2 blade vs 3 blade props

[doctormike]

I'm back. Here is the combo I am using for my "test". Art-Tech Pitts, 9x6 3 blade prop, 35a ESC, 410 kv 480 motor, 1300 mah 3s battery @12.4 v.I used this battery for the test only. For flying, at least an 1800 mah should be used. The static test results are, 10 min. @ 1/2 throttle 11.4 v remaining. With this power setup 1/2 throttle is amazing. I haven't flown it yet (weather) but, a static run at full throttle is actually scary! So, my question for you 2 blade proponents is...If 3 blade props are less efficient, why do racing, aerobatic, and ww2 fighters use 3 or even 4 blade props? In my never so humble opinion, the blades are not affected by the previous blades turbulence when the plane is flying, because the blades have undisturbed air to bite into as the plane moves forward. I believe 3 blade props are fine if the correct power combo is used. besides, they look sooooo cool! I'll be back after I fly it. The Doctor

[WintrSol]

Re: 2 blade vs 3 blade props

The primary reason warbirds used 3- or 4-blade props was for ground clearance; the engines were powerful enough that a 2-blade prop large enough to use that power would possibly strike the deck. That's the same reason I use a 3-blade prop in my T28; with oleo gear, the nose wheel compresses enough that a 2-blade prop would get shorter, real fast. BTW, have you measured the current/power drawn by that setup? You don't want the magic smoke to come out!

[doctormike]

Re: 2 blade vs 3 blade props

The magic smoke hasn't come out. With more high rpm runs ,motor, esc and battery are not even warm. Yeah,I know about the ground clearance thing. 3 blade props just look too cool to not use them. Again it's a matter of using them correctly. Thanks for your reply. The Doctor

[FLY BOY]

Re: 2 blade vs 3 blade props

I have played around with the whole prop thing myself. I have done some good testing using 2, 3, and 4 blade props side by side. In my own test results I found that for all out speed the 2 blade worked the best in most cases, pending your set up, But when it came time to land, Having the least amount of drag, the 2 blade came in hot and took a longer approach to slow. I love the scale looks of 3, and 4 blade props myself, and where I found the 3, and 4 blade prop to excel was in a climb. They seem to climb further when going vertical. Blade change basics I found are as follows. Lose and inch, go up 1 pitch. Lose a blade, go up in pitch x 2. Example= I was using the stock 11x6x3 blade on my T28. Wanted more speed but when I went up in blade size, She ran hot. So I downed size the blade length and went up 2 in pitch and found I got more speed and performance from a 10x8x2 blade. I had one plane go from a 11x6x3, into a 10x10x2 with no heating up, Quality of your electronics help out with heat, and so does proper cooling. My favorite change was in my F4U Corsair. Came with a 13x6x3 blade, In search for more speed and performance, It ended up with a 12x12x2 blade and was out standing with no heating up. I bet I gained 10+ mph, and out performed a bad to the bone P51 Mustang, Mustang guy was upset. My Corsair knocked the king off his throne that day, all in good fun of course. We like to play with the war birds at our field. Anyways I hope this helps some, Good luck and happy flying. P.S always make small changes in props sizes keeping a feel on batt pack and esc for heat. they will heat up when going the wrong direction in prop size. This method works if u don't have the proper meters.

[WintrSol]

Re: 2 blade vs 3 blade props

Guys going for all-out speed use a 1-blade prop; takes forever to take off, but once at speed, it will out-fly any other prop. These have to be hand-made, of course.

[Sweep]

Re: 2 blade vs 3 blade props

I have just started getting into the hobby and am currently flying a Freewing Seagull. Great starter plane, just bought new wings due to those few first flight crashes, but am looking to upgrade to the FMS Cub. I think it is a logical first step and I like the look of the plane but I want to add a 3 blade prop.

So if I wanted to put a three blade prop on a FMS Cub (Maybe a more super Cub look), what would the goal be for pitch and size with recommended electronics (estimate?). I was looking at 3 bladed props in the Motion prop section and figured that I would want to get a prop for a similar size aircraft but obviously the pitch will be different?

