? for choosing New Motor/thrust

[mag1]

As a newbie, I'm not sure as to how much thrust you need to move a plane of a given weight. What is the rule of thumb? Do you also need to know the wing area? I would like to build a DIY Brushless motor, but I'm not sure as to how to figure out just what I need. Thanks for any and all input.

[mlh1961]

As a rule of thumb you need;

50 -60 watts for simple flight, hand launch
70-80 watts for mild aerobatics and maybe ROG
100 watts or more for full aerobatics
and a minimum of 150 watts for 3D.

This is very general and they are watts per pound, so if you have a plane that weighs 16 ounces, you need a BARE minimum of 50 watts to fly.

Hope this helps you. If you post what plane you have I can give you some idea, using one of my set-ups. I am sure there will be more people chime in also.

Mitch

[mag1]

Here's the spec's. I have different radio,ect... but this is the plane. Thanks

[portablevcb]

The 50-60W minimum for simple flying is a bit on the high side. I know a lot of folks use those numbers, but, I've flown a lot of scale slow fliers in the 30-40W/lb range and they do just fine, including ROG.

Aerobatic performance numbers are guidelines only as the plane itself makes a big difference as well as the type of aerobatics, pattern, just fooling around, 3D, etc. For example, solid pattern performance needs a lot more power than simply doing loops and rolls around the field and 3D needs a lot of thrust at low speeds.

For the plane shown above you can find an approximate equivalent by figuring the max current draw (ESC rating) and the battery voltage. Multiply together to get Watt output of stock setup. The number will be on the high side since the ESC is probably rated a bit over what the max current draw is for that setup. It will get you in the ballpark for picking a new power system.

If you're getting that plane why not just fly it on the stock setup to see if you like that power output? Then if you want to go to brushless you can measure the draw and find one that has same or a little more power.

charlie

[mag1]

Thanks for the info. I knew I could count on you guys. The reason for going to brushless is I would like to get more flight time, as current times are pretty low. I guess I could always get a larger battery, but I liked the idea of lipo's vs the heavy nicads. :rolleyes:

[portablevcb]

LiPo's are the logical step to get more duration. Brushless will get you a little bit more, maybe a couple of minutes. Your best bet is to get a lighter weight plane :D

charlie

[Dr Kiwi]

That's going to need a big DIY motor - a double or triple I imagine - because the stock set up seems to be about 150W (and you would be better off with a little more). Of course getting rid of a 7oz motor and a big NiMh will make it lighter, but you still need a brushless outrunner the equivalent of a Hacker A20-22L or bigger (?A30), to spin a 9x5.5 @ 15A or so from 3s Lipo.

The 50-60W minimum for simple flying is a bit on the high side. I know a lot of folks use those numbers, but, I've flown a lot of scale slow fliers in the 30-40W/lb range and they do just fine, including ROG.

At the stock 18oz/sq.ft that is no slow-flying floater so you'll need some speed and power to get it to stay in the air. (typical slowflyers are only 5-8oz/sq.ft).

Cheers, Phil

[mag1]

Thanks for the input.

My wife bought me this one so that I wouldn't have to learn on my MM C-180 that I built last winter. (she dosn't want to see me digger it in) :D What a nice gal, feeding my new habbit. I've been busy in other aspects of life, so I havn't had the time to learn to fly, and it gets dark here early, so it's to hard to fly after work. So, to feed my building habbit, I'm working on a 2nd wing with flaps and alerions for the mm c-180, floats are done, and I thought a brushless motor would be interesting to possibly build. The DIY motors arn't to expensive, so I thought it might be fun to wind one up some night.

[portablevcb]

I fly my MM C-180 on a GoBrushless 18T (26ga) motor and 2sLiPo (7" prop, ~4A). Works great. I flew it on the stock IPS for over a year, then put in a Feigao, then the CDROM. The Feigao and CDROM had identical power output. THe plane actually works better on the 7" prop than it did on the 8"&9" props I have run on it.

My first wing had ailerons. Added about an ounce and little to the performance. It did let me play with sideslips during landings :) Make the ailerons larger than stock (wider chord). An inch wide would not be too much. Differential will also help as there was a bit of adverse yaw in mine. I did reduce the dihedral by about half. Worked good.

I put flaps and ailerons on my Dumas Bird Dog. A lot of fun, but, it took a it more power so I had a sp280 in it. 14ozRTF and I liked it. Only problem I had was I reduced the didedral to scale. Made it a bit twitchy in level flight. I'd leave in a bit more if I did it again.

Having two wings is the best of both worlds. The stock one for gentle floating around and thermal hunting. The mod one for doing those challenging touch and goes and side slips.

have fun
charlie