Wood equal to or better than Douglas Fir?

Discussion in 'Materials' started by abosely, Jul 1, 2015.

  1. abosely
    Joined: Mar 2015
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    Location: Big Island Hawaii

    abosely Senior Member

    As it turns out finding clear Douglas Fir on Big Island is turning out to be difficult. The clear 4x8 beams aren't readily available currently.

    I saw it mentioned that 2x12 Douglas Fir when picked through can yield some straight grain material. Is that realistic? I don't mean getting all I need in one trip but going through it when a new comes in each time.

    I need a lot of 1"x3" & 1"x2" actual dimension lumber. Plus most of the other wood is 1" actual thickness.

    I can re-saw & plane 1.5" down to 1" if finding 2"x12", 10" or 8" can be found. Doesn't need to be vertical grain, just straight grain and fairly clear, I can cut out the knots.

    Is there another wood that would be as good or stronger than Douglas Fir that might be available from either box stores or local lumber yards?

    Any ideas or suggestions?

    Cheers, Allen
     
  2. alan white
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    Location: maine

    alan white Senior Member

    What part of the boat is the wood for?
     
  3. abosely
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    Location: Big Island Hawaii

    abosely Senior Member

    Stringers, deck supports, 4- 1" pieces laminated for keel, part of bulkheads...

    It's a Wharram Tangaroa Mk IV Catamaran. Not to be used for masts, will use Sitka Spruce for them.

    One other possibility is i can get free trees-logs here. We are setting up a small sawmill for milling lumber and a planer for our houses. But don't know how to pick a tree species for lumber.

    I can lots of Australian Blackwood (Acacia melanoxylon) and Albizia Chinensis
    (Chocolate Heart Albizia).
    I looked them up on the wood Database and their are close to Douglas Fir, but don't know how to compare/judge them.

    There other Australian & Asian trees here that can be used for lumber. Just don't know how to tell which would be correct to use.

    Cheers, Allen
     
  4. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    Southern Yellow Pine is stronger than DF and is straight grande. Do not know availability
    where you are. It has the same durability as DF. Denser than DF.
     
  5. abosely
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    Location: Big Island Hawaii

    abosely Senior Member

    Big Island Hawaii. Is it much heavier than Douglas Fir?
     
  6. rasorinc
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    Location: OREGON

    rasorinc Senior Member

    Yes, go to the Glen-L Marine site At bottom of opening page they list foreign and US boat building lumber. It lists weight.
     
  7. abosely
    Joined: Mar 2015
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    Location: Big Island Hawaii

    abosely Senior Member

    It looks like I can get #1 Southern Yellow Pine 2x12 here. 2x12s would be a good size for re-sawing down the needed sizes. I can plane it down to 1" actual thickness.

    The Wood Database lists Douglas-Fir:

    Average Dried Weight: 32 lbs/ft3 (510 kg/m3)
    Specific Gravity (Basic, 12% MC): .45, .51
    Janka Hardness: 620 lbf (2,760 N)
    Modulus of Rupture: 12,500 lbf/in2 (86.2 MPa)
    Elastic Modulus: 1,765,000 lbf/in2 (12.17 GPa)
    Crushing Strength: 6,950 lbf/in2 (47.9 MPa)

    Southern Yellow Pine as Longleaf Pine

    Average Dried Weight: 41 lbs/ft3 (650 kg/m3)
    Specific Gravity (Basic, 12% MC): .54, .65
    Janka Hardness: 870 lbf (4,120 N)
    Modulus of Rupture: 14,500 lbf/in2 (100.0 MPa)
    Elastic Modulus: 1,980,000 lbf/in2 (13.70 GPa)
    Crushing Strength: 8,470 lbf/in2 (58.4 MPa)

    So Southern Yellow Pine is heavier but stronger. Could the 1" thick in DF be reduced if made in Southern Yellow Pine? Maybe keep the main structural components like the stringers in 1"x3" but some of the others like deck supports could be reduced some?

    If getting stronger and more rot resistant wood at least that helps offset the worry about the added weight some. I do want her strong & tough, like an expedition type boat. :)

    It looks like about 29% heavier than DF. I'm not sure how significant that is yet without adding up how much lumber is needed.

    Also I can pick thru the lumber and select the lighter pieces too. That would help some I guess.

    Edit: I need 500 board feet of 1"x3" material. According to Glen-L website D-F is 2.83 lbs/bf %00 x 2.83=116lbs, SYP is 3.42 lbs/bf x 500=140lbs, so about 24lbs heavier and this is a pretty big chunk of the lumber material. So I guess maybe not too bad of a weight penalty? At least i gain some strength with the weight penalty.

