Grown Douglas Fir Spar Fabrication?

[jferguson]

Come spring of 2004 I'm going to begin construction of a cutter rigged cruising vessel, likely a Buehler design, which can support a "grown" spar in the 40 ft range as the mast. I live on an island on Puget Sound with healthy stands of Douglas Fir which have grown in dense forest (tall, straight and clear) so I intend to try cutting a couple of trees for mast, booms and bowsprit. I've found relatively brief descriptions, often contradictory, of the process one should employ to season and shape such spars but nothing comprehensive. Soooo, I'd be very interested in input from the remarkable members of this forum; either personal knowledge/experience or reference to published material on the matter.

What say you all?

[imported_Conrad]

I knew a guy who had grown spars on his boat several years ago. After cutting, he had barked and shaped the spars, then painted the ends and applied oil to them as they seasoned in a shady part of his yard for about three years while the boat got finished. There was some checking, but not too bad. My sense is the more slowly you can allow the process to happen, the less checking there might be. Instead of oil, I know there are commercial products used by those who mill their own lumber to slow the drying, thus minimizing the checking.

[Mike Field]

Would this be one of those instances where it would be a good idea to control the checking by taking a longitudinal cut half-way through the log for the whole length? I've not done this, but I understand it localises the checking, so the overall result is that essentially any checking that occurs just widens the cut. Then when the log has seasoned properly you glue in a spline of the appropriate size.

But in any case, I'd certainly seal the ends against air penetration, probably by slathering on bitumen paint. (Or perhaps some epoxy if I were feeling paticularly flush that week.)

Oh, and by the way Jeff, welcome to the Forum.

[TomRobb]

I've heard that Japanese post & beam builders use the longways kerf to control checking & placed so as to not see the kerf - I suppose because it will continue to swell & shrink. For compression only loads the kerf should be meaningless. Of course your mast will get some beam loads too.

[jferguson]

Creating a control cut, much the same way as in concrete work, is something I hadn't heard of or thought about. Lots of Fir around here. Maybe I'll try both ways and see what happens. Will post on the forum if the results prove interesting.

Thanks for the welcome Mike. I'm having a great time learning by reading posts on this forum!

Jeff

[redsail]

Great to have your new spars growing nearby.
Perhaps you may want to select a couple of trees that will become your masts and slice the bark and into the sap wood all the way around a foot or so above the ground. The tree will die because the sap can't run and your masts will season standing up. I think tha possible risk of checking would be lessened. Now would be the time as the trees are as dormant as they will ever be.

[redsail]

Great to have your new spars growing nearby.
Perhaps you may want to select a couple of trees that will become your masts and slice the bark and into the sap wood all the way around a foot or so above the ground. The tree will die because the sap can't run and your masts will season standing up. I think tha possible risk of checking would be lessened. Now would be the time as the trees are as dormant as they will ever be.