Boomkin rot

BALANCE · Post by **BALANCE** » Wed Apr 01, 2009 6:08 pm

IYHO's, how bad is this?

Hirilondë · Post by **Hirilondë** » Wed Apr 01, 2009 8:08 pm

rescuesailor · Post by **rescuesailor** » Wed Apr 01, 2009 11:35 pm

I think your Sc***ed! seriouslywhat are the dimensions of this lumber? I have a bumkin made of teak that measures 1.5 inches by 5.5 inches. I had a plan to replace it with 2 inch schedule 40 SS pipe. A friend who is a structual engineer told me that the wood is actually better. I have a hard time believing it but that what's he says. At any rate I have always worried abou that wood holding up a 53' tall mast! maybe you should think about replacing with Stainless steel.

Ric in Richmond · Post by **Ric in Richmond** » Thu Apr 02, 2009 7:30 am

Bad...but what loads are fed into it? Compression right?

May not be AS bad if it is only compression load. I can see that you might jury rig some plates to carry the load over the bad spot, but only for a temporary repair

If there is any bending load put on it then it is done NOW.

But hey...what do I know? This info is worth exactly what you paid for it!

Quetzalsailor · Post by **Quetzalsailor** » Thu Apr 02, 2009 8:36 am

First, determine whether that's the whole extent of the rot. The other screw holes may be similarly affected, but to differing degrees. The open checks on the top surface may conceal problems (they hold water). The open check on the side adjacent to your excavation may extend to the rotted area. You may have problems elsewhere on the spar, like at the bedded end on the boat.

Even if you have to remove half the vertical dimension of that timber, say, 1 1/2" of (my estimate) the 3", that's a scarpf of 12" each way, at 1:8, or a repair 24" plus the distance along the rotted area long. I have no idea how long the whole chunk of wood is, or how complicated the fitted shapes at each end are, but a repair 'dutchman' as big as that is not so unreasonable. Saws, chisels, spokeshave, and chalk, will make quick work of it.

If the rot is less extensive then a dadoe or 'trench' with ends tapering up at 1:8 will be just fine, but a little harder to ensure a good fit. Plunge cutting with a dadoe blade on a radial arm saw would rough it out quickly; clean up with the chisels. (Clearly, the ends of the dadoe would be the diameter of the dadoe blade, but if the slope at the surface is 1:8, you're finished w/o much further effort.)

Use matching species and cut of wood, both for appearance but more importantly for function. Looks like Fir to me. 'Cut' means orienting the rings in the same direction; looks to me like the rings are vertical (look at the end). Use epoxy with microfiber filler; neat coatings until the wood does not take any more then plenty of filled mix to ensure a full glue line.

My favourite dutchman is one in which the excavation swoops down to the required depth and back up in a nice even curve, rather than sloping uniformly down, hard turn to horizontal, hard turn back to the surface. The swooping shape is easier to fit and looks prettier to my eye. I've done a dozen in my FD and a couple more on its' mast; no doubt a bunch more on other projects.

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 4:03 pm

I've decided to replace it, it's a fairly simple installantion. Now wondering what kind of wood to use. Sitka spruce? I'm not quite sure what I have now. Many different opinions, always sheds doubt.

bcooke · Post by **bcooke** » Mon Apr 13, 2009 4:21 pm

Sitka is a very strong wood for its weight. It doesn't measure up to the better hardwoods though. It wouldn't be my first choice on a heavy displacement boat.

Are you thinking varnish or paint?

Sticking with what is already there is usually a safe choice.

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 4:51 pm

That's my problem, many different opinions as to what I have now.

bcooke · Post by **bcooke** » Mon Apr 13, 2009 5:14 pm

That's my problem, many different opinions as to what I have now.

Then you need to be more critical of who you solicit opinions from. :-)

The world is full of stupid, half baked opinions. Most of them originate over the Internet.

Seriously, ask around for a (real) wooden boat guy or quality woodworker. I bet they could identify the wood from 50 yards. The ones around me that know what they are doing get frustrated with me when I scratch my head for two seconds. Its just so obvious to anyone with some skill.

Shoalcove · Post by **Shoalcove** » Mon Apr 13, 2009 5:48 pm

Local white oak (not red) would work great I think. Sitka would seem fine if you have the would already. Douglas fir could be used as well. I'm no expert but all these woods get used for such things. Have fun.

Oscar · Post by **Oscar** » Mon Apr 13, 2009 6:05 pm

Or, get yourself a tig welder and some stainless tubing......... A good excuse to buy some tools and learn a new skill....

BALANCE · Post by **BALANCE** » Mon Apr 13, 2009 8:51 pm

There is a guy who supplies stainless boomkins for WS'ers. I just prefer the wood. I bought a pushpit from this same man and if I hadn't, I never would have discovered the rot until it failed. I should probably saturate the new boomkin with epoxy....hmm.

Britton, a 'wood guy' - ship right told me it was Spruce. I put the question up here because I thought the WS's were fitted with Douglas Fir boomkins. This wood guy thought Sitka Spruce was better....stronger but I think I'm gleaning otherwise. Tim?

bcooke · Post by **bcooke** » Mon Apr 13, 2009 9:19 pm

The original certainly could be spruce. My first thought is that Doug fir would be an excellent choice.

Post by **Tim** » Tue Apr 14, 2009 5:57 am

I think the wood in the photo looks like Doug fir from here, but it could be spruce too; I don't have a PhD in wood ID, after all, so I may be missing some intricacies in the wood grain or appearance that would lead to a firm choice one way or the other.

Ultimately, the quality of the pieces of wood used for the new boomkin will have a direct effect on its strength, so whatever the species be sure the pieces of wood to be used for the boomkin are chosen with strength and application in mind--straight grain, no knots, etc.

Wood is strong. Don't be afraid to use it. Replace in kind, and you'll be fine.

Hirilondë · Post by **Hirilondë** » Wed Apr 15, 2009 11:18 am

Tim wrote: Wood is strong. Don't be afraid to use it. Replace in kind, and you'll be fine.

OOOH! Would you print the score for that? :)

Once Spruce has aged it can look a lot like Douglas Fir. Both have been used for spars and related structures (like a boomkin). The two characteristics they share, and which make them most suitable is strength, both compression and shear, and they hold fasteners well. Spruce is a bit lighter, so often first choice for spars. If sufficiently designed, either would be most acceptable for a boomkin.

Idon84 · Post by **Idon84** » Thu Apr 16, 2009 12:31 am

My boomkin is Honduras Mahogany. My bowsprit will be doug fir.

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