I’m sure we have all walked or driven past a dumpster / skip and seen an old Venetian window blind.
Well I can tell you that they make the most wonderful keels and rudders.
I salvaged two red ones the other day, stripped them down to get the 25mm slats ~ I have realized that they make rudder and keel building a breeze.
For the keel I used some threaded stainless rod - drilled the 4oz fishing weight put a nut on the end and tapped it back into the lead so as to bury the nut
The slats can be cut with scissors - tape two edges together - CA the rod in position - CA the two slats together and clamp - I have also tried this with building foam between the slats and found this works just as well
I still like my rc chopper rotor blades…a bit more $$$ though…but if built properly you can move them from boat to boat and not have to build a new one each time…
Andy - I do something similar but I cast carbon fiber sheets inside a old, 16 inch diameter plastic planter as my curved material source.
Construction is similar except I use a filed down nut that is epoxied about 1/4 of an inch up inside the skins at the location of maximum chord. The bulb is then bolted onto the keel with the head of the bolt and its washer countersunk into the bulb. Plastilene is a good material to fair out the countersunk hole temporarily. Once I’ve decided that I like the weight and the placement of the bulb I fiberglass the bulb in place.
Marc - I use a thin balsa rib down the maximum camber location (my rudder shaft only extends about 3/4 inch into the rudder), and a similar but thinner piece along the leading edge to hold the skins slightly apart. I like the leading edge to be a bit blunter than the trailing one. I fill the voids with West 105 epoxy thickened with Microlight 410 filler and graphite powder. I don’t use much, just enough to seal the the gaps. Before Ca glueing the skins together the inner face of the rudder skins are roughed up with sandpaper. This helps make a better bond with the various adhesives.
on the one with no foam I just let it free flood up from the bottom - I figured it was easier to do that than worry about it
The foam one is of course completely filled with foam and the foam sticks the whole together as it cures. I did this on the rudder section with a fiber glass rod to which I fixed the rudder horn after it went through the rudder tube