More joiner madness

Not really much to report over the last few days.  I've had to do some traveling for work, but I did manage to get the joiner boxes all buttoned up and everything has aligned well.  I also discovered that with the longer joiner rods in the wings combined with a little bend introduced into the rod, will hold the wings together very tightly and will probably eliminate the need for any fastening system.

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!

Starting the wings

That pesky thing called work has gotten in my way the past few days, but I have managed to get some things done.  I made the main and secondary spars for the right wing half using 3/32" hard balsa then made sure every rib joint was tight as a drum with a complete dry fit assembly first.  Then came the Tightbond, some weights along the trailing edge to make sure it stayed straight and level, and voila, a new right wing half.  Obviously, I need to add a lot more wood to the picture, but you get the drift.

I also managed to cut 1/16" ply for the wing joiner ribs, but I will wait until I get to the point where I can do alignment of the wing halves before installing the joiner system and end ribs.

The gull is framed

I'll admit.  This is the part of the build that most intimidated me, and it feels really good to be through most of it.  I like to do the hardest things first, but I imagine the fuselage will throw some curves at me too.

below is a series of shots of how I assembled each gull half.  After flying the Playboy today with fellow clubmates at the sailplane field, I was anxious to get back and glue this thing up.

First, the crappy picture.  I should have gotten the tripod out, but you'll get the drift.  In order to make sure I had the main spar square to the subspar, and straight to the rest of the assembly before I screwed down the bases, I got out the laser beam and aligned everything with the main spar.

Then I added measurements to the drawing so I could make sure each individual rib was lined up correctly.  First, I drew a line under the gull on the plans from the root to 7" directly below the tip joint.  Then I measured straight down from the bottom edge of the spar to the line, and added 1/8".  This addition of 1/8" is to make up for the up-sweep from the bottom of the rib(spar) to the leading edge groove.  Then as I assembled the ribs, I measured each one so it matched the plans.  At the rear, I used the spar template to make sure the trailing edge tips stayed in alignment.  You can see the results below on the starboard gull assembly.

Then came the leading edges.  These stacked assemblies weren't holding their shape very well, and I needed them to be dead on because I didn't want to add any stress to the gull assembly as I was putting it together.  What I found was that my heat gun did a great job of allowing me to bend a little at a time and get the leading edges fit perfectly.

And finally, a mockup of the gull assembly!

The jig is up!

I also started building a jig to put together the Gull.  It will be built on the jig and I'll try to get everything nice and even, and so far the dry fit is coming out nice and straight.  The pieces are coming together like it was laser cut!  Once I get it positioned on the drywall, I'll screw it down and start gluing.

Leading edge

The plans call for a 1/8x3/8" leading edge, but of course it needs to follow that wicked gull curve.  So instead of one piece, I decided to laminate 3 pieces of 1/8" sq. bass stock.  First I used the spars to cut a pattern in two slabs of foam board and used spray adhesive to stick them together.  I fastened them down to my drywall building board.  Then I steamed all 3 pieces for a short while - just enough to get them flexible.  I glued the edges, and pinned them against the foam board.  These should make for a nice leading edge.

Spars take 2

I made some pretty good progress today.  I figured out my slot cutting for the ribs, created a jig for the assembly, and also started on the leading edges.

First, the rear spars.  I used the main spars as the template to draw the rears, but since the rears are also narrower, I had to reduce the width to 3/4".  I also had to transfer the slot marks, and you can see how I did that in the following pics:

From there, I took all 4 spars out into the garage and setup my 4.5" grinder with a carbide cutoff wheel.  Yes, the same wheel that helped me create a new exhaust for the Porsche can cut nice clean 1/16" slots too!  Here you can see the table jig I setup to feed the spar nice and straight.