Using Black Gum and Hickory in TF

RPowers · January 09, 2014, 11:02:04 AM

I am wanting to use a basic timber frame for my mill shed, and later for my work shop, in preparation for a TF/stone home I hope to build. I have some RO and WO on my 28 acres, but lots of black gum and assorted hickories. Is there any reason for not using these species in heavy wood construction? I know that neither are durable woods, but this would be in an above-ground weather-protected setting. I need beam to span 20' for the mill shed, and looking at DonP's calcs the #2 or better hickory was better than RO for the figures I needed. I have no experience with timber framing, so I'm wanting your advice. Would hickory work for rafters/beams, and black gum for posts? What do you think?

Thanks, RP

Thehardway · January 09, 2014, 02:42:24 PM

I would have no problem with the hickory if was of good quality and sound and you work it green. If it has a lot of mineral streaking, expect to be shapening your tools a good bit. The Black Gum I might have a second thought about. My experince with gum has been that it has a lot of internal stress and has interwoven grain. Its workability leaves a lot to be desired in my book. The gum will try to bind your saw and drill and be hard to get a clean tenon or mortice. You will fight with it considerably more than with red oak which works up beautifully. Gum will want to twist and warp and generally "gum" things up. Only plus it has is it can be very pretty. I would be using the red oak for posts with a healthy dose of borate solution and Diatomaceous earth around there bases.

That said, if your willing to fight with it just about anything would make a saw shed that will likely outlast the owner.

RPowers · January 09, 2014, 03:54:43 PM

Thanks for the reply. I have a question as well about definitions regarding wood characteristics. I am trying to use DonP's Beam Calculator where you can enter your own values. I Know what all of the values are except for the Maximum Fiberstress in Bending. Is this the same as Modulus of Rupture in psi for a given species, or something else? I'm not finding any test data that give a Maximum fiberstress in bending for various woods.

mesquite buckeye · January 09, 2014, 04:29:23 PM

Hickory is one of our strongest woods, with good shock resistance. It will last as long as you keep it dry and the termites out of it. Your house will also be more earthquake resistant. ;D

Jim_Rogers · January 09, 2014, 04:36:49 PM

Quote from: RPowers on January 09, 2014, 03:54:43 PM
Thanks for the reply. I have a question as well about definitions regarding wood characteristics. I am trying to use DonP's Beam Calculator where you can enter your own values. I Know what all of the values are except for the Maximum Fiberstress in Bending. Is this the same as Modulus of Rupture in psi for a given species, or something else? I'm not finding any test data that give a Maximum fiberstress in bending for various woods.

Max Fiberstress in bending is Fb in the formula. Modulus of Rupture are E in the formula, so no they are not the same thing.

Jim Rogers

RPowers · January 09, 2014, 05:08:17 PM

Jim,

I am looking at the data from this document. http://www.woodweb.com/Resources/wood_eng_handbook/Ch04.pdf It is the only thing I have found online that has values for Black Gum (Tupelo). Do any of the stats correspond to Fb or Fv on this? I have looked for something to tell me how to do some converstion or somthing, but in 3 hours of web sufting I've found nada. So if there is a website i should to go to find either the data or formulas to find this data I'd appreciate it. There is all sorts of info online for SYP or oak, but I'm wanting to determine figures for Black Gum, because I have it in plenty. This page has data, but being new to figuring load stresses on timbers I'm not able to figure up from down on some things. Thanks.

mesquite buckeye · January 09, 2014, 06:10:29 PM

I think you could use balsa wood for construction if you size it big enough. ;D

beenthere · January 09, 2014, 06:19:59 PM

QuoteMax Fiberstress in bending is Fb in the formula. Modulus of Rupture are E in the formula

Jim
Would Modulus of Elasticity be E ? I'm thinking so.

Some reading about the terms can be found in the Wood Handbook: Wood as an Engineering Material,

http://www.arb.ca.gov/cc/capandtrade/protocols/usforest/i_usfs_wood_handbook_2010.pdf

beenthere · January 09, 2014, 06:27:26 PM

RPowers
Doubt the species you want has been tested for those numbers.

But you might extrapolate numbers from other species that are in the tables for some ballpark figures.
Look at the clearwood strength properties for a species (like SYP) that have the stress grading numbers and see if the Black Gum properties relate.. then extrapolate.
Keep in mind that the grade plays an important role and will have an effect on performance.

Jim_Rogers · January 09, 2014, 06:53:00 PM

Quote from: beenthere on January 09, 2014, 06:19:59 PM
QuoteMax Fiberstress in bending is Fb in the formula. Modulus of Rupture are E in the formula

Jim
Would Modulus of Elasticity be E ? I'm thinking so.

Yea, I sometimes get those two mixed up.

stanwelch · January 09, 2014, 07:26:10 PM

Thehardway --
Why put diatomaceous under the base of the post? I assume the post will set on a pier.

Thehardway · January 09, 2014, 07:41:37 PM

It will deter and kill invasive insects.

RPowers · January 09, 2014, 08:39:59 PM

Quote from: beenthere on January 09, 2014, 06:27:26 PM
RPowers
Doubt the species you want has been tested for those numbers.

But you might extrapolate numbers from other species that are in the tables for some ballpark figures.
Look at the clearwood strength properties for a species (like SYP) that have the stress grading numbers and see if the Black Gum properties relate.. then extrapolate.
Keep in mind that the grade plays an important role and will have an effect on performance.

That sounds like the best starting point for me, thanks.