The rule of a thumb is that the intake:exhaust area ratio should be at least 1:3. With this ratio some kind of a sub pressure is created at the intake and the air is sucked in rather than pushed into the fuse, which is much better.

So you can easily calculate what ever is the area of the ring created between the spinner and the cowl, multiply that by 3 and that should be the opening of the exhaust.

Just to warn you, every time I do this I get shocked how big the exhaust area should be, but that is how it works.  If the exhaust turns out to be too big it is much better to reduce the area of the intake rather than not have the exhaust big enough!

Velco

I guess it is Rimfire 65cc right?

Well it shows that 22x14 would be ideal but such prop doesn't exist. So it is either 21x14 or 22x12. You should try both and see which one suits you. My choice would be 21x14 because it gives more reserve thrust at cruising speed with less, but enough static. Or, make the first flights on 22x12 and move on to 21x14.

I can explain some other time in more detail some theory and practice how prop choice differs from gas to electric.

Velco

quote:

ORIGINAL: Velco

I guess it is Rimfire 65cc right?

Well it shows that 22x14 would be ideal but such prop doesn't exist. So it is either 21x14 or 22x12. You should try both and see which one suits you. My choice would be 21x14 because it gives more reserve thrust at cruising speed with less, but enough static. Or, make the first flights on 22x12 and move on to 21x14.

I can explain some other time in more detail some theory and practice how prop choice differs from gas to electric.

 

Velco

I searched the net before posting and yes the only 22x14 available was from HK, but some of my friends have tried those props some 2 years ago and they were really crap, thats why I did not take them into consideration. But now what kehlog is saying sounds very interesting, probably some new version.  kahlog, can you please post some of your results, I am really curios about Turnigy Cherry wood props now and will definitively give them a try.

I did  a lot of experimenting with props including APC-E, TGS from HK and Turnigy Light Elelctric. I ended up using practically Turnigy LE on all of my planes. I have only recently purchased XOAR 20x13 and 19x15 as well as PT carbon 20x13 for my F3A bird to test this year.

At Scorpion site there are motor tables where APC-E and XOAR are compared and XOAR results compare almost identical to my findings about Turnigy LE. I even believed that they are the same thing, but they are not. One things is almost certain, they are produced at the same place.

Velco


Edit: I went to XOAR website to check once again and  XOAR PJN Beecwood series do look identical to Turnigy Light Electric. These props can also be found under various brands all around Europe. The XOAR props I have are F3A props and they are shaped differently, slightly more curvy for less noise.

Thanks for the info, I will definitively give them a try now. Unfortunately there is no 15x10 available that I am using on Sebart MissWind50 but there is 17x10 that I am using on Wind110E. I have E-logger so it will be easy to compare.

After talking a bit to Mirce I figured out that 50% more static from flying weight is really not necessary so I have come up with one more interesting solution for Rim  65cc on 12S (or any other motor with kV around 170 like AXI 5345/18)  which is also more scale especially on Dora and it is Biela 3 blade 20x14. Would really look nice painted in black .

Velco

quote:

ORIGINAL: Velco

After talking a bit to Mirce I figured out that 50% more static from flying weight is really not necessary so I have come up with one more interesting solution for Rim  65cc on 12S (or any other motor with kV around 170 like AXI 5345/18)  which is also more scale especially on Dora and it is Biela 3 blade 20x14. Would really look nice painted in black.

quote:

ORIGINAL: Corsair 29

quote:

ORIGINAL: Velco

After talking a bit to Mirce I figured out that 50% more static from flying weight is really not necessary so I have come up with one more interesting solution for Rim  65cc on 12S (or any other motor with kV around 170 like AXI 5345/18)  which is also more scale especially on Dora and it is Biela 3 blade 20x14. Would really look nice painted in black.

This is also quite interesting as well. Does ecalc show you what the current draw is on the 3 bladed prop at 100% throttle verses a 2 bladed prop? Obviously there will be more current draw for more load, which may require a larger battery pack(mah).

quote:

ORIGINAL: Velco
.

As there is no good Do 335 thread (at least I could not find it) I have some interesting options for that modell too as I consider the suggested  2 Eflite160 on 10S  and 20x10 completely unnecessary and the plane sounds very bad with those props spinning at such high revs.

A question from my side, which way to go, Benedini or Model Sound Inc way? Some pro and contra from the filed would be nice.

Velco

quote:

ORIGINAL: kahloq

quote:

ORIGINAL: Velco
.

As there is no good Do 335 thread (at least I could not find it) I have some interesting options for that modell too as I consider the suggested  2 Eflite160 on 10S  and 20x10 completely unnecessary and the plane sounds very bad with those props spinning at such high revs.

A question from my side, which way to go, Benedini or Model Sound Inc way? Some pro and contra from the filed would be nice.

Velco

Ummm.... there is definitely a good esm do 335 thread headed up by Fockewulf37. In it there are a few examples on electric versions and there has been one done with two power 160's. But..yea its quite overpowered and could be flown with power 60s or power 90s with smaller props. A bendini sound system would definitely make it sound nice, but ive no experience with Model Sound Inc.

Thread here:
http://www.rcuniverse.com/forum/m_10204139/mpage_1/key_/tm.htm

quote:

ORIGINAL: Velco

I searched the net before posting and yes the only 22x14 available was from HK, but some of my friends have tried those props some 2 years ago and they were really crap, thats why I did not take them into consideration. But now what kehlog is saying sounds very interesting, probably some new version.  kahlog, can you please post some of your results, I am really curios about Turnigy Cherry wood props now and will definitively give them a try.

I did  a lot of experimenting with props including APC-E, TGS from HK and Turnigy Light Elelctric. I ended up using practically Turnigy LE on all of my planes. I have only recently purchased XOAR 20x13 and 19x15 as well as PT carbon 20x13 for my F3A bird to test this year.

At Scorpion site there are motor tables where APC-E and XOAR are compared and XOAR results compare almost identical to my findings about Turnigy LE. I even believed that they are the same thing, but they are not. One things is almost certain, they are produced at the same place.

Velco


Edit: I went to XOAR website to check once again and  XOAR PJN Beecwood series do look identical to Turnigy Light Electric. These props can also be found under various brands all around Europe. The XOAR props I have are F3A props and they are shaped differently, slightly more curvy for less noise.