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Is poplar suitable for a Roorkee Chair?

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Forum topic by livewire516 posted 12-02-2018 08:09 PM 1974 views 0 times favorited 19 replies Add to Favorites Watch
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livewire516

120 posts in 1147 days


12-02-2018 08:09 PM

Topic tags/keywords: roorkee campaign chair ash poplar chair safari chair

I most concerned about whether poplar would be strong enough. Roorkee’s most common failure point seems to be the ~22” long, 1 1/8” diameter stretchers that end with tapered tenons (terminating at 5/8” diameter).

Talking to the only experienced woodworker I know in the flesh (I’m a nurse – and woodworking is a relatively recent hobby), he couldn’t understand why I would bother with poplar since the total amount of wood I’d need to purchase for the Roorkee isn’t all that much…and like most people he believes poplar to be ugly.

I personally like the idea of poplar, I grew up in what was historically Lenapi territory, where it was valued as canoe wood. I’ve seen beautiful examples, especially after “sun tanning” or exposure to oxalic acid. Also, I’ve never seen a painted Roorkee, so if it did turn out to be truly ugly I’d get to do something I’ve never seen before!

My only concern remains the stretchers with tenoned tapers. Could I fashion a dowel of adequate strength out of poplar? Or, am I creating unnecessary frustration/obstacles for myself, who is a beginner?

If I should steer clear of poplar, I assume I will make it out of ash, since it’s traditional.

If anyone is unfamiliar of the specific chair style, I thought this picture clearly shows the tapered tenon stretcher:


19 replies so far

View bondogaposis's profile

bondogaposis

6069 posts in 3638 days


#1 posted 12-02-2018 08:31 PM

Poplar is plenty strong enough, of greater concern is whether the grain is straight, and runs the full length of the stretchers. I agree with your friend, making a Roorkhee is a lot of work to only end up with a poplar chair.

-- Bondo Gaposis

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Redoak49

5419 posts in 3276 days


#2 posted 12-02-2018 09:33 PM

I think poplar is strong enough but a wood with more interesting grain might be better. Since you have a reason for wanting poplar,I would try it.

View Phil32's profile

Phil32

1613 posts in 1190 days


#3 posted 12-02-2018 09:54 PM

Actually the legs have more exposure than the stretchers. Are you going to shape them on a lathe? A wood with interesting grain would be my choice. Perhaps red oak?

-- You know, this site doesn't require woodworking skills, but you should know how to write.

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000

2859 posts in 2186 days


#4 posted 12-02-2018 11:04 PM

Poplar only has a rating of 540 on the Janka scale.
Alder would be better than poplar.

Walnut would be my choice though.

View TungOil's profile

TungOil

1384 posts in 1782 days


#5 posted 12-02-2018 11:30 PM

Maybe a hybrid? Use poplar for the main parts and switch to oak or ash for the tenons.

Popular is a bit soft, might not turn as well as ash.

-- The optimist says "the glass is half full". The pessimist says "the glass is half empty". The engineer says "the glass is twice as big as it needs to be"

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pottz

21354 posts in 2271 days


#6 posted 12-03-2018 12:01 AM

ill second the walnut as first choice,poplar would be one of my last choices.

-- working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.

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livewire516

120 posts in 1147 days


#7 posted 12-03-2018 02:15 AM

So although several folk here believe the strength should be adequate, (provided I ensure the pieces are milled to have good grain direction) – I am started to lean towards ash, simply because it’s bending strength is approximately 15k (comparable to Sapele or Walnut, whereas Poplar is around 10k). I won’t pretend to even know what unit of measure I’m looking at on these tables, but the only write up I've seen about a Roorkee built out of poplar had stretchers break twice (albeit from store bought dowels). It’s my first attempt on a chair, so I’d like to set myself up for success, and if it breaks and is poplar, I’ll be swearing myself for deviating with regards to wood species.

Phil – I myself don’t own a lathe – I have be debating fashioning the dowels with a round-over bit on my router table vs having my friend help me with their midi-lathe. I know the round-over solution won’t make a perfect dowel, but most of the stretcher would be covered and the business ends will be tapered afterward. Also, I’m more interested in the Kaare Klint Safaristol aesthetic, so I don’t plan on rounding the handles in the legs (another reason I’m looking toward using ash). The difficulty about accessing his lathe is that I’m based out of Boston and they live in Philadelphia, so although I head down that way regularly, I’d have to coordinate my travel schedule with their availability.

