Jon H

On the climbing/diving thing i do not agree that it is related to c/g, at least within the realms i am on about. Its virtually impossible to get a scale model to be in trim through its entire speed range and certainly the full size is trimmed regularly. Even your basic cessna is constantly in need of trimming so if a model climbs with speed and falls with less speed i would consider this normal. My sea fury is the most neutral of my warbird fleet and its also the one with the thinnest and most symmetrical wing. My La7 and P39 really need a good shove of forward elevator at high speed. In the case of the P39 i have watched a number of those old WWII training videos for the full size and from many of the shots i can see my model behaving very much like the full size. In practice its not an issue and i just hold the nose down with some forward stick on fast passes. However, if a model climbs with power, that is another story and engine thrust lines should be investigated. Again i keep things simple these days with 0-0 on my up/side thrust and just fly the thing. I have not come across a warbird yet were this has been any kind of problem. The only tricky part is working out if the model is climbing with speed or power, but usually this can be tested by just opening and closing the throttle before the speed has a chance to change much. When it comes to rates, i have high/low set for ailerons and elevator on different switches. Generally i use high elevator low aileron for takeoff, and go to low elevator when in the air with the gear up. Landing is normally the same but i may use high aileron rate if the wind is choppy and i want more authority. Lowering flaps also enables my elevator flap mix to effectively trim the model for the landing configuration as the slow speed and drag of te gear usually makes the model want to bury its nose in the earth.

From your description it sounds like there should be more than enough compression to me. I was once distracted by a phone call and forgot to put piston rings in a laser i assembled. On test It started and ran, even tuned up, but idle and acceleration was very poor and compression very low so i took it apart to find out why. Imagine my surprise to find no rings! While i appreciate that glow and diesel are not the same, the basic point is these engines should operate to some degree even when the fit is less than stellar. Also, if you can get the thing running the heat cycles should grow the piston slightly and you may find it all comes good. The trick is getting the thing going in the first place. I echo the feeling of others who are cautious about an electric starter, but used correctly it might be the way to go as the dynamic compression will be higher than when hand flipped. If you use an electric starter do not prime the engine at all and just let it draw its own fuel. I am sure there will be a way to get it going.

There has been plenty of comment on the compression, the piston nip etc but its very hard to quantify. Are you able to post a video showing the engine being flipped over with a prop on? Might be able to judge better what it happening. Unless the fit is truly awful, which i doubt, a heavy port prime and gradual increase of compression while flicking should at least get a pop out of it even if it wont run right away. I find it strange that it is completely devoid of life.

Yea, and the 20% castor recommendation was binned in favour of 15% synth by the mid 90's, then halved to 7% a few years back. While i dont think 7% synth is a good idea in this case, 15 will be absolutely no problem.

a gusting wind can wipe out any model under the right (or wrong?) circumstances. My little hurricane got faceplanted into the runway once with a sharp downdraft despite full corrective action. But as you say, these traditional models can usually absorb the abuse and bent undercarriage was the worst of it. One other thing to consider though is the model is now a half pound lighter and will fly that bit slower. If your flare was at the normal speed you are used to you may have had just enough excess energy for the wind to really pick it up before dropping it back down. That said, it would probably have been a non event had the engine not decided to give up at that exact moment. In any case, retracts are always more prone to damage and I tend to hangar my warbirds in gusting conditions for that reason. Last weekend i took my sea fury to put some hours on the rebuilt engine. The first 3 flights were perfect with nice smooth landings. The 4th took me 3 approaches with 2 go arounds as i couldnt get it stable as the wind had swung to the north a little and the turbulence off some trees caused real problems. WIth the wind in that direction, 4 flights already and an undamaged model i decided to call it a day.

