Re: Winter refit - transom
Okay...
Notice that in the last pic of the previous post I did something funny with the sticks on the top edge.. the vertical reinforcement is under the lower edge stick, but at the top it's over, and actually has several bits of stick under it to make it meet the horizontal stick.
For some reason this made sense while I was doing this... I was probably thinking back to old projects or something. Anyway, the reason this big space exists at the top of the transom is that there's a "step" in the transom glass. The upper 8-9 inches of glass curves outward from the flat lower section about an inch and a half in the center and progressively less toward the sides.
Looking at this before starting the templating I had decided I'd have to backfill the top section with 1 1/2 inches of plywood and epoxy, so I could have a flat surface for the new full height transom to sit against. The old transom stopped below the step, and I'm working to make the new one as strong as possible.
Here's a pic of the whole mess, you can see the step and the little stack of stick bits:
What I did to repair the botch there was to cut it out (literally) and replace it with a stick "pad" that sits under the top horizontal stick. Basically this holds the horizontal stick off the transom glass so it matches where the plywood transom will eventually sit...on top of the to-be-constructed plywood and epoxy filled area:
Due to the fact that these spacers are in there, I had to switch to using the front side of the template as the one that would lay flat(be the bottom when I use the template). Otherwise the whole template would lay curved on the wood sheet and cause errors larger than I'd like.
Once I had the top horizontal stick in the right place I re-did the vertical support so it was under the bottom horizontal stick (near the bottom of the transom) and I used a short patch section of stick to put it over the top horizontal section.. this violates the desired layering, but since it's a reinforcing piece and won't be measured against this is ok.
I then continued the rest of the way along the top and placed another vertical support. The pads under the horizontal top stick held it in the right place, so I just matched the under/over layering of the other vertical support for this second support.
I continued on into the corner, trimming as needed, placed the second side vertical (again flat against the transom glass) and rounded the final corner, sloping down the bottom of the transom to the keel. At this point I placed a short horizontal piece to "skip" the area of the garboard plug, which I'm going to cover with an epoxy/fiber mix and sculpt instead of just drilling a hole through the transom.
So now we have the whole outline. Something's wrong, though. If you look at the picture you can see that the right side (actually port) is nearer the top edge of the transom glass than the left side. The weight of the horizontal top sticks made it sag a bit.
At this point I could fix it by cutting it apart again, and making the stick sit level. But I decided that would be a mess of patches and trimming, so the easiest thing to do is just extend the existing edge. So I'm violating my layering again. This will make the top of the template sit one stick thickness off the wood... at this point that's ok with me.
I recommend only doing this to "push out" edges at the end of the template construction... earlier in the process it's more accurate to cut it apart and re-do.
So, I added a couple sticks to push out the top edge and then I put in some diagonal bracing on the left side. The braces sit on top of the bottom and the side... boy, I've just thrown my careful layering out the window, haven't I?
Actually the reason I mentioned the layering at all is that it's a good thing to try for. If you can manage to not build your template stair-step at all you'll minimize errors in it and your eventual part will fit exactly right. I'm willing to try for that as I can but take liberties for ease because of what I'm cutting here.. the transom can't fit super tight against the bottom and boat sides anyway since it would be hard to put in place, and I'm going to fillet around it to fill the small gaps anyway.
I stepped back and took another look (and another picture) and I decided that this white outline was where my new transom should sit. So, it's off to the basement and the sawhorses for cutting plywood.
I'm using 1/2" Arauco plywood here. I've posted about it here and there, basically it's a plantation grown pine plywood from South America, made with exterior glue. Production is controlled so that one side of the wood is A grade and the other is B or C. It's fairly pretty stuff, and cheaper than marine ply.
I set the template on the wood with the top edge against one edge of the sheet and one side corner at the sheet corner to minimize cutting and to give me a "factory straight" edge on top. Note that there's some deviation from the template line, but I'd prefer to have a straight edge rather than try to match the glass precisely, I think that'll look better. Silly of me after all the templating work up there, isn't it?
You can just barely see the outline I traced here in pencil. I did the obvious, going around the template, being careful to make my pencil stay as vertical as possible to transfer the template outline.
I used common sense to skip eg. bits of stick corner projecting out and gaps. I then took a straightedge and re-did the bottom where the garboard plug sits manually.. I wanted the wood to extend a bit farther there than that horizontal piece I'd put in... I can always trim it later.
More next post....
