freeair

Guys, i have purchased an Extra 300 / 90 inch span model that comes with a fibreglass fuselage / sheeted foam wings and tail planes. what i would like to know is what size engine you guys would recommend for this size model ? i can buy a new MT-62cc at a good price. i intend on doing mostly IMAC flying not 3D stuff. thanks.

Rush7

My Feedback: (74)

What is the weight of the plane? I am thinking a DA 85 or Torch 90 would do the trick for you.

freeair

i really cant say what weight this unfinished model is as i have to sheet the main wings but at present the fuselage seams to be not to heavy as its light fibreglass construction along with sheeted tail plane. both main and tail planes will be covered with something like monocoat and the fuse will be sprayed with a few colors. don,t you think an 85 cc engine might be abit too much for this size 90 inch span model ?
one of our club members has a 2.6 extra powered by the DA-85 and it has heaps of power, my model is the 2.3 meter job. one other thing about the Torch brand of engines? are they made by the same guys that make the Torch Sparkplugs ? if so forget this engine. what i do like about the MT Engine is it is an exact copy of the great Zenoah Engine which means parts such as bearings / pistons / rings etc are very easy to obtain at a good price aswell plus the MT is ligher in weight to the Zenoah, the DA engines are very good i must say but a little over priced .

warbird72

My Feedback: (79)

I have the world models 80'' ws extra 300s. It has a converted 30cc homlite weed eater in it. It also has a tme smoke system on board. It wolnt hover but it flyes very well. All up weight  is around 15lbs.  

mrbigg

My Feedback: (21)

Perfect engine for what you want to do. Don't overprop it and it will work great. I've seen a G62 toss a 21 pound plane around like nothing. It was propped to rev though.

freeair

thanks, mrbig. the guy that sold me this model and new engine to come did recommend a prop of 23 x 10 apparently this MT62 can run props from 22 inch to 24 inch diameter, so i suppose the 23 inch with 10 inch pitch could be the go ?

mrbigg

My Feedback: (21)

I don't know. What I do know is that the MT is supposed to be a rip off of the G62. If has the same port layout as the Zenoah, then it's a revver. There are guys on here that have run 24" props on their G62s and like it. I tried a Mejlik 23x8 on mine and hated it. Slow spool up and the engine just sound like it was being bogged down. All you can do is experiment with props. I'd sure hate for you to put too big a prop on it for the first flight and have it not produce the thrust needed to keep it airborne. I seen a guy do this with a Saito twin in a Cub. It got off the ground but would barely fly. Almost lost it because it was barely moving above stall speed. When he got it down, he put a smaller prop on it and it was a totally different plane. You'd a thought he put an engine twice the size in it.

Jake Ruddy

My Feedback: (40)

22x10 is the prop for you.

mrbigg

My Feedback: (21)

That would depend on which 22x10 prop your talking about. The 62 needs to be prop for at least 7,000 rpm. Prop it for about 8,000 and you'll be shocked at the power it has.

mrbigg

My Feedback: (21)

Here's a pic of the G62's Dyno chart. Check out the power it starts making at 8 grand all the way to 10 grand.

freeair

they say the MT-62 is suited to props of 22 / 23 and 24 inch diameter, the cost of this big monsters are about $100 au each so i hope i get the right size to start with. a friend has a DA 50 with a 22 x 8 prop so you would have to think a 62 would need a slightly larger prop such as 23 x 8 / 23 x 10 ?????? any tips ?

mrbigg

My Feedback: (21)

Not if the MT62 is an exact copy of the G62, which people have said it is. Look at the Dyno chart. You'll see where it makes it's power- higher in rpm than the DA 50. Your putting the engine in a bigger, heavier airframe that will load the engine down, hence the need to let the engine get up to speed. Buy some cheaper props and experiment. I can tell you this, I put a Mejlik 23x8 on my G62 and hated it. Didn't let it rev in the air. That was on a 16 pound Extra with an 84" span.

octanehuffer

BME 58 with a 24x10.
Evolution 58 with a 24x10.
MT 62 with a 24x10.
G-62 with a 23x10.
Take your pick.

Rcpilot

My Feedback: (78)

I have a 75cc conversion engine in a 90" Extra 300L. Weighs about 18.5 pounds. Good power for this altitude. Swinging a Xoar 24-10.

freeair

looks like i might be going for the MT-80, a few have said the 62 is abit underpowered for IMAC flying and atleast if i have the extra grunt of the 80 cc engine i can allways throttle back and only use the extra power when needed like in takeoffs and vertical climbs.

Rcpilot

My Feedback: (78)

IMAC flying takes a LOT of power. You could probably fly in the Basic class with the 60cc engine, but thats it. The more advanced classes have maneuvers that require point rolls on the up-lines. I've been practicing the Advanced sequences a little. I need ALL the power I got for maneuvers like the Humpty, Hammerhead and Teardrop. Even the Goldfish requires a lot of power if you stretch it out and make it a big maneuver. My timing is slow, so my maneuvers are usually pretty big. It takes ALL I got to pull out some of those long lines.

I think you are making the right decision with the 80cc engine. It'll be a little heavier, but it is easy to balance out by locating your rudder servo(s) and tray farther back. The couple ounces of added weight won't hurt performance overall.

I don't EVER fly mine at full throttle when it is horizontal. The only time I give full throttle is when the nose is pointed straight up. Throttle management is key on something with this much power.

Don't forget to tune your low end needle. These large singles really thump if you let the low end run too rich.