60 size engine in a 40 size plane?

[Pippen]

Hey all, I own a Great Planes Easy Sport ARF and it is powered by an O.S. .40 FX. It is very sluggish, and i have to take off from a rather bumpy grass field, and it needs more than 200 feet of runway to take off. I need advice on a more powerful engine for it. I want unlimited vertical performance, but i cant spend more than about $170. recommended engine size is .40 to .51 2 stroke, or .50 - .70 4 stroke. I am thinking of putting in an OS .60 2 stroke, would that be way too much power? I have checked the dimensions and weight, and it will certainly fit into the engine compartment. Any advice or feedback would be awsome. :confused:

[phuffstatler]

I don't think it would be as much a factor of power, as weight on the nose. A .61 would add several ounces to the front end, plus all the extra torque would be tough on the airframe.

An OS .46 or an Enya .50 would be a better choice. A Thunder Tiger .46 wouldn't be a bad choice if you're looking to save bucks.

What prop are you using (brand, size, etc)?
An OS .40 FX would be happiest with a 10x6, depending on brand and location (I'm in Texas).

Also, is your fuel fresh? Areyou using a low nitro fuel (like 5%). You can increase that up to 15% and get quite a bit more out of it.

Is your engine running lean? They will fall way off of power when lean. Is it way too hot to touch right after flying?

Finally, check the CG, and make sure it's good, too.

Hope some of this helps.

[Pippen]

I am running the engine slightly rich, and the engine isnt too hot to touch. I am definitly getting all the power I can out of it. I use a 10x6 APC sport prop.

Is a .46 really all that much of a power increase? it doesnt seem like it would be. I am also taking a look at an OS .50 SX, but i guess I am just Power hungry! I want as much power as i can, without compromising the plane's strength. would a 4 stroke be a better option? maybe a magnum 65?

I am using fresh 10% nitro fuel, tower hobbies brand.

I had to add over 8 ounces to the nose, so that is definitly not a problem. I am tail heavy to start with.

Thanks alot for the feedback:)

[Dave Robelen]

Hi Pippen,
Most of the "milder" .60's don't weigh anymore than the 4-stroke engines that your kit reccomends. Going up from the .40FX would pretty much require moving to a .60 to see any real worthwhile increase. You may need to exercise a little "power management" in manuvers, to avoid folding wings in a high speed loop or such, but otherwise the move to a .60 is not that big a deal. That takeoff roll will be shorter for sure! Getting really vertical performance from models built like this takes an amazing amount of power because of the excess built in weight.
Have a good one, Dave

[Pippen]

Thanks, that helped me alot, I have narrowed my choices down to a OS .61 FX, or a .61 LA. What is better? the FX is more expensive, but is it worth the investment. Would the LA do me just fine? what do you all think?

Thanks alot for the reply :)

[Dave Robelen]

Hi Pippen,
The LA would not give that much more power for all the effort and expense. It will take something like the FX series to really feel the difference.
Regards, Dave

[Pippen]

Thanks alot, This question has been nagging me for the past couple of weeks.

I will go for the FX, and hope for the best i guess. Will I need a bigger fuel tank ( I have a 10.5 OZ tank ) for the model? and is wing folding a problem with powerful engines? I biult the model extra strong, because i knew I was gonna be upgrading my powerhouse soon. Is that a really big concern for me?

[Dave Robelen]

Hi Pippen,
That .60FX will drink well over one ounce a minute at full throttle. Many fliers go for a 16 oz. tank. You would probably be happier with the larger tank since it will give you about the same flight time as you have now.
Moving up in power makes it possible to break even a well built plane in certain manuevers. Full throttle loops or somthing like a split S at full power with a hard elevator pull really put the stress to it. If you are not ready to change the throttle in manuevers, just start the high load stuff at a bit less than full bore until you have the feel of it. Also, run a prop with fairly low pitch and all the diameter your plane can handle. This will give great acceleration on takeoff and keep that top speed manageable.
Have fun, Dave

[Pippen]

Hello Dave,

I have the potential to stay in the air for well over 20 minutes as it is now, but that is @ 1/2 throttle most of the time. I mostly want the extra power for takeoffs, and it is windy at my flying site alot of the time, so I need a little extra oomph when flying into the wind. I am not too aerobatic at the controls yet, it is a new plane, still trtying to dial in the right trims and stuff. I had to add 8 ounces to the nose to get the proper CG, and I kinda figured that might mean that the plane was biult for a larger engine? I agree with what you said about the prop pitch, sounds about right. I have one question though, I heard the term "snap roll" somwhere, and have been racking my brain trying to figure it out. Is it where you can make the plane lose all of it's flight capabilities for a second and make it topple nose over tail?? what is that manouver called??

well, thanks again for all your help

[Dave Robelen]

Hello Pippen,
The .60 should be just the ticket for you. When you throttle back to cruise, it will use about the same fuel/minute as the .40. The .60 will simply be loafing more. Meanwhile, you might as well put that ballast to work, eh? It's only money, right?;) The manuever you are describing is generally called a Lomshevak, the plane rolls and somersaults all at the same time. A snap roll is the result of pushing all the stick to the corner at the same time, say, full up, left rudder, left aileron and high throttle. The result is a very rapid rotation, primarily in roll. Essentially it is the same as a tailspin, but done in directions other than straight down.
Regards, Dave

[phuffstatler]

Pippen, the 8 ounces in the nose could easily have come from the radio gear being installed too far back in the fuselage, or some construction related weight in the back of the fuselage. I have a friend with the same plane as you, with a Thunder Tiger .46 on it, and he is quite pleased with it. Not a lot of extra nose weight, either. (I don't think any weights) It may be too late to do much about that right now. That big engine will help you get rid of some lead for useful weight, in the engine itself, so that is a good part of it.

