Joe123s

with an os 46fx. currently using a ma 10X6

adam d

if you look at the planes for your plane it should say

adam d

plans

Joe123s

they are at my parents house.. its and lt 40

DBCherry

My Feedback: (4)

Try an 11 X 5 or a 12 X 5. They'll produce a bit more "torque" which will give a little better vertical performance, and will let the plane slow down a bit more for landing.
Dennis-

phread59

DB is right on the money. I would also say try the same sizes in APC props as well. The APC's I feel may work a little better on that motor IMHO. It never hurts to try different props untill you find a combination that works for you. I have about 30 some different props in various sizes. And I only fly 40 to 60 2 strokes and 80 and 120 4 strokers.

Mark Shuman

Mindwarp

Yup. Speaking from experience my LT-40 flies far better with the 11x5 than the 10x6. Our field is surrounded on three out of four sides by fairly tall trees, so take-off's and landings have to be steep. The 11x5 prop gives me far better power output than the 10x6 for those sharp take-off's, and a lower idle speed for those short approaches.

As always though, try a few different prop sizes and see which one suits you best.

Cheers,
Neil.

CafeenMan

10 x 6 is too small for a .46. I second the 11 x 5. Maybe even a 12 x 5. Lower pitch will keep the speed within reason and allow the plane to slow down more. Will also give better acceleration for getting of trouble.

Joe123s

im going to see how the 11/4 works and maybe try an 11/5. i heard a 12/5 was too much for the 46

CafeenMan

Joe - I have a 12 x 5 on my .46 and it turns it fine. I think an 11 x 4 is a little on the small side. It's less work than a 10 x 6 which I also think is too small.

For each inch you add in one you subtract in the other and have the same load. This is a rule of thumb and not an exact swap.

9 x 7 = 10 x 6 = 11 x 5 = 12 x 4

See? All those props would turn about the same on any given engine. So if a 10 x 6 is too small then so are the others. But... wehn you start getting farther away from the "base" prop the rule starts to dissolve. In other words, the reality is that a 12 x 4 would probably not be too small. Hope that makes sense.

BTW - those are just an example - none of those props may work for your application.

BarracudaHockey

My Feedback: (11)

Here's the link to the OS page that talks about prop range for that engine. I had to look around too cuz I was used to messing with 40's and I bought the 46 for my Extra 300.

Happy Hollidays.
Andy

http://www.osengines.com/engines/fx.html

minnesota crash

What would anyone suggest for prop size for kadet senior-surpass 70- for slow flight?

grittykitty

I would second CaffeenMan. I have an Avistar select with the .40LA, and I run an APC 12x4, which works beautifully. Since it has a lower pitch, the spool up is good, giving it excellent climbout, and slows down nice for landings. I did have to go with slightly larger diameter tires, though, to get comfortable ground clearance.

grittykitty

minnesota crash,

Recommended for the Surpass .70 is:
Sport & Stunt models: 11x8,11x9,12x7,12x8,12.5x6
Scale models: 13.8x8,14x7,15x6,16x6

For slower flight, I'd use a larger fan/lower pitch. Better spool-up, torque, and climb-out . SIG recommends a .40 to .46 engine on the Kadet senior, so check that CG!! The surpass is going to be heavier, and reinforce the firewall, as the bigger engine has more pulling power on the plane. And, as in my above post, check your ground clearance. If you take off / land in the grass, little ground clearance is going to stall the engine, and if you land on pavement, even a small bounce could cause a prop strike, and do some serious damage.

Maybe CaffenMan can weigh in on this one........

Dewalt17

Actually a 10x6 and an 11x5 are exactly the same performance wise. I have a book just for props and the performance numbers for a 10x6 and 11x5 are the same. My Nexstar which has an OS 46 came with a 11x5. After a few bounced landings it took a couple nicks out of the end of the prop. I now use an APC 10x6 which has the same performance just a little more ground clearance while im still working on greesing those landings.

Montague

What book is that? I'm curious, because my experience does not match what you are saying.

Propeller performance is affected by way too many factors to make a blanket statement that two sizes of prop are the same. Airframe and engine design are just two of the big factors.

Not only that, but the same size prop in two different brands will often perform very differently in the air.

There might be some engines and airframes out there where those two size props handle the same in the air. But I am sure there are airframes and engines where there is a noticeable difference as well. A high-drag trainer such as the Nextstar is going to show less effect from changing props than a cleaner design. A clean high-speed plane, or an acrobatic plane will show much more of a difference.

Different engines in the same size also seem to prefer differnet size props. The porting and timing of the engine does matter, though most sport engines are pretty close to each other. Engine performance is not linear, so differnet engines produce their peak useable power at different RPMs and with differnet props.

For example, the OS LA series of engines generally to like to spin bigger props at lower RPMs. If you put a smaller prop on them, they don't turn up the revs other engines might, but when you put an over-sized prop on they work better. Other engines I've run really don't like turning the big props, but come alive when lightly loaded with a small prop that allows them to really crank up the RPMs.

FHHuber

Performance of an engine/prop combination also depends somewhat on the aircaft, engine tuning and pilot skill...

The 10X6 to 11X5:::
Should see a lower top airspeed with the 11X5, unless the plane's drag prevented you seeing the extra speed the higher pitch prop SHOULD give.
You will see slightly faster accelleration on the ground, and better climb with the lower pitch prop, unless the aircraft has better than 1:1 power:weight.
You will be able to slow down for landings better with the lower pitch. (very important on light slow flying planes, especially 4*40 and most trainers)
The longer lower pitch prop will also help prevent overspeed in a dive. (nothing prevents overspeed if diving with full throttle)

case in point that airframe matters... my Fokker Dr1 flies faster with a 14X4 than with a 13X6... needs the extra pull at low speeds from the longer prop. Same max engine RPM both props.

beginner_1

Prop Chart For Two-Stroke Engines

Alternate Propellers Starting Prop
Engine Size

5.25 x 4, 5.5 x 4, 6 x 3.5, 6 x4 , 7 x 3 6 x 3
.049

7 x 3, 7 x 4.5, 7 x 5 7 x 4
.09

8 x 5, 8 x 6, 9 x 4 8 x 4
.15

8 x 5, 8 x 6, 9 x 5 9 x 4
.19 - .25

9 x 7, 9.5 x 6, 10 x 5 9 x 6
.20 - .30

9 x 7, 10 x 5, 11 x 4 10 x 6
.35 - .36

9 x 8, 11 x 5 10 x 6
.40

10 x 6, 11 x 5, 11 x 6, 12 x 4 10 x 7
.45

10 x 8, 11 x 7, 12 x 4, 12 x 5 11 x 6
.50

11 x 7.5, 11 x 7.75, 11 x 8, 12 x 6 11 x 7
.60 - .61

11 x 8, 12 x 8, 13 x 6, 14 x 4 12 x 6
.70

12 x 8, 14 x 4, 14 x 5 13 x 6
.78 - .80

13 x 8, 15 x 6, 16 x 5 14 x 6
.90 - .91

15 x 8, 18 x 5 16 x 6
1.08

16 x 10, 18 x 5, 18 x 6 16 x 8
1.20

18 x 8, 20 x 6 18 x 6
1.50

18 x 10, 20 x 6, 20 x 8, 22 x 6 18 x 8
1.80

18 x 10, 20 x 6, 20 x 10, 22 x 6 20 x 8
2.00

here is a chat i hope it help every one.