jst4fun

My Feedback: (4)

Just wondering what a saito 72 would do on a wm midget mustang? I am picking the plane up this weekend and I have a 72 lying around that needs a home. Does anyone have any sugestions?? I would really like some input on this because i am taking the plane to florida the next weekend w/me to fly down there while im on vaca. Can somebody let me know about this selection and what prop size that i could throw on this plane????

Thanks

AirGar

My Feedback: (7)

Personally, I don't think it's enuff motor for the Midget. Mine had a ST 90 with a Pitt muffler, and this seemed to be a great combo. If your not looking for speed, you'll probably be ok. Don't expect much more than 50-60mph, however.

Gary

Jim Oliver

My Feedback: (1)

Hi,
One of our club members has the WM MM with OS 91 four stroke; it is enough but certainly not too much. The Saito 72 will probably be rather bland.

Funtanas56

i honestly would go to a OS 91 FX 2 stroke yes a 2 stroke its way above what is recomended for the plane but trust me you will like it speeds of up to 150-160 are achivable with that engine just watch your throttle management and you will be fine just rmber you can alweas throttle back

js3

My Feedback: (3)

Wrong. Sorry. NO WAY will the WM MM and the OS 91 FX combo do 150. No way. Maybe 125 if you have a tuned muffler on it. Perhaps you're speaking Kilometers/hour rather than Miles/hour?

I'm not intending to flame you but I have personally flown this exact combination and while the speed was enough to be considered fun, there is no way it was even close to 150 mph.

speeddmn

i have owned 2 of these models and i agree, 150 is an unreachable expectation for this aircraft. one of mine had a super tigre G-90 and the other one had a saito 91 4-stroke. bolth engines pulled this plane pretty well. 65 to 70 mph im guessing . but the nice thing about this plane is its fairlly easy to fly. you'll find that it does like to glide and takes some runway to land. so to answer your question i think the saito 72 will be rather disapointing. hope this helped.

Homebrewer

My Feedback: (8)

A TT .91 was perfect combo and weight for this airplane. Using another 4 stroke required a little extra nose weight. With a 13x10 prop running 20/20 fuel this combo was incredibly fast. The TT .91 offers similar performance to the Saito 100 at much lower cost.

A Midget Mustang 14x6 APC slowed it down a little and gave overall decent vertical performance and shorter takeoffs.

Funtanas56

i dont know how you broke in your OS 91 FX or what kinda fule you run on it or prop size but i have been acuratly been getting 154.5 on my radar gun i use 30% heli fule and 13-8 prop i gurenty you try that combo you will get 150 to 160 i will be happy to get a movie to prove this and i am using the STOCK MUFFLER!!! its true go with the 91 2 stroke but be aware 30% will not make your engine last long i have done this as an attempt to see how long the engine will last science it was given to me. i suggest you mesure the speed again js3.[8D]

Funtanas56

il be happy to send you a movie of it buddy you must not be breaking the engine in the way i do [8D]

famousdave

My Feedback: (61)

NiCe Spaelling aNd Grammerr. I'd get a new radar gun. You must have one of those guns the cops used in the 70's that clocked trees going 80 just by flicking the wrist... I'm not trying to be a jerk, but the math just doesn't work.

I had a Patriot with a Sport JETT 50 spinning at 19,200. It was the fastest prop plane anywhere I brought it. That plane JUST made it to 150 in a mild dive, It might have gone faster in a power dive but at that speed it was barely controllable (i.e. elevator was real slow) I have flown the MM, it is not built to survive those speeds for long. It is a cool plane though.

An OS 91's max RPM is 16,000 , pipe it and run 30% and yes - you might get 17,500 out of it, but probably not with that prop. That rod won't be sticking around long at that RPM either. At that RPM if your plane weighed nothing and had a Cd of Zero you might get 125 MPH out of it with the 13x8. To get 150 you would need close to 21.000 RPM. Not going to happen with OS. Not even on 80% nitro.

Now if you lightened the MM and put a good engine like a JETT or at least a ROSSI, you might get to 150 in a dive, but you also would probably fold that wing. Both those .61 sized engines make more power than the OS.

I have flown the MM with a piped Rossi. It went through the traps at 138 tops, and that was with sealed surfaces, no gear (we used a take-off sled) and no rudder. We shaved .75# off the gross weight. It looked like it was doing 200 though......

