Pond Skipper

Its a good prop design no doubt, made for 15 size combat planes. The thicker airfoil will give good thrust with the
.074 however the extra mass and drag on the engine is not optimal. I'm not sure if the 6x4 was out back then.
http://www.apcprop.com/product_p/lp06040(1).htm



These should be good for speed.

For the .074
New is this: 5.5 x 4.5
http://www.apcprop.com/FPV_Racing_p/lp05545e-b4.htm


For an .09 engine
New is this: 5.5 x 6.5C very low weight and thin
http://www.apcprop.com/product_p/lp05565ec.htm

Pond Skipper

On another note the MA 6x4 weighs in the same as the APC 6x4 at 5.2g

Member comments:
APC 6.3x4 which spins at about 16500 rpm when maxed out on 10% Nitro
APC 7x3 gets 17.1k nitro unknown.

The guy with the 7x3 ended up doing a full throttle dive and bent the rod.
He was using 3 shims think 30% nitro mix of various fuels he had on hand.
Car and Heli fuel.

20% castor and 30% nitro with a lighter prop should avoid any bending.



I think the stubby plane would benefit from a prop with good thrust such as the 6.3x4.
For me though prop mass and airfoil thickness is keeping me from using it. 1 member
on here noted the MA 6x4 was a very good choice for his plane. Plane, prop and engine
must be optimized in unity after weight is no longer adjustable.

Servo wise I am not sure till I see the plane Its up in the air my guess around 40oz for the
elevator and ailerons. May use a Vertigo .07 with a tuned pipe. Spins a 5x4 at 28k.

MJD

My Feedback: (1)

The 6x4 may be the bee's knees, if I can find one at the LHS I'll check it out. I'm only familiar with the 6.3x4 so far, it is beefy enough to take a bunch more engine.

Pond Skipper

It should be a worthy prop really depends of the application. We can all agree the .074 is a good
engine no bearings though and not meant to run high sustained rpm's. It does have 160 deg timing
and could run with a pipe if desired. I am going to beat you to it Mike, all set up in the test stand
after work I will make some noise and vid the results, will have rpm, hp , thrust and static mph data.
Note the bullet spinner it is meant for the Cox engines I tapped it out for 4mm it is a perfect fit for the
power of the .074. I consider the weight too much for .049 engines. I have done one up for my TD .09 too.
89g with prop spinner combo. Should make really good thrust and hit 18,400 rpm static is my guess with
20% castor and 30% nitro will be used.

If so great sport set up that should unload close to 85mph :
Static est: 21oz thrust / .232hp / 173.1w / 70 mph

The MA 6x4 has a wider blade out to the tips and should
make close to 25oz thrust if vertical is lacking.

MJD

My Feedback: (1)

Of course you'll beat me to it - I'm counting on it. The local hobby shops were a long time before anyone had the 5.7x3 on the shelf, I found some of those first time not too long ago, and then I finally saw/felt the big diff between that and the 6.3x4, the 5.5x2 etc with those mondo hubs.

My .074 is currently on a 3ch bipe Hacker Funny (it's funny looking alright) that has absolutely no need for any more hp than a Babe Bee, so its talents are apparent but a bit wasted - it pulls the living crap out of it at full throttle.

Pond Skipper

Lol yes I remember the first flight vid it was up and away to spec height with ease.
A MA 5.5 x 4.5 would be worth trying


Static Tests Published on Dec 9, 2015

AP .09 Hornet / 25% nitro
MA 5.5x4.5 / 19,300 / .92lbs thrust / 82mph /.213hp / 159w

Another 25% nitro:
APC 6.3x4 / 17,280 / 1.3lbs thrust / 66 mph / .22hp /164w

Pond Skipper

https://www.youtube.com/watch?v=u1XHtbi5sWQ&feature=youtu.be Published on Oct 19, 2016
Norvel .074 / APC 6x4 - 17,603 rpm / 30% Nitro 20% Castor
Static: 19oz thrust / .203hp / 151.4w / 67 mph


Condition is new with less than 20 mins total run time.
Anticipate around 22k unloaded 83 mph good sport prop no
trouble with idle. Perhaps if you unscrew the exhaust nipple
Should hit 18k after some air time, muffler is robbing rpm,
could add an extra shim.

