irvine 53 prop selection

[old yorkie]

can anybody please help with the correct prop size for an irvine 53. the engine is going in a seagull decathlon with 68" wing span. looking for a scale speed rather than outright speed. any help would be appreciated.

mike.

[Stevo]

Hi Old Yorkie,

I'd start with an 12 x 6. That should give you a bit of torque, without the screemin' demons!

Edited By Stevo on 11/07/2014 18:41:55

[cymaz]

+1 for a 12x6

[old yorkie]

wow thanks for the quick reply stevo/cymaz, i have a spare apc 12x6 so will give it a go in the morning.

thanks again, mike.

[cymaz]

It surprised me what a difference a prop change makes on the flying characteristics of the plane. The props may be in the manufactures range and the engine ok but what a difference on climb rate slowing down to land etc.

[Former Member]

[This posting has been removed]

[Stevo]

Ur my kinda guy Petcy..

Indeed none of my aircraft are engineered to or have vertical performance... and fly not soley on the benefit of a screaming fan..

[cymaz]

I always try a few different props just " to see what happens".

Percy, that's what my flying instructor used to say to me " it's the wing that flies the blxxx plane!" (and at just over 80 now he still says it).

Edited By cymaz on 13/07/2014 08:29:58

[Stevo]

With me it's caution.

Big and fine to start with, so I can get pulled out of trouble should I need to.

I may change later, but given that I like my WW1 scale, and love flying low wing trainer types for basic aerobatics there doenst seem a lot of point. Perhaps I should!!

[old yorkie]

well saturdays test with the 12 x 6 did not happen thanks to a surprise visit from the grandkids !!!!!. will try if the rain stops here today. with regard to pitch,is the higher number a finer pitch?.is there somewhere on the forum that looks at props and the effects changes can make.

mike

[Bob Cotsford]

The pitch (second number in the prop spec eg 6" is the theoretical distance the prop will move forward in one revolution - think of a screw going into a piece of wood, the steeper the angle of the blades, the further it wants to travel in one rev. So smaller number = lower pitch = lower maximum speed and higher acceleration (like the gears in a car, low pitch = low gear).

On 46-52 2strokes I tend to go for 11*7 for faster models, 12*6 or 12*5 for slower models or fun-fly types.

For a fast Kwik-Fly 40 aerobatic model I use 11*7, for a Panic I'm running 12*5. Both get under 80dBa at 7M, the difference is in airspeed and acceleration.

[old yorkie]

today i finally managed to get flying and try the 12 x 6 prop and wow what a differance a small change makes . the plane feels nicer to fly, bags of torque when flying around on half throttle and the landings are so much slower. thanks for your help and advice.

mike

[cymaz]

[Jonathan M]

On 13/07/2014 at 11:29, Bob Cotsford said:

The pitch (second number in the prop spec eg 6"/CuteEditor_files/images/emwink.gif is the theoretical distance the prop will move forward in one revolution - think of a screw going into a piece of wood, the steeper the angle of the blades, the further it wants to travel in one rev. So smaller number = lower pitch = lower maximum speed and higher acceleration (like the gears in a car, low pitch = low gear).

On 46-52 2strokes I tend to go for 11*7 for faster models, 12*6 or 12*5 for slower models or fun-fly types.

For a fast Kwik-Fly 40 aerobatic model I use 11*7, for a Panic I'm running 12*5. Both get under 80dBa at 7M, the difference is in airspeed and acceleration.

 

[Picking up on a 10yr old thread... but the principles haven't aged!]

 

I've got a very nicely-running Irvine 46 in a good Irvine Tutor Mk1 I've just acquired for use as a club trainer.  The engine came with a Master Airscrew 12x5 which I assume is probably a very appropriate prop for this model's trainer-function?... big enough to give flywheel effect and keep noise down, and not too fast with a relatively fine pitch for low-to-medium speed flying and acceleration/deceleration?

 

By comparison I have an APC 12x6 on the Irvine 53 in my Gangster, which is perfect for that.

 

Also, more generally, is there any difference between MA and APC props?  Any reason why folks prefer one or the other?

 

 

[Andy Stephenson]

My opinion, Master Airscrew props are heavy and inefficient. APC props are designed using advanced computer software which didn't exist when MA props first came out and I don't believe they've changed since.

[Jonathan M]

Makes sense Andy... the Master Airscrew's shape certainly looks like it was inspired by the Wright Flyer!

 

It is also heavy, and when giving the Irvine 46 a brief test run (hand-flick started quickly) the whole airframe shook!  So out came the prop-balancer followed by 20 minutes with some heavy-duty files!

 

Methinks I'll order an APC 12x6 and 12x5 and see which suits the model best in actual flight.

 

Edited August 21 by Jonathan M

[GaryW]

7 hours ago, Andy Stephenson said:

My opinion, Master Airscrew props are heavy and inefficient. 

 

I disagree... I have both a Master Airscrew 14x7 and a Graupner 14x7 that I bought for my new Spitfire and when setting up the CofG I found the Graupner is the heavier prop... The Master Airscrew 14x7 being 58g,, while the Graupner 14x7 is 80g

Edited August 21 by GaryW

[GaryW]

Coincidently I just looked up the specs on an APC 14x7 to compare against the Master Aircrew & Graupner props I have and the APC 14x7 specs list the prop weight to be 2.72oz / 78g 

 

Ive also looked up a 12x6 Master Airscrew & APC 12x6 and again find the APC to be the heavier @ 1.62 /45g verses 36g for the Master Airscrew

so maybe APC are not that light a prop after all

Edited August 21 by GaryW

[Martin Harris - Moderator]

Master Airscrew props appear to be very efficient - at turning power into noise. ..

 

On numerous occasions at our club, models failing noise tests have passed after changing to APC propellers of the same size. 
 

However, in addition to their traditional square ended ranges, they do now have a range of “scimitar” props which I have no experience of - perhaps these are more efficient?

[PDB]

Have used both APC and Master Airscrew 11x7 props on an OS46 equipped trainer for a couple of years and cannot notice a difference.

 

I also balance new props before use and again not found any difference between the two makes.

[Andy Stephenson]

1 hour ago, Martin Harris - Moderator said:

Master Airscrew props appear to be very efficient - at turning power into noise.

I've had this problem too. Running a 13x6 MA prop on a Laser75 failed the standard noise test but changing to a MK prop cured the problem and gave better performance.

[Paul De Tourtoulon]

1 hour ago, Martin Harris - Moderator said:

Master Airscrew props appear to be very efficient - at turning power into noise. ..

That's why I love them on 2 strokes,,,

[Jonathan M]

Well I flew the Irvine Tutor/46 today (maiden session for me with this model) on three different props - the 12x5 Master Airscrew it came with, the 12x6 APC off my Gangster and an 11x7 APC from my collection.

 

The 12x5 MA was clearly much noisier than the  two APC props, and gave no discernible lower-gear advantage over the 12x6 APC which seemed the best of the three all-round.  I do need much clearer acceleration on the takeoff run of this fairly heavy model on our short patch (with every prop I tried the model just about lumbered into the air with a yank of up elevator just before the long grass!) so will order APC's 11x5 and 12x5 for the next round of tests.