Again, not to be a jerk - I'd check your radar setup. Something's gone fishy in the swamp...

DP

Funtanas56

may i also not like the way our field is look at it and tell me how much wind we would get at www.sarasotarc.com we are on like a
mountain people we get the worst ammount of wind you can imagine espicialy during this season thats why i am getting 150 and trust me i have been im planes for long enough to tell what 150 looks like without a radar gun[8D]

Overlander

I am considering buying a used MM with an OS 91 4 stroke. I have a lot of experience flying electrics in the 2.5 3 pound range with brushless power. This will be my first gas plane. Does the MM have any bad flying characterisitcs?

-Todd

DaveR

My Feedback: (7)

Methinks Funtana needs a new radar gun. I was just on Bolly's website looking at their online book. http://www.bolly.com.au/book/Book.js...er=2&Section=4. It has an RPM/pitch chart. It would require 20000 RPM with an 8 pitch to reach 152 mph. There is no way an OS 91FX would hit 20000 rpm with a 13-8, it would take EXTREME measures to get a 10-8 to hit 20000. Not to mention the fact that APC's website has a formula for safe RPM on props. For glow engines, it is RPM x dia =< 190,000(in other words, a 10in prop no faster than 19000rpm). From my observations, most people overestimate the speed of their planes. Example, a 10-6 prop at 14000rpm is 80mph, but on a hi-drag trainer, my guess is somewhere around 65-70mph tops. Also keep in mind, drag goes up exponentially with speed. That's something the book didn't address. 100mph is readily obtainable with a MM, more than that really takes a honkin' motor.

Flyboy Dave

My Feedback: (21)

The Midget would honk with an OS 1.08 FSR in it. You Guys are dreaming
about those RPM's with the .91 [X(].

Dave.

DaveR

My Feedback: (7)

Flyboy, you might be surprised at what some of the 91's will turn. The ASP/Magnum 91s/stock muffler spun a 12.5X6 Bolly Clubman(APC clone, not their good CF props) 13800 on 5% according to a british mag. MAN tested a ST G90 w/hideous stock muffler and 5%; it spun an APC 11X7 14180rpm[X(], also a Bolly 10.5X8(probably Clubman) 14760rpm[X(][X(]. I've been researching this due to my interest in a G&P F-18 pusher, this configuration limits you to an APC 11X7 as the best prop. I figure both of the above engines make similar power. I'm betting that with a Jett-Stream or Ultrathrust muffler and 15% nitro, either motor will come close to 15000rpm on the 11X7, not bad for about $200. An SJ-90 turns a 12X6 APC 14700, I'm guessing an 11X7 would go about 15500, no more than 16k for sure. How long would the Magnum or ST last at 15K?? maybe 8 sec, maybe 100 flights, neither one costs much to rebuild, or replace for that matter. The point of my previous post was to point out that people's planes generally don't go as fast as they think. Even 100mph is difficult to obtain. The above 11X7 at 15k is only 100mph assuming a clean plane.

Flyboy Dave

My Feedback: (21)

Bad news, DaveR....I think the Brits had a bit too much brandy in their tea that
day....the new ASP (same as Magnum/OS clone) with the front needle is rated....

....that's RATED....at 11.5 with the 12-6....as you can see. You will never get
close to 14K with these engines....much less the rediculous 18-20K these Guys
are talking about. A Jett .90 turns 14.5-15K.

Even with a reasonable prop....a 13-6, 13-8 they won't go much over 11K,
at least on this Planet.

Dave.

DaveR

My Feedback: (7)

Flyboy, I haven't personally run or tached either engine. I did notice your chart doesn't show the "S" model of the ASP/Magnum, it's the old one. The ASP test was reprinted on JustEngines website. The Supertigre G90 numbers came from Model Airplane News, December 96 issue(I have it), Mike Billinton tested it. Here are the numbers from it on 5% nitro:

Prop Open Exh ST Muffler Bolly Pipe at 480mm

10X6 MK 15080 n/a
11X7 APC 14960 14180
10.5X8 Bolly n/a 14760
12X6 Maestro 13140 12550
13X6 MK 12770 12250
12X12 APC 10550 9790 10930
14X7 Graupner 10220 9580
15X6 Airflow 10140 9370
15X7 Bolly n/a 9290 10290
13X10.5 MK 9900 9080
15X8 APC 9440 8640

I left off the huge props and most tuned pipe numbers as their rather meaningless unless tuned for a particular prop. But as expected, the pipe adds about 1000 rpm over the ugly ST muffler. You can say this test is BS too and I couldn't prove you wrong, but I don't think Mike Billinton did BS reviews. His numbers on the OS140RX is spot on with the various pattern fliers. Other numbers are peak hp, 2.35@14418(open), 2.34@11670(Bolly), 1.97@12768(ST Muffler). Torque, 229@9000(Bolly), 220@7300(open), 186@5923(ST muffler). Personally, this tells me it has one WIDE powerband when looking at the open exhaust numbers.

