Planking and epoxy

Mike I can save you the trouble of a case of 5200 and hand cramps squirting it into 1/2" wide seams. There's a nice ferro hull already for you, not far from here. Clipper bow, wineglass transom, 5' draft on a 40' hull. She'd make you a lovely home afloat and you could fit her out in time for spring break, right?

 

Hmmm, sounds attractive.

Could I get the whole junk on a flat pontoon for towing her to Europe?

You know thats cheap, towing is always slow and costs near to nothing.

 

I have always read that you could add some concrete to a boat to make it more stable, [one of those books on design I think] but a boat with built in balast displaced across the complete hull, Man why didn"t I think of that. Can you arrange some of those spring break girls from around Daytona for me for that real maiden voyage?

 

wind loading on an open window is definitely a dynamic load but overall I see your point that its hardly comparable to a boat, although there are other situations in which Ive used this material that were subjected to cycled loading ( built a huge set of spiral steps out of the stuff for the fat family a while back, I swear not one of these folks right down to any of the three kids or the dog weighed less than 300 lbs)

Also same can be said concerning availability for yellow pine, the original stands were decimated and for a time was considered commercially extinct. Most of what is used today and referred to as yellow pine is more likely to be short leaf or loblolly pine neither of which holds a candle to long leaf in rot resistance.

I just got a few winks after a long and grueling night of new years festivities but I did whip up a short comparison of four species typically used in planking

long leaf and short leaf yellow pine ( the good stuff and none to easy to get anymore )
old growth western red cedar ( also getting hard to find )
yellow poplar ( Tulipfira ) I can get mountains of the stuff and dirt cheap

I thought Ild compare several of the more common available materials that I might consider for planking my build. I omitted Douglas Fir because of its inconsistency, its habits of splitting, its tendency to warp and twist over time and its low resistance to decay.

I compared four species, long leaf yellow pine, short leaf yellow pine, yellow poplar and western red cedar. For my purposes Ill be needing roughly 3000 bd/ft so costs will be determined with that in mind.

what I found that was pound for pound and dollar for dollar Poplar is a clear winner with two considerations in mind. One that when used as a diagonal planking the same number of layers are used in each material so as to keep the cost of glue comparable. Two that the thickness of the planking is adjusted to maintain similar strength comparisons and as compared to long leaf yellow pine do not exceed in weight

Ok I got curious about how the actual numbers stack up so I thought Ild dig em up from several sources and lay them out side by side, then compare them by weight and cost

from wood a manual for its uses in wooden vessels ( US Navy )

weight ( specific gravity ) yellow pine .58, short leaf .51 poplar .40, cedar .33

fiber stress at proportional limit long leaf yellow pine 9,300 short leaf yellow pine 7,700 poplar 6,100 cedar 5,300

modulus of both rupture and elasticity yellow pine 14,700 and 1,990 short leaf 1,280 and 1,760 poplar 9,200 and 1,500, cedar 7,700 and 1,120.

static bending stress to both proportional limit and maximum load yellow pine 2.44 and 11.8 short leaf 1.93 and 11.0 poplar 1.43 and 6.8 cedar 1.44 and 5.8

impact bending at proportional limit in lb/sq inch and impact height to failure yellow pine 15,400 and 34 short leaf 13,600 and 33 poplar 13,500 and 20 cedar 8,600 and 17

shear parallel to grain and hardness parallel to grain yellow pine 1,500 and 870 short leaf 1,310 and 690 poplar 1,100 and 450 cedar 860 and 350



in an effort to determine the accuracy of my primary source I thought Ild look at another source suggested by another member



from the wood explorer

weight ( specific gravity ) yellow pine .55 short leaf .44 poplar .38 cedar .33

bending strength yellow pine 14,117 short leaf 12,834 poplar 9,435 cedar 8271

crushing strength yellow pine 941 short leaf 804 poplar 490 cedar 485

hardness yellow pine 942 short leaf 676 poplar 432 cedar 337

impact strength yellow /inches pine 31 short leaf 32 poplar 23 cedar 17

shear strength yellow pine 1,633 short leaf 1,362 poplar 1045 cedar 945

stiffness yellow pine 1,971 short leaf 1,715 poplar 1,506 cedar 1,189

work to max load yellow pine 9 short leaf 8 poplar 8 cedar 7

Par was right, southern yellow pine is superior in all regards when compared on a per board foot basis, IE by volume. However since weight is also a consideration and volume isn't nearly as much I also would like to take a look at what happens if we compare the four species by weight and then also by cost. The reason Im willing to make this consideration is that the thickness of the finished planking is not really all that relevant, as long as the thickness of each individual plank does not inhibit its application to the curvature of the molds, and the final weight of the structure is equal, a few % of volume is irrelevant in this instance.



so what is the superior wood by weight



ok not a great way to measure superiority in building characteristics as some measurements translate better than others but still some good food for thought.

