marktur

Opjose - thanks for the Bobcat file for G3 - very cool.
I just changed my flaperons to Spoilerons after doing about 30 touch and goes with your modeled plane. I was easily able to keep the nose off the ground for the entire length of the runway with very positive control...

Can you tell me how much throw you're setting for the spoilerons? Give me measurements at the root - closest to the fuse so I can make sure I'm measuring from the same position as you are. I'm using the Spektrum Heli version, so I'm using the 2 position switch on the top left for my flap settings: Normal, Spoilers 1, Spoilers 2. I'd like to know how you're mixing your elevator with it. Using the model in G3, it wants to pitch down when I raise them, so I"m assuming you're mixing in up elevator? Also - what is your throw for the elevator? I like the sensitivity of the model, but ailerons are a bit twitchy for my taste....however, I snap-rolled the plane, and WOW! I gotta try that with my real one, but I'm afraid to rip off the tail booms! (I did finally switch to metal screws all around, but still...lots of stress doing a snapper!

I wonder if anyone has a model configured for the HET F20 EDF? I'm about to finish one...

Thanks!

PS. Didn't fly - looked like rain out west by the field and I was lazy...

opjose

Actually I think you have it backwards...

When it wants to "pitch down" the spoilerons are OFF...

The plane wants to pitch down in normal flight and the trims are used to keep it level at less than WOT.

Turning the knob to the right, and the G3 plane reacts just like mine... it climbs at WOT and maintains level at 60% throttle, just DON'T try to fly it inverted this way!


In other words when you turn the knob to the right the spoilerons "lift" causing the plane to pitch up.

I had my real plane set up the same way so I could trim it in flight and find the best setting.

Once I did I landed it, looked at the deflection and set my "spoilerons"/flap switch to do exactly the same thing.

Now I don't fly it with the knob enabled as it's too easy to forget...


I have the control surfaces set in G3 as per my plane. Mine really does roll that fast!

My tail booms and wings are all permanently epoxied in.


I'll measure the throws later.

PhilLin

Hi, Marktur!

I posted earlier re my KeeCatEDF conversion (www.rcgroups.com/forums/showthread.php?t=722722). The KeeCat is slightly bigger than the Nitro 'Cat. I have a TF4000 120mm fan on it (had it for a CenuryJet BAE Hawks), but my simple mounting design can be easily adapted for the Nitro 'Cat. I'm not familair with the HET F-20 Fan. What mm diameter is it? My TF4000 currently driven by a Neu 1912-1.5Y gives max-static-thrust about 8 lbs of thrust on an all-up-weight of 10lbs; & can give 10.3 lbs with a same size/wt Neu 1912-1Y. So vertical performance is quite lively. Jim Phelps did another conversion where he just bolted an HW730 fan onto the glo engine beams mounted upside down on the stock glo engine fire-wall. His scheme might be more suited if you want to use your nitro-cat as test bed for HET fan; i.e. if it has around 7 to 8lbs static thrust.

Cheers,

Phil

opjose

Hitting the flap switch on my real plane raises the "spoilerons" exactly 1/4"

In the G3 model the spoilerons are raised a bit higher than what I have on my plane.

On my real plane I also have the ailerons raised 1/8" from level with the wing, as measured closest to the fuselage.

I did this after playing with the spoileron settings while the plane was in the air. My intent was to get it to fly level, hands off. That 1/8" helped a great deal with this.

So in effect my real spoileron setting is 3/8" up for both ailerons.


On my real plane using my JR radio, when I engage the spoilerons I add down elevator of approximately 1/8-1/4"

No. The spoilerons ALONE are producing the pitch up effect. Don't thing of the Bobcat like a standard plane. Think of it more like a delta wing.

Up ailerons ( really flaps in this case not spoilerons ) causes the nose to pitch UP, the opposite of what would happen in a normal plane.

I actually have to add a bit of DOWN elevator both in G3 and my real plane to prevent it from going really nose high when the spoilerons are engaged.

On my real plane it measures at 1" Up and 1" down.

I have my aileron throws at 100% travel which gives me about the same deflection as in the G3 model.

The real plane rolls VERY fast at any speed.

I use about 50% Expo on the high rates and 35% Expo on the low rates with the rates set to 100 & 60% respective servo travel.

Yup that's what mine does. Though I never snap roll it at WOT.

I epoxied the booms and stab in place and I installed metal screws and washers, etc. all around.

---

The one thing the model I sent you doesn't do like the real deal, is the "wallowing" the plane does as it approaches stall.

I was still playing with the settings to get the same observed characteristics so I don't consider that a "final" version... just something that would let you see beforehand how the real plane will handle.

marktur

OK guys, I flew it this morning with the new pipe, 30% Cool Power Heli fuel, APC 11x7 prop. All I can say is WOW! It tached at around 14,400 on the ground, and I'm sure it was another 1000 or so better in the sky. It flies the way I wanted it to now! Everyone says it's moving SIGNIFICANTLY faster, although my buddy with a little Electric jet was still faster...we were estimating him at about 110-120 and mine in the 90 mph range, but hard to tell without a radar gun...

The vertical was unreal!

