Hello Michael, I ended up selling my CH750 project and no longer need the engine, it is still bolted to the shipping crate Viking sent it to me on.

Hey Michael,

Thanks! I do still have it. I had to put it on hold for a bit, but will jump back in here shortly. I should be posting more in the near future.

Hi Michael,

I do have a materials list for the CH640.  I had to develop the list myself from the plans, because it did not exist when I started in 2008.  Also, I developed my own part layout drawing for the same reason.

I'm happy to share what I have.  Please contact me directly at scott_stewart@keysight.com.

-Scott

Since I haven't seen the CH640 plans, it's tough to know what kind of brake you'll need. Based on my experience with the STOL CH750, I'd strongly advise against building a Dave brake. He built a 601 with it, and it probably worked okay for that. I broke my Dave brake twice trying to form the upper firewall stiffener, which is .063" and 893mm long. I used a metal piano hinge from Home depot, and the rivet failed the first time. I repaired it with solid rivets and the second failure occurred when the piano hinge metal just stretched away. Even if you use a quality stainless steel hinge from the aircraft materials suppliers, I don't believe it will hold. Other builders have had similar experiences. I built mine 8 feet long, and that wasn't long enough to do my tail section spars (each of the 3 tail spares was almost 9 feet long). I have access to a 10' industrial brake with a modified shoe, so that it bends at a 1/8" (3.2mm) radius. I repaired and modified my Dave brake several times before I could do most of the plane, but it's still not the right brake for the job. I can't bent the thicker fuselage channels and the wing trailing edge skins.

You'll definitely want to look through your entire set of plans and determine what the longest bends are in specific thicknesses.  Around 1000mm of .063 will give you a lot of trouble on a Dave brake. If your spars/spar caps (likely in .040) require long bends, you'll need access to a brake that can handle that. Dan Hill has an excellent video series on building a HomebuiltHELP brake (free plans on their site). I'm assuming the CH640 has a lot of similarly formed components as the CH750. If so, you will have a hard time building a single brake that can do everything. The HomebuiltHELP brake (especially as Dan built it), will do probably 99% of the plane, minus the longest bends. 

The Dave brake is easy to build, but if you're going to scratch-build an airplane, building the HomebuiltHELP brake is an excellent project to start with. When my project is done (I only have a few skins and my cabin interior structures to form), I'm scrapping my entire brake. If/when I start building the CH640, I'll build up a brake similar to the HomebuiltHELP brake, but I'll also have a hydraulic press brake. In another thread, one of the builders  said the longest bends in the CH640 are the spar caps in .040, and they're almost 11 feet long (3218mm)! I am almost certain you will not be able to bend those on a Dave brake. Further, the Dave brake has no adjustable set-back, so you can run into trouble with different thicknesses and bending acute angles with it. If you have access to other brakes regularly, then a Dave brake might work for you. I would check out Dan's brake build series before you commit to a brake, though.

Sorry that was so long, but it's a complicated issue, and I'm planning on doing a video that addresses all of this. I get a lot a brake questions, so a brake video would seem prudent.

Hi Michael,

When I bought the plans, Zenair included a CD with lots of pictures. They also include a very detailed rudder assembly manual which describes the rudder skin drilling.  Did you get this CD?

The idea is that you should lay out the hole pattern on the rudder skin and drill undersize (3/32") rivet holes in the skin. The rudder skeleton should only have centerlines drawn on the spar and rib flanges. You then lay the skin around the skeleton and line up the pieces so you can see the drawn centerlines through the rivet holes. Once everything is aligned, you match drill the rivet holes into the spar and rib flanges, and then drill all holes to full size.

You use this same technique throughout the build: layout and drill undersize holes in the skins, align to center of ribs/spar, final drill assembly.

I made matching right and left blocks for my wing ribs. Every place I needed a forming block, I made two in order to firmly secure the aluminum. For those pieces, like ribs, where I needed to make left and right, I put fluting notches into both blocks. In single pieces, like the firewall, I put fluting notches into just one.

-Scott

Hi Michael,

You will want to make as smooth of a curve through all the points as looks good.  This may require you to offset from the points giving by +/- 1 mm.  The smoothness of the curve is more important than the actual measurements.  The lift performance will not change if the measurements are +/- 2 mm, but the drag will increase if the curve is not smooth.

You will notice on the wing ribs and the curved bulkheads that you will need a little artistry to achieve a good curve, using the numbers provided as only a guide.

-- Scott Stewart

Hi Michael,

Do not use the "~305" dimension they call out on your drawings.  350 +/- 20 is what you want.  I used 350 and this is how it looks completed:

Notice the position of the lightening hole relative to the rivet holes on either side.  If you used 305mm, you would overlap the rivet holes.

-Scott