Im going to look at the average weight of each material as derived from both data sets and compare that to a theoretical sample piece of similar weight and suggest that if a one sq/ft piece of yellow pine one inch thick weighing 3,17 lb was compared to a equal mass piece of poplar and also yellow pine what would ( roughly ) the resulting strength characteristics of each be based on its additional thickness. Yellow poplar would be 1.43 inches thick and cedar would be 1.71 inches thick to obtain the same mass sample of all three species at 12x12 inches when compared to a 1 inch thick piece of yellow pine. Now I realize that there is some gaping flaws in comparing these data points this way but for the most part its just a theoretical look at strength vs mass as opposed to strength vs volume, the later of which is what both the data sets are based on.

averaging the two data sets
yellow pine 38 lb/ft3 short leaf 34 lb/ft3 poplar 26.5 lb/ft3 cedar 22.25 lb/ft3

long leaf yellow pine is 18% hevier than its short leaf cousin, 43.3 % heavier than poplar and 71% heavier than cedar so how do the numbers compare to an equal weight of each material. Ill convert the wood explorer data set to reflect and equal mass instead of an equal volume and then see how that stacks up against the US navy numbers

all numbers are converted based on an equal weight of material

bending strength short leaf 15,155 poplar 14,143 yellow pine 14,117 cedar 13,520

crushing strength short leaf 945 yellow pine 941 cedar 829 poplar 702

hardness yellow pine 942 short leaf 798 poplar 619 cedar 576

impact strength short leaf 38 poplar 33 yellow pine 31 cedar 29.5

shear strength yellow pine 1,633 cedar 1,616 short leaf 1,607 poplar 1,497

stiffness poplar 2,158 short leaf 2,024 cedar 2,033 yellow pine 1971

work to max load cedar 11.97 poplar 11.5 short leaf 9.44 yellow pine 9



now the US navy numbers



fiber stress at proportional limit yellow pine 9,300 short leaf 9,086 cedar 9,063 poplar 8,741

modulus of rupture short leaf 1,510 yellow pine 14,700 poplar 13,184, cedar 13,167 .

modulus of elasticity poplar 2,149 short leaf 2,077 yellow pine 1,990 cedar 1,915

stress to proportional limit cedar 2.46 yellow pine 2.44 short leaf 2.28 poplar 2.15

stress to maximum load short leaf 13 yellow pine 11.8 cedar 9.92 poplar 9.74

impact bending at proportional limit poplar 19,345 short leaf 1,604 yellow pine 15,400 cedar 14,706

impact height to failure short leaf 39 yellow pine 34 cedar 29.07 poplar 28.66

shear parallel to grain poplar 1,576 short leaf 1,545 yellow pine 1,500 cedar 1,471

hardness parallel to grain yellow pine 870 short leaf 814 poplar 645 cedar 598

by weight Poplar is approximately equal to long leaf yellow pine and only slightly inferior to short leaf pine
the comparison does show that poplar can hold its head up in a pound for pound contest with the yellow pine brothers



cost



what is the cost of the 3000 bd/ft Ill be needing and what would that cost be once adjusted to obtain similar strength characteristics based on going back to the original numbers and considering the percentage of increase to achieve equality for each material

I buy dead clear straight grained poplar from the mill for less than $1 a foot $2 a foot if I buy it here in town

