Gutters

Years ago, when I first conceptualized the doghouse, I decided just to have a large removable sliding hatch that extend far enough forward that the keel could be raised through the same oversized opening.  This forced several undesirable outcomes.  One is that my hatch doesn't push very far forward when opened. Another is the top of the doghouse had to be made bone straight for the entire length of the hatch and garage.  Finally, the gutters, due to their length, would not have much pitch, and might trap standing water.  I thought about lot's of creative drain solutions, but in the end, decided on a pretty standard approach, and I worked hard on keeping the whole assembly snug enough to inhibit any large influx of wave water.

After lots of sketches, my build started with the gutters and the integral garage for the slider.  One of my biggest concerns was matching the arc-shaped top of my doghouse.  I checked the as-built curvature with a deerskin template, and set to work to model my part in Rhino.  Once I had a plan put together, it was a joy to test my skills with a slightly more complicated mold on the new CNC.

Here the new CNC is going to work on a glued stack of MDF.  I started with an approximate shape, but I still filled the dust collector straight away.

From there I moved the mold over for some sanding to reduce tool marks, and added a few coats of West Systems, using the clear 207 hardener.  I used the wet on wet method, re-coating several times when tacky to build up a film gauge to sand against.

For my final coat of resin, as I've become accustomed on MDF molds, I added white pigment.  This can help when you want to gauge how much material you are removing.  The pic below shows the beginning of the layup.  I added some fairly significant layering along the U channel, as in addition to serving as rain gutters, this part is designed to stiffen and strengthen the roof of the doghouse.

After curing, I put the mold back on the router and cut the part directly to final outline.  The trick is to index it in the right spot.  I have some alignment pins on my machine bed that made this straightforward.

I'm pretty excited in this pic, as this is the first dry fit of the part.  I attached it with machine screws to check it all out.  The curvature is a close match to the transverse arc of the roofline.

I had to adjust the front lip of the garage, so I made a trench out of some mylar film and built it up with bog, followed by some carbon to add stiffness.

For a sliders, Paul Bieker suggested I perhaps try with skived PTFE.  You can buy strips of this stuff from McMaster Carr that comes chemically etched on one side to enable bonding with epoxy.  I am somewhat worried that it's too soft to wear well, but it's slippery as hell, and it won't crack and craze like the other white plastic options.

As sanding is easier on the bench, than on the boat, I rolled some 410 on the part and did a initially fairing.

Finally, I glued the part in place.  Some of the #10 screws got pretty saturated in resin, so I got them moving and extracted with the help of an old soldiering iron.