Subject: RE: baidarka Which Spruce?
From: Peter A. Chopelas (pac@premier1.net)
Date: Mon Apr 03 2000 - 21:30:51 EDT
Wayne,
White pine does not show up in either USA or Canada species list for SPF,
it would be grouped with "White Woods" (species stamp WW) but would
include any true firs, spruces, hemlocks or pines; Idaho White Pine is
stamped "IWP". White could also be listed separately as "Eastern White
Pine". And there are a number of mills that do separately identify
individual species with their own mark, but nothing listed in the Western
Lumber Grading Rules approved by the Board of Review, American Lumber
Standard (which is where all this information came from)
As far as strength vs. weight goes you might find this info interesting:
Allowable Stress
Weight(LB/CF) Bending (psi) strength /weight ratio
Doug Fir 31.2 2400 76.9 (very stiff)
Eastern Softwoods 25.5 1875 72.3 (includes eastern spruces- Black, Red,
and White)
Eastern White Pine 22.5 1875 83.3
Sitka Spruce 26.8 1800 67.2
Southern Pine 34.3 2850 83.1 (very stiff)
Spruce-Pine-Fir(s) 22.4(least in grp)1950 87.1
Western Red Cedar 19.3 1725 89.3
This is for 4 or more growth rings per inch (a lot more would be stronger
but would also add weight) with small well spaced tight knots. Moisture
content 19 percent or less. A comparison of tensile strength and
compression strength will yield very different results, as will fastener
holding strength. It just depends how you need to load the wood in each
application. This is for larger sizes (2x2 or 2x4), you will find a clear
piece of strait grained wood in stringer size will be stronger, but this
serves as a comparison.
It is interesting to note that the strongest wood does not have the best
strength to weight ratio, also interestingly hardwoods such as maple or oak
are not any stronger, but will weight a lot more. Hardwoods are superior
in cross grain compression, so they would be good for rub strips but add a
lot of weight without adding any more strength.
It appears if you select the lightest wood from the SPF stack you could get
a good strength to weight ratio but you may not have the lightest for that
group in your local lumber yard. Also to take advantage of the best
strength to weight ratio wood you have to optimize the size to the strength
requirement, and that may not give you the best fastener strength (for
example often I will call out a bigger size than I need for bending
strength because I need to get enough fasteners into each end to handle the
loads).
Again I would just use what is available and inexpensive, if you want the
lightest wood for cheap, just see which in the stack "feel" light (though
you still do not know what you are getting).
Peter
-----Original Message-----
From: wayne steffens [SMTP:wsteffen@mr.net]
Sent: Monday, April 03, 2000 5:50 PM
To: baidarka@lists.intelenet.net
Subject: Re: baidarka Which Spruce?
Peter, thanks for that voluminous amount of info. Shouldnt white pine be in
the spf somewhere, or is it only sold as such? I know we've got a bit of
that in our lumberyards.
The reason I would like to find spruce is not to be authentic. Tne reason I
would like to use spruce is to be light. Cedar is just as light or lighter
but not as strong, from what I've heard. Rot resistance has been discussed
recently, and I dont give a hoot about that because I dont think it matters
for a boat that spends most of its time out of the water. The fact that the
people who originally built Caribou kayaks chose spruce and I am too is
mostly coincidence. They didnt really have much choice because spruce is
the dominant long driftwood in their area. It just so happens its a fairly
good wood to use, too. I would like to be authentic in the sense that most
Caribou kayaks are very long, and weight was (and is) a consideration when
building one. I dont think I can build a lighter kayak with other readily
available woods. I may use cedar for the ribs for the same reason, although
ash is stronger and readily available. Again its a coincidence that cedar
was the rib of choice for the original builders. If there was an even
lighter, cheaper, readily available wood that was suitable for ribs, I
would use that instead. If I just grabbed the first clear boards I saw from
the SPF pile when looking for gunnels, I would probably end up with a boat
that would me much heavier than it need be. There was a considerable weight
difference in the 1x4's I looked at. Most of the lighter ones looked like
spruce.
BTW, I Built a paddle out of Doug fir and dont plan on doing it again as
long as lighter woods are available. Its strong as heck but now the paddle
comes in handy only when I need to bang crusty creosote out of the wood
boiler chimney, or to prop the woodshed door shut during gales (like right
now). I know other people have used it succesfully though.
You're right that people shouldnt overlook the other choices, and I
wouldnt hesitate to use another lightweight wood if spruce couldnt be
found, especially with a smaller boat. In fact, I might have already done
that with the Aleut boat I built. The wood is not as light as some known
spruce boards I have, but the boat will still be under 40lbs when finished.
Of course its also 11 feet shorter than the Caribou will be. ;-) and it has
much smaller and shorter gunnels. But I found it by looking for the best,
lightest, straightest grain, most "sprucey" (and cheapest) wood I could
find. These other boards that might be spruce or might not, while very
nice and probably just fine for my use, are not cheap. They will cost me
$40 per boat. If I hadnt asked my canoe friend what they were, I probably
would have just used them. However, aspen AFAIK, is not known for its use
in boatbuilding, but is well known for its use in such unstructural things
as toothpicks and pulp. I'm not convinced they are aspen though, so I may
use them yet.
The whole concept of authenticity is elusive to me, and I dont pursue it
that religiosly. What is authentic? Is it better? Better than what? If an
"authentic" boat has nails in it, is it no longer authentic? If I build a
boat with nothing but wood, hide and sinew, is it authentic or a replica?
The decisions on what materials and processes to use are different for
everyone, as they always have been. Weight, strength, suitability and
availability have always been considerations, and now we have to throw cash
into the equation too. I think many of us are on this list because we have
an interest in building semi-authentic boats or using "traditional"
materails and processes. In my case the decision to go "authentic" or
"practical" "lighter" or "least expensive" is often completely arbitrary
and based on my mood at a particular moment. I had planned to use no glues
in my Aleut boat, but when it started to drag on and I was getting
impatient I slapped some epoxy on in a couple places. So why didnt I want
to use epoxy? Mostly because it sounded more fun. I had planned to use
canvas because its a natural fiber, then one day I compulsively decided
nylon would be a lot more natural (and sexy). My reasons for building are
very different from the original builders. Sometimes I'd rather walk
someplace and sometimes I'd rather drive. I know that Caribou kayak
builders would walk the extra mile to get cedar for ribs rather than use
willow, if they had the time to do so. I'll bet if the caribou had arrived
and they needed a boat, they wouldnt hesitate to use willow.
Many of us take great pains to sand, polish and finish our "authentic"
frames. Is that authentic? Not in most cases, but it brings pleasure to the
builder so its worth the effort to some. Me, I'd rather not. I might
however spend hours playing with bone parts, moosehide, and even blood
glue, not so much to be authentic, but because it might be fun. In many
ways, I dont think any of our boats are really authentic no matter how hard
we try. In other senses though they are very authentic, in that we all
build using the best materials available for our own purposes (which is
usually pleasure, rather than a hunting tool) and modify the designs to our
own ends. Any "traditional" authenticity or lack thereof is due to whether
I feel it would be more pleasureable at any particular point in time. OK,
that is QUITE enough babbling from me. ;-)
Wayne
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