Pilot side Top wing skins

After Lunch we stated cutting the wing skins for the top of the wing.  We found that the foam would not bend around the entire contour of the leading edge ribs.  We cut slots every inch, half the thickness of the foam.  That helped , but it still required some work to bend it around the contour.  Course Drywall screews helped to keep the foam down while the glue was drying.

We ran out of time today to glue in the center sheet of foam, but it will probably get completed one night next week.

Foam Ribs on Pilot Side and Conduit

This morning we cut the wing ribs with our segmented hotwire.  It worked great.  We had a little manual shaping to do with a sanding bar, but it all worked out very well. 

You may notice the white tube in the leading edge foam.  This is a conduit for stobe and Nav light wiring if we decide to add it later.  It is PVC pipe, but it is very light and has an extreemly thin sidewall.  The total weight of a 4 ft section is only 2.6 oz!  The total weight added to the plane is less than 10.4 oz!

The root rib is at -1 degree, and the tip is -1.56 degrees.  The extra few degrees at the tip causes the tips to stall last. That should make the plane not want to drop a wing when it stalls.

Wing Spar Extentions and Ribs

Between 10/7/2010 and 10/24/2010 we added the following Foam wing spar extentions. 

They are standard foam with KR Glass on both sides overlapping the spar by a few inches. We then trimmed out the edges and filled them with Flox. I was amazed at how stong they are!


You may notice the problem with image. The filler we used was Micro, Not Flox! We were able to easily peel out the Micro and redo with Flox.


 
 
 
 
Durring the weekend of 10/24/2010 we glued foam between the spars and on the front and the back for the wing ribs.  We also finished our templates for each end.  We are going to hotwire all the ribs in one pass of the segmented hotwire we built a few weeks back.
 

 
 
 
 

Hotwire issues

I was trying to devise the best way to cut the foam wing ribs for the KR.  There are 5 ribs in the outer wing.  The wing both tapers to a shorter chord at the tip, and changes airfoils completly!  I attempted to plot out the airfoil at each of the 5 locations but had less than perfect results.

After much time was spent working with a spreadsheet and CAD, I decided to see if I could do a hybrid of methods to acheive the wing ribs. 

On the origional KR, The foam was glued in place and a large strait edge sander was used over 2 templates to shape the foam.  This has a few downfalls:

1) Sanding is messy
2) The foam you would have to use is OPEN cell foam.  It requires a coat of micro to seal the cells
3) The foam is not available to me localy so I would have to drive 5 hours, or have some very large pieces of it shipped.

I decided on trying to use the standard Polystyreen foam and a long hotwire.  Unfortunatly, the hot wire would have to be so long that I was sure I did not have a way to power it.  I wondered if I could Segment the wire by making the electricity "Jump" across parts of the hotwire by adding a larger wire in some segments giving the electricty a path with a lot less resistance.

Here is our attempt using our long bow and a 14 gauge wire with aligator clips:



As you can see, It worked..  So, it was time to make a looong bow that could span all 5 wing ribs on the outer spars which as 90" long.

Here is the final product:



Now I just have to hurry and finish the foam spar extensions before it gets to cold to fiberglass!  I hope to have wing ribs in place and shaped by Halloween!