I seem to remember paying about $6 a foot for cedar dead clear old growth straight grain but its been a long time since I bought any so that may be way off ( feel free to chime in with your best price ). Ill go with $5 just to be as fair as possible.
long leaf yellow pine is staging a comeback but is still pricey, Ive not bought any except as flooring in a while but even at that its about $2 a foot for #2 common. Im going to say that dead clear straight grain select is bound to be $4 a foot but just to be fair lets call it $3 just in case anyone has a good handle on some. also Im going to consider short leaf and long leaf at the same cost since both are grouped as yellow pine

per board foot and total for 3000 bd/ft


red cedar $5 = $15.000

yellow pine $3.00 = $9,000

poplar $1.50 = $ 4,500


Red cedar Ild likely be paying more like $6 or 7 per ft. Either of the yellow pine brothers, a miracle price, if I could find it, Ild likely be paying more like $5 per ft. Poplar I estimated high just to try and keep things fair, I can buy this material from the mill for <$1 a foot and off the stump for pennies if I want to just slab and dry it myself



cost per 3000 bd/ft

adjusted for modulus of elasticity

poplar = $4,500
long leaf yellow pine - 33% = $6000
short leaf yellow pine - 17% = $7,470
red ceder +.33% = $20,000


adjusted for impact bending

poplar =$4,500
long leaf yellow pine -14% =$7,740
short leaf yellow pine -0.74% =$8,933
red ceder +57% =$23,550


adjusted for static bending to proportional limit

poplar =$4,500
long leaf yellow pine -67% = $2,920
short leaf yellow pine -35% =$5,850
ceder -0.69% =$1,490


adjusted for shear parallel to grain

poplar =$4,500
long leaf yellow pine -36% =$5,760
short leaf yellow pine -19% =$7,290
cedar +28% =$19,200


not much comparison there
other than in static bending and the thing to remember is that by weight poplar is only 13% lower in static bending strength than long leaf yellow pine and that this aspect of the comparison is based on the original numbers as reported by both sources. These numbers show the cost adjustment only and do not reflect a mass adjustment but instead the expence needed to obtain the same strength for a given volume of material




comparison of characteristics by per bd/ft dollar



bending strength poplar 18,870 yellow pine 14,117 cedar 4,963

crushing strength poplar 980 yellow pine 941 cedar 281

hardness yellow pine 942 poplar 864 cedar 202

impact strength /inches poplar 46 yellow pine 31 cedar 10

shear strength poplar 2130 yellow pine 1,633 cedar 567

stiffness poplar 3012 yellow pine 1971 cedar 713

work to max load poplar 16 yellow pine 9 cedar 4.2



dollar for dollar Poplar leads all categories except hardness



thing to remember is that some of these numbers do not adjust well to considerations of weight and cost but for the most part I think its a fair way to look at the qualities of a given wood in respect to its use in any building project

cheers
B

 

We can still get decent fir with nice enough grain to be stable. It holds up to the weather ok unless it doesn't, much better when dressed accordingly. How does this stuff you're talking about actually hold up? You're making it look pretty attractive at an old time price. Nice clear grain etc.

 

Poplar is has about the same decay resistance as the pines maybe just a tad better

whats your cost for that fir and what exact species is it
so I can factor it into the numbers

and remember
the way I have calculated the weight and cost ratio and then converted the volume based measurements needs to be taken with a grain of salt
the translation in most categories in more like a function than sum and therefor may not be as accurate a comparison as it could be
I only use the comparison as a loose interpretation of about were the pound for pound comparison lands each material

 

Toss out your old Navy data base stuff, Boston. It's no longer reasonable and covers old growth and first cut stuff, not the stock available now, let alone the farm raised junk that most of the dimensional stock is now coming from. Then there's still the rupture issue with poplar.

 

Decent fir is all over the place on Puget Sound. You have to pick through the piles a bit at the lumberyard but you can still find it. Dry clear vg fir suitable for trim is pricey but high quality framing material can be had with patience. I could track prices for you next week but off the top of my head maybe 1.25 bd ft retail.

You can't count on finding real good stuff every day but it's still around. I'm a bit of a pervert about using good material. If a job is small enough to pick up the material I get pretty good stuff, if the truck just dumps it at the site it is what it is.

 

I kinda thought the US Navy data was remarkably similar to the wood explorer data. I was actually kinda surprised at how close they were although yes there were also some interesting differences. Im glad to have the newer on line source available, I had not seen that site before and it was really pretty good. Ill have to add that site to my saved locations.

I have a whole library of antique books concerning ship building and ancient mariners including more than a few first hand accounts not only a first addition of that US navy book but also first additions of Melville's Two Years Before the Mast and an almost complete copy of Sir Francis Drakes log books and bits and pieces of Damplier, Lord Nelson and Captain cook. None of which do I plan on throwing away any time soon

Wally
I have been a lumber yard rat longer than I care to remember and although I to have dug through my share of bunks looking for those few jewels, the material I can get from the mill is vastly superior in nearly all regards. Par is not so far off the mark when he throws expense to the wind because after all, you are staking your life on what you build and price cannot be the only consideration. That bit about static bending was kinda a wake up call although by weight it was not so bad, its just it translated badly by the dollar.


Yellow pine is not available at any of the local yards around here and what Pine is available is either very low quality framing lumber or very expensive ( $7~$8 a foot ) trim that no contractor in his right mind would spring for, white pine or Hemlock mostly. No rot resistance and very weak stuff.
The quality of pine from the lumber yard depends greatly on location. Out here in the Midwest we get a lot of crap Douglas fir and Larch, even Pinion and Ponderosa pine sometimes Ive found mixed in . Nothing worth building a boat out of. getting one clear pine 16' 1x4 is like a small miracle although since you mentioned it Im going to inquire ( I need to go down there anyway today ) at the yard about what a bunk of #1 select yellow pine 16' foots will cost me. Then just for fun Ill call this mill I found on line that cuts nothing but Yellow pine and compare there price as well.

my study shows that I can save roughly half on the expense of planking by going with Poplar and end up with a thicker hull of the same weight, that is of equal strength is nearly all regards and superior strength is a few key areas like impact bending and modulus of elasticity as well as stiffness, all key parameters, assuming I cannot find any better price for Yellow pine. Speaking of which

Par what did your last load of yellow pine cost you

Im betting my guess of $3 bd/ft was in the ball park
if your feeling shy PM me the info
thanks
B

ok
Im done absconding with this thread
sorry to the original author
just working out a few things concerning planking

my apologies
B

 

I have no doubt getting wood from the mill is a better way to go. I'm just saying we still have access to decent fir without too much trouble. I am quite interested in the popular you mention. We used to be able to get very nice clear mahogany quite cheaply and easily that I used for all sorts of nontraditional uses because it was nice to work with. A victim of politically correct eco awareness. I'm interested in your final conclusions.

 

My last yellow pine was milled from my own stock at a local mill. I've purchased a good size chunk of heavily wooded land with yellow along one side and a mixture inside the fences. I'll never have to worry about good oak again, but I can see a day when the yellow may be gone.

 

Hey Boston,
Getting back to one of your questions. Here on Puget Sound when we say fir we mean douglas fir, when we say hem fir we mean hemlock. Pine means that horrible twisty stuff from Idaho, ( I don't remember the species). Cedar means red cedar. Hope this helps.

 

That pine you're referring to TollyWally is Ponderosa and it's crap for most any project, especially boats.

 

it does
and thanks Wally

ps
I sitll use Mahogany for a lot of projects its great stuff and when farm grown its not an environmental issue

agreed
its ponderosa and that stuff sucks

Dougy is also not a consideration as I find its characteristics to be outside of acceptable parameters.

Long Leaf and even Short Leaf Yellow Pine is rare and very expensive, I have found a mill specializing in yellow pine but even there I expect my estimates of $3 per bd/ft to be very low with numbers more in the range of $5 ~ $6 being more likely to be accurate, as opposed to <$1 per bd/ft for poplar

in all areas but static bending Poplar is, pound for pound and dollar for dollar, the clear winner in this comparison regardless of the source of technical data

I will need to research the calculation method of static bending in order to seriously determine its relevance to planking however from what I know of the measurement and from my own engineering experience this number is highly relevant to the materials consideration as planking. In this regard poplar is inferior to yellow pine however both cost and weight considerations may negate this difference or at least abrogate it to a significant degree as stated <13~16% by weight

cheers
B

oh
as per post #37
that rupture issue
I believe you are referring to static bending ( please correct me if Im wrong )
and that is roughly 2x by volume and only 13% to 20% by mass greater in yellow pine
so by increasing the volume of poplar not to exceed mass of yellow pine, poplar can accomplish 80% minimum of the static bending resistance required
the additional 20% max could be easily compensated for by longitudinal members ( stringers ) and bulk heads
if my assessment is somehow incorrect please detail any correction you might suggest

B