CNC routing blade ribs

[gizmo]

I finally got around to making some foam ribs on the cnc router. These are for a large blade, 2 meters long, with a TSR of 7. The ribs were cut from PVC foam supplied by a fellow windmill builder, Trev. Trev, the local fibreglass guru, will use these ribs to make a plug for a fibreglass mould.



The full story is here http://www.thebackshed.com/windmill/FORUM1/forum_posts.asp?TID=547&PN=1.

I used the Warlock calculator to work out the blades chords and angles, though I needed to doctor the figures slightly. The longest rib is 300mm long, though the calculator was asking for ribs 500mm long close to the hub, not really practical.

The ribs took about 2 hours to CAD up, and a further 1 hour to cut out. They all have a 6mm hole to slide over a length of 6mm rod, hopefully this will make assembly a lot easier. If this works I'll make a smalled set for a 1.2 meter long blade to suit the F&P motors.

Glenn

[chadking]

Thos look excellent! Keep us informed on how the final project turns out.  It's amazing what a CNC machine will do.  

[willib]

hi gizmo

your going down the same path i took about a year ago, minus the cnc though.

then i found the Hot wire technique as was suggested by paradigmdesign

with the hot wire you can incorperate 'Twist' into your design,

using the foam as ribs and tring to incorperate twist can drive ya up the wall.

i'm not familar with PVC foam , what are its characteristics?

using a hot wire on PVC doesnt sound good though

my most recent blade diary

http://www.fieldlines.com/story/2006/11/22/63043/407

[paradigmdesign]

To be fair, I no longer recommend that method (after allot of trial and error + toxic fume inhalation).  I have went to (as per advice from my composites guru) using polyester tooling foam, close to the method shown just replace the words CNC with band saw.  There are difficulties involved in both processes, but working polyester has been a dream compared to the hot wire stuff.  I would recommend using a 8lb/cu. ft. foam or heavier, it will work better with sanding.

Good Stuff!

[paradigmdesign]

Just read the other forum post.  I thought thoes looked thin, using a 2410?  BTW it was a good idea to modify the tip and root chord from the warlock calcs.  Also, did you put the jig hole on the camber line or the chord line?  I guess with a 2140 there is virtually no diff between the two anyways.  I found putting a second hole to key in the twist is helpfull also(though it does add some time on the PC).  Keep us posted!