Did Chapelle Goof????

[UCanoe_2]

Guys, I am confused.

On p. 248 of Boatbuilding, Chapelle illustrates the right and wrong ways to plank the bottom of a flat-bottomed boat. Of course he installs the planks so that when the wood cups, the concave side of the plan is toward the inside of the boat. He shows the cup curving the same way as the wood's annual rings; that is, the concave surface is toward the inside of the tree.

I have plenty of warped lumber, and the cupping goes in the opposite direction from the annual rings. The concave surface is toward the outside of the tree. Is Chapelle mistaken, or did my lumber come from a different planet, or am I just looking at the pictures wrong??

This matters because I am building a new boom for my old Finn. (More posts and pictures will follow in the near future.) The boom is basically two 1 x 4s laminated to make a 2 x 4 spar. The lumber is nice and flat now, but when it does cup I want the stresses to hold the glue joint together instead of splitting it apart.

What to do?

[Jay Greer]

When I visited the Herreshoff home, I was able to review a printer's proof, the same book that Chapelle had sent to LFH. The margins of the pages were loaded with Herreshoff's comments concerning just such discrepancies. In his defense, I will say that the book is one of the best ever written on the subject of boat building. Also, the writing of a "how to" book is a major undertaking! Mine is still in rough draft form.
Jay

[S B]

When Chapelle built boats they were meant to go in the water and stay there. Sitting on a trailer, baking in the sun, requires a different approach to using wood.

[UCanoe_2]

When I visited the Herreshoff home, I was able to review a printer's proof, the same book that Chapelle had sent to LFH. The margins of the pages were loaded with Herreshoff's comments concerning just such discrepancies. In his defense, I will say that the book is one of the best ever written on the subject of boat building. Also, the writing of a "how to" book is a major undertaking! Mine is still in rough draft form.
Jay

Isn't the purpose of the proof to identify errors that are corrected in the book's final published version?

[UCanoe_2]

When Chapelle built boats they were meant to go in the water and stay there. Sitting on a trailer, baking in the sun, requires a different approach to using wood.

The construction techniques may have changed, but wood still behaves the same with regard to cupping, twisting, warping, etc.

[crawdaddyjim50]

Well stuff happens with books due to people that are not conversant in the subject matter being the ones doing the editing. It just doesn't appear to them as it would someone who has experience in the subject.

As for the cupping matter. What type of glue are you using on the boom? Also if you are worried about movement you could make quarters of the stock and glue them up with the grain running so as to cancel out such movement. Eh?

[Canoeyawl]

There are a number of questionable practices in that book. The most glaring being the advice on casting lead...

He advises wetting down the mold before pouring - Danger-Danger-Danger

But, as Jay said, it is a great reference volume.

[Peerie Maa]

Just to stir the pot.
Is the original post talking about the way the wood cups as it dries out. When we build a boat we start with dry wood and then get it waterlogged. So the cupping will go the other way?

Try to let the wood for the boom reach the humidity of the completed painted/varnished spar before gluing up, then there is no reason for the wood to move further.

[peter radclyffe]

Guys, I am confused.

On p. 248 of Boatbuilding, Chapelle illustrates the right and wrong ways to plank the bottom of a flat-bottomed boat. Of course he installs the planks so that when the wood cups, the concave side of the plan is toward the inside of the boat. He shows the cup curving the same way as the wood's annual rings; that is, the concave surface is toward the inside of the tree.

I have plenty of warped lumber, and the cupping goes in the opposite direction from the annual rings. The concave surface is toward the outside of the tree. Is Chapelle mistaken, or did my lumber come from a different planet, or am I just looking at the pictures wrong??

This matters because I am building a new boom for my old Finn. (More posts and pictures will follow in the near future.) The boom is basically two 1 x 4s laminated to make a 2 x 4 spar. The lumber is nice and flat now, but when it does cup I want the stresses to hold the glue joint together instead of splitting it apart.

What to do?
when it does cup ? it would be better to quarter saw your timber, so it doesn't cup, on a big spar you can use other timber, but the margins on a small spar are mimimal,

[Krunch]

Just to stir the pot.
Is the original post talking about the way the wood cups as it dries out. When we build a boat we start with dry wood and then get it waterlogged. So the cupping will go the other way?

That answer works for me! :D

[floatingkiwi]

Guys, I am confused.

On p. 248 of Boatbuilding, Chapelle illustrates the right and wrong ways to plank the bottom of a flat-bottomed boat. Of course he installs the planks so that when the wood cups, the concave side of the plan is toward the inside of the boat. He shows the cup curving the same way as the wood's annual rings; that is, the concave surface is toward the inside of the tree.

I have plenty of warped lumber, and the cupping goes in the opposite direction from the annual rings. The concave surface is toward the outside of the tree. Is Chapelle mistaken, or did my lumber come from a different planet, or am I just looking at the pictures wrong??

This matters because I am building a new boom for my old Finn. (More posts and pictures will follow in the near future.) The boom is basically two 1 x 4s laminated to make a 2 x 4 spar. The lumber is nice and flat now, but when it does cup I want the stresses to hold the glue joint together instead of splitting it apart.

What to do?
Hang on a minute mate. You are not comparing apples with apples. Boat bottom planks and spars. Wet and dry. Wouldn't they behave different?

[Jay Greer]

In most cases, I try to work with quarter sawn or VG stock that has little or no tendancy to cup across the grain.
Jay

[paladin]

and if your worried about cupping, cut up the wood in thin slices...keeping them in order, then flip every other one end for end and reglue them back together...solves the cupping problem.