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What a difference a prop can make

Arcfyre

Well-known member
#1
Ok, so I've been scratch building FT designs for exactly a year now. It's been one heck of a ride, and I've learned a huge amount about this hobby.

I've had a love/hate relationship with the simple cub since day 1. My first ever thread on this forum was about my cub. Check it out here if you're interested. Long story short, it was ridiculously overweight, with an oversized battery and prop, made of the wrong material and built as a 3 channel. Anyone that knows about the cub knew that this thing had zero chance of flying like the one in the build video. Anyway it didn't last more than a few flights before it was destroyed.

I didn't let it get me down. I got a speed build kit for a Storch and a simple soarer, built my flying skills for several months, and after going through a few mini mustangs and discovering a love for flying wings, I circled back to a simple cub.

I had learned a lot by now, especially about scratch building. I had the proper DTFB material, and was much much cleaner with my cutting out. I was also much more careful with gluing. I wouldn't call myself a professional builder by any means, but definitely proficient. Anyway, with my level of skill at the time, I felt confident to try the cub again.

I built a nice clean airframe and wired it up as a 4 channel. I used a much more appropriate motor, and a much smaller 1000mah battery to keep weight down. It was adequately powered and well within specs for AUW. It should fly just fine, right?

Well, it didn't. Even with a stabilized RX I just couldn't keep the stupid thing in the air. I was at the point where I could thread needles with my Storch or Versa wing, but I couldn't fly the cub? A trainer? Really? The fault must lie with the airplane.

After a particularly nasty landing which removed the landing gear and most of the nose, I scrapped that airframe and sat down to do some reading. I finally discovered that I wasn't the only one who had issues with the cub. I want to give credit to @Hai-Lee for finally mentioning that the wing incidence angle needed an adjustment before the plane would fly. I steeled my nerves and sat down to build another simple cub.

I built this one as light as I possibly could. I modified the wing incidence angle and even stretched the wingspan a bit to give it more lift. I powered it with a tiny little lightweight motor and used my smallest battery possible. I used a "soft" 8x4.5 slowfly prop and went for a maiden flight.

The thing barely flew with that power setup. No balls whatsoever. Totally unable to cope with any wind. Another disappointing cub. Part of the problem was that at any power setting above 60%, the prop would overspin and flatten out, basically producing no thrust at all. This basically made the plane unflyable, UNTIL yesterday I put an APC 8x3.8 slowfly prop on.

Oh my word, what a beautiful flying airplane! Just about silent, uses barely any power, and has a great rate of climb if it needs it. Lands in a few feet and can fly at walking speed. Can handle a little wind too. I'm blown away. Finally, I have a cub that flies!

It's only taken me a year, but I finally have a simple cub that flies. I'm thrilled lol. I'm blown away the difference that the right prop can make to the flyability of an airplane.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#2
Ok, so I've been scratch building FT designs for exactly a year now. It's been one heck of a ride, and I've learned a huge amount about this hobby.

I've had a love/hate relationship with the simple cub since day 1. My first ever thread on this forum was about my cub. Check it out here if you're interested. Long story short, it was ridiculously overweight, with an oversized battery and prop, made of the wrong material and built as a 3 channel. Anyone that knows about the cub knew that this thing had zero chance of flying like the one in the build video. Anyway it didn't last more than a few flights before it was destroyed.

I didn't let it get me down. I got a speed build kit for a Storch and a simple soarer, built my flying skills for several months, and after going through a few mini mustangs and discovering a love for flying wings, I circled back to a simple cub.

I had learned a lot by now, especially about scratch building. I had the proper DTFB material, and was much much cleaner with my cutting out. I was also much more careful with gluing. I wouldn't call myself a professional builder by any means, but definitely proficient. Anyway, with my level of skill at the time, I felt confident to try the cub again.

I built a nice clean airframe and wired it up as a 4 channel. I used a much more appropriate motor, and a much smaller 1000mah battery to keep weight down. It was adequately powered and well within specs for AUW. It should fly just fine, right?

Well, it didn't. Even with a stabilized RX I just couldn't keep the stupid thing in the air. I was at the point where I could thread needles with my Storch or Versa wing, but I couldn't fly the cub? A trainer? Really? The fault must lie with the airplane.

After a particularly nasty landing which removed the landing gear and most of the nose, I scrapped that airframe and sat down to do some reading. I finally discovered that I wasn't the only one who had issues with the cub. I want to give credit to @Hai-Lee for finally mentioning that the wing incidence angle needed an adjustment before the plane would fly. I steeled my nerves and sat down to build another simple cub.

I built this one as light as I possibly could. I modified the wing incidence angle and even stretched the wingspan a bit to give it more lift. I powered it with a tiny little lightweight motor and used my smallest battery possible. I used a "soft" 8x4.5 slowfly prop and went for a maiden flight.

The thing barely flew with that power setup. No balls whatsoever. Totally unable to cope with any wind. Another disappointing cub. Part of the problem was that at any power setting above 60%, the prop would overspin and flatten out, basically producing no thrust at all. This basically made the plane unflyable, UNTIL yesterday I put an APC 8x3.8 slowfly prop on.

