Gordon Brown Posted December 11, 2015 Share Posted December 11, 2015 I'm in the process of building a CMPRO Mitsubishi Zero, the 71 inch wingspan job, and the manual doesn't give any advice on down and right thrust for the engine. Anyone got any ideas? I'm assuming as it's a low wing plane the down thrust would be small but as thus is the first large IC model I've built I'm not sure about right thrust. The engine will be an ASP 120fs. Quote Link to comment Share on other sites More sharing options...
Bucksboy Posted December 11, 2015 Share Posted December 11, 2015 I had a CMP Pro Zero a couple of years ago, I can't remember if it was this one but how many different sizes did they make? Anyway, the C of G as stated in the manual was wrong and too far back. The plane had one eventful flight and one only. Sorry, I can't help with information about the engine thrust but make several enquiries about the c of g on the web, I found loads of evidence after I'd crashed the plane. Quote Link to comment Share on other sites More sharing options...
Gordon Brown Posted December 11, 2015 Author Share Posted December 11, 2015 I was aware of the cog issue, as you say, lots of info available about that, I intend to start at about 25% MAC which should be a safe bet. However, Zeros tend to need lots of lead in the nose as the nose moment is so short. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted December 11, 2015 Share Posted December 11, 2015 I got the smaller one, and can't tell any side thrust. It does fly well and although feels heavy flies well and doesn't stall. I have a Saito 65 in it and thinking of putting retracts in, as I can feel wheel wells already fitted beneath the covering. Quote Link to comment Share on other sites More sharing options...
Daren Graham - Cambria Funfighters Posted December 11, 2015 Share Posted December 11, 2015 Only a general rule of thumb but 3 degrees is usually the magic number for both. Quote Link to comment Share on other sites More sharing options...
AVC Posted December 11, 2015 Share Posted December 11, 2015 Paraphrasing to a great designer "don't build any rigth thrust, learn to use the rudder instead" Quote Link to comment Share on other sites More sharing options...
Daren Graham - Cambria Funfighters Posted December 11, 2015 Share Posted December 11, 2015 Why make life any harder for yourself than it already is? Quote Link to comment Share on other sites More sharing options...
AVC Posted December 11, 2015 Share Posted December 11, 2015 For the same reason that we don't use 3 axis gyroscopes, autopilots, etc. From my point of view a hobby is not about making the life easier, but to enjoy with the challenge of controlling a model airplane in the air Quote Link to comment Share on other sites More sharing options...
Gordon Brown Posted December 11, 2015 Author Share Posted December 11, 2015 I'm with Daren on this one, getting the thrust settings correct doesn't seem any different to getting the cog correct. I suppose if I really want a challenge I could use the cog from the manual but common sense dictates that's building in too many potential problems. Having seen the difference proper trimming made to my Monolog in terms of how pleasant it was to fly I'm keen to make sure the Zero gets the same treatment. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted December 11, 2015 Share Posted December 11, 2015 I have no experience of full size and how they counter thrust issues, apart from knowing about rudder pedals and trim tabs, do they fly straight lines with a boot full of rudder in or trim it out ? however it's a simple process to trim a model aeroplane to counter it, I don't see holding rudder in verticals when doing stall turns as learning to use rudder (makes the ones to the right less crisp) it's a no brainer for me..trim it out on the mount. Learn to use your rudder landing/taking off in cross winds, co-ordernating rudder/aileron turns ,flying inverted, knife edging etc all more fun with a well trimmed model. John Quote Link to comment Share on other sites More sharing options...
AVC Posted December 11, 2015 Share Posted December 11, 2015 In the end is a personal option, and it all depends on what you want to do with your hobby. And as John says, trim it correctly and use the rudder in takes off, verticals, etc.But again, it's all down to preferences Quote Link to comment Share on other sites More sharing options...
