Sunday, October 24, 2010

Tips and joiners

Today I made some good progress.  After a nice brisk 34 mile ride on the bike (that make 120 miles this week), I started working on the wings again.  I wanted to get the tips and wing joiners done before I started sheeting, so that's what I worked on.

First, the tips.  The plans say to use bent bamboo.  As luck would have it, I'm fresh out of bamboo.  I could have laminated and steam bent some strip spruce, but I wanted more surface area to glue the wing sheeting to, and I want the tips to be a bit more sturdy.  So instead of the thin edge, I went with light weight sheet balsa 3/16" thick.  In order to get the plan image on the wood, I used the Acetone transfer method, and viola, a perfect reverse image.  Stack to pieces of wood together, take it to the bandsaw, and out pops two tips.  As you can see in the pic, I also cut slots for the spars.

Also, I created my joiner ribs by cutting out 1/16" ply ribs matching the rib #1 profile then gluing sheet 1/8" balsa to the backsides and sanding to shape.  I took those assemblies, marked out the slots for the spars and leading edge, and attached them to the wing pieces.

Then came the joiners.  I've decided to go with two 3/16" steel rods with brass receivers.  I could have gone with cf rods, but this is what I have on hand and I'm a big believer in keeping momentum going.  Will they be strong enough?  I think so unless I decide to do ground loops.

I put the brass receivers in the gull side of the wing, 2 bays deep.  Then I put the rods in the tips panels also two bays deep.  I probably could have gotten away with only one bay, but a little extra strength doesn't hurt the weight too much.  First, I measured my hole spacings and used my hand drill to make the holes.  The I dry assembled everything to make sure it all lined up.  When I was happy with the fit, I built joiner boxes around the rods using hard balsa and 1/64" ply caps and used 60 minute epoxy to hold it all together.  I kept the wings joined together with clamps to ensure that the rods and receivers stay lined up.  Since the receivers aren't attached yet, I can still tweak those a bit, but I like doing my wing joiners this way to ensure the best joint possible.

Tomorrow night, the other wing!


  1. Looks great - where does one find bamboo these days? Did you wind up looking for any?