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Hammond Dory Builder
02-05-2010, 08:21 AM
I am ready to hang the garboard plank on a 16' John Gardner Hammond Dory. The bottom is 1+" pine, and the plank is 1/2" clear cypress. The frames are sawn oak sandwiched with epoxied plywood gussets (no hackmatack growing here in Delaware!). I'm building upside down, and everything is fair. The garboard is all clamped and tucks in nicely at stem and transom (with a few groans from me and the stock).

My question: If I use 3M 5200 to bed the strake, how concerned do I need to be about the fastenings? Might I even use skinny ones (like drywall screws) and remove them after the 5200 sets up? If the mere notion of using 5200 is horrifying to readers, I'll listen to that, too! Please help me avoid the moaning chair!

Clinton B Chase
02-05-2010, 08:38 AM
You are bedding the lap in 5200? Then use the same fastening you would if it were dry. Also, 5200 is viscous and if it is a little cool in your shop, you need to give the lap time to close up. Are you clenching or riveting? I think 5200 is fine. The other way is to bed it dry and after planking, with the boat upside down, run a v-groove down the outside of the lap and apply a bead of polysulfide or 5200. You would still want to use a little goo in the gains and hood ends. 5200 is permanent.

Hammond Dory Builder
02-05-2010, 09:01 AM
Actually, I was thinking more about the mating surfaces with the bottom, stem, and transom at this point, which includes the hood ends. I have beveled the "upper" edge to receive the next plank "above," which of course is below, working upside down! I suppose if the 5200 works, I will use it all the way.

As for the plank-to-plank fastenings, I haven't thought that far ahead. If my fit quality seems promising, I may try rivets. The stitch and glue people take their wires out, right? Could I do the same with tiny screws?

By the way, I can blame this boat partly on Portland, Maine. I was visiting on business years ago and bought my first Gardner book in a bookstore there.

James McMullen
02-05-2010, 10:18 AM
Most of us here in the boat repair business wouldn't recommend 5200 for this. . . . .not because it doesn't stick, but because it sticks too well for this purpose. You will be making your boat pretty unrepairable way down the road if you use 5200--you'll destroy the surrounding planks trying to get a broken piece out for fixing.

Sikaflex or Boatlife run in a bead like how Clint describes is how I'd do it. 5200 is using a sledgehammer to drive a thumbtack here.

Bob Smalser
02-05-2010, 10:37 AM
... garboard plank on a 16' John Gardner Hammond Dory.

... the plank is 1/2" clear cypress.

...3M 5200 to bed the strake

...The frames are sawn oak sandwiched with epoxied plywood gussets

Please help me avoid the moaning chair!



You aren't "bedding" your garboards to the frames, you are gluing them to the frames. I'd use a nonadhesive bedding compound.

Dory garboards are wide and are noted for cracking because of fasteners alone impeding seasonal movement. That's why Gardner often recommended plywood garboards on otherwise solid-planked pine and cedar boats. Glue makes that situation much worse because it has less "give" than fasteners...and to compound your problems, cypress isn't as seasonally stable as either white pine or light cedar.

Last, as there have been notable epoxy failures with White Oak, consider adding substantial rivets to your frame gussets if you haven't already...these use six per frame:

http://pic20.picturetrail.com/VOL12/1104763/6771586/382303649.jpg

Ian McColgin
02-05-2010, 11:00 AM
Bob is absolutely correct about bedding. This construction is not good for dry sailing as there is no seam comound or glue that can keep up with the changes in shape. For that reason, dories of this sort need to live in the water. The ones I've seen that are happiest (if all dimensional wood, no ply) simply have the garboard and keel coming together and maybe in the spring before you put on the bottom paint use a grease gun to squirt in a bead of roofing tar or roofing tar/underwater(brown) seam compound. It sill swell shut.

I guess it's too late to suggest making a narrower garboard with first strake bevel lapped smoothy on, but you can take that approach in a year or so after the garboard splits.

G'luck

Thad Van Gilder
02-05-2010, 11:55 AM
5200 = F*** you to anyone in the future who owns her.

That would be a very, very poor choice. Try polysulphide.

-Thad

Bob Triggs
02-05-2010, 02:28 PM
If you have a really close fit between the garboard edge surfaces meeting the bottom"s bevel edge and the stem bevel and transom bevel, you should not need much in the way of sealant. The same goes for the plank lap joints- if they are carefully fitted to meet flush along their lengths, they shoud be fine.

The old-time way was to use a light slip of cotton caulking material between the faying (meeting wood to wood) edges. One way was to apply pine tar/stockholm tar to the meing edges and lay down the cotton prior to finally nailing together. Another way was to tack the cotton down to the bottom board edges with very small light tacks. The cotton would be a very light string-like twist of about an eighth of an inch in diameter. It should compress flat in the joint and not interfere with the mechanical strength of the joint. You buy cotton caulking and strip it down to what you need and twist if between your fingers as you are applying it. Some old timers woud use paint to set the cotton on the joints, red lead being a favorite. The idea is you have to have a (sticky) way to get the cotton uniformly onto the joint prior to fastening the wood. But you dont want to saturate the cotton in the joint with tar or paint or goop since it needs to be able to swell and dry somewhat freely. Once you paint the boat- enough paint should weep into the outside of that tight seam to act as a sealant.

If you fit and fasten as per John Gardener's original instructions in The Dory Book it will work out fine. Once the wood gets damp and the joints take up a bit with some light swelling you are all set. If you are using it off of a trailer, and storing it dry between trips, then the polysulfide sealant may work well for you.

But the major stength of the joint will still need to come from a good, tight close fit of the join between garboard and bottom, and garboard to stem and transom etc, and by using the proper hardware. I think that Monel Ring-Shank nails are very good for this application, boring tiny pilot holes along the way. Those tight surfaced joints need very little "filling" or sweling to get a leakproof seam.

The more I deal with small boats the greater wisdom that I can see in some of those traditional techniques- ideas that evolved with the thousands of years history of small wooden boat building. The cotton will last for years, decades in fact. And it easy to repair a boat built that way.

I had to learn all of this the hard way.:rolleyes: