RC-Captain

Hello everyone,

I am currently rebuilding a Modeltech extra 300 for the 6th time. Well the first with this fuselage and notice there is absolutely no way the carb can be above the tank no matter what I do. It was determined that the dead sticks I am experiencing are due to the carb being to low in reference to the tank.

The way the plans mention to mount the tank is at the 8 O'Clock position inverted of course. The only way I can alleviate this problem is to mount the engine at the 2 O'Clock position and bare with the mess it is going to make.

mirwin

My Feedback: (1)

Can"t you use a fuel regulator?

Mike

RC-Captain

Yes, but I am going to attempt to mount the engine right side up and go from there, I don't know what the manufactureres were thinking but it's been two different engines put in this plane that ended in the same result. The proof is in the pudding just making everyone else aware before buying one.

piper_chuck

My Feedback: (12)

I've had 2 different engines in mine and the only deadsticks I've had were my own fault or a couple recent ones that appear to have been caused by bad fuel. Suddenly 3 very reliable planes all developed the same problem. It went away when I used a new bottle of the same fuel.

I don't think there's a issue with the engine location in this plane. I'm curious how it was determined that the carb location is the cause of your deadsticks, I've got planes with carbs that are lower relative to the tank than this one and they still don't deadstick.

RC-Captain

It's determined because of allot of factors. I will give you some of them.

1 mounted in my trainer this engine never dead sticked , not even once.

2 same plane to different engines , fuel is brand new and a dead stick occurs.

3 cant cut bulk stock away from fuel tank compartment , because of design.

4 asked the engine forum what was going on and everyone agreed it was the tank height not the position of
the engine.

So I am convinced that the design of the plane is incomplete. If you look at the position of the fire wall it is higher than the carburetor when the engine is mounted at 8 O'clock position. The reason I got a flights in is because the plane isn't level when leaving the ground but a balanced plane in flight is level and this is when the stuttering and stalling of the engine begins.

exeter_acres

My Feedback: (2)

Hmmmm... you seem to have a history of posts regarding problems with engines....

me thinks there just may be a tuning issue out there....
the Extra has been flown successfully by many, many people......

RC-Captain

the only problem I have with any engine is with the MAGNUM .28 ! , the AP .15 and the other 4 OS engines I have, have ran fine from the beginning until now . So I don't know what history book you are reading regarding me and engines but here it is in plain English.

WHO ? or are you just talking rubbish ? come with a little more facts than this please. []

piper_chuck

My Feedback: (12)

Every time a thread comes up on it, people, such as me, chime in with positive comments about the plane.

RC-Captain

It seems you have no regards for tank positioning , which is fine, but how can you be convinced that all three of your planes problems wasn't from tank position vs bad fuel ? Of course a new bottle of fuel has more nitro potency so it may only seem that this solved the problem, but did it really ?


I read in RCU almost one hundred times a guy posting about an engine that would not run , and some one replying , lower the tank. I have NEVER seen you, Chuck, respond it has nothing to do with the tank position.

My point is simple , the tank position can't be lowered on this plane , thus far the positioning of the engine is a mistake.

piper_chuck

My Feedback: (12)

Different tank, lines, and engine position. Did you retune the high and low needles when you made this swap? Did you do a nose up test to confirm that the high speed wasn't lean?
Could be the plane, but it could also be the way you're tuning the engines.
Nope, and you've yet to prove that the design is the cause of your problems.
I just read the thread. You're not accurately representing what was said. One person suggested that tuning could be the issue, but you completely ignored that and latched onto tank height. The people were responding with generalities, and I doubt any of them actually have this plane. They were saying tank height COULD be the problem. There are other, and more likely, explanations, such as the engines not being tuned right.
Stuttering and stalling are indicative of an engine that's not tuned right. You had trouble with a Magnum .28, and now you're having trouble with an OS .46 FX (which by the way is WAY TOO MUCH ENGINE FOR THIS PLANE), and you're now condemning the designers?

RC-Captain

come on Chuck, if I am guilty of overpowering a plane so are you and tons of other people in RCU thats not the problem I am having . You are so convinced that it isn't tank position , but didn't you mount your tank at the 12 O'clock position ? If yes why ?

Other than that just because you don't dead stick with this set up, doesn't mean your motor to tank position is perfect.

piper_chuck

My Feedback: (12)

I have regards for fuel tank position, and I've also observed that most engines are not as sensitive to tank position as some people seem to think. How can I be convinced tank position wasn't the cause for the sudden problem that developed? It's simple, all three of these engines have run flawlessly in these planes for over a year. Suddenly they start acting up, one right after the other. The tank did not suddenly change positions. I tried new glow plugs, didn't help. Checked the fuel lines, all were fine. Only after I got out a new bottle of fuel did the problem go away, ON ALL 3!
There are many reasons why an engine won't run right. Could be tuning, bad fuel, plumbing problems, bad or wrong glow plug, and a host of other problems. When you're faced with one person who is having a problem with a plane that's got lots of positive feedback, it's best to look at the way the plane is being operated before blaming the design. By the way, what plugs are you running?
You have not proven this point. There are plenty of us out here, who are not having the problems you describe. In fact, I think you're the ONLY person I've heard of who has this problem with this plane.

piper_chuck

My Feedback: (12)

The plane is rated for .25-.36. Mine has a .32 in it. Please help me understand in what way I'm overpowering mine? And, the fact that you're trying to cram a significantly larger engine in it is relevant if you think the tank is too high. The carb on the .46 is going to be even further from the centerline of the shaft, exacerbating the problem you think you have.
I don't understand your question. I mounted my tank per the instructions.
I'm not saying the tank position is perfect. I'm suggesting that given that many people have had great results with this plane, there's a good likelyhood that your problem is not due to bad design.

You have the opinion that the design is bad. That's fine, it's your opinion. I'm providing an alternate opinion, and the results to back it up, that the design works just fine. If the design was as bad as you are implying, I would have expected to see lots of people complaining about it. Quite the contrary, it gets lots of positive comments.

piper_chuck

My Feedback: (12)

I just took a peek at the user reviews of this plane. No mention of deadstick problems and all 10 people who posted (a pretty respectable number considering smaller planes are allegedly not as popular as the bigger ones) seemed pretty happy with it.

RC-Captain

OK OK OK , it's not the tank position , but as far as overpowering I had a MAG .28 in the plane and still received dead sticks . I put the MAG .28 mounted at 12 o'clock in a SPAD delta wing the engine wouldn't stop running . I didn't fly the delta but the transitioning and idling was fine when mounted up right. So what am I supposed to believe?, what I hear or what I see in front of me ?


You can defend the plane all you want, I LOVE THIS PLANE thats why I am still trying to get it to fly . I was told the plane was squirrelly , and didn't see any signs of this, I guess the guy who told me this didn't know anything about dual rates. To sum up this thread, I will mount the same OS .46 in the 2 O'clock position and post results.

PS .36 to .46 isn't very much and just to let you know , the plane handles better with a .46 vs a .28.

piper_chuck

My Feedback: (12)

Try mounting the .28 inverted on a test stand and see how it runs. You might find that it's troublesome even on the stand. If it's sputtering, see how it responds to adjusting the carb. I'm also still curious what you are using for a plug.

The difference between .36 and .45 is actually quite a bit. I've got several of both size. The .36 engines are upsized .25s. They are quite a bit smaller and usually several ounces lighter than the typical .45 engine. For example, the TT .36 Pro, a very popular .36 engine, weighs in at 11.4 ounces, while the OS .46 AX and TT .45 Pro are both over 17 ounces. Adding 6 extra ounces to a plane this size is a significant difference, especially when you consider the extra lead it would need in the tail for balance, and the very thin airfoil. The overall effect on the flying characteristics is not going to be positive on anything other than the vertical.

