Note: Red colored changes are the most critical
Replaced Spar Fitting Bolts with Tapered Pins
- Chris Bobka and Dale Johnson were the advisers
- Avoids the wear-and-tear of assembly/disassembly using precision bolts
- Assembly is easier
- Required slightly larger hole
- Edge distances verified using Canadian guidelines
Outer Spar Fittings made from Bar stock rather than plate
- Bar material is 63,000 vs. 64,000 for the plate
- Performed strength calculations
- Note: Fittings are double shear. Thus, the outer fittings two fittings sharing the load.
Therefore, they only carry half the load (i.e.: ½ the load for each)
- Tested strength of material by destructive test of sample, see Strength Testing
Modified Shape of Nose Rib:
- Revised shape does not change the external shape of the airfoil
- Simplified the effort the cut out the part.
- Eliminate poor edge tolerance for 4 rivets
- Produces a slightly stiffer part.
Rear Vertical on Rib made wider on ribs at Spar Fitting Station:
- Solves rivet edge distance problem
- Eliminates the need for a gusset
Changed Order of Skin Installation:
- Plans call for the Bottom Skin to be installed first.
- I installed the Nose Skin first which enabled me to build a sturdy/accurate D-Cell.
Rounded end of 40 inch inner spar caps:
- Made slightly longer to avoid rivet hole, rounding avoids abrupt change in strength
Rib Stiffeners are slightly longer with angled end:
- Improves rivet edge distance
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Future Changes:Move wing approximately 2 inches to the rear:
- At my weight, several builders have advised to move the wing 2 inches to the rear.
- Impact on flight dynamics will be reviewed with Chris Bobka (longer nose, shorter tail)
- A tail heavy aircraft can be dangerous in a spin.
… counter consideration:
- With the center of mass more forward from the landing gear, landings may be harder (for a tail dragger)
- Building impact should be minimal: slots for spars be relocated, a few side angles need to be longer, radius of rear spar bulkhead needs to be reduced slightly, and joy-stick to aileron push-rods will have to be longer.
- Seat bottom may be impacted
... First choice was 27 hsp for longer range ... per Dale Johnson's recommendation.
- It is my guess that with any size engine, the max speed of 55 knots will be reached (assuming correct prop).
- I now intend to use a 32 hsp one-half Volkswagen
- 32 hsp is 4 pounds lighter than the 27 hsp engine (I assume from boring the cylinders).
Use formed ribs in center section:
- I chose built-up ribs for the weight savings ... and I save money. Also, they were fun to build.
- It turns out that not very much weight is saved (1 pound?)
- The formed ribs have very nice enlarged lightening holes which would make it easier to reach into the wing.
- Conversely ... Rib doublers block most of the holes ... aaagh!