Worth the Weight?

[3D-Seth]

Hey guys,
I got to thinking today about IMAC. In IMAC, we use 3 bladed props to even out our uplines and downlines (with quieting the motors). Couldnt you use this idea on an F3P airframe to help slow the downlines? I know you would be adding extra weight, but would it be worth it?

If it was, what size 3 blade would I use for an Axi 2204/54 and a 5-6oz airframe?

Thanks guys!!

Seth Arnold

[3D-Seth]

I also got to thinking, the extra weight would also pull the plane down faster . . . . what do you guys think??

[3D-Seth]

Also, you could have the brake on and stop the prop to create more drag too right? IDK just askin questions . . .

[Matchless]

Seth, about 3 revisions back, there is a downline braking functionality in the Castle software. I ran it for a while with 2 blade props and really did not see much effect. I am assuming others saw the same so they pulled it. I never had the opportunity to try it with a 3 blader though.

So far, my search for 3 blade props in this size has turned up little that would be of any use to us.... (all junk)

[Wayne]

Seth,

I like your way of thinking..


You dont want the prop to stop if your looking for braking.
The disk of a spinning propeller has a ton of drag. (Good)
If it stops, that drag goes away.

I use just enough brake to keep the prop turning while inflight but not enough for it to be producing any thrust.

[Matchless]

	Quote:
	I use just enough brake to keep the prop turning while inflight but not enough for it to be producing any thrust.

That sounds similar to what I was trying. I would run anywhere between 10% and 50% braking factor.... Maybe I need to go back and try it some more...

[TonyThomasian]

So how much more weight would it add? LOL

[EddieWeeks]

I have made a lot of props in the last few month and I think to increase downline
breaking, get a wider prop with less pitch and keep the large dia.

This type of prop will have less slip and will accelerate the plane faster and
decelerate it also faster... Top end will suffer though..

Just a guess

Eddie Weeks

[OverTemp]

I thought 3-bladers reduced downline braking Maybe I'm wrong, but I've always worked under that assumption... that's why I fly 2-bladers on gassers (plus more thrust in a 2-blade).

I think what you really want to do is keep the disc area as large as possible... i.e. a large low-pitch 2-bladers, and keep it spinning below the point where it produces thrust. I don't use the brake on my ESC at all... I don't like it.

A 3-blade prop will hurt your 3D performance... you will lose a large percentage of your slipstream over the rudder/elevator/aileron. If you have to go from 10" 2-blade to an 8" 3-blade you will have 64% of the slipstream area. Going from a 9" to blade to an 8" 3-blade gives you 79% of the 9" slipstream. 10" to 9" = 81% of the slipstream. Numbers to think about.

All that being said, try it if you can and let us know how it works! Cheap experiment!

[Matchless]

	Quote:
	A 3-blade prop will hurt your 3D performance... you will lose a large percentage of your slipstream over the rudder/elevator/aileron. If you have to go from 10" 2-blade to an 8" 3-blade you will have 64% of the slipstream area. Going from a 9" to blade to an 8" 3-blade gives you 79% of the 9" slipstream. 10" to 9" = 81% of the slipstream. Numbers to think about.

Per the original poster, this is for F3P rather than 3D.

[SargeNZ]

Wide blades maybe all good, but all those that are running GWS HD props for their better efficiency are going to be faced with a problem. IMO there are better ways to provide braking than by using the prop, eg perforations on control surfaces and drag plates.

Has anyone TESTED the change in drag of a stationary vs braked vs freewheeling prop? You might get results that are not expected. I am talking about a controlled bench test rather than an in-flight test.

[Edge 540]

Everything has been tested by somebody. lol Probably not at these Re though.