Aero120

I had exactly this problem with My Hangar nine mustang. The problem was not the plug, or the fuel but the bottom end mixture. I had to start mine with the engine the right way up and like yours it wouldn't idle at all with the plane the right way up.  I leaned the bottom end off by over a turn and now it will idle for over two minutes and pick straight up. My engine is an OS 91FX and initially ran fine but as it ran in the needle settings seemed to go their own ways. The top end went lean and the bottom went rich. However its sorted now. If your engine runs fine at full throttle then the plug isn't too cold, if the revs bog down at idle but pick up when you reconnect the glow, the plug is drowning. If there's plenty of oil coming out of the exhaust as it idles then its a too rich mixture drowning the plug rather than the plug coolling too much on its own.

Tim, Is a custom made exhaust? My custom mustang exhaust didn't fit initially so I returned it to Just Engines and they altered it. Only took a couple of days including postage.

Here's a video of Miss America flying. The "yodelling wasp" is not the sound of the Mustang! [IMG]http://i152.photobucket.com/albums/s164/aero120/th_MissAmericavid.jpg[/IMG][/URL][/p

Kelvin, I wouldn't say lots of problems, just a few things that need sorting. I've just got in from ground running the mustang and having leaned out the bottom end by about one and a half turns, it runs fine, will idle for over two minutes and picks straight up when the throttle is opened. Very little oil fowling of the plug now, so when connecting the glow at idle there is only a small increase in revs. So looks like an onboard glow isn't needed at the mo and neither is a hotter plug. The neat look of the plane without a standard exhaust has got to be worth a bit of fiddling!

Kelvin, My incowl exhaust in my mustang became a problem in the recent sudden hot weather and caused the engine to overheat. Several club members suggested that the air outlet wasn't large enough, stating that in should be four times the size of the inlet. So I enlarged the outlet at the rear of the cowl and it worked, the engine stays cool even when extended ground running. the larger outlet is hardly noticeable as the exhausts were there anyway.  On the real Warhawk there are a row of hinged flaps at the back of the radiator housing under the cowl, you could cut these out and hinge them to allow more air flow without ruining the scale appearance. 

This is a very obvious comment, especially in hind sight and thought I'd mention it here to hopefully allow anyone else following this route to a scalish plane to avoid disaster. Both Kelvin and myself have chosen to use non standard exhausts. My engine was brand new and I fitted the exhaust and mounted it all into my workmate to setup and do the initial running in. By the time it went into the plane it ran beautifully. However after the first few flights with a rich ish mixture, the engine bedded in further and chose to stop several times in mid air at low throttle settings. Fortunately I managed to dead stick it in without any damage apart from a few more grey hairs! I need to lean out the bottom end mixture and or fit  a hotter plug or even on-board glow. So as I've said, its very obvious now but could have wrecked the plane. I expected the mixture settings to be different from standard because of the different gas flow of the exhaust, but didn't expect the top and bottom end settings to separate from each other to such an extent as the engine ran in.

Simon thanks for that. DOH!

I totally agree, use what you want, but that's my point. Some people think that a WWII fighter should have  a quiet, gentle, torquey four stroke as its a war bird. However mine unlike the real planes is not a 60 yr old invaluable antique and so I want to fly it as they were intended to be flown. A late WWII fighter could "g" a pilot unconscious, catch up with a V1 in level flight  and hit the sound barrier in a dive,   Yes Eric I meant 1 bang per rev ie 16,000 bangs per min! Good point Simon, you are right, a real merlin would have only gone bang on each cylinder every four revs, but Richard, there's no passive stroke on a two stroke so its suck squeeze bang blow every revolution as bang, then induction and exhaust all overlap on the down stroke. So from Simon's comment my two stroke is over reving, bangs per minute wise but I still nearer the full size sound than a four stroke in my view. I do like the sound and torque of a four stroke, but I don't think its a match for the roar of a supercharged V12. But as many of you have said, fit what you want and enjoy.  I wonder if I'll be similarly critised for fitting a four stroke in my DH Chipmunk. But the Gypsie Major engine isn't really in the same same league as a Merlin or Griffon so I think a four stroke is ideal in that plane.

Hi Kelvin, My Miss America has flown very well on the Just Engines made exhaust, However I did open up the "mouth" under the spinner as far as possible to allow plenty of air to enter the cowl and a similarly a generous gap at the back of the cowl around the tail pipes to let the air out 

Okay thought I'd chuck this one into the mix. I've recently completed and flown a H9 Miss America Mustang and lost count of how many people were surprised I'd fitted a two stroke ( OS 91 FX) instead of a four stroke.  I also had many comments along the line of "well, it shouldn't go too fast as its a war bird" Are we losing the plot here? WWII war birds were the peak of piston engined planes and out performed the early jets. The V12 Merlins and Griffons were using superchargers and intercoolers and were way beyond the power output of any similar car engines at the time. These warbirds are now invaluable classics and so are nursed through modern air displays to conserve the engine and airframe, but I clearly remember the sight and sound of Rolls Royce's own Spitfire being hammered around the sky over Hucknall in the late seventies and early eighties.  That Griffon howled and screamed and was just as chilling as the Vulcan's howl. So in model terms where does a four stroke stand? In my opinion unless you are building a model of an under powered one cylinder plane, in the bin! A real Merlin makes 12 bangs per revolution. The red line for a WWII Merlin is 2,700 rpm. That equates to 32,400 bangs per minute. My two stroke 91 only does 16,000 rpm which at one bang per minute is 16,000 bangs per minute, half of what a merlin does. So a two stroke weighs less, has more power and is closer to scale than any four stroke. However for a Reno racer they over tune the engines and run at 3,600 rpm which means even a two stroke isn't making enough bangs per min!

