NACA-0014 Rudder Modification Underway

[Bob23]

Just to let you know that I'm lurking in the shadows and taking in all this information, trying to assimilate it into my grey matter before I begin my rudder project. I'll either photo chronicle it here or start a blog.
Bob23

[Salty19]

Just an idea to save weight on the rudder.   Drill several (perhaps 50-75, maybe more?) 1/2" holes evenly spaced throughout the aluminum blade, sand smooth..then glue the foam on. The idea here to keep the structural integrity intact while removing some of the heavy material.  The foam and glass will add strength back. If I recall correctly, I read a post on another forum about doing this with success.  Your mileage may vary.

IDA chose the NACA 0012 blade shape for Compacs on their foiled rudders after testing various forms.  Doug tried the 0014 design as an experiment.  And judging from his boats' speed (sailed w/ him 2 years ago), as well as his reviews of the performance, no question the 0014 works quite well.  Probably splitting hairs between the 0014 and 0012 on our little cruising boats.

[kchunk]

Salty, that's a good idea, but without calculating anything, I wouldn't be surprised if the increased buoyancy from the foam on the rudder actually made it float. At the very least it'll probably increase the buoyancy of the new rudder assembly, acting against whatever method you use to hold the rudder down when sailing.

--Greg

[nies]

Salty, my Ida rudder has positive buoyancy and had to rig a tension line to keep her down. I believe you will need all the weight to keep her down,.....Phil

[Bob23]

I plan on installing a downhaul line to solve the buoyancy problem. This worked well with my old SeaPearl 21. Haven't worked out the particulars yet but all these brainstorms start with pencil and paper and morning coffee.
Bob23

[Salty19]

I figured every bit of reduction of weight adding to increased buoyancy would good thing, what with thee heavy 4 strokes and all, but can see your points about holding the rudder down.  Would be cool to fit something like what the IDA rudder assembly has to keep 'er down and let it come up when grounded, then pushes it back down. Something like a truck engine hood auto-raise rod/dampener .

Let me get a pick and I'll post it.  Bob you may need a second or third cup to think this one through

[Craig Weis]

Don't need to hold the rudder down if she's bolted down with a sheer pin from a snow blower auger.
The keel hangs lower and I don't usually run aground going astern. Some 6" deeper then the keel. Really?

Saber Saw out a rectangle hole in the aluminum blank and pour in some lead protruding out on both sides. That will hold it down. File to shape, then glue on the foam, cope the foam around the lead and shape all that to the foil. Glass over the works and paint.

skip.

[Bob23]

ps: on my 23, the rudder draws 6 inches more than the keel. I guess the 19 is different.
I may need espresso for this one...with Sambucca!
Bob23

[nies]

Skip, with my great sailing ability I have sailed backwards.............Phil

[brackish]

Actually, if you can keep it down, a little more buoyancy in the rear would be a good thing.  Offset some of the weight of these heavier, four stroke, motors that are hanging there.

[kchunk]

Drill out a pound of aluminum? I suppose in theory you're right, but the difference would be negligible.

[Greene]

Step 2 nearing completion.  I ended up using a Shur-Form and sanding pads to shape the stryofoam even though I did make a hot wire foam cutter.  The foam cutter really would be the way to go if you have one.  My cobbled together power supply included a used furnace transformer which worked really well for about twenty minutes while I practiced.  About the time I was ready to use it on my templates it gave up.  Oh well, back to hand shaping if I want to get Step 2 done this weekend.

The hand shaping really isn't difficult or time consuming, so it worked out pretty well.  As you can see in the pictures it shaped up nicely. The rectangular sanding pads they sell at the hardware store for drywall sanding really work great for final shaping.  I didn't want to end up with the rudder lifter/holder line going through the stryofoam so I tapered the top edge down slightly to end just below the 1/4" hole for the line.  I don't think this will be an issue, but I'm not sure.  Any opinions?
Since the nose piece (wood) was already finished I ground out the nose portion of my template to make it easier to slide it along the rudder.

Next up will be coating it with epoxy resin fiberglass.

[kchunk]

Mike, that's really coming out nice! It's going to be such a drastic improvement, not to mention the satisfaction of doing it yourself. Way to go!

--Greg

[Bob23]

Mike:
   Thanks so much for the great photos and live coverage of this news event! It's helping me re-think a few steps in my own rudder project which, for now, resides only in my grey matter.
Bob23

[Craig Weis]

That tiny bit of foam and wood will not displace enough water to make a modified and foiled rudder float. Do the math, or better yet just think about it.

skip.