Why is it that some planes seem indestructible while others are not rebuildable after a bad landing? I've built more than 50 over the years and some have logged 1000's of flights while others didn't get past their maiden. These were all kits that I built, so it's not due to a flimsy airframe or too little glue (as I have seen in some of the current ARF's). My all-time most survivable plane was a small HOB P-51. Easy to transport and flew forever on a gallon of fuel. The original kit was $20 (I think Tower sells them for $40 now) and only needed a single roll of monocoat.
I built the House of Balsa .20 sized P-51 (kit K-40) around 1980. This was the first model I ever flew with close to a 1:1 power to weight ratio. I was able to learn to do rolling circles with it, knife edge flight and other aerobatics. It could also do a very tight “pylon turn” and pulled an incredible amount of G’s. They still make it and it hasn't changed in 30 years. I made a few mods to mine which may have increased the life span. It had a .25 FSR because our club was racing them. This plane literally had thousands of flights on it, survived for 30 years (voluntarily retired), and was crashed and rebuilt more times than I can count. The odd thing is the damage was never too severe. This is amazing since some of the crashes were such that I expected to be lucky if the engine and radio survived. Some glue and monocoat and it was always good to go. The planes crash resistance was probably due to luck and perhaps because it was a light well-built model. I retired it to use the body to make a fuselage test mold since I had never done that. Sadly, it did not survive the process.
I liked the model so much that I decided to scratch build a .60 size version. The wing and tail are sheeted foam and I glassed and painted the entire model. I added flaps just because I could. Unfortunately, all of that glass and paint on the tail forced me to add 1 1/2 pounds of lead to the nose resulting in a 10+ pound plane (ouch). The .25 size weighed 2 1/2 pounds. I was shooting for 7 pounds and would have come much closer with monocoat. I hoped it would at least get off the ground. I’ve since picked up some tips on sheeting foam and glassing that would trim off some of that, but it’s too late now.
The engine was new so I did some break-in on the stand and then decided to do some taxi tests while I got more time on the engine. I was doing faster and faster tests and a gust of wind gave it that little bit extra and the next thing I knew it was airborne. I should have chopped the throttle and let it settle, but it was near the end of the runway and I was afraid I'd run out of space. I did, but not until later.
I got it trimmed out and the too heavy (in my mind) .60 sized P-51 flew very nicely. Not as agile as the small one, but basically similar. I was making one last high speed flyby in preparation for landing when disaster struck - flameout. I was too low, too fast and heading down the runway into the wind. If I had been more familiar with the model I might have realized I could do a 360 degree turn and land (maybe). Even a reverse field landing would have been better. I thought it would slow down pretty quickly and since our runway is fairly long, the worst case I'd hit the dirt and high grass and scrub at the end of the runway. Wrong!
The plane kept going and going and I lost depth perception on it. It ended up hitting a large tree 10 feet off the ground. It impacted on the left wing just in front of the landing gear. Given the speed and mass of this model there is no way anything would be left. I was astounded to find it in two pieces (wing and fuse) without even a broken prop! There was a sizable dent in the LE and the left gear was damaged but that was all! The fuse was undamaged. It hit a tree at landing speed and then fell 10 feet straight down with less damage than I've had ground looping an airplane.
It seems for me at least, this particular model is charmed. I have rekitted more models than most modelers will ever fly. I've attached pics of the original (30 year old .25) along with the .60. I also included a picture of the mold and first fuse I made. Due to my inexperience, the fuse that survived 30 years of crashes didn't survive my mold making process. I have yet to complete a .25 size with glass fuse (due to other projects) but I hope to soon. This fuse should be invincible considering my luck with the balsa one - or not. Time will tell.
If you decide to build one of these, let me know and I can suggest some improvements. With the small servos, batteries and rx’s available today I bet it could be built well under 2 ½ pounds. I would also be interested to hear if my experience with this model is unique or if anyone else has had good luck with it.