I have OS engines of the same vintage running 15% synthetic and 5 nitro with no issues and i cant see any reason why there ever would be. 25% oil will make an utterly horrendous mess and there is just no need for it.

ill add my 2p as well. I can see that if you had 2 identical models, but one was a brick, it might be less stable than its lighter mate when flown at the same speed as it would need a greater aoa, but generally weight is not a factor as long as the model is within the range of weights appropriate for its size. On reynolds and all that...ehhh its pretty much meaningless unless we are building exact scale replicas with identical wing sections etc. As we dont tend to do that, just forget it and move on. As a side note, most model warbirds tend to have over size tails to 'improve stability'. I have a big problem with this as making the tail bigger also makes the elevator bigger, and thus more effective. This makes an already sensitive model more sensitive leading to excess nose weight to tame the beast. I believe this larger tail idea is a hangover from the free flight days when the bigger tail would have probably been an asset. However, now we have our dumb thumbs on the controls the static stability of the aircraft is less important as we are able to correct deviations we do not like. With this in mind i built my little hurricane with a scale (or more scale) tail on it and i have no stability problems with it, and my elevator movements are still very small. So take that modelling folk lore. I advocate scale tails and rearward c/g in the pursuit of model warbird bliss. Oh and i cant be bothered with side or down thrust either. Mount it straight and use the tall waggly thing on the back.

15x8 would get my vote in that model. use apc, master are rubbish.

yep it will be fine Tank in the right place, OS f plug, correct prop for model (what is it?) With that sorted, start it, tune it, fly it. Repeat until tired, go home, crack open a beer (or beverage of your choice) and reflect on your day of flying. Hopefully the engine is in decent mechanical condition. I would recommend you whip the front housing off the engine and take peek inside before you run it. If its rusty or otherwise not nice change the bearings etc and then go from there.

Ah look see, i try and help one chap id his engine and im back doing a job i no longer have for a company that no longer exists at half 7 on a Monday night. I dont mind helping out here and there but going through the entire range from start to finish would be like writing war and peace. Just the 150 alone has about 6 major versions to cover although many of the versions hardly differ visually. I have given details for the 100 and 120, the 150 is the same as the 120 just 100mm tall not 90. That's going to have to do for now.

Martin yours is a 100, Brian's a 120 circa...ehh 96? sure why not. 120 has 45mm case, 90mm tall, bulges for head bolts on crankcase above mount rails, large head, large exhaust etc...and, it just looks like a 120 as that is what 120's look like.

Well it looks like a 100...they look like that. if it looks like that its a 100 as that is what they look like. This is also a 100. 100's look like this https://www.laserengines.com/product/laser-100/ You will note it looks the same as the old one, just not as square. What else...well 45mm case, 100mm tall...square case with no bulges above the mount rails for head bolts....small head, small carb, small exhaust....and it just looks like a 100.

it couldnt have been done for the same price as a common throw crank. A full boxer would have cost a fortune and at maybe twice the cost of a v it wouldnt have sold. Also as vibration with a single throw was not a problem on test, and no owner has ever complained its a moot point anyway. This was discussed to death during the development. I have seen posts on facebook from people who have not owned one or seen one run claiming excessive vibration, but they simply havent a clue what they are talking about. They run fine, not as smooth as a V but not as 'bad' as a single, and power that thrashes the competition. Although unrelated, i like the 180 degree firing interval too. Makes a nice sound.

Dont look at me. i stamped the size on mine and in 1993 i was only 8 so not my problem.

Its a 100. 1993 manufacture. There is an outside chance its a very late 90, but i doubt it. Weights are meaningless as carbs changed, early engines had solid cranks, later ones hollow etc.

The pot calling the kettle black. I was more than happy to assist and was quite happily posting away until you kicked off with your snarky 'throttle moves both ways' comment. So perhaps you should consider the way you speak you people if you do not want the same in return. If it was in jest and i misunderstood then fair enough, but i do not have much tolerance for snarky nonsense. Especially when the engine you have has a pretty dreadful throttle. Ok fair enough, but from my point of view once you have flown a handful of 60 ish inch warbirds you have flown them all. The basics are the same for all of them and the lessons from one easily apply to another. For example the H9 109f is a bit of a porker. It always has been and i do not know why it should end up so heavy and its not really a great yard stick to measure by. Seen in isolation it might look ok and fly alright, but compared to a broader range of similar models it is more of an outlier. Regarding Galaxy, they were at their peak in the days before the internet and their kits faded from the lime light by the time it came along so information will the sparse. I used to fly a galaxy mustang and it was a good model which flew well on a 150 4 stroke. They are old designs and their age shows in many respects but they do generally fly well once all is said and done.