Oh my word, what a beautiful flying airplane! Just about silent, uses barely any power, and has a great rate of climb if it needs it. Lands in a few feet and can fly at walking speed. Can handle a little wind too. I'm blown away. Finally, I have a cub that flies!

It's only taken me a year, but I finally have a simple cub that flies. I'm thrilled lol. I'm blown away the difference that the right prop can make to the flyability of an airplane.
You are one of the few to have the patience to work through the problems and set up the Simple cub the way it really performs!

It is such a sweet handling bird and could almost be considered as calm enough to use as a trainer or the like. Unfortunately the landfill sites have a number of failed cubs that just were not built or setup properly!

Your comment on the value of the prop selection is golden and a lesson all newbies need to heed. Many a good plane has been lost due to poor setup choices! Your persistence is admirable and should be a lesson for all.

Actually now you know the issues in tailoring the performance to the design you could build and setup almost any of the FT offerings without a worry and have a sweet performing bird almost every time!

Well done!

Have fun!
 

Arcfyre

Well-known member
#3
Actually now you know the issues in tailoring the performance to the design you could build and setup almost any of the FT offerings without a worry and have a sweet performing bird almost every time!

Well done!

Have fun!
Yeah I've been at that point for a while with all of my models, with the exception of the cub. I'm glad I finally got it figured out
 

mrjdstewart

Well-known member
#5
wow, i have built more simple cubs than i care to remember and all of them have flown. all of my students have built one as well and all of theirs have flown fine, both 3 and 4 channel. i have used c-packs, b-packs, and random motors i had sitting around. i have used everywhere from 8x4.5 to 10x4.5 props, all slow fly. most built from scratch using DTFB.

sorry to hear about your struggles but glad you stuck with it. the cub is one of my favorite airplanes for simple, basic flight. my fav is set up is a flaperon with a b-pack, w/ a 3s-1300, 20A esc, and 10x4.5 sf. i can grease touch and goes all day long, even tried water skiing touch down once. :p

not my most exciting video but...


having the correct prop is very important, i have seen many SF props flatten due to too much power. i do believe that the understanding of motor/prop/esc/battery combos is the biggest learning curve in the hobby. build procedures don't change, but weight, performance, and desire vary by each plane. that is where things get interesting.

laters,

me :cool:
 

Arcfyre

Well-known member
#6
Nice flying, @mrjdstewart!
Im looking forward to my flying field opening in a few weeks so I can practice the same with my cub. The lawn I usually fly from after work is too long for a cub to handle it easily.
 

basslord1124

Well-known member
#8
That's awesome to hear. :) Honestly I have heard mixed reviews on the Simple Cub. I flew mine recently and I didn't have a great experience. But mine, at least the issue now, was my high rates weren't set up correctly. Here's the recent video I did of it:


Currently I'm running a 9x6 prop with a 1600Mah 3S. When I did have control I don't think it flew terribly or anything, of course you all may see something I'm not. It was in 5-6Mph winds too.
 

mayan

Well-known member
#9
That's awesome to hear. :) Honestly I have heard mixed reviews on the Simple Cub. I flew mine recently and I didn't have a great experience. But mine, at least the issue now, was my high rates weren't set up correctly. Here's the recent video I did of it:


Currently I'm running a 9x6 prop with a 1600Mah 3S. When I did have control I don't think it flew terribly or anything, of course you all may see something I'm not. It was in 5-6Mph winds too.
@basslord1124 don't kill yourself :), we need you around.
 

Sero

New member
#16
I went through some frustrations with my Cub, Seemed to get past them mostly by getting rid of the dihedral and adding support to the tail control rods. I'm using a c-pack with 10x4.5 APC and 1300 3 cell. I don't care for it with a 2200, seems to weigh it down too much.
I'd like to know what set-up people use when using floats, cant imagine it would fly well with that extra weight.
 

Arcfyre

Well-known member
#19
I went through some frustrations with my Cub, Seemed to get past them mostly by getting rid of the dihedral and adding support to the tail control rods. I'm using a c-pack with 10x4.5 APC and 1300 3 cell. I don't care for it with a 2200, seems to weigh it down too much.
I'd like to know what set-up people use when using floats, cant imagine it would fly well with that extra weight.
I tried a cub on floats for about 10 minutes. It was a no go. If you'd like to try floats, use the simple scout. I've had great success with that model.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#20
I tried a cub on floats for about 10 minutes. It was a no go. If you'd like to try floats, use the simple scout. I've had great success with that model.
To get the cub to fly sweet and take off/land just as sweet you need to firstly consider the extra drag of the floats and so a bit more thrust is highly desirable.
Next there is the weight to consider and so you may need a slight bit more main wing incidence, (not too much though(.

And finally the floats should have a "Step" to help break surface tension and allow the plane to rise up on the "Plane" when running at speed over the water. The step is the point of contact with the ground in the same manner that wheels are the point of contact with the ground for a normal ground take off. The Step should be slightly FORWARD of the planes CG for a nice take off.

The biggest issue with flying off of floats is that they are fitted incorrectly and often too far to the rear. In the extreme if the step is too far aft the plane can somersault nose first into the water on landing or even on take off.

Just what I was taught!

Have fun!