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Apr 14, 2018, 12:01 PM
Registered User
Quote:
Originally Posted by rotagen
I think the battery weight at 1800mah would be the issue for hand tossing.

Just a little more info from my experience. I looked at my Kungfu and I am using a 6x5 slow fly prop it looks like. And that is on that low KV (1300?) heavy- ish motor the plan first mentioned. I found that combo to be better suited to 4S, I think the KV was around 1300? For a 6 inch prop and 3S you want around 2000KV. No big deal flies great with a 4S 850maH.

In my experience it really is a stressfull thing to hand launch a wing that size with an overweight battery, but I haven't tried it on the Kungfu, I've only tried 3S 1000maH and 4S 850, about the same weights. The main issue is keeping enough altitude to miss the ground and keeping the wing level since the stall speed is certainly increased with the added weight. But who knows, the kungfu is such a nice flier. Now with a larger prop and lower KV, you might get away with it, much more authority at low speed. My guess is if you just let the thing fly, you'd have to be at full throttle, and the acceleration below stall speed... scary. But I have some super fun little 2S warbirds that weigh around 5-6 ounces, it's really fun to just release them with your fingers and they're fine.

BTW: I always grab the left wing and discus throw my pusher planes. I know many people throw them normally..... DON'T risk a trip to the hospital.
missed the over sized battery yes the weight is going to make things harder, the heavier a plane is made the faster it needs to go to stay flying..
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Apr 15, 2018, 11:24 AM
Disaster magnet
The 1800Mah 3s that I own weighs 152 grams. I also have a 740Mah 2s that weighs <30 grams. Would the 2s work better? Maybe with a larger prop?
Apr 15, 2018, 10:36 PM
Scratch building addict
rotagen's Avatar
I would say that it would fly but not with much authority. 2S at 2200kv motor gives about a 6-8 inch prop I think. But it might be a good easy setup for the maiden until you get a 3S around 1000mah. I say go for it but you'll have to move the battery way forward to get CG right.
Apr 16, 2018, 04:46 AM
Reap the wild wind
headlessagain's Avatar
I have a slightly larger Funbat which will take anything from a 800-2200 mAh 3s lipo. Easy to get away but vertical is blunted with the larger pack.
Perhaps "mclarkson" could chime in re lipo size as I'm pretty sure he's built both models
Andy
Apr 16, 2018, 08:42 AM
flyin' fool
goldguy's Avatar
The designer recommends 800 to 1000 3S with a flying weight of around 300 grams.

There must be a reason!!

LIGHT IS MIGHT.
Last edited by goldguy; Apr 16, 2018 at 08:47 AM.
Apr 16, 2018, 10:01 AM
Scratch building addict
rotagen's Avatar
I agree goldguy. From my experience (learn by screwing up), lighter is always better, and with the kungfu the trade-off between power and lightness seems perfect as-listed.

Also this size makes proper CG easy to obtain with the fuselage design.

Get a ton of different size batteries like I do, and store them in baggies at proper voltage in a beer fridge (justifying my addiction).

hint....thank me later.....

http://www.valuehobby.com/power-syst...0mah-3s-t.html

I found both the 3S 1000maH and the 4S 850maH (nearly identical weight and size) work well. I switched to 4S because the KV on the motor I followed from the initial plan was low - 1250KV I think it was.
Last edited by rotagen; Apr 16, 2018 at 10:07 AM.
Apr 16, 2018, 10:07 AM
Registered User
Successfull maiden of sorts... it was really windy so its hard to tell.

First launch ended up nose up and felt like had hardly any control, moved the battery back and it was much better. but the wind made it hard to do proper controlled turns. I think i may be lacking in control throw. Might change for stronger servos, the ones im using seem pretty flimsy.

Need to redo the control rods. BBQ with piano wire isnt ideal, the rod gets in the way of getting more throw.

2300kv on 3s with a 6x5 prop seems to work fine.
Apr 16, 2018, 10:26 AM
Scratch building addict
rotagen's Avatar
Cool, I pretty much always use 0.047 music wire for my control rods and those dubro mini E/Z connectors on the control horn, which I always run out of, The 047 is the largest size the minis take. I think I got my music wire from Hobbylinc.
Apr 16, 2018, 11:33 AM
Registered User
Quote:
Originally Posted by rotagen
Cool, I pretty much always use 0.047 music wire for my control rods and those dubro mini E/Z connectors on the control horn, which I always run out of, The 047 is the largest size the minis take. I think I got my music wire from Hobbylinc.
I can get music wire locally. Just used what I had on hand. Just looked at the first page pics. I'm not close enough to the hinge with my control horns plus they need to be taller. And use a longer servo arm.

