swap a 4 blade prop for a 3 or 2 blade prop?
12-14-2021, 10:22 AM
#1
Member
Thread Starter
Join Date: Aug 2005
Posts: 304
swap a 4 blade prop for a 3 or 2 blade prop?
a plane with a 4 blade E-flite prop 4 Blade, 10.5x8: and I want to swap it out for a 3 Blade or a 2 blade . so what are my size choices in length and pitch ? anyone know helps
12-14-2021, 12:15 PM
#2
Super Contributor
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 12,866
A 4 blader is purely a scale looking item and will not actually give better performance - in fact it could lead to less - due to blade cavitation at high rpm. On ground - the thrust will suffer until model attains speed ...
Generally a 2 blade gives better performance - but of course doesn't look the part.
10.5x3.8 is a weird size and is hard to find a direct 2 / 3 blade replacement. I would suggest in 2 blade form either 11x4 or 10x5 ..... similar in 3 blade. See later post after Q caught the mistake !!
There's an old myth of up 1 / down 1 when changing blade count .... its generally ok ... but not actually correct. Pitch gives speed ... diameter gives thrust / torque ... so care needs to be taken not to compromise one or other.
Generally a 2 blade gives better performance - but of course doesn't look the part.
There's an old myth of up 1 / down 1 when changing blade count .... its generally ok ... but not actually correct. Pitch gives speed ... diameter gives thrust / torque ... so care needs to be taken not to compromise one or other.
Last edited by solentlife; 12-14-2021 at 07:32 PM.
12-14-2021, 02:07 PM
#3
homo ludens modelisticus
Join Date: Jul 2005
Location: near Nijmegen, Nederland
Posts: 1,433
Keep in mind that a plane propeller cannot cavitate, it needs a liquid to cavitate:
wikipedia: Cavitation.
Like a wing the propeller stalls:
wikipedia: Stall_(fluid_dynamics)
wikipedia: Cavitation.
Like a wing the propeller stalls:
wikipedia: Stall_(fluid_dynamics)
12-14-2021, 02:25 PM
#4
Super Contributor
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 12,866
Originally Posted by ron_van_sommeren
Keep in mind that a plane propeller cannot cavitate, it needs a liquid to cavitate:
wikipedia: Cavitation.
Like a wing the propeller stalls:
wikipedia: Stall_(fluid_dynamics)
wikipedia: Cavitation.
Like a wing the propeller stalls:
wikipedia: Stall_(fluid_dynamics)
Pedantics Ron ... the effect is similar. Prop stalls and thrust is lost.
12-14-2021, 04:02 PM
#6
homo ludens modelisticus
Join Date: Jul 2005
Location: near Nijmegen, Nederland
Posts: 1,433
Originally Posted by solentlife
Pedantics Ron ... the effect is similar. Prop stalls and thrust is lost.
Last edited by ron_van_sommeren; 12-14-2021 at 04:36 PM.
12-14-2021, 07:31 PM
#7
Super Contributor
Join Date: Oct 2010
Location: Ex UK Brit now in Latvia west coast - Ventspils
Posts: 12,866
Originally Posted by quorneng
Did not the OP say the 4 blade was a 10.5x8 (eight) not 3.8!
Surely the replacement should have at least an equal pitch. Say 12x9 two blade or 12x8 three blade.
Surely the replacement should have at least an equal pitch. Say 12x9 two blade or 12x8 three blade.
"10.5x8
I don't think it necessary to go up 2 in diameter as a 4 blader is not that efficient in my experience.
Thread
Thread Starter
Forum
Replies
Last Post
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
