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Katana Mini Snap

Old 06-04-2006, 09:28 PM
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EZ Money
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Default Katana Mini Snap

I flew my Katana Mini for the first time this weekend. Everything is set up per the book but it wants to climb with power so I trimmed it out and moved the CG forward.

The biggest problem is that as soon as I cut the power for landing it snaps. I have a lot of airplanes including a 25% Cap 232 and have never seen an airplane so snappy.

Right now the thing is unflyable.

Anyone have experience with this and is there a recommend fix?

Thanks,
Old 06-04-2006, 09:39 PM
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Ryguy
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Default RE: Katana Mini Snap

That's really weird. I have a Katana and haven't had any problems with anything like that. I'd recommending posting on RCgroups, there's a huge thread on the Katana there, and a bunch of guys who would be glad to help.
Old 06-05-2006, 12:14 AM
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nitro wing
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Default RE: Katana Mini Snap

Check your wing and surfaces for warpage and alignment,also check lateral balance.
Old 06-05-2006, 07:31 AM
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Default RE: Katana Mini Snap

try using a lot of expo. this will soften up the controls so it will not snap as much.
Old 06-05-2006, 08:59 AM
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Default RE: Katana Mini Snap

Check the lateral balance as suggested. Also, add a ton of expo to the elevator. The elevator is very poertful and can cause the plane to snap if you apply alot of up when near the stall speed.
Old 06-06-2006, 03:50 PM
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lwatson
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Default RE: Katana Mini Snap

Mine is very stable at low speeds. I land with just a small amount of throttle. I suspect your engine incidence is wrong. If it climbs with power it might have up incidence. I set my CG so it flies hands off upside down. I fly with slight 1/16" spoilrons just to avoid wing rock in harriers.

First get the incidence correct. Test this by flying at mid power and trim it out, then fly at high power. The plane should track the same.

Next test CG, the inverted test is good, but you can also fly it high with mid power, then point the nose down to 45 degrees as the plane accelerates it should stay at 45 degrees. If it flattens out, you are nose heavy. If it dives, you are tail heavy.

Have faith, this is a good flying plane. stick with it.
Old 06-21-2006, 06:14 AM
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jvdii
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Default RE: Katana Mini Snap

I had the snap problems as well. It is very snappy at slow speeds. I have tried it both nose heavy and tail heavy, with the same result. I like the idea reducing elevator throw. This sounds like the right solution. Along with reducing the elevator throw, I have also moved the CG to a mid point. Hopefully next flight will be better.

I also have a question about my motor / speed controller setup. I have an old Phoenix 45 and an eflite 480. The battery is an Apex 2200. The prop is an APC slow fly 12x6. When I first fired it up with auto cal throttle the motor squealed horribly around 3/4 throttle. I changed it to fixed throttle and added a throttle curve to keep out of that higher range. I have tried many combinations to get up in the higher range, but it always squeals. Reducing prop size and removing the prop reduce the problem. I have removed current protection with no change. Is this a common situation? I have not had this problem with smaller setups.

Finally, is the comment about CG and 45 deg down-line backwards? I thought tail heavy will flatten out and nose heavy will dive.

Thanks for the help.
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Old 06-21-2006, 08:53 AM
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Default RE: Katana Mini Snap

The way to set the CG is so that it will fly hands off right side up and inverted.
Old 06-21-2006, 09:12 AM
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Default RE: Katana Mini Snap

The way to set the CG is so that it will fly hands off right side up and inverted.
I agree.
Old 06-21-2006, 09:42 AM
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EZ Money
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Default RE: Katana Mini Snap

I reduced the rates on the elevator from 65% on low rate to 40% and that cured the problem. However on the first flight the tabs that hold the hatch pulled out and the hatch and canopy flew off. I landed it perfectly and the right gear folded which caused the prop to hit the pavement tearing the motor out of the cage.

So now I have beefed the whole thing up by addiding a lot of 1/16 plywood.

If it breaks again, in the trash it goes.

It's a nice airplane but waaay too flimsy and who ever came up with the two piece landing gear wasn't thinking too well.
Old 06-21-2006, 07:06 PM
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jvdii
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Default RE: Katana Mini Snap

CG:
I had a Foamy Factory Votec that was balanced to fly inverted and upright hands off. It was a very good flyer. I say had because I gave it away to make room for new stuff, and returning a favor. I would like to get the Katana to that point.

Landing Gear:
My Dad warned me of the split gear, so I beefed them up.

I re-setup the Katana this morning before work. I have not had a chance to try it yet. I have a feeling it will be nice.

I bet this happens quite a bit. I have a 30% extra and a couple foamies. I viewed the Katana in the same ranks as the foamies, so I set it up that way. If I set up the 30% Carden heavy on the throws, it would be snappy too.
Old 06-21-2006, 08:49 PM
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Default RE: Katana Mini Snap


ORIGINAL: jvdii

CG:
I had a Foamy Factory Votec that was balanced to fly inverted and upright hands off. It was a very good flyer. I say had because I gave it away to make room for new stuff, and returning a favor. I would like to get the Katana to that point.

Landing Gear:
My Dad warned me of the split gear, so I beefed them up.

I re-setup the Katana this morning before work. I have not had a chance to try it yet. I have a feeling it will be nice.

I bet this happens quite a bit. I have a 30% extra and a couple foamies. I viewed the Katana in the same ranks as the foamies, so I set it up that way. If I set up the 30% Carden heavy on the throws, it would be snappy too.

We use alot of throw, but TONS of expo. But still we do not have the throw set at max. We have about 120 flights on the current demo plane and just now broke the fuse at the LG mount. As you can see by the video we did, our runway is quite rough and most of the time we harrier it in but it always catches the pants and noses the plane over immediately. We have had to re-tighten it numerous times, but never broke anything until now. We have blown the motor out the front of the cowl twice due to a faulty ESC causing vibration and have found that just by reinforcing every glue joint with a bead of thick CA makes it alot stronger. Also, soak the top and bottom balsa pieces of the motor box with thin CA.

Hope this helps.
Old 07-14-2006, 05:17 AM
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clive45
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Default RE: Katana Mini Snap

Have you sealed the hinge gaps. This evedently stops the snap at slow speed. This is covered in detail on RCG
Old 07-14-2006, 09:18 AM
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Ryguy
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Default RE: Katana Mini Snap

About the LG, I strongly recommend the 3dhobbyshop.com aluminum gear. It held up to a crash that ripped out the bottom of the fuselage when the wind switched directions on me in a harrier.

Once you get the KM set up right, it rocks. I fly mine like a foamy, catching it from hovers and poking the thing with the TX antanna while hovering right in my face. Its FUN!
Old 07-14-2006, 04:34 PM
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Default RE: Katana Mini Snap


ORIGINAL: Ryguy

About the LG, I strongly recommend the 3dhobbyshop.com aluminum gear. It held up to a crash that ripped out the bottom of the fuselage when the wind switched directions on me in a harrier.

Once you get the KM set up right, it rocks. I fly mine like a foamy, catching it from hovers and poking the thing with the TX antanna while hovering right in my face. Its FUN!




Working on a 20OZ KM now. No LG small motor Tiny battery and feather servos. Should fly like one of the profile balsa E-Profiles.


www.venomengines.com

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