Saturday, November 10, 2012

Doryman's Melonseed


You thought I'd forgotten the melonseed?

We've had a very mild fall with little rain, which is a bonus if your livelihood is maintaining and building wood boats. Recently, however, the weather has not been so nice and Doryman wishes he'd spent more time on his woodpile.

When weather threatens around here, we retreat to the back porch for boat work, which is at least dry, if not heated. Then, each day is gauged by the barometer and the dewpoint. It's a little known fact that epoxy is not nearly as sensitive to temperature, as moisture. I don't mean to be confusing here, epoxy does not give a fig about moisture. But wood does. It's this simple - if the wood is saturated with moisture, it will not accept epoxy. But if there are ten degrees (F) of separation between the current temperature and the dewpoint, and your wood is not actually wet or green, the epoxy will penetrate and adhere to the wood. The shop-vac is useful for "air-drying" wood surfaces, though a hair-dryer works wonders. If last night was cold and today it will rain, try blowing your wood surfaces with a fan or a shop-vac exhaust before applying epoxy.




If the conditions are wetter still, which might seem extreme, though we spend four to five months a year around here with 100% humidity - so we understand - a very good substitute for epoxy is a polyurethane glue that is formulated to cure in the presence of moisture. Which is why you see a black adhesive in some applications, in the construction photos. Another excuse for using polyurethane glue is probable movement. Epoxy has much more tensile strength than wood, so will fracture and de-laminate where wood flexes, swells or shrinks. In those cases, a more flexible bond is required. I bond all my plank laps with polyurethane glue, because my boats are built to be outside, in use, all year-round.




To date, the Doryman melonseed has been planked and framed for decking. The most recent step has been the installation of anti-skid strips milled from Oregon white oak. Aside from helping to keep traction, they act as stringers which add stiffness to the wide garboard plank.



Photos of this build can be found on Doryman's Flickr site.

One day we may take some time to talk about the design process. This particular design is informed by Howard Chapelle, William Atkins and Uffa Fox.











In other Doryman Boatyard news, the mast for the Teak Lady, Che Hon is being repaired. This 73-year-old old Douglas fir mast was cut off at one time, just above deck level, with the intention of installing a tabernacle, but we've decided to restore the boat to as-built condition. A foot above the old cut, the mast was hollow so in order to scarph three feet onto the existing mast, a plug was fashioned to fill the void.

The mast is 3 1/2" in diameter and the scarph is 12/1.










As a result, the mast will be much stiffer, higher up from the deck, which will affect it's bending characteristics. This might promote failure, if the boat were sailed to it's potential, but it's not likely Che Hon will ever campaign another race, she's retired.

Sounds a lot like the tired old sailor typing this missive...



6 comments:

Dabbler said...

Greeting from Georgia,

The Melonseed is looking great. You mentioned using polyurethane on the laps. Is that the 3M 4000 or are you using something else that is formulated for below waterline applications?

I've been enjoying your blog for some time now, thanks for all the great photos, stories, and links.

Best regards,
Don Foster

doryman said...

Thank you, Don,

At the risk of endorsing a product... I used 3M 5200 on this boat. More often I use Sikaflex, which is a slightly different chemical formulation and a few dollars less expensive.
The Sikaflex has less bonding strength, but they are both very effective.
5200 is less viscous than Sikaflex and takes quite a bit longer to set.

I don't talk about "means and methods" very often - there are so many good products and everyone has their tricks of the trade. But I do strongly recommend marine grade products for boat building, which runs counter to a lot of opinion you find today.

Welcome aboard!

michael

Port-Na-Storm said...

Doryman, I'm glad you are back working on the Melonseed, I was beginning to wonder. I'm very interested to see how she sails, I've only ever seen one for real and never afloat. They seem perfect for some of our sheltered waters.

doryman said...

Graham,

There was a steady flow of paying work this summer, which is a good thing as far as that goes, but I'm back to the important stuff now.

I assume you saw the video of her water trial. She sits very pretty in the water. About a month ago, I finished a sprit sail, mast and sprit, but still need to carve a boom. (tried the sail rig without a boom and it was not satisfactory).
Sometime this winter, plans will be available for this boat, it's turning out to be a winner.

EyeInHand said...

You must have been reading our minds. Really looking forward to following this one, of course. Great to see it taking shape.

doryman said...

Barry,
I haven't been neglecting my friends, honest! Days go by and I can gauge the progress, but if I stand back and take in the bigger picture, it's hard to see.
Then I wonder if folks would really like to see yet another framing picture that looks so much like the last one, it's a test to see if you can pick out the differences.
Last year this time, the plan was to have the boat done by now. I'm sure you know how that goes.