Scale Build Off - 1/4 scale (55") Pitts Challenger III

PsyBorg

Wake up! Time to fly!
Wow she does really look beautiful all done in that red. Love the two glasses all ready to toast her. Nice touch.

As far as experts to help you tune by picking things up in the video don't look to me. I just ask dumb newb questions to add wrinkles in my own head trying to do a cause and effect thing so I remember symptoms and what was the cause and possible solutions.

GL at FF and I cant wait to see more video.
 
Just watched your latest video.... So sorry! Great attitude though! The "better luck next time" comment floored me. I would have been feeling gut shot at that moment. But, it's part of the hobby! Good luck on the rebuild!
 

wilmracer

I build things that fly (sometimes)
Mentor
Just watched your latest video.... So sorry! Great attitude though! The "better luck next time" comment floored me. I would have been feeling gut shot at that moment. But, it's part of the hobby! Good luck on the rebuild!

Yeah... TBH it did hurt to see but I already knew at least a partial rebuild would HAVE to be in the works. The AUW on this final flight was a hair over 16lbs :black_eyed:. The wings came out far too heavy and after paint I had to add about 8oz to the nose to re-balance. I had joked with some folks before the flight that if she crashed I hoped at least the fuse would survive. Turns out it was the other way around :eek:

All the electronics survived, which is a plus. I'll do another one in the coming months, and it will be a much faster build as the fuse plug is already done. I'm betting I can do that one under 10lbs easy.

 

willsonman

Builder Extraordinare
Mentor
Carl and I discussed some extensive changes throughout. Simpler wings should shave at least 2 pounds, if not more. The H-stab was made with carbon, balsa sheeted, and then glassed. I suggested a simple hard bass TE and balsa leading edge for strength and just glass with epoxy for a finish and strength. This lighter tail would lend itself well to reducing nose ballast to offset. Its up to Carl, but there are many other things that can be done to put her on a diet. We also discussed using thinner ply for the internal bracing of the fuselage as well as carbon tow in the layup around the cockpit opening. I'm sure Carl can post a pic of that failure point but using tow in that area will greatly ensure the re-build will be a long-lasting model.

In the end, I think Carl was happy with how things turned out. He is always upbeat about his builds, and crashes for that matter. He takes lessons learned seriously and that is a big part of the fun with these scratch builds. Having spotted for him on two other VERY fast airplanes at FTFF, he is an excellent pilot and I have no doubt that he did the very best with this incident as well as the P-40.
 

saiga556

Full of...
V2 will be much better. Some crashes are good. It helps you make the jump and refine the design. I have found that the v2 is so much easier.

At least it looked really good. The balance of weight vs. scale detail is one of the hardest scratchbuilding skills to master. It pretty easy to make light be strong bit making it look good also adds a whole new dimension of difficulty.

Better luck next go.
 

wilmracer

I build things that fly (sometimes)
Mentor
Thanks all. Yeah, I try to have a positive outlook. A rebuild was going to be necessary to make her a good flyer, and if she hadn't gone in I might have just opted to throw a bigger motor and more cells at her to just muscle her through the air. It would have made her airworthy, but not the airplane I wanted her to be. With what I learned from this build the rebuild will go smoothly and she'll fly the way I want.
 
You have to have the good attitude! I had a 60 inch Seagull Extra 300 that went in on the third flight! I had picked it up used but unfinished. The previous owner had filled it with nice high end, high voltage, digital servos. What I failed to consider was the amp draw from those servos. I ran a 1600 mAh 5 cell NimH pack for the radio. It flew very well! After two flights I was going to pack up and leave but thought, no, I'll burn one more tank of fuel! I was coming in to get in the pattern for final and I lost all control and it went in hard! Ruined my Saito FA .90, obliterated the plane, and even ruined the aileron servos! It was a brown out.... But, they all have an expiry date, some just sooner than others!
 

PsyBorg

Wake up! Time to fly!
You were pretty sure weight was going to be an issue back when you were doing the wings and trying to decide how to do the ailerons. I make it a rule to never live with "I shudda coulda woulda" and try as best I can to go with that gut feeling. 9 outta 10 times its going to be right. I finally stopped listening to that voice in my ear on the other shoulder telling me to "Go for it"

Your case is surely different then mine as you are designing and building and proto-typing as you go. That skill set is a HUGE plus to have. No reason to feel bad about the out come on this one. It got off the ground. It flew. Most of all it confirmed what you already had an idea of going into the flight. The best part is other Flite test people got to see it and live the lesson with you. We all may feel bad about the out come but I know many here have a huge respect for what you do and look forward to the next phase
 

Guy123

Junior Member
Such a shame that it ended up in bits! :(

Really nice build log, thanks for keeping us posted and a great looking plane! I'd say even on the re-maiden it screamed tail heavy to me - obviously you want an aerobatic plane to be slightly tail heavy, but it looked like it was cruising at a 45 degree angle.

I can imagine this was frustrating too as with the weight considerations it wouldn't have been as easy as shoving some ballast in the nose to level it out - oh to be a builder! :)

You did a great job making it look pretty and I can't wait to see the re-build; I'm sure you'll make another beaut.

Best of luck

Guy
 

wilmracer

I build things that fly (sometimes)
Mentor
Have you had a long enough grieving period yet for the Challenger rebuild to happen?

I'd love to jump back into this one eventually, and I've held on to the plug, plans, hotwire templates, and other pieces for when I do. At the moment hobby time has been hard to come by and I've been focused on getting other projects completed. The big P-40 is ready to go again, I have an 8 year old F-14 project that I need to get airborne or out of the shop, I need to get the Talon flown again and finished, and I have a big build that I really need to tackle in the next year or so that will probably be the next on the build table. With all that the Challenger is probably a few years out :black_eyed:
 

thenated0g

Drinker of coffee, Maker of things
Mentor
I would suggest something other than a bungee. Once you heat the wire it will give and you will get warped ridges in the foam cuts. With that bow I would suggest another wire and a very strong spring. It will remove the slack when the wire heats but not give by dragging the hot wire. I use piano wire... like from an actual piano. Picked it up from a repair shop. Got about 10 feet of it for $1. THeey have it by the spool and usually are good about helping hobbyists. I'll get my calipers out tomorrow and measure it for you. I'm taking off work all next week so if you are free let me know.

Man, was not looking for this info, was researching the fiberglass fuselage, but i have been having very similar effects on my hot wire cutting and didnt know why. Going to try your spring method.
 

willsonman

Builder Extraordinare
Mentor
Man, was not looking for this info, was researching the fiberglass fuselage, but i have been having very similar effects on my hot wire cutting and didnt know why. Going to try your spring method.
Yeah, the tension needs to be kept on the wire during the cut otherwise the wire will sag and your cuts will require some elbow grease. Far easier to modify a bow with a spring with tension so that you can avoid it in the first place.
 

thenated0g

Drinker of coffee, Maker of things
Mentor
on my cnc hot wire cutter i went to a weight and pulley setup but i dont think im getting enough tension on it as i am getting this waviness like the wire isnt tight enough.
 

OliverW

Legendary member
Wish I was on the forums early enough to see this. Sean is a great family friend.. The new pitts will be a beast!