Gartside Dingy Garboard Twist

[Nick Ratto]

Hi, I'm a new member. I'm writing to introduce myself, post some pictures of the boat I'm building and ask a question.

I'm building the Gartside sailing dingy that was featured in the November/December Woodenboat. She's hard-chined ply with four strakes per side and epoxy/taped seams. She's put together similar to the Tom Hill method using battens over the molds to determine the plank shapes. The battens are planed down to accept the planks butting up to each other. The seams are then epoxy filled and taped. The entire hull is epoxy/glassed after it goes together.

Here's where I'm at now:
http://www.imagestation.com/snicks02/Gartside_stringers
http://www.imagestation.com/snicks02/Gartside_Transom

I am attempting to install the garboards and am having some trouble with the twist going from the first station to the bow. It takes a whole lot of force to get the garboards to meet the bow. I was able to get one somewhat into place with liberal use of windex (I read that amonnia helps with flexibility) and lots of clamps but the design is such that I won't be able to use all the clamps (The other plank will be in the way) when I epoxy the garboard to it's nieboring plank. The plans call for nailing the planks to the battens but I don't think that they will be able to take the pulling force as the plank attempts to untwist.

I know that one problem is that I'm using 3/8 inch marine grade doug fir that had been in storage for a while (Like 20 years) and the plans call for 1/4 inch. From what I have read in the forum, 3/8 should still be able to work. However, I'm somewhat concerned about the age of the plywood and that it sat in a hot workshop (regularly in the 90s during the summer) for so many years. Anyone have any experience with older plywood?

I'm going to try the towels in boiling water routine and, perhaps throw them in the pool for a while. Any other suggestions?

Thanks,

Nick

[Big Red]

Nick, mate I can't offer much in the way of boat-building advice, but might be able to help with your pics.

To get them to show on this forum, they actually have to be on the web somewhere, like in an Image Station album, or on someones web site.

If they are on the net, or after you put them there, what you do, when your typing your post/reply is click on the button underneath the window that says Image.

That will give you a little box, in which you put the URL, the address of your pic. You can get the URL by right-clicking on the image and clicking Properties. The URL will show up in the Properties window.

Anyway put that URL in the box that pops up when you click Image, and there you go. Bob's your Aunty :D

[Bob Ketterling]

Nick - what kind of clamps are you using? In a similar situation I used the plywood clamps that Oughtred describes in his book on clinker plywood construction and they worked well on 3/8 ply.

[Nick Ratto]

I'm going to try posting the images again. Seems that I used the wrong addresses.

http://www.imagestation.com/picture/sraid119/pa4011bc4035220b04c2245de8a034497/f87c3fbc.jpg

http://www.imagestation.com/picture/sraid119/pb21338824596ea89fe183b96b0d49a3a/f87c3fb7.jpg

Big Red, thanks for the help with the images.

Bob, I do have some of those clamps that I used on an Acorn dingy but I was worried about the plank pulling the batten out of wack. I guess the real issue is the amount of force it will take to keep the plank in place. I'll see if those will help while I try the hot towels.

Thanks everyone,

Nick

[shamus]

That looks to be a fairly vicious twist for 3/8 ply. Here's a thought. If you're not bright finishing the garboard temporarily attach (screws)to the problem area of each garboard a batten say 2"x1" and a couple of feet long so that the battens extend towards the floor when the planks are in position. These will help you twist, and a spanish windlass (twisted rope between the two might hold them in position while you get 4 or 5 screws into the stem. Fill the screw holes afterwards.

Or you could use 1/4' ply for the garboards, and use up your supply of 3/8 on the upper strakes which will lie easier to the stem. My 2c worth.

[ 05-31-2004, 03:59 AM: Message edited by: shamus ]

[Big Red]

Wow Nick, looks awesome so far! Hopefully it works out for you soon... and we can see more pics :D

Could you use, umm doing the maths in my head, two layers of 3/16" ply for the garboard strake, and leave the 3/8" ply for the rest of the boat?

Good luck anyway mate :D

[Nick Ratto]

Shamus, The hull will be glassed and painted so holes in the plank will be no problem. I had thought about doing something like that but with epoxy instead of screws then heating the epoxy to remove the lever. I like your idea better though. I'll probably try a couple of them for each plank. I'm going to give that a try tomorrow.

Using one 1/4" or two 3/16" layers was the last resort since it would require buying more wood. It doesn't grow on trees you know. Uh, well...

I'll let you know how it goes.

Nick

[shamus]

Nick I was thinking about it overnight and had another idea which might be worth thinking about. It occurs to me that it might be possible to reinforce the batten temporarily by spiling a 3x1 or similar to fit inside it on edge. Then screw right through the plank, batten and into this reinforcing timber with drywall screws until the glue goes off. Any use??

I had a similar problem myself once and opted for thinner ply, but it causes a small problem with the width of the outer stem.

[Nick Ratto]

Well, I got one in place. I used copious amounts of windex, screwed two levers onto the areas with the most twist (Thanks Shamus), and used a clamp at the forward-most end of the plank. I attached a piece of line to the end of each lever, ran it down to a screw in the building frame, back up to a screw in the end of the lever, then back down to a 10 pound lead weight. It provided just enough force to keep the plank where I put it without pushing it down before I wanted it to. It also gave me a lot of purchase given the length of the lever and the makeshift "screw" and tackle system. I just pushed down on the levers and the plank stayed where I put it. Pretty cool.

http://www.imagestation.com/picture/sraid119/p02a230c0ebccf487283bf4e64a7732cf/f8701277.jpg

Here's a picture that does a better job of showing how much twist is in these planks.

http://www.imagestation.com/picture/sraid119/p7e0cbd37491c865aaf85b80d8d98ba8e/f870127b.jpg

I'm letting it dry in place overnight and tomorrow I'll remove it, trim it to size, and prepare to attach it for good (forever?).

My plan is to spile the plank below it and lay them on together so I have something to secure the upper edge (Towards the shear) to.

With any luck, I'll have a couple of planks on tomorrow!

[shamus]

Good!

[Big Red]

Success, awesome :D

Good luck, and keep us posted :D