DUB JETT IS THE MAN! That was the best bolt-on upgrade I've had in a while! I don't even care about trying the Weston pipe when it arrives (but I will PS. The plane came home CLEAN!!!!!! A little bit of oil on the horizontal stab...that's it.

I'm really glad I didn't add the extra weight of a bigger motor, as I'm hearing and seeing (in G3) the differences between mine and OPJose's plane. He's at least 10 oz heavier than me, and it seems like it's much more throttle/pitch sensitive than mine is. My ailerons are smooth with the wing in normal flight, and my elevator is only a MM or so up to sustain level flight at any speed.

I did mix in the spoilerons, and took most of the up elevator mixing out, but next flight I'll try it with no mixing at all and see if that stops it from ballooning. Spoilerons were the RIGHT answer for sure, OPJose - thanks for the help for sure!

I want to weigh my plane and then we'll be able to tell if this is why I'm not having pitchy issues...

opjose

Yup you are running more efficiently than I am with my .76 so our speeds are somewhat comparable.... but I have more weight giving you better ( or equal ) verticals.

It's a blast to fly isn't it?

Quite impressive for a non-turbine plane.

I have my battery pack stuffed in the nose. When I adjust the G3 model the same way the G3 plane becomes much more pitch sensitive even though the C.G. is about the same.

OldRookie

My Feedback: (13)

I was trying to figure which engine would be faster in the Bobcat.
I have a YS 45, and would use a quiet pipe on it.
The other set -up would be the OS 55AX, on some type of pipe.
I have only run the YS 45 on the stock muffler, so wouldn't know their potential. I think I would like to set up the YS 45 for a pretty good up line. It shouldn't be too much trouble to re tune the pipe for a smaller diameter bigger pitch prop for when you really want to get top speed.
Either way I have to throw some $$$$ at it. I keep telling myself, it is only a hobby.

Greg

timevac

Yes I was suprised at how much fuel i am using as well.I am runnig the stock tank (12oz i think).
I do fly at full thottle for the whole flight,even when in a vertical dive!! That might have somthing to do with it.
I was getting about 9 minutes without the pipe on it.

timevac

Marktur How was your fuel consumption on the jett pipe??

littlepiston

My Feedback: (12)

well i flew my bobcat a few more time,, I CANT GET IT TO SLOW down! hehe Were is the build thead that has the mods for adding flaps?? and whqat can i expect when i apply flaps

The plane flys fast and im only at above 1/2 thottle i took it full speed a few time. its a little to fast for now, i need more flight time.

hapyjac2

My Feedback: (927)

If you want to add flaps, and if you want to be AMA legal, any turbine powered aircraft must have brakes too!

Check out my BobCat Conversion link at;

www.southfloridajettogether.com

littlepiston

My Feedback: (12)

i have brakes allready from Tam, it need flaps also to be AMA legal?

marktur

Littlepiston - setup SPOILERONS. I used them very effectively this weekend, and it cuts out some of the "floaty" lift when in ground effect, and definitely slows the plane down visibly in the air. I don't know if that counts as "flaps" for turbines, but it sure does the trick.

ira d

The AMA does not require flaps for turbines

marktur

Anyone know if I can fly my Bobcat at the Cape Coral Jet Rally?

larry11

My Feedback: (6)

What exactly is the difference between the retract ready, and non-retract ready? Can you use fixed gear temporarally with the retract version?

The reason I ask is I want to adventually add retracts semi hassle free.

marktur

Hi Larry,
I would suggest simply getting the retracts...it makes a wonderful difference. Go with Spring-airs - around $150-160. This is an investment like a radio or motor, which can go from plane to plane over the years...

I'm not sure if you'll be able to mount regular gear,. because of the gap in the hardwoord that allows you to drop in the retracts.

Also, the retract-ready version seems to have a bit thicker of a wing and L.E., which gives you better characteristics for slow flight (yes, it will fly "slow", too).

Hope that helps!
Mark

opjose

The retract ready version does allow for the installation of the fixed gear, but the process is not really reversable as designed.

In other words what you install is what you'll be flying with...

The attachment block for the fixed gear gets epoxied in the wheel opening that would be used by the retracts.

I'd imagine that you could rig up something, but it would require some machinations...

---

Meanwhile my Bobcat .25 is coming along too...

I hope to post pics and maybe some build tips when I am done.

marktur

If you epoxy the gear blocks in, then you'll have to do some real surgery if you ever want to change to retracts...my $0.02...


Mark

PS. Jets are not supposed to have fixed gear!

marktur

Jose,

Who is selling a .25 size? (Or are you scratch building?)
What motor are you going to use?

Very interesting!

Mark

marktur

Saw it on Nitro Models...cool.

opjose

Yup I'm going EP on the .25 though it can use either a glow or electric motor.

marktur

Are you putting in retracts (say yes, dammit!)

opjose

No sorry... too much effort on such a small plane and I'm already worried about the total weight.

I'm far more concerned about getting it properly powered as an EP.

I've made the motor mounting box removable so I can always go back to glow or another engine mount.


If I like it, I may get another then try retracts on it...

tamir_250

hey everybody !
which engine will be better for the FALCON 120, the AX120 or THE FX 160 ?
regurds.