3 blade props

[Olly Giles]

How do you select a 3 blade prop to directly replace a 2 blade prop. So if i am currently using a 16x10e prop what would be the 3 blade equivilant?

[John Privett]

You'll want to reduce the diameter but keep the pitch the same.

 

The rough "rule of thumb" was always to reduce the diameter by an inch - though that was in the days when a "typical" prop was 10 or 12 inches diameter, so on a 16" prop you may need to come down by more than an inch. I'd try a 15x10 or possibly a 14x10.

 

Presuming the "e" indicates you're flying electric then you should check with a wattmeter that the current is still within limits before flying.

 

If somebody has Motorcalc or similar it would be interesting to see what numbers it comes up with.

[Josip Vrandecic -Mes]

Graupner equivalent prop list (OS 70 4 stroke ) looks like this :

11-7'' (three blades) and 12,5-6'' (two blades).

note: OS and Graupner only .....it might be helpful...Cheers Jo

[laurent Muchacho]

Anyone got a tip or Technic to balance 3 blades prop?

 

I've got a balancer that I know how to use to balance 2 blades prop but found it difficult to balance 3 blades prop

 

Many thanks

[Former Member]

[This posting has been removed]

[laurent Muchacho]

If you buy graupner props I agree, you don't need to balance them but I do have some gws 3 blades that need balancing. Same with all Giantcod 3 blades prop I've received.

 

If you don't need to balance new prop your are lucky but only a few wood prop, master airscrew and Graupner are perfect out of the box but most other need balancing from my experienced.

 

On my e2k pylon plane I do have to precisely balance every prop even if the prop is balanced sometime the hob will be a bit unbalanced meaning the density of the nylon is denser on one side of the prop. This will not usually cause problem or even noticeable vibration on most plane but on the e2k 650W make you realise that each prop need to be perfect.

 

Please any tips on balancing 3 blades is welcome

 

Laurent

 

 

 

 

 

 

[laurent Muchacho]

There it is how to balance 3 blade prop

 

http://www.phprc.net/images/RC_Aero_-_3_Blade_Prop_Balancing_Technique.pdf

 

His technique work really for big prop but for small prop like tha gws7x3.5 3 blade if you scrap/sand from the heaviest until it balance with the lightest you will mainly scrap too much of the plastic on the blade making the blade more flexible and less efficient.

 

The the way I do it is has follow

1) follow each of the step described

2) found the lightest blade (1 dot blade) move (3 dots blade) to the top and add weight to number one until it balance with number 2

3) now you can scrap/sand out of number 3 until it balance with the 2 others

 

Hope that help. Please feel free to ask any question