March 19th - Finishing up the Passenger side wing walk

Today we added the wood that spans across the wooden ribs and cut 3/32" plywood and foam to fit the inboard top wing area.  We also went through and verified all the bolts were tight on the wing attach fittings and the landing gear.  We realized *After* we glued these in that we did not flox the gear leg to the bracket yet..  We'll work on that next week!  We also stopped at our new home improvement store, Menards, while we were out at lunch.  They have all our wing foam and at a cheaper price!  I'm sure the rest of the wing foam will be purchased there soon.

We need to complete the top skins so we can flip the plane and finish the bottom skins.

March 12th - Work started on the Wing Walks

Wing walks are provided to make an area to strong enough to walk on.  Many people think that an airplane must be really strong to fly!  That's not always true.  The wings are made of Foam and fiberglass.  They can withstand a total load of 3G's at 1200 LBS.  That's 3600 LBS of force spread evenly across the surface.  The key phrase is "Evenly across the surface".  The KR2S has 82 Square feet of surface area, so that means 1 square foot of the wing can only support 43 LBS.  A person's shoe applies all your weight in less than 1/2 a square foot.

In the picture, you can see 2 foam ribs and 2 wood ribs closest to the fuselage.

January 30th - Wing Skins

It was the first decent day to get back to work..  We did a bit of cleaning and continued working on the wing skins.  It was still cold, so progress was slow.

The Left and right Top Outer wing skins are complete.  We will need to start working on the wing walk area soon before we can close in the inner part of the wing.

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!