Per Chris he gets 16,500 with the 6.3x4 non stock muffler.
This is after some flying time on the engine I imagine.

airraptor

My Feedback: (66)

well I tried 5 times to put prop data in here but the format they use auto-formats it and Fs it all up

Pond Skipper

What is the bare weight of the Midget Mustang as shown? I like the thrust of the
prop for acro flying mixed with some speed. The pitch is suffering some perhaps
the MA 5.5x4.5 should be tested next. I would like to be closer to 100 mph with
good vertical if possible. With a small true turn type spinner to cover up the high
pitched portion of the prop would allow a 6x5. Will have to do some digging by
the time you add up the weight of the spinner and adapter the weight gets to
be a bit much on the top end rpm.

18k static would be ok around 22k unloaded 83 mph with a lean mean plane.
The stubby plane needs extra power to get past it's design type for speed.
Not sure what I will do yet, I have plenty of different engines, just I would like
a low weight option to keep the glide nice. My flying field is a bit rough certain
times of the year.

airraptor

My Feedback: (66)

APC's prop data shows at 18,000 rpm and zero airspeed it takes .196 hp to spin it at 18,000 and makes 1.567 pounds of thrust. and should fly a clean airplane at 104 mph at 24,000 rpm assuming the hp stays the same at .197. Need to find the power this engine makes at 24,000 so I can see how much it will unload

Pond Skipper

I like using this for my calculations it has panned out well with my speed projects.

http://p51.christiani.nl/staticthrustcalculator.htm


Yes I have consulted the APC power charts they always
tend to show more thrust per given rpm. Which is promising
when propping for top end speed. If I go with a speed solution
for the plane I would much rather use an engine with bearings
hence the Vertigo .07 mention in a previous post. The thing is
I keep trying to get some use out of the Norvel .074 and it get
pushed to the side in lieu of rpm beast.

Mr Cox

In my notes while bench running the Norvel .074, I have 17500rpm on the 6.3x4 prop (with stock muffler) and 10% nitro (with 20% all castor). One thing to look for is the position of the throttle barrel at full throttle, it doesn't always end up correctly (length wise along the thread) but it can be shifted by half turns in order to end up in its least restrictive setting at full throttle. On mine it was off by half a turn, and the full throttle was also limited by the eccentric throttle stop screw (just remove it and use the servo limits instead). There was perhaps around 500 rpm hidden in getting the barrel in the correct position, it is quite easy to remove the mesh for a closer inspection.

I tried a grey Cox 6x4 prop once, but the engine threw it a way, so I took that as a sign and haven't used it since then...

I've only seen one engine review I think (it is available on sceptreflight.com: http://sceptreflight.com/Model%20Eng...20%20.074.html) and this one indicates that max power is delivered around 22 krpm, but they don't show the power curve and the provided prop data are much lower in terms of power. As AndyW has shown there is a lot of potential by using a tuned pipe, so maybe that could be tested too before resorting to a much heavier(?) car engine conversion.

Pond Skipper

Hey Chris, here was where I had found your 16.5k report for the Super Chipmonk.
The Sceptre site states 15.5k with a Cox 7x3 and 19k with a 6x3 using 15% nitro.
This evening I can bolt on the 6.3x4 and see if it hits 17.5k VS 17.6k seen with
the 6x4. Sceptre site states .38hp at 22k would have to spin a 6 x 3.9 prop at that
rate which is impossible.

