my36 Posted February 5, 2011 Report Share Posted February 5, 2011 I'm a first time, novice builder. Things were proceeding nicely until I tried to open the butterfly and start wiring the chine. First time I tried, the butt join at the stem cracked. I sanded it down some and added another layer of tape and let it cure 48 hours again. It started cracking again when I started wiring the sides to the bottom. Is there a trick to this? Any thoughts on how to proceed? Quote Link to comment Share on other sites More sharing options...
ChrisObee Posted February 5, 2011 Report Share Posted February 5, 2011 I'm a first time, novice builder. Things were proceeding nicely until I tried to open the butterfly and start wiring the chine. First time I tried, the butt join at the stem cracked. I sanded it down some and added another layer of tape and let it cure 48 hours again. It started cracking again when I started wiring the sides to the bottom. Is there a trick to this? Any thoughts on how to proceed? A picture would help. The best thing about this sort of construction is that anything can be fixed with a little sawdust and a bit of goo. Quote Link to comment Share on other sites More sharing options...
hokeyhydro Posted February 5, 2011 Report Share Posted February 5, 2011 A trick I read about somewhere on this forum (I think) was to screw a small block of plywood (maybe 3" x 3") across the butt joint at the aft end of the joint, as in away from the stem and toward the stern. Quote Link to comment Share on other sites More sharing options...
Ken_Potts Posted February 5, 2011 Report Share Posted February 5, 2011 A trick I read about somewhere on this forum (I think) was to screw a small block of plywood (maybe 3" x 3") across the butt joint at the aft end of the joint, as in away from the stem and toward the stern. That worked when I broke mine. It's a heartbreaking sound when it breaks, isn't it? I screwed two blocks together like a clamp across the back end of the butterfly and removed the "clamp" after everything was pulled into shape and the joints were cured. Quote Link to comment Share on other sites More sharing options...
Scott Dunsworth Posted February 5, 2011 Report Share Posted February 5, 2011 I always use two or more layers of glass on the butterfly inside and out. Also make sure they are long enough. You can after the epoxy has cured go back and add wires tightened down Say every inch of the glass,at the area that's giving you trouble. That should allow you to open her up. You are going to see some discoloring in the glass as its stressed where the epoxy and glass are trying to give up. But unless your being very rough on it she should hold. Also get two friends to hold the hull sides up as you wire down the chine. The wood block only really helps if you have a long floppy hull panel. Scott Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted February 5, 2011 Report Share Posted February 5, 2011 I always use two or more layers of glass on the butterfly inside and out. I used 2 layers on the outside when I did my Spindrift. It is the outside that gets the most load when shaping the hull during the stitching phase. But I think in your case my36 I would also use a "clamp" as others have described. You have already had more than your share of trouble here. Quote Link to comment Share on other sites More sharing options...
Designer Posted February 6, 2011 Report Share Posted February 6, 2011 Newbie, I hate to hear this. There are several possibilities as to what went wrong. First is the plys, some plys bend better than others. We started having some Spindrift bows break in my boat building class but when I folded the same ply at my shop it worked fine. I concluded that the controlled environment inside the community college was drying the ply and making it stiffer to bend. We started soaking the bow area inside and out with hot wet rags just before folding and have not broken any more. There is a lot of peel stress on the aft edge of the glass tape during the folding operation. It is important to screw the blocks mentioned in the plan. I have not had any failures when using the blocks. What happens is the zipper effect, the aft edge of the tape is highly loaded and it lets go which moves the stress along until it fails which moves the stress along etc.. Quote Link to comment Share on other sites More sharing options...
my36 Posted February 6, 2011 Author Report Share Posted February 6, 2011 Thanks everyone for the comments and ideas. I'm using 6mm Joubert Okoume plywood. I suspect the problem is that my basement is VERY dry in the winter. I will try Graham's idea of adding humidity with hot rags. I may even mist the panels with a misting water bottle. I did not see anything in the plans about screwing a block, I only read about it here. I'll look again. I plan to unwire enough so that I can add a second layer of tape and epoxy. Is there any reason to worry about the extra layer of tape and epoxy being more than the plans call for? Quote Link to comment Share on other sites More sharing options...
Ray Frechette Jr Posted February 6, 2011 Report Share Posted February 6, 2011 Is there any reason to worry about the extra layer of tape and epoxy being more than the plans call for? Boat might be a bit nose heavy. You may need to add a few stainless steel washer to the transom to trim the boat right in the water. Quote Link to comment Share on other sites More sharing options...
hokeyhydro Posted February 6, 2011 Report Share Posted February 6, 2011 Boat might be a bit nose heavy. You may need to add a few stainless steel washer to the transom to trim the boat right in the water. Right, Ray. I did some quick math: figure 10 oz tape = 10 oz/per square yard and 60% resin content for a hand layup = 25 oz, BUT he will be using an itty bitty piece so WAG square inches and dividing by micro-ounces of a 1/4 ss washer I get 6 1/2 washers needed to counterbalance the additional nose glass. Might be off a tad since I used a gram scale to weigh the washers Quote Link to comment Share on other sites More sharing options...
Ray Frechette Jr Posted February 6, 2011 Report Share Posted February 6, 2011 Right, Ray. I did some quick math: figure 10 oz tape = 10 oz/per square yard and 60% resin content for a hand layup = 25 oz, BUT he will be using an itty bitty piece so WAG square inches and dividing by micro-ounces of a 1/4 ss washer I get 6 1/2 washers needed to counterbalance the additional nose glass. Might be off a tad since I used a gram scale to weigh the washers I would just float it once done and add a few washers till it look right by eye. Quote Link to comment Share on other sites More sharing options...
Designer Posted February 6, 2011 Report Share Posted February 6, 2011 6mm Joubert ply is as good as it gets. I looked through the plans and there is no mention of the reinforcing blocks except in the CD of building pictures. Here is the picture. Quote Link to comment Share on other sites More sharing options...
ilnadi Posted March 13, 2011 Report Share Posted March 13, 2011 Is there any bend at that butt joint once the boat is 3D? If not, would it not be better to add longer reinforcing blocks to hold the seam flat? Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted March 14, 2011 Report Share Posted March 14, 2011 The butterfly starts to crack at the aft end and it then continues like a zipper. You only need to stop it from starting. Quote Link to comment Share on other sites More sharing options...
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