Bill,

O to be building again…your questions bring back fond memories! …but then again, I plan to fly tomorrow, and Judy is already packing for our trip to Sun&Fun at the end of the month! Now, back to your questions:

Retracting the gear definitely moves the CG aft. Lancair’s recommended CG envelope (normally measured with the gear down) was developed with this in mind…the airplane has to be controllable/have adequate elevator authority both with the gear retracted, and with it down.  I suspect they were pretty conservative in setting the limits from the very limited envelop testing I did on my airplane, but again, this is an area I really didn’t want to explore on my own. (I took Judy to heart when she told me that if I broke this airplane, I wasn’t getting another one.)

Hard(er) to measure the wt/bal with gear retracted  unless you’re willing to go to some trouble to put your jack stands (or similar) on scales. Can be done, but I always get nervous when the airplane is on jacks anyway… As to spin recovery, I’d definitely try extending the gear if it didn’t recover immediately…for two reasons. First, the CG moves forward, and reduces the polar moment of inertia…both should help. None of the airplanes I’ve seen extend both mains symmetrically—one is always ahead of the other. This generates a temporary yawing moment that just might get one wing out of the stall and get the nose down? (I wouldn’t suggest you go test this theory, but I’ve actually thought of giving this a try if ever needed…along with a thorough clean up of the seat afterward!)

I did not install stall strips “because it was not the manly thing to do.”  J  Actually, I had already finished and painted the wings before this was even discussed very much, and I was reluctant to do this afterward and re-paint the wings. If I had it to do over again, I would add stall strips, and I encourage you to do this. They cause absolutely no speed, weight or other penalty, and could be a life saver. I do have an AOA Pro system and have calibrated it for my airplane. This is something to consider also. My airplane stalls very well/straight ahead, but most roll prior to a full stall, some violently. I believe in exploring the approach to stall for these aircraft, and even a full stall, IF THE AIRPLANE BEHAVES WELL in the approach testing and WITH CAREFUL PLANNING AND AN EXPERIENCED LANCAIR IP/PILOT. This is definitely not something you want to do on the first few flights! There are some very good Lancair instructors around that will take you through stall testing if you’d like. Again, please, not by yourself…

I really think you’ll be very good with using either type honeycomb for the fuselage partitions, etc. Pete is correct on the armrest bids, and also around the door flanges, especially at the lower back of the door. The force trying to make a round balloon out of the fuselage is tremendous, and even small imperfections/thin flanges in these areas will allow the fuselage to bulge excessively, even causing the flight controls to bind in extreme cases. I actually used 4-bid on the right arm rest, but added some stiffeners and 6 –bids to the bottom of the door flange and the left side arm rest to reinforce this. The left side is more sensitive than the right because the door frame keeps this side from being a continuously “running” flange. Pay particular attention to the vertical AL reinforcements that stiffen the fuselage above the main spar box. Don’t short cut in these areas.

Hope this helps.

Bob

PS: In about 700 hours, almost all of it pressurized at 4+ PSI, I have no cracks, delaminations, etc that I can see. I did crack the door transparency, but this was almost certainly from allowing the door to “slam” open against the lift strut in a high wind. I wrote about this extensively on the LML last year about this time. The repair has held up marvelously. Message: Build it carefully according to the plans and you should be OK. These are well-engineered airplanes, and are holding up well in service.