Richard, Just Engines made a custom internal exhaust for my H9 Mustang. I had great service from them and its fits really well and doesn't seem to restrict the engine.

You've got to pretty accurate to land back on these things though...................

Kelvin, with the nicely painted pilot and replacement dash that cockpit looks very good. With the rubbish weather over the weekend I've got plenty done on the mustang. This is the switch I've bought to operate the undercarriage and radio circuits. With it are the 1/32 ply plates I've made to reinforce the fuselage and my circuit diagram, I will appologise for it as its twenty years since I last drew one and so the symbology may well be wrong but I just did it for my own reference. This is the completed harness with outputs for the relevant voltage meters and sharing the negative wires except for the servo wich is earthed via its plug into the receiver and I thought just a signal wire could be vulnerable on its own. The connections to the switch ahve been covered in hot melt glue to protect them from vibration. I fitted a paper tube over the wires to the tail servos to stop the wires thrashing around. Just a peice of A4 rolled into a tube PVA'd and then stuck in place with PVA. Here's the fuel and glow system. Flushed the fuel system before connecting to the engine. Its a bit of a spaghetti due to the postion of the pipes on the refuelling valve, it would have fitted better on the other side of the plane but that would have been impossible due to the engine mount offset and the throttle cable Two greens on the voltage gauges. Both circuits alive and tested Looking ready to go And finally, having landed safely after her first flight today. Control throws and C of G set up as per the instructions. I had some problems with the engine flooding when initially starting but soon set up with some help from another club member and a good test flight followed. Even though set rich, the engine produced plenty of power and the plane felt agile and light. Good response to control inputs and slowed very well for landing. Looked great in the air and easy to orientate against the late afternoon sun. Now I've confirmed  the Cof G I'll spent some more time sorting the wiring and tidying up the radio installation.

 I have "built" my Miss America in my Rc flight sim by modding the graphics, sound and data files of the default P51. Hopefully this should give me a rough idea of how it will look and handle in the air.

I have heard similar stories of tail plane failures on another artf I have, namely the Travelair. I can't help but think that this is caused by builders cutting into the wood when trimming the covering away from the centre of the tail plane. I like Kelvin's idea of using a soldering iron to avoid this. I use a new scalpel blade and just score the covering so I can peel it back and it tears along the score. My Travelair is a couple of years old now and the tailplane has withstood lots of abuse without failing. 

Thanks David. The scheme is not entirely accurate though. After its crash in 2002 the real plane (above)received a slightly different scheme as above, most noticabley the tailplane graphics now resembles the wings. Prior to its crash the sponsor logos varied regularly but at least that gave me some degree of freedom so I could put on my own designed logos.

Kelvin, do you think the cowl is too thin around the screw area? Mines deformed into the fuselage under the pressure from the screws so I'm thinking of either reinforcing the fuselage with some thin ply plates, cutting out the balsa and replacing with ply or drilled dowl end on or adding another layer of glass cloth to the inside rear of the cowl.

as homer says...

 I have fitted a remote glow and fuel connector to an alloy bracket that is screwed to the firewall. The needle valve has been repositioned using a 1/4inch piece of hardwood bearer to move it sideways but maintaining its vertical position relative to the carb. Its visible on the above photos.

Inside I have added 1/8 ply and balsa spars to carry the fuel tank batteries and reciever. The front set of spars also locate the fuel tank and are retained by screws into hardwood bearers so they can still be removed. I've also replaced the rigid throttle rod with a cable routed well to the side of the plane

Here's a reinforced main gear bay with a home made control rod with a ball joint replacing the standard Z bend

  As a personal preference I've replaced the tailwheel with an alloy hubbed version so I could retain it with washers soldered on each side of the wheel. I've also bent the rod sideways to engage in the control horn. This is more ugly than inseting it into the front of the rudder but isolates the rudder from any vertical movement of the tailwheel. The tailwheel can also be removed for maintenance. Also worth noting is that the tailwheel is completely wrong for a P51. If I have to do a rebuild I will consider moving it to the scale location and making it retractable

Here's the inverted OS91. The silencer was made by Just Engines to fit this model. It all fits inside the cowling but I've shorted the alloy tail pipes and fitted the silicon extensions incase of a belly landing.

Here's a late pic of the inside of the fuselage. Its very similar to the Warhawk. Here everthing is positioned to work out the Cg for the first time hence the mess.

I have decided that this model is for fun, howling around and looking great but with a good nod to scale items. Hence I have replaced the dash sticker with a "scale" decoupage dash with voltage gauges inplace of a dummy radio stack The pilot is an ideal candidate for MIss America!