You've mentioned that you fly mostly at half throttle. You don't know what a snap roll is. With a .61 on the nose, with it's bigger prop, drag, etc. you're going to be heavier, slow down quicker, and fall out of the sky faster with that big engine on the front when the power comes off. It's going to be more demanding of your skills to fly and keep in one piece, and you're going to have learn throttle control, quickly, or you'll pull the tail or wings off of it. Yes, it can be done.

You may have noticed by now that I'm not a huge fan of grossly over-powering model planes, especially smaller ones. What good is the overall experience of unlimited vertical if the silly thing has a stall speed of 40 mph? Most every example I've seen of .40 size planes running .60's (or More!) has resulted in the landing speeds going way up, which puts lots more stress on your landing gear, especially on grass, and on you, the pilot. The planes have also tended to shake apart over time, though that's mostly being lazy on the prop balancing.

Oh well, do what you will. My two cents tossed on the table...

Phil in Austin

[Pippen]

phuffstattler and Dave,
Thanks for all the feedback!!

Well phuffstatler, that sheds new light on the subject. In answer to your question about the radio equipment, the equipment was placed in the right spots. The reason I had to add more weight ( i think) was because I have an OS .40 FX in the nose, and they are slightly smaller than other .40's. that may be a reason, but i am not sure.

Also, I will not be heavier, I will actually be slightly lighter, I have checked the weights, and i will be about 2 ounces lighter with the larger engine, seeing as how i will be able to take out the lead balls.

I fly relatively often, and i am fairly confident @ the sticks. and I dont think that it will make much of a diff with the .60 on the landing, seeing as how i am going to stick to a 11x6 or 12x6 prop at first, same pitch as what i use now. (does that sound right?)

My main goal is not unlimited vertical, it is a quicker takeoff speed. I have had more than a few mishaps before my initial turn( such as stalls ) from a too slow takoff speed, and I believe that it will definitly help me out in that respect. Thanks for your input phil, and let me know if i am on the right track with my thinking. I dont want to risk destroying my airplane, and i want to be fully confident with my descision.

Dave, hmm, I believe I have done that move more than a few times, just didnt know the right name for it, Thanks for clearing it up.

[Dave Robelen]

Hi Pippen,
As long as you remember there is a throttle on the transmitter, and the weight stays about the same, You should be good to go with the extra diplacement. More horsepower will also be an advantage if you begin to extend your aerobatic capabilities. Run it a little rich, stick with no more than 6" pitch, and you ought to have a really decent setup.
Regards, Dave

[Pippen]

Thanks Dave,
Wow, this site is a goldmine.

Finally, without much further ado, I have decide to go with the .61. lol
yes, the OS 61 is right for me i think. I flew this morning, and it reminded me how little power I had! I am gonna keep it rich, and go easy for the first few flights, and I ought to be fine. ( by the way, i tried a snap roll, and Boy oh boy. It was awsome!! I was able to get 4 snaps out of it. I am also woarking on perfecting an inverted immelman turn. those are fun! ) well, thanks for all the advice. I dont have any flying buddies around here, so it is hard to find a good discussion about the great hobby of RC planes.

Thanks again,
Pippen

[William Robison]

Hello Pippen,

I read the cautions about overpowering, and agree. But. One of my most enjoyable planes is a Diablo 40. It has been powered by a K&B 61 since I got it. Never been sorry.

The airplane will launch vertically out of my hand. Landings take a little more room, but landing speed is not excessive, and the K&B is a LOT lighter than the OS 60FX.

Dave, you mentioned a "Lomcevak." You acknowledged the high Gs in it, but did you know the load can exceed 16G doing one? I have no idea how many my Diablo has done, and while it gets a very careful IRAN after every few flights, there has been no sign of wing or wing joint failure, nor have I found any problem with the empennage. The only high G induced failure I've had was a hole in the fuel tank, it was proof of the extreme forces in such maneuvers. The tank had shifted forward with enough energy to punch a hole in it where it was pushed against the engine mount retaining screws in the back of the firewall. That was Gs AGAINST the normal line of flight!

But Pippen, until you have pulled a few Gs, and done some careful inspections, I woould advise against going to "3D" maneuvers.

Incidentally, the Diablo/K&B 61 flies with a 12x6 three blade prop.

In the Twin's hour, go for more Power!

Bill

PS: Dave, anything new on posting the spread sheet model?

[Dave Robelen]

Hi Bill,
No, Sorry. I was out of the house away from the phone and terminal most all day. I really did think about it though. Tomorrow, really!
Dave