Dory tack welds

Hi to all,

I've posted recently about a  Northeaster Dory build I'm doing with a HS shop class.  Thanks for the support of those who have replied.

Not unexpectively, we've worked through a host of issues already. The kids have been great in sucking up their mistakes and redoing things. They're proud beyond words that they're actually building a boat. 

Our Christmas break begins tomorrow and my plans are to go in for a bit to tweak the stitching and to do the spot welding of the outer hull .  Would like for the kids to come back and fillet and lay glass.

Question has to do with how true to form the hull has to be before tacking. In particular, the transom seems to be laying drastically off center.  When the hull is right side up, I can easily twist it to any shape I want. Upside down, I'm not confident in my vision.

I don't know if I should be worried about this at all as the manual shows that the worrying begins when the glass gets applied.  Tack now, worry later or .........

How much does "tacking" matter beyond the fact that it allows you to remove the stitches?

Thanks again,

BTW

just having the chance to teach bow/stearn, port, starboard, thwarts. gunells,   etc to a bunch of dairy farm kids from central Vermont has been a hoot. 


3 replies:

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RE: Dory tack welds

You really need to get the boat as fair as possible before you tack weld the hull. From experience it's not that easy to straighten out a hull, particularly the transom, after that has been done. It can be done but it's a pain in he butt! Just make sure you have two level sawhorses to put the boat on and make sure the horses are square to the center line of the boat. That will take the twist out of the boat if its making contact with the horses at he same points on each side. Then straighten up the transom. The tack welds will hold that shape. And since you're going to be doing them yourself you won't have to worry about the kids bumping it out of position before the epoxy has cured. 

Sounds like you're having a lot of fun with kids. Keep us posted!

George K

RE: Dory tack welds

Just to empahize what George said, once you tack it, that's the shape it will have forever unless you cut the tacks. They may not look like much, but those tacks are strong enough that you can pick up the boat and move it around without it changing shape. They are what sets the shape of your boat. The fillets and glass reinforce the tacks so that they won't break, but the tacks are what define the shape.

Laszlo

PS - I know it's nitpicky, but as a fomer welding instructor in a major West Coast shipyard it makes me cringe when I hear people talk about tack welding S&G boats. Welding is when you melt the work so it flows together and hardens back into one piece. Wood doesn't melt. What you're doing with the epoxy is bonding it. Thank you for letting me get that off my chest. Merry Christmas

 

RE: Dory tack welds

ditto on everything said.

another tip i would put out there is having a gaggle of levels and shims to help with the line up.

there is a section in the tips section called 'checking for twist'  http://www.clcboats.com/shoptips/stitch_glue/checking_twist.html which is a nice overview.  over the length of the dory there are a lot of places little errors can work there way in....before tacking/glassing is your last way to easily address anything to do with line-up/twist/basic hull shape.

a couple notes from the 'if it can go wrong, it will go wrong' that i would share:

- good lights

- good sightlines (ability to get in front and behind) (sometimes hard for garage builders)

- lots of levels (depending on the craft, addressing one alignment problem can move the problem to another area)  i bought a bunch of these small $2.00 plastic levels in addition to having the one of the more expensive/longer ones.

- check levels at each station

- recheck after you tack-but before the tack is set - you sometimes bump/move it in the process.

- monitor during the cure process/secure the area to ensure nothing moves during the cure (don't want to re-tell my story of cutting the panels apart on a twisted hull after the fillets hardened -- one of my children kicked a shim out of a sawhorse supporting a curing hull while trying to retrieve some equipment from the garage)

- repeat process again when the final fillets and glassing occur. (while the tack should hold it pretty much, heavier hulls like the dory, if not properly supported can still develop twist until fully filleted/glassed....it will just be smaller deviations)

best of luck

howard

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