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Bending Front cabin trunk question


yoyoecho

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I was wondering if there is a good way to bend the front cabin trunk? Have just tried to push the 1/4" ply up in to place and after about 30 sec there was a crack followed by a snap and I have two bit of ply. Made a second one but this time I put it in water for and hour but this time it snapped before even making the curve. I think that the center lamination might have had a defect. Have lots on wood so I can keep going making them until I get one that works but just wanted to know if there is a better way to do this.

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A few years ago someone else reported having the same problem. It turned out that the center ply had a void down the length of the plywood. He finally got around the problem by using a different piece of plywood. I got around the problem by squaring the cabin front.

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I suggest just wetting the outside part of the trunk so as to expand just that side and cause it to start bending before you put in place. Also make sure the outer lamination grains are running verticle so that the bend is not fighting against the strand of the woods fiber.

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The plywood will have a natural tendency to sluff, (bend a bit) to one side or the other naturally. Take advantage of that natural tendency to want to do that. I would agree that there is most likely a void or weak layer in the center that is allowing it to crack this way. Normally that will not happen with 1/4". The other thing is to use double layers and pre bend it into a "U" shape with a length of rope. Allow that to set overnight and then it will slip right into place as the plywood gets a chance to relax a bit.

You can also wet it down by laying it in the bathtub and weighting it down for a while. Then flex it into the "U" shape and tie it and let it set overnight before installing it.

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I lost my first piece in much the same way. I had pre drilled the screw holes in the ply and found that the ply failed right at the centre hole, so for the next piece I pre drilled all the screw holes except for the middle one and one either side of that. Single handed and using a rachet 'tie down' around the whole piece she went on a treat.

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I had the same horrible experience so I found a piece of bender board, 3/8" luan with a single ply in the middle. Worked like a charm. Check out a store fixture manufacturer. They use it on the bases of display cabinets, etc. I just happened to have a piece laying around and had just enough. Stained up real nice inside like mahogany.

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Thanks to everyone. I have the part cut and pre bent I think the problem was the ply but will be fitting this weekend (bad weather and work at the end of the week and did not get to work on the boat). Tim let me just say that you make me sick. "gluelam veneers in my vaccum bag" just do me a favor next time that you are going out sailing let me know, and where you keep your keys. I will stop by to use your tools. Your stuff always looks so good. :) Will post some pic's if it does not snap and if it does my wife might post some of me rolling around in the grass kicking and screaming.

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Will post some pic's if it does not snap and if it does my wife might post some of me rolling around in the grass kicking and screaming.

Before you do the job, go out and rent a digital video camera and have your wife shoot the whole thing.....we need some action shots!

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Will do my camera can record up to 1 min video but I think 30 sec's should be all that it will need. No one wants to see a grown man cry. Okay this group might :D Put off fitting it today had to cut grass and get the flotation to put behind the seat and wood for rafters (stalling) but tomorrow is boat day, got all of the "honey do list" done even new stairs for the deck (house deck not boat deck)

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