As for the turned taper and feet, I might be creating unnecessary stress for myself but I planned on rigging up a spindled jig to make a Craftsman-esque “Router Crafter.” (Before woodworking, my hobbies were working on cars and arduino/basic robotics so it actually was the mechanics of jig-making that got me interested in woodworking). I’ve already mocked up hand-cranked matched spindles with 608 bearings and angle-ground threaded rod (if all else fails, I got myself a lil’ rotisserie).

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TheFridge

10863 posts in 2773 days


#8 posted 12-03-2018 02:41 AM



Poplar only has a rating of 540 on the Janka scale.
Alder would be better than poplar.

Walnut would be my choice though.

- jbay

Seconded

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View livewire516's profile

livewire516

120 posts in 1147 days


#9 posted 12-03-2018 02:50 AM


Poplar only has a rating of 540 on the Janka scale.
Alder would be better than poplar.

Walnut would be my choice though.

- jbay

Seconded

- TheFridge

I’m a little confused. My understanding is that Janka ratings are for hardness, not strength.

View 000's profile

000

2859 posts in 2186 days


#10 posted 12-03-2018 03:55 AM

I m a little confused. My understanding is that Janka ratings are for hardness, not strength.

- livewire516


I think you are correct in your understanding.

View TheFridge's profile

TheFridge

10863 posts in 2773 days


#11 posted 12-03-2018 06:30 AM

That’s what she said

Edit: sorry. I can’t helo but to interject useless drivel. Bad habit of mine. Wouldn’t be bad if it actullay fit :)

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

View MrRon's profile

MrRon

6213 posts in 4530 days


#12 posted 12-03-2018 07:32 PM

For the cost differential between poplar and ash, I would go with ash.

View JayT's profile

JayT

6439 posts in 3498 days


#13 posted 12-03-2018 08:52 PM

You are correct about Janka being a rating for hardness. In most cases, a harder wood is also stronger, but not always. Modulus of Rupture is a measure of how much pressure a wood can take before breaking. For example, Doug fir is fairly soft, but very stiff and strong for it’s weight. It is much softer than a hardwood like cherry, but has a similar MoR, so would be just as resistant to breaking.

With straight grain and proper orientation, I would think poplar would be strong enough. Ash is much stronger, however, and would be a better choice, IMHO.

Hardware store dowels are not generally made from the best pieces of lumber. If the dowel had grain going off the edge, then it would definitely be a weak point and prone to breakage. Even with ash, you are going to need to make sure that the grain runs straight through the pieces to prevent shearing on a grain line.

-- https://www.jtplaneworks.com - In theory, there is no difference between theory and practice. In practice, there is.

View livewire516's profile

livewire516

120 posts in 1147 days


#14 posted 12-03-2018 10:43 PM


Hardware store dowels are not generally made from the best pieces of lumber. If the dowel had grain going off the edge, then it would definitely be a weak point and prone to breakage. Even with ash, you are going to need to make sure that the grain runs straight through the pieces to prevent shearing on a grain line.

- JayT

Agreed. Schwarz, who seems to have written more about making this style chair than anyone says: store-bought dowels are possible, but 90% of dowels in the bin wouldn’t make the cut. He’s also noted that the stretchers tend to fail when the belts are inadequately tensioned because it exposes the tapered portion of the tenon to the entirety of the stress (so that might have also been a cause of failure with the above mentioned chair maker, as that’s where his broke).

View bonobo's profile

bonobo

341 posts in 3343 days


#15 posted 04-28-2021 06:07 PM

This is and old thread but I figured I’d chime in for anyone researching wood for this project.

I think hardness is every bit important as bending strength. I made mine with soft maple dowels and beech and while it feels structurally up to the task, I’d go with harder woods if I were doing it again. The problem is that no matter how tight you make the straps, there’s still a force exerted on the legs to splay a tiny bit. With softer wood, the joinery gets compressed and it only takes a bit of deformation of the tenon and or socket to throw it off a perfect 90 degrees and then the pressure/deformation on the joint is even greater. It’s settling down now and doesn’t look too bad but I think poplar would be asking for trouble.

-- “Don't yet rejoice in his defeat, you men! Although the world stood up and stopped the bastard, the bitch that bore him is in heat again.” —Bertolt Brecht

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