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andrew scease
12-21-2007, 11:21 PM
I recently purchased a 17' Swampscott Dory rigged for rowing and sail. I was thinking about taking out the thwart at Frame 3 and running a 9-12" bench (both sides) on top of the riser from the aftermost Frame to Frame 2. I was planning on notching it to fit at frame three and tying it into the thwarts at each end. Is this a good idea? Do I need to add knees at Frames 2 and 4? I have seen a similar arrangement on an Amesbury Skiff(?). Would it work on a dory w/o compromising structural integrity?

Bob Smalser
12-21-2007, 11:34 PM
You mean like this? ;)

http://pic20.picturetrail.com/VOL12/1104763/7372002/96856024.jpg

http://pic20.picturetrail.com/VOL12/1104763/7372002/96856011.jpg

I left the thwart in, but in some designs you can make the seats full-length and replace the knees on the thwart you remove by installing your side seats and installing new knees that land on the frame beneath the seat. That's if the structure can handle the loss of a thwart.

The Swampscott in Gardner's Vol I only has 4 sawn frames with thwarts, with no thwart at midships max beam width and #3 positioned immediately abaft the beam. Removing #3 looks structurally inadequate from here, in that the boat will lose half the support for the maximum beam width and also around 7 feet of total breadth support. I don't think the intermediate bent frames are sufficiently strong to support the loss. The boat's shape will distort, if not immediately, then in use. Mast and sail against passenger weight as counterbalance put a lot of stress on a light hull.

andrew scease
12-22-2007, 01:01 AM
thanks Mr. Smalser,
both you and my Dad are of the same mind. What do think if I reduce the width of the #3 thwart (maybe double the thickness?) and put in the bench? I'd like to keep as much room inboard as possible. She's a little narrow in the beam to begin with. The frames are fairly robust. Sawn oak with ply gussets. Thanks for the pics. Thats a fine looking rig there. Similar to what I was intending. I bought this one about a week before our first snow. Since then we've seen about 15". The first day of winter and I'm dreaming of spring!

Bob Smalser
12-22-2007, 01:22 AM
What do think if I reduce the width of the #3 thwart (maybe double the thickness?) and put in the bench?

If your thwarts are say, 5/4 X 8 or so in a fairly stiff species like spruce or Doug Fir, I think you could reduce the width of #3 down to as narrow as 5 inches in order to make it easier to step over. I'd have to play with some paper patterns of the profile however, to get a look I liked to blend the benches fairly to the thwart.

http://pic20.picturetrail.com/VOL12/1104763/7711190/101687781.jpg

To let in your benches, cut and fair the male laps first, fit onto the tops of your thwarts and scribe the profiles of the mortises required. Used with care, a heavy router can be freehanded to cut the mortises. Rout just shy of the scribed line, then clean off the flash caused by the bit with a sharp chisel so you can see the line clearly for your final cut.

Thorne
12-22-2007, 02:07 AM
I take it that the thwarts are fixed onto the riser, and/or attached to the frames as in Bob's example? Do they have knees to hold them in place?

The thwarts in my Chamberlain dory skiff fit fairly loosely and didn't bear against the hull (like removable thwarts in a Banks dory), so I replaced the rear one with sternsheets without worrying too much about the loss of the structural member. So far so good, not too much movement of the rear frame.

http://www.luckhardt.com/newyoke3.jpg

But as Bob says, sailing puts a lot of stress on a light hull, so you need all the help you can get, particularly if you remove crosswise bracing.

andrew scease
12-22-2007, 03:27 AM
Thanks for both of your replies. I think I'll keep a narrower thwart at #3 and include the seats fastened to the riser. If it was the aftermost frame I wouldn't worry so much. As it is so close to the beam, I think you're right, the support is necessary. Thanks for the pics of the mortising. Much prettier than what I had in mind. I think I'll sail her for a few weeks this spring to see what works best for movement.

elad
01-23-2008, 09:33 PM
Thought I'd add a picture of the bench seats I add to my swampscott. It made it much nicer when sailing.
Dale
http://i77.photobucket.com/albums/j48/elad12/swampscott2.jpg

andrew scease
02-02-2008, 10:17 PM
Thanks Elad,

that looks something like what I had in mind. Are the benches notched for the frames? That looks pretty stiff.

NHDORY
02-03-2008, 07:46 PM
Elad, Is that a traveler set up on your Dory? Does it work well for you?

elad
02-07-2008, 09:00 PM
Andrew, Yes I just cut a notch out to fit around the ribs. The seats just overlap and sit on the thwart where they are just attached with 2 bronze screws.

N H Dory, That is a traveler, just bronze rod. I have a wooden block that is normally there. Works great for the mainsheet which then runs thru a cam cleat located just below the forward edge of the seat there (right about where that oar is pointing.

Dale

NHDORY
02-07-2008, 10:49 PM
Elad, I've been thinking about doing the same thing on our Swampscott Dory (built by the Landing school, not me) but was concerned the range of the tiller handle would be restricted by the traveler.

I don't suppose you have any photos of what the set up looks like when sailing?

elad
02-08-2008, 08:40 PM
Here are 3 photo's I took today in my shop showing the mainsheet going thru the block on the traveler, then to the cam cleat. It looks like it might get in the way of the tiller but it doesn't really. The only thing is that when changing tacks you have to bring the mainsheet up over the tiller. Also I don't use the cam cleat on short tacks or in questionable airs.
Dale
http://i77.photobucket.com/albums/j48/elad12/trav4.jpg
http://i77.photobucket.com/albums/j48/elad12/trav2.jpg
http://i77.photobucket.com/albums/j48/elad12/trav3.jpg