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View livewire516's profile

Is poplar suitable for a Roorkee Chair?

by livewire516
posted 12-02-2018 08:09 PM


14 replies so far

View bondogaposis's profile

bondogaposis

5266 posts in 2654 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

View Redoak49's profile

Redoak49

3844 posts in 2291 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

461 posts in 206 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?

-- Phil Allin - There are mountain climbers and people who talk about climbing mountains. The climbers have "selfies" at the summit!

View 000's profile

000

2859 posts in 1202 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

1147 posts in 798 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"

View pottz's profile (online now)

pottz

4501 posts in 1287 days


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

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

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

View livewire516's profile

livewire516

29 posts in 163 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).

View TheFridge's profile

TheFridge

10844 posts in 1789 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

29 posts in 163 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 1202 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

10844 posts in 1789 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

5364 posts in 3546 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

6112 posts in 2514 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.

-- In theory, there is no difference between theory and practice. In practice, there is.

View livewire516's profile

livewire516

29 posts in 163 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).

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