Andy was able to spin a APC 7x3 up to 19.3k in the end with his modifications with a CS pipe.
First test he noted a 2k boost.

https://www.youtube.com/watch?v=lrOTQv1YUIE
https://www.youtube.com/watch?v=KLJdlZqgnGc 18.5k with a Cox 7x3.5

Pond Skipper

I have the heli exhaust throttle setup for the .074 and can adapt a Profi pipe to it.
Can just use the carb and tap out the throttle stem from the heli muffler or use
a open venturi and the heli exhaust restriction.

Pond Skipper

Much lighter car conversion add 19.6g for pipe and header.
The Fuji was able to power the .09 Dart to 148mph with an HQ carbon prop.

https://www.youtube.com/watch?v=7IaQ4o_qXZ8

Mr Cox

Yes, that sounds like the very first run in the plane (7-8 years ago?). From memory the engine was barely run-in, used an extra head shim, had a small piece of silicon tubing on the exhaust, had not seen the problem with the barrel in the carb etc.

All these little things add up, guess one shouldn't focus to much on the exact numbers from one engine to another (accross the pond too) but one can find some small relative gains in each individual engine which in the end makes a for a decent improvement. It looks like the tuned pipe is really the way to go though, for some real power.

Mr Cox

That's strange, I thought the stock Norvel came in at around 74g (including muffler), what material do you have in that spinner-nut..?!

Mr Cox

That's quite heavy though, you can just take a thin walled aluminium tube, use the two stock screw for attachment and block the front side of the tube (needs to be smooth on the inside I guess.)

Mr Cox

Just noticed that AndyW is not using the stock carb?
It looks more like the G-mark .12 carb (with added adjustable airbleed?), that would certainly spice things up too!

airraptor

My Feedback: (66)

The MA props are lower pitch than stated. compare them to a APC of same size and pitch to see this your self. I measured them also on a pitch gauge.

Pond Skipper

The heli muffler comes out to 34.2g with pipe
The best option would be the Sportwerks header pipe.
As mentioned before the spinner is from a Cox .09 that
and the prop adds weight for sure.

Would make this a big prop spinning beast, whole new range of props.
Here are some of my small car engine conversions.
From .05, .06 and .07 Now have a .09 and .12 too.
I have 4 Picco .05's my top choice for small planes, boats.

.....

Pond Skipper

I have these on order for another project carbon nylon mix very stiff strong at the hub
and low weight. The Norvel .074 could swing theses for a fun fly project if a tuned pipe
is used. Low weight profile plane would be perfect. But could be cut down with back cut
for the Mustang project.

Pond Skipper

Tried this without pressure fuel flow couldn't keep up with the pipe.
So tried the heli muffler on its own louder than the stock muffler
but not so bad. The stock muffler always looked too small for an
.074 and proved to be choking down the power quite a bit.

Stock muffler is 7.5g with bolts.

...

APC 6x4 Static Results:
Heli / 18,814 rpm / .248 hp / 185w / 21oz thrust / 71.2 mph
Stock / 17,603 / .203 hp / 151.4w / 19oz thrust / 67 mph

+ 1,211rpm / 34w boost in power not bad about what a Cox Pee Wee engine makes.

Reduced the rubber hose to add a bit more breath to the exhaust
and with a pressure tap I imagine 19k+ wont be hard to reach.
So around 22oz thrust 195w. Bigger expansion chamber and
exhaust.

...

https://www.youtube.com/watch?v=zjY3gjE-r3w&feature=youtu.be
Rubber hose looks cheap, was lucky enough to find some
aluminum tube a bit undersized, with a tap hammered stretched it into place.
Much better factory look, might find a home in the Midget Mustang after all.
Will bench test one more time to see how it does on pressure.

...

Pond Skipper

Ok ran it up with the finished muffler with pressure:

Static APC 6x4
19,147 rpm / 196w / .262hp / 22oz / 73 mph / should be a freight train with all that thrust.

5x5 should be a good speed prop 6x4 for thrust. Depending on windy day vs calm should
be a good engine without putting too much mass on the nose of the Midget Mustang.

da Rock

With a pitch gauge?

Not many people have those, how does yours read the pitch? in inches? How big a diameter will it handle?