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PostPosted: Sat Apr 27, 2013 9:48 am 
Brotherhood of the Golden Paddle

Joined: Sun Aug 16, 2009 10:05 pm
Posts: 1398
Location: South Salem, NY
I have a tendency to leave my boats; Klepper and Long Haul, put together for long periods of time during the useable months. I always keep them covered but often forget to let the air out of the sponsons. I haven't had a sponson blow on me but I've ended up with a lot of warping on my bow and stern pieces. So the first lesson I believe is to let the air out of your sponsons completely if you are going to leave your boats set up.

Mark Eckhart at Long Haul told me he that he thinks leaving boats together for long periods of time is the number one cause for bent and warped frame pieces. I'm adding the thought that it's air in the sponsons that keeps the frame taught and thereby causes more warping. The thinking being that a loose hull on the frame won't cause this...?

Anyway, I had a bent AII stern piece that I hadn't used in a couple years because of the warp and decided to play with it. I did some reading online about straightening bent wood and got the impression none of this wood was coated the way ours are. To make a long story short I took my iron that I had just finished ironing today's work shirt with and went outside the kitchen door with the iron still plugged in. I soaked a T-shirt with water and laid it over the bent stern piece. I ironed the shirt close to dry several times heating the wood over and over while pressing down against the warp. I did this several times and started to see some progress much to my surprise. By the end of a twenty or so minute session the board was very hot and I was actually able to bend it with my hands - gloves would have been a good idea. There's still a vey slight warp in the tailing edge but for the most part she is straight again. I'm actually kind of amazed that I did this. Even though I felt bending with my hands I think most of the work was done with the pressure of the iron.

I let the piece lay out last night and am happy to report that it seems to have kept it's 'straightened' shape.

Most of the instructions I read about straightening involved wetting the bent surface and this water absorption would straighten the wood. My piece has a thick coat of varnish on it from a year or two ago - no absorption here. So I think it was purely the heat softening the glue and wood allowing it to be bent back in shape. I also worked the piece until the wood had cooled back down.

This is obviously old school for many woodworkers, but I've never seen it mentioned here.

Dennis

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Klepper Aerius II
Klepper T9
Long Haul MK1 Expedition 'light'
Klepper S4 sail rig
Kayaksailor 1.6 +genoa
BSD 36HP


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PostPosted: Sat Apr 27, 2013 9:07 pm 
Site Admin

Joined: Thu Apr 14, 2005 12:34 pm
Posts: 1719
Location: Southeast Michigan
You might have to touch up the finish after that.

Old time gunmakers used to bend shotgun stocks to adjust the cast-off by pouring hot linseed oil over them while applying pressure. Same basic idea; you soften the lignin in the wood, making it pliable. A friend and I tried bending a stock using heat lamps, which worked very well. Should work with frame parts, too. Just keepte wood far enough away so that it does't burn the wood or the finish.

I don't think the sponsons have any affect on the frame parts. They just snug the skin around the longerons that are already under plenty of stress just from being bent around the frames.

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PostPosted: Mon Apr 29, 2013 8:16 pm 
Brotherhood of the Golden Paddle

Joined: Sun Aug 16, 2009 10:05 pm
Posts: 1398
Location: South Salem, NY
I always had the impression the expansion and contraction that occurs in the sponsons would also have an effect on the pulling this way or that on the frame. I'm pretty sure I heard it here or somewhere related to folding kayaks. I think Mark has told me that proper inflation is an important step to maintaining an even keel - perhaps I took that one step further in my mind.

Can you describe how you used the heat lamp(s) to heat the gunstock? I'm thinking I might like to give that a try. I was going to try really hot water next, but the next bow piece is a little weak on varnish and I don't want to damage the wood anymore with hot water submersion. The other solution I've seen is to make a steam tube with an electric 'tea pot' underneath sending hot steam up into the tube. I've seen this for steaming long pieces of wood. Maybe I'll ask my friend Google for some more steam ideas. The iron worked, but it was a chore and as you said, the varnish could have been compromised - although it doesn't look it.

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Klepper Aerius II
Klepper T9
Long Haul MK1 Expedition 'light'
Klepper S4 sail rig
Kayaksailor 1.6 +genoa
BSD 36HP


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