Gonna change out for a better servo. The ones i used were from my mini arrow wing and was never that impressed. The throw on them seemed low aswell
Apr 16, 2018, 11:37 AM
Scratch building addict
rotagen's Avatar
I used trusty old cheapo hxt500s I think and they work well, loops etc no problem. I think most people use 9gm servos? I haven't found anything smaller than those hxt that work worth a darn...and I've tried...turnigy 4gm and 3 other brands were all pretty crummy....one of my ongoing searches.

The tower pro 5gm servos that look like the hxts I have had problems with so they got on my sh*t list.

Anyways, its a great plane, just throwing stuff out there.
Apr 16, 2018, 10:52 PM
flyin' fool
goldguy's Avatar
It's all about a low wing loading!! The difference between light and heavy is.............

*** Overall better performance in all aspects of flight
*** Better input control
*** Improved aerobatics
*** More efficient
*** Longer flights
*** Less crash damage
*** And, most importantly ................ way more FUN

All it takes is an ounce or two to ruin a great design, once you've experience light you'll never go back to porky.
Last edited by goldguy; Apr 16, 2018 at 10:58 PM.
Apr 17, 2018, 03:38 AM
Registered User
Quote:
Originally Posted by goldguy
It's all about a low wing loading!! The difference between light and heavy is.............

*** Overall better performance in all aspects of flight
*** Better input control
*** Improved aerobatics
*** More efficient
*** Longer flights
*** Less crash damage
*** And, most importantly ................ way more FUN

All it takes is an ounce or two to ruin a great design, once you've experience light you'll never go back to porky.
Yep i built a yak 55 hevy. By heavy I mean almost 250g too heavy. Put a biger motor upfront. Sure it flew but it was not well behaved in slow flight. It did however handle wind fairly well. But it broke on almost every hard landing.

Just weiged my Kung-fu. 270g auw. That's with an 1806 2200kv motor upfront and a simonk 30a speed controller, 1000mah 3s battery. 2 9g servos

I recycled the power pod from my flitetest mini arrow so there's extra weight there.

I flew this in 15mph wind. It wasn't fun but it did fly.

No carbon spar. Fibre tape on both sides of the bottom foam and top kfm dowbler. Tape is stretched to keep it under tension. It's pretty stiff might even be stiffer than a single carbon spar.

Not sure if it makes a difference for flight but I decided to round the leading edge of the v-tail. Really liked how it looked so did the top aswell. Going to do the elevons and the wing ends aswell makes it look just that little it less hacked together.
Apr 17, 2018, 08:34 AM
Disaster magnet
Quote:
Originally Posted by rotagen
I agree goldguy. From my experience (learn by screwing up), lighter is always better, and with the kungfu the trade-off between power and lightness seems perfect as-listed.

Also this size makes proper CG easy to obtain with the fuselage design.

Get a ton of different size batteries like I do, and store them in baggies at proper voltage in a beer fridge (justifying my addiction).

hint....thank me later.....

http://www.valuehobby.com/power-syst...0mah-3s-t.html

I found both the 3S 1000maH and the 4S 850maH (nearly identical weight and size) work well. I switched to 4S because the KV on the motor I followed from the initial plan was low - 1250KV I think it was.

Wow, that is a really cheap lipo.
Apr 17, 2018, 10:14 AM
Scratch building addict
rotagen's Avatar
bazsound that is a nice-looking kungfu.

Thanks for those pics, Now I feel better about my next project, a second-try at a wing with the zanonia seed shape. I call it the Manta. Because of the shape (circular/elliptical in the front) I couldn't figure out how to put in a carbon spar so I decided I will leave it out, and do something similar to you with extreme tape or just a KF layer to stiffen things.... epoxy itself makes a pretty good stiffening agent.

I can't agree more, Lightness matters more than anything, there's no replacement if you want an enjoyable plane.

I learned that the hard way early on, and then forgot later and made some crappy flying planes, now I have to keep reminding myself.
Apr 17, 2018, 10:51 AM
flyin' fool
goldguy's Avatar
Ever pick up a bird? Amazing how light they are. They have hollow bones for a reason.

The reason geese poop so much is that if they didn't the extra weight causes them issues with taking off.


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