NACA-0014 Rudder Modification Underway

[Greene]

I got started on my rudder upgrade project today.  I am going to modify the flat plate on my '84 CP16 to a NACA 0014 foil.  I admired the pictures of Doug's foil (Doug142) and he kindly supplied a template printout of the foil shape.   I am going to use a hardwood leading edge and pink styrofoam filler covered in fiberglass.

The first step was to make a maple leading edge to give the rudder some impact protection.  I'm posting a couple pic's of the nearly finished piece.  I followed Doug's advice and have added 1" to the leading edge so it will end up 13" wide x 22" tall. 

[Glenn Basore]

This will be an interesting project to follow.

Keep us posted.

[Bob23]

Greene:
   This is perfect timing as I'm about to embark on a similar project. I'm also going to turn my 23's flat plat to a NACA 0014 foil only instead of foam, I plan on using a series of foil shaped blocks and a hardwood leading edge just as you are. The "framing" will be wrapped in an 1/8" mahogany plywood and fiberglassed, giving the look of a wood foil rudder. My son, who builds surf boards, will fiberglass it for me- he's a better glasser than I.
   I plan on chronicling the process but, as of right now, don't know how to post photos here. I guess this is a good time to learn!
Bob23..thanks

[Greene]

Bob,

Your project sounds a lot more involved than mine.  As a tinkerer I look forward to seeing your project come together.  Lucky for us we can just follow Doug's (Doug142) lead and profit from his advice and experience on these projects.  I'd like to see someone else try a NACA-0012 foil on a 16 so we could compare them.  Any takers?

Last night I tested some old fiberglass resin I had laying around on a couple brands of pink polystyrene.  The resin ate the foam like I eat chocolate.  Doug was kind enough to remind me to look for an epoxy resin instead of the polyester resin.  That epoxy isn't supposed to eat stryofoam.

Mike  

[Craig Weis]

I was thinking of a slightly different foiling method. Using one of two methods.

#1
~Start with the factory aluminum blade. As this blade has the correct depth and width for the hull's design.
~The leading edge would have a nice hardwood leading and trailing[?] edge prescribed to foil's shape.
~Glue on a single layer of pink foam board insulation. Both sides.
~Sand the foam board to the foil's shape.
~Shape and check the foil with templates.
~Using a woven 1-1/2 once fiberglass cloth saturated with West System epoxy...
~I'd wrap the glass cloth round the leading edge and over lap at the trailing edge. Pulling It tight.
~Sand her out when cured. And paint it.

#2
~Aluminium blade.
~Shaped hardwood leading edge.
~Glass cloth wrapped around leading edge.
~Pulled tight all the way to the trailing edge of aluminum blade.
~The glass cloth would not be touching the blade between edges.
~Leaves a hollow blade between the two edges.
~A couple of 1/4" drilled holes to let water flow in and out, when down or pulled up.
~The rudder would be flat sided. Is that OK? Don't know. Foiled? yes.

Note that when the epoxy cured and was sanded and low spots filled
the rudder 'would be stiff as a wedding cock' as they say. You won't be able to punch through the hollow part.

Bare in mind that the IdaSailor rudder is 3 lb heavier on land and 3 lb lighter in water then factory rudder.

skip.

[Greene]

Skip,

Your description #1 is exactly what I planned on.  I don't see any need for hardwood at the trailing edge.  At that point of the foil there is very little Styrofoam thickness, just metal.

I figure if it doesn't work all I have to do is clean the stuff off the stock rudder and I'm back where I started.  Well, maybe $30 poorer and I will have entertained myself through a couple weeks of this stiffwater season.

Mike
   

[kchunk]

I've thought about this project too, but I'd try to cut the foam with a hot wire over plywood templates. Cutting plywood in two dimensions is easier than shaping foam in three dimensions. One thing to consider though, I agree that epoxy fiberglass is the way to go, but keep in mind, UV will destroy the epoxy so plan accordingly. See if you can find some sort of UV inhibiter to use with your epoxy and/or keep it painted.

