Hey guys, here are some more pic's of my fuselage. I had an idea for the belly and turtledeck and it worked pretty good so give it a try. Rather than just eyeball the 1/64" offset I put masking tape along the edge. 4 or 5 layers should do the trick. This serves two purposes: first, it keeps any glue from getting on the sheeting in that area and second it holds the belly / turtle deck in the perfect spot when you pull the tape over it to hold it onto the fuse. I also did something cool with the firewall. First, I decided to try the "clocked motor" idea that Jason talked about a while ago (in order to avoid cutting a hole for header clearance with a side-exhaust motor). Jon Lowe did this and it worked great for his OS 160 so I did the same for mine. Karl makes a header that fits perfectly. Just tell him that you're using the same setup as Jon Lowe (motor is rotated 15 degrees clockwise from vertical when looking at it from the front). Here's how I did it:
1. Draw two perpendicular lines on the plywood re-enforcing disk. This gives you a reference point for top / bottom and both sides. I used a piece of graph paper to help find the end points of the lines.
2. Locate your motor mount holes on the disk using these marks.
3. Drill holes for your motor mount in the disk only.
4. Draw reference marks on the balsa firewall piece. For up / down I used the original horizontal line that intersects with the top of the top stringer since that's how the plans show it. In other words don't calculate an offset for the down thrust. If you look closely at your plans you'll see that that's how it's supposed to be. To accomodate the right thrust however you need to calculate an offset. That's .33405" to the left of dead center when viewed from the back side of the firewall. 11/32" is close enough unless you're really into splitting hairs. MAKE SURE YOU PAY ATTENTION TO WHICH SIDE WILL BE RIGHT AND LEFT!
5. Locate the disk on the balsa firewall over the reference lines that you just made. Line up the marks on the disk with your (offset) reference marks and cut around the disk.
6. Laminate the balsa and plywood firewall. I used slow epoxy and 75 lbs. of weight. Let it cure.
7. Now for the cool part. Glue the disk into the cutout in the balsa firewall but rotate it 15 degrees counterclockwise (since we're working on the back side) using a small protractor referenced to the lines on the disk and the firewall.
8. After the epoxy on the disk cures, drill holes through the firewall using the holes in the disk as a guide. Put your blind nuts in the disk.

Now clean up the stringer notches and sand a bit of an angle into the whole assembly so that the fuse sides make good contact. Use slow epoxy on the firewall and put it in place on the fuse. To help hold everything together I left the stringers about 3/4" ~ 1" longer than required and I put #64 rubber bands across them to hold the firewall in place. Some pins on the inside at each stringer keep the firewall from sliding into the fuse while the epoxy cures and some tape across the front keeps the seams tight.

John Pavlick