spruce vs pine

Discussion in 'Boatbuilding' started by Charly, Sep 19, 2011.

  1. alan white
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    alan white Senior Member

    Use spruce for strength to weight superiority. Adirondack spruce is another highly considered species, similar to Sitka. Both are used for guitar tops, something I'm familiar with.
    If you are making up a squarish section, the term quarter-sawn is irrelevant. The reason is stability and shrinkage/expansion issues are far less important where there is so little width either way.
    Look for clear grain, lack of sap pockets, shake (internal cracking) and straightness. It is better to use some variety of spruce for its qualities of light weight and strength than to worry about other wood varieties. Even inexpensive spruce varieties such as our local Eastern white spruce (ultra cheap when sold as strapping (3/4" x 2 1/2"), when picked through, will suffice nicely so no need to get too extravagent with such expensive species as Sitka, etc..
     
  2. nwahs
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    nwahs Junior Member

    i would not call 3/4 x 2-1/2 squarish, you might think there no cup in it??? put it on a big belt sander, it might not be as flat as you thought.
     
  3. PAR
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    PAR Yacht Designer/Builder

    Nwahs, you miss read the comment by Alan. I'll second the use of white spruce. I can get it here cheap too and I make spars out of it all the time. It's lighter then Sitka, but also slightly weaker and has the other issues, that are typical of these woods, such as fastener holding ability, etc.
     
  4. tunnels

    tunnels Previous Member

    Have used Cypress for longtudinal girders inside a fibre glass rescue boat more than 25 years ago and its still going strong . Timber Was cut to shape and sanded etc then Glassed well after sealed with resin ll sides before installing into the hull It is stringy and will bend a mile before breaking, Buts its never a clean break . :p
     
  5. nwahs
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    nwahs Junior Member

    a few wood strength examples,

    sitka- horz/ shear (wet) 1271 (dry)1495
    comp/ perp (wet) 223 (dry) 335
    comp/ parallel (wet) 960 (dry) 1200


    ok white spruce
    horz/shear (wet)1222 (dry)1438
    comp/ perp (wet)283 (dry)425
    comp/ parallel (wet)1120 (dry)1400


    long leaf pine
    horz/ shear (wet) 1857 (dry) 2185
    compress/ perp (wet) 377 (dry)565
    comp/ paralel (wet) 1440 (dry)1800

    doug fir horz (wet) 1417 (dry)1668
    comp/ perp (wet) 417 (dry)625
    comp/ para (wet) 1360 (dry)1700


    sorry your yellow pine, and cypress are not listed in my reference book
    ive have personally tested none, and endorse none.

    i find personlly stronger woods tend to come at a cost of weight.
    i certanly would not skimp on strenth, weight& cost ratio well its your choice

    as to your actual question on epox bond, i have heard no probs but would make sure resin and moisture were decent in what ever you select
     
  6. Charly
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    Charly Senior Member

    Thank you all for the inputs

    The "home depot method", or selecting certain boards and then ripping the good stuff out, scarfing and then laminating, has worked well for me so far. It is more labor intensive, especially when building up wider stock, because most of the good stuff I have found comes from two-by stock, which means ripping and planing the boards down to proper thickness. On my cheap table saw, it is difficult to get a flat accurate rip from a two-by set on edge, therefore the final planing step is necessary. No big deal, just more work. Anyway, at this point in the build I have more time than money;)

    I have been concerned about having too many different short pieces, IOW too many scarfs, in any given length, not so much as a strength issue, ( I suppose a properly glued up homeade "gluelam" would be plenty strong) but of weight. So there is a tradeoff.

    I have some feelers out, and will report back what prices I come up with for 16 pieces of 12 foot long 1x6 sitka. I can get #1 select pine here for less than .50/linear foot. If I go that route, I will wind up with three scarfs per board (final laminated board being two 3/4 by 2-1/4 x ~22-1/2 feet). Of course, this would have to be vetted with the designer, and possibly downsize them a bit to make the weight gain less of an issue. I will also try and check up on the cypress. It is plentiful here too.
     
  7. alan white
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    alan white Senior Member

    I understood the section was laminated to 1 1/2" x 2 1/4". It's the finished section after gluing whose dimensions must remain stable, not the individual laminations.
    Quarter sawn means either the type of cutting (to achieve the greatest number of growth rings on the widest face), or the description of any "quarter-sawn" oriented piece culled from plain sawing.
    The term comes from the initial quartering of a log, after which each quarter was rotated 45 degrees to recut as close to 90 degrees from the growth rings.
    Plain-sawn wood shrinks and expands up to twice as much as quarter-sawn wood. Quarter-sawn wood is therefore more desirable almost anywhere on a boat, especially planking and decking, but also anywhere where widish boards are used such as interior panelling. The less a board "moves", the better in terms of the caulk staying water-tight.
    Cupping is usually a result of uneven contraction or expansion between the two sides. Shrinkage or expansion alone is far easier on the wood if both sides take on and give off moisture at the same rate. Coatings such as paint or varnish slow down absorbtion rates. If both sides are coated similarly and kept at about the same temperature cupping will not occur.
    Wide boards on a boat ask the most of the wood to perform well. The marrower the boards required, the less finicky one needs to be about the drying process, but for the best results the widest boards should be air-dried quarter-sawn wood. Wood destined for being buried in an epoxy-encapsulated assembly need only be dry and narrow of width (under 2 1/2",e.g.). There ought to be no measurable expansion/contraction in such pieces once the boat is built, and even if water did accidentally get into such an assembly, the pieces within are too narrow to favor grain direction anyway.
     
  8. Easy Rider
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    Easy Rider Senior Member

    I thought Sitka Spruce was rot prone and not considered boat building material. We have unlimited Sitka Spruce here but we're in SE Alaska.
     
  9. CatBuilder

    CatBuilder Previous Member

    It shares those characteristics with Okoume, which is another of the top boat building woods.

    People have overlooked the rot potential in these very stiff/strong (for the weight) species, since they are to be thoroughly encapsulated in epoxy.
     

  10. PAR
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    PAR Yacht Designer/Builder

    Sitka's strength to weight ratio, has been highly praised in spar making for generations. As such, isn't as prone to rot, being on deck or well aloft. Only fairly recently has epoxy encapsulation been employed in this regard.
     
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