--Greg

[Craig Weis]

Don't cut with a hot wire. Use a sanding block and smooth your way to that perfect shape.
Takes about 25 minutes per side I'd guess. Check with a cardboard template cut from the foil picture.

kchunk...Well Ok then Hot Wire it is. Nothing wrong with it. I make my model boats out of glued blocks of foam and sand to shape using templates. I have zero experience with hot wire, never thought about a battery charger. Hummmmm wait! Maybe going in the house and saying to the wife, "I'm energized" will work.

I don't really cotton to R/C aeroplanes that are A.R.F.'s. I like building with balsa, stick and tissue. Some how they come out lighter in weight then the foam guys. Of course I sand almost every stick to nothing before I super glue it together. Maybe that's where the weight goes? My nephew holds my 14 ounce-72" wing span-two channel Carl Goldburg's Gentle Lady. I still have it with a .051 power pod. Boy does she fly nice. I going to fix her up with new battery pacs and give this plane to Dylan. He flys it pretty well. Uncle skip is trying to guide him into being a Corporate Pilot, both fixed and non-fixed wing craft.

West System epoxy is fortified with UV resitant polyester blend.
Think yard furniture.
If the paint goes chalky then there was no polyester in the epoxy powder paint coat used to coat the furniture.
This is present on cheaper Wal-Mart brands.

http://www.finishingtalk.com/community/

skip.

[kchunk]

Don't cut with a hot wire.

Well, cutting with a hot wire is only my opinion. And what do I know...other than that's how they taught us to make composite aircraft wings and control surfaces in A&P school. I suppose both methods will result the same product. Sanding to match will get you close, a hot wire will be dead nuts...just my opinion...

[kchunk]

After a brief search on youtube I'm certainly convinced that a hot wire is the way to go. Apparently the R/C aircraft hobby has adopted this method and you can find anything from complex CNC cutters to the most simple homemade solutions using a battery charger as a power source. This particular example was rather impressive:

http://www.youtube.com/watch?v=R0ZCnR_g6ZU

I was picturing using a positive template and running the wire along the outside of the template, but this guy shows a pretty good example of using a single negative template to quickly make a tapered wing. Pretty sweet!

--Greg

[Craig Weis]

That was a really cool hot wire video.
What is the template made out of?
I think the trick is to keep both ends
of the wire level so the core is the
same thickness/shape both ends.
Is the held end insulated against
heating and applying voltage to the hands?
Looks easy. Too easy.

skip.

[kchunk]

The way you'd do it for a consistent wing section (like a rudder) is to put your wire through a bow and use two templates. The bow will keep it taut and allow you you follow the outside of the positive templates. The templates can be cut from plywood. I saw one video on youtube where the guy started cutting his templates from formica. Said that his plywood templates were so used that they were starting to develop flaws over the years.

Here's a link for a NACA foil generator:

http://darwin.wcupa.edu/webapps/javafoil/

I still have my old rudder blade and keep thinking to myself that I need to try this...partly because I keep bending my IdaSailor rudder.

[Greene]

Gee thanks a bunch  kchunk!  Now I have to build a hot wire foam cutter to complete this project.  The Admiral said to just hand sand it like I originally planned on.  (i.e. "You don't need another tool.")  But the tinkerer in me just loves a new tool/toy project.  Lets see, I have a used furnace transformer 24volt/40VA for the power supply and plenty of hardware junk around the house, so all I would need to buy is a 5' chunk of Nichrome wire ($3.50)   Sorry Admiral, it is kchunk's fault.

[kchunk]

Don't mention it 

Sounds like you got everything you need. If your wife gives you grief over the $5.50 let me know...I'll spring for the $5.50.

Watching that guy cut that tapered foil by fixing one end of the wire was a great idea for a swept wing.

How are making your foil template? I was thinking of using the foil generator from the link in my last post, printing out a 0012 or 0014 foil and taking to kinkos and getting them to enlarge it to what ever size I needed and transferring the paper template to a pair of plywood templates.

[Greene]

My wife would never gives me grief, just love and admiration.  Well .........maybe she just tolerates me.

Doug142 printed out a set of 14" templates for me and I have transferred them to wood.  Hopefully I can find some time this weekend to make my new foam cutter and spend some time building the rudder.  

Just keeping busy until the lakes start cooperating.