Daren Graham - Cambria Funfighters Posted December 11, 2015 Share Posted December 11, 2015 Quite right, many full sized WW2 aircraft used measures to counter the effects of propellor induced forces on the aircraft, mainly because of the huge amounts of power in fighter engines. Offset fins and thrustlines. I have no knowledge of this relating to the Zero but some of the later marques were using massively powerful motors and I would be surprised if the designers didn't deal with the trim changes in some way. We no longer build models using a single sided razor blade because better tools are available for the job. (I guess you need to have started modelling many years ago to fully apreciate that comment). Quote Link to comment Share on other sites More sharing options...
Gordon Brown Posted December 11, 2015 Author Share Posted December 11, 2015 Oops, here's me with several boxes of single sided razor blades I still use (a local electronics shop was selling them off at a quid a box of 100 a couple of years ago), and two planes with 3 axis gyros fitted! Quote Link to comment Share on other sites More sharing options...
Daren Graham - Cambria Funfighters Posted December 11, 2015 Share Posted December 11, 2015 Gordon, I wondered what you were doing since you gave up the big job at number 10. Still making epic decisions then? Quote Link to comment Share on other sites More sharing options...
AVC Posted December 12, 2015 Share Posted December 12, 2015 Darren, you should have a look to my workshop: the most advanced piece of technology is a mini jigsaw I recently bought in Lidl Going back to the original question, I don't have experience with this particular model, but ages ago I had a Giles 202 of CMPro. In that one, the right and down thrust was already built in the firewall, and the engine was mounted with a specific offset to compensate it. Could it be that the Zero have a similar arrengmemt?Edited By AVC on 12/12/2015 05:37:58 Quote Link to comment Share on other sites More sharing options...
Daren Graham - Cambria Funfighters Posted December 12, 2015 Share Posted December 12, 2015 If it has you should be able to see it by eyeing the face of the firewall or use a small square..I recently had a prototype Extra300 to build and it too had built in thrust line. To get the prop in the right place meant that the engine mount was almost in the top right hand corner of the firwall. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 12, 2015 Share Posted December 12, 2015 I find warbirds need setting up similar to classic aerobatic models, around 1 degree downthrust and 1 or 2 degrees sidethrust. To check I stand the fuselage on it's engine bulhead and use a plumbline from the tip of the rudder for checking sidethrust, and from the elevator seat for sidethrust. Quote Link to comment Share on other sites More sharing options...
Gordon Brown Posted December 12, 2015 Author Share Posted December 12, 2015 There is no thrust built into the firewall, I've stood the fuselage on the firewall and checked with a large engineers square. The suggestion by Bob of 1 degree is what I'll try unless anyone else has better information. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted December 12, 2015 Share Posted December 12, 2015 Having no engine side thrust won't make much a difference, unless you are an extremely low speed and the model gyrates round the engine thrust or if you are under very high power levels, which would give a slightly left turn - hence why doing a left roll is quicker than doing a right roll, because of this reason. Ideally, an airframe should have no side thrust, as a dead stick glide, or very low power descent would cause trim changes. The model should have some design built-in to limit the amount of side thrust - such as pattern models, where a slight trim change would cause a noticable drift - unless the pilot corrects that, but the judges will see that and puts more load on the pilot - precision - not what you want by differing thrust/angle of attack values. Edited By Paul Marsh on 12/12/2015 13:35:08 Quote Link to comment Share on other sites More sharing options...
chris larkins Posted March 5, 2017 Share Posted March 5, 2017 Any update on this model? Have you flown it? I have one of these in a box and it may be next in line when the building board is free Quote Link to comment Share on other sites More sharing options...
Gordon Brown Posted March 5, 2017 Author Share Posted March 5, 2017 Haven't progressed very far with mine I'm afraid, other committments, other models all took precedence and I haven't flown as much since my lad left to join the army as he was one of the main drivers of the hobby. I have fitted split flaps and diddled about with mounting the tank etc, hit a minor issue with the ASP 120fs exhaust as the angle it's at means that I'd have to hack a huge hole in the cowl to allow it to exit. I've put together a design for a better exhaust manifold that I will knock up on the lathe when I get time. I've just finished building my Rojair ME163 so there's space to get on with the Zero, or the FW190 that needs repair, or the half built Stuka, or the Polecat kit, or the half built Swordfish I couldn't resist buying, or that rather nice big Citabria... Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.