Surprise

[Steve Ambrose]

I'm working on an Otca that got crunched in the midsection and was repaired years ago. I knew based on the humps and bumps I would uncover some surprises. Most of the wood that was replaced needs to come out and this evening I found the reason in print!

 

[Kathryn Klos]

Nice to have your suspicions so clearly spelled-out!

 

[goldencub]

Could someone explain what the problem is with spruce, assuming it's close grained and knot-free? Why does spruce give humps and bumps? Al D

 

[Greg Nolan]

I believe that the problem is not with spruce, but that the source of the wood was common grade studs, which may have been spruce or may have been balsam fir, and were likely to have had knots, not been close grained, and not been straight grained.

Someone carefully picking through a pile of lumber yard (or big box store) studs may occasionally find a piece of clear, straight grain wood, but such a piece would be unusual, and if someone just buys the run of the mill, the majority of the wood will be far from clear and far from prime.

 

[MGC]

H-4 Hercules

Could someone explain what the problem is with spruce? Al D

Nothing if you are Howard Hughs and building the spruce goose.
Ribs are normally cedar...I presume the bumps have more to do with workmanship than the material....

 

[Steve Ambrose]

While clear spruce is the wood of choice for inwales and it takes long curves well, it doesn't take the sharper bends of the typical rib shape very well. In this case virtually all the ribs that were replaced using the spruce/fir stud material failed. They either kinked, cracked, or broke across the rib creating a hard spot or angle where a curve should have been. Most of the ribs and planking milled from the SPF (spruce/pine/fir - who knows)? ended up splitting lengthwise as well. The typical trees used to make studs have wide growth rings and when you mill quickly grown SPF down to the thicknesses we deal with in building canoes you end up with weak, brittle material. Some ribs displayed compression failure (inside fibers crushed) while others showed tension failure (outside fibers snapped). Cedar ribs can suffer the same fate but usually take the bending much more successfully. I usually snap a couple especially at the ends over the stems. Frankly I'm surprised the last guy didn't give up in frustration and torch it!

 

[Andre Cloutier]

Should have used PRIME lumber, such as the high quality 2x4 provided by the Home Despots. Nothing but the best for this beast