RE: hangar 9 corsair needed fixes before 1st fight
The factory did address the issues of the weak firewall attachment and the weak area at the wing's gull bend. I had one of the early kits that lacked the reinforcements and, after reading of the firewalls pulling out after the first engine start on some of the early kits, I seriously beefed up my firewall. The airplane was a delight in the air but it only lasted 30 flights. The right wing outer panel blew off in flight and the model came down vertically into a corn field. All I could do was pull the throttle all the way back but it still hit hard. Interestingly, my beefed up firewall survived but the metal engine mounts broke! Also interestingly, the wing did not break at the gull bend so I must have reinforced the wing too by that time. (It was 4 + yrs ago and my memory is a bit hazy on the sequence of events.)
The two outer panels of the wing attach to a short center section with very short 1/4" ply joiners. These joiners work like a tongue-in-box both in the outer panels and the center section. Unfortunately the "box" parts are only made of balsa - the tops and bottoms are 1/4" square balsa and the "walls" are about 1/8". When the wing was under positive "G" from a loop, the outer panel was being pushed upward pivoting about the point of attachment to the center section. The part of the joiner that was in the center section box pushed its way downward thru the 1/4" balsa and 1/16" balsa skin. This 1/4" balsa was very soft and not suitable for what was in effect, a main spar. Those ply joiner pieces did not go all the way to the center of the center section either. There was empty space about 4" long between the two joiners inside that box. If the joiner had been a single piece of 1/4" (maybe even hard balsa instead of ply) that extended out both sides into the outer panels, it surely would not have broken either.
I took some close-up pics with my macro zoom lens on my 35 mm Pentax, drew a diagram and wrote a polite letter explaining how the failure occurred (my own little "NTSB" investigation) and my conclusion that the failure was the result of inadequate structural design. I requested a left wing, center section and fuselage so I could rebuild the airplane. Hangar 9 sent me an entire complete kit, free! I sent them a profuse thank-you note. To their credit, Hangar 9 is truly a stand-up company.
The new kit was updated from the first production run and had 4 hardwood blocks reinforcing the firewall/fuselage joint and a spar reinforcement at the wing's gull bend. The firewall reinforcement looked rather minimal to me, so I repeated the beefing up job I'd done on the first one but the spar reinforcement was almost identical to the one I had done myself on the first one. I was pleased with that, but I still made my own one-piece ply joiner for the center section.
I did something else, too. I'd used a Magnum .91 4-stroke engine and on the first model I mounted it the way they had provided for, with the cylinder pointing downward, not vertically, but at the "7 o'clock" position as viewed from the front. This had the effect of lowering the carburetor to a position very low relative to the fuel tank and it was not possible to lower the tank because the wing center was in the way. I'd had several flame-outs and deadsticks on the first model because of the difficulty of getting reliable top-end and idle needle valve settings with the effective high-tank position. So I mounted the engine in the new one with the cylinder horizontal ("9 o'clock" position) effectively raising the carb higher. The engine ran very much better this way. I have not seen a Saito 100 (H9's recommended engine) up close and maybe that engine runs better in the "7 o'clock" position than mine does but I recommend you carefully check how your tank position is relative to your engine's carb before you finalize the engine installation.
One other thing I discovered later - the Top Flight canopy for the Gold Edition Corsair is a very nice replacement for the H9 canopy, It has a better scale shape and the H9 plastic is rather more brittle. The TF one is not painted but the H9 is painted in the inside. I had put my switches and battery charge cables and the Voltwatch under the canopy and made it removable on mine. (I used two batts and two switches for redundancy). I'd have preferred to glue some small metal washers around the holes in the plastic for reinforcing where my little pins held the canopy on but the paint would need to be scraped away to allow the glue to stick the washers to the plastic. With the TF canopy, I could put my own paint on the outside and avoid that.
Another tip: Why do a test flight on a new airplane with the canopy and cowl on? Chances are, you will have to adjust the engine settings anyway and getting at the engine with the cowl on is a pain. You have to remove the prop (and spinner if the airplane has one) to remove the cowl. Get the engine set and the airplane trimmed and get it landing reliably before risking $50 worth of scale accessories. After it is flying and landing reliably, THEN put the scale stuff on and enjoy how pretty it looks. On my second F4U, I made my own wooden cowl with a hatch that can be opened without taking off the prop. Not only did that improve the operational convenience at the field, I was able to make it a lot stronger and more resistant to damage from the airplane going on its chin on landings.
Which brings up another point - most of the tail-dragger WWII fighters in model form often tend to go on their nose on landing, especially if you fly off grass. Most model kits have the main gears too far back. Worse, a lot of retracts only swing 90 degrees and point straight down when extended. I got the Sierra Precision retracts with the 100 degree swing to GET THOSE MAINS farther FORWARD. Robart also makes "back and twist" retracts with a choice of swing angles. Look at pics of the full size airplanes - the gear legs extend from the wing at a point very close to the leading edge. The Sierra units can't really be mounted as far forward as I'd like because the leg extends from the chassis at a point a good inch to the rear of the forward-most point of the gear's frame. Also, the leading edge of our models' wings is a pretty thick piece of wood that, itself, forces the gear to be mounted farther to the rear than would be ideal but I'd be reluctant to try to remove any material from what is already a weak point in the wing.
I also mounted my air tank and plumbing, valve and retract servo on the wing instead of the fuselage to avoid those darn quick-disconnects that torture my arthritic fingers. My structural reinforcements and air retracts made for a nearly 10 lb model, a little heavier than the first one. The first one flew light and was very nice in the air (when the engine was running and the wing was staying on!) The second one did not have as light a feel to it, but it still flew very realistically and was very pleasant to fly. It sure landed a lot better than the first one.
The designers initially made some poor choices in the structure but they have addressed this and updated the model. And they did do a nice job of making a good looking Corsair. WWII fighters can be really thrilling to fly (at least when you can avoid crashing or damaging your model on landing noseovers!) and the H9 Corsair is a BEAUTIFUL sight in the air.
I hope some of my experience is helpful to you so best of luck with yours!