Erickson6111

The stock propellor on my Mini App. S broke when I crash landed in tall grass, so I need a new one. Ive convinced myself that a 3 or even 4 blade would be ideal, in allowing takeoffs in taller grass and small waves at the lake.

Does anyone know of a compatible multi-blade prop for a 26oz foam plane at approx 150Watt?

​​​​​Or is there any issues that I need to be aware of?

Erickson6111

The slightly larger prop on my brothers super cub brushes the water when he's got floats on, even with calm water.

Erickson6111

Also my stock prop was 8.25" x 5.5 pitch

DGrant

My Feedback: (4)

Not sure on the prop really.. with an Apprentice... but I can say that if you're needing some ground clearance, you might look into bigger wheels. When you start switch props on an E-plane, you're getting into an area that you might need or want check your amperage before just taking it up. I would imagine that plane is pulling about 15-20 amps with a 11.1v Lipo.. which does put you at about 150 watts... maybe a bit more I'd bet.

See if you can find a moto-calc link somewhere, maybe even on this site that will give you some insight as to how to prop the plane... It's either that, or get yourself an amperage meter and check it yourself (not a bad idea at all really if you're going to be flying alot).. If you know the formula's and parameters you can safely make good decisions on your props, batteries, speed controls,etc...

What you're actually quoting at 150 watts says the motor/prop is only pulling 13.5 amps at 11.1v. That seems a tad low... I'm not saying it's wrong.. but I'm wondering how you arrived at 150 watts... to determine what/if you can go to a 3 blade without smoking your ESC or battery... The best way though is to probably drop a few bucks on a prop that you think will come close... It might be tough to find one... as the plane is specced with an 8.25x5.5 prop... If you can find a 7" 3blade prop... or even a 6" 3blade you'd be in the ball park to safely test your amperage... I'd bet a 6x5 3blade prop would be near what you need.... just a quick analysis here... but that's about what I'd start with and see where the amperage is.

The formula for figuring your watts is: Volts x Amps = Watts. ,,, but in my opinion the amps are the elephant in the room here.. I see the stock plane has a 1300 20c Lipo... so you're good up to about 25-26 amps there... the ESC though is only rated 18 amps... so if you prop it up too much.. that ESC will get very hot.. and that will create a problem.

I might even suggest keep your plane in top stock form and keep practicing with it... as you will eventually get into bigger faster planes.. These planes do fly very well. I hope this all makes sense here... and I'm sure there's more to it.. but this is it in a nutshell. Good luck with it.

Erickson6111

I am completely new to this whole thing. But after getting terrible durability out of my stock prop (3 landings in tall grass) I am looking for something different. Very little info on the subject it seems. Id love to land & take off with the plane, but it struggles even on mowed lawn, and the gravel road isn't much better.

DGrant

My Feedback: (4)

Try bigger wheels... and shorter grass. Not sure what you mean when you say you're "looking for something different" ..? A smoother surface will certainly help... but if a prop strikes that, it will break much quicker pn hard surface then on grass.. I guarantee that. Is it the take-offs that are the prob, or the landings?... Take-offs you have to run the motor up, so the prop is spinning fast of course, whereas landings are usually just glided in... and shouldn't be a problem. I'm betting these are thinner props being on a small electric plane.

When you say it struggles though... It sounds like you're trying to fly it off a surface that is just too much for the plane... The rougher the surface, the larger the plane needs to be...or other measures are needed.. which I'm sure is why you posted the thread..

If you have a local hobby shop, maybe they can offer suggestions, or have different props to suggest too. You asked if there were any issues you should be aware of... which is why I replied with a bit of info on the amperage draw vs. a larger/different prop... Unfortunately too... props are, and can be a part of the learning curve... and some people buy a half dozen at a time, and eventually learn too. The Apprentice series really is a decent set-up to learn with. Good luck with it

Erickson6111

The lawn is smoothe enough, but I don't wanna have to bring the lawn mower with me every time I take off. Brothers super cub trail dragger can do it, but my tricycle is less clearance. I bought taller and softer tires, but the legs are too short to account for the extra width of the tires. So I gotta drill out the centers and cut a 1/8th inch off the tires to make them skinnier.

Erickson6111

I want to get away from the stock prop because that broke with no real reason. I have a 4 blade 7"x5.4 pitch coming in the mail. Nearest hobby shop is 200 miles away, and they don't seem knowledgeable or prudent in returning phone calls.

