shaping foam for aero rudder

[waterwks4me]

I am sure it has been mentioned in other posts concerning making an aero rudder but I can't seem to find it.  What type of shaping foam are you guys using to make your aero rudder.  I am ready to start the project but not quite sure what foam to use.  Thanks for any input.

[MacGyver]

You can go to any home depot, or Lowes, etc type store and buy by the sheet a Blue colored foam by DOW Chemical that is used to insulate houses.
This foam can be bought in varying thicknesses, and has a plastic liner sheet on I think half inch and below. Be sure to remove that sheet when using the foam as it is only a stabilizer for the foam since it comes in 4X8

I think I used 2 sizes only because I had it on hand from a home project.

Mac

[wroundey]

How are you shaping the foam? What are you using to cut/shape it?

[Vipersdad]

Do a thread search on the forum for a link to Mike Greene's photos when he did his.  If you search for "foiled rudder" it will come up.

V.

[NateD]

I used the pink foam board, and used a SureForm to shape it. Here is my write-up: http://cpyoa.geekworkshosting.com/forum/index.php?topic=5072.0

[Jon898]

I've never done this and certainly haven't tried it for a NACA rudder foil, but a method that is used for RC planes/gliders to shape a nice airfoil wing is to use a hot wire run over a foil template.  The hot wire is typically a guitar string with the heat from a step-down transformer attached via alligator clips to the section of wire needed to do the cutting.  Since most plane wings are tapered, usually this is done using one fixed end and a single template on the thicker end, but I don't see why this would not work using a template at each end to get a constant foil shape the length of the rudder.  There are plenty of UTubes that show this (e.g. http://www.youtube.com/watch?v=ckxnNRSM3YE ).

Using a hot wire would seem to avoid a lot of messy sanding and offering-up of templates to check the shape.

Anybody have experience of this?

[waterwks4me]

Thanks for the information.  Nate, where did you get the pink foam?  MacGyver, yes I did see the bluish foam boards in Lowe's but wasn't sure if it was the foam I needed since most pics of homemade aero rudders seemed to have used pink foam.  John898, yes I saw the youtube video on cutting the foam with hot wire but I believe I am going to use the SureFoam to shape it.

[NateD]

Thanks for the information.  Nate, where did you get the pink foam?  MacGyver, yes I did see the bluish foam boards in Lowe's but wasn't sure if it was the foam I needed since most pics of homemade aero rudders seemed to have used pink foam.  John898, yes I saw the youtube video on cutting the foam with hot wire but I believe I am going to use the SureFoam to shape it.

I probably got the pink insulation from a home improvement chain up here called Menards (a lot like Home Depot or Lowes). I don't know if there is any difference between the pink and blue. Menards, Home Depot, and Lowes all have website where you can check the availability of products in stores near you, so it should be easy enough to find whatever color tickles your fancy.

While the wire cutters look pretty slick, the SureForm is about $5 and simple to use. Yes it takes more time and creates more mess (although less mess than I expected), but if you're only going to make 1 foil every couple years, it's simpler than a hot wire cutter.

[Greene]

After making a foiled rudder for our Com-Pac 16 using the Sureform I decided to try the hotwire method when I purchased a Com-Pac 19.  I bought the wire from a local hobby shop and made up a frame out of oak.  Then I built a wooden guide for the wire to follow which produced the correct shape.  It worked great, but all told it was a lot more work than the simple hand forming method.  There was little if any difference in the final results.

When I made the third foil (Com-Pac 23) I had my choice of methods and I opted to do it the simple Sureform method.  Guess that tells you which method I would choose. 

Not:  Make sure you use epoxy resin, not polyester.

Mike

[Jon898]

Mike:

Thanks for the info...good to know.

Jon

[waterwks4me]

Thanks guys for the information.  I'll let you all know how it goes.