It's also hard to imagine that you will even be able to use the extra power without tearing the thing apart. Mine's a rocket with a Webra .32, and I've got it pitched down to reduce the speed. Much more power and the plane would be subjected to stresses that it probably can't handle.

Personally, this is one I wouldn't overpower. But, it's your plane and if you're happy with the .46, great!

piper_chuck

My Feedback: (12)

Oh, I forgot to mention, Merry Christmas, or happy holidays if you follow a different faith!

Newc

Why not simply mount a small tank at what RC-Fiend thinks is the right position (height-wise) but on the outswide of the fuselage temporarily and see if this makes any difference in flight? Not to worry about drag, etc. with a small tank mounted externally as this is done all the time with combat planes using engines of this size. Simply use strapping tape to hold the tank on.

After all, part of the fun of this hobby is to use innovatiion to solve problems.

RC-Captain

I don't have to do this, I will turn the engine 180* and mount it without the cowl and fly the plane to see if I was right. By this weekend I should have it ready to go.

On top of that I am mounting the MAG .28 on another plane in the up right position to see if it will fly the plane with out any problems in this position.

BillS

RC-FIEND

It does seem that some manufacturers don’t consider details like tank/carburetor relationship. Since the beginning of time the correct relationship (upright or inverted) between carb nozzle and tank has been the same, carb nozzle approximately 1/4” to 3/8” above the tank centerline. Violate the basic principles and most often one ends up constant engine fiddling. While some do get engines to run in adverse tank relationships most will not.

Wonder if the manufacturer has flown the airplane.

Bill

RC-Captain

I getting the feeling that RCU is truly a matter of oppinion. I can't remember reading one time in RCU where a person used the recommended size engine for a plane built from scratch or bought and assembled. So I go from a recommended .36 to a .46 and I am immediately facing possible problems.

Was it you Chuck that put a .40 engine on a .15 size SHRIKE ? or am I losing my mind ? [sm=spinnyeyes.gif]


and yea MERRY CHRISTMAS, any new planes ?

piper_chuck

My Feedback: (12)

You must have a short memory, because more than one of us have posted that we are using within spec engines for the plane in question, and many other planes. I'm pretty sure you were participating in the threads talking about this plane. I'm also pretty sure that you've also participated in threads where many of us commented that a .46 was a bad idea. There are a few people who routinely advocate overpowering, but you'll actually find many more people staying within the recommended range. The advocates of overpowering also tend to be way more vocal than the quiet majority who power their planes per the manufacturer's specs. The number of people who would consider using a .46 in a .30 size plane are few and far between. It's your plane, do what you want with it. Just don't start crying about poor construction when it starts shedding apendages in mid air, or you go below the (increased) stall speed and snap it into the ground while landing.

Apparently you ARE losing your mind . My Shrike does not have a .40 engine! In fact, my Shrike 10 doesn't even have the .25 that so many other's put in it. I've posted what's in it, go find it if you're interested.

Besides, there's a world of difference between the power that one chooses to put in a kit built plane that can be reinforced during building, and that's only designed for one thing, going fast, and what's put in an ARF that's designed for areobatics. Adding significantly more weight (and 6-8 ounces is significant on a 3.5 pound plane) to an aerobatic plane can mess up its flying characteristics. If all you want is a rocket, go for it. If you want a well behaved aerobatic plane, my opinion is that this plane with a .46 is not going to be it.

RC-Captain

OK I will look for the post and report back , but in the mean time, you shy away from stating the MT extra is rated for a .36 I am wondering why ?

LOL You really doubt my flying skills allot ....another reason for video.

piper_chuck

My Feedback: (12)

Where on earth do you come up with these things? I did nothing of the sort. Reread post #13 and post #16.

RC-Captain

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This makes since and thanks for the info Bill .