I was hoping that a 20amp 740kv motor would be ok with my 18A. ESC. But replacing a stock motor of 18Amp 1300 kv. Aaaand the new motor is a same 28mm size, same company, different mounting holes

: P

j.duncker

My Feedback: (2)

A two blade prop is more efficient than a 3 or 4 blade one.

Yes a 4 blade will allow for slightly reduced diameter which helps with ground clearance on take off.

Erickson6111

I found a post saying that a 4 blade still needs to be 87% the diameter of the 2 blade it replaces. That is horribly inefficient, so im really hoping that is true

jester_s1

I think you are overthinking this. You don't need to change motors. To use a 3 blade prop, just go down by 1 inch and keep the same pitch and brand. A watt meter is a good tool to have when you want to experiment as it will tell you exactly how much power you are using instead of guessing and hoping for the best.

As for you takeoffs troubles, small planes don't deal well with grass. That's a weakness you just have to accept when you choose to fly an electric park flyer instead of a traditional .40-.60 size trainer.

Erickson6111

well, I am changing motors because the original died in 25 min flight time, and Hobby Horizons customer service takes too long.

Also, Hobby Horizon FMMProp039 7x5.4-4blade is actually a 7.5x4-4blade. They spelled it wrong on their website...

: P

Im never gonna spend money on Hobby Horizon products again

jester_s1

So you are going from a 1300 to a 740kv motor? It isn't going to work. You won't have enough RPM to fly your plane. You could go to a much bigger prop and possibly make it work, but it will never work well. If you had asked on the forum before buying a new motor we could have helped you out with picking the right one.

Erickson6111

I assumed that slower motor + more blades = same thing essentially.

But my 4 blade props are actually super skinny, so they aren't turning fast enough with the 740kv.

Hobby horizon has sent me a new 1300kv motor also, but I broke 2 of these parkzone propellors today, and I want to find a different brand.

Ideally, I want to find myself a 6.5"x5.5" with blades approx 3/4" width.

​​​​​​​My current 7.5x4-4blades are ok performance with the 1300, but they're junk. Tried to take off in grass that was a bit taller and snapped 2 blades off.

Does anyone have suggestions?

Steve Collins

My Feedback: (8)

Please don't take this the wrong way as in all seriousness, I hope you will follow solid advice.

First, don't try and re-engineer a mini apprentice. There is nothing wrong with the stock setup. The motor failing that soon sounds like a fluke to me. I have used and continue to use the e-flite brand of motors from Horizon Hobbies with no failures with hundreds if not thousands of flights. Do yourself a favor and use the replacement motor they sent you. One easy way to get more power out of the stock motor setup is to use a battery with a much higher "C" rating.Lots of beginning fliers in my local club use the Apprentice and I have witnessed a lot of punishing landings and some really ugly takeoffs that should have never left the ground but I have not seen the props breaking as you have in your experience.

Second, I agree that sometimes the stock propellers are not as sturdy as we would like them to be. You are going to experience a bunch of grief and frustration trying 3 and 4 blade props on that plane. My recommendation is to find an APC prop of the same or similar diameter and pitch as the stock prop. These are far superior props to most of the black plastic ones that come with a lot of the small arfs.

With this small a plane, you are going to have issues with it trying to fly off of grass. It really needs to have a hard surface. Surely you can find a place somewhere in your area.

aspeed

Motor loading aside, I would keep away from 3 and 4 blade props, as they are inefficient. I like softer more flexible props. On the old glow motors we could stick them into the ground at full speed, and bend them back and keep flying. Some indoor leckies I had were bad, like my Sukoi. I just put a similar more flexible one on. No probs. Just don't give it more load, or the battery, motor or speed control could overheat, and you will get shorter flights too.

jester_s1

If you are breaking props, you are either taking off or landing wrong or you are trying to fly off of a surface that your plane simply can't handle. A broken prop is essentially a crash. You wouldn't build your plane heavier and stronger to help it survive nose in to the concrete crashes, so don't try to buy more durable props to help them survive misuse.

If you broke a prop on your takeoff roll because the grass was too tall, then you are trying to fly in way too rough an area. It will never work. Look for a smooth surface to take off on, preferably something paved but well maintained park grass will work with wheels on the big side.

And I'll second what others have said- don't try to re-engineer the Apprentice. It's darn near perfect out of the box, so adjust what you are doing to work with it.