A bit off topic but what would be the goto upgrade for ESC/Motor with an 11.1V 2200mah 30C battery? Is stock really quality enough? And is it worth upgrading servos for a plane like this?

I know some of these questions are a bit off topic, sorry for that, just lots of questions!

[WintrSol]

Re: 2 blade vs 3 blade props

The rule of thumb for 2 to 3 blades is, reduce diameter by one inch, with the same, or next number up in pitch. You should use that as a starting point, and use a watt meter to verify the power, since details of blade design vary a lot, and effect the power and thrust. For example, I swapped the stock, 3-blade prop on my T28 with a MAS one of the same diameter and pitch, and power and thrust both went up by about 10%. I measure power with a watt meter, and thrust with a digital scale securely fastened to the tail. I also replaced the 12x9 prop on my 182 with an 11x8.5x3, and the power and thrust were nearly the same, it just flew a tad slower than my friend's 182 with the stock setup. Looks cooler on the ground, though; on taxi or in the air, who can tell?

[stitch]

RE: 2 blade vs 3 blade props

i,m trying to find a 3 blade spinner to fit my dhc-2 beaver anyone know where i can find one same as stock but 3 blade? i thought i read somewhere in here where a guy had 3 blade spinner on his. can,t seem to find it now! thanks!

[doctormike]

RE: 2 blade vs 3 blade props

Stitch, Dubro sells 3 blade spinners. Combined with a Windsor prop, it really looks and flies great! While your at it, buy a Dubro prop balancer. Balance your props and spinners!!! It is very easy to trim the spinner to fit the prop. I use a Dremel with a small sanding drum. The Doctor

[tchap]

RE: 2 blade vs 3 blade props

I just purchased a HK skipper and want to change out the stock prop. The way the plane is set up limits you on prop length so I was thinking of a three blade for more bite. After doing some reading on other forums I have heard of guys taking a larger prop and cutting it down in length. Was wondering if anybody has tried this? Do they do this for the extra width?

[WintrSol]

RE: 2 blade vs 3 blade props

I just purchased a HK skipper and want to change out the stock prop. The way the plane is set up limits you on prop length so I was thinking of a three blade for more bite. After doing some reading on other forums I have heard of guys taking a larger prop and cutting it down in length. Was wondering if anybody has tried this? Do they do this for the extra width?

The fewer the blades, the more efficient a prop is, IOW more thrust from the same amount of power. When they started putting huge engines in aircraft, and ground clearance was not enough, they also put more blades on the prop to use all that power. Adding blades to a prop, while leaving the diameter and pitch the same, greatly increases the power a prop will pull from the power system, so, before changing your power system, I recommend you get a watt meter and measure what you have. If your current prop pushes your motor or ESC within 20% of the maximum they are rated, going to three blades will burn it up. Generally, when increasing the power output, you have to put in a higher-rated ESC, and sometimes motor, too.

[doctormike]

RE: 2 blade vs 3 blade props

tchap, I have trimmed prop tips with good results, but only because I needed that size prop. I just leave the tips square and slightly round the corners. If you do this, BE PRECISE and balance! If you will examine the twist in a prop, you will see less pitch in the tip. You don't want a lot of twist in the tip, so, never take off too much.  When going from 2 blade to 3 blade, go with 1' shorter and 1' higher in pitch. Good luck, The Doctor , P.S. wintrsol is so correct. However, Almost any engine upgrade, especially in full scale planes, includes a 3 blade prop, even when a change in ground clearance is not needed. Thanks, The Doctor

[WintrSol]

RE: 2 blade vs 3 blade props

Yes, I missed answering the length reduction question. I have a Cherokee arrow, and flew it with a 13x8 prop; it need just a bit more speed, but they don't make 13x10 props, at least, none I could find, so I cut a 14x10, and balanced it. You end up with a bit more than a 10" pitch that way, because of the varying twist, but it gave me that extra bit of power, without reducing ground clearance.