ok clearly you did understand my post at all. You cant say a model is tail heavy just because it needs lead to balance it. You can say its tail heavy without ballast, but its not tail heavy per se. No, it dosent. This is a starting point to guarantee the model is controllable and to cover off inaccurate balancing. It is not set in stone and you can move it and i would imagine that even 110mm would be fine. Not that you need to measure it, just keep removing weight and making adjustments. As a said before, i took over 1lb out of my large hurricane and about half a pound out of my smaller Hurricane. Both fly better for it despite being 'tail heavy' if measured according to the plans. This is a half truth at best. There is a perception that cg is a fixed entity perfectly measured at 95mm in your case and that is where it has to be. This is flat out false as any ic model looses several oz of nose weight over a flight as you burn the fuel off. Generally, this has no appreciable effect on the model and its performance. With this fact in mind we can say there is a cg range where the model is controllable, becoming less so at each end of the range. My suggestion is to have the cg as far aft as stability will allow as you end up with a model which is lighter, handles better on the ground and wont sniff the dirt on taxi.

Which rcv have you got for it? I have been playing with a 120sp and found some interesting things. If you have the same engine let me know and i can give you the info

why does it matter if i ever built one? I have a similar model from another manufacturer and countless other warbirds of varying sizes up to 90 inch. The tldr is that the model you have is a 60 inch and intended for 60 2strokes and 90 4 strokes, and a flying weight of about 9.5lbs. As yours is heavier than that you need to be prepared for it to not be as forgiving as you might hope. That was the point i was trying to make. With that said, i decided to check the spec to see if my memory was not as accurate as i would like. Turns out the model is 66 inch and not 60 as i originally thought, and with that in mind the weight is not quite as much of a concern. Its still very over powered, but at least the prop has a fairly fine pitch. Just keep an eye on the rpm as the limiting speed for master 3 blades is a little low. Not entirely, but after 18 years in the model industry i have had enough of smart alec comments and will be far less diplomatic when responding now i am just a modeller again.

quantify 'tail heavy'. If you are referencing the fact that it needs lead to balance at the marks in the instructions this is not a tail heavy condition and more than likely the model is nose heavy. Many kits come with extremely conservative c/g recommendations and they can usually be shoved back a good long way before the model becomes unstable. The advantages are obvious with less weight carried and a model which will not spend all day sniffing the dirt. The only thing you need to do to keep the model on an even keel is reduce your elevator travel as you move the c/g back. I have mentioned many times that i balanced my DB Hurricane on the plan c/g and have since removed more than 1lb of lead from the nose. My Sea fury too lost a big chunk after test flights, as have countless other sport and scale models i have in the hangar. Ultimately, the recommended c/g is a starter for 10 just to get your safely through the maiden flight. After that it will need to be adjusted, often quite significantly.

Or you could accept that its a sub optimal result and take appropriate precautions. There is even the option to remove some stuff from the model to reduce its weight.

IF the gear need that level of rake the model is balanced far too nose heavy. P51's tend to handle well on the ground and have decent size wheels. It should not be necessary to crank them that far forward.

Ah my 2nd favourite most stupid defence of excessive engine size. In any case, irrespective of the familiarity of the pilot with the throttle stick the model is over weight and over powered. This is rarely a good combination.

yikes.

My warbirds Hurricane is 63 inch and about 9.5lbs. Very fast with a laser 80 fitted. Ground handling is no problem though, and its not for my bigger DB Hurricane either. As i have mentioned before, warbirds have a rep for being unstable so they are balanced nose heavy to guard against such behaviour. The irony is that the excessive nose weight demands large elevator throw to keep the nose out of the dirt when taxiing. This high rate is the actual cause of their instability in the first place and adding the nose weight just made it worse as you now need even more elevator travel. I will always advocate a more rearward c/g and smaller rates on elevator. I also for scale size wheels and, ideally, scale length legs as well to help with ground handling. Some warbird kits come with tiny little wheels and a single snail turd is enough to trip them up.