I have my Model Tech P-51 (.60, 65” ws) in the basement ready to finish and finalize, but I’m a little concerned about the engine I purchased for it, only because of what I’ve heard and not experienced. The plane should normally weigh out at 10-11 lbs. w/o retracts and I currently have Robart Mechanicals in it, but have thought about Spring Air if they’ll fit.

Now I ask you, besides the type of plane in question here, will the OS .91 Surpass II be sufficient for this bird or do I need to upgrade to a 100 or 120? When I state sufficient, I mean with some authority, scale, not a piper….sorry piper flyers out there.

Hi!
11lbs nearly 5kg is rather heavy and your .91 FS will not fly it with great authority...but it will fly in a scale like manner!
If you want more oomph! Get a 15cc twostroke...like MVVS 15cc engine. A 20cc (1.20 ) fourstroke will only make matters worse
( more deadweight).

Regards!
Jan K

An 11 lbs. is rather heavy. The .90 will fly it, but if
you're looking for some authority, and are set on a
4-stroke....get a 1.20. You will have a pretty high
wing loading already....Put some motor in it !

Dave.

SInce you've already got a bunch of weight to deal with I'd recommend you look at the lightest big motor above your .91 Surpass. A Saito 1.00 might fit the bill . . . more horsies, less weight.

Ok, thanks for the replies!

So what I'm hearing is the OS .91 FS will fly it, I might need to keep the speed up and flaps down at takeoff and landing to reduce tip stall, BUT will I have to keep it at full throttle to fly or could I mill around at 3/4 to 1/2 throttle???

I've put in a for trade request for a LNIB Saito 100 for my NIB OS .91 FS, so hopefully someone will bite.

Cheers!

Can't see you milling around with a mustang. The horse wants to run. Watch the flaps on takeoff. If you take off with them on, and try to climb steep, you could end up in a tip stall, spin situation and that will be the end. Make sure you climb out fairly flat till you learn the flight tendencies of the plane. Have fun

100 saito is better....but you still will be lacking.

If you want to be able to power down and run at 3/4 throttle you will need to get up into the 120 size motors. or 108 for 2 stroke !!

I agree....the Saito 1.00 is not enough power. A 1.20
O.S. Surpass would be good, or the O.S. 1.08 FSR
two stroke is a brute.

I would have put the YS 1.20 (supercharged) in it.
Forget the flaps for take-off....let it run out at full
speed, before you ease it up....the flaps are cool for
landing....but keep about 3 clicks of throttle on it,
bring it in fast, and grease it in. Don't try to float
it in !!!

Done Deal....Dave.

I had an OS 120 Surpass III on a 12 pound Top Flite P-47. The engine flew the plane with authority. If want to fly scale, just throttle back. IMHO a warbird weighing 10 or 11 pounds with a 65" wingspan is normal. Most warbirds need nose weight so it is normal to put the biggest engine you can in the nose of a warbird. If you ask this question in the warbird section you will find that most people will recommend at least a 120 four stroke. Oh and by the way, never use flaps for take off. If you do, you will not have your warbird for long. You want to build up as much speed on the ground as you can before you become airborne. If you do not have enough speed, the plane will tip stall faster than you can react.