Flyboy Dave

My Feedback: (21)

More bad news, DaveR....

....I don't know why you keep calling me out....but I'll explain the facts of life
to you one time, so pay attention. If your going to quote performance numbers
off some chart that Joe schmuck or Mike Billinton posted (never heard of him)
you're going to be chasing your tail for a long time.

We started talking here about the OS .91FX....not the ST .90 or the OS 1.40.
But being as you brought it up, lets look at those ST #'s shall we?

Notice that the high #'s are open pipe. Where are you going to run an open pipe ?
Look at the 10-6 #'s....that"s a .45 size prop. I have .45's and ..60's that will
out perform that WITH a muffler....don't make me put a pipe on them.

If you get to the reasonable .90 size props, like a 13-6, 13-8 (which is small) you
will find your engine right back in the 10,000 rpm (dog) range.

Go into the 11-7, 7.5, 8 range....again, your .90 gets trounced by .60's.

Another factoid of life is....just because some Schmuck gets some rpm number
running an engine open pipe, under ideal test conditions....out back in his little shed
....with some props and equiptment we never even heard of, and you won't
find at the LHS....do you expect to get the same results on Sunday....

....at your field (altitude), with your fuel, plug, and your prop, with your muffler ?
Nice try, think again.

The only stat you showed (12x12) with the Bolly pipe (whatever that is) showed
a meager 400 RPM increase over the open pipe. That's not even worth the effort,
much less the expense.

Please don't quote me any more numbers you read in some magazine....

and enjoy RCU....out there in the "Midwest"....

Dave.

DaveR

My Feedback: (7)

I apologize for "calling you out". I didn't realize my post deserved such a response.

Flyboy Dave

My Feedback: (21)

Not a problem, DaveR....

....I read your big post before you deleted it. No harm....no foul.

Now, there are some .90's that will turn up some R's....and create some speed,
but most bare the names OS, Rossi, and Jett....I have a few myself. The last one
down belongs to Esten Spears....it is probably the meanest of the bunch.
It may be a .95.

These babies will twirl some lumber....

Dave.

CheezeyPoof

I run an OS 1.08 in mine. Sort of like having a 454 in a Camaro.[X(]

Jim Oliver

My Feedback: (1)

Hey CheezyPoof,

What muffler are you using on the 108? How much surgery was required to make it work?
I have a Jett 90L w/Jett muff looking for a home, the MM could be it if everything would fit without too much cutting.

Thanks,

AirGar

My Feedback: (7)

Hey Jim

Git yourself a 60 F-20 for that Jett 90, you won't be disappointed!

Personally, I think the Midget Mustang screams for a "Pitts" style muffler, which is what I had on my ST 90.

I think with the Jett 90, you'd really have to do some hacking to get it to work. There's also a very good chance the exhaust (muffler) would be to short, and you'd end up having to add an extension. (You don't want to do that with a Jett)

The MM is a real looker, and you sure don't want to "ugly" up that pretty cowl!

You could also check with Dubb Jett, and talk to him about muffler mods, if this is the combo your set on....maybe he has something?

Hmmmmm...a Jett 90L with a Pitts muffler.....I'd bet that would sound BAD ASS!!

Gary

Falcon XR

I've got the World Models midget mustang and it sure is nice. I had a O.S. 1.20 hanging around and thought why not? ( I know someone out there is already frowning)

Anyway with a 16x8 APC prop and 20% nitro it is one sweet airplane plus in a shallow dive on full throttle it sounds quite real. Certainly draws a look skyward.
It is not a straight forward fit with the 1.20 but the air frame handles the extra weight nicely once I strengthened all the usual areas.

It is quite quick as you could imagine but not as quick as what some people have suggested a Midget might be capable of. Still I just love the overall performance of this plane.

Falcon XR

Owps, sorry some pics might help

Falcom XR