Not sure where to post this. I'm building a Sig Midstar for a second plane. I bought a TT .46 Pro to put in this plane and am wondering if I over bought and shouldn't just save this engine for another project and use a .46 la or a TT gp .42, etc. Any thoughts? Thanks.

peace

The TT Pro 46 will be great on a Mid Star

+ 1 for Jim's response. I had a Mid Star long ago and used a TT46 on it. Its a Great combo.

One of the guys at the club flew a similar combo and it flew really well.

I'm stickin'. Thanks all!

peace

It will not be too much for the plane but if it is to much for your flying skills then go for max thrust. Try a APC 11x5 prop or a 11x5 MA which is closer to a 11X4 in pitch but more blade area.

A .46 is a good engine for it.
Now some guys were running the .50, .52, .55 and even the small block .60 engines on planes like these. so the .46 engine is perfectly suited for it.

Is it okay to use a 11" prop even though the manual only recommends 10x6, 7?? Over proping won't hurt the engine?

peace

HarpHunt,


Even a prop as large as a 12x6, will not overload a .46 sport engine.

It will keep RPM down a bit, so the plane will be somewhat slower in flight; somewhere around 10,500. But thrust would be pretty high, so it will not slow down much going up-hill.


Overloading only becomes a case, if RPM on the ground is bogged down below peak torque, which for a TT should be around 9K.

Good to know! I've a .46 la in my Lt-40. Could I run larger props on it? Thanks.
peace

HarpHunt,


The OS.46LA is a rather weak engine, but you can still run a 12x6 on it.

Don't expect much over 10K, though.

Watch for overheating.

Use your TT 46 Pro. You have a throttle control to regulate your air speed. Learn to use it. It only takes a few minutes.


Ed Creger

The Mid star probably needs at least a 46. I wouldn't worry too much about excessive power. That is something pretty hard to achieve

Quote:

ORIGINAL: blw

The Mid star probably needs at least a .46. I wouldn't worry too much about excessive power. That is something pretty hard to achieve

The [link=http://www.sigmfg.com/IndexText/SIGRC56.html]Sig MidStar 40[/link] is designed by its manufacturer for an engine as small as a .30...
But it probably will fly off a paved runway with a .19; or maybe even a .15 engine with a longer take-off run.

In fact, its flight would be more scale-like with a smaller engine.


But if used with a larger engine, perhaps even a .55-.56 (a .61 frame engine will make it fly like a floor-tile...), the throttle can be modulated to keep its speed in check.

Remember the Goldberg Falcon/Skylark 56? It too was designed to fly with a .15 to .19 or a .19 to .35, I forget which. The latest versions of the series recommended a .40 to .45, IIRC.

It is funny how our idea of reasonable power has changed over time.

In 1971/72, my wife's Falcon 56 three channel was powered by a reasonably energetic Fox .25 baffle piston engine. Our grass field was considered average in the south Jersey area. Her Falcon would not ROG (takeoff from the ground - Rise Off Ground). It had to be hand launched. Paved fields were a rarity in those days. We adapted to using the grass field, or a good hand launch. With the point being that your model with a TT .46 Pro shouldn't have any problem taking off of any kind of flying field,

Of course, you are probably wondring about how the largish engine will affect the balance point (the correct term for modeling's Center of Gravity - which is incorrect). And you are right to be concerned. Generally, the engines that you have described as substitutes will be four to five ounces lighter than the TT 46 Pro and they just might make balancing less of a chore.


Ed Cregger

There is one at my field, and I'm fairly sure it has a 46FX, but I could be wrong. It reminds me of my Sig Kavalier with a Saito 56.

You can get those models too light where they bob like cork in a little wind. You need engine power to enjoy windy day flying, and not afraid of it. Imo

Yeah, but they are more fun when they are super light.

If he is determined to replace the TT .46 Pro with a lighter engine, for which I could not blame him, and if money is no object, he might want to consider one of the .30 to .39 ball bearing schneurle ported engines. They deliver more horsepower than their larger plane bearing cousins and their throttling is infintely superior. Frankly, I favor the OS .32 F/SX series.


Ed Cregger

I'm not determined... I have a .46 la on my lt-40 which seems to be adequate power, even at 1/3 to 1/2 throttle. I began wondering if the midstar might be too small for the more powerful tt .46 (or the TT too powerful). It is rated for a .30 to .40, but yes, our idea of reasonable power has changed. I was wondering how reasonably. I guess I was wondering more if it wouldn't be wasted on the midstar - reserve throttle that wouldn't be used. Probably overthinking

peace

Either way, it's all about having fun.

You won't hurt anything by using the TT you already have on hand. You can always prop it for lots of vertical pull vs higher airspeeds.

Ienjoy swapping out engines on a plane to see how much it changes and have found smaller less powerful engines can be fun too, just different.
The Irvine 25 Iused on my Kadet Jr was lots of power while the OS26 Four Stroke was not but it still flew really well.

Since you have put it that way, yes, if I already had a lower powered, but acceptable, option, I would choose that over the TT .46 Pro. As you have pointed out, the OS .46LA handles the ARF LT-40 well. No need to tie up your higher powered engine on a floater. It has been a fun conversation. Thanks.


Ed Cregger

Evolution 40NX, weighs about 10 oz w/o muffler. Factory muffler 2.5 oz. Jettstream 4 oz.. 15% Powermaster blended oil.

Factory mufflerAPC 9x616,500 rpm
APC 10x5 15,600 rpm
APC 12.5x4.515,500 rpm
APC 10x613,980 rpm
Jett red muffler APC 9x618,400 rpm
APC10x516,380 rpm
APC 10.5x4.5 17,190 rpm
APC 10x614,800 rpm sensitive needle setting with this prop.

This engine seems to like rpm. 10x6 with Jett muffler may be too much. It will need to be flown to see if it unloads in the air.

Energyman

Energyman, I almost suggested the Evo 36 because I forgot about the newer 40 NX.