part E will be attached.

Now flip your slats over (it may help you to remember how things go back together after your trip to the drill press if you make a carpenter’s triangle across all 5 slats – on the back).

On the FRONT of the slats measure up 3/8” from the bottom and make a mark. Then find the center point across the width of all four Parts B & C and make a mark at the bottom AND at about the 23.5” mark as well. You’ll use the mark at the top to determine where to place the screws in Part E. The mark at the bottom is where you will drill the pilot holes to attach Part D when we get there.

Next make a mark 1” in on either side of Part A and then find the center and make a mark at the bottom AND at the top. Because of the width of Part A – you need to use three screws to secure it to both Parts D and E.

Now using either a hand drill or your drill press drill the screw holes on the bottoms of each slat (ON THE FRONT). If you use a drill press for the part you can clamp a scrap board to the drill press table to make a fence so you will always have the right distance from the end. If I were going to be doing a multitude of these I would make a fence, but since there are only five parts – I pretty much eyeball it.

Now you need to get the locations marked for the screw holes on Part E. At this point I do use two clamps to hold my slats together so I can get an accurate mark. Lay Part E onto the slats so that the ends match up with the “box” you made earlier. Now – with the center marks you made earlier – make a mark on the side of Part E and carry it over to the top – which will mark the center points to make the screw holes.

Then it’s another trip to the drill press to drill the holes. Be sure that you don’t drill the screw holes too deep – you want them just deep enough to take the screw head and to leave enough room to hold a plug. About ½ the body of the forstener bit is plenty deep.

Once all the drilling is done go ahead and sand off the pencil lines and break the edges of the piece (easier to do now than when it’s attached.) Only break the edges of the TOP of the piece not the bottom that actually attaches to the slats.

Now onto the attaching of Part E. You’ll need to add some glue at this point to the back of Part E and a little onto each slat.
Cautionary point here
– If you intend to only attach the outside and middle slats to allow you room to paint, be sure NOT to put glue on those areas of Part E that will be left without a slat. Also, if you plan to attach all the slats at once and paint later you want to be careful with the glue and it’s hard to get squeeze out from between the slats.

You should now have your slats with the fronts down and the back up, with your ¼” spacers and two clamps lightly clamping the slats together. Place one end of Part E into your box and drill your pilot hole with the 3/32nd bit.

CAUTION CAUTION CAUTION – be very careful not to be all gung ho and drill all the way through the front of the slats. You just want to break through Part E and into the slat just a little ways.

What I do, is drill my first pilot hole, drive the first screw and use it as a pivot to place my other end.

So I do one end then the other and then the inside slats. I use the 1-1/4” screws here.

So now onto Part D. Depending on the clamps you used you may have to take them off at this point to flip the assembly over. I used my Bessey clamps so I have to take them off or they are too heavy. If you take them off, just be sure to put your spacers back in before you replace the bottom clamp (at this point – you only need the clamp at the bottom.

I use my table saw fence to my advantage here as well. Use two small clamps and attach the scrap 3.5” piece of material to the fence. Then lay the back rest with the top on the scrap and the bottom towards you.

Put some glue on the Part D and slide it under the slats, drill the pilot holes and drive the screws the same way as you did for Part E.

Congratulations you’ve finished the back assembly!

All that’s left is putting in your plugs (again going with the grain).

Once your plugs have dried sand them down flush with the slats.

Next up the arm assembly.

As always if you have any questions or comments please let me know.

-- Like a bad penny, I keep coming back!



4 comments so far

View lew's profile

lew

10002 posts in 2388 days


#1 posted 949 days ago

Super lesson, Betsy! You make the whole thing seem so easy!

Excellent photos, too! Glad they finally posted for you.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View nubby's profile

nubby

16 posts in 2029 days


#2 posted 946 days ago

Nice job , Betsy ! Very thorough. Great pics and instruction for any level of WW tha wants to build A-chairs. Your’s is by far the best instructions I have seen. I applaud you ladies doing woodwork. Before my wife became ill, she used to be in the shop with me all the time.
I, too make adirondack furniture and porch rockers. Working on some different designs right now that will sit a little higher for elderly folks.
Keep up the good work, Betsy !

-- Ben,in Dixie, www.roun-tuit.com

View rance's profile

rance

4130 posts in 1793 days


#3 posted 935 days ago

Betsy, I lost track but am back to watch the remaining steps. Thanks for putting this whole blog together. I know it is not easy.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Betsy's profile

Betsy

2913 posts in 2529 days


#4 posted 934 days ago

Thanks guys. I’m hoping to do the arm assembly and attach the best to complete the chair soon. Right now I’m trying to finish up a project for a 3-year old whose birthday is fact approaching!

-- Like a bad penny, I keep coming back!

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