Thursday, April 17, 2008

Better results on the bulkheads

Well, in my last post I thought there might be an issue with the Divinycell foam. This was certainly not the case, and I think I was hasty in publishing that post. As Tor commented, my problems were certainly caused by something else. I may never be sure.

Things are going much better now. After work today I cut the glass, the peel ply, the plastic sheet, measured and mixed the epoxy and completed the above lamination for the standard cabin bulkhead in 1 hour. I could never do that vacuum bagging.

Sunday, April 13, 2008

Starting lamination of main hull bulkheads - a problem with using plastic over the peel ply

It has been hard to find time lately to work on boat parts. Same old story, too much time at the day job. That said, the little boat building demon in me will not let things stop totally. I started a test part ( the small middle forward bunk bulkhead) with the plan to do one side at a time going for a hand lay up, using peel ply and the plastic so that I could squeegee the air and excess resin out. To my surprise I found out that using the plastic on one side of a foam piece will not create the vacuum that I have seen elsewhere on the outer float hulls. After I would compress the foam, air would reappear underneath the plastic sheet. I can only deduce that the Divinycell foam that I am using is not totally closed cell in construction. I will be running out of Divinycell sheets at some point fairly soon. I think that I will make the main hull out of Corecell, especially if the foam turns out to properly closed, in other words, one side of the foam air isolated from the other.

So, for the moment I am just using peel ply as I can knock them off pretty quickly, laminating one side at a time. The epoxy weight to cloth weight ratio is alittle over 1 on the first part (ie epoxy weight/cloth weight) but I can live with that. I could go back to vacuum bagging the flat parts but it will require a setup of a larger table and I can't seem to find the time.

There are other techniques I can try. No doubt by the time I have all the bulkheads done it will be quite optimized. I can see why that after building the first boat some people just have to build another. All these skills that have been mastered and optimized for ones own personality, just have to be put to some use!

Sunday, April 06, 2008

Main hull bulkhead outlines transferred to the foam

It is not very exciting work, but transferring the full size plan outlines to the foam is challenging in its own way. The many bulkheads parts have to located in the sheets, then they have to be correctly aligned and taped together. I've used 8"x11" size sheets of carbon paper, this means that on some of the larger bulkheads there are 'many' carbon sheets to keep underneath the lines that you want to transfer. Not a difficult job, but tedious.

Here is a picture of one of the sheets of foam with the bulkhead shapes ready cutting out and laminating. You can see that I go over the carbon trace with a permanent marker.

I'm thinking about doing these panels differently from the float bulkheads. Back then I cut the parts to the exact size and proceeded with the two sided vacuum bagging technique. This time I may cut the parts with about an inch or so of extra material around the perimeter. Then after lamination cut them down to the exact size. I'm also thinking that since my 'hand lay ups' with peel ply and plastic is getting so good I just may carry on with this technique on these panels.