    I hate to add unnecessary weight. I want to keep her as light as I can.

    Thoughts, ideas?

    Cheers, Allen
     
  8. Steve W
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    Steve W Senior Member

    You are right to be concerned about added weight, every pound you add to the structure is a pound of payload you can not carry without sinking below your lines. Yellow pine would be a good option since it is readily available but you would probably want reduce the scantlings, I would consult with the designer for his take on this.

    Steve.
     
  9. Jamie Kennedy
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    Jamie Kennedy Senior Member

    I could not find Albizia but the Australlian Blackwood looks very promising. It's crush strength was better than Douglas Fir but not as good as Yellow Pine, but 40 psf vs 41. Beautiful looking wood though, so it might be a shame to paint it, but aren't they all. I think it would make sense to use some locally grown wood if there is anything that is grown for construction. If it can be used in Hawaii for construction there is a good chance it will be suitable for marine use.

    googled and found this publication...
    www.ctahr.hawaii.edu/oc/freepubs/pdf/RM-7.pdf
     
  10. Jammer Six

    Jammer Six Previous Member

    Most hardwoods.

    Personally, after a career in construction and miles of doug fir, I detest the stuff. When I think of it, I think of pitch and jammed tools.
     
  11. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There's a huge difference between construction grades of Douglas fir and select stock. All the confers will offer pitch, pith, etc., though when boat building, we usually don't employ these sections of a piece, but as rafters in someone's house, the typical carpenter just doesn't care and nails up what they have on sight, defects and all.
     
  12. Jammer Six

    Jammer Six Previous Member

    You need to meet more carpenters, PAR. And you need to know more about how wood is worked professionally, if you're going to comment. No one around here uses doug fir for rafters. It's a really bad choice, for a number of reasons.

    I would point out the differences between what you've written in this forum and wood working, but I'm quite certain you're not typical of boat builders, and I don't wish to tar them with your brush.

    I understand your dismay with residential contractors. I've seen many, many of you. A lot of homeowners have been ripped off by contractors, simply because they didn't know how to avoid it. You're not alone.
     
  13. FMS
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    FMS Senior Member

    It's not an issue of being ripped off by contractors.

    Contractors don't spend the time or effort to select every individual stud, joist, and rafter while rejecting 95% of the boards because it's unnecessary. Customers don't ask for it nor would they pay for that.

    A house isn't weight sensitive as a boat is. Structural members are nailed in place or glued with low grade adhesive, compared to boat construction. Oversized lower grade rough framing allows space for insulation, duct runs, sound isolation and are unseen. Code expects rough framing to be rough and sizes accordingly.

    Boatbuilders get away with picking the stacks for the best 5% because there are few of them. Only using the best 5% of lumber in home construction would result in a large cost increase.
     
  14. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Exactly, I've made no point against contractors, though you Jammer seem to have a need to react defensively.

    I'll bet my knowledge about wood and marine construction, is far in excess of yours, based on your participation here, which can at best be described as eclectic.

    The choice of Douglas fir for a rafter has much more to do with appropriate sizing than the species. This is engineering 101, you should try it some time. As to "taring" other boatbuilders with my workworking brush, well I'll stand on the dozens of active builders I do know, have worked with and will continue to work with. You see there's a difference between you and me Jammer, many of the participants here actually know me, some have worked for or with me, some are customer or clients, others friends, so please give it a shot and lets see where my tar incrusted brush falls.

    Back to Douglas fir, it's a fine species, though some familiarization is helpful to pick out the best or better examples in a lot. It's not the hands down choice for everything, but it can be used in many applications. It's available in long, clear lengths, it machines well, though finishing can be a chore, particularly if it's a peeled veneer, like that used in plywood, but these issues are simply an idiosyncrasy of the species, just like any other species good and bad points.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    I always marvel at the strength-for-weight of what is called "Oregon Pine" here ( never heard of it being called Douglas Fir here, a lot of what finds a market locally now would be grown in New Zealand). I have an old extension ladder that is about 60 years old made from it ( except the rungs, which are some kind of Eucalypt, probably ironbark). I can only assume there is no common timber that betters it for these purposes. And talking about it being available in long lengths, a race-course grandstand in these parts has Oregon beams in the structure that have been up for 100 years, and appear to be around 70-80 feet, and maybe 18" x 12", massively impressive. Those came straight off a steamer from the US west coast.
     
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