Scantlings for doug fir, pacific yew

[ken.bryant]

In planning "Kinnickkinnick" (to "Maid of Endor" design), currently planning to use doug fir for keel/stem/sternpost, and pacific yew for frames. Atkin calls for (surprise!) white oak for both. Any thoughts about whether I can get by with same scantlings as for WO, or do I need to / dare to increase them for the softer woods?

[Three Cedars]

I'm not familiar with the boat you mention. Are the frames to be sawn or steambent?

White oak is much more uniform to bend than yew. Yew is tempermental stuff almost every single tree is leaning and twisting so it is full of surprises with a great deal of waste. White oak is a better bet in the long run.

Doug fir is fine for what you mention get medium grained fir , without sapwood of course.

[ken.bryant]

Frames are to be steam-bent. A local builder got me excited about yew, but thanks for the caution. I'll play with a few trial pieces before I make any big buy.

[ 01-06-2006, 05:29 PM: Message edited by: ken.bryant ]

[Nordicthug]

Douglas Fir is excellent material for your purpose. If you can, select air dried old growth select structural rather than clear. You want a fairly generous sprinkling of tight small knots in your timbers. Each knot acts like a bolt, preventing your timber from splitting in service. A reasonably tight grain is good, as well. Doug fir is not the most rot resistant, but old growth seems to contain more pitch and is less tasty to to the little nasties who make up boatbuilder's nightmares.

If it is available, you might consider Alaska Yellow Cedar, too. Good timber, and wonderful planking.

Gerry N.

[Bob Smalser]

Originally posted by ken.bryant:
Any thoughts about whether I can get by with same scantlings as for WO, or do I need to / dare to increase them for the softer woods?http://www2.fpl.fs.fed.us/TechSheets/techmenu.html

Compare the strength data between the two in each USDA category and see.

[ken.bryant]

Thanks for the site. After looking at their figures, it looks like -- in shear, compression, etc.--doug fir is not quite as strong as white oak (well, no surprise there) -- but (and here's the surprise) pacific yew is STRONGER than oak.

Found references to books in old postings (elements of yacht design, elements of boat strength) that may help me understand the implications...

[Bob Smalser]

DF isn't as strong, but factor in weight and you'll see there are few building materials anywhere that are as strong per pound as DF.

DF also stays drier in the boat than oak, and if you use red lead liberally on faying surfaces and in fastener holes, it can last forever with routine care in your climate.

I've substituted DF one for one in place of WO in small boats, and I've also increased its scantling 15% where I thought I was on the edge.

Not familiar with the design you're working with, but in larger boats, I'd probably either contact the designer or have my local engineeer run the numbers on what size I needed.

[ 01-07-2006, 09:50 PM: Message edited by: Bob Smalser ]

[Three Cedars]

Originally posted by ken.bryant:
Thanks for the site. After looking at their figures, it looks like -- in shear, compression, etc.--doug fir is not quite as strong as white oak (well, no surprise there) -- but (and here's the surprise) pacific yew is STRONGER than oak.

I'd take oak everytime in a boat of any size. Why ? yew like most softwoods is more inclined to split than hardwoods. Yew is smaller diameter than oak and much tighter ringed so when you drill a hole or attach a fastener then the chances of splitting go up. Also yew is much more inclined to ring shake and hidden faults. Just my opinion.... I've only built kayaks! Who knows it might be just fine. ( my yew experience is limited to bows, splitting wedges, tool handles and bench legs )

[ken.bryant]

Thanks, fellow BCer. Well, I got my curiosity up about Yew now, so I'm going to play with a piece of two. But if I don't like it, I'll go back to plain old vanilla (white oak).