Black Ash for strip planking

Discussion in 'Materials' started by nero, Mar 23, 2007.

  1. nero
    Joined: Aug 2003
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    nero Senior Member

    Has anyone some experience with black ash used for strip planking? I am considering it for the cross-bridge deck structure for my catamaran.

    From all the numbers on it out of the USDA Wood Handbook, it looks to be acceptable. Weight wise it will make the structure 18 kgs more over using cypress. This is not a problem. It is a lot stronger so, i could actually use a thinner planking schedule and perhaps come out lighter and stronger.

    On the odd chance that I build another boat, is this wood resistant to saltwater? Thinking of below the waterline use.

    I can get it from Iowa for under $1.50 bd ft. .... if the add is true.

    thanks
     
  2. alan white
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    alan white Senior Member

    Ash isn't a good wood below the waterline. Neither would it have the best strength to weight ratio. Encapsulated in epoxy, which it bonds pretty well to, it is possible to use it above the waterline.
    But apart from the fact you can get it cheaply, it has little going for it where weight matters. You will likely spend more to accomodate it than your savings in terms of sealing it.
    Cypress or spruce or fir would be better choices. Vertical grain fir is available everywhere as house decking material.
    40 lbs extra must mean there's not a lot of material required in any case. The difference between cypress and ash would be substantial, maybe 25-30%, so I'm guessing your whole structure would require no more than 40-50 board feet based on what you say the increase in weight will be.
    The right wood may then increase your cost by maybe $150.00US, which is not a bad price for saving 40 lbs on a multihull.

    A.
     
  3. nero
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    nero Senior Member

    Thanks Alan
    Cypress (that I am using for the hulls) is as published in the USDA Wood Handbook, 0.46 sp gr making 30 sq m. of 20 mm planking 276 kg. Black Ash is .49 sp gr. making the same .6 cubic m. 294 kg.

    VG fir? Douglas Fir is 0.48 so just slightly below Black Ash in weight. And DF is not as stiff or tough ... if I understand the numbers correctly.

    I will probably buy a 1,000 bd ft. (a little over twice the required) because of waste, choice, and there is always something I can use it for. Fuel to run to and from Iowa will cost $120.

    Will look at house decking material. Everything I have seen at lumber yards is pathetic in quality. Also kiln dried, not a good thing as I understand it from others.

    Can get Atlantic White Cedar also for a simular price. Found a willing sawer in Vermont. Never worked with this stuff and wonder if the side hardness (softness) of the wood will be prone to dents.

    Finding VG clear cypress is too frustrating.

    The wood is to be sheathed in uni and biaxel glass. This part of the boat is 80 cm of the wl at the lowest point.
     
  4. alan white
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    alan white Senior Member

    Doug fir comes in at 2.8 lbs. bd. ft in my reference. White ash at 3.6, no reference to black ash.
    Regarding atlantic white cedar... good stuff I've heard. As good as eastern white (eastern white is getting hard to find in clear wide boards).
    The cypress will be soft, like the fir, like the cedars. All soft. The glass will protect the surface.
    Fir is only slightly heavier than cypress. It is very available too, in vertical grain, and pretty strong. I would not worry about kiln drying with smaller dimension lumber such as 3/4" x 3". If epoxy is used for gluing and sealing,
    it will not matter. Keels are commonly built up out of the same stuff, layer by layer, and then glassed over.

    Good luck,

    Alan
     
  5. nero
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    nero Senior Member

    Yes white ash is much heavier sp gr of .60. Not at all the same plant as black ash ... not that I have seen or worked with black ash.

    From the USDA Wood Handbook:
    Black Ash Group
    The black ash group includes black ash (F.nigra) and pumpkin ash (F. profunda. Black Ash grows in the Northeast and Midwest, and pumpkin ash in the South.

    The heartwood of black ash is a daarker brown than that of American white ash; the sapwood is light-colored o nearly white. The wood of the black ash group is lighter in weight (basic specific gravity of 0.45 to 0.48) than that of the wite ash group (>0.50). Pumpkin ash, American white ash, and green ash that grow in southern river bottoms, especially in areas frequently flooded for long periods, produce buttresses that contain relatively lightweight and brash wood.

    Intersting enough under Sassafras, they state that it and black ash are easily confused. Perhaps another clue that black ash is good for boat building .... like sassafras.

    I have some old growth DF. The stuff is very heavy. It came from the floors in my grandfathers house when it was torn down. Built my daggerboads out of it. As I understand it the newer growth is less dense. They do not use it for decking here in Illinois. They sell a low grade of WRC.

    Perhaps I need to get some samples of each and test them.

    thanks for the advice Alan
     

  6. alan white
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    alan white Senior Member

    I've noticed Douglas fir varies in density quite a bit, and old growth is probably more consistently dense on average. My 34 lbs cu. ft. figure however came out of a 1962 edition of a boatbuilding manual. How old is old?
    One really nice aspect of using locally sold lumber is that you get to pick through the pile.
    New decking materials like pressure treated southern pine, plastic, and Spanish cedar (I think that's what it is) have obviously made Douglas fir decking less marketable----- the tongue and groove 1 x 4 used to be the only reasonable choice for verandas and covered porches here in the east, and so I've used it many times to patch or replace those old house decks.
    I've also noticed that hundred year old outdoor (roof-covered) floors have held up well, in spite of the T&G construction.
    If I were in your shoes, I wouldn't order modern DF decking, since you can't paw through it. I would imagine however that somebody has it in your neck of the woods since it is also used to match many old interior floors.
    I would look for pieces that are on the heavier side of average, eliminating the sappier pieces and also the very densest. Look for and avoid pitch pockets. I don't need to mention seeking straightness of grain and quarter-sawing, if indeed you do end up looking at DF.
    If you have access to old flooring, there's a lot of work involved in renewing it, but if it's free, I would weigh some pieces just for kicks, and just maybe